WO2020019705A1 - 摄像镜头、摄像模组及终端 - Google Patents

摄像镜头、摄像模组及终端 Download PDF

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Publication number
WO2020019705A1
WO2020019705A1 PCT/CN2019/075626 CN2019075626W WO2020019705A1 WO 2020019705 A1 WO2020019705 A1 WO 2020019705A1 CN 2019075626 W CN2019075626 W CN 2019075626W WO 2020019705 A1 WO2020019705 A1 WO 2020019705A1
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Prior art keywords
lens
facing
optical axis
surface side
image
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PCT/CN2019/075626
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English (en)
French (fr)
Inventor
於丰
安澤卓也
野田百合
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华为技术有限公司
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Priority to EP19840161.4A priority Critical patent/EP3779551A4/en
Publication of WO2020019705A1 publication Critical patent/WO2020019705A1/zh
Priority to US17/111,395 priority patent/US20210088757A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
    • G02B27/4205—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant
    • 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
    • G02B13/0055—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras employing a special optical element
    • G02B13/0075—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras employing a special optical element having an element with variable optical properties
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
    • 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
    • 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
    • G02B13/0055—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras employing a special optical element
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
    • G02B27/4205—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant
    • G02B27/4211—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant correcting chromatic aberrations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/50—Constructional details
    • H04N23/55—Optical parts specially adapted for electronic image sensors; Mounting thereof

Definitions

  • the present invention relates to the field of optical imaging technology, and in particular, to a camera lens, a camera module, and a terminal.
  • the shooting function has become an indispensable feature of many smart terminals (such as smart phones).
  • smart terminals such as smart phones.
  • the camera lens is a core component of the camera module of a smartphone, and its technology has developed rapidly.
  • users' demands for miniaturization of smartphones and high imaging quality (large aperture) of shooting functions are increasing.
  • the evaluation parameters of high imaging quality include optical indicators such as chromatic aberration, monochromatic aberration (including astigmatism, distortion, spherical aberration, etc.).
  • optical indicators such as chromatic aberration, monochromatic aberration (including astigmatism, distortion, spherical aberration, etc.).
  • chromatic aberration including astigmatism, distortion, spherical aberration, etc.
  • monochromatic aberration including astigmatism, distortion, spherical aberration, etc.
  • One method is to choose a low-dispersion optical material to make the lens, which is helpful to eliminate chromatic aberration.
  • the dispersion of lenses made of glass materials is relatively low, while the dispersion of lenses made of plastic materials is relatively large.
  • the processing requirements are very high and the cost is relatively expensive , which greatly limits its application on the lens of smart phones.
  • Another method is to increase the number of lenses in the camera lens, and to better eliminate chromatic aberration by adding several lenses.
  • the current higher-end camera lenses generally use 6 lens combinations, and many companies are actively developing technologies of 7 or 8 lens combinations in order to further eliminate chromatic aberrations to improve imaging quality.
  • this method is easily limited by the size of the smart phone, which contradicts the trend of thin and thin smart phones.
  • the camera lens of a smart phone is mainly designed for an image sensor of 1 / 3.2 inch to 1 / 3.0 inch, and the total optical total length (TTL) is generally about 5.0 mm.
  • TTL total optical total length
  • larger size and higher resolution image sensors such as 1 / 2.8 inch to 1 / 2.3 inch
  • the mainstream camera lens design solution will inevitably lead to a further increase in the TTL parameter.
  • due to the limitation of the size of the smart phone it is difficult to further increase the total thickness and area of the camera lens, and it is more difficult to meet the miniaturization and high imaging quality at the same time.
  • Embodiments of the present invention provide a camera lens, a camera module, and a terminal.
  • the camera lens can meet the requirements of miniaturization and high imaging quality, and meet the requirements of an increased image sensor format.
  • an embodiment of the present invention provides a camera lens.
  • the camera lens includes the first lens, the second lens, and the lens module along the optical axis from the object surface to the image surface.
  • the second lens is a diffractive optical element, and the diffractive optical element is located between the first lens and the lens module, and
  • the first lens is separated from the lens module, and the optical axes of the first lens, the diffractive optical element, and the N lenses located in the lens module are coincident with each other. among them:
  • the first lens includes two surfaces facing away from each other, wherein a surface facing the object surface side is convex at the optical axis, and a surface facing the image surface side is concave at the optical axis; the first lens has a positive optical power. ;
  • a diffractive optical element includes two layers of different optical materials and an optical diffraction grating located therebetween, that is, the diffractive optical element includes a surface facing the object surface side, a surface facing the image surface side, and the two The diffractive surface between the surfaces; wherein the surface facing the object surface side is convex at the optical axis, and the surface facing the image surface side is concave at the optical axis; the diffractive optical element has a positive optical power;
  • the element has the property of negative anomalous dispersion (negative dispersion for short), so the diffractive optical element can be used to offset the positive dispersion of the refractive element (such as L1, lens module).
  • a lens module includes N lenses arranged at intervals along the optical axis, where N is an integer greater than or equal to 3 and less than or equal to 7; a surface of each lens of the N lenses facing the object surface side and an image surface side At least one of the surfaces is an aspheric surface, and the lens module has a positive optical power to balance monochromatic aberrations such as spherical aberration and astigmatism.
  • the camera lens provided by the embodiment of the present invention can use the negative dispersion of the diffractive optical element to offset the positive dispersion of the refractive element (such as L1 and lens module), thereby effectively reducing the chromatic aberration of the imaging;
  • the lens module can further balance monochromatic aberrations such as astigmatism, spherical aberration, and distortion.
  • a camera lens designed with such a structural frame will be able to design a large-aperture camera lens for image sensors of different sizes (such as large-format image sensors of 1 / 2.8 inch to 1 / 2.3 inch, etc.), improving Imaging quality;
  • the camera lens implementing the embodiments of the present invention it will be possible to achieve smaller size by optimizing the physical parameters (such as aspheric coefficient, thickness, lens material, refractive index, etc.) of each lens of the camera lens. TTL to meet the miniaturization needs of camera lenses. That is to say, the camera lens provided by the embodiment of the present invention can satisfy both the miniaturization and the high imaging quality, and also meet the requirements of the increased size of the image sensor.
  • the aperture value Fno (F value) of the camera lens is between 2.0 and 1.2, such as F1.6, F1.5, F1.4, and the like.
  • all lenses in the camera lens may be made of plastic materials, so implementing the embodiments of the present invention is also beneficial to reducing the cost of the camera lens.
  • L1 may specifically use cycloolefin-based low-dispersion materials; the lenses in the lens module may be selected using conventional lens materials (such as polycarbonate-based high-dispersion materials, or according to the structural design of the camera lens) Cycloolefin type low dispersion materials, etc.).
  • the lens material between the surface facing the object surface side and the diffractive surface is made of a thio resin material with low dispersion, and the refractive index N1 of the material is in a range of 1.62 ⁇ N1 ⁇ 1.76; the diffractive surface and the direction
  • the lens material between the surfaces on the image surface side uses a high-dispersion polycarbonate-based or modified alkane-based material, and the range of the refractive index N2 of the material is 1.55 ⁇ N2 ⁇ 1.64.
  • the power of the material located between the surface facing the object surface side and the diffractive surface is P1
  • the surface facing the image surface side and the diffractive surface The optical power between the materials is P2, and P1 and P2 satisfy the conditional expression: -4 ⁇ P1 / P2 ⁇ 4.
  • the power P1 and P2 of the diffractive optical element and the power P front (that is, the power of the first lens L1) of the previous lens of the diffractive optical element, and the power P last ( That is, the power of the third lens L3 in the lens module) can also satisfy the following conditions: Abs (P1 / P front ) ⁇ 4; Abs (P2 / P last ) ⁇ Abs (P1 / P front ), where , Abs represents an absolute value function. Since two optical powers are used to disperse the optical power, the refraction requirements of a single lens for light can be reduced, and monochromatic images such as spherical aberration, astigmatism, and distortion caused by a single large optical power can be reduced. Poor, achieving a very large aperture with a small total optical length.
  • the Abbe number of the d-line of the sodium spectrum of the material between the surface facing the object surface side and the diffractive surface is V d 21
  • the Abbe number of the d-line of the sodium spectrum between the material on the image plane side and the diffractive surface is V d 22
  • V d 21 and V d 22 satisfy the following conditional expressions: 30 ⁇ V d 21 ⁇ 60; 20 ⁇ V d 22 ⁇ 40.
  • the Abbe numbers of lens A and lens B of the diffractive optical element and the Abbe number of the previous lens of the optical diffractive element that is, the Abbe number V d 1 of the material used for the first lens L1
  • the optical diffractive element The following conditions can also be satisfied between the Abbe number of the latter lens (that is, the Abbe number Vd3 of the material used for the third lens L3 in the lens module): V d 1 ⁇ V d 21 ⁇ V d 22 ⁇ V d 3, or V d 1 ⁇ V d 21 ⁇ V d 22 ⁇ V d 3.
  • the thickness of the lens A in the diffractive optical element is H1, and H1 satisfies: 0 ⁇ H1 ⁇ 0.5mm; the thickness of the lens B is H2, and H2 satisfies: 0 ⁇ H2 ⁇ 0.5mm .
  • the diffraction grating is arranged between the lens A and the lens B, and its grating height Gh satisfies 0 ⁇ Gh ⁇ 50um, that is, the thickness of the diffraction grating is between 0-50um.
  • At least one of the surface of the diffractive optical element facing the object surface side and the surface facing the image surface side is an aspheric surface, in order to balance spherical aberration, astigmatism, and the like. Chromatic aberration.
  • the surface of the diffractive optical element facing the object surface side and the surface facing the image surface side are both aspheric surfaces.
  • the two surfaces of the first lens L1 and the surfaces of all lenses in the lens module may be aspheric, so as to better balance monochromatic aberrations such as spherical aberration and astigmatism. .
  • the lens module includes the following four lenses: a third lens, a fourth lens, a fifth lens, and a sixth lens, that is, the camera lens includes at least six independent lenses: A lens, a second lens (ie, a diffractive optical element), a third lens, a fourth lens, a fifth lens, and a sixth lens. among them:
  • the third lens L3 includes two surfaces: a surface facing the object surface side and a surface facing the image surface side. At least one of the two surfaces is an aspheric surface in order to correct the residual aberration and reduce the image. The effect of divergence.
  • the surface facing the object surface side has a convex shape at the optical axis X
  • the surface facing the object surface side may have a convex shape or a concave shape at the optical axis X
  • the third lens has a positive optical power.
  • the fourth lens L4 has a meniscus shape and includes two surfaces: a surface facing the object surface side and a surface facing the image surface side.
  • the surface facing the object side is concave at the optical axis.
  • L4 can be used to correct on-axis chromatic aberration (a type of positional chromatic aberration) and to correct chromatic aberration of magnification, and to correct low images up to about 70%. Distortion in image height.
  • L4 has a weaker positive or negative power.
  • the fifth lens L5 includes two surfaces: a surface facing the object surface side and a surface facing the image surface side. Both surfaces may be aspheric to facilitate correction of spherical aberration at the periphery of the lens. It is beneficial to control the light emitted from L5 to an appropriate angle between low image height and maximum image height.
  • L5 has a meniscus shape.
  • the surface on the object side is convex on the optical axis X
  • the surface on the image side is concave on the optical axis X.
  • at least one of the two surfaces In the middle there is an inverse curve point at a position away from the optical axis X, that is, the shape of the peripheral portion of the surface is curved toward the object surface side.
  • the sixth lens L6 includes two surfaces: a surface facing the object surface side and a surface facing the image surface side. Both of these surfaces may be aspheric. Specifically, the surface facing the object surface side is at the optical axis X. The convex shape, the surface facing the image surface side is concave at the optical axis X, and L6 has a negative optical power, which is helpful for ensuring the back focus, correcting astigmatism, and controlling the incident angle of the main ray to the image sensor.
  • the surface facing the image plane side there is an inverse curve point at a position away from the optical axis X, that is, the surface facing the image plane side is a concave surface in the vicinity of the optical axis X, and faces toward the peripheral portion.
  • Convex aspheric surface Therefore, the lower the power of L6 is toward the peripheral part of the lens, the weaker the negative power, or the positive power changes gradually at the peripheral part.
  • the surface facing the object surface side also has an aspheric surface having a positive refractive power change at the peripheral portion. In this way, the peripheral portion of the lens of L6 distributes the required positive power to these two faces, thereby preventing a sharp change in the shape of L6.
  • the lens module includes the following five lenses: a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens, that is, the camera lens includes at least 7 Independent lenses: a first lens, a second lens (ie, a diffractive optical element), a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens. among them:
  • the third lens L3 includes two surfaces: a surface facing the object surface side and a surface facing the image surface side. At least one of the two surfaces is an aspheric surface in order to correct the residual aberration and reduce the size of the aberration.
  • the effect of astigmatism Specifically, the surface facing the object surface side has a concave shape at the optical axis X, the surface facing the image surface side can have a convex shape or a concave shape at the optical axis X, and L3 has a negative optical power.
  • the fourth lens L4 has a meniscus shape and includes two surfaces: a surface facing the object surface side and a surface facing the image surface side, and the surface facing the object surface side is concave at the optical axis.
  • L4 can be used to correct on-axis chromatic aberration (or vertical chromatic aberration) and to correct magnification chromatic aberration.
  • L4 has a weaker positive or negative power.
