WO2011122357A1 - Image pickup optical system and optical adjustment method - Google Patents

Image pickup optical system and optical adjustment method Download PDF

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Publication number
WO2011122357A1
WO2011122357A1 PCT/JP2011/056331 JP2011056331W WO2011122357A1 WO 2011122357 A1 WO2011122357 A1 WO 2011122357A1 JP 2011056331 W JP2011056331 W JP 2011056331W WO 2011122357 A1 WO2011122357 A1 WO 2011122357A1
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WO
WIPO (PCT)
Prior art keywords
lens
lens group
optical system
imaging optical
positive
Prior art date
Application number
PCT/JP2011/056331
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French (fr)
Japanese (ja)
Inventor
治行 中野
昇 滝
宏明 田中
慶二 松坂
Original Assignee
コニカミノルタオプト株式会社
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Application filed by コニカミノルタオプト株式会社 filed Critical コニカミノルタオプト株式会社
Priority to CN2011800269188A priority Critical patent/CN103201665A/en
Publication of WO2011122357A1 publication Critical patent/WO2011122357A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
    • G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
    • G02B13/002—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface
    • G02B13/0045—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface having five or more lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B9/00—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -
    • G02B9/12—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having three components only

Definitions

  • the present invention relates to an imaging optical system that forms an image of a subject on an imaging surface of a solid-state imaging device, and an optical adjustment method for the imaging optical system.
  • imaging devices using solid-state imaging devices such as CCD (Charge Coupled Device) type image sensors and CMOS (Complementary Metal-Oxide Semiconductor) vertical type image sensors have become mobile phones, PDAs (Personal Digital Assistants), etc.
  • an image pickup optical system including, for example, three to five lenses is used due to a demand for high performance and the like.
  • the imaging optical system is an optical system that forms an image of a subject on the imaging surface of the solid-state imaging device.
  • Such an imaging optical system has a demand for autofocusing when mounted on a camera-equipped mobile phone, for example.
  • an imaging optical system is single-focused because the number of lenses is relatively small, and as a focus adjustment method for auto-focusing, an entire extension system that moves all the lenses constituting the imaging optical system Is often adopted.
  • an inner focus system that moves some of the internal lenses as shown in Patent Document 1 is advantageous.
  • the imaging optical system that employs the inner focus method has a mechanism that moves in the optical axis direction for focus adjustment. For this reason, in the inner focus method, the number of mechanical parts increases, and the center position of the lens tends to be decentered in a direction perpendicular to the optical axis.
  • An imaging optical system configured to satisfy the demands for miniaturization and high performance is susceptible to an adverse effect (for example, one-sided blur) due to eccentricity generated during manufacturing.
  • an imaging optical system is a single-focus imaging optical system that forms an image of a subject on an imaging surface of a solid-state imaging device, and in order from the object side to the image side, A first lens group having at least two lenses including a positive lens disposed on the side and having a positive refractive power as a whole, and a second lens group having at least one lens as a whole and having a positive refractive power as a whole A third lens group including at least one lens, wherein the first lens group and the third lens group are fixed with respect to the imaging surface, and the second lens group is used for focus adjustment. It is provided so as to be movable in the optical axis direction and satisfies the following conditional expression. 0.1 ⁇ f1 / fg2 ⁇ 2 However, f1 is the focal length of the positive lens closest to the object, and fg2 is the focal length of the second lens group.
  • the imaging optical system of this configuration is a configuration in which a second lens group disposed between the first lens group and the third lens group is provided so as to be movable in the optical axis direction, and adopts a so-called inner focus method. Yes. For this reason, it is easy to reduce the size and height of the imaging optical system as compared with the case where the entire (all group) feeding system is adopted.
  • the focal length of the positive lens arranged on the most object side and the focal length of the movable second lens group are configured to satisfy a predetermined conditional expression. For this reason, when the imaging optical system is assembled, the decentering of the entire optical system can be easily adjusted by moving the positive lens arranged on the most object side in the direction perpendicular to the optical axis, and the imaging optical system can be downsized. It can be maintained.
  • the first lens group is configured by at least two lenses including a positive lens on the most object side.
  • the first lens group for example, by including at least one negative lens in the first lens group, it is possible to effectively correct the spherical aberration and the axial chromatic aberration. It is easy to improve the optical performance.
  • the imaging optical system of this structure satisfy
  • fg2 is the focal length of the second lens group
  • f is the focal length of the entire imaging optical system.
  • the imaging optical system of this structure satisfy
  • fg1 is the focal length of the first lens group
  • f is the focal length of the entire imaging optical system.
  • the imaging optical system having the above configuration includes a first holding member that holds the first lens group, a second holding member that holds the second lens group, and a third holding that holds the third lens group.
  • the lens holding space of the first holding member is preferably formed such that the diameter in the direction perpendicular to the optical axis is larger than the diameter of the positive lens arranged on the most object side. .
  • the imaging optical system when the imaging optical system is assembled, it is possible to adjust the eccentricity of the entire optical system by moving only the positive lens arranged on the most object side, and the eccentricity can be adjusted efficiently.
  • the positive lens arranged on the most object side is moved in the direction perpendicular to the optical axis to adjust the eccentricity, and further, the first lens group is moved in the optical axis direction. It is also possible to correct field curvature.
  • the first holding member further includes a space portion for arranging an adjustment jig around the lens holding space.
  • a space portion for arranging an adjustment jig around the lens holding space.
  • the first holding member further includes an adhesive filling portion for bonding and fixing a side surface of the positive lens disposed on the most object side, and the space portion includes the adhesive filling portion.
  • the space portion and the adhesive filling portion may be arranged in a circumferential direction of the first holding member so as to be sandwiched.
  • the third lens group includes a negative lens. According to this configuration, the total length of the imaging optical system can be reduced (lower profile) by a so-called telephoto type lens configuration.
  • the optical adjustment method of the present invention is composed of at least two lenses including a positive lens arranged on the most object side in order from the object side to the image side.
  • the third lens group is an optical adjustment method of a single-focus imaging optical system that is fixed with respect to the imaging surface, and the second lens group is provided so as to be movable in the optical axis direction for focus adjustment. It is characterized by comprising an alignment process for adjusting the decentration of the entire optical system by moving the positive lens on the object side in the direction perpendicular to the optical axis.
  • the imaging optical system preferably satisfies the following conditional expression. 0.1 ⁇ f1 / fg2 ⁇ 2
  • f1 is the focal length of the positive lens closest to the object
  • fg2 is the focal length of the second lens group.
  • the optical adjustment method having the above-described configuration further includes an inclination adjustment step of adjusting the inclination of the second lens group, and the alignment step is performed after the inclination adjustment step.
  • the inclination of the second lens group is removed, and the remaining parallel eccentricity (which causes a one-sided blur) is corrected. For this reason, good optical performance can be easily obtained, and optical adjustment can be performed efficiently.
  • position adjustment for moving the first lens group in the optical axis direction may be performed after the alignment step. According to this configuration, both the one-sided blur and the curvature of field can be corrected. Further, in this configuration, not only the positive lens on the most object side but also all the first lens units are moved in the optical axis direction, and there is an advantage that adjustment work is easy.
  • the alignment step may be performed using a solid-state imaging device prepared exclusively for optical adjustment, or may be performed using a solid-state imaging device incorporated as a product. Also good.
  • an imaging optical system having a stable quality can be obtained, and the former method is suitable for, for example, a trader who sells an imaging optical system. Further, according to the latter method, it is possible to obtain an imaging device with good optical characteristics (a device in which a solid-state imaging device is incorporated in an imaging optical system), and the latter method is suitable for a trader who sells imaging devices, for example. is there.
  • the first lens group includes a lens that is different from a positive lens disposed on the most object side and has a first position reference mark, and the third lens.
  • the group includes a lens having a second position reference mark, and when the positive lens arranged on the most object side is observed from the direction along the optical axis before being included in the first lens group,
  • the relative position adjustment of the first lens group and the third lens group may be performed so that the first position reference mark and the second position reference mark coincide with each other.
  • the imaging optical system satisfies the following conditional expression. 0.1 ⁇ fg2 / f ⁇ 2
  • fg2 is the focal length of the second lens group
  • f is the focal length of the entire imaging optical system.
  • an imaging optical system that can be reduced in size and height and can be easily aligned when the imaging optical system is assembled.
  • optical adjustment of the imaging optical system can be performed efficiently. Therefore, according to the present invention, it is possible to provide an image pickup optical system and an image pickup apparatus having good optical characteristics that can be reduced in size and height and suppress one-side blur.
  • Schematic perspective view showing a configuration of an optical unit including the imaging optical system of the present embodiment Schematic exploded perspective view showing the configuration of an optical unit including the imaging optical system of the present embodiment
  • Schematic sectional view of an optical unit including the imaging optical system of the present embodiment The flowchart which shows the assembly procedure of the imaging optical system of this embodiment Schematic sectional view showing a state (first state) during assembly of the imaging optical system of the present embodiment Schematic sectional view showing a state (second state) during assembly of the imaging optical system of the present embodiment
  • FIG. 5 is a schematic cross-sectional view showing a state during the assembly of the imaging optical system of the present embodiment, and is a diagram for explaining a first lens alignment process;
  • the top view of the 1st lens holder of this embodiment when it sees from the top, and the figure showing the state where the 1st lens was inserted in the holder Configuration diagram of the imaging optical system of Example 1 Configuration diagram of the imaging optical system of Example 2 Configuration diagram of the imaging optical system of Example 3 Configuration diagram of the imaging optical system of Example 4 Configuration diagram of image pickup optical system of Embodiment 5 Configuration diagram of the imaging optical system of Example 6 Configuration diagram of the imaging optical system of Example 7 Configuration diagram of imaging optical system of embodiment 8 Configuration diagram of image pickup optical system of Embodiment 9 Configuration diagram of imaging optical system of Example 10 Aberration diagram of Example 1 at infinity object distance Aberration diagram of Example 2 at object distance at infinity Aberration diagram of Example 3 at infinity object distance Aberration diagram of Example 4 at infinity object distance Aberration diagram of Example 5 at infinity
  • FIG. 1 is a schematic perspective view illustrating a configuration of an optical unit including an imaging optical system according to the present embodiment.
  • FIG. 2 is a schematic exploded perspective view showing a configuration of an optical unit including the imaging optical system of the present embodiment.
  • FIG. 3 is a schematic cross-sectional view of an optical unit including the imaging optical system of the present embodiment.
  • the optical unit 10 including the imaging optical system 1 (see FIGS. 1 and 3) of the present embodiment is roughly divided into a first group unit G1, a second group unit G2, and a third group unit G3.
  • the actuator unit A1 is provided.
  • the first unit G1 in order from the object side to the image side, includes a first light shielding plate 11 made of a donut-shaped disk component, a first lens L1, and a second light shielding plate 12 made of a donut-shaped disk component. And the second lens L2, and these are held by the first lens holder (embodiment of the first holding member of the present invention) 13. That is, in the present embodiment, the first lens group LG1 is formed by the first lens L1 and the second lens L2.
  • the first lens holder 13, which is a bottomed plate-shaped member having a substantially disk shape in plan view, has a lens holding space 13a for holding the first lens group LG1 in the thickness direction. In addition, an opening 13 b for allowing light to pass through is formed at the bottom of the first lens holder 13.
  • the first group unit G1 (first lens group LG1) is an imaging surface 70a of a solid-state imaging device 70 (for example, a CCD type image sensor, a CMOS type image sensor, etc .; indicated by a broken line in FIG. 3) attached to the optical unit 10. It is fixed so as not to move.
  • the first lens L1 is a positive lens
  • the second lens is a negative lens
  • the first lens group LG1 including the first lens L1 and the second lens L2 has a positive refractive power as a whole.
  • the first lens group LG1 (the lens group provided in the first group unit G1) has a positive lens (the first lens L1 of the present embodiment) disposed on the most object side, and has a positive refractive power (positive power as a whole). ) May be configured with three or more lenses. In order to effectively correct the spherical aberration and the axial chromatic aberration, it is preferable that the first lens group LG1 includes at least one positive lens and at least one negative lens.
  • a position reference mark M1 is formed at a substantially central portion of the object-side surface of the second lens L2 included in the first lens group LG1, as shown in an enlarged view in FIG. That is, the second lens L2 is a mark lens provided with a position reference mark.
  • the position reference mark M1 is obtained by providing a depression (recess) on the lens surface.
  • Such a position reference mark M1 may be obtained, for example, by cutting the lens surface, or may be obtained by providing a protrusion on a mold for manufacturing the lens.
  • the configuration of the position reference mark M1 is not limited to the configuration of the present embodiment.
  • the position reference mark M1 may be obtained by providing a convex portion on the lens surface, or may be a dot obtained by using an inkjet or the like. There may be.
  • the position reference mark M1 is provided on the object side surface, but may be provided on the image side surface.
  • the position reference mark M1 is preferably formed as small as possible so as not to affect the optical performance of the imaging optical system 1 within a range in which the function as a marker is exhibited.
  • the second group unit G2 includes, in order from the object side to the image side, a third lens L3, a third light-shielding plate 21 made of a donut-shaped disk component, and a fourth lens L4, which are a second lens holder. (Embodiment of the 2nd holding member of this invention) It becomes the structure hold
  • the second lens group LG2 is formed by the third lens L3 and the fourth lens L4.
  • the second lens holder 22 has a cylindrical through space 22a, and the second lens group LG2 is held in the through space 22a.
  • the second group unit G2 (second lens group LG2) can be moved in the optical axis direction (reference numeral AX in FIG. 3 is the optical axis) by an actuator unit A1 described later in detail. That is, the imaging optical system 1 of the present embodiment employs a so-called inner focus method.
  • the second lens group LG2 (lens group provided in the second group unit G2) is configured to have a positive refractive power as a whole.
  • the number of lenses constituting the second lens group LG2 is not limited to the configuration (two) in the present embodiment, and may be one or three or more.
  • the second lens group LG2 is composed of two lenses, for example, the third lens L3 and the fourth lens L4 are both positive lenses, the third lens L3 is a negative lens, and the fourth lens L4 is a positive lens. It's okay.
  • the third group unit G3 includes, in order from the object side to the image side, a fifth lens L5, for example, a filter member 42 made of a parallel plate such as an IR cut filter or an optical low-pass filter, and these are the first frame (holding). Member) 41.
  • the first frame 41 has a space 41a penetrating in the thickness direction so that light can pass in the thickness direction.
  • the third group unit G3 (the third lens group LG3 including the fifth lens L3) is fixed so as not to move with respect to the imaging surface 70a of the solid-state imaging device 70 attached to the optical unit 10, similarly to the first group unit G1. State.
  • the third lens group LG3 is formed only by the fifth lens L5, which is a negative lens.
  • the present invention is not limited to this. That is, the third lens group LG3 may be composed of a plurality of lenses, and may have a positive refractive power or a negative refractive power as a whole. However, it is preferable that the third lens group LG3 includes a negative lens, thereby obtaining a so-called telephoto type configuration and shortening the overall length of the imaging optical system 10 (a reduction in size and height). .
  • a position reference mark M2 is formed at a substantially central portion of the object-side surface of the fifth lens L5 included in the third lens group LG3 as shown in an enlarged view in FIG. That is, the fifth lens L5 is a mark lens provided with a position reference mark.
  • the position reference mark M2 provided on the fifth lens L5 is obtained by providing a recess (concave portion) on the lens surface.
  • the method of forming the position reference mark M2 and the points to be noted are the same as those of the position reference mark M1 provided on the second lens L2.
  • the position reference mark M2 provided on the fifth lens L5 may be changed to another configuration (such as a convex portion or a dot) as in the case of the position reference mark M1 provided on the second lens L2.
  • the actuator unit A1 is a drive mechanism that allows the second group unit G2 (second lens group LG2) to move in the optical axis direction so that the imaging optical system 1 is an inner focus type.
  • This actuator unit A1 is configured using an ultrasonic linear actuator that is referred to as a SIDM (Smooth Impact Drive Mechanism; registered trademark) actuator 31 and is suitable for miniaturization.
  • SIDM Smooth Impact Drive Mechanism; registered trademark
  • the SIDM actuator 31 is bonded and fixed to one end of the SIDM shaft 31a and the SIDM shaft 31a arranged so that the axial direction is parallel to the optical axis direction, and expands and contracts in the axial direction of the SIDM shaft 31a.
  • a weight 31c that is bonded and fixed to the end of the piezoelectric element 31b opposite to the side to which the SIDM shaft 31a is bonded and fixed.
  • a lead wire 32 and a terminal 33 for driving the piezoelectric element 31b are attached to the SIDM actuator 31 by soldering.
  • a drive signal is given to the piezoelectric element 31b via the terminal 33 and the lead wire 32.
  • the piezoelectric element 31b expands and contracts, and the SIDM shaft 31a vibrates in the axial direction due to the expansion and contraction.
  • the second lens holder 22 that is frictionally engaged with the SIDM shaft 31a (this engagement is realized by the leaf spring 23) is moved in the target direction (FIG. 3). (Upward direction or downward direction).
  • the SIDM actuator 31 can move the second lens group LG2 in the optical axis direction.
  • the weight 31c is provided for the purpose of generating displacement due to expansion and contraction of the piezoelectric element 31b only on the side of the SIDM shaft 31a.
  • the single focus / inner focus type imaging of the present embodiment is performed.
  • the optical system 1 optical unit 10) is obtained. Details of the assembly of the imaging optical system 1 (optical unit 10) will be described later.
  • the five lenses L1 to L5 constituting the imaging optical system 1 are all made of a plastic material.
  • these lenses L1 to L5 may be made of glass.
  • the lenses are made of plastic. It is made of material.
  • the lens constituting the imaging optical system 1 is formed of a plastic material. Since the plastic material has a large refractive index change at the time of temperature change, if all the lenses are made of plastic lenses as in this embodiment, the image point position of the imaging optical system 1 fluctuates when the ambient temperature changes. It will have a problem of end. Recently, however, it has been found that mixing inorganic fine particles in a plastic material can reduce the effect of temperature changes on the plastic material.
  • a plastic material with extremely low temperature dependency of the refractive index can be obtained.
  • fine particles of niobium oxide (Nb 2 O 5 ) in an acrylic resin a change in refractive index due to a temperature change can be reduced.
  • the temperature of the imaging optical system 1 is obtained by using a plastic material in which such inorganic particles are dispersed in a positive lens (for example, the first lens L1) having a relatively large refractive power or all the lenses. It is possible to suppress the image point position fluctuation at the time of change to be small.
  • the imaging optical system 1 is comprised so that the following conditional expression (1) may be satisfy
  • fg2 is the focal length of the second lens group LG2
  • f is the focal length of the entire imaging optical system 1.
  • the imaging optical system 1 is configured to satisfy the following conditional expression (2). 0.1 ⁇ f1 / fg2 ⁇ 2 (2)
  • f1 is the focal length of the first lens L1 (the most object side positive lens)
  • fg2 is the focal length of the second lens group LG2.
  • the reason why the conditional expressions (1) and (2) are satisfied in this way is to correct the eccentricity (deviation in the direction perpendicular to the optical axis AX) generated in the lenses L1 to L5 constituting the imaging optical system 1.
  • This is a device for facilitating the adjustment work for obtaining (obtaining good optical characteristics). Details of this will be described in a method for assembling the imaging optical system 1 (optical unit 10) described below.
  • FIG. 4 is a flowchart showing an assembling procedure of the imaging optical system of the present embodiment.
  • assembly of the imaging optical system 1 will be described with reference to FIG.
  • the first group unit G1 is assembled (step S1). Specifically, the second lens L2 and the second light shielding plate 12 are incorporated in the first lens holder 13 in this order. At this time, the second lens L2 is bonded and fixed to the first lens holder 13. At this stage, the first lens L1 and the first light shielding plate 11 are not incorporated into the first lens holder 13.
  • the second group unit G2 is assembled (step S2). Specifically, the fourth lens L4, the third light shielding plate 21, and the third lens L3 are incorporated in the second lens holder 22 in this order. At this time, by applying an adhesive 80 between the third lens L3 and the second lens holder 22, the fourth lens L4, the third light-shielding plate 21, and the third lens L3 are collectively put into the second lens L3. The lens holder 22 is fixed.
