CN101105574A - Zoom lens, camera, and personal digital assistant - Google Patents
Zoom lens, camera, and personal digital assistant Download PDFInfo
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- CN101105574A CN101105574A CNA2007101290317A CN200710129031A CN101105574A CN 101105574 A CN101105574 A CN 101105574A CN A2007101290317 A CNA2007101290317 A CN A2007101290317A CN 200710129031 A CN200710129031 A CN 200710129031A CN 101105574 A CN101105574 A CN 101105574A
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Abstract
The zoom lens includes a first lens group G1 having a negative refracting power, an aperture stop FA, a second lens group G2 having a positive refracting power, and a third lens group G3 having a positive refracting power, which are disposed in order from an object side. In this configuration, at least the first lens group G1 and the second lens group G2 move along with changing magnification from the wide-anglu end toward the telephoto end, in a manner that a spacing between the first lens group G1 and the second lens group G2 decreases gradually and a spacing between the second lens group G2 and the third lens group G3 increases gradually. Here, the second lens group G2 includes a first cemented lens C1 having at least three pieces of lenses united, and a second cemented lens C2 having at least two pieces of lenses united.
Description
Priority requirement
This patent application claims priority from japanese patent application No. 2006-182843, filed on 30.2006 to the office, and japanese patent application No. 2006-269663, filed on 29.2006 to the office, both of which are incorporated by reference in their entirety.
Technical Field
[0001]
The present invention relates to a zoom lens capable of selecting and setting an ideal focal length within a predetermined focal length range, which, in addition to having characteristics of small size and good performance, is capable of achieving a wide angle of view at a wide angle end and a high variable magnification; and more particularly to a focusing lens suitable for use in photographing apparatuses using an electronic photographing method such as digital still cameras and video cameras, as well as for use in film-based cameras using silver halide photosensitive films, and to a photographing apparatus and a personal digital assistant using the focusing lens.
Background
[0002]
Conventional cameras using long-standing silver halide films, that is, cameras using films have been replaced with so-called digital cameras or electronic cameras that photograph an object using a solid-state imaging Device (solid imaging Device) such as a CCD (Charge Coupled Device), acquire image data of a still image or a moving image of the object, and store the data in digital form in a nonvolatile semiconductor memory such as a flash memory as a representative. Such cameras have been widely spread as stand-alone cameras, and are used in mobile phones and other personal digital assistants, as well as being applied to film-based cameras as a new type of use.
The market for such digital cameras has been very large and the demands on digital cameras by different users have varied greatly. Users always desire digital cameras with higher image quality and smaller size, and both of these factors contribute significantly to user demand. Therefore, higher performance and smaller size are also required for the zoom lens used as a photographing lens (photographing lens).
In order to achieve a smaller size, it is necessary to reduce the length of the entire lens of the zoom lens, that is, to reduce the distance from the lens surface closest to the object side to the image plane. To achieve higher performance, the zoom lens must have a resolving power corresponding to an imaging device of at least about 800 to 1000 ten thousand pixels over the entire zoom range.
[0003]
In addition, many users desire a wider angle of view of the photographing lens; a half angle of view at the short focal end of the zoom lens, that is, a half angle of view at the wide-angle end is desirably 38 degrees or more. For a photographer, i.e., a professional photographer, or a high-level amateur having higher expertise and skill than the professional photographer, they desire a half viewing angle at the wide-angle end of 42 degrees or more. The half viewing angles of 38 degrees and 42 degrees, when converted to the focal length of a 35mm film-based camera using 35mm (called a leica camera), correspond to focal lengths of 28mm and 24mm, respectively.
There are many types of zoom lenses suitable for digital cameras. The following zoom lens can be used to achieve a smaller size. The zoom lens includes, in order from an object side, a first lens group having a negative refracting power, a second lens group having a positive refracting power, and a third lens group having a positive refracting power; and an aperture stop integrally moving with the second lens group on the object side of the second lens group. Wherein the second lens group is monotonously moved from the image side to the object side with changing magnification