  • the fifth lens L5 includes two surfaces: a surface facing the object surface side and a surface facing the image surface side, and the surface facing the object surface side is concave at the optical axis. Both surfaces can be aspheric to facilitate correction of spherical aberrations at the periphery of the lens.
  • the sixth lens L6 includes two surfaces: a surface facing the object surface side and a surface facing the image surface side.
  • the surface facing the object surface side is convex at the optical axis, and the surface facing the object surface side is outside the optical axis.
  • the position has an inverse curve point, the surface facing the image surface side is concave at the optical axis, and the surface facing the image surface side has an inverse curve point at a position other than the optical axis;
  • L6 has a negative optical power.
  • the seventh lens L7 includes two surfaces: a surface facing the object surface side and a surface facing the image surface side. Both surfaces can be aspheric. Specifically, the surface facing the object side is convex at the optical axis X, the surface facing the image side is concave at the optical axis X, and L7 has a negative optical power. Therefore, it is beneficial to ensure the back focus, perform astigmatism correction, and control the incident angle of the main ray to the image sensor. Specifically, in the surface facing the image plane side, there is an inverse curve point at a position away from the optical axis X, that is, the surface facing the image plane side is a concave surface in the vicinity of the optical axis X, and faces toward the peripheral portion.
  • the surface facing the object surface side also has an aspheric surface having a positive refractive power change at the peripheral portion. In this way, the peripheral portion of the lens of L7 distributes the required positive power to these two faces, thereby preventing a sharp change in the shape of L7.
  • the camera lens further includes an infrared filter IR, and the IR is disposed between the lens module and the image plane (image sensor), and is used to cut off and filter infrared light.
  • the camera lens may further include 6 independent lenses and an infrared filter; in the above two implementation modes (b), the camera lens may It further includes 7 independent lenses and an infrared filter.
  • each lens in the two implementation manners (a) and (b) may also be sufficient to satisfy the following conditional expression:
  • Vdl represents the Abbe number of the d-line of the sodium spectrum of the first lens L1;
  • Vd3 represents the Abbe number of the d-line of the sodium spectrum of the third lens L3;
  • Vd4 represents the Abbe number of the d-line of the sodium spectrum of the fourth lens L4;
  • f1 represents the focal distance of the first lens L1
  • f21 represents the focal distance of the surface of the diffractive optical element facing the object surface side and the diffractive surface
  • the Abbe numbers of the first lens L1 to the fourth lens L4 on the d-line are set within an appropriate range by using the conditional expressions (1) to (5), so that the on-axis color image can be corrected well.
  • Aberration and chromatic aberration of magnification are set within an appropriate range by using the conditional expressions (1) to (5), so that the on-axis color image can be corrected well.
  • Aberration and chromatic aberration of magnification it will be possible to easily select a suitable plastic material for each lens, thereby reducing the cost of the imaging lens.
  • the focal length ratio between the first lens L1 and the lens B in the second lens L2 is specified within an appropriate range, and the The focal length ratio between the lens A and the lens B is specified in an appropriate range, so that various aberrations can be corrected while shortening the overall optical length.
  • an embodiment of the present invention provides a camera module.
  • the camera module includes a camera lens and an image sensor according to the first aspect; wherein: the camera lens is used to form a light signal of a subject and is reflected to the image sensor; The optical signal for the subject is converted into an image signal and output, so as to realize the photographing or video recording function of the camera module.
  • an embodiment of the present invention provides a terminal.
  • the terminal includes a display screen and the camera module according to the second aspect, and the display screen is used to display an image captured by the camera module.
  • the camera module can be applied to smart phones, notebook computers, desktop computers, tablet computers, personal digital assistants (PDAs), wearable devices, augmented reality (AR) devices, virtual reality (Virtual Reality, VR) equipment, monitoring equipment and other end products, and because the camera lens has a lower total optical length TTL and a large aperture (such as F1.6, F1.5, F1.4, etc.), using a large aperture can Increase the amount of light entering the camera lens, thereby improving the clarity and color accuracy of imaging in night scenes or indoor scenes, and reducing the requirements for image stabilization of photos and videos, and meeting the design requirements of image sensors of different sizes, which is conducive to the realization of the terminal Miniaturization and high performance of products.
  • the implementation of the embodiments of the present invention can use the negative dispersion of diffractive optical elements to offset the positive dispersion of refractive elements (such as L1 and lens modules), thereby effectively reducing the chromatic aberration of the imaging; Group, can further balance monochromatic aberrations such as astigmatism, spherical aberration, and distortion.
  • a camera lens designed with such a structural frame will be able to design and achieve a large aperture (such as F1.44) for image sensors of different sizes (such as large-format image sensors of 1 / 2.8 to 1 / 2.3 inch, etc.) )
  • Camera lens to improve imaging quality in addition, the embodiments of the present invention can also meet the miniaturization requirements of camera lenses by optimizing the aspheric coefficient, thickness, lens material, refractive index and other parameters of each lens of the camera lens (such as TTL is 5.12mm). That is to say, the camera lens provided by the embodiment of the present invention can satisfy both the miniaturization and the high imaging quality, and also meet the requirements of the increased size of the image sensor.
  • the diffractive optical element in the camera lens can be made of plastic material
  • the first lens and lens module can also be made of plastic material, so it is not necessary to use low-dispersion glass materials or other special inorganic materials.
  • the embodiment of the invention also effectively reduces the cost of the camera lens and meets the needs of commercial applications.
  • FIG. 1 is a schematic structural diagram of a camera module according to an embodiment of the present invention
  • FIG. 2 is a schematic structural diagram of an optical diffraction element according to an embodiment of the present invention.
  • FIG. 3 is a schematic structural diagram of a camera lens and a lens module including 6 independent lenses and 1 IR according to an embodiment of the present invention
  • (A)-(d) in FIG. 4 are graphs of polychromatic light aberration curves in a visible spectrum in a range of 470-650 nm provided by an embodiment of the present invention.
  • FIG. 5 is a schematic diagram of simulation results of field curvature and distortion provided by an embodiment of the present invention.
  • FIG. 6 are graphs of polychromatic light aberration curves in a visible spectrum in a range of 470-650 nm provided by an embodiment of the present invention.
  • FIG. 7 is a schematic diagram of simulation results of field curvature and distortion provided by an embodiment of the present invention.
  • FIG. 8 is a schematic structural diagram of a camera lens and a lens module including 7 independent lenses and 1 IR according to an embodiment of the present invention
  • FIG. 9 is a schematic diagram of simulation results of longitudinal spherical aberration and distortion provided by an embodiment of the present invention.
  • Aberration refers to the deviation between the results obtained by non-paraxial ray tracing and the results obtained by paraxial ray tracing in an optical system, and the deviation from the ideal state of Gaussian optics (first-order approximation theory or paraxial ray). .
  • Aberrations are divided into two categories: chromatic aberration (also called chromatic aberration) and monochromatic aberration.
  • chromatic aberration also called chromatic aberration
  • monochromatic aberration is because the refractive index of the lens material is a function of wavelength.
  • Chromatic aberration is a kind of dispersion phenomenon.
  • the so-called dispersion phenomenon refers to the phenomenon that the speed of light or the refractive index in a medium changes with the wavelength of light waves.
  • the dispersion in which the refractive index of light decreases with increasing wavelength can be called normal dispersion, and the refractive index varies with
  • the dispersion that increases with increasing wavelength can be called negative dispersion (or negative anomalous dispersion).
  • Monochromatic aberration refers to aberrations that occur even in highly monochromatic light.
  • monochrome aberrations are divided into two types: “blur the imaging” and “distorte the imaging”.
  • the former category includes spherical aberration (spherical aberration), astigmatism, and the like, and the latter category includes field curvature (field curvature), distortion, and the like.
  • the camera module includes a camera lens and an image sensor.
  • the camera lens can be installed between the subject (object surface) and the image sensor (image surface).
  • the camera lens is used to form the image of the subject (that is, the light signal), and the image sensor is used to convert the image of the subject (that is, the optical signal) (Light signal) is converted into an image signal and output, so as to realize the camera or video function of the camera module.
  • the camera module can be applied to smart phones, notebook computers, desktop computers, tablet computers, personal digital assistants (PDAs), wearable devices, augmented reality (AR) devices, and virtual reality (Virtual Reality). , VR) equipment, monitoring equipment and other end products.
  • PDAs personal digital assistants
  • AR augmented reality
  • VR Virtual Reality
  • FIG. 1 is a schematic structural diagram of a camera module.
  • a camera lens is disposed between an image sensor and an object surface to form an image of a subject and reflect the image to the image sensor.
  • the side where the subject is located is called the object surface (or the object surface side)
  • the side where the image sensor is located is called the image surface (or the image surface side).
  • the camera lens along the optical axis X from the object surface side to the image surface side includes: a first lens L1, a second lens L2, a lens module composed of several lenses, and an infrared filter (IR filter), of which:
  • IR filter infrared filter
  • the first lens L1, L1 includes two surfaces facing away from each other, which can be called a first surface and a second surface, respectively.
  • the first surface faces the object surface side
  • the second surface faces the image surface side
  • the first surface and the second surface are both Aspheric surfaces are used to balance monochromatic aberrations such as spherical aberration and astigmatism.
  • L1 has a meniscus shape
  • the first surface has a convex shape at the optical axis X
  • the second surface has a concave shape at the optical axis X
  • L1 has a positive optical power.
  • the second lenses L2, L2 are diffractive optical elements. See FIG. 2, which is a schematic diagram of the structure of L2.
  • the diffractive optical element includes two different optical materials (two lens sheets) and two The optical diffraction grating between the two, specifically, the diffractive optical element is formed by sandwiching the optical diffraction grating with the two lens sheets, and L2 can be regarded as including three surfaces, which are respectively called a third surface and a fourth surface. And side 5.
  • the third and fifth surfaces are surfaces outside L2, and at least one of the third and fifth surfaces is an aspheric surface, so as to balance monochromatic aberrations such as spherical aberration and astigmatism.
  • the third surface faces the object surface side and is convex
  • the fifth surface faces the image surface side and is concave.
  • the fourth surface is a surface formed by a diffraction grating located inside L2, and the fourth surface may be a spherical surface or an aspherical surface.
  • the thickness of the lens A in the diffractive optical element is H1, and H1 satisfies: 0 ⁇ H1 ⁇ 0.5mm; the thickness of the lens B is H2, and H2 satisfies: 0 ⁇ H2 ⁇ 0.5mm.
  • the diffraction grating is arranged between the lens A and the lens B, and its grating height Gh satisfies 0 ⁇ Gh ⁇ 50um, that is, the thickness of the diffraction grating is between 0-50um, and the diffractive optical element has the property of negative dispersion.
  • the lens between the third surface and the fourth surface (may be referred to as the lens A) uses a low-dispersion thio resin material, and the range of the refractive index N1 of the material is 1.62 ⁇ N1 ⁇ 1.76; the fourth surface
  • the lens (can be referred to as the lens B) between the fifth surface and the fifth surface adopts a high-dispersion polycarbonate-based or modified alkane-based material, and the refractive index N2 of the material is in a range of 1.55 ⁇ N2 ⁇ 1.64; the material used for lens A
  • the range condition that the Abbe number V d 21 meets is 30 ⁇ Vd21 ⁇ 60
  • the range condition that the Abbe number V d 22 of the material used for the lens B satisfies is 20 ⁇ V d 22 ⁇ 40.
  • the Abbe numbers of lens A and lens B of the diffractive optical element and the Abbe number of the previous lens of the optical diffractive element that is, the Abbe number V d 1 of the material used for the first lens L1, the optical diffractive element
  • the following conditions can also be satisfied between the Abbe number of the latter lens (that is, the Abbe number V d 3 of the material used for the third lens L3 in the lens module): V d 1 ⁇ V d 21 ⁇ V d 22 ⁇ V d 3, or V d 1 ⁇ V d 21 ⁇ V d 22 ⁇ V d 3.
  • L2 has a positive power as a whole, and the power of L2 can be further divided into the power P1 of the lens A and the power P2 of the lens B.
  • P1 may be a positive power or a negative power to facilitate the dispersion of the first surface power
  • P2 may be a positive power or a negative power to compensate for aberrations.
  • P1 and P2 can both be positive power; for example, when P1 is positive power, P2 can be negative power, and the absolute value of P2 is less than P1; for example, when P1 is negative
  • the power of P2 can be positive, and the absolute value of P2 is greater than P1.
  • P1 and P2 can also satisfy the following relationship: -4 ⁇ P1 / P2 ⁇ 4; the power P1 and P2 of the diffractive optical element and the power P front (that is, the first The power of one lens L1) and the power P last of the diffractive optical element (the power of the third lens L3 in the lens module) can also satisfy the following conditions: Abs (P1 / P front ) ⁇ 4; Abs (P2 / P last ) ⁇ Abs (P1 / P front ), where Abs represents an absolute value function.
  • the lens module, the main optical axis of the lens module and the main optical axes of the first lens and the second lens coincide with each other.
  • the lens module is composed of N lenses, and each lens in the N lenses is arranged at an interval along the optical axis X, and the main optical axes of the lenses coincide with each other.
  • Each lens in the lens module has two lens surfaces, and the lens surface of each lens can be aspheric.
  • the lens module has a positive optical power in order to balance monochromatic aberrations such as spherical aberration and astigmatism.
  • N is an integer greater than or equal to 3 and less than or equal to 7, that is, the camera lens may include 5-9 independent lenses.