  • the third group unit G3 is assembled (step S3).
  • the fifth lens L5 and the filter member 42 are incorporated in the first frame 41.
  • the fifth lens L5 and the filter member 42 are assembled into the first frame 41 from different directions (for example, from the top and bottom in FIG. 3). These incorporated members are each bonded and fixed to the first frame 41 with an adhesive 80.
  • step S4 the assembly of the actuator unit A1 is performed (step S4). Specifically, one end of the SIDM shaft 31a and one end of the piezoelectric element 31b are bonded and fixed, and the other end of the piezoelectric element 31b and one end of the weight 31c are bonded and thereby the SIDM actuator 31 is formed. One end of a lead wire 32 is soldered to each of a pair of electrodes provided on the piezoelectric element 31 b, and a terminal 33 is soldered to the other end of each lead wire 32.
  • steps S1 to S4 are not limited to the order shown here, and may be performed in a different order, or steps S1 to S4 may be performed simultaneously in parallel.
  • the actuator unit A1 is attached to the third group unit G3 (step S5).
  • the lead wire 32 is wound around the fifth lens L5 mounted on the first frame 41, and the terminal 32 is clipped to a predetermined position (see FIG. 1) of the first frame 41. It is almost fixed by the method.
  • the SIDM actuator 31 is provided in the vicinity of one of the four corners of the first frame 41 provided in a substantially rectangular shape in plan view. However, it is not fixed yet, although it is arranged so that its axial direction is substantially parallel to the optical axis AX.
  • the second group unit G2 is engaged with the actuator unit A1 (step S6).
  • the second group unit G2 is provided in the vicinity of one corner of the second lens holder 22 constituting the second group unit G2 (in the vicinity of the corner substantially above the actuator support portion 41b) and a plate provided in a substantially L shape.
  • the spring member 23 is arranged so as to sandwich the SIDM shaft 32a with the tip of one side.
  • the leaf spring member 23 is attached to a boss 22b (see FIG. 2) provided on the second lens holder 22 so that a substantially L-shaped bending point corresponding to a substantially central portion of the leaf spring member 23 can swing.
  • the tip of the other side of the character is attached so as to abut on the second lens holder 22.
  • the second group unit G2 is engaged with the SIDM shaft 31a with a predetermined frictional force and is movable in the axial direction.
  • the second frame 50 is attached to the first frame 41 (step S7).
  • the second frame 50 having a box shape (however, an opening 50a for allowing light to pass through is provided on the upper surface) is configured to be covered with the actuator unit A1 and the second group unit G2. It is attached to the first frame 41.
  • a snap fit mechanism is provided between the first frame 41 and the second frame 50, and the relative position in the optical axis direction of both is fixed without using an adhesive.
  • the relative position in the direction perpendicular to the optical axis AX is fixed by a positioning pin and a positioning hole engaged therewith.
  • FIG. 5 cross-sectional view shows the state (first state) at the end of step S7.
  • the tip of the SIDM shaft 31a of the actuator unit A1 is fitted in a fitting hole 50b provided on the upper surface of the second frame 50. .
  • the weight 31c is not bonded and fixed.
  • the inclination of the second lens group LG2 (second group unit G2) is adjusted (step S8).
  • the inclination of the second lens group LG2 is adjusted by adjusting the position of the weight 31c in a plane perpendicular to the optical axis AX. More specifically, for example, the imaging surface 70a of the solid-state imaging device 70 is arranged in parallel with the imaging surface 70a (the solid-state imaging device 70 is not attached at this stage, and is assumed to be attached). Inclination is adjusted using, for example, an autocollimator or the like so that the reference surface and the edge surface outside the effective surface of the third lens L3 are parallel to each other. At the stage where this tilt adjustment is performed, the weight 31 c is bonded and fixed to the first frame 41 with the adhesive 80.
  • the first group unit G1 (the first lens L1 is not incorporated) is attached to the second frame 50 (step S9).
  • the position of the first lens holder 13 constituting the first group unit G1 is determined by the position reference mark M1 applied to the second lens L2 and the position reference mark M2 applied to the fifth lens L5.
  • the first lens holder 13 is bonded and fixed to the second frame 50 after adjusting so as to match without shifting in the direction perpendicular to the axis.
  • a state (second state) at the end of step S9 is shown in FIG. 6 (cross-sectional view).
  • the lens position adjustment performed so that the position reference mark M1 and the position reference mark M2 coincide may be performed, for example, while simultaneously observing the two marks M1 and M2 along the optical axis direction. Also, for example, by observing the two position reference marks M1 and M2 separately along the optical axis direction, the positions of the marks M1 and M2 in the observation coordinate system are obtained separately, and based on the obtained coordinate positions. Then, the position of the second lens L5 (the position of the first lens holder 13) may be moved so that the positions of the two coincide.
  • the first lens group LG1, the second lens group LG2, and the third lens group LG3 are mounted on separate mechanical components.
  • a large shift shift in a direction perpendicular to the optical axis AX
  • Such misalignment may make it difficult to obtain good optical characteristics during the final optical adjustment of the imaging optical system 1 (optical adjustment using a solid-state imaging device).
  • lens position adjustment is performed using the position reference marks M1 and M2 so that the second lens L2 and the fifth lens L5 are in the correct relative positions.
  • the imaging optical system 1 is configured to satisfy the conditional expression (1) so that the second lens group LG2 is hardly affected even when the second lens group LG2 is in an eccentric state. -ing 0.1 ⁇ fg2 / f ⁇ 2 (1)
  • fg2 is the focal length of the second lens group LG2
  • f is the focal length of the entire imaging optical system 1.
  • the refractive power of the second lens group LG2 does not become too strong, and the above-described position reference mark caused by the eccentricity of the second lens group LG2
  • the image shift of M2 can be suppressed small.
  • the reason why the lower limit of the conditional expression (1) is satisfied is that the refractive power of the second lens group LG2 is appropriately maintained without becoming too weak, thereby shortening the total length of the imaging optical system 1. This is the purpose.
  • the imaging optical system 1 is more preferably configured to satisfy the following conditional expression (1) ′. 0.5 ⁇ fg2 / f ⁇ 1.5 (1) ′
  • step S9 when step S9 is completed, the first lens L1 (positive lens arranged on the most object side) is fixed to the first lens holder 13 (step S10).
  • the first lens L1 is moved in a direction perpendicular to the optical axis AX before being fixed to the first lens holder 13, and its position is adjusted for optical adjustment (alignment process).
  • FIG. 7 is a schematic cross-sectional view showing a state during the assembly of the imaging optical system of the present embodiment, and is a view for explaining the alignment process of the first lens.
  • the solid-state imaging device 70 Prior to the alignment step, as shown in FIG. 7, the solid-state imaging device 70 is disposed behind the first frame 41.
  • the solid-state imaging device 70 may be an adjustment device prepared for optical adjustment or may be used as a product. When used as a product, the solid-state image sensor 70 may be fixed to the first frame 41 at this stage.
  • FIG. 8 is a schematic plan view of the first lens holder according to the present embodiment as viewed from above.
  • the first lens is inserted into the holder (lens holding space 13a (see FIG. 2)). Show.
  • the first lens L1 inserted into the lens holding space 13a can be held by a jig.
  • the jig is composed of, for example, three claw-shaped members, and is configured such that the claw-shaped member inserted into the space portion 13d sandwiches the first lens L1.
  • the diameter of the lens holding space 13a (size in the direction perpendicular to the optical axis AX) is larger than the diameter of the first lens L1. Therefore, a gap SP is formed in a state where the first lens L1 is inserted into the lens holding space 13a, and the first lens L1 held by the jig is in a direction perpendicular to the optical axis AX of the first lens L1. It is movable.
  • the imaging optical system 1 of the present embodiment employs the inner focus method.
  • the inner focus method is an advantageous method for reducing the height of the imaging optical system 1.
  • the number of mechanical parts is increased, and the center position of the lens is increased.
  • Eccentricity that shifts in a direction perpendicular to the optical axis is likely to occur.
  • An imaging optical system configured to satisfy the demands for miniaturization and high performance is susceptible to adverse effects (eg, one-sided blur and axial coma) caused by eccentricity that occurs during manufacturing. For this reason, when the imaging optical system 1 is assembled, alignment (optical adjustment) is performed in order to correct the influence of eccentricity.
  • the lens position adjustment in step S9 may not be performed depending on circumstances, but is preferably performed to facilitate alignment.
  • the imaging optical system 1 is configured to satisfy the conditional expression (2). 0.1 ⁇ f1 / fg2 ⁇ 2 (2)
  • f1 is the focal length of the first lens L1 (the most object side positive lens)
  • fg2 is the focal length of the second lens group LG2.
  • the focal length of the first lens L1 with respect to the second lens group LG2 is prevented from becoming too short by configuring so as to exceed the lower limit of the conditional expression (2).
  • the focal point of the first lens L1 with respect to the second lens group LG2 is prevented from becoming too long.
  • the amount of movement of the first lens L1 from being too large in order to correct the eccentricity of the second lens group LG2 (for alignment), and the adjustment operation can be performed quickly.
  • the value lower than the upper limit of the conditional expression (2) it is possible to prevent the imaging optical system 1 from becoming large in the lens radial direction (direction perpendicular to the optical axis direction).
  • the imaging optical system 1 is more preferably configured to satisfy the following conditional expression (2) ′. 0.5 ⁇ f1 / fg2 ⁇ 1.8 (2) ′
  • the position adjustment of the first lens L1 in the optical axis direction may be performed together. Thereby, it is possible to improve performance not only for one-sided blur but also for field curvature.
  • the first lens holder 13 that is, the first lens group LG1 is moved in the optical axis direction, so that not only one-side blur but also field curvature You may make it aim at improvement. In this case, in step S9, the first lens holder 13 is not bonded and fixed, and the first lens holder 13 needs to be held by the adjustment jig.
  • the imaging optical system 1 is preferably configured to satisfy the following conditional expression (3), and more preferably configured to satisfy the following conditional expression (3) ′.
  • conditional expression (3) 1.0 ⁇ fg1 / f ⁇ 3.0 (3) 1.3 ⁇ fg1 / f ⁇ 2.5 (3) ′
  • fg1 is the focal length of the first lens group LG1
  • f is the focal length of the entire imaging optical system 1.
  • the focal length of the first lens group LG1 becomes appropriate, and a reduction in height and performance is achieved. Realization is possible. Specifically, since the focal length of the first lens group LG1 can be appropriately maintained by configuring the conditional expression (3) (preferably conditional expression (3) ′) to be lower than the upper limit, imaging is performed. The principal point position of the optical system 1 can be arranged closer to the object side, and the overall length of the imaging optical system 1 can be shortened. Further, by configuring so as to exceed the lower limit of conditional expression (3) (preferably conditional expression (3) ′), the focal length of the first lens group LG1 does not become unnecessarily small, and the first lens group LG1. Higher order spherical aberration and coma can be suppressed.
  • conditional expression (3) preferably conditional expression (3) ′
  • step S10 when step S10 is completed, the first light shielding plate 11 is attached to the first lens L1. Further, the cover 60 is placed on the first frame 41 from above to serve also as a countermeasure for electromagnetic wave leakage (step S11). A snap-fit mechanism is provided between the cover 60 and the first frame 41, and the cover 60 is attached to the first frame 41 without being bonded and fixed.
  • the imaging optical system 1 (optical unit 10) of the present embodiment is obtained.
  • the imaging optical system 1 optical unit 10 of the present embodiment is obtained.
  • a preferred embodiment of the imaging optical system 1 will be described.
  • FIGS. 9 to 18 show the configuration (lens configuration) of the imaging optical system of Examples 1 to 10 (EX1 to 10).
  • 9 to 18 are optical cross-sectional views when the imaging optical system 1 is in an infinitely focused state. Further, the movement of the focus group (second lens group LG2) during focusing from infinity to the closest distance is indicated by an arrow mF.
  • the position reference mark M1 is provided on the second lens L2, and in Examples 1 to 5, 8, and 10 (5 lenses), the position reference mark M2 is provided on the fifth lens L5.
  • the fourth lens L4 is provided with a position reference mark M2 on the lens surface.
  • the surface number, the radius of curvature r (mm), the shaft upper surface distance d (mm), and the variable distance at the time of focusing are the closest object distance (object The distance between axis top surfaces dm (mm) at a distance of 10 cm, the refractive index nd for the d line (wavelength: 587.56 nm), the Abbe number vd for the d line, and the effective radius (mm) are shown.
  • the surface with * in the surface number is an aspherical surface, and the surface shape is defined by the following formula (AS) using a local orthogonal coordinate system (X, Y, Z) with the surface vertex as the origin. .
  • AS a local orthogonal coordinate system
  • X, Y, Z a local orthogonal coordinate system with the surface vertex as the origin.
  • the focal length and F number of the entire system values in both the focus state at the infinity object distance (object distance: ⁇ ) and the closest object distance (object distance: 10 cm) are shown.
  • the back focus fB represents the distance from the image side surface of the parallel plate PT (same as the filter member 42) to the image plane IM (same as the imaging surface 70a).
  • the focal length of each lens and each lens group is shown as single lens data and lens group data.
  • Table 1 shows values of the examples corresponding to the respective conditional expressions (conditional expressions (1), (2), and (3)).
  • FIGS. 19 to 28 are aberration diagrams of Examples 1 to 10 (EX1 to 10) at an infinite object distance (object distance: ⁇ ).
  • (A) is a spherical aberration diagram
  • (B) is an astigmatism diagram
  • (C) is a distortion aberration diagram.
  • the spherical aberration diagram shows the amount of spherical aberration for the d-line (wavelength 587.56 nm) indicated by the solid line and the amount of spherical aberration for the g-line (wavelength 435.84 nm) indicated by the broken line in the optical axis AX direction from the paraxial image plane.
  • the amount of deviation (unit: mm) is represented, and the vertical axis represents a value obtained by normalizing the incident height to the pupil by the maximum height (that is, relative pupil height).
  • the broken line T represents the tangential image surface with respect to the d line
  • the solid line S represents the sagittal image surface with respect to the d line, expressed as a deviation amount (unit: mm) in the optical axis AX direction from the paraxial image surface.
  • the vertical axis represents the image height (IMG HT, unit: mm).
  • the horizontal axis represents distortion (unit:%) with respect to the d-line
  • the vertical axis represents image height (IMG HT, unit: mm).
  • the maximum value of the image height IMG HT corresponds to the maximum image height Y ′ on the image plane IM (half the diagonal length of the imaging surface 70a of the solid-state imaging device 70).
  • the imaging optical system 1 of Embodiment 1 includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a positive third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces.
  • the first lens L1 is a biconvex positive lens
  • the second lens L2 is a negative meniscus lens concave on the image side
  • the third lens L3 is on the object side.
  • the fourth lens L4 is a positive meniscus lens convex to the image side
  • the fifth lens L5 is a negative meniscus lens concave to the image side.
  • first lens L1 and the second lens L2 have a positive refractive power as a whole
  • first lens group LG1 and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole
  • second lens group LG2 has a positive refractive power as a whole
  • the fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
  • the imaging optical system 1 of Embodiment 2 includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a positive third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces.
  • the first lens L1 is a biconvex positive lens
  • the second lens L2 is a negative meniscus lens concave on the image side
  • the third lens L3 is on the object side.
  • the fourth lens L4 is a positive meniscus lens convex to the image side
  • the fifth lens L5 is a negative meniscus lens concave to the image side.
  • first lens L1 and the second lens L2 have a positive refractive power as a whole
  • first lens group LG1 and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole
  • second lens group LG2 has a positive refractive power as a whole
  • the fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
  • the imaging optical system 1 (see FIG. 11) of Example 3 includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a positive third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces.
  • the first lens L1 is a biconvex positive lens
  • the second lens L2 is a negative meniscus lens concave on the image side
  • the third lens L3 is on the object side.
  • the fourth lens L4 is a positive meniscus lens convex to the image side
  • the fifth lens L5 is a negative meniscus lens concave to the image side.
  • first lens L1 and the second lens L2 have a positive refractive power as a whole
  • first lens group LG1 and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole
  • second lens group LG2 has a positive refractive power as a whole
  • the fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
  • the imaging optical system 1 (see FIG. 12) of Example 4 includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a negative third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces.
  • the first lens L1 is a positive meniscus lens convex on the object side
  • the second lens L2 is a negative meniscus lens concave on the image side
  • the third lens L3 is The negative meniscus lens is concave on the image side
  • the fourth lens L4 is a positive meniscus lens convex on the image side
  • the fifth lens L5 is a negative meniscus lens concave on the image side.
  • first lens L1 and the second lens L2 have a positive refractive power as a whole
  • first lens group LG1 and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole
  • second lens group LG2 has a positive refractive power as a whole
  • the fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
  • the imaging optical system 1 of Embodiment 5 includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a negative third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces.
  • the first lens L1 is a biconvex positive lens
  • the second lens L2 is a negative meniscus lens concave on the image side
  • the third lens L3 is on the image side.
  • the fourth lens L4 is a biconvex positive lens
  • the fifth lens L5 is a negative meniscus lens concave on the image side.
  • first lens L1 and the second lens L2 have a positive refractive power as a whole
  • first lens group LG1 and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole
  • second lens group LG2 has a positive refractive power as a whole
  • the fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
  • the imaging optical system 1 (see FIG. 14) of Example 6 includes, in order from the object side, an aperture stop ST, a positive first lens L1, a negative second lens L2, a positive third lens L3, and a negative 4th lens L4, and all the lens surfaces are aspherical surfaces.
  • the first lens L1 is a biconvex positive lens
  • the second lens L2 is a negative meniscus lens concave on the image side
  • the third lens L3 is biconvex.
  • the fourth lens L4 is a negative meniscus lens that is concave on the image side.
  • the first lens L1 and the second lens L2 as a whole have a first lens group LG1 having a positive refractive power
  • the third lens L3 has a second lens group LG2 as a whole having a positive refractive power
  • L4 constitutes a third lens group LG3 having a negative refractive power as a whole.
  • the imaging optical system 1 includes, in order from the object side, an aperture stop ST, a positive first lens L1, a negative second lens L2, a positive third lens L3, and a negative 4th lens L4, and all the lens surfaces are aspherical surfaces.
  • the first lens L1 is a biconvex positive lens
  • the second lens L2 is a negative meniscus lens concave on the image side
  • the third lens L3 is on the image side.
  • the fourth lens L4 is a negative meniscus lens that is concave on the image side.
  • the first lens L1 and the second lens L2 as a whole have a first lens group LG1 having a positive refractive power
  • the third lens L3 has a second lens group LG2 as a whole having a positive refractive power
  • L4 constitutes a third lens group LG3 having a negative refractive power as a whole.
  • the imaging optical system 1 of Embodiment 8 includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a positive third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces.
  • the first lens L1 is a biconvex positive lens
  • the second lens L2 is a negative meniscus lens concave on the image side
  • the third lens L3 is biconvex.
  • the fourth lens L4 is a positive meniscus lens convex on the image side
  • the fifth lens L5 is a negative meniscus lens concave on the image side.
  • first lens L1 and the second lens L2 have a positive refractive power as a whole
  • first lens group LG1 and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole
  • second lens group LG2 has a positive refractive power as a whole
  • the fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
  • the imaging optical system 1 includes, in order from the object side, an aperture stop ST, a positive first lens L1, a negative second lens L2, a positive third lens L3, and a negative 4th lens L4, and all the lens surfaces are aspherical surfaces.
  • the first lens L1 is a biconvex positive lens
  • the second lens L2 is a negative meniscus lens concave on the image side
  • the third lens L3 is on the image side.
  • the fourth lens L4 is a negative meniscus lens that is concave on the image side.
  • the first lens L1 and the second lens L2 as a whole have a first lens group LG1 having a positive refractive power
  • the third lens L3 has a second lens group LG2 as a whole having a positive refractive power
  • L4 constitutes a third lens group LG3 having a negative refractive power as a whole.