  • N may be 4 or 5, that is, the camera lens may include 6 or 7 independent lenses.
  • the infrared filter IR, IR is arranged between the lens module and the image sensor (image plane IM), and is used to cut off and filter infrared rays.
  • the aperture value Fno of the imaging lens is between 2.0 and 1.2.
  • all lenses in the camera lens can be made of plastic materials, among which L1 can specifically adopt cycloolefin-based materials with low dispersion; the lenses in the lens module can be designed according to the structure of the camera lens Choose conventional lens materials (such as polycarbonate-based high-dispersion materials or cycloolefin-based low-dispersion materials, etc.); the specific materials used for L2 refer to the description above, and will not be repeated here. .
  • the lens herein is an optical element having optical power near the optical axis.
  • the so-called “convex surface” and “concave surface” refer to the shape of the paraxial axis (near the optical axis).
  • the camera lens provided in the embodiment of the present invention includes a first lens, a diffractive optical element, and a lens module.
  • the negative dispersion of the diffractive optical element is used to cancel the positive dispersion of the refractive element (such as L1 and the lens module).
  • the lens module it can further balance monochromatic aberrations such as astigmatism, spherical aberration, and distortion.
  • a camera lens designed with such a structural frame will be able to design and achieve a large aperture (such as F1.5) for image sensors of different sizes (such as large-format image sensors of 1 / 2.8 to 1 / 2.3 inch, etc.) (F1.4, F1.4, etc.) to improve imaging quality;
  • the embodiments of the present invention can also satisfy the camera lens by optimizing the aspheric coefficient, thickness, lens material, refractive index and other parameters of each lens of the camera lens The need for miniaturization (that is, to achieve a smaller TTL). That is to say, the camera lens provided by the embodiment of the present invention can satisfy both the miniaturization and the high imaging quality, and also meet the requirements of the increased size of the image sensor.
  • the diffractive optical element in the camera lens can be made of plastic material
  • the first lens and lens module can also be made of plastic material, so it is not necessary to use low-dispersion glass materials or other special inorganic materials.
  • the embodiment of the invention also effectively reduces the cost of the camera lens and meets the needs of commercial applications.
  • the lens module is composed of 4 lenses, that is, the camera lens includes 6 independent lenses and an infrared filter, and the camera lens is sequentially along the optical axis X from the object surface side to the image surface side.
  • the third lens L3, L3 includes two surfaces, which can be referred to as a sixth surface and a seventh surface, respectively.
  • the sixth surface faces the object surface side
  • the seventh surface faces the image surface side.
  • At least one of the 6th and 7th surfaces is an aspheric surface in order to correct the residual aberrations and to reduce the astigmatic aberrations.
  • the sixth surface has a convex shape at the optical axis X
  • the seventh surface may have a convex shape or a concave shape at the optical axis X
  • L3 has a positive optical power.
  • the fourth lens L4 and L4 include two surfaces, which can be referred to as an eighth surface and a ninth surface, respectively.
  • the eighth surface faces the object surface side and the ninth surface faces the image surface side.
  • L4 has a meniscus shape, and the eighth surface has a concave shape at the optical axis X.
  • L4 can be used to correct chromatic aberration on the axis (a type of positional chromatic aberration) and to correct chromatic aberration of magnification. And correct distortion in image planes with low image heights up to about 70% image height.
  • L4 has a weaker positive or negative power.
  • the fifth lens L5 and L5 include two surfaces, which may be referred to as a tenth surface and an eleventh surface, respectively.
  • the tenth surface faces the object surface side
  • the eleventh surface faces the image surface side.
  • Both the 10th and 11th surfaces are aspheric to facilitate correction of spherical aberrations at the periphery of the lens; passing L5 is also beneficial to control the light emitted from L5 to an appropriate angle between low image height and maximum image height.
  • L5 has a meniscus shape
  • the tenth surface has a convex shape at the optical axis X
  • the eleventh surface has a concave shape at the optical axis X.
  • the position far from the optical axis X has an inverse curve point, that is, the shape of the peripheral portion of the 10th surface and / or the 11th surface is curved toward the object surface side.
  • the sixth lens L6 and L6 include two surfaces, which may be referred to as a twelfth surface and a thirteenth surface, respectively.
  • the twelfth surface faces the object surface side and the thirteenth surface faces the image surface side.
  • Both the twelfth surface and the thirteenth surface are aspheric.
  • the twelfth surface has a convex shape at the optical axis X
  • the thirteenth surface has a concave shape at the optical axis X
  • L6 has a negative power, which is beneficial Ensure back focus, correct astigmatism, and control the angle of incidence of the main ray toward the image sensor.
  • the thirteenth surface has an inverse curve point at a position far from the optical axis X, that is, the thirteenth surface is an aspheric surface that is concave near the optical axis X and changes to a convex surface toward the peripheral portion. Therefore, the lower the power of L6 is toward the peripheral part of the lens, the weaker the negative power, or the positive power changes gradually at the peripheral part.
  • the twelfth surface also has an aspheric surface with a positive refractive power change at the peripheral portion. In this way, the peripheral portion of the lens of L6 distributes the required positive power to these two faces, thereby preventing a sharp change in the shape of L6.
  • the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 together constitute a "lens module" in the embodiment of the present invention.
  • the infrared filter IR is disposed between the lens module and the image sensor, and is used to cut off and filter infrared rays.
  • all lenses in the camera lens can be made of plastic materials, among which L1 can be specifically made of cycloolefin-based materials with low dispersion; L3, L4, L5, and L6 can be based on the structure of the camera lens
  • L1 can be specifically made of cycloolefin-based materials with low dispersion
  • L3, L4, L5, and L6 can be based on the structure of the camera lens
  • the design situation selects the use of polycarbonate-based high-dispersion materials or cycloolefin-based low-dispersion materials; the specific materials used for L2 refer to the description above, and will not be repeated here.
  • anti-curve point refers to a point on an aspheric surface where the tangent plane intersects the optical axis perpendicularly.
  • the lens in the imaging lens described in the embodiment of FIG. 3 satisfies the following conditional expressions (1) to (7):
  • V d l represents the Abbe number of the first lens L1 to the d-line (that is, the d-line in the sodium spectrum, specifically the reference wavelength of 589.3 nm);
  • V d 21 represents the Abbe number of the lens A to the d line in the second lens L2;
  • V d 3 represents the Abbe number of the third lens L3 on the d line
  • V d 4 represents the Abbe number of the fourth lens L4 on the d line
  • f1 represents the focal length of the first lens L1
  • f21 represents the focal lengths of the third and fourth faces in the second lens L2 (that is, the optical diffraction element) (the focal length of the lens A );
  • f21 represents the focal length of the lens A in the second lens L2
  • f22 represents the focal length of the 4th and 5th surfaces in the second lens L2 (that is, the optical diffraction element) (lens B) Focal length);
  • the Abbe numbers of the first lens L1 to the fourth lens L4 on the d-line are set within an appropriate range by using the conditional expressions (1) to (5), so that the on-axis color image can be corrected well.
  • Aberration and chromatic aberration of magnification are set within an appropriate range by using the conditional expressions (1) to (5), so that the on-axis color image can be corrected well.
  • Aberration and chromatic aberration of magnification it will be possible to easily select a suitable plastic material for each lens, thereby reducing the cost of the imaging lens.
  • the focal length ratio between the first lens L1 and the lens B in the second lens L2 is specified within an appropriate range, and the The focal length ratio between the lens A and the lens B is specified in an appropriate range, so that various aberrations can be corrected while shortening the overall optical length.
  • the following further describes the relevant lens parameters of the camera lens in a specific application scenario, as shown in Table 1 below.
  • Table 1 the surface number The indicated faces correspond to the faces given above, that is, the face number "1" represents the aforementioned first face, the face number "2" represents the aforementioned second face, and the face number "3" represents the aforementioned third Face, and so on.
  • f represents the focal length of the entire camera lens;
  • Fno represents the F value of the camera lens;
  • ⁇ represents the half field angle of the camera lens;
  • TTL represents the optical full length of the camera lens.
  • Total Track Length refers to In the optical system, the distance between the lens located closest to the object surface side toward the object surface side (such as the first surface in the first lens herein) to the image plane (IM) is the distance from the optical axis X.
  • i represents the serial number of the lens surfaces counted from the object surface side (that is, corresponding to each lens surface in the imaging lens shown in the embodiment of FIG. 3)
  • r represents the radius of curvature of the lens surface
  • d represents the optical axis X
  • the distance between the lens surfaces, N d represents the refractive index of the lens facing the d-line, and V d represents the Abbe number of the lens facing the d-line.
  • the lens surface of each lens in the imaging lens is further described below.
  • the lens surface of the imaging lens may be formed by an aspheric surface.
  • the aspheric surface equation of the aspheric surface can be given by the following formula:
  • Z is the height parallel to the z axis in the lens surface
  • r is the radial distance from the vertex
  • c is the curvature of the surface at the vertex
  • K is the conic constant
  • a 4 , A 6 , A 8 , A 10 , A 12 indicates aspheric coefficients corresponding to the 4th order, 6th order, 8th order, 10th order, and 12th order, and an aspheric surface of an appropriate order can be selected according to needs.
  • FIG. 4 are graphs of polychromatic light aberration curves in a visible spectrum in a range of 470-650 nm according to an embodiment of the present invention.
  • different imaging planes Talmeridional image plane, Sagittal image plane Sag
  • at different fields of view (0mm, 1.2950mm, 2.590mm, 3.2380mm
  • different wavelengths (0.650um, 0.550um (0.470um)
  • the corresponding aberrations are less than 20um, that is, aberrations at different imaging planes, different fields of view, and different wavelengths are all well corrected.
  • FIG. 5 is a simulation result of Field Curvature and Distortion according to an embodiment of the present invention.
  • the fields of different wavelengths (0.650um, 0.550um, 0.470um) All of them can be well compensated.
  • the distortion of different wavelengths (0.650um, 0.550um, 0.470um) can be controlled within 3%. Therefore, the camera lens provided by the embodiment of the present invention meets the design application requirements, that is, the camera The lens can achieve a large aperture of F1.44 in the TTL range of 5.12mm, and the aberration can be optimized very well.
  • the camera lens provided in the embodiment of the present invention includes 6 lenses, and is a diffractive optical element at the L2 position.
  • the negative dispersion of the diffractive optical element is used to offset the positive of the refractive element (such as L1 and lens module). Dispersion, thereby effectively reducing the chromatic aberration of the imaging; on the other hand, the lens module can further balance monochromatic aberrations such as astigmatism, spherical aberration and distortion.
  • a camera lens designed with such a structural frame will be able to design and achieve a large aperture (such as F1.44) for image sensors of different sizes (such as large-format image sensors of 1 / 2.8 to 1 / 2.3 inch, etc.) )
  • Camera lens to improve imaging quality in addition, the embodiments of the present invention can also meet the miniaturization requirements of camera lenses by optimizing the aspheric coefficient, thickness, lens material, refractive index and other parameters of each lens of the camera lens (such as TTL is 5.12mm). That is to say, the camera lens provided by the embodiment of the present invention can satisfy both the miniaturization and the high imaging quality, and also meet the requirements of the increased size of the image sensor.
  • the diffractive optical element in the camera lens can be made of plastic material
  • the first lens and lens module can also be made of plastic material, so it is not necessary to use low-dispersion glass materials or other special inorganic materials.
  • the embodiment of the invention also effectively reduces the cost of the camera lens and meets the needs of commercial applications.
  • the embodiment of the present invention provides related lens parameters of the camera lens in another specific application scenario, as shown in Table 3 below.
  • the surface corresponding to the surface number corresponds to the surface given above
  • f represents the focal length of the entire camera lens
  • Fno represents the F value of the camera lens
  • ⁇ represents the half field angle of the camera lens
  • TTL represents the optics of the camera lens full length.
  • i represents the serial number of the lens surfaces counted from the object surface side (that is, corresponding to each lens surface in the imaging lens shown in the embodiment in FIG.
  • r represents the curvature radius of the lens surface
  • d represents the optical axis X
  • N d represents the refractive index of the lens facing the d-line
  • V d represents the Abbe number of the lens facing the d-line.
  • the lens surface of the camera lens may be formed by an aspheric surface.
  • the aspheric surface equation of the aspheric surface can be given by the following formula:
  • Z is the height parallel to the z axis in the lens surface
  • r is the radial distance from the vertex
  • c is the curvature of the surface at the vertex
  • K is the conic constant
  • a 4 , A 6 , A 8 , A 10 , A 12 indicates aspherical coefficients corresponding to the 4th order, 6th order, 8th order, 10th order, and 12th order, and an aspheric surface of an appropriate order can be selected according to needs.
  • FIG. 6 (a) to (d) of FIG. 6 are graphs of polychromatic light aberration curves in a visible spectrum in a range of 470-650 nm according to an embodiment of the present invention.
  • different imaging planes Talmeridional image plane, Sagittal image plane Sag
  • the corresponding aberrations are less than 20um, that is, aberrations at different imaging planes, different fields of view, and different wavelengths are all well corrected.
  • FIG. 7 is a simulation result of field curvature and distortion according to an embodiment of the present invention.
  • the fields of different wavelengths (0.650um, 0.550um, 0.470um) All of them can be well compensated.
  • the distortion of different wavelengths (0.650um, 0.550um, 0.470um) can be controlled within 4%. Therefore, the camera lens provided by the embodiment of the present invention meets the design application requirements, that is, the camera The lens can achieve a large aperture of F1.48 in the TTL range of 5.14mm, and the light aberration can be optimized very well.
  • the camera lens provided in the embodiment of the present invention includes 6 lenses, and is a diffractive optical element at the L2 position.
  • the negative dispersion of the diffractive optical element is used to offset the positive of the refractive element (such as L1 and lens module). Dispersion, thereby effectively reducing the chromatic aberration of the imaging; on the other hand, the lens module can further balance monochromatic aberrations such as astigmatism, spherical aberration and distortion. Therefore, a camera lens designed with such a structural frame will be able to design and achieve a large aperture (such as F1.48) for image sensors of different sizes (such as large-format image sensors such as 1 / 2.8 to 1 / 2.3 inches).
  • the embodiments of the present invention can also optimize the aspheric coefficient, thickness, lens material, refractive index and other parameters of each lens of the camera lens to meet the miniaturization needs of the camera lens (such as TTL is 5.14 mm). That is to say, the camera lens provided by the embodiment of the present invention can satisfy both the miniaturization and the high imaging quality, and also meet the requirements of the increased size of the image sensor.
  • the diffractive optical element in the camera lens can be made of plastic material
  • the first lens and lens module can also be made of plastic material, so it is not necessary to use low-dispersion glass materials or other special inorganic materials.
  • the embodiment of the invention also effectively reduces the cost of the camera lens and meets the needs of commercial applications.
  • the lens module is composed of 5 lenses, that is, the camera lens includes 7 independent lenses and an infrared filter, and the camera lens is sequentially along the optical axis X from the object surface side to the image surface side.
  • the third lens L3, L3 includes two surfaces, which can be referred to as a sixth surface and a seventh surface, respectively.
  • the sixth surface faces the object surface side
  • the seventh surface faces the image surface side.
  • At least one of the 6th and 7th surfaces is an aspheric surface in order to correct the residual aberrations and to reduce the astigmatic aberrations.
  • the sixth surface has a concave shape at the optical axis X
  • the seventh surface may have a convex shape or a concave shape at the optical axis X
  • L3 has a negative optical power.
  • the fourth lens L4 and L4 include two surfaces, which can be referred to as an eighth surface and a ninth surface, respectively.
  • the eighth surface faces the object surface side and the ninth surface faces the image surface side.
  • L4 has a meniscus shape, and the eighth surface has a concave shape at the optical axis X.
  • L4 can be used to correct on-axis chromatic aberration (or longitudinal chromatic aberration) and to correct magnification chromatic aberration.
  • L4 has a weaker positive or negative power.
  • the fifth lens L5, L5 includes two surfaces, which can be referred to as the 10th surface and the 11th surface, respectively.
  • the 10th surface faces the object surface side
  • the 10th surface has a concave shape at the optical axis X
  • the 11th surface faces the image surface side.
  • Both the 10th and 11th surfaces are aspherical to facilitate correction of spherical aberrations at the periphery of the lens.
  • the sixth lens L6 and L6 include two surfaces, which may be referred to as a twelfth surface and a thirteenth surface, respectively.
  • the twelfth surface faces the object surface side and the thirteenth surface faces the image surface side.
  • Both the twelfth surface and the thirteenth surface are aspheric.
  • the twelfth surface has a convex shape at the optical axis X, and the twelfth surface has a curve point outside the optical axis.
  • the thirteenth surface is at the optical axis X.
  • the concave shape, the thirteenth surface has an inverse curve point at a position other than the optical axis.
  • L6 has a negative power.
  • the seventh lens L7 and L7 include two surfaces, which can be referred to as a 14th surface and a 15th surface, respectively.
  • the 14th surface faces the object surface side and the 15th surface faces the image surface side.
  • Both the 14th and 15th surfaces are aspheric.
  • the 14th surface has a convex shape at the optical axis X
  • the 15th surface has a concave shape at the optical axis X
  • L7 has a negative optical power, which is beneficial to Ensure back focus, correct astigmatism, and control the angle of incidence of the main ray toward the image sensor.
  • the fifteenth surface has an inverse curve point at a position far from the optical axis X, that is, the fifteenth surface is an aspheric surface that is concave near the optical axis X and changes to a convex surface toward the peripheral portion. Therefore, the lower the power of L7 is toward the peripheral part of the lens, the weaker the negative power, or the positive power changes gradually at the peripheral part. By forming this aspheric surface, it is helpful to control the height of each image Incident angle of the main ray entering the image sensor. Specifically, the fourteenth surface also has an aspheric surface with a positive refractive power change at the peripheral portion. In this way, the peripheral portion of the lens of L7 distributes the required positive power to these two faces, thereby preventing a sharp change in the shape of L7.
  • the infrared filter IR is disposed between the camera lens and the image sensor (image plane IM), and is used to cut off and filter infrared rays.
  • all the lenses of the camera lens may be made of plastic materials, among which L1 may specifically adopt cycloolefin-based low-dispersion materials; L3, L4, L5, L6, and L7 may According to the structural design of the camera lens, high-dispersion materials of polycarbonate type or low-dispersion materials of cycloolefin type are selected; for the specific materials used for L2, refer to the description above, and the refractive index and ab The number is different from the related refractive index, Abbe number, and the like of the L2 in the embodiment of FIG. 3 (see the foregoing Table 1, Table 3, and Table 5 below), and details are not described herein again.
  • the lens in the imaging lens described in the embodiment of FIG. 8 satisfies the following conditional expressions (1) to (7):
  • V d l represents the Abbe number of the first lens L1 to the d-line (that is, the d-line in the sodium spectrum, specifically the reference wavelength of 589.3 nm);
  • V d 21 represents the Abbe number of the lens A to the d line in the second lens L2;
  • V d 3 represents the Abbe number of the third lens L3 on the d line
  • V d 4 represents the Abbe number of the fourth lens L4 on the d line
  • f21 represents the focal length of the lens A in the second lens L2
  • f22 represents the focal length of the fourth and fifth surfaces in the second lens L2 (the focal length of the lens B);
  • the Abbe numbers of the first lens L1 to the fourth lens L4 on the d-line are set within an appropriate range by using the conditional expressions (1) to (5), so that the on-axis color image can be corrected well.
  • Aberration and chromatic aberration of magnification are set within an appropriate range by using the conditional expressions (1) to (5), so that the on-axis color image can be corrected well.
  • Aberration and chromatic aberration of magnification it will be possible to easily select a suitable plastic material for each lens, thereby reducing the cost of the imaging lens.
  • the focal length ratio between the first lens L1 and the lens B in the second lens L2 is specified within an appropriate range, and the The focal length ratio between the lens A and the lens B is specified in an appropriate range, so that various aberrations can be corrected while shortening the overall optical length.
  • the lens surface of the camera lens may be formed by an aspheric surface.
  • the aspheric surface equation of the aspheric surface can be given by the following formula:
  • Z is the height parallel to the z axis in the lens surface
  • r is the radial distance from the vertex
  • c is the curvature of the surface at the vertex
  • K is the conic constant
  • a 4 , A 6 , A 8 , A 10 , A 12 , A 14 and A 16 represent aspheric coefficients.
  • FIG. 9 is a simulation result of longitudinal spherical aberration and distortion in the embodiment of the present invention.
  • different wavelengths (0.650um, 0.550um, 0.470um)
  • the vertical spherical aberration can be well compensated.
  • the distortion of different wavelengths (0.650um, 0.550um, 0.470um) can be controlled within 2%. Therefore, the camera lens provided by the embodiment of the present invention meets the design and application requirements. That is, the camera lens can achieve a large aperture of F1.45 within a TTL range of 5.60mm, and the light chromatic aberration can be optimized very well.
  • the camera lens provided in the embodiment of the present invention includes 7 lenses and is a diffractive optical element at the L2 position.
  • the negative dispersion of the diffractive optical element is used to offset the positive of the refractive element (such as L1 and lens module). Dispersion, thereby effectively reducing the chromatic aberration of the imaging; on the other hand, the lens module can further balance monochromatic aberrations such as astigmatism, spherical aberration and distortion. Therefore, a camera lens designed with such a structural frame will be able to design an image with a large aperture (such as F1.45) for image sensors of different sizes (such as large-format image sensors from 1 / 2.8 inches to 1 / 2.3 inches).
  • the embodiment of the present invention can also meet the miniaturization requirements of the camera lens by optimizing the aspheric coefficient, thickness, lens material, refractive index and other parameters of each lens of the camera lens (for example, the TTL is 5.60mm) . That is to say, the camera lens provided by the embodiment of the present invention can satisfy both the miniaturization and the high imaging quality, and also meet the requirements of the increased size of the image sensor.
  • the diffractive optical element in the camera lens can be made of plastic material
  • the first lens and lens module can also be made of plastic material, so it is not necessary to use low-dispersion glass materials or other special inorganic materials.
  • the embodiment of the invention also effectively reduces the cost of the camera lens and meets the needs of commercial applications.
  • the diffractive optical element is described as appearing at the L2 position of the camera lens, in a possible implementation manner, the diffractive optical element may also appear at other positions (for example, L3, L4, L5, etc.), the implementation process can refer to the description above, and will not be repeated here.
  • the diffractive optical elements are all described in the form of one, in a possible implementation manner, there are also multiple diffractive optical elements (for example, 2, 3, 4 ... etc.) Etc.), the implementation process can refer to the above description, which will not be repeated here.
  • the embodiment of the present invention further provides a lens module, the lens module includes a camera lens as described above, and an image sensor; wherein: the camera lens is used to form light of a subject The signal is reflected to the image sensor; the image sensor is used to convert an optical signal corresponding to a subject into an image signal.
  • an embodiment of the present invention further provides a terminal, and the terminal is mounted with the lens module as described above.
  • the camera lens according to each embodiment is applied to a smartphone, a notebook computer, a desktop computer, a tablet computer, a Personal Digital Assistant (PDA), a wearable device, and Augmented Reality (AR).
  • Equipment, virtual reality (VR) equipment, monitoring equipment and other end products can meet the increasing requirements of image sensor format, and because the camera lens has a lower total optical length TTL and a large aperture (such as F1. 6.F1.5, F1.4, etc.), the use of a large aperture can increase the amount of light entering the camera lens, thereby improving the imaging clarity and color accuracy in night scenes or indoor scenes, and reducing the anti-shake requirements for photographs and videos, and Meet the design needs of image sensors of different sizes, which is conducive to achieving miniaturization and high performance of this end product.