  • the imaging optical system 1 (see FIG. 18) of Example 10 includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a negative third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces.
  • the first lens L1 is a biconvex positive lens
  • the second lens L2 is a biconcave negative lens
  • the third lens L3 is a concave negative lens on the image side.
  • the fourth lens L4 is a biconvex positive lens
  • the fifth lens L5 is a biconcave negative lens.
  • the first lens L1, the second lens L2, and the third lens L3 have a first lens group LG1 having a positive refractive power as a whole, and the fourth lens L4 has a second lens group LG2 having a positive refractive power as a whole.
  • the fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
  • the imaging optical systems of Examples 1 to 10 exhibit good aberration characteristics.
  • all of Examples 1 to 10 satisfy the conditional expressions (1), (2), and (3). That is, according to the present invention, an imaging optical system having good optical characteristics can be obtained with high accuracy and efficiency.
  • the principal ray incident angle of the light beam incident on the imaging surface 70a of the solid-state imaging device 70 is not necessarily designed to be sufficiently small in the periphery of the imaging surface 70a.
  • it has become possible to reduce shading by reviewing the arrangement of the color filters of the solid-state imaging device and the on-chip microlens array.
  • each of the above-described embodiments is a design example aimed at further miniaturization.
  • the position reference mark is provided in the lens center.
  • the position where the position reference mark is provided is not limited to this position.
  • the position reference mark may have the configuration shown in the present embodiment, or may have a ring shape or the like.
  • the present invention is suitable for an imaging optical system that forms an image of a subject on the imaging surface of a solid-state imaging device.

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Abstract

Disclosed is an image pickup optical system (1) which is sequentially provided with, from the object side to the image side: a first lens group (LG1), which is composed of at least two lenses, including a positive lens (first lens (L1)) disposed closest to the object, and has positive refractive power as a whole; a second lens group (LG2), which is composed of at least one lens, and has positive refractive power as a whole; and a third lens group (LG3), which is composed of at least one lens. The first lens group (LG1) and the third lens group (LG3) are fixed to an image pickup surface (70a), the second lens group (LG2) is provided movably in the optical axis direction for the purpose of focus adjustment, and the image pickup optical system (1) satisfies the conditional expression of 0.1<f1/fg2<2, where f1 is the focal point distance of the positive lens closest to the object, fg2 is the focal point distance of the second lens group.

Description

撮像光学系及び光学調整方法Imaging optical system and optical adjustment method
　本発明は、固体撮像素子の撮像面に被写体を結像させる撮像光学系、及び、該撮像光学系の光学調整方法に関する。 The present invention relates to an imaging optical system that forms an image of a subject on an imaging surface of a solid-state imaging device, and an optical adjustment method for the imaging optical system.
　近年においては、ＣＣＤ（Charge　Coupled　Device）型イメージセンサやＣＭＯＳ（Complementary　Metal-Oxide　Semiconductor） 型のイメージセンサ等の固体撮像素子を用いた小型の撮像装置が、携帯電話やＰＤＡ（Personal　Digital　Assistant）等の携帯端末に搭載されるようになっている。このような小型の撮像装置においては、高性能化等の要求により、例えば３枚ないし５枚のレンズを備える撮像光学系が使用されるようになっている。ここで、撮像光学系は、固体撮像素子の撮像面に被写体を結像させる光学系のことである。 In recent years, small imaging devices using solid-state imaging devices such as CCD (Charge Coupled Device) type image sensors and CMOS (Complementary Metal-Oxide Semiconductor) vertical type image sensors have become mobile phones, PDAs (Personal Digital Assistants), etc. On mobile devices. In such a small image pickup apparatus, an image pickup optical system including, for example, three to five lenses is used due to a demand for high performance and the like. Here, the imaging optical system is an optical system that forms an image of a subject on the imaging surface of the solid-state imaging device.
　このような撮像光学系は、例えばカメラ付き携帯電話に搭載される場合等において、オートフォーカス化への要求がある。従来、このような撮像光学系は、レンズ枚数が比較的少ないために単焦点とされ、オートフォーカス化のためのフォーカス調整の方式としては、撮像光学系を構成する全レンズを移動させる全体繰り出し方式が採用されることが多い。しかし、近年の小型・低背化の要求を考慮すると、特許文献１に示されるような、内部の一部のレンズを移動させるインナーフォーカス方式が有利である。 Such an imaging optical system has a demand for autofocusing when mounted on a camera-equipped mobile phone, for example. Conventionally, such an imaging optical system is single-focused because the number of lenses is relatively small, and as a focus adjustment method for auto-focusing, an entire extension system that moves all the lenses constituting the imaging optical system Is often adopted. However, in consideration of the recent demands for small size and low profile, an inner focus system that moves some of the internal lenses as shown in Patent Document 1 is advantageous.
特開２００８－７６９５３号公報JP 2008-76953 A
　しかしながら、インナーフォーカス方式を採用した撮像光学系は、フォーカス調整のために光軸方向に移動する機構を有することになる。このため、インナーフォーカス方式では、メカ部品が増加し、レンズの中心位置が光軸と垂直な方向にずれる偏芯が生じ易い。そして、小型化・高性能化の要求を満たすように構成される撮像光学系においては、製造時に発生した偏芯による悪影響（例えば片ボケ）を受け易いといった問題がある。 However, the imaging optical system that employs the inner focus method has a mechanism that moves in the optical axis direction for focus adjustment. For this reason, in the inner focus method, the number of mechanical parts increases, and the center position of the lens tends to be decentered in a direction perpendicular to the optical axis. An imaging optical system configured to satisfy the demands for miniaturization and high performance is susceptible to an adverse effect (for example, one-sided blur) due to eccentricity generated during manufacturing.
　このような問題を解決するために、製造時の品質管理を厳しくすることも考えられるが、その場合、製造コストが増大するために好ましくない。このために、撮像光学系の組み立て時に、偏芯による光学特性の悪化を補正する偏芯調整（調芯）を行うのが好ましい。しかしながら、スペース上の制約があったり、低コスト化のために効率良く調芯を行うことが求められたり、様々な制約がある。 In order to solve such a problem, it may be possible to tighten quality control at the time of manufacturing, but in that case, it is not preferable because the manufacturing cost increases. For this reason, it is preferable to perform eccentricity adjustment (alignment) that corrects deterioration of optical characteristics due to eccentricity when the imaging optical system is assembled. However, there are various constraints such as space limitations and efficient alignment required for cost reduction.
　そこで、本発明の目的は、小型・低背化が図れ、撮像光学系の組み立て時の調芯が行い易い撮像光学系を提供することである。また、本発明の他の目的は、小型・低背化が図られた撮像光学系における調芯を効率良く行える光学調整方法を提供することである。 Therefore, an object of the present invention is to provide an imaging optical system that can be reduced in size and height and can be easily aligned when the imaging optical system is assembled. Another object of the present invention is to provide an optical adjustment method that can efficiently perform alignment in an imaging optical system that is reduced in size and height.
　上記目的を達成するために本発明の撮像光学系は、固体撮像素子の撮像面に被写体を結像させる単焦点の撮像光学系であって、物体側から像側へと向かって順に、最物体側に配置される正レンズを含む少なくとも２枚のレンズからなって全体として正の屈折力を有する第１レンズ群、少なくとも１枚のレンズからなって全体として正の屈折力を有する第２レンズ群、少なくとも１枚のレンズからなる第３レンズ群を備え、前記第１レンズ群と前記第３レンズ群とは、前記撮像面に対して固定され、前記第２レンズ群は、フォーカス調整のために光軸方向に移動可能に設けられ、以下の条件式を満たすことを特徴としている。
　０．１＜ｆ１／ｆｇ２＜２
但し、ｆ１は最物体側の正レンズの焦点距離、ｆｇ２は第２レンズ群の焦点距離である。 In order to achieve the above object, an imaging optical system according to the present invention is a single-focus imaging optical system that forms an image of a subject on an imaging surface of a solid-state imaging device, and in order from the object side to the image side, A first lens group having at least two lenses including a positive lens disposed on the side and having a positive refractive power as a whole, and a second lens group having at least one lens as a whole and having a positive refractive power as a whole A third lens group including at least one lens, wherein the first lens group and the third lens group are fixed with respect to the imaging surface, and the second lens group is used for focus adjustment. It is provided so as to be movable in the optical axis direction and satisfies the following conditional expression.
0.1 <f1 / fg2 <2
However, f1 is the focal length of the positive lens closest to the object, and fg2 is the focal length of the second lens group.
　本構成の撮像光学系は、第１レンズ群と第３レンズ群との間に配置される第２レンズ群が光軸方向に移動可能に設けられる構成であり、いわゆるインナーフォーカス方式を採用している。このため、全体（全群）繰り出し方式を採用する場合に比べて撮像光学系の小型・低背化を図り易い。 The imaging optical system of this configuration is a configuration in which a second lens group disposed between the first lens group and the third lens group is provided so as to be movable in the optical axis direction, and adopts a so-called inner focus method. Yes. For this reason, it is easy to reduce the size and height of the imaging optical system as compared with the case where the entire (all group) feeding system is adopted.
　そして、最物体側に配置される正レンズの焦点距離と、可動する第２レンズ群の焦点距離とを所定の条件式を満足する構成としている。このため、撮像光学系の組み立て時に、最物体側に配置される正レンズを光軸と垂直な方向に動かすことによって光学系全体の偏芯調整を容易に行えるとともに、撮像光学系の小型化を維持できるようになっている。 The focal length of the positive lens arranged on the most object side and the focal length of the movable second lens group are configured to satisfy a predetermined conditional expression. For this reason, when the imaging optical system is assembled, the decentering of the entire optical system can be easily adjusted by moving the positive lens arranged on the most object side in the direction perpendicular to the optical axis, and the imaging optical system can be downsized. It can be maintained.
　なお、本構成では、第１レンズ群が最物体側に正レンズを含む少なくとも２枚のレンズからなる構成としている。この構成では、例えば第１レンズ群の中に少なくも１枚の負レンズを含む構成とすることで、球面収差と軸上色収差の補正を効果的に行うことが可能になり、撮像光学系の光学性能を良好とし易い。 In this configuration, the first lens group is configured by at least two lenses including a positive lens on the most object side. In this configuration, for example, by including at least one negative lens in the first lens group, it is possible to effectively correct the spherical aberration and the axial chromatic aberration. It is easy to improve the optical performance.
　また、本構成の撮像光学系は、更に以下の条件式を満たすのが好ましい。
　０．１＜ｆｇ２／ｆ＜２
但し、ｆｇ２は第２レンズ群の焦点距離、ｆは撮像光学系全体の焦点距離である。 Moreover, it is preferable that the imaging optical system of this structure satisfy | fills the following conditional expressions further.
0.1 <fg2 / f <2
Here, fg2 is the focal length of the second lens group, and f is the focal length of the entire imaging optical system.
　また、本構成の撮像光学系は、更に以下の条件式を満たすのが好ましい。
　１．０＜ｆｇ１／ｆ＜３．０
但し、ｆｇ１は第１レンズ群の焦点距離、ｆは撮像光学系全体の焦点距離である。 Moreover, it is preferable that the imaging optical system of this structure satisfy | fills the following conditional expressions further.
1.0 <fg1 / f <3.0
Here, fg1 is the focal length of the first lens group, and f is the focal length of the entire imaging optical system.
　上記構成の撮像光学系は、前記第１レンズ群を保持する第１の保持部材と、前記第２レンズ群を保持する第２の保持部材と、前記第３レンズ群を保持する第３の保持部材と、を有し、前記第１の保持部材のレンズ保持空間は、光軸と垂直な方向の直径が前記最物体側に配置される正レンズの直径よりも大きく形成されているのが好ましい。 The imaging optical system having the above configuration includes a first holding member that holds the first lens group, a second holding member that holds the second lens group, and a third holding that holds the third lens group. The lens holding space of the first holding member is preferably formed such that the diameter in the direction perpendicular to the optical axis is larger than the diameter of the positive lens arranged on the most object side. .
　本構成によれば、撮像光学系の組み立て時に、最物体側に配置される正レンズのみを動かして光学系全体の偏芯調整を行うことが可能であり、効率良く偏芯調整を行える。また、群単位でレンズを動かせるために、最物体側に配置される正レンズを光軸に対して垂直な方向に動かして偏芯調整を行い、更に、第１レンズ群を光軸方向に動かして像面湾曲の補正を行うといったことも可能である。 According to this configuration, when the imaging optical system is assembled, it is possible to adjust the eccentricity of the entire optical system by moving only the positive lens arranged on the most object side, and the eccentricity can be adjusted efficiently. In order to move the lens in units of groups, the positive lens arranged on the most object side is moved in the direction perpendicular to the optical axis to adjust the eccentricity, and further, the first lens group is moved in the optical axis direction. It is also possible to correct field curvature.
　また、上記構成において、前記第１の保持部材は、前記レンズ保持空間の周囲に調整治具を配置するための空間部を更に備えるのが好ましい。このように構成することで、最物体側に配置される正レンズを光軸に対して垂直な方向に動かすとともに、光軸方向に移動させるといった光学調整も容易となり、片ボケと像面湾曲とを補正して良好な光学特性を得やすい。そして、この構成において、前記第１の保持部材は、前記最物体側に配置される正レンズの側面を接着固定するための接着剤充填部を更に備え、前記空間部が前記接着剤充填部を挟むように、前記空間部と前記接着剤充填部とが前記第１の保持部材の円周方向に配列されていることとしてもよい。 Further, in the above configuration, it is preferable that the first holding member further includes a space portion for arranging an adjustment jig around the lens holding space. Such a configuration facilitates optical adjustment such as moving the positive lens arranged on the most object side in the direction perpendicular to the optical axis and moving in the optical axis direction. This makes it easy to obtain good optical characteristics. In this configuration, the first holding member further includes an adhesive filling portion for bonding and fixing a side surface of the positive lens disposed on the most object side, and the space portion includes the adhesive filling portion. The space portion and the adhesive filling portion may be arranged in a circumferential direction of the first holding member so as to be sandwiched.
　上記構成の撮像光学系において、前記第３レンズ群には負レンズが含まれるのが好ましい。本構成によれば、いわゆるテレフォトタイプのレンズ構成によって、撮像光学系の全長の小型化（低背化）が可能である。 In the imaging optical system configured as described above, it is preferable that the third lens group includes a negative lens. According to this configuration, the total length of the imaging optical system can be reduced (lower profile) by a so-called telephoto type lens configuration.
　上記目的を達成するために本発明の光学調整方法は、物体側から像側へと向かって順に、最物体側に配置される正レンズを含む少なくとも２枚のレンズからなって全体として正の屈折力を有する第１レンズ群、少なくとも１枚のレンズからなって全体として正の屈折力を有する第２レンズ群、少なくとも１枚のレンズからなる第３レンズ群を備え、前記第１レンズ群と前記第３レンズ群とは撮像面に対して固定され、前記第２レンズ群はフォーカス調整のために光軸方向に移動可能に設けられる単焦点の撮像光学系の光学調整方法であって、前記最物体側の正レンズを光軸と垂直な方向に動かして光学系全体の偏芯調整を行う調芯工程を備えることを特徴としている。 In order to achieve the above object, the optical adjustment method of the present invention is composed of at least two lenses including a positive lens arranged on the most object side in order from the object side to the image side. A first lens group having power, a second lens group including at least one lens and having a positive refractive power as a whole, and a third lens group including at least one lens, and the first lens group and the The third lens group is an optical adjustment method of a single-focus imaging optical system that is fixed with respect to the imaging surface, and the second lens group is provided so as to be movable in the optical axis direction for focus adjustment. It is characterized by comprising an alignment process for adjusting the decentration of the entire optical system by moving the positive lens on the object side in the direction perpendicular to the optical axis.
　本構成によれば、最物体側の正レンズを移動するだけで光学系全体の偏芯調整が行われるために、良好な光学性能を有する（片ボケが抑制された）撮像光学系を効率良く得られる。また、最物体側の正レンズは他のレンズと比較してレンズ径を小さくできるものであるために、本構成の方法を採用すれば、撮像光学系の大型化を抑制できるといった利点も有する。 According to this configuration, since the decentration adjustment of the entire optical system is performed simply by moving the positive lens on the most object side, an imaging optical system having good optical performance (in which one blur is suppressed) can be efficiently performed. can get. Further, since the positive lens on the most object side can reduce the lens diameter as compared with other lenses, there is an advantage that the enlargement of the imaging optical system can be suppressed by adopting the method of this configuration.
　上記構成の光学調整方法において、前記撮像光学系は、以下の条件式を満たすのが好ましい。
　０．１＜ｆ１／ｆｇ２＜２
但し、ｆ１は最物体側の正レンズの焦点距離、ｆｇ２は第２レンズ群の焦点距離である。 In the optical adjustment method having the above configuration, the imaging optical system preferably satisfies the following conditional expression.
0.1 <f1 / fg2 <2
However, f1 is the focal length of the positive lens closest to the object, and fg2 is the focal length of the second lens group.
　上記構成の光学調整方法において、前記第２レンズ群の傾きを調整する傾き調整工程を更に備え、前記調芯工程は前記傾き調整工程後に行われるのが好ましい。本構成によれば、第２レンズ群の傾き除去し、その後に残存する平行偏芯（片ボケの原因となる）を補正することになる。このために、良好な光学性能が得やすく、また、効率良く光学調整が行える。 It is preferable that the optical adjustment method having the above-described configuration further includes an inclination adjustment step of adjusting the inclination of the second lens group, and the alignment step is performed after the inclination adjustment step. According to this configuration, the inclination of the second lens group is removed, and the remaining parallel eccentricity (which causes a one-sided blur) is corrected. For this reason, good optical performance can be easily obtained, and optical adjustment can be performed efficiently.
　上記構成の光学調整方法において、前記調芯工程を行う際に、前記最物体側の正レンズを光軸方向に動かす位置調整が併せて行われることとしてもよい。本構成によれば、片ボケと像面湾曲との両方の補正を同時に行うことができる。 In the optical adjustment method having the above configuration, when performing the alignment step, position adjustment for moving the most object side positive lens in the optical axis direction may be performed together. According to this configuration, it is possible to simultaneously correct both the one-sided blur and the field curvature.
　上記構成の光学調整方法において、前記調芯工程後に、前記第１レンズ群を光軸方向に動かす位置調整が行われることとしてもよい。本構成によれば、片ボケと像面湾曲との両方の補正を行うことができる。また、本構成では最物体側の正レンズだけでなく、第１レンズ群を全て光軸方向に動かす構成であり、調整作業が行い易いといった利点も有する。 In the optical adjustment method having the above-described configuration, position adjustment for moving the first lens group in the optical axis direction may be performed after the alignment step. According to this configuration, both the one-sided blur and the curvature of field can be corrected. Further, in this configuration, not only the positive lens on the most object side but also all the first lens units are moved in the optical axis direction, and there is an advantage that adjustment work is easy.
　上記構成の光学調整方法において、前記調芯工程は、光学調整専用に準備された固体撮像素子を用いて行われることとしてもよいし、製品として組み込まれた固体撮像素子を用いて行われることとしてもよい。 In the optical adjustment method having the above-described configuration, the alignment step may be performed using a solid-state imaging device prepared exclusively for optical adjustment, or may be performed using a solid-state imaging device incorporated as a product. Also good.
　前者の方法によれば、安定した品質の撮像光学系を得ることができ、前者の方法は、例えば撮像光学系を販売する業者に好適である。また、後者の方法によれば、光学特性の良好な撮像装置（撮像光学系に固体撮像素子を組み込んだ装置）を得ることができ、後者の方法は、例えば撮像装置を販売する業者に好適である。 According to the former method, an imaging optical system having a stable quality can be obtained, and the former method is suitable for, for example, a trader who sells an imaging optical system. Further, according to the latter method, it is possible to obtain an imaging device with good optical characteristics (a device in which a solid-state imaging device is incorporated in an imaging optical system), and the latter method is suitable for a trader who sells imaging devices, for example. is there.