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Abstract

一种摄像镜头、摄像模组及终端，摄像镜头沿光轴(X)从物面到像面包括第一透镜(L1)、衍射光学元件(L2)和透镜模组，第一透镜(L1)朝向物面侧的面在光轴(X)处为凸面，朝向像面侧的面在光轴(X)处为凹面，具有正的光焦度；衍射光学元件(L2)具有正的光焦度且具有负色散性质，其包括朝向物面侧的面、朝向像面侧的面、以及位于这两个面之间的衍射面，朝向物面侧的面在光轴(X)处为凸面，朝向像面侧的面在光轴(X)处为凹面；透镜模组包括N枚透镜(L3-L7)，N枚透镜(L3-L7)中的各个透镜(L3-L7)的朝向物面侧的面和朝向像面侧的面中至少有一个面为非球面，透镜模组具有正的光焦度。摄像镜头可以满足小型化和高成像质量要求，以及满足图像传感器幅面增大的需求。

Description

摄像镜头、摄像模组及终端 技术领域
本发明涉及光学成像技术领域，尤其涉及摄像镜头、摄像模组及终端。
背景技术
近年来，随着智能终端技术的发展，拍摄功能已经成为很多智能终端(如智能手机)的必备功能特性。以智能手机为例，摄像镜头作为智能手机的摄像模块的核心组件，其技术得到飞速的发展。随着时间和技术的发展，用户对智能手机的小型化和拍摄功能的高成像质量(大光圈)的需求日益增加。
通常来说，高成像质量的评估参数包括了色差、单色像差(包括像散、畸变、球面像差等)等等像差的光学指标，为了获得高成像质量，需要足够大的光学空间来平衡不同的像差，可通过调整摄像镜头中透镜的非球面系数和透镜距离等来平衡单色像差，从而得到大光圈。但是在大光圈的情况下，色差通常难以控制。现有技术中消除色差通常有以下两种方法：
一种方法是选择低色散的光学材料来制成透镜，从而有利于消除色差。比如，采用玻璃材料制成的透镜的色散都比较低，而塑料材料制成的透镜的色散都比较大，但是，若采用玻璃材料来制成透镜，其加工工艺要求非常高，且成本较昂贵，极大限制了其在智能手机的镜头上应用。
另一种方法是增加摄像镜头中的透镜枚数，通过增加若干枚透镜来更好地消除色差。比如，当前较高端的摄像镜头普遍采用6枚透镜组合，而很多企业为了进一步消除色差来提升成像质量，都在积极开发7枚或者8枚透镜组合的技术。然而，这种方法容易受到智能手机尺寸的限制，与智能手机轻薄化的趋势相矛盾。
另外，现有技术中，智能手机的摄像镜头主要是针对1/3.2英寸～1/3.0英寸的图像传感器来进行设计，整体光学总长(Total Track Length，TTL)通常约为5.0mm。而随着智能手机硬件性能的演进，更大尺寸、更高的分辨率的图像传感器(如1/2.8英寸～1/2.3英寸)开始广泛被采用，随着图像传感器幅面越来越大，当前的主流摄像镜头设计方案势必会导致TTL参数进一步增大。而由于智能手机尺寸的限制，摄像镜头的总厚度和面积难以进一步增加，同时满足小型化和高成像质量的困难会更大。
综上所述，对摄像镜头的设计而言，既要满足小型化和高成像质量要求，又要满足图像传感器幅面增大的需求，目前来说是一种严峻的技术挑战。
发明内容
本发明实施例提供了摄像镜头、摄像模组及终端，该摄像镜头可以满足小型化和高成像质量要求，以及满足图像传感器幅面增大的需求。
第一方面，本发明实施例提供了一种摄像镜头。该摄像镜头沿光轴从物面到像面包括：第一透镜、第二透镜和透镜模组，第二透镜为衍射光学元件，衍射光学元件位于第一透镜和透镜模组之间，且与第一透镜和透镜模组相隔离，所述第一透镜、所述衍射光学元件和位于所述透镜模组内的N个透镜的光轴互为重合。其中：
第一透镜，包括相背离的两个面，其中朝向物面侧的面在光轴处为凸面，朝向像面侧的面在光轴处为凹面；所述第一透镜具有正的光焦度；
衍射光学元件，包括两层不同的光学材料以及位于两者之间的光学衍射光栅，也就是说所述衍射光学元件包括朝向物面侧的面、朝向像面侧的面、以及位于这两个面之间的衍射面；其中，朝向物面侧的面在光轴处为凸面，朝向像面侧的面在光轴处为凹面；所述衍射光学元件具有正的光焦度；由于衍射光学元件具有负反常色散(简称负色散)的性质，因而可用该衍射光学元件来抵消折射元件(如L1、透镜模组)的正色散。
透镜模组，包括沿光轴间隔排列的N枚透镜，N为大于或等于3且小于或等于7的整数；所述N枚透镜中的各个透镜的朝向物面侧的面和朝向像面侧的面中，至少有一个面为非球面，所述透镜模组具有正的光焦度，从而用以平衡球差、像散等单色像差。
可以看到，本发明实施例提供的摄像镜头一方面能够利用衍射光学元件的负色散来抵消折射元件(如L1、透镜模组)的正色散，从而有效降低了成像的色差；另一方面可通过透镜模组，能进一步平衡像散、球差、畸变等单色像差。所以，采用这样的结构框架设计的摄像镜头，将能够针对不同尺寸的图像传感器(如1/2.8英寸～1/2.3英寸等等的大幅面的图像传感器)来设计实现大光圈的摄像镜头，提高成像质量；另外，基于实施本发明实施例的摄像镜头的上述结构特点，将能够通过优化摄像镜头的各个透镜的物理参数(如非球面系数、厚度、透镜材料、折射率等)来实现较小的TTL，满足摄像镜头的小型化需求。也就是说，本发明实施例提供的摄像镜头既能同时满足小型化和高成像质量，又能满足图像传感器幅面增大的需求。
基于第一方面，在可能的实施方式中，所述摄像镜头的光圈值Fno(F值)在2.0～1.2之间，如F1.6、F1.5、F1.4等。通过采用大光圈可以提升摄像镜头的进光量，从而提升夜景或室内场景中的成像清晰度、色彩准确度，并降低对拍照录像的防抖要求。
基于第一方面，在可能的实施方式中，摄像镜头中所有的透镜均可由塑料材料构成，所以，实施本发明实施例还有利于降低摄像镜头的成本。具体的，L1可具体采用环烯烃类的低色散的材料；透镜模组中的透镜可以根据摄像镜头的结构设计情况来选择采用常规的镜头材料(如聚碳酸酯类的高色散的材料，或者环烯烃类的低色散的材料，等等)。所述衍射光学元件中，朝向物面侧的面和衍射面之间的透镜材料采用低色散的硫代树脂材料，该材料的折射率N1的范围条件为1.62<N1<1.76；衍射面和朝向像面侧的面之间的透镜材料采用高色散的聚碳酸酯类或者改性烷烃类材料，该材料的折射率N2的范围条件为1.55<N2<1.64。
基于第一方面，在可能的实施方式中，所述衍射光学元件中，位于朝向物面侧的面和衍射面之间的材料的光焦度为P1，位于朝向像面侧的面和衍射面之间的材料的光焦度为P2，P1和P2满足条件式：-4<P1/P2<4。衍射光学元件的光焦度P1、P2与衍射光学元件的前一透镜的光焦度P front(即第一透镜L1的光焦度)、衍射光学元件的后一透镜的光焦度P last(即透镜模组中的第三透镜L3的光焦度)之间还可满足以下条件：Abs(P1/P front)<4；Abs(P2/P last)<Abs(P1/P front)，其中，Abs表示绝对值函数。由于采取了两个光焦度对光焦度进行分散，可以降低单镜片的对光线的折射要求，从而能够降低由于单一大光焦度带来的球面像差、像散、畸变等单色像差，实现在较小的光学总长下实现超大的光圈。
基于第一方面，在可能的实施方式中，所述衍射光学元件中，位于朝向物面侧的面和衍射面之间的材料对钠光谱的d线的阿贝数为V d21，位于朝向像面侧的面和衍射面之间的材料对钠光谱的d线的阿贝数为V d22，V d21和V d22分别满足以下条件式：30<V d21<60；20<V d22<40。
具体实现中，衍射光学元件的透镜A、透镜B的阿贝数与光学衍射元件的前一透镜的阿贝数(即第一透镜L1所采用材料的阿贝数V d1)、光学衍射元件的后一透镜的阿贝数(即透镜模组中的第三透镜L3所采用材料的阿贝数Vd3)之间还可满足以下条件：V d1〉V d21〉V d22〉V d3，或者V d1<V d21<V d22<V d3。
基于第一方面，在可能的实施方式中，该衍射光学元件中的透镜A厚度为H1，H1满足：0＜H1<0.5mm；透镜B的厚度为H2，H2满足：0＜H2<0.5mm。衍射光栅设置在透镜A和透镜B之间，其光栅高度Gh满足0＜Gh<50um，亦即衍射光栅的厚度在0～50um之间。
基于第一方面，在可能的实施方式中，所述衍射光学元件朝向物面侧的面和朝向像面侧的面中，至少有一个面为非球面，以便于平衡球差、像散等单色像差。例如，具体实现中，所述衍射光学元件朝向物面侧的面和朝向像面侧的面皆为非球面。
基于第一方面，在可能的实施方式中，第一透镜L1的两个面和透镜模组中所有透镜的面可皆为非球面，从而更好地平衡球差、像散等单色像差。
基于本发明实施例的上述结构框架，下面描述两种摄像镜头的实现方式。
(a)在一实现方式中，所述透镜模组包括如下4个透镜：第三透镜、第四透镜、第五透镜和第六透镜，也就是说，摄像镜头至少包括6枚独立透镜：第一透镜、第二透镜(即衍射光学元件)、第三透镜、第四透镜、第五透镜和第六透镜。其中：
所述第三透镜L3包括两个面：朝向物面侧的面和朝向像面侧的面，这两个面中至少一个面为非球面，以便于校正残余的像差，并且起着缩小像散差的作用。具体的，朝向物面侧的面在在光轴X处为凸面形状，朝向物面侧的面在光轴X处可为凸面形状也可为凹面形状，第三透镜具有正的光焦度。
所述第四透镜L4呈弯月形，包括两个面：朝向物面侧的面和朝向像面侧的面。朝向物面侧的面在光轴处为凹面，L4可用于校正轴上色像差(属于位置色像差的一种)以及良好地校正倍率色像差，并且校正低像高至约70％像高的像面中的畸变。L4具有较弱的正光焦度或负的光焦度。
所述第五透镜L5包括两个面：朝向物面侧的面和朝向像面侧的面，这两个面可皆采用非球面，以便于校正透镜周边部的球面像差；通过L5还有利于实现将从L5射出的光线在低像高至最大像高之间控制成适当的角度。具体的，L5呈弯月形的形状，物面侧的面在光轴X处为凸面形状，朝向像面侧的面在光轴X处为凹面形状，此外，这两个面的至少一个面中，在远离光轴X的位置具有一个反曲线点，即，该面的周边部的形状呈现出向物面侧的方向弯曲。
所述第六透镜L6包括两个面：朝向物面侧的面和朝向像面侧的面，这两个面可皆采用非球面，具体的，朝向物面侧的面在光轴X处为凸面形状，朝向像面侧的面在光轴X处为凹面形状，L6具有负的光焦度，从而有利于确保后焦距、进行像散的校正以及控制向图像 传感器的主光线入射角度。具体的，在朝向像面侧的面中，在远离光轴X的位置具有一个反曲线点，即，朝向像面侧的面为在光轴X的附近为凹面、随着朝向周边部而向凸面变化的非球面。因此，L6的光焦度越朝向透镜的周边部，其负的光焦度越弱，或在周边部逐渐向正的光焦度变化，通过形成这种非球面，有利于控制各像高处向图像传感器射入的主光线的入射角度。具体的，朝向物面侧的面也具有在周边部向正的光焦度变化的非球面。这样，L6的透镜的周边部将所需的正光焦度分配到这两个面，从而防止L6的形状发生急剧变化。
(b)在又一实现方式中，所述透镜模组包括如下5个透镜：第三透镜、第四透镜、第五透镜、第六透镜和第七透镜，也就是说，摄像镜头至少包括7枚独立透镜：第一透镜、第二透镜(即衍射光学元件)、第三透镜、第四透镜、第五透镜、第六透镜和第七透镜。其中：
所述第三透镜L3包括两个面：朝向物面侧的面和朝向像面侧的面，这两个面中的至少一个面为非球面，以便于校正残余的像差，并且起着缩小像散差的作用。具体的，朝向物面侧的面在在光轴X处为凹面形状，朝向像面侧的面在光轴X处可为凸面形状也可为凹面形状，L3具有负的光焦度。
所述第四透镜L4呈弯月形，包括两个面：朝向物面侧的面和朝向像面侧的面，朝向物面侧的面在光轴处为凹面。，L4可用于校正轴上色像差(或称纵向色像差)以及良好地校正倍率色像差。L4具有较弱的正光焦度或负的光焦度。
所述第五透镜L5包括两个面：朝向物面侧的面和朝向像面侧的面，朝向物面侧的面在光轴处为凹面。这两个面可皆采用非球面，以便于校正透镜周边部的球面像差。
所述第六透镜L6包括两个面：朝向物面侧的面和朝向像面侧的面，朝向物面侧的面在光轴处为凸面，且朝向物面侧的面在光轴以外的位置具有反曲线点，朝向像面侧的面在光轴处为凹面，且朝向像面侧的面在光轴以外的位置具有反曲线点；L6具有负的光焦度。
所述第七透镜L7包括两个面：朝向物面侧的面和朝向像面侧的面。这两个面可皆采用非球面，具体的，朝向物面侧的面在光轴X处为凸面形状，朝向像面侧的面在光轴X处为凹面形状，L7具有负的光焦度，从而有利于确保后焦距、进行像散的校正以及控制向图像传感器的主光线入射角度。具体的，在朝向像面侧的面中，在远离光轴X的位置具有一个反曲线点，即，朝向像面侧的面为在光轴X的附近为凹面、随着朝向周边部而向凸面变化的非球面。因此，L7的光焦度越朝向透镜的周边部，其负的光焦度越弱，或在周边部逐渐向正的光焦度变化，通过形成这种非球面，有利于控制各像高处向图像传感器射入的主光线的入射角度。具体的，朝向物面侧的面也具有在周边部向正的光焦度变化的非球面。这样，L7的透镜的周边部将所需的正光焦度分配到这两个面，从而防止L7的形状发生急剧变化。
基于第一方面，在可能的实施方式中，所述摄像镜头还包括红外滤光片IR，IR配置在透镜模组与像面(图像传感器)之间，用于实现对红外线进行截止、滤光等。举例来说，在上述两种实现方式(a)中，所述摄像镜头可进一步包括6枚独立透镜和1枚红外滤光片；在上述两种实现方式(b)中，所述摄像镜头可进一步包括7枚独立透镜和1枚红外滤光片。
基于第一方面，在可能的实施方式中，两种实现方式(a)和(b)中的各透镜还可满 足以下条件式：
(1)50<V dl<60；其中，Vdl表示第一透镜L1对钠光谱的d线的阿贝数；
(2)50<V d3<60；其中，Vd3表示第三透镜L3对钠光谱的d线的阿贝数；
(3)20<V d4<30；其中，Vd4表示第四透镜L4对钠光谱的d线的阿贝数；
(4)1<f1/f21<5；其中，f1表示第一透镜L1的焦距；f21表示所述衍射光学元件朝向物面侧的面和衍射面的焦距；
(5)f21/f22<1；其中，f22表示所述衍射光学元件朝向像面侧的面和衍射面的焦距。
本发明实施例通过上述条件式(1)～(5)，分别将第一透镜L1～第四透镜L4对d线的阿贝数规定在适当的范围内，从而能够良好地校正轴上色像差及倍率色像差。此外，根据上述规定的范围内，将能够轻易地为各个透镜选择合适的塑料材料，从而实现降低了摄像镜头的成本。
本发明实施例通过上述条件式(6)和(7)，将第一透镜L1与第二透镜L2中的透镜B之间的焦距比例规定在适当的范围内，以及将第二透镜L2中的透镜A与透镜B之间的焦距比例规定在适当的范围内，从而能够在缩短光学全长的同时实现校正各种像差。
第二方面，本发明实施例提供了一种摄像模组。所述摄像模组包括如第一方面所述的摄像镜头以及图像传感器；其中：所述摄像镜头用于形成被摄体的光信号并反映到所述图像传感器；所述图像传感器用于将对应于被摄体的光信号变换为图像信号并输出，以便于实现摄像模组的拍照或录像功能。
第三方面，本发明实施例提供了一种终端。所述终端包括显示屏和如第二方面所述的摄像模组，所述显示屏用于显示所述摄像模组拍摄的图像。也就是说所述摄像模组可应用于智能手机、笔记本电脑、台式电脑、平板电脑、个人数字助理(Personal Digital Assistant，PDA)、可穿戴设备、增强现实(Augmented Reality，AR)设备、虚拟现实(Virtual Reality，VR)设备、监控设备等终端产品中，且由于摄像镜头具有较低的光学总长TTL和超大的光圈(如F1.6、F1.5、F1.4等)，采用大光圈可以提升摄像镜头的进光量，从而提升夜景或室内场景中的成像清晰度、色彩准确度，并降低对拍照录像的防抖要求，并满足不同尺寸的图像传感器的设计需求，从而有利于实现该终端产品的小型化和高性能化。
可以看到，实施本发明实施例一方面可利用衍射光学元件的负色散来抵消折射元件(如L1、透镜模组)的正色散，从而有效降低了成像的色差；另一方面可通过透镜模组，能进一步平衡像散、球差、畸变等单色像差。所以，采用这样的结构框架设计的摄像镜头，将能够针对不同尺寸的图像传感器(如1/2.8英寸～1/2.3英寸等等的大幅面的图像传感器)来设计实现超大光圈(如F1.44)的摄像镜头，提高成像质量；另外，本发明实施例还能够通过优化摄像镜头的各个透镜的非球面系数、厚度、透镜材料、折射率等参数来满足摄像镜头的小型化需求(如TTL为5.12mm)。也就是说，本发明实施例提供的摄像镜头既能同时满足小型化和高成像质量，又能满足图像传感器幅面增大的需求。此外，由于摄像镜头中的衍射光学元件可采用塑料材料制成，第一透镜和透镜模组也可采用塑料材料制成，从而不需要采用低色散的玻璃材料或者其他特殊的无机材料，所以实施本发明实施例还有效降低了摄像镜头的成本，满足商业应用需求。
附图说明
图1是本发明实施例提供的一种摄像模组的结构框架示意图；
图2是本发明实施例提供的一种光学衍射元件的结构示意图；
图3示出了本发明实施例的一种包含6枚独立透镜和1枚IR的摄像镜头以及透镜模组的结构示意图；
图4中的(a)～(d)是本发明实施例提供的在470-650nm范围的可见光谱上的多色光线像差曲线图；
图5是本发明实施例提供的对场曲和畸变的仿真结果示意图；
图6中的(a)～(d)是本发明实施例提供的在470-650nm范围的可见光谱上的多色光线像差曲线图；
图7是本发明实施例提供的对场曲和畸变的仿真结果示意图；
图8示出了本发明实施例的一种包含7枚独立透镜和1枚IR的摄像镜头以及透镜模组的结构示意图；
图9是本发明实施例提供的对纵向球差和畸变的仿真结果示意图。
具体实施方式
下面结合本发明实施例中的附图对本发明实施例进行描述。
本发明的实施方式部分使用的术语仅用于对本发明的具体实施例进行解释，而非旨在限定本发明。首先解释本发明实施例所涉及的像差概念。像差(aberration)是指光学***中，由非近轴光线追迹所得的结果和近轴光线追迹所得的结果不一致，与高斯光学(一级近似理论或近轴光线)的理想状况的偏差。像差又分为两大类：色差(chromatic aberration，或称色像差)与单色像差(monochromatic aberration)。色差是由于透镜材料的折射率是波长的函数，不同波长的光通过透镜时因折射率不同而产生的像差，色差又可分为位置色像差和倍率色像差两种。色差是一种色散现象，所谓色散现象是指介质中的光速或折射率随光波波长变化的现象，光的折射率随着波长的增加而减小的色散可称为正常色散，而折射率随波长的增加而增加的色散可称为负色散(或称负反常色散)。单色像差是指即使在高度单色光时也会产生的像差，按产生的效果，单色像差又分成“使成像模糊”和“使成像变形”两类。前一类有球面像差(spherical aberration，可简称球差)、像散(astigmatism)等，后一类有像场弯曲(field curvature，可简称场曲)、畸变(distortion)等。
下面介绍本发明实施例提供的一种摄像模组，该摄像模组包括摄像镜头和图像传感器。该摄像镜头可安装被摄体(物面)与图像传感器(像面)之间，摄像镜头用于形成被摄体的像(即光信号)，图像传感器用于将被摄体的像(即光信号)转换为图像信号并输出，以便于实现摄像模组的拍照或录像功能。所述摄像模组可应用于智能手机、笔记本电脑、台式电脑、平板电脑、个人数字助理(Personal Digital Assistant，PDA)、可穿戴设备、增强现实(Augmented Reality，AR)设备、虚拟现实(Virtual Reality，VR)设备、监控设备等终端产品。
参见图1，图1为摄像模组的结构框架示意图，如图1所示，摄像镜头设置于图像传感器与物面之间，以形成被摄体的像并反映到图像传感器，故可将被摄体所在一侧称为物 面(或称物面侧)，图像传感器所在一侧称为像面(或称像面侧)。进一步的，摄像镜头沿光轴X从物面侧到像面侧包括：第一透镜L1、第二透镜L2、由若干枚透镜组成的透镜模组以及红外滤光片(IR Filter)，其中：
第一透镜L1，L1包括相背离的两个面，可分别称为第1面和第2面，第1面朝向物面侧，第2面朝向像面侧，第1面和第2面皆采用非球面，以便于平衡球差、像散等单色像差。具体的，L1呈弯月形的形状，第1面在光轴X处为凸面形状，第2面在光轴X处为凹面形状，L1具有正的光焦度。
第二透镜L2，L2为衍射光学元件，参见图2，图2为L2的结构示意图，如图2所示，该衍射光学元件包括两层不同的光学材料(两个透镜片)以及位于两者之间的光学衍射光栅，具体的，该衍射光学元件由所述两个透镜片夹合所述光学衍射光栅而形成，L2可视为包括三个面，分别称为第3面、第4面和第5面。第3面和第5面为位于L2外部的面，第3面和第5面中至少一个面采用非球面，以便于平衡球差、像散等单色像差。其中，第3面朝向物面侧且为凸面，第5面朝向像面侧且为凹面。第4面为位于L2内部的衍射光栅所形成的面，第4面可以采用球面也可以采用非球面。
具体实施例中，该衍射光学元件中的透镜A厚度为H1，H1满足：0＜H1<0.5mm；透镜B的厚度为H2，H2满足：0＜H2<0.5mm。衍射光栅设置在透镜A和透镜B之间，其光栅高度Gh满足0＜Gh<50um，亦即衍射光栅的厚度在0～50um之间，该衍射光学元件具有负色散的性质。
具体实施例中，第3面和第4面之间的透镜(可简称透镜A)采用低色散的硫代树脂材料，该材料的折射率N1的范围条件为1.62<N1<1.76；第4面和第5面之间的透镜(可简称透镜B)采用高色散的聚碳酸酯类或者改性烷烃类材料，该材料的折射率N2的范围条件为1.55<N2<1.64；透镜A所采用材料的阿贝数V d21满足的范围条件为30<Vd21<60，透镜B所采用材料的阿贝数V d22满足的范围条件为20<V d22<40。具体实现中，衍射光学元件的透镜A、透镜B的阿贝数与光学衍射元件的前一透镜的阿贝数(即第一透镜L1所采用材料的阿贝数V d1)、光学衍射元件的后一透镜的阿贝数(即透镜模组中的第三透镜L3所采用材料的阿贝数V d3)之间还可满足以下条件：V d1〉V d21〉V d22〉V d3，或者V d1<V d21<V d22<V d3。
具体实施例中，L2从整体上来说具有正的光焦度，L2的光焦度又可分为透镜A的光焦度P1以及透镜B的光焦度P2。其中，P1可以是正的光焦度，也可以是负的光焦度，以便于分散第一个面的光焦度，P2可以是正光焦度或者负光焦度，以便于补偿像差。例如，P1和P2可以皆为正的光焦度；又例如，当P1是正的光焦度时，P2可为负的光焦度，且P2的绝对值小于P1；又例如，当P1是负的光焦度时，P2可为正的光焦度，且P2的绝对值大于P1。具体实现中，P1和P2还可满足下述关系：-4<P1/P2<4；衍射光学元件的光焦度P1、P2与衍射光学元件的前一透镜的光焦度P front(即第一透镜L1的光焦度)、衍射光学元件的后一透镜的光焦度P last(即透镜模组中的第三透镜L3的光焦度)之间还可满足以下条件：Abs(P1/P front)<4；Abs(P2/P last)<Abs(P1/P front)，其中，Abs表示绝对值函数。由于采取了两个光焦度对光焦度进行分散，可以降低单镜片的对光线的折射要求，从而能够降低由于单一大光焦度带来的球面像差、像散、畸变等单色像差，实现在较小的光学总长下实 现超大的光圈。
透镜模组，透镜模组的主光轴(main optical axis)与第一透镜、第二透镜的主光轴相互重合。透镜模组由N枚透镜构成，该N枚透镜中的各个透镜沿光轴X间隔排列，各个透镜的主光轴相互重合。透镜模组中的每个透镜皆具有两个透镜面，每个透镜的透镜面皆可为非球面。所述透镜模组具有正的光焦度，以便于平衡球差、像散等单色像差。
其中，N为大于或等于3且小于或等于7的整数，也就是摄像镜头可包括5-9枚独立透镜。具体实施例中，N可以是4或5，也就是摄像镜头可包括6枚或7枚独立透镜，其详细的实施方式可参考后文的描述。
红外滤光片IR，IR配置在透镜模组与图像传感器(像面IM)之间，用于实现对红外线进行截止、滤光等。
另外，本发明实施例中，所述摄像镜头的光圈值Fno在2.0～1.2之间。
需要说明的是，在具体实现中，摄像镜头中所有的透镜均可由塑料材料构成，其中，L1可具体采用环烯烃类的低色散的材料；透镜模组中的透镜可以根据摄像镜头的结构设计情况来选择采用常规的镜头材料(如聚碳酸酯类的高色散的材料，或者环烯烃类的低色散的材料，等等)；L2所采用的具体材料参考上文的说明，这里不再赘述。
还需要说明的是，本文中的透镜为在光轴近旁具有光焦度的光学元件，关于透镜的面形状，所谓的“凸面”“凹面”是指近轴(光轴近旁)的形状。
可以看到，本发明实施例中提供的摄像镜头包括第一透镜、衍射光学元件和透镜模组，一方面利用衍射光学元件的负色散来抵消折射元件(如L1、透镜模组)的正色散，从而有效降低了成像的色差；另一方面通过透镜模组，能进一步平衡像散、球差、畸变等单色像差。所以，采用这样的结构框架设计的摄像镜头，将能够针对不同尺寸的图像传感器(如1/2.8英寸～1/2.3英寸等等的大幅面的图像传感器)来设计实现大光圈(如F1.5、F1.4等等大光圈)的摄像镜头，提高成像质量；另外，本发明实施例还能够通过优化摄像镜头的各个透镜的非球面系数、厚度、透镜材料、折射率等参数来满足摄像镜头的小型化需求(即实现较小的TTL)。也就是说，本发明实施例提供的摄像镜头既能同时满足小型化和高成像质量，又能满足图像传感器幅面增大的需求。
此外，由于摄像镜头中的衍射光学元件可采用塑料材料制成，第一透镜和透镜模组也可采用塑料材料制成，从而不需要采用低色散的玻璃材料或者其他特殊的无机材料，所以实施本发明实施例还有效降低了摄像镜头的成本，满足商业应用需求。
基于上述图1实施例的结构框架，下面详细介绍本发明实施例提供的摄像镜头的一种具体实施方式。参见图3，该实施方式中，透镜模组由4枚透镜构成，亦即摄像镜头包括6枚独立透镜和1个红外滤光片，摄像镜头沿光轴X从物面侧到像面侧依次包括：
第一透镜L1，可参考图1实施例中L1的相关描述，这里不再赘述。
第二透镜L2，可参考图1、图2实施例中L2的相关描述，这里不再赘述。
第三透镜L3，L3包括两个面，可分别称为第6面和第7面，第6面朝向物面侧，第7面朝向像面侧。第6面和第7面中的至少一个面为非球面，以便于校正残余的像差，并且起着缩小像散差的作用。具体的，第6面在在光轴X处为凸面形状，第7面在光轴X处可 为凸面形状也可为凹面形状，L3具有正的光焦度。