　上記構成の光学調整方法において、前記第１レンズ群には、前記最物体側に配置される正レンズとは異なるレンズであって第１の位置基準マークを有するレンズが含まれ、前記第３レンズ群には第２の位置基準マークを有するレンズが含まれ、前記最物体側に配置される正レンズを前記第１レンズ群に含ませる前に、光軸に沿う方向から観察した場合に、前記第１の位置基準マークと前記第２の位置基準マークとが一致するように、前記第１レンズ群と前記第３レンズ群との相対位置調整が行われることとしてもよい。この場合において、前記撮像光学系は、以下の条件式を満たすのが好ましい。
　０．１＜ｆｇ２／ｆ＜２
但し、ｆｇ２は第２レンズ群の焦点距離、ｆは撮像光学系全体の焦点距離である。 In the optical adjustment method configured as described above, the first lens group includes a lens that is different from a positive lens disposed on the most object side and has a first position reference mark, and the third lens. The group includes a lens having a second position reference mark, and when the positive lens arranged on the most object side is observed from the direction along the optical axis before being included in the first lens group, The relative position adjustment of the first lens group and the third lens group may be performed so that the first position reference mark and the second position reference mark coincide with each other. In this case, it is preferable that the imaging optical system satisfies the following conditional expression.
0.1 <fg2 / f <2
Here, fg2 is the focal length of the second lens group, and f is the focal length of the entire imaging optical system.
　本発明によると、小型・低背化が図れ、撮像光学系の組み立て時の調芯が行い易い撮像光学系を提供できる。また、調芯を行い易いために、撮像光学系の光学調整を効率良く行える。したがって、本発明によれば、小型・低背化を図れ、片ボケを抑制した良好な光学特性を有する撮像光学系や撮像装置を提供できる。 According to the present invention, it is possible to provide an imaging optical system that can be reduced in size and height and can be easily aligned when the imaging optical system is assembled. In addition, since it is easy to perform alignment, optical adjustment of the imaging optical system can be performed efficiently. Therefore, according to the present invention, it is possible to provide an image pickup optical system and an image pickup apparatus having good optical characteristics that can be reduced in size and height and suppress one-side blur.
本実施形態の撮像光学系を備える光学ユニットの構成を示す概略斜視図Schematic perspective view showing a configuration of an optical unit including the imaging optical system of the present embodiment 本実施形態の撮像光学系を備える光学ユニットの構成を示す概略分解斜視図Schematic exploded perspective view showing the configuration of an optical unit including the imaging optical system of the present embodiment 本実施形態の撮像光学系を備える光学ユニットの概略断面図Schematic sectional view of an optical unit including the imaging optical system of the present embodiment 本実施形態の撮像光学系の組み立て手順を示すフローチャートThe flowchart which shows the assembly procedure of the imaging optical system of this embodiment 本実施形態の撮像光学系の組み立て途中の状態（第１の状態）を示す概略断面図Schematic sectional view showing a state (first state) during assembly of the imaging optical system of the present embodiment 本実施形態の撮像光学系の組み立て途中の状態（第２の状態）を示す概略断面図Schematic sectional view showing a state (second state) during assembly of the imaging optical system of the present embodiment 本実施形態の撮像光学系の組み立て途中の状態を示す概略断面図で、第１レンズの調芯工程を説明するための図FIG. 5 is a schematic cross-sectional view showing a state during the assembly of the imaging optical system of the present embodiment, and is a diagram for explaining a first lens alignment process; 本実施形態の第１のレンズホルダーを上から見た場合の概略平面図で、第１レンズがホルダー内に挿入された状態を示す図The top view of the 1st lens holder of this embodiment when it sees from the top, and the figure showing the state where the 1st lens was inserted in the holder 実施例１の撮像光学系の構成図Configuration diagram of the imaging optical system of Example 1 実施例２の撮像光学系の構成図Configuration diagram of the imaging optical system of Example 2 実施例３の撮像光学系の構成図Configuration diagram of the imaging optical system of Example 3 実施例４の撮像光学系の構成図Configuration diagram of the imaging optical system of Example 4 実施例５の撮像光学系の構成図Configuration diagram of image pickup optical system of Embodiment 5 実施例６の撮像光学系の構成図Configuration diagram of the imaging optical system of Example 6 実施例７の撮像光学系の構成図Configuration diagram of the imaging optical system of Example 7 実施例８の撮像光学系の構成図Configuration diagram of imaging optical system of embodiment 8 実施例９の撮像光学系の構成図Configuration diagram of image pickup optical system of Embodiment 9 実施例１０の撮像光学系の構成図Configuration diagram of imaging optical system of Example 10 実施例１の無限遠物体距離時の収差図Aberration diagram of Example 1 at infinity object distance 実施例２の無限遠物体距離時の収差図Aberration diagram of Example 2 at object distance at infinity 実施例３の無限遠物体距離時の収差図Aberration diagram of Example 3 at infinity object distance 実施例４の無限遠物体距離時の収差図Aberration diagram of Example 4 at infinity object distance 実施例５の無限遠物体距離時の収差図Aberration diagram of Example 5 at infinity object distance 実施例６の無限遠物体距離時の収差図Aberration diagram of Example 6 at infinity object distance 実施例７の無限遠物体距離時の収差図Aberration diagram of Example 7 at infinity object distance 実施例８の無限遠物体距離時の収差図Aberration diagram of Example 8 at infinity object distance 実施例９の無限遠物体距離時の収差図Aberration diagram of Example 9 at object distance at infinity 実施例１０の無限遠物体距離時の収差図Aberration diagram of Example 10 at infinity object distance
　以下、本発明の、固体撮像素子の撮像面に被写体を結像させる単焦点の撮像光学系、及び、光学調整方法の実施形態について、図面を参照しながら詳細に説明する。 Hereinafter, embodiments of a single-focus imaging optical system and an optical adjustment method for imaging a subject on an imaging surface of a solid-state imaging device according to the present invention will be described in detail with reference to the drawings.
（撮像光学系の構成）
　まず、本実施形態の撮像光学系の構成について、図１から図３を参照しながら説明する。図１は、本実施形態の撮像光学系を備える光学ユニットの構成を示す概略斜視図である。図２は、本実施形態の撮像光学系を備える光学ユニットの構成を示す概略分解斜視図である。図３は、本実施形態の撮像光学系を備える光学ユニットの概略断面図である。 (Configuration of imaging optical system)
First, the configuration of the imaging optical system of the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic perspective view illustrating a configuration of an optical unit including an imaging optical system according to the present embodiment. FIG. 2 is a schematic exploded perspective view showing a configuration of an optical unit including the imaging optical system of the present embodiment. FIG. 3 is a schematic cross-sectional view of an optical unit including the imaging optical system of the present embodiment.
　本実施形態の撮像光学系１（図１及び図３参照）を備える光学ユニット１０は、図２に示すように、大きくは、１群ユニットＧ１と、２群ユニットＧ２と、３群ユニットＧ３と、アクチュエータユニットＡ１と、を備える構成となっている。 As shown in FIG. 2, the optical unit 10 including the imaging optical system 1 (see FIGS. 1 and 3) of the present embodiment is roughly divided into a first group unit G1, a second group unit G2, and a third group unit G3. The actuator unit A1 is provided.
　１群ユニットＧ１は、物体側から像側に向かって順に、ドーナツ型の円板部品からなる第１の遮光板１１、第１レンズＬ１、ドーナツ型の円板部品からなる第２の遮光板１２、及び第２レンズＬ２を備え、これらが第１のレンズホルダー（本発明の第１の保持部材の実施形態）１３に保持される構成となっている。すなわち、本実施形態においては、第１レンズＬ１及び第２レンズＬ２によって第１レンズ群ＬＧ１が形成されている。なお、平面視略円板状の有底の皿型部材である第１のレンズホルダー１３は、厚み方向に第１レンズ群ＬＧ１を保持するレンズ保持空間１３ａを有する。また、第１のレンズホルダー１３の底部には光を通過させるための開口１３ｂが形成されている。 The first unit G1, in order from the object side to the image side, includes a first light shielding plate 11 made of a donut-shaped disk component, a first lens L1, and a second light shielding plate 12 made of a donut-shaped disk component. And the second lens L2, and these are held by the first lens holder (embodiment of the first holding member of the present invention) 13. That is, in the present embodiment, the first lens group LG1 is formed by the first lens L1 and the second lens L2. The first lens holder 13, which is a bottomed plate-shaped member having a substantially disk shape in plan view, has a lens holding space 13a for holding the first lens group LG1 in the thickness direction. In addition, an opening 13 b for allowing light to pass through is formed at the bottom of the first lens holder 13.
　この１群ユニットＧ１（第１レンズ群ＬＧ１）は、光学ユニット１０に取り付けられる固体撮像素子７０（例えばＣＣＤ型のイメージセンサやＣＭＯＳ型のイメージセンサ等；図３に破線で示す）の撮像面７０ａに対して動かないように固定状態とされる。第１レンズＬ１は正レンズ、第２レンズは負レンズとなっており、第１レンズＬ１及び第２レンズＬ２で構成される第１レンズ群ＬＧ１は全体として正の屈折力を有している。 The first group unit G1 (first lens group LG1) is an imaging surface 70a of a solid-state imaging device 70 (for example, a CCD type image sensor, a CMOS type image sensor, etc .; indicated by a broken line in FIG. 3) attached to the optical unit 10. It is fixed so as not to move. The first lens L1 is a positive lens, the second lens is a negative lens, and the first lens group LG1 including the first lens L1 and the second lens L2 has a positive refractive power as a whole.
　なお、第１レンズ群ＬＧ１（１群ユニットＧ１内に設けられるレンズ群）は、最物体側に正レンズ（本実施形態の第１レンズＬ１）が配置され、全体として正の屈折力（正パワー）を有する構成であれば、３枚以上のレンズで構成しても構わない。また、球面収差と軸上色収差の補正を効果的に行うことを可能とすべく、第１レンズ群ＬＧ１には、少なくとも１枚の正レンズと少なくとも１枚の負レンズが含まれるのが好ましい。 The first lens group LG1 (the lens group provided in the first group unit G1) has a positive lens (the first lens L1 of the present embodiment) disposed on the most object side, and has a positive refractive power (positive power as a whole). ) May be configured with three or more lenses. In order to effectively correct the spherical aberration and the axial chromatic aberration, it is preferable that the first lens group LG1 includes at least one positive lens and at least one negative lens.
　第１レンズ群ＬＧ１に含まれる第２レンズＬ２の物体側表面の略中心部分には、図３に拡大図（破線円内の図）で示すように位置基準マークＭ１が形成されている。すなわち、第２レンズＬ２は、位置基準マークが施されたマークレンズとなっている。この位置基準マークＭ１は、本実施形態においてはレンズ表面に窪み（凹部）を設けることによって得ている。このような位置基準マークＭ１は、例えばレンズ表面を切削加工して得てもよいし、レンズを製造する金型に突起部を設けておいて得るようにしてもよい。 A position reference mark M1 is formed at a substantially central portion of the object-side surface of the second lens L2 included in the first lens group LG1, as shown in an enlarged view in FIG. That is, the second lens L2 is a mark lens provided with a position reference mark. In the present embodiment, the position reference mark M1 is obtained by providing a depression (recess) on the lens surface. Such a position reference mark M1 may be obtained, for example, by cutting the lens surface, or may be obtained by providing a protrusion on a mold for manufacturing the lens.
　なお、位置基準マークＭ１の構成は本実施形態の構成に限定される趣旨ではなく、例えばレンズ表面に凸部を設けることによって得てもよいし、また、インクジェット等を用いて得たドット等であってもよい。また、本実施形態では、位置基準マークＭ１を物体側表面に設ける構成としているが、像側表面に設ける構成としても構わない。また、位置基準マークＭ１は、マーカーとしての機能を発揮する範囲で、撮像光学系１の光学性能に影響を与えないように、なるべく小さく形成するのが好ましい。 The configuration of the position reference mark M1 is not limited to the configuration of the present embodiment. For example, the position reference mark M1 may be obtained by providing a convex portion on the lens surface, or may be a dot obtained by using an inkjet or the like. There may be. In the present embodiment, the position reference mark M1 is provided on the object side surface, but may be provided on the image side surface. In addition, the position reference mark M1 is preferably formed as small as possible so as not to affect the optical performance of the imaging optical system 1 within a range in which the function as a marker is exhibited.
　２群ユニットＧ２は、物体側から像側に向かって順に、第３レンズＬ３、ドーナツ型の円板部品からなる第３の遮光板２１、第４レンズＬ４を備え、これらが第２のレンズホルダー（本発明の第２の保持部材の実施形態）２２に保持される構成となっている。すなわち、本実施形態においては、第３レンズＬ３及び第４レンズＬ４によって第２レンズ群ＬＧ２が形成されている。なお、第２レンズホルダー２２は、円筒状の貫通空間２２ａを有し、この貫通空間２２ａ内に第２レンズ群ＬＧ２は保持される。 The second group unit G2 includes, in order from the object side to the image side, a third lens L3, a third light-shielding plate 21 made of a donut-shaped disk component, and a fourth lens L4, which are a second lens holder. (Embodiment of the 2nd holding member of this invention) It becomes the structure hold | maintained by 22. FIG. That is, in the present embodiment, the second lens group LG2 is formed by the third lens L3 and the fourth lens L4. The second lens holder 22 has a cylindrical through space 22a, and the second lens group LG2 is held in the through space 22a.
　この２群ユニットＧ２（第２レンズ群ＬＧ２）は、詳細は後述するアクチュエータユニットＡ１によって光軸方向（図３の符号ＡＸが光軸である）に移動可能となっている。すなわち、本実施形態の撮像光学系１は、いわゆるインナーフォーカス方式を採用している。第２レンズ群ＬＧ２（２群ユニットＧ２内に設けられるレンズ群）は、全体して正の屈折力を有するように構成されている。 The second group unit G2 (second lens group LG2) can be moved in the optical axis direction (reference numeral AX in FIG. 3 is the optical axis) by an actuator unit A1 described later in detail. That is, the imaging optical system 1 of the present embodiment employs a so-called inner focus method. The second lens group LG2 (lens group provided in the second group unit G2) is configured to have a positive refractive power as a whole.
　なお、第２レンズ群ＬＧ２を構成するレンズの枚数は、本実施形態の構成（２枚）に限らず、１枚或いは３枚以上としてもよい。第２レンズ群ＬＧ２を２枚で構成する場合、例えば、第３レンズＬ３及び第４レンズＬ４をいずれも正レンズとしたり、第３レンズＬ３を負レンズ、第４レンズＬ４を正レンズとしたりしてよい。 Note that the number of lenses constituting the second lens group LG2 is not limited to the configuration (two) in the present embodiment, and may be one or three or more. When the second lens group LG2 is composed of two lenses, for example, the third lens L3 and the fourth lens L4 are both positive lenses, the third lens L3 is a negative lens, and the fourth lens L4 is a positive lens. It's okay.
　３群ユニットＧ３は、物体側から像側に向かって順に、第５レンズＬ５、例えばＩＲカットフィルタや光学的ローパスフィルタ等の平行平板からなるフィルタ部材４２を備え、これらが第１のフレーム（保持部材）４１によって保持される構成となっている。第１のフレーム４１は、厚み方向に貫通した空間４１ａを有し、光が厚み方向に通過できるようになっている。この３群ユニットＧ３（第５レンズＬ３からなる第３レンズ群ＬＧ３）は、１群ユニットＧ１と同様に、光学ユニット１０に取り付けられる固体撮像素子７０の撮像面７０ａに対して動かないように固定状態とされる。 The third group unit G3 includes, in order from the object side to the image side, a fifth lens L5, for example, a filter member 42 made of a parallel plate such as an IR cut filter or an optical low-pass filter, and these are the first frame (holding). Member) 41. The first frame 41 has a space 41a penetrating in the thickness direction so that light can pass in the thickness direction. The third group unit G3 (the third lens group LG3 including the fifth lens L3) is fixed so as not to move with respect to the imaging surface 70a of the solid-state imaging device 70 attached to the optical unit 10, similarly to the first group unit G1. State.
　なお、本実施形態では、負レンズである第５レンズＬ５のみによって第３レンズ群ＬＧ３が形成されているが、これに限られる趣旨ではない。すなわち、第３レンズ群ＬＧ３は、複数枚のレンズで構成されても構わないし、また、全体として正の屈折力でも負の屈折力でも構わない。ただし、第３レンズ群ＬＧ３には負レンズが含まれるのが好ましく、これにより、いわゆるテレフォトタイプの構成が得られ、撮像光学系１０の全長を短くできる（小型化・低背化を図れる）。 In the present embodiment, the third lens group LG3 is formed only by the fifth lens L5, which is a negative lens. However, the present invention is not limited to this. That is, the third lens group LG3 may be composed of a plurality of lenses, and may have a positive refractive power or a negative refractive power as a whole. However, it is preferable that the third lens group LG3 includes a negative lens, thereby obtaining a so-called telephoto type configuration and shortening the overall length of the imaging optical system 10 (a reduction in size and height). .
　第３レンズ群ＬＧ３に含まれる第５レンズＬ５の物体側表面の略中心部分には、図３に拡大図（破線円内の図）で示すように位置基準マークＭ２が形成されている。すなわち、第５レンズＬ５は、位置基準マークが施されたマークレンズとなっている。第５レンズＬ５に設ける位置基準マークＭ２は、本実施形態においてはレンズ表面に窪み（凹部）を設けることによって得ている。このような位置基準マークＭ２の形成方法及び留意点は、第２レンズＬ２に設けた位置基準マークＭ１と同様である。また、第５レンズＬ５に設ける位置基準マークＭ２についても、第２レンズＬ２に設ける位置基準マークＭ１の場合と同様に、別の構成（凸部やドット等）に変更しても構わない。 A position reference mark M2 is formed at a substantially central portion of the object-side surface of the fifth lens L5 included in the third lens group LG3 as shown in an enlarged view in FIG. That is, the fifth lens L5 is a mark lens provided with a position reference mark. In the present embodiment, the position reference mark M2 provided on the fifth lens L5 is obtained by providing a recess (concave portion) on the lens surface. The method of forming the position reference mark M2 and the points to be noted are the same as those of the position reference mark M1 provided on the second lens L2. Further, the position reference mark M2 provided on the fifth lens L5 may be changed to another configuration (such as a convex portion or a dot) as in the case of the position reference mark M1 provided on the second lens L2.
　アクチュエータユニットＡ１は、撮像光学系１をインナーフォーカス方式とすべく、２群ユニットＧ２（第２レンズ群ＬＧ２）を光軸方向に移動可能とする駆動機構である。このアクチュエータユニットＡ１は、ＳＩＤＭ（Smooth　Impact　Drive　Mechanism；登録商標）アクチュエータ３１と称される、小型化に好適な超音波リニアアクチュエータを用いて構成されている。なお、このアクチュエータについては、例えば本出願人が先に特開２００１－２６８９５１号公報などで提案している。 The actuator unit A1 is a drive mechanism that allows the second group unit G2 (second lens group LG2) to move in the optical axis direction so that the imaging optical system 1 is an inner focus type. This actuator unit A1 is configured using an ultrasonic linear actuator that is referred to as a SIDM (Smooth Impact Drive Mechanism; registered trademark) actuator 31 and is suitable for miniaturization. For example, the present applicant has previously proposed this actuator in Japanese Patent Laid-Open No. 2001-268951.
　ＳＩＤＭアクチュエータ３１は、図３に示すように、軸方向が光軸方向と平行になるように配置されるＳＩＤＭ軸３１ａと、ＳＩＤＭ軸３１ａの一端に接着固定され、ＳＩＤＭ軸３１ａの軸方向に伸縮する圧電素子３１ｂと、圧電素子３１ｂのＳＩＤＭ軸３１ａが接着固定される側と反対の端部に接着固定される錘３１ｃと、からなっている。ＳＩＤＭアクチュエータ３１には、図２に示すように、圧電素子３１ｂを駆動するためのリード線３２と端子３３とが半田付けにて取り付けられている。 As shown in FIG. 3, the SIDM actuator 31 is bonded and fixed to one end of the SIDM shaft 31a and the SIDM shaft 31a arranged so that the axial direction is parallel to the optical axis direction, and expands and contracts in the axial direction of the SIDM shaft 31a. And a weight 31c that is bonded and fixed to the end of the piezoelectric element 31b opposite to the side to which the SIDM shaft 31a is bonded and fixed. As shown in FIG. 2, a lead wire 32 and a terminal 33 for driving the piezoelectric element 31b are attached to the SIDM actuator 31 by soldering.
　ＳＩＤＭアクチュエータ３１を駆動させる場合には、端子３３及びリード線３２を介して圧電素子３１ｂに駆動信号を与える。駆動信号が与えられると圧電素子３１ｂは伸縮し、この伸縮によってＳＩＤＭ軸３１ａが軸方向に振動する。この時の振動波形を適切に制御することにより、ＳＩＤＭ軸３１ａに摩擦係合している（この係合は板バネ２３によって実現されている）第２のレンズホルダー２２を目的の方向（図３の上方向或いは下方向）にのみ摺動させることができる。このため、ＳＩＤＭアクチュエータ３１によって、第２レンズ群ＬＧ２の光軸方向への移動が可能となる。なお、錘３１ｃは、圧電素子３１ｂの伸縮による変位をＳＩＤＭ軸３１ａ側にのみ発生させる目的で設けられている。 When driving the SIDM actuator 31, a drive signal is given to the piezoelectric element 31b via the terminal 33 and the lead wire 32. When a drive signal is applied, the piezoelectric element 31b expands and contracts, and the SIDM shaft 31a vibrates in the axial direction due to the expansion and contraction. By appropriately controlling the vibration waveform at this time, the second lens holder 22 that is frictionally engaged with the SIDM shaft 31a (this engagement is realized by the leaf spring 23) is moved in the target direction (FIG. 3). (Upward direction or downward direction). For this reason, the SIDM actuator 31 can move the second lens group LG2 in the optical axis direction. The weight 31c is provided for the purpose of generating displacement due to expansion and contraction of the piezoelectric element 31b only on the side of the SIDM shaft 31a.
　以上の１群ユニットＧ１、２群ユニットＧ２、３群ユニットＧ３、及びアクチュエータユニットＡ１を、第２のフレーム５０及びカバー６０と組み合せて組み立てることにより、本実施形態の単焦点・インナーフォーカス方式の撮像光学系１（光学ユニット１０）が得られる。撮像光学系１（光学ユニット１０）の組み立ての詳細は後述する。 By combining the first group unit G1, the second group unit G2, the third group unit G3, and the actuator unit A1 in combination with the second frame 50 and the cover 60, the single focus / inner focus type imaging of the present embodiment is performed. The optical system 1 (optical unit 10) is obtained. Details of the assembly of the imaging optical system 1 (optical unit 10) will be described later.
　なお、本実施形態においては、撮像光学系１を構成する５つのレンズＬ１～Ｌ５はいずれもプラスチック材料で形成されている。勿論、これらのレンズＬ１～Ｌ５をガラスによって構成してもよい。ただし、本実施形態の撮像光学系１においては、各レンズＬ１～Ｌ５の曲率半径や外径がかなり小さくなってガラスレンズとすると大量生産に不向きであること等を考慮して、各レンズをプラスチック材料で形成している。 In the present embodiment, the five lenses L1 to L5 constituting the imaging optical system 1 are all made of a plastic material. Of course, these lenses L1 to L5 may be made of glass. However, in the imaging optical system 1 of the present embodiment, considering that the curvature radii and outer diameters of the lenses L1 to L5 are considerably small and are not suitable for mass production if glass lenses are used, the lenses are made of plastic. It is made of material.
　ここで、撮像光学系１を構成するレンズをプラスチック材料で形成する場合の留意点について述べておく。プラスチック材料は温度変化時の屈折率変化が大きいため、本実施形態のように全てのレンズをプラスチックレンズで構成すると、周囲温度が変化した際に、撮像光学系１の像点位置が変動してしまうという問題をかかえることになる。しかし最近では、プラスチック材料中に無機微粒子を混合させると、プラスチック材料が受ける温度変化の影響を小さくできることが分かってきた。 Here, the points to be noted when the lens constituting the imaging optical system 1 is formed of a plastic material will be described. Since the plastic material has a large refractive index change at the time of temperature change, if all the lenses are made of plastic lenses as in this embodiment, the image point position of the imaging optical system 1 fluctuates when the ambient temperature changes. It will have a problem of end. Recently, however, it has been found that mixing inorganic fine particles in a plastic material can reduce the effect of temperature changes on the plastic material.
　詳細に説明すると、一般に透明なプラスチック材料に微粒子を混合させると、光の散乱が生じて透過率が低下するため、微粒子が混合されたプラスチック材料は光学材料として使用することは困難であった。しかし、微粒子の大きさを透過光束の波長より小さくすることにより、散乱が実質的に発生しないようにすることができる。また、プラスチック材料は温度が上昇することにより屈折率が低下してしまうが、無機粒子は温度が上昇すると屈折率が上昇する。そこで、これらの温度依存性を利用して互いに打ち消し合うように作用させることにより、屈折率変化がほとんど生じないようにすることができる。具体的には、母材となるプラスチック材料に最大長が２０ナノメートル以下の無機粒子を分散させることにより、屈折率の温度依存性のきわめて低いプラスチック材料とすることができる。例えば、アクリル樹脂に酸化ニオブ（Ｎｂ2Ｏ5）の微粒子を分散させることにより、温度変化による屈折率変化を小さくすることができる。 More specifically, generally, when fine particles are mixed in a transparent plastic material, light scattering occurs and the transmittance is lowered. Therefore, it is difficult to use a plastic material mixed with fine particles as an optical material. However, by making the size of the fine particles smaller than the wavelength of the transmitted light beam, it is possible to substantially prevent scattering. In addition, the refractive index of the plastic material decreases as the temperature increases, but the refractive index of the inorganic particles increases as the temperature increases. Therefore, it is possible to make almost no change in the refractive index by using these temperature dependencies so as to cancel each other. Specifically, by dispersing inorganic particles having a maximum length of 20 nanometers or less in a plastic material as a base material, a plastic material with extremely low temperature dependency of the refractive index can be obtained. For example, by dispersing fine particles of niobium oxide (Nb 2 O 5 ) in an acrylic resin, a change in refractive index due to a temperature change can be reduced.
　撮像光学系１においては、比較的屈折力の大きな正レンズ（例えば第１レンズＬ１）又はすべてのレンズに、このような無機粒子を分散させたプラスチック材料を用いることにより、撮像光学系１の温度変化時の像点位置変動を小さく抑えることが可能となる。 In the imaging optical system 1, the temperature of the imaging optical system 1 is obtained by using a plastic material in which such inorganic particles are dispersed in a positive lens (for example, the first lens L1) having a relatively large refractive power or all the lenses. It is possible to suppress the image point position fluctuation at the time of change to be small.
　ところで、本実施形態においては、望ましい形態として撮像光学系１は次の条件式（１）を満たすように構成されている。
　０．１＜ｆｇ２／ｆ＜２　　　　（１）
但し、ｆｇ２は第２レンズ群ＬＧ２の焦点距離、ｆは撮像光学系１全体の焦点距離である。 By the way, in this embodiment, the imaging optical system 1 is comprised so that the following conditional expression (1) may be satisfy | filled as a desirable form.
0.1 <fg2 / f <2 (1)
Here, fg2 is the focal length of the second lens group LG2, and f is the focal length of the entire imaging optical system 1.
　また、本実施形態においては、撮像光学系１は次の条件式（２）を満たすように構成されている。
　０．１＜ｆ１／ｆｇ２＜２　　　（２）
但し、ｆ１は第１レンズＬ１（最物体側の正レンズ）の焦点距離、ｆｇ２は第２レンズ群ＬＧ２の焦点距離である。 In the present embodiment, the imaging optical system 1 is configured to satisfy the following conditional expression (2).
0.1 <f1 / fg2 <2 (2)
Here, f1 is the focal length of the first lens L1 (the most object side positive lens), and fg2 is the focal length of the second lens group LG2.
　このように条件式（１）、（２）を満足するように構成するのは、撮像光学系１を構成するレンズＬ１～Ｌ５に生じる偏芯（光軸ＡＸと垂直な方向のずれ）を補正する（良好な光学特性を得る）ための調整作業を行い易くするための工夫である。この詳細については、以下に述べる撮像光学系１（光学ユニット１０）の組み立て方法の中で説明する。 The reason why the conditional expressions (1) and (2) are satisfied in this way is to correct the eccentricity (deviation in the direction perpendicular to the optical axis AX) generated in the lenses L1 to L5 constituting the imaging optical system 1. This is a device for facilitating the adjustment work for obtaining (obtaining good optical characteristics). Details of this will be described in a method for assembling the imaging optical system 1 (optical unit 10) described below.
（撮像光学系の組み立て方法）
　次に、本発明の光学調整方法を含む、撮像光学系１（光学ユニット１０）の組み立て方法について詳細に説明する。図４は、本実施形態の撮像光学系の組み立て手順を示すフローチャートである。以下、この図４を参照しながら撮像光学系１の組み立てについて説明する。 (Assembly method of imaging optical system)
Next, a method for assembling the imaging optical system 1 (optical unit 10) including the optical adjustment method of the present invention will be described in detail. FIG. 4 is a flowchart showing an assembling procedure of the imaging optical system of the present embodiment. Hereinafter, assembly of the imaging optical system 1 will be described with reference to FIG.
　まず、１群ユニットＧ１の組み立てが行われる（ステップＳ１）。詳細には、第２レンズＬ２及び第２の遮光板１２が、この順番で第１のレンズホルダー１３に組み込まれる。この際、第２のレンズＬ２は第１のレンズホルダー１３に接着固定される。なお、この段階では、第１レンズＬ１及び第１の遮光板１１は、第１のレンズホルダー１３には組み込まれない。 First, the first group unit G1 is assembled (step S1). Specifically, the second lens L2 and the second light shielding plate 12 are incorporated in the first lens holder 13 in this order. At this time, the second lens L2 is bonded and fixed to the first lens holder 13. At this stage, the first lens L1 and the first light shielding plate 11 are not incorporated into the first lens holder 13.
　次に、２群ユニットＧ２の組み立てが行われる（ステップＳ２）。詳細には、第４レンズＬ４、第３の遮光板２１、及び第３レンズＬ３が、この順番で第２のレンズホルダー２２に組み込まれる。この際、第３レンズＬ３と第２のレンズホルダー２２との間に接着剤８０を塗付することにより、第４レンズＬ４、第３の遮光板２１、及び第３レンズＬ３がまとめて第２のレンズホルダー２２に固定される。 Next, the second group unit G2 is assembled (step S2). Specifically, the fourth lens L4, the third light shielding plate 21, and the third lens L3 are incorporated in the second lens holder 22 in this order. At this time, by applying an adhesive 80 between the third lens L3 and the second lens holder 22, the fourth lens L4, the third light-shielding plate 21, and the third lens L3 are collectively put into the second lens L3. The lens holder 22 is fixed.
　次に、３群ユニットＧ３の組み立てが行われる（ステップＳ３）。詳細には、第５レンズＬ５及びフィルタ部材４２が第１のフレーム４１に組み込まれる。第５レンズＬ５とフィルタ部材４２とは別々の方向（例えば図３において、上からと下からが該当）から第１のフレーム４１に組み込まれる。これら組み込まれた部材は、それぞれ第１のフレーム４１に接着剤８０にて接着固定される。 Next, the third group unit G3 is assembled (step S3). Specifically, the fifth lens L5 and the filter member 42 are incorporated in the first frame 41. The fifth lens L5 and the filter member 42 are assembled into the first frame 41 from different directions (for example, from the top and bottom in FIG. 3). These incorporated members are each bonded and fixed to the first frame 41 with an adhesive 80.
　次に、アクチュエータユニットＡ１の組み立てが行われる（ステップＳ４）。詳細には、ＳＩＤＭ軸３１ａの一端と圧電素子３１ｂの一端の接着固定、圧電素子３１ｂの他端と錘３１ｃの一端との接着固定が行われ、これによりＳＩＤＭアクチュエータ３１が形成される。圧電素子３１ｂに設けられる一対の電極のそれぞれにリード線３２の一端が半田付けされ、また、各リード線３２の他端に端子３３が半田付けされる。 Next, the assembly of the actuator unit A1 is performed (step S4). Specifically, one end of the SIDM shaft 31a and one end of the piezoelectric element 31b are bonded and fixed, and the other end of the piezoelectric element 31b and one end of the weight 31c are bonded and thereby the SIDM actuator 31 is formed. One end of a lead wire 32 is soldered to each of a pair of electrodes provided on the piezoelectric element 31 b, and a terminal 33 is soldered to the other end of each lead wire 32.
　なお、ステップＳ１～Ｓ４の組み立て工程は、ここで示した順序に限られる趣旨ではなく、異なる順番で行ってもよいし、ステップＳ１～Ｓ４は同時に並行して行われるようにしてもよい。 Note that the assembly process of steps S1 to S4 is not limited to the order shown here, and may be performed in a different order, or steps S1 to S4 may be performed simultaneously in parallel.
　次に、アクチュエータユニットＡ１が３群ユニットＧ３に取り付けられる（ステップＳ５）。詳細には、第１のフレーム４１に搭載される第５レンズＬ５の周囲を囲むようにリード線３２が這い回され、端子３２が第１のフレーム４１の所定の箇所（図１参照）にクリップ方式で略固定される。なお、この時点では、ＳＩＤＭアクチュエータ３１は、第１のフレーム４１のアクチュエータ支持部４１ｂ（平面視略矩形状に設けられる第１のフレーム４１の４つの角部のうちの１つの近傍に設けられる）に、その軸方向が光軸ＡＸと略平行となるように立てられた状態で配置されるが、未だ固定はされない。 Next, the actuator unit A1 is attached to the third group unit G3 (step S5). Specifically, the lead wire 32 is wound around the fifth lens L5 mounted on the first frame 41, and the terminal 32 is clipped to a predetermined position (see FIG. 1) of the first frame 41. It is almost fixed by the method. At this point, the SIDM actuator 31 is provided in the vicinity of one of the four corners of the first frame 41 provided in a substantially rectangular shape in plan view. However, it is not fixed yet, although it is arranged so that its axial direction is substantially parallel to the optical axis AX.
　次に、２群ユニットＧ２がアクチュエータユニットＡ１に係合される（ステップＳ６）。詳細には、２群ユニットＧ２は、それを構成する第２のレンズホルダー２２の１つの角部付近（アクチュエータ支持部４１ｂの略上方にある角部近傍）と、略Ｌ字状に設けられる板バネ部材２３の一辺の先端部とで、ＳＩＤＭ軸３２ａを挟むように配置される。ここで、板バネ部材２３は、その略中央部に当る略Ｌ字状の屈曲点が第２のレンズホルダー２２に設けられるボス２２ｂ（図２参照）に揺動可能に取り付けられとともに、略Ｌ字の他辺の先端部が第２のレンズホルダー２２に当接するように取り付けられる。これにより、２群ユニットＧ２は、ＳＩＤＭ軸３１ａに所定の摩擦力で係合され、その軸方向に移動可能な状態となる。 Next, the second group unit G2 is engaged with the actuator unit A1 (step S6). Specifically, the second group unit G2 is provided in the vicinity of one corner of the second lens holder 22 constituting the second group unit G2 (in the vicinity of the corner substantially above the actuator support portion 41b) and a plate provided in a substantially L shape. The spring member 23 is arranged so as to sandwich the SIDM shaft 32a with the tip of one side. Here, the leaf spring member 23 is attached to a boss 22b (see FIG. 2) provided on the second lens holder 22 so that a substantially L-shaped bending point corresponding to a substantially central portion of the leaf spring member 23 can swing. The tip of the other side of the character is attached so as to abut on the second lens holder 22. Thus, the second group unit G2 is engaged with the SIDM shaft 31a with a predetermined frictional force and is movable in the axial direction.
　次に、第２のフレーム５０が第１のフレーム４１に取り付けられる（ステップＳ７）。詳細には、箱形状（ただし、上面に光を通過させるための開口５０ａが設けられている）の第２のフレーム５０が、アクチュエータユニットＡ１及び２群ユニットＧ２に被せられるような姿勢とされて第１のフレーム４１に取り付けられる。第１のフレーム４１と第２のフレーム５０との間にはスナップフィット機構が設けられており、接着剤を用いることなく両者の光軸方向の相対位置が固定される。光軸ＡＸと垂直な方向の相対位置は位置決めピンと、それに係合する位置決め穴によって固定される。また、この第２のフレーム５０の取り付けによって、アクチュエータユニットＡ１の端子３３は第１のフレーム４１と第２のフレーム５０との間に挟みこまれて完全に固定される。このステップＳ７の終了時点の状態（第１の状態）を図５（断面図）に示す。 Next, the second frame 50 is attached to the first frame 41 (step S7). Specifically, the second frame 50 having a box shape (however, an opening 50a for allowing light to pass through is provided on the upper surface) is configured to be covered with the actuator unit A1 and the second group unit G2. It is attached to the first frame 41. A snap fit mechanism is provided between the first frame 41 and the second frame 50, and the relative position in the optical axis direction of both is fixed without using an adhesive. The relative position in the direction perpendicular to the optical axis AX is fixed by a positioning pin and a positioning hole engaged therewith. Further, by attaching the second frame 50, the terminal 33 of the actuator unit A1 is sandwiched between the first frame 41 and the second frame 50 and completely fixed. FIG. 5 (cross-sectional view) shows the state (first state) at the end of step S7.
　なお、第２のフレーム５０を第１のフレーム４１に取り付けるにあたって、アクチュエータユニットＡ１のＳＩＤＭ軸３１ａの先端は、第２のフレーム５０の上面に設けられる嵌合孔５０ｂに嵌合した状態とされる。この時点では錘３１ｃの接着固定は行われていない。 When the second frame 50 is attached to the first frame 41, the tip of the SIDM shaft 31a of the actuator unit A1 is fitted in a fitting hole 50b provided on the upper surface of the second frame 50. . At this time, the weight 31c is not bonded and fixed.
　次に、第２レンズ群ＬＧ２（２群ユニットＧ２）の傾きの調整が行われる（ステップＳ８）。詳細には、錘３１ｃの光軸ＡＸと垂直な平面内の位置を調整することによって第２レンズ群ＬＧ２の傾き調整が行われる。更に具体的には、例えば、固体撮像素子７０の撮像面７０ａ（この段階では固体撮像素子７０は取り付けられていないため、取り付けられた場合を想定した話である）と平行となるように配置される基準面と、第３レンズＬ３の有効面より外側のコバ面とが平行となるように、例えばオートコリメータ等を用いて傾き調整が行われる。この傾き調整が行われた段階で、錘３１ｃが接着剤８０にて第１のフレーム４１に接着固定される。 Next, the inclination of the second lens group LG2 (second group unit G2) is adjusted (step S8). Specifically, the inclination of the second lens group LG2 is adjusted by adjusting the position of the weight 31c in a plane perpendicular to the optical axis AX. More specifically, for example, the imaging surface 70a of the solid-state imaging device 70 is arranged in parallel with the imaging surface 70a (the solid-state imaging device 70 is not attached at this stage, and is assumed to be attached). Inclination is adjusted using, for example, an autocollimator or the like so that the reference surface and the edge surface outside the effective surface of the third lens L3 are parallel to each other. At the stage where this tilt adjustment is performed, the weight 31 c is bonded and fixed to the first frame 41 with the adhesive 80.