第四透镜L4，L4包括两个面，可分别称为第8面和第9面，第8面朝向物面侧，第9面朝向像面侧。具体的，L4呈弯月形的形状，第8面在光轴X处为凹面形状，L4可用于校正轴上色像差(属于位置色像差的一种)以及良好地校正倍率色像差，并且校正低像高至约70％像高的像面中的畸变。L4具有较弱的正光焦度或负的光焦度。
第五透镜L5，L5包括两个面，可分别称为第10面和第11面，第10面朝向物面侧，第11面朝向像面侧。第10面和第11面皆采用非球面，以便于校正透镜周边部的球面像差；通过L5还有利于实现将从L5射出的光线在低像高至最大像高之间控制成适当的角度。具体的，L5呈弯月形的形状，第10面在光轴X处为凸面形状，第11面在光轴X处为凹面形状，此外，在第10面和/或第11面中，在远离光轴X的位置具有一个反曲线点，即，第10面和/或第11面的周边部的形状呈现出向物面侧的方向弯曲。
第六透镜L6，L6包括两个面，可分别称为第12面和第13面，第12面朝向物面侧，第13面朝向像面侧。第12面和第13面皆采用非球面，具体的，第12面在光轴X处为凸面形状，第13面在光轴X处为凹面形状，L6具有负的光焦度，从而有利于确保后焦距、进行像散的校正以及控制向图像传感器的主光线入射角度。具体的，在第13面中，在远离光轴X的位置具有一个反曲线点，即，第13面为在光轴X的附近为凹面、随着朝向周边部而向凸面变化的非球面。因此，L6的光焦度越朝向透镜的周边部，其负的光焦度越弱，或在周边部逐渐向正的光焦度变化，通过形成这种非球面，有利于控制各像高处向图像传感器射入的主光线的入射角度。具体的，第12面也具有在周边部向正的光焦度变化的非球面。这样，L6的透镜的周边部将所需的正光焦度分配到这两个面，从而防止L6的形状发生急剧变化。
可以理解的是，上述第三透镜L3、第四透镜L4、第五透镜L5和第六透镜L6共同构成了本发明实施例中的“透镜模组”。
红外滤光片IR，IR配置在透镜模组与图像传感器之间，用于实现对红外线进行截止、滤光等。
需要说明的是，在具体实现中，摄像镜头中所有的透镜均可由塑料材料构成，其中，L1可具体采用环烯烃类的低色散的材料；L3、L4、L5以及L6可以根据摄像镜头的结构设计情况来选择采用聚碳酸酯类的高色散的材料或者环烯烃类的低色散的材料；L2所采用的具体材料参考上文的说明，这里不再赘述。
还需要说明的是，本文中所谓的“反曲线点”是指切平面与光轴垂直相交的非球面上的点。
本发明具体实施例中，上述图3实施例所描述的摄像镜头中的透镜满足以下的条件式(1)～(7)：
(1)50<V dl<60；其中，V dl表示第一透镜L1的对d线(即钠光谱中的d线，具体为基准波长589.3nm)的阿贝数；
(2)30<V d21<60；其中，V d21表示第二透镜L2中的透镜A对d线的阿贝数；
(3)20<V d22<40；其中，V d22第二透镜L2中的透镜B对d线的阿贝数；
(4)50<V d3<60；其中，V d3表示第三透镜L3的对d线的阿贝数；
(5)20<V d4<30；其中，V d4表示第四透镜L4的对d线的阿贝数；
(6)1<f1/f21<5；其中，f1表示第一透镜L1的焦距；f21表示第二透镜L2(即光学衍射元件)中的第3面和第4面的焦距(透镜A的焦距)；
(7)f21/f22<1；其中，f21表示第二透镜L2中的透镜A的焦距；f22表示第二透镜L2(即光学衍射元件)中的第4面和第5面的焦距(透镜B的焦距)；
本发明实施例通过上述条件式(1)～(5)，分别将第一透镜L1～第四透镜L4对d线的阿贝数规定在适当的范围内，从而能够良好地校正轴上色像差及倍率色像差。此外，根据上述规定的范围内，将能够轻易地为各个透镜选择合适的塑料材料，从而实现降低了摄像镜头的成本。
本发明实施例通过上述条件式(6)和(7)，将第一透镜L1与第二透镜L2中的透镜B之间的焦距比例规定在适当的范围内，以及将第二透镜L2中的透镜A与透镜B之间的焦距比例规定在适当的范围内，从而能够在缩短光学全长的同时实现校正各种像差。
基于上述图3实施例描述的摄像镜头以及上述条件(1)～(7)，下面进一步描述一种具体应用场景中摄像镜头的相关镜头参数，如下表1所示，表1中，面序号所表示的面与上文中所给出的面一一对应，也就是说，面序号“1”表示前述第1面、面序号“2”表示前述第2面，面序号“3”表示前述第3面，以此类推。f表示整个摄像镜头的焦距；Fno表示摄像镜头的F值；ω表示摄像镜头的半视场角；TTL表示摄像镜头的光学全长，本文中，光学全长(Total Track Length，TTL)是指光学***中，位于最靠物面侧的透镜朝向物面侧的面(如本文中第一透镜中的第1面)至像面(IM)为止的光轴X上的距离。此外，i表示从物面侧开始计数的透镜面的序号(即对应图3实施例所示的摄像镜头中的各个透镜面)、r表示透镜面的曲率半径、d表示在光轴X上的透镜面间的距离、N d表示透镜面对d线的折射率、V d表示透镜面对d线的阿贝数。
表1
Figure PCTCN2019075626-appb-000001
Figure PCTCN2019075626-appb-000002
下面进一步描述摄像镜头中各个透镜的透镜面。在本实施例中，摄像镜头的透镜面可能是由非球面形成，对于这些非球面的透镜面，非球面表面的非球面方程可由下式给出：
Figure PCTCN2019075626-appb-000003
其中，Z表示透镜面中与z轴平行的高度，r表示从顶点起的径向距离，c是顶点处表面的曲率，K是圆锥常数，A 4、A 6、A 8、A 10、A 12表示4阶、6阶、8阶、10阶、12阶对应阶次的非球面系数，可根据需要来选择适当的阶次的非球面。
下面进一步给出该应用场景中的摄像镜头中的各个透镜面对应的圆锥常数K和非球面系数，如下表2所示：
表2
Figure PCTCN2019075626-appb-000004
Figure PCTCN2019075626-appb-000005
基于上述表1和表2，下面说明本发明实施例中对该摄像镜头的实验测试结果。
参见图4，图4中的(a)～(d)是本发明实施例在470-650nm范围的可见光谱上的多色光线像差曲线图。如图4所示，不同的成像平面(子午像面Tan、弧矢像面Sag)、在不同的视场处(0mm、1.2950mm、2.590mm、3.2380mm)、不同波长(0.650um、0.550um、0.470um)对应的像差(纵轴的对应值)皆小于20um，也就是说，不同的成像平面、不同的视场处、不同波长的像差都被良好的校正。
参见图5，图5是本发明实施例对场曲(Field Curvature)和畸变(Distortion)的仿真结果，根据图示仿真结果可以看出，不同波长(0.650um、0.550um、0.470um)的场曲都能较好的补偿，同时，不同波长(0.650um、0.550um、0.470um)的畸变也能控制在3％以内，所以，本发明实施例提供的摄像镜头满足设计应用要求，即该摄像镜头可以在5.12mm的TTL范围内，实现F1.44的超大光圈，并且像差能够得到非常好的优化。
可以看到，本发明实施例中提供的摄像镜头包括6枚透镜，且在L2位置为衍射光学元件，一方面利用衍射光学元件的负色散来抵消折射元件(如L1、透镜模组)的正色散，从而有效降低了成像的色差；另一方面通过透镜模组，能进一步平衡像散、球差、畸变等单色像差。所以，采用这样的结构框架设计的摄像镜头，将能够针对不同尺寸的图像传感器(如1/2.8英寸～1/2.3英寸等等的大幅面的图像传感器)来设计实现超大光圈(如F1.44)的摄像镜头，提高成像质量；另外，本发明实施例还能够通过优化摄像镜头的各个透镜的非球面系数、厚度、透镜材料、折射率等参数来满足摄像镜头的小型化需求(如TTL为5.12mm)。也就是说，本发明实施例提供的摄像镜头既能同时满足小型化和高成像质量，又能满足图像传感器幅面增大的需求。
此外，由于摄像镜头中的衍射光学元件可采用塑料材料制成，第一透镜和透镜模组也可采用塑料材料制成，从而不需要采用低色散的玻璃材料或者其他特殊的无机材料，所以实施本发明实施例还有效降低了摄像镜头的成本，满足商业应用需求。
基于上述图3实施例描述的摄像镜头以及上述条件(1)～(7)，本发明实施例提供了又一种具体应用场景中的摄像镜头的相关镜头参数，如下表3所示，同理，面序号对应的面与上文中所给出的面一一对应，f表示整个摄像镜头的焦距、Fno表示摄像镜头的F值、ω表示摄像镜头的半视场角、TTL表示摄像镜头的光学全长。此外，i表示从物面侧开始计数的透镜面的序号(即对应图2实施例所示的摄像镜头中的各个透镜面)、r表示透镜面的曲率半径、d表示在光轴X上的透镜面间的距离、N d表示透镜面对d线的折射率、V d表示透镜面对d线的阿贝数。
表3
Figure PCTCN2019075626-appb-000006
Figure PCTCN2019075626-appb-000007
下面进一步描述摄像镜头各个透镜的透镜面。同理，在本实施例中，摄像镜头的透镜面可能是由非球面形成，对于这些非球面的透镜面，非球面表面的非球面方程可由下式给出：
Figure PCTCN2019075626-appb-000008
其中，Z表示透镜面中与z轴平行的高度，r表示从顶点起的径向距离，c是顶点处表面的曲率，K是圆锥常数，A 4、A 6、A 8、A 10、A 12表示表示4阶、6阶、8阶、10阶、12阶对应阶次的非球面系数，可根据需要来选择适当的阶次的非球面。
下面进一步给出该应用场景中的摄像镜头中的各个透镜面对应的圆锥常数K和非球面系数，如下表4所示：
表4
Figure PCTCN2019075626-appb-000009
Figure PCTCN2019075626-appb-000010
基于上述表3和表4，下面提供本发明实施例中对摄像镜头的实验测试结果。
参见图6，图6中的(a)～(d)是本发明实施例在470-650nm范围的可见光谱上的多色光线像差曲线图。如图4所示，不同的成像平面(子午像面Tan、弧矢像面Sag)、在不同的视场处(0mm、1.2950mm、2.590mm、3.2380mm)、不同波长(0.650um、0.550um、0.470um)对应的像差(纵轴的对应值)皆小于20um，也就是说，不同的成像平面、不同的视场处、不同波长的像差都被良好的校正。
参见图7，图7是本发明实施例对场曲(Field Curvature)和畸变(Distortion)的仿真结果，根据图示仿真结果可以看出，不同波长(0.650um、0.550um、0.470um)的场曲都能较好的补偿，同时，不同波长(0.650um、0.550um、0.470um)的畸变也能控制在4％以内，所以，本发明实施例提供的摄像镜头满足设计应用要求，即该摄像镜头可以在5.14mm的TTL范围内，实现F1.48的超大光圈，并且光色像差能够得到非常好的优化。
可以看到，本发明实施例中提供的摄像镜头包括6枚透镜，且在L2位置为衍射光学元件，一方面利用衍射光学元件的负色散来抵消折射元件(如L1、透镜模组)的正色散，从而有效降低了成像的色差；另一方面通过透镜模组，能进一步平衡像散、球差、畸变等单色像差。所以，采用这样的结构框架设计的摄像镜头，将能够针对不同尺寸的图像传感器(如1/2.8英寸～1/2.3英寸等等的大幅面的图像传感器)来设计实现超大光圈(如F1.48)的摄像镜头，提高成像质量；另外，本发明实施例还能够通过优化摄像镜头各个透镜的非球面系数、厚度、透镜材料、折射率等参数来满足摄像镜头的小型化需求(如TTL为5.14mm)。也就是说，本发明实施例提供的摄像镜头既能同时满足小型化和高成像质量，又能满足图像传感器幅面增大的需求。
此外，由于摄像镜头中的衍射光学元件可采用塑料材料制成，第一透镜和透镜模组也可采用塑料材料制成，从而不需要采用低色散的玻璃材料或者其他特殊的无机材料，所以实施本发明实施例还有效降低了摄像镜头的成本，满足商业应用需求。
基于上述图1实施例的结构框架，下面继续介绍本发明实施例提供的摄像镜头的又一种具体实施方式。参见图8，该实施方式中，透镜模组由5枚透镜构成，亦即摄像镜头包括7枚独立透镜和1个红外滤光片，摄像镜头沿光轴X从物面侧到像面侧依次包括：
第一透镜L1，可参考图1实施例中L1的相关描述，这里不再赘述。
第二透镜L2，可参考图1、图2实施例中L2的相关描述，这里不再赘述。
第三透镜L3，L3包括两个面，可分别称为第6面和第7面，第6面朝向物面侧，第7面朝向像面侧。第6面和第7面中的至少一个面为非球面，以便于校正残余的像差，并且起着缩小像散差的作用。具体的，第6面在在光轴X处为凹面形状，第7面在光轴X处可为凸面形状也可为凹面形状，L3具有负的光焦度。
第四透镜L4，L4包括两个面，可分别称为第8面和第9面，第8面朝向物面侧，第9面朝向像面侧。具体的，L4呈弯月形的形状，第8面在光轴X处为凹面形状，L4可用于校正轴上色像差(或称纵向色像差)以及良好地校正倍率色像差。L4具有较弱的正光焦度或负的光焦度。