　次に、１群ユニットＧ１（第１レンズＬ１は組み込まれていない）が第２のフレーム５０に取り付けられる（ステップＳ９）。詳細には、１群ユニットＧ１を構成する第１のレンズホルダー１３の位置を、第２レンズＬ２に施された位置基準マークＭ１と第５レンズＬ５に施された位置基準マークＭ２とが、光軸に垂直な方向にずれることなく一致するように調整した上で、第１のレンズホルダー１３を第２のフレーム５０に接着固定する。このステップＳ９の終了時点の状態（第２の状態）を図６（断面図）に示す。 Next, the first group unit G1 (the first lens L1 is not incorporated) is attached to the second frame 50 (step S9). Specifically, the position of the first lens holder 13 constituting the first group unit G1 is determined by the position reference mark M1 applied to the second lens L2 and the position reference mark M2 applied to the fifth lens L5. The first lens holder 13 is bonded and fixed to the second frame 50 after adjusting so as to match without shifting in the direction perpendicular to the axis. A state (second state) at the end of step S9 is shown in FIG. 6 (cross-sectional view).
　位置基準マークＭ１と位置基準マークＭ２とが一致するように行うレンズ位置調整は、例えば光軸方向に沿って２つのマークＭ１、Ｍ２を同時に観察しながら行ってもよい。また、例えば、２つの位置基準マークＭ１、Ｍ２を光軸方向に沿って別々に観察することによって各マークＭ１、Ｍ２の観察座標系内の位置を別々に得て、得られた座標位置に基づいて両者の位置が一致するように第２レンズＬ５の位置（第１のレンズホルダー１３の位置）を動かすようにしてもよい。 The lens position adjustment performed so that the position reference mark M1 and the position reference mark M2 coincide may be performed, for example, while simultaneously observing the two marks M1 and M2 along the optical axis direction. Also, for example, by observing the two position reference marks M1 and M2 separately along the optical axis direction, the positions of the marks M1 and M2 in the observation coordinate system are obtained separately, and based on the obtained coordinate positions. Then, the position of the second lens L5 (the position of the first lens holder 13) may be moved so that the positions of the two coincide.
　ところで、上述のように、本実施形態の撮像光学系１においては、第１レンズ群ＬＧ１、第２レンズ群ＬＧ２、第３レンズ群ＬＧ３は別々のメカ部品に搭載される構成となっている。このような構成の場合、部品誤差の累積によって、第１レンズ群ＬＧ１と第３レンズ群ＬＧ３との相対的な位置関係に大きなずれ（光軸ＡＸに対して垂直な方向のずれ）が生じ易い。そして、このような位置ずれは、最終的に行われる撮像光学系１の光学調整（固体撮像素子を用いた光学調整）の際に良好な光学特性を得難くする場合がある。このため、部品誤差の累積による上記相対位置のずれは解消することが望まれる。このような理由から、本実施形態においては、位置基準マークＭ１、Ｍ２を用いて第２レンズＬ２と第５レンズＬ５とが正しい相対位置となるようにレンズ位置調整を行っている。 Incidentally, as described above, in the imaging optical system 1 of the present embodiment, the first lens group LG1, the second lens group LG2, and the third lens group LG3 are mounted on separate mechanical components. In the case of such a configuration, a large shift (shift in a direction perpendicular to the optical axis AX) easily occurs in the relative positional relationship between the first lens group LG1 and the third lens group LG3 due to the accumulation of component errors. . Such misalignment may make it difficult to obtain good optical characteristics during the final optical adjustment of the imaging optical system 1 (optical adjustment using a solid-state imaging device). For this reason, it is desirable to eliminate the shift of the relative position due to the accumulation of component errors. For this reason, in this embodiment, lens position adjustment is performed using the position reference marks M1 and M2 so that the second lens L2 and the fifth lens L5 are in the correct relative positions.
　ここで、第２レンズＬ２と第５レンズＬ５との間に第２レンズ群ＬＧ２が存在するような本実施形態の構成の場合には、第２レンズ群ＬＧ２が偏芯していると、第２レンズ群ＬＧ２を介して観察される位置基準マークＭ２の像（本実施形態では虚像であるが、異なる構成では実像となることもある）が本来の位置から大きくずれて観察される場合がある。そして、このような状態で位置基準マークＭ１、Ｍ２を用いたレンズ位置調整を行っても、レンズを正しい相対位置とはできない。このため、本実施形態では、第２レンズ群ＬＧ２が偏芯状態にあっても、その影響をほとんど受けることがないように、撮像光学系１が条件式（１）を満足するように構成しているのである。
　０．１＜ｆｇ２／ｆ＜２　　　　（１）
但し、ｆｇ２は第２レンズ群ＬＧ２の焦点距離、ｆは撮像光学系１全体の焦点距離である。 Here, in the configuration of the present embodiment in which the second lens group LG2 exists between the second lens L2 and the fifth lens L5, if the second lens group LG2 is decentered, An image of the position reference mark M2 observed through the two lens group LG2 (a virtual image in the present embodiment, but may be a real image in a different configuration) may be observed with a large deviation from the original position. . In such a state, even if the lens position adjustment using the position reference marks M1 and M2 is performed, the lens cannot be in the correct relative position. Therefore, in the present embodiment, the imaging optical system 1 is configured to satisfy the conditional expression (1) so that the second lens group LG2 is hardly affected even when the second lens group LG2 is in an eccentric state. -ing
0.1 <fg2 / f <2 (1)
Here, fg2 is the focal length of the second lens group LG2, and f is the focal length of the entire imaging optical system 1.
　詳細には、条件式（１）の下限を上回るように構成することで、第２レンズ群ＬＧ２の屈折力が強くなり過ぎず、上述した、第２レンズ群ＬＧ２の偏芯によって生じる位置基準マークＭ２の像ずれを小さく抑えることができるようにしている。なお、条件式（１）の上限を下回るように構成しているのは、第２レンズ群ＬＧ２の屈折力は弱くなり過ぎることなく適度に維持することで、撮像光学系１の全長の短縮化を図る趣旨である。 Specifically, by configuring so as to exceed the lower limit of conditional expression (1), the refractive power of the second lens group LG2 does not become too strong, and the above-described position reference mark caused by the eccentricity of the second lens group LG2 The image shift of M2 can be suppressed small. The reason why the lower limit of the conditional expression (1) is satisfied is that the refractive power of the second lens group LG2 is appropriately maintained without becoming too weak, thereby shortening the total length of the imaging optical system 1. This is the purpose.
　また、撮像光学系１は以下の条件式（１）´を満足するように構成するのが、より好ましい。
　０．５＜ｆｇ２／ｆ＜１．５　　　（１）´ The imaging optical system 1 is more preferably configured to satisfy the following conditional expression (1) ′.
0.5 <fg2 / f <1.5 (1) ′
　図４に戻って、ステップＳ９が完了すると、第１レンズＬ１（最物体側に配置される正レンズ）が第１のレンズホルダー１３に固定される（ステップＳ１０）。なお、第１レンズＬ１は、第１のレンズホルダー１３に固定される前に光軸ＡＸと垂直な方向に動かされて、光学調整のためにその位置が調整される（調芯工程）。以下、この調芯工程について、図７を参照しながら説明する。図７は、本実施形態の撮像光学系の組み立て途中の状態を示す概略断面図で、第１レンズの調芯工程を説明するための図である。 Referring back to FIG. 4, when step S9 is completed, the first lens L1 (positive lens arranged on the most object side) is fixed to the first lens holder 13 (step S10). The first lens L1 is moved in a direction perpendicular to the optical axis AX before being fixed to the first lens holder 13, and its position is adjusted for optical adjustment (alignment process). Hereinafter, this alignment step will be described with reference to FIG. FIG. 7 is a schematic cross-sectional view showing a state during the assembly of the imaging optical system of the present embodiment, and is a view for explaining the alignment process of the first lens.
　調芯工程に先立って、図７に示すように、第１のフレーム４１の背後に固体撮像素子７０が配置される。この固体撮像素子７０は、光学調整用に準備された調整用のものでもよいし、製品として用いられるものでもよい。製品として用いられるものである場合には、この段階で、固体撮像素子７０を第１のフレーム４１に固着してもよい。 Prior to the alignment step, as shown in FIG. 7, the solid-state imaging device 70 is disposed behind the first frame 41. The solid-state imaging device 70 may be an adjustment device prepared for optical adjustment or may be used as a product. When used as a product, the solid-state image sensor 70 may be fixed to the first frame 41 at this stage.
　固体撮像素子７０を配置すると、治具に保持された第１レンズＬ１が、第２レンズＬ２及び第２の遮光板１２が組み込まれた第１のレンズホルダー１３のレンズ保持空間１３ａ（図２参照）内に、先に組み込まれている部材に押し付けられるように挿入される。そして、固体撮像素子７０によって得られる光学特性を監視しながら、第１レンズＬ１を光軸ＡＸと垂直な方向に動かし、好ましい光学特性が得られるように調芯が行なわれる。好ましい光学特性を得られる位置を見つけたら、紫外線照射により接着剤８０を硬化して、第１レンズＬ１の第１のレンズホルダー１３内への固定が行われる。 When the solid-state imaging device 70 is disposed, the lens holding space 13a of the first lens holder 13 in which the first lens L1 held by the jig is incorporated with the second lens L2 and the second light shielding plate 12 (see FIG. 2). ) To be pressed against the previously incorporated member. Then, while monitoring the optical characteristics obtained by the solid-state imaging device 70, the first lens L1 is moved in a direction perpendicular to the optical axis AX, and alignment is performed so that preferable optical characteristics are obtained. When a position where favorable optical characteristics can be obtained is found, the adhesive 80 is cured by ultraviolet irradiation, and the first lens L1 is fixed in the first lens holder 13.
　ここで、図８を参照して、第１のレンズホルダー１３の構成について追加説明しておく。なお、図８は、本実施形態の第１のレンズホルダーを上から見た場合の概略平面図で、第１レンズがホルダー内（レンズ保持空間１３ａ（図２参照））に挿入された状態を示している。 Here, the configuration of the first lens holder 13 will be additionally described with reference to FIG. FIG. 8 is a schematic plan view of the first lens holder according to the present embodiment as viewed from above. The first lens is inserted into the holder (lens holding space 13a (see FIG. 2)). Show.
　図８に示すように、第１のレンズホルダー１３の外周側には、第１レンズＬ１を側面から接着するための接着剤を充填する接着剤充填部１３ｃが円周方向に等間隔で３箇所設けられている。また、接着剤充填部１３ｃを挟むように、空間部１３ｄが円周方向に等間隔で３箇所設けられている。すなわち、接着剤充填部１３ｃと空間部１３ｄとは円周方向に交互に配置されている。この空間部１３ｄにより、レンズ保持空間１３ａ内に挿入された第１レンズＬ１の治具による保持が可能となっている。治具は例えば、３本の爪状部材で構成され、空間部１３ｄに挿入された爪状部材が第１レンズＬ１を挟むように構成される。また、レンズ保持空間１３ａの直径（光軸ＡＸと垂直な方向のサイズ）は、第１レンズＬ１の直径より大き目に形成されている。このために、レンズ保持空間１３ａ内に第１レンズＬ１を挿入した状態で隙間ＳＰが形成され、治具により保持された第１レンズＬ１が、第１レンズＬ１の光軸ＡＸと垂直な方向へ移動可能となっている。 As shown in FIG. 8, on the outer peripheral side of the first lens holder 13, there are three adhesive filling portions 13c filled with an adhesive for adhering the first lens L1 from the side surface at equal intervals in the circumferential direction. Is provided. Further, three space portions 13d are provided at equal intervals in the circumferential direction so as to sandwich the adhesive filling portion 13c. That is, the adhesive filling portions 13c and the space portions 13d are alternately arranged in the circumferential direction. By this space portion 13d, the first lens L1 inserted into the lens holding space 13a can be held by a jig. The jig is composed of, for example, three claw-shaped members, and is configured such that the claw-shaped member inserted into the space portion 13d sandwiches the first lens L1. The diameter of the lens holding space 13a (size in the direction perpendicular to the optical axis AX) is larger than the diameter of the first lens L1. Therefore, a gap SP is formed in a state where the first lens L1 is inserted into the lens holding space 13a, and the first lens L1 held by the jig is in a direction perpendicular to the optical axis AX of the first lens L1. It is movable.
　ところで、上述のように、本実施形態の撮像光学系１ではインナーフォーカス方式を採用している。インナーフォーカス方式は撮像光学系１の低背化に有利な方式であるが、フォーカス調整のために光軸方向に移動する機構を有することになるためにメカ部品が増加し、レンズの中心位置が光軸と垂直な方向にずれる偏芯が生じ易い。そして、小型化・高性能化の要求を満たすように構成される撮像光学系においては、製造時に発生した偏芯による悪影響（例えば片ボケや軸上コマ収差）を受け易いといった問題がある。このため、撮像光学系１の組み立て時に、偏芯の影響を補正すべく調芯（光学調整）を行うようにしている。なお、上記レンズ位置調整（ステップＳ９参照）によってレンズの相対配置の補正は行っているが、それだけでは必ずしも万全とは言えず、安定した品質を得るために調芯を行う必要がある。逆に、ステップＳ９のレンズ位置調整は場合によっては行わないこととしても良いが、調芯を行い易くするために行うのが好ましい。 Incidentally, as described above, the imaging optical system 1 of the present embodiment employs the inner focus method. The inner focus method is an advantageous method for reducing the height of the imaging optical system 1. However, since it has a mechanism that moves in the optical axis direction for focus adjustment, the number of mechanical parts is increased, and the center position of the lens is increased. Eccentricity that shifts in a direction perpendicular to the optical axis is likely to occur. An imaging optical system configured to satisfy the demands for miniaturization and high performance is susceptible to adverse effects (eg, one-sided blur and axial coma) caused by eccentricity that occurs during manufacturing. For this reason, when the imaging optical system 1 is assembled, alignment (optical adjustment) is performed in order to correct the influence of eccentricity. Although the correction of the relative arrangement of the lenses is performed by the lens position adjustment (see step S9), it is not always perfect, and alignment is necessary to obtain stable quality. Conversely, the lens position adjustment in step S9 may not be performed depending on circumstances, but is preferably performed to facilitate alignment.
　調芯は複数のレンズを移動させて行うことも可能であるが、効率良く調芯を行うために、本実施形態では第１レンズＬ１（最物体側に配置される正レンズ）のみを移動させる構成としている。そして、調芯を正確且つ効率良く行えること等を考慮して、撮像光学系１が条件式（２）を満足するように構成しているのである。
　０．１＜ｆ１／ｆｇ２＜２　　　（２）
但し、ｆ１は第１レンズＬ１（最物体側の正レンズ）の焦点距離、ｆｇ２は第２レンズ群ＬＧ２の焦点距離である。 Although alignment can be performed by moving a plurality of lenses, in order to perform alignment efficiently, only the first lens L1 (positive lens arranged on the most object side) is moved in this embodiment. It is configured. In consideration of the fact that alignment can be performed accurately and efficiently, the imaging optical system 1 is configured to satisfy the conditional expression (2).
0.1 <f1 / fg2 <2 (2)
Here, f1 is the focal length of the first lens L1 (the most object side positive lens), and fg2 is the focal length of the second lens group LG2.
　詳細には、条件式（２）の下限を上回るように構成することで、第２レンズ群ＬＧ２に対する第１レンズＬ１の焦点距離が短くなりすぎるのを防止している。これにより、第１レンズＬ１の移動（調芯のための移動）に対する光学性能の変化の感度が大きくなりすぎて、調整精度が低下するのを防止可能となっている。また、条件式（２）の上限を下回ることで、第２レンズ群ＬＧ２に対する第１レンズＬ１の焦点が長くなりすぎるのを防止している。これにより、第２レンズ群ＬＧ２の偏芯を補正するため（調芯のため）に第１レンズＬ１を動かす量が大きくなりすぎるのを防止でき、調整作業を素早く行える。また、条件式（２）の上限を下回るようにすることで、撮像光学系１がレンズの径方向（光軸方向と垂直な方向）に大型化することも抑制可能となっている。 More specifically, the focal length of the first lens L1 with respect to the second lens group LG2 is prevented from becoming too short by configuring so as to exceed the lower limit of the conditional expression (2). Thereby, it is possible to prevent the adjustment accuracy from deteriorating due to the sensitivity of the change in the optical performance with respect to the movement of the first lens L1 (movement for alignment). Further, by falling below the upper limit of conditional expression (2), the focal point of the first lens L1 with respect to the second lens group LG2 is prevented from becoming too long. As a result, it is possible to prevent the amount of movement of the first lens L1 from being too large in order to correct the eccentricity of the second lens group LG2 (for alignment), and the adjustment operation can be performed quickly. Further, by making the value lower than the upper limit of the conditional expression (2), it is possible to prevent the imaging optical system 1 from becoming large in the lens radial direction (direction perpendicular to the optical axis direction).
　また、撮像光学系１は以下の条件式（２）´を満足するように構成するのが、より好ましい。
　０．５＜ｆ１／ｆｇ２＜１．８　　　（２）´ The imaging optical system 1 is more preferably configured to satisfy the following conditional expression (2) ′.
0.5 <f1 / fg2 <1.8 (2) ′
　なお、この第１レンズＬ１の取り付けの際（調芯工程を行う際）に、第１レンズＬ１の光軸方向の位置調整を併せて行ってもよい。これにより、片ボケのみならず、像面湾曲についても性能向上を図ることが可能である。また、第１レンズＬ１を取り付けた後に（調芯工程後に）、第１のレンズホルダー１３（すなわち、第１レンズ群ＬＧ１）を光軸方向に移動して、片ボケのみならず、像面湾曲の向上を図るようにしてもよい。なお、この場合には、ステップＳ９において、第１のレンズホルダー１３の接着固定は行わないようにし、第１のレンズホルダー１３を調整治具で保持した状態のままとする必要がある。 In addition, when the first lens L1 is attached (when the alignment process is performed), the position adjustment of the first lens L1 in the optical axis direction may be performed together. Thereby, it is possible to improve performance not only for one-sided blur but also for field curvature. In addition, after the first lens L1 is attached (after the alignment process), the first lens holder 13 (that is, the first lens group LG1) is moved in the optical axis direction, so that not only one-side blur but also field curvature You may make it aim at improvement. In this case, in step S9, the first lens holder 13 is not bonded and fixed, and the first lens holder 13 needs to be held by the adjustment jig.
　また、撮像光学系１は以下の条件式（３）を満足するように構成するのが好ましく、更には以下の条件式（３）´を満足するように構成するのがより好ましい。
　１．０＜ｆｇ１／ｆ＜３．０　　（３）
　１．３＜ｆｇ１／ｆ＜２．５　　（３）´
但し、ｆｇ１は第１レンズ群ＬＧ１の焦点距離、ｆは撮像光学系１全体の焦点距離である。 The imaging optical system 1 is preferably configured to satisfy the following conditional expression (3), and more preferably configured to satisfy the following conditional expression (3) ′.
1.0 <fg1 / f <3.0 (3)
1.3 <fg1 / f <2.5 (3) ′
Here, fg1 is the focal length of the first lens group LG1, and f is the focal length of the entire imaging optical system 1.
　条件式（３）（好ましくは条件式（３）´）を満足するように撮像光学系１を構成することにより、第１レンズ群ＬＧ１の焦点距離が適切となり、低背化と高性能化の実現が可能となる。詳細には、条件式（３）（好ましくは条件式（３）´）の上限を下回るように構成することで、第１レンズ群ＬＧ１の焦点距離を適度に維持することができるために、撮像光学系１の主点位置をより物体側に配置することができ、撮像光学系１の全長を短くすることができる。また、条件式（３）（好ましくは条件式（３）´）の下限を上回るように構成することで、第１レンズ群ＬＧ１の焦点距離が必要以上に小さくなり過ぎず、第１レンズ群ＬＧ１で発生する高次の球面収差やコマ収差を小さく抑えることができる。 By configuring the imaging optical system 1 so as to satisfy the conditional expression (3) (preferably conditional expression (3) ′), the focal length of the first lens group LG1 becomes appropriate, and a reduction in height and performance is achieved. Realization is possible. Specifically, since the focal length of the first lens group LG1 can be appropriately maintained by configuring the conditional expression (3) (preferably conditional expression (3) ′) to be lower than the upper limit, imaging is performed. The principal point position of the optical system 1 can be arranged closer to the object side, and the overall length of the imaging optical system 1 can be shortened. Further, by configuring so as to exceed the lower limit of conditional expression (3) (preferably conditional expression (3) ′), the focal length of the first lens group LG1 does not become unnecessarily small, and the first lens group LG1. Higher order spherical aberration and coma can be suppressed.