第五透镜L5，L5包括两个面，可分别称为第10面和第11面，第10面朝向物面侧，第10面在光轴X处为凹面形状，第11面朝向像面侧。第10面和第11面皆采用非球面，以便于校正透镜周边部的球面像差。
第六透镜L6，L6包括两个面，可分别称为第12面和第13面，第12面朝向物面侧，第13面朝向像面侧。第12面和第13面皆采用非球面，具体的，第12面在光轴X处为凸面形状，第12面在光轴以外的位置具有反曲线点；第13面在光轴X处为凹面形状，第13面在光轴以外的位置具有反曲线点。L6具有负的光焦度。
第七透镜L7，L7包括两个面，可分别称为第14面和第15面，第14面朝向物面侧，第15面朝向像面侧。第14面和第15面皆采用非球面，具体的，第14面在光轴X处为凸面形状，第15面在光轴X处为凹面形状，L7具有负的光焦度，从而有利于确保后焦距、进行像散的校正以及控制向图像传感器的主光线入射角度。具体的，在第15面中，在远离光轴X的位置具有一个反曲线点，即，第15面为在光轴X的附近为凹面、随着朝向周边部而向凸面变化的非球面。因此，L7的光焦度越朝向透镜的周边部，其负的光焦度越弱，或在周边部逐渐向正的光焦度变化，通过形成这种非球面，有利于控制各像高处向图像传感器射入的主光线的入射角度。具体的，第14面也具有在周边部向正的光焦度变化的非球面。这样，L7的透镜的周边部将所需的正光焦度分配到这两个面，从而防止L7的形状发生急剧变化。
红外滤光片IR，IR配置在摄像镜头与图像传感器(像面IM)之间，用于实现对红外线进行截止、滤光等。
需要说明的是，在本发明实施例具体实现中，摄像镜头所有的透镜均可由塑料材料构成，其中，L1可具体采用环烯烃类的低色散的材料；L3、L4、L5、L6以及L7可以根据摄像镜头的结构设计情况来选择采用聚碳酸酯类的高色散的材料或者环烯烃类的低色散的材料；L2所采用的具体材料参考上文的说明，且其材料的折射率、阿贝数与前述图3实施例的L2的相关折射率、阿贝数等有所差异(参见前述表1、表3和下述表5)，这里不再赘 述。
同理，本发明具体实施例中，上述图8实施例所描述的摄像镜头中的透镜满足以下的条件式(1)～(7)：
(1)50<V dl<60；其中，V dl表示第一透镜L1的对d线(即钠光谱中的d线，具体为基准波长589.3nm)的阿贝数；
(2)30<V d21<60；其中，V d21表示第二透镜L2中的透镜A对d线的阿贝数；
(3)20<V d22<40；其中，V d22第二透镜L2中的透镜B对d线的阿贝数；
(4)50<V d3<60；其中，V d3表示第三透镜L3的对d线的阿贝数；
(5)20<V d4<30；其中，V d4表示第四透镜L4的对d线的阿贝数；
(6)1<f1/f21<5；其中，f1表示第一透镜L1的焦距；f21表示第二透镜L2中的第3面和第4面的焦距(透镜A的焦距)；
(7)f21/f22<1；其中，f21表示第二透镜L2中的透镜A的焦距；f22表示第二透镜L2中的第4面和第5面的焦距(透镜B的焦距)；
本发明实施例通过上述条件式(1)～(5)，分别将第一透镜L1～第四透镜L4对d线的阿贝数规定在适当的范围内，从而能够良好地校正轴上色像差及倍率色像差。此外，根据上述规定的范围内，将能够轻易地为各个透镜选择合适的塑料材料，从而实现降低了摄像镜头的成本。
本发明实施例通过上述条件式(6)和(7)，将第一透镜L1与第二透镜L2中的透镜B之间的焦距比例规定在适当的范围内，以及将第二透镜L2中的透镜A与透镜B之间的焦距比例规定在适当的范围内，从而能够在缩短光学全长的同时实现校正各种像差。
基于上述图8实施例描述的摄像镜头以及上述条件(1)～(7)，下面进一步描述一种具体应用场景中的摄像镜头的相关镜头参数，如下表5所示：
表5
Figure PCTCN2019075626-appb-000011
Figure PCTCN2019075626-appb-000012
下面进一步描述摄像镜头各个透镜的透镜面。同理，在本实施例中，摄像镜头的透镜面可能是由非球面形成，对于这些非球面的透镜面，非球面表面的非球面方程可由下式给出：
Figure PCTCN2019075626-appb-000013
其中，Z表示透镜面中与z轴平行的高度，r表示从顶点起的径向距离，c是顶点处表面的曲率，K是圆锥常数，A 4、A 6、A 8、A 10、A 12、A 14、A 16表示非球面系数。
下面进一步给出该应用场景中的摄像镜头中的各个透镜面对应的圆锥常数K和非球面系数，如下表6所示：
表6
Figure PCTCN2019075626-appb-000014
Figure PCTCN2019075626-appb-000015
基于上述表5和表6，下面提供本发明实施例对摄像镜头的实验测试结果。
参见图9，图9是本发明实施例对纵向球差(Longitudinal spherical ABER)和畸变(Distortion)的仿真结果，根据图示仿真结果可以看出，不同波长(0.650um、0.550um、0.470um)的纵向球差都能较好的补偿，同时，不同波长(0.650um、0.550um、0.470um)的畸变也能控制在2％以内，所以，本发明实施例提供的摄像镜头满足设计应用要求，即该摄像镜头可以在5.60mm的TTL范围内，实现F1.45的超大光圈，并且光色像差能够得到非常好的优化校正。
可以看到，本发明实施例中提供的摄像镜头包括7枚透镜，且在L2位置为衍射光学元件，一方面利用衍射光学元件的负色散来抵消折射元件(如L1、透镜模组)的正色散，从而有效降低了成像的色差；另一方面通过透镜模组，能进一步平衡像散、球差、畸变等单色像差。所以，采用这样的结构框架设计的摄像镜头，将能够针对不同尺寸的图像传感器(如1/2.8英寸～1/2.3英寸的大幅面的图像传感器)来设计实现超大光圈(如F1.45)的摄像镜头，提高成像质量；另外，本发明实施例还能够通过优化摄像镜头各个透镜的非球面系数、厚度、透镜材料、折射率等参数来满足摄像镜头的小型化需求(如TTL为5.60mm)。也就是说，本发明实施例提供的摄像镜头既能同时满足小型化和高成像质量，又能满足图像传感器幅面增大的需求。
此外，由于摄像镜头中的衍射光学元件可采用塑料材料制成，第一透镜和透镜模组也可采用塑料材料制成，从而不需要采用低色散的玻璃材料或者其他特殊的无机材料，所以实施本发明实施例还有效降低了摄像镜头的成本，满足商业应用需求。
需要说明的是，虽然在上述实施例中，衍射光学元件都是以出现在摄像镜头的L2位置进行描述，但是在可能的实施方式中，衍射光学元件也可以出现在其他的位置(例如L3、L4、L5…等等)，其实现过程可参考上文描述，这里不再赘述。
还需要说明的是，虽然在上述实施例中，衍射光学元件都是1枚的形式以进行描述，但是在可能的实施方式中，衍射光学元件也是多枚(例如2、3、4枚…等等)，其实现过程可参考上文描述，这里不再赘述。
基于同样的发明构思，本发明实施例还提供一种镜头模组，所述镜头模组包括如前文所描述的摄像镜头，以及图像传感器；其中：所述摄像镜头用于形成被摄体的光信号并反映到所述图像传感器；所述图像传感器用于将对应于被摄体的光信号变换为图像信号。
基于同样的发明构思，本发明实施例还提供一种终端，所述终端安装有如上所述的镜头模组。
在上述实施例中，对各个实施例的描述各有侧重，某个实施例中没有详述的部分，可以参见其他实施例的相关描述。
如上所述，将各个实施方式所涉及的摄像镜头应用于智能手机、笔记本电脑、台式电脑、平板电脑、个人数字助理(Personal Digital Assistant，PDA)、可穿戴设备、增强现实(Augmented Reality，AR)设备、虚拟现实(Virtual Reality，VR)设备、监控设备等终端产品中，能够满足图像传感器幅面越来越大的要求，且由于摄像镜头具有较低的光学总长TTL和超大的光圈(如F1.6、F1.5、F1.4等)，采用大光圈可以提升摄像镜头的进光量，从而提升夜景或室内场景中的成像清晰度、色彩准确度，并降低对拍照录像的防抖要求，并满足不同尺寸的图像传感器的设计需求，从而有利于实现该终端产品的小型化和高性能化。

Claims (10)

  1. 一种摄像镜头，其特征在于，所述摄像镜头沿光轴从物面到像面包括：第一透镜、第二透镜和透镜模组，所述第二透镜为衍射光学元件，所述衍射光学元件位于所述第一透镜和所述透镜模组之间，且与所述第一透镜和所述透镜模组相隔离，其中：
    所述第一透镜朝向物面侧的面在光轴处为凸面，朝向像面侧的面在光轴处为凹面；所述第一透镜具有正的光焦度；
    所述衍射光学元件包括朝向物面侧的面、朝向像面侧的面、以及位于这两个面之间的衍射面；其中，朝向物面侧的面在光轴处为凸面，朝向像面侧的面在光轴处为凹面；所述衍射光学元件具有正的光焦度；
    所述透镜模组包括沿光轴间隔排列的N枚透镜，N为大于或等于3且小于或等于7的整数；所述N枚透镜中的各个透镜的朝向物面侧的面和朝向像面侧的面中，至少有一个面为非球面；所述透镜模组具有正的光焦度；
    其中，所述第一透镜、所述衍射光学元件和位于所述透镜模组内的N个透镜的光轴互为重合。
  2. 如权利要求1任一项所述的摄像镜头，其特征在于，所述衍射光学元件中，位于朝向物面侧的面和衍射面之间的材料的折射率为N1，位于朝向像面侧的面和衍射面之间的材料的折射率为N2，N1和N2分别满足以下条件式：
    1.62<N1<1.76；
    1.55<N2<1.64。
  3. 如权利要求1或2所述的摄像镜头，其特征在于，所述衍射光学元件中，位于朝向物面侧的面和衍射面之间的材料对钠光谱的d线的阿贝数为V d21，位于朝向像面侧的面和衍射面之间的材料对钠光谱的d线的阿贝数为V d22，V d21和V d22分别满足以下条件式：
    30<V d21<60；
    20<V d22<40。
  4. 如权利要求1-3任一项所述的摄像镜头，其特征在于，所述衍射光学元件中，位于朝向物面侧的面和衍射面之间的材料的光焦度为P1，位于朝向像面侧的面和衍射面之间的材料的光焦度为P2，P1和P2满足条件式：
    -4<P1/P2<4。
  5. 如权利要求1-4任一项所述的摄像镜头，其特征在于，所述衍射光学元件朝向物面侧的面和朝向像面侧的面中，至少有一个面为非球面。
  6. 如权利要求1-5任一项所述的摄像镜头，其特征在于，所述透镜模组包括如下4个透镜：第三透镜、第四透镜、第五透镜和第六透镜，其中：
    所述第三透镜朝向物面侧的面在光轴处为凸面；所述第三透镜具有正的光焦度；
    所述第四透镜呈弯月形，所述第四透镜朝向物面侧的面在光轴处为凹面；
    所述第五透镜朝向物面侧的面在光轴处为凸面，朝向物面侧的面在光轴以外的位置具有反曲线点；
    所述第六透镜朝向物面侧的面在光轴处为凸面，朝向像面侧的面在光轴处为凹面，且朝向像面侧的面在光轴以外的位置具有反曲线点；所述第六透镜具有负的光焦度。
  7. 如权利要求1-5任一项所述的摄像镜头，其特征在于，所述透镜模组包括如下5个透镜：第三透镜、第四透镜、第五透镜、第六透镜和第七透镜，其中：
    所述第三透镜朝向物面侧的面在光轴处为凹面；所述第三透镜具有负的光焦度；
    所述第四透镜呈弯月形，所述第四透镜朝向物面侧的面在光轴处为凹面；
    所述第五透镜朝向物面侧的面在光轴处为凹面；
    所述第六透镜朝向物面侧的面在光轴处为凸面，且朝向物面侧的面在光轴以外的位置具有反曲线点，朝向像面侧的面在光轴处为凹面，且朝向像面侧的面在光轴以外的位置具有反曲线点；所述第六透镜具有负的光焦度；
    所述第七透镜朝向物面侧的面在光轴处为凸面，朝向像面侧的面在光轴处为凹面，且朝向像面侧的面在光轴以外的位置具有反曲线点；所述第七透镜具有负的光焦度。
  8. 如权利要求6或7所述的摄像镜头，其特征在于，所述摄像镜头中的各透镜还满足以下条件式：
    50<V dl<60；其中，V dl表示第一透镜L1对钠光谱的d线的阿贝数；
    50<V d3<60；其中，V d3表示第三透镜L3对钠光谱的d线的阿贝数；
    20<V d4<30；其中，V d4表示第四透镜L4对钠光谱的d线的阿贝数；
    1<f1/f21<5；其中，f1表示第一透镜L1的焦距；f21表示所述衍射光学元件朝向物面侧的面和衍射面的焦距；
    f21/f22<1；其中，f22表示所述衍射光学元件朝向像面侧的面和衍射面的焦距。
  9. 一种摄像模组，其特征在于，所述摄像模组包括如权利要求1-8任一项所述的摄像镜头，以及图像传感器；其中：
    所述摄像镜头用于形成被摄体的光信号并反映到所述图像传感器；
    所述图像传感器用于将对应于被摄体的光信号变换为图像信号。
  10. 一种终端，其特征在于，所述终端包括显示屏和如权利要求9所述的摄像模组，所述显示屏用于显示所述摄像模组拍摄的图像。
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