　再び図４に戻って、ステップＳ１０が完了すると、第１の遮光板１１が第１レンズＬ１に貼り付けられる。また、電磁波漏れ対策等を兼ねてカバー６０が第１のフレーム４１に上から被せられる（以上ステップＳ１１）。カバー６０と第１のフレーム４１との間にはスナップフィット機構が設けられており、カバー６０は接着固定されることなく第１のフレーム４１に取り付けられる。 Returning to FIG. 4 again, when step S10 is completed, the first light shielding plate 11 is attached to the first lens L1. Further, the cover 60 is placed on the first frame 41 from above to serve also as a countermeasure for electromagnetic wave leakage (step S11). A snap-fit mechanism is provided between the cover 60 and the first frame 41, and the cover 60 is attached to the first frame 41 without being bonded and fixed.
　以上により、本実施形態の撮像光学系１（光学ユニット１０）が得られる。次に、撮像光学系１の好適な実施例について示す。 Thus, the imaging optical system 1 (optical unit 10) of the present embodiment is obtained. Next, a preferred embodiment of the imaging optical system 1 will be described.
　（実施例）
　以下、撮像光学系１の好適な実施例について、コンストラクションデータ等を挙げて具体的に説明する。実施例１～１０（ＥＸ１～１０）の撮像光学系の構成（レンズ構成）について、図９～図１８に示す。図９～図１８は、撮像光学系１が無限遠合焦状態にある場合の光学断面図である。また、無限遠から最近接距離へのフォーカシングにおけるフォーカス群（第２レンズ群ＬＧ２）の移動を、矢印ｍＦで示している。 (Example)
Hereinafter, a preferred embodiment of the imaging optical system 1 will be specifically described with reference to construction data and the like. FIGS. 9 to 18 show the configuration (lens configuration) of the imaging optical system of Examples 1 to 10 (EX1 to 10). 9 to 18 are optical cross-sectional views when the imaging optical system 1 is in an infinitely focused state. Further, the movement of the focus group (second lens group LG2) during focusing from infinity to the closest distance is indicated by an arrow mF.
　なお、実施例１～１０については第２レンズＬ２に位置基準マークＭ１が、実施例１～５、８、１０（レンズ枚数５枚）については第５レンズＬ５に位置基準マークＭ２が、実施例６、７、９（レンズ枚数４枚）については第４レンズＬ４に位置基準マークＭ２が、レンズ表面に施されるが、これらのマークは光学性能への影響がほぼ無視できるように設けられるものであるために、レンズの構成についてマークの存在は考慮に入れていない。 In Examples 1 to 10, the position reference mark M1 is provided on the second lens L2, and in Examples 1 to 5, 8, and 10 (5 lenses), the position reference mark M2 is provided on the fifth lens L5. For 6, 7, and 9 (four lenses), the fourth lens L4 is provided with a position reference mark M2 on the lens surface. These marks are provided so that the influence on the optical performance can be almost ignored. Therefore, the presence of the mark is not taken into consideration for the lens configuration.
　各実施例のコンストラクションデータでは、面データとして、左側の欄から順に、面番号，曲率半径ｒ（ｍｍ），軸上面間隔ｄ（ｍｍ），フォーカス時の可変間隔に関しては最近接物体距離時（物体距離：１０ｃｍ）の軸上面間隔ｄｍ（ｍｍ），ｄ線（波長：５８７．５６ｎｍ）に関する屈折率ｎｄ，ｄ線に関するアッベ数ｖｄ，有効半径（ｍｍ）を示す。面番号に＊が付された面は非球面であり、その面形状は面頂点を原点とするローカルな直交座標系（Ｘ，Ｙ，Ｚ）を用いた以下の式(AS)で定義される。非球面データとして、非球面係数等を示す。なお、各実施例の非球面データにおいて表記の無い項の係数は０であり、すべてのデータに関してＥ－ｎ＝×１０-nである。 In the construction data of each embodiment, as surface data, in order from the left column, the surface number, the radius of curvature r (mm), the shaft upper surface distance d (mm), and the variable distance at the time of focusing are the closest object distance (object The distance between axis top surfaces dm (mm) at a distance of 10 cm, the refractive index nd for the d line (wavelength: 587.56 nm), the Abbe number vd for the d line, and the effective radius (mm) are shown. The surface with * in the surface number is an aspherical surface, and the surface shape is defined by the following formula (AS) using a local orthogonal coordinate system (X, Y, Z) with the surface vertex as the origin. . As aspheric data, an aspheric coefficient or the like is shown. It should be noted that the coefficient of the term not described in the aspherical data of each embodiment is 0, and En = × 10 −n for all data.
Figure JPOXMLDOC01-appb-M000001
 　…(AS)
Figure JPOXMLDOC01-appb-M000001
 … (AS)
　ただし、
ｈ：Ｘ軸（光軸ＡＸ）に対して垂直な方向の高さ（ｈ2＝Ｙ2＋Ｚ2）、
Ｘ：高さｈの位置での光軸ＡＸ方向のサグ量（面頂点基準）、
Ｒ：基準曲率半径（曲率半径ｒに相当する。）、
Ｋ：円錐定数、
Ａｉ：ｉ次の非球面係数、
である。 However,
h: height in the direction perpendicular to the X axis (optical axis AX) (h 2 = Y 2 + Z 2 ),
X: sag amount in the direction of the optical axis AX at the position of height h (based on the surface vertex),
R: Reference radius of curvature (corresponding to the radius of curvature r),
K: conic constant,
Ai: i-th order aspheric coefficient,
It is.
　各種データとして、全系（光学系全体）の焦点距離（ｆ，ｍｍ），Ｆナンバー（Ｆｎｏ．），半画角（ω，°），固体撮像素子の撮像面７０ａの対角線長（２Ｙ’，ｍｍ；Ｙ’：最大像高），バックフォーカス（ｆＢ，ｍｍ），入射瞳位置（ＥＮＴＰ，第１面から入射瞳位置までの距離，ｍｍ），射出瞳位置（ＥＸＴＰ，撮像面７０ａから射出瞳位置までの距離，ｍｍ），前側主点位置（Ｈ１，第１面から前側主点位置までの距離，ｍｍ），後側主点位置（Ｈ２，最終面から後側主点位置までの距離，ｍｍ）を示す。全系の焦点距離及びＦナンバーについては、無限遠物体距離時（物体距離：∞）と最近接物体距離時（物体距離：１０ｃｍ）の両方のフォーカス状態での値を示している。バックフォーカスｆＢは、平行平板ＰＴ（フィルタ部材４２に同じ）の像側面から像面ＩＭ（撮像面７０ａに同じ）までの距離を表すものとする。さらに、単レンズデータ及びレンズ群データとして各レンズと各レンズ群の焦点距離を示す。また、各条件式（条件式（１）、（２）、（３））に対応する実施例の値を表１に示す。 As various data, the focal length (f, mm), F number (Fno.), Half angle of view (ω, °) of the entire system (whole optical system), diagonal length (2Y ′, mm; Y ′: maximum image height), back focus (fB, mm), entrance pupil position (ENTP, distance from first surface to entrance pupil position, mm), exit pupil position (EXTP, exit pupil from imaging surface 70a) Distance to position, mm), front principal point position (H1, distance from first surface to front principal point position, mm), rear principal point position (H2, distance from final surface to rear principal point position, mm). Regarding the focal length and F number of the entire system, values in both the focus state at the infinity object distance (object distance: ∞) and the closest object distance (object distance: 10 cm) are shown. The back focus fB represents the distance from the image side surface of the parallel plate PT (same as the filter member 42) to the image plane IM (same as the imaging surface 70a). Furthermore, the focal length of each lens and each lens group is shown as single lens data and lens group data. Table 1 shows values of the examples corresponding to the respective conditional expressions (conditional expressions (1), (2), and (3)).
　図１９～図２８は、実施例１～１０（ＥＸ１～１０）の無限遠物体距離時（物体距離：∞）の収差図である。図１９～図２８のそれぞれにおいて、（Ａ）は球面収差図、（Ｂ）は非点収差図、（Ｃ）は歪曲収差図である。球面収差図は、実線で示すｄ線（波長５８７．５６ｎｍ）に対する球面収差量、破線で示すｇ線（波長４３５．８４ｎｍ）に対する球面収差量を、それぞれ近軸像面からの光軸ＡＸ方向のズレ量（単位：ｍｍ）で表しており、縦軸は瞳への入射高さをその最大高さで規格化した値（すなわち相対瞳高さ）を表している。非点収差図において、破線Ｔはｄ線に対するタンジェンシャル像面、実線Ｓはｄ線に対するサジタル像面を、近軸像面からの光軸ＡＸ方向のズレ量（単位：ｍｍ）で表しており、縦軸は像高（ＩＭＧ　ＨＴ，単位：ｍｍ）を表している。歪曲収差図において、横軸はｄ線に対する歪曲（単位：％）を表しており、縦軸は像高（ＩＭＧ　ＨＴ，単位：ｍｍ）を表している。なお、像高ＩＭＧ　ＨＴの最大値は、像面ＩＭにおける最大像高Ｙ’（固体撮像素子７０の撮像面７０ａの対角長の半分）に相当する。 19 to 28 are aberration diagrams of Examples 1 to 10 (EX1 to 10) at an infinite object distance (object distance: ∞). In each of FIGS. 19 to 28, (A) is a spherical aberration diagram, (B) is an astigmatism diagram, and (C) is a distortion aberration diagram. The spherical aberration diagram shows the amount of spherical aberration for the d-line (wavelength 587.56 nm) indicated by the solid line and the amount of spherical aberration for the g-line (wavelength 435.84 nm) indicated by the broken line in the optical axis AX direction from the paraxial image plane. The amount of deviation (unit: mm) is represented, and the vertical axis represents a value obtained by normalizing the incident height to the pupil by the maximum height (that is, relative pupil height). In the astigmatism diagram, the broken line T represents the tangential image surface with respect to the d line, and the solid line S represents the sagittal image surface with respect to the d line, expressed as a deviation amount (unit: mm) in the optical axis AX direction from the paraxial image surface. The vertical axis represents the image height (IMG HT, unit: mm). In the distortion diagram, the horizontal axis represents distortion (unit:%) with respect to the d-line, and the vertical axis represents image height (IMG HT, unit: mm). The maximum value of the image height IMG HT corresponds to the maximum image height Y ′ on the image plane IM (half the diagonal length of the imaging surface 70a of the solid-state imaging device 70).
　実施例１の撮像光学系１（図９参照）は、物体側から順に、正の第１レンズＬ１と、開口絞りＳＴと、負の第２レンズＬ２と、正の第３レンズＬ３と、正の第４レンズＬ４と、負の第５レンズＬ５と、から構成されており、レンズ面は全て非球面である。近軸の面形状で各レンズを見た場合、第１レンズＬ１は両凸の正レンズであり、第２レンズＬ２は像側に凹の負メニスカスレンズであり、第３レンズＬ３は物体側に凸の正メニスカスレンズであり、第４レンズＬ４は像側に凸の正メニスカスレンズであり、第５レンズＬ５は像側に凹の負メニスカスレンズである。なお、第１レンズＬ１及び第２レンズＬ２が全体として正の屈折力を有する第１レンズ群ＬＧ１を、第３レンズＬ３及び第４レンズＬ４が全体として正の屈折力を有する第２レンズ群ＬＧ２を、第５レンズＬ５が全体として負の屈折力を有する第３レンズ群ＬＧ３を構成している。 The imaging optical system 1 of Embodiment 1 (see FIG. 9) includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a positive third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When each lens is viewed with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is on the object side. The fourth lens L4 is a positive meniscus lens convex to the image side, and the fifth lens L5 is a negative meniscus lens concave to the image side. In addition, the first lens L1 and the second lens L2 have a positive refractive power as a whole, the first lens group LG1, and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole, a second lens group LG2. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
　実施例２の撮像光学系１（図１０参照）は、物体側から順に、正の第１レンズＬ１と、開口絞りＳＴと、負の第２レンズＬ２と、正の第３レンズＬ３と、正の第４レンズＬ４と、負の第５レンズＬ５と、から構成されており、レンズ面は全て非球面である。近軸の面形状で各レンズを見た場合、第１レンズＬ１は両凸の正レンズであり、第２レンズＬ２は像側に凹の負メニスカスレンズであり、第３レンズＬ３は物体側に凸の正メニスカスレンズであり、第４レンズＬ４は像側に凸の正メニスカスレンズであり、第５レンズＬ５は像側に凹の負メニスカスレンズである。なお、第１レンズＬ１及び第２レンズＬ２が全体として正の屈折力を有する第１レンズ群ＬＧ１を、第３レンズＬ３及び第４レンズＬ４が全体として正の屈折力を有する第２レンズ群ＬＧ２を、第５レンズＬ５が全体として負の屈折力を有する第３レンズ群ＬＧ３を構成している。 The imaging optical system 1 of Embodiment 2 (see FIG. 10) includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a positive third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When each lens is viewed with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is on the object side. The fourth lens L4 is a positive meniscus lens convex to the image side, and the fifth lens L5 is a negative meniscus lens concave to the image side. In addition, the first lens L1 and the second lens L2 have a positive refractive power as a whole, the first lens group LG1, and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole, a second lens group LG2. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
　実施例３の撮像光学系１（図１１参照）は、物体側から順に、正の第１レンズＬ１と、開口絞りＳＴと、負の第２レンズＬ２と、正の第３レンズＬ３と、正の第４レンズＬ４と、負の第５レンズＬ５と、から構成されており、レンズ面は全て非球面である。近軸の面形状で各レンズを見た場合、第１レンズＬ１は両凸の正レンズであり、第２レンズＬ２は像側に凹の負メニスカスレンズであり、第３レンズＬ３は物体側に凸の正メニスカスレンズであり、第４レンズＬ４は像側に凸の正メニスカスレンズであり、第５レンズＬ５は像側に凹の負メニスカスレンズである。なお、第１レンズＬ１及び第２レンズＬ２が全体として正の屈折力を有する第１レンズ群ＬＧ１を、第３レンズＬ３及び第４レンズＬ４が全体として正の屈折力を有する第２レンズ群ＬＧ２を、第５レンズＬ５が全体として負の屈折力を有する第３レンズ群ＬＧ３を構成している。 The imaging optical system 1 (see FIG. 11) of Example 3 includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a positive third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When each lens is viewed with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is on the object side. The fourth lens L4 is a positive meniscus lens convex to the image side, and the fifth lens L5 is a negative meniscus lens concave to the image side. In addition, the first lens L1 and the second lens L2 have a positive refractive power as a whole, the first lens group LG1, and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole, a second lens group LG2. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
　実施例４の撮像光学系１（図１２参照）は、物体側から順に、正の第１レンズＬ１と、開口絞りＳＴと、負の第２レンズＬ２と、負の第３レンズＬ３と、正の第４レンズＬ４と、負の第５レンズＬ５と、から構成されており、レンズ面は全て非球面である。近軸の面形状で各レンズを見た場合、第１レンズＬ１は物体側に凸の正メニスカスレンズであり、第２レンズＬ２は像側に凹の負メニスカスレンズであり、第３レンズＬ３は像側に凹の負メニスカスレンズであり、第４レンズＬ４は像側に凸の正メニスカスレンズであり、第５レンズＬ５は像側に凹の負メニスカスレンズである。なお、第１レンズＬ１及び第２レンズＬ２が全体として正の屈折力を有する第１レンズ群ＬＧ１を、第３レンズＬ３及び第４レンズＬ４が全体として正の屈折力を有する第２レンズ群ＬＧ２を、第５レンズＬ５が全体として負の屈折力を有する第３レンズ群ＬＧ３を構成している。 The imaging optical system 1 (see FIG. 12) of Example 4 includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a negative third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When viewing each lens with a paraxial surface shape, the first lens L1 is a positive meniscus lens convex on the object side, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is The negative meniscus lens is concave on the image side, the fourth lens L4 is a positive meniscus lens convex on the image side, and the fifth lens L5 is a negative meniscus lens concave on the image side. In addition, the first lens L1 and the second lens L2 have a positive refractive power as a whole, the first lens group LG1, and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole, a second lens group LG2. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
　実施例５の撮像光学系１（図１３参照）は、物体側から順に、正の第１レンズＬ１と、開口絞りＳＴと、負の第２レンズＬ２と、負の第３レンズＬ３と、正の第４レンズＬ４と、負の第５レンズＬ５と、から構成されており、レンズ面は全て非球面である。近軸の面形状で各レンズを見た場合、第１レンズＬ１は両凸の正レンズであり、第２レンズＬ２は像側に凹の負メニスカスレンズであり、第３レンズＬ３は像側に凹の負メニスカスレンズであり、第４レンズＬ４は両凸の正レンズであり、第５レンズＬ５は像側に凹の負メニスカスレンズである。なお、第１レンズＬ１及び第２レンズＬ２が全体として正の屈折力を有する第１レンズ群ＬＧ１を、第３レンズＬ３及び第４レンズＬ４が全体として正の屈折力を有する第２レンズ群ＬＧ２を、第５レンズＬ５が全体として負の屈折力を有する第３レンズ群ＬＧ３を構成している。 The imaging optical system 1 of Embodiment 5 (see FIG. 13) includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a negative third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When each lens is viewed with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is on the image side. A concave negative meniscus lens, the fourth lens L4 is a biconvex positive lens, and the fifth lens L5 is a negative meniscus lens concave on the image side. In addition, the first lens L1 and the second lens L2 have a positive refractive power as a whole, the first lens group LG1, and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole, a second lens group LG2. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
　実施例６の撮像光学系１（図１４参照）は、物体側から順に、開口絞りＳＴと、正の第１レンズＬ１と、負の第２レンズＬ２と、正の第３レンズＬ３と、負の第４レンズＬ４と、から構成されており、レンズ面は全て非球面である。近軸の面形状で各レンズを見た場合、第１レンズＬ１は両凸の正レンズであり、第２レンズＬ２は像側に凹の負メニスカスレンズであり、第３レンズＬ３は両凸の正レンズであり、第４レンズＬ４は像側に凹の負メニスカスレンズである。なお、第１レンズＬ１及び第２レンズＬ２が全体として正の屈折力を有する第１レンズ群ＬＧ１を、第３レンズＬ３が全体として正の屈折力を有する第２レンズ群ＬＧ２を、第４レンズＬ４が全体として負の屈折力を有する第３レンズ群ＬＧ３を構成している。 The imaging optical system 1 (see FIG. 14) of Example 6 includes, in order from the object side, an aperture stop ST, a positive first lens L1, a negative second lens L2, a positive third lens L3, and a negative 4th lens L4, and all the lens surfaces are aspherical surfaces. When viewing each lens with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is biconvex. The fourth lens L4 is a negative meniscus lens that is concave on the image side. The first lens L1 and the second lens L2 as a whole have a first lens group LG1 having a positive refractive power, the third lens L3 has a second lens group LG2 as a whole having a positive refractive power, and a fourth lens. L4 constitutes a third lens group LG3 having a negative refractive power as a whole.
　実施例７の撮像光学系１（図１５参照）は、物体側から順に、開口絞りＳＴと、正の第１レンズＬ１と、負の第２レンズＬ２と、正の第３レンズＬ３と、負の第４レンズＬ４と、から構成されており、レンズ面は全て非球面である。近軸の面形状で各レンズを見た場合、第１レンズＬ１は両凸の正レンズであり、第２レンズＬ２は像側に凹の負メニスカスレンズであり、第３レンズＬ３は像側に凸の正メニスカスレンズであり、第４レンズＬ４は像側に凹の負メニスカスレンズである。なお、第１レンズＬ１及び第２レンズＬ２が全体として正の屈折力を有する第１レンズ群ＬＧ１を、第３レンズＬ３が全体として正の屈折力を有する第２レンズ群ＬＧ２を、第４レンズＬ４が全体として負の屈折力を有する第３レンズ群ＬＧ３を構成している。 The imaging optical system 1 according to the seventh embodiment (see FIG. 15) includes, in order from the object side, an aperture stop ST, a positive first lens L1, a negative second lens L2, a positive third lens L3, and a negative 4th lens L4, and all the lens surfaces are aspherical surfaces. When each lens is viewed with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is on the image side. The fourth lens L4 is a negative meniscus lens that is concave on the image side. The first lens L1 and the second lens L2 as a whole have a first lens group LG1 having a positive refractive power, the third lens L3 has a second lens group LG2 as a whole having a positive refractive power, and a fourth lens. L4 constitutes a third lens group LG3 having a negative refractive power as a whole.
　実施例８の撮像光学系１（図１６参照）は、物体側から順に、正の第１レンズＬ１と、開口絞りＳＴと、負の第２レンズＬ２と、正の第３レンズＬ３と、正の第４レンズＬ４と、負の第５レンズＬ５と、から構成されており、レンズ面は全て非球面である。近軸の面形状で各レンズを見た場合、第１レンズＬ１は両凸の正レンズであり、第２レンズＬ２は像側に凹の負メニスカスレンズであり、第３レンズＬ３は両凸の正レンズであり、第４レンズＬ４は像側に凸の正メニスカスレンズであり、第５レンズＬ５は像側に凹の負メニスカスレンズである。なお、第１レンズＬ１及び第２レンズＬ２が全体として正の屈折力を有する第１レンズ群ＬＧ１を、第３レンズＬ３及び第４レンズＬ４が全体として正の屈折力を有する第２レンズ群ＬＧ２を、第５レンズＬ５が全体として負の屈折力を有する第３レンズ群ＬＧ３を構成している。 The imaging optical system 1 of Embodiment 8 (see FIG. 16) includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a positive third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When viewing each lens with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is biconvex. The fourth lens L4 is a positive meniscus lens convex on the image side, and the fifth lens L5 is a negative meniscus lens concave on the image side. In addition, the first lens L1 and the second lens L2 have a positive refractive power as a whole, the first lens group LG1, and the third lens L3 and the fourth lens L4 have a positive refractive power as a whole, a second lens group LG2. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
　実施例９の撮像光学系１（図１７参照）は、物体側から順に、開口絞りＳＴと、正の第１レンズＬ１と、負の第２レンズＬ２と、正の第３レンズＬ３と、負の第４レンズＬ４と、から構成されており、レンズ面は全て非球面である。近軸の面形状で各レンズを見た場合、第１レンズＬ１は両凸の正レンズであり、第２レンズＬ２は像側に凹の負メニスカスレンズであり、第３レンズＬ３は像側に凸の正メニスカスレンズであり、第４レンズＬ４は像側に凹の負メニスカスレンズである。なお、第１レンズＬ１及び第２レンズＬ２が全体として正の屈折力を有する第１レンズ群ＬＧ１を、第３レンズＬ３が全体として正の屈折力を有する第２レンズ群ＬＧ２を、第４レンズＬ４が全体として負の屈折力を有する第３レンズ群ＬＧ３を構成している。 The imaging optical system 1 according to the ninth embodiment (see FIG. 17) includes, in order from the object side, an aperture stop ST, a positive first lens L1, a negative second lens L2, a positive third lens L3, and a negative 4th lens L4, and all the lens surfaces are aspherical surfaces. When each lens is viewed with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens L3 is on the image side. The fourth lens L4 is a negative meniscus lens that is concave on the image side. The first lens L1 and the second lens L2 as a whole have a first lens group LG1 having a positive refractive power, the third lens L3 has a second lens group LG2 as a whole having a positive refractive power, and a fourth lens. L4 constitutes a third lens group LG3 having a negative refractive power as a whole.
　実施例１０の撮像光学系１（図１８参照）は、物体側から順に、正の第１レンズＬ１と、開口絞りＳＴと、負の第２レンズＬ２と、負の第３レンズＬ３と、正の第４レンズＬ４と、負の第５レンズＬ５と、から構成されており、レンズ面は全て非球面である。近軸の面形状で各レンズを見た場合、第１レンズＬ１は両凸の正レンズであり、第２レンズＬ２は両凹の負レンズであり、第３レンズＬ３は像側に凹の負メニスカスレンズであり、第４レンズＬ４は両凸の正レンズであり、第５レンズＬ５は両凹の負レンズである。なお、第１レンズＬ１、第２レンズＬ２及び第３レンズＬ３が全体として正の屈折力を有する第１レンズ群ＬＧ１を、第４レンズＬ４が全体として正の屈折力を有する第２レンズ群ＬＧ２を、第５レンズＬ５が全体として負の屈折力を有する第３レンズ群ＬＧ３を構成している。 The imaging optical system 1 (see FIG. 18) of Example 10 includes, in order from the object side, a positive first lens L1, an aperture stop ST, a negative second lens L2, a negative third lens L3, and a positive 4th lens L4 and negative 5th lens L5, and all the lens surfaces are aspherical surfaces. When viewing each lens with a paraxial surface shape, the first lens L1 is a biconvex positive lens, the second lens L2 is a biconcave negative lens, and the third lens L3 is a concave negative lens on the image side. The fourth lens L4 is a biconvex positive lens, and the fifth lens L5 is a biconcave negative lens. The first lens L1, the second lens L2, and the third lens L3 have a first lens group LG1 having a positive refractive power as a whole, and the fourth lens L4 has a second lens group LG2 having a positive refractive power as a whole. The fifth lens L5 constitutes a third lens group LG3 having a negative refractive power as a whole.
Figure JPOXMLDOC01-appb-I000002
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　図１９～図２８に示すように、実施例１～１０の撮像光学系は良好な収差特性を示す。また、実施例１～１０いずれも条件式（１）、（２）、（３）を満足する。すなわち、本発明によれば、良好な光学特性を備える撮像光学系を精度良く、効率的に得ることが可能である。 As shown in FIGS. 19 to 28, the imaging optical systems of Examples 1 to 10 exhibit good aberration characteristics. In addition, all of Examples 1 to 10 satisfy the conditional expressions (1), (2), and (3). That is, according to the present invention, an imaging optical system having good optical characteristics can be obtained with high accuracy and efficiency.
　ところで、上述した実施例では、固体撮像素子７０の撮像面７０ａに入射する光束の主光線入射角が、撮像面７０ａ周辺部において必ずしも十分に小さい設計にはなっていない。しかし、最近の技術では、固体撮像素子の色フィルターやオンチップマイクロレンズアレイの配列の見直しによって、シェーディングを軽減することができるようになってきている。具体的には、固体撮像素子の撮像面の画素ピッチに対し、色フィルターやオンチップマイクロレンズアレイの配列のピッチをわずかに小さく設定すれば、撮像面の周辺部にいくほど各画素に対し色フィルターやオンチップマイクロレンズアレイが撮像光学系（撮像レンズ）の光軸側へシフトするため、斜入射の光束を効率的に各画素の受光部に導くことができる。これにより固体撮像素子で発生するシェーディングを小さく抑えることができる。この点を考慮して、上述の各実施例では、より小型化を目指した設計例となっている。 Incidentally, in the above-described embodiment, the principal ray incident angle of the light beam incident on the imaging surface 70a of the solid-state imaging device 70 is not necessarily designed to be sufficiently small in the periphery of the imaging surface 70a. However, with recent technology, it has become possible to reduce shading by reviewing the arrangement of the color filters of the solid-state imaging device and the on-chip microlens array. Specifically, if the pitch of the arrangement of the color filters and the on-chip microlens array is set slightly smaller than the pixel pitch of the imaging surface of the solid-state imaging device, the color for each pixel increases toward the periphery of the imaging surface Since the filter and the on-chip microlens array shift to the optical axis side of the imaging optical system (imaging lens), the obliquely incident light beam can be efficiently guided to the light receiving portion of each pixel. Thereby, the shading which generate | occur | produces with a solid-state image sensor can be restrained small. In consideration of this point, each of the above-described embodiments is a design example aimed at further miniaturization.
（その他）
　なお、本発明は以上に示した実施形態及び実施例の構成に限定されない。すなわち、本発明の目的を逸脱しない範囲で種々の変更が可能である。例えば、以上においては、位置基準マークがレンズセンタに設けられる構成を示したが、位置基準マークが設けられる位置はこの位置に限定されるものではない。例えば、レンズ周辺のコバ部（レンズの有効部の周囲に設けられる部分；例えば図２の符号Ｌ２ＡやＬ５Ａ参照）に設けられる構成としても勿論構わない。この場合の位置基準マークは、本実施形態で示したような構成でも良いし、その他リング状等であっても構わない。 (Other)
In addition, this invention is not limited to the structure of embodiment shown in the above and an Example. That is, various modifications can be made without departing from the object of the present invention. For example, in the above description, the position reference mark is provided in the lens center. However, the position where the position reference mark is provided is not limited to this position. For example, it is of course possible to adopt a configuration provided in the edge portion around the lens (a portion provided around the effective portion of the lens; for example, see L2A and L5A in FIG. 2). In this case, the position reference mark may have the configuration shown in the present embodiment, or may have a ring shape or the like.
　本発明は、固体撮像素子の撮像面に被写体を結像させる撮像光学系に好適である。 The present invention is suitable for an imaging optical system that forms an image of a subject on the imaging surface of a solid-state imaging device.
　１　　　撮像光学系
　１３　　第１のレンズホルダー（第１の保持部材）
　１３ａ　レンズ保持空間
　１３ｃ　接着剤充填部
　１３ｄ　空間部
　２２　　第２のレンズホルダー（第２の保持部材）
　４１　　第１のフレーム（第３の保持部材）
　７０　　固体撮像素子
　７０ａ　撮像面
　ＡＸ　　光軸
　Ｌ１　　第１レンズ（最物体側の正レンズ）
　Ｌ２　　第２レンズ
　Ｌ３　　第３レンズ
　Ｌ４　　第４レンズ
　Ｌ５　　第５レンズ
　ＬＧ１　第１レンズ群
　ＬＧ２　第２レンズ群
　ＬＧ３　第３レンズ群 DESCRIPTION OF SYMBOLS 1 Imaging optical system 13 1st lens holder (1st holding member)
13a Lens holding space 13c Adhesive filling portion 13d Space portion 22 Second lens holder (second holding member)
41 First frame (third holding member)
70 Solid-state imaging device 70a Imaging surface AX Optical axis L1 First lens (most object side positive lens)
L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens LG1 1st lens group LG2 2nd lens group LG3 3rd lens group

Claims (17)

  1. 　固体撮像素子の撮像面に被写体を結像させる単焦点の撮像光学系であって、
    　物体側から像側へと向かって順に、最物体側に配置される正レンズを含む少なくとも２枚のレンズからなって全体として正の屈折力を有する第１レンズ群、少なくとも１枚のレンズからなって全体として正の屈折力を有する第２レンズ群、少なくとも１枚のレンズからなる第３レンズ群を備え、
    　前記第１レンズ群と前記第３レンズ群とは、前記撮像面に対して固定され、
    　前記第２レンズ群は、フォーカス調整のために光軸方向に移動可能に設けられ、
    　以下の条件式を満たすことを特徴とする撮像光学系。
    　０．１＜ｆ１／ｆｇ２＜２
    但し、
    　ｆ１：最物体側の正レンズの焦点距離
    　ｆｇ２：第２レンズ群の焦点距離     A single-focus imaging optical system that forms an image of a subject on an imaging surface of a solid-state imaging device,
    In order from the object side to the image side, the first lens group including at least two lenses including a positive lens disposed on the most object side and having a positive refractive power as a whole, includes at least one lens. A second lens group having a positive refractive power as a whole, a third lens group comprising at least one lens,
    The first lens group and the third lens group are fixed with respect to the imaging surface,
    The second lens group is provided to be movable in the optical axis direction for focus adjustment,
    An imaging optical system characterized by satisfying the following conditional expression:
    0.1 <f1 / fg2 <2
    However,
    f1: Focal length of the positive lens closest to the object fg2: Focal length of the second lens group
  2. 　更に、以下の条件式を満たすことを特徴とする請求項１に記載の撮像光学系。
    　０．１＜ｆｇ２／ｆ＜２
    　但し、
    　ｆｇ２：第２レンズ群の焦点距離
    　ｆ：撮像光学系全体の焦点距離     The imaging optical system according to claim 1, further satisfying the following conditional expression:
    0.1 <fg2 / f <2
    However,
    fg2: focal length of the second lens group f: focal length of the entire imaging optical system
  3. 　更に、以下の条件式を満たすことを特徴とする請求項１に記載の撮像光学系。
    　１．０＜ｆｇ１／ｆ＜３．０
    　但し、
    　ｆｇ１：第１レンズ群の焦点距離
    　ｆ：撮像光学系全体の焦点距離     The imaging optical system according to claim 1, further satisfying the following conditional expression:
    1.0 <fg1 / f <3.0
    However,
    fg1: Focal length of the first lens group f: Focal length of the entire imaging optical system
  4. 　更に、以下の条件式を満たすことを特徴とする請求項２に記載の撮像光学系。
    　１．０＜ｆｇ１／ｆ＜３．０
    　但し、
    　ｆｇ１：第１レンズ群の焦点距離
    　ｆ：撮像光学系全体の焦点距離     The imaging optical system according to claim 2, further satisfying the following conditional expression:
    1.0 <fg1 / f <3.0
    However,
    fg1: Focal length of the first lens group f: Focal length of the entire imaging optical system
  5. 　前記第１レンズ群を保持する第１の保持部材と、前記第２レンズ群を保持する第２の保持部材と、前記第３レンズ群を保持する第３の保持部材と、を有し、
    　前記第１の保持部材のレンズ保持空間は、光軸と垂直な方向の直径が前記最物体側に配置される正レンズの直径よりも大きく形成されていることを特徴とする請求項１から４のいずれかに記載の撮像光学系。     A first holding member that holds the first lens group, a second holding member that holds the second lens group, and a third holding member that holds the third lens group,
    The lens holding space of the first holding member is formed so that a diameter in a direction perpendicular to the optical axis is larger than a diameter of a positive lens arranged on the most object side. The imaging optical system according to any one of the above.
  6. 　前記第１の保持部材は、前記レンズ保持空間の周囲に調整治具を配置するための空間部を更に備えることを特徴とする請求項５に記載の撮像光学系。 The imaging optical system according to claim 5, wherein the first holding member further includes a space for arranging an adjustment jig around the lens holding space.
  7. 　前記第１の保持部材は、前記最物体側に配置される正レンズの側面を接着固定するための接着剤充填部を更に備え、前記空間部が前記接着剤充填部を挟むように、前記空間部と前記接着剤充填部とが前記第１の保持部材の円周方向に配列されていることを特徴とする請求項６に記載の撮像光学系。 The first holding member further includes an adhesive filling portion for bonding and fixing a side surface of a positive lens disposed on the most object side, and the space portion sandwiches the adhesive filling portion. The imaging optical system according to claim 6, wherein the portion and the adhesive filling portion are arranged in a circumferential direction of the first holding member.
  8. 　前記第３レンズ群には負レンズが含まれることを特徴とする請求項１から４のいずれかに記載の撮像光学系。 5. The imaging optical system according to claim 1, wherein the third lens group includes a negative lens.
  9. 　物体側から像側へと向かって順に、最物体側に配置される正レンズを含む少なくとも２枚のレンズからなって全体として正の屈折力を有する第１レンズ群、少なくとも１枚のレンズからなって全体として正の屈折力を有する第２レンズ群、少なくとも１枚のレンズからなる第３レンズ群を備え、前記第１レンズ群と前記第３レンズ群とは撮像面に対して固定され、前記第２レンズ群はフォーカス調整のために光軸方向に移動可能に設けられる単焦点の撮像光学系の光学調整方法であって、
    　前記最物体側の正レンズを光軸と垂直な方向に動かして光学系全体の偏芯調整を行う調芯工程を備えることを特徴とする光学調整方法。     In order from the object side to the image side, the first lens group including at least two lenses including a positive lens disposed on the most object side and having a positive refractive power as a whole includes at least one lens. A second lens group having a positive refractive power as a whole, a third lens group comprising at least one lens, and the first lens group and the third lens group are fixed with respect to the imaging surface, The second lens group is an optical adjustment method of a single-focus imaging optical system provided to be movable in the optical axis direction for focus adjustment,
    An optical adjustment method comprising an alignment step of adjusting the decentering of the entire optical system by moving the positive lens on the most object side in a direction perpendicular to the optical axis.
  10. 　前記撮像光学系は、以下の条件式を満たすことを特徴とする請求項９に記載の光学調整方法。
    　０．１＜ｆ１／ｆｇ２＜２
    但し、
    　ｆ１：最物体側の正レンズの焦点距離
    　ｆｇ２：第２レンズ群の焦点距離     The optical adjustment method according to claim 9, wherein the imaging optical system satisfies the following conditional expression.
    0.1 <f1 / fg2 <2
    However,
    f1: Focal length of the positive lens closest to the object fg2: Focal length of the second lens group
  11. 　前記第２レンズ群の傾きを調整する傾き調整工程を更に備え、
    　前記調芯工程は前記傾き調整工程後に行われることを特徴とする請求項９又は１０に記載の光学調整方法。     A tilt adjustment step of adjusting the tilt of the second lens group;
    The optical adjustment method according to claim 9, wherein the alignment step is performed after the inclination adjustment step.
  12. 　前記調芯工程を行う際に、前記最物体側の正レンズを光軸方向に動かす位置調整が併せて行われることを特徴とする請求項９又は１０に記載の光学調整方法。 11. The optical adjustment method according to claim 9, wherein, when performing the alignment process, position adjustment for moving the positive lens on the most object side in the optical axis direction is also performed.
  13. 　前記調芯工程後に、前記第１レンズ群を光軸方向に動かす位置調整が行われることを特徴とする請求項９又は１０に記載の光学調整方法。 The optical adjustment method according to claim 9 or 10, wherein a position adjustment for moving the first lens group in the optical axis direction is performed after the alignment step.
  14. 　前記調芯工程は、光学調整専用に準備された固体撮像素子を用いて行われることを特徴とする請求項９又は１０に記載の光学調整方法。 11. The optical adjustment method according to claim 9, wherein the alignment step is performed using a solid-state imaging device prepared exclusively for optical adjustment.
  15. 　前記調芯工程は、製品として組み込まれた固体撮像素子を用いて行われることを特徴とする請求項９又は１０に記載の光学調整方法。 The optical adjustment method according to claim 9 or 10, wherein the alignment step is performed using a solid-state imaging device incorporated as a product.
  16. 　前記第１レンズ群には、前記最物体側に配置される正レンズとは異なるレンズであって第１の位置基準マークを有するレンズが含まれ、前記第３レンズ群には第２の位置基準マークを有するレンズが含まれ、
    　前記最物体側に配置される正レンズを前記第１レンズ群に含ませる前に、光軸に沿う方向から観察した場合に、前記第１の位置基準マークと前記第２の位置基準マークとが一致するように、前記第１レンズ群と前記第３レンズ群との相対位置調整が行われることを特徴とする請求項９又は１０に記載の光学調整方法。     The first lens group includes a lens that is different from the positive lens disposed on the most object side and has a first position reference mark, and the third lens group includes a second position reference. Including a lens with a mark,
    Before the positive lens arranged on the most object side is included in the first lens group, the first position reference mark and the second position reference mark are observed when viewed from the direction along the optical axis. 11. The optical adjustment method according to claim 9, wherein relative position adjustment between the first lens group and the third lens group is performed so as to coincide with each other.
  17. 　前記撮像光学系は、以下の条件式を満たすことを特徴とする請求項１６に記載の光学調整方法。
    　０．１＜ｆｇ２／ｆ＜２
    　但し、
    　ｆｇ２：第２レンズ群の焦点距離
    　ｆ：撮像光学系全体の焦点距離     The optical adjustment method according to claim 16, wherein the imaging optical system satisfies the following conditional expression.
    0.1 <fg2 / f <2
    However,
    fg2: focal length of the second lens group f: focal length of the entire imaging optical system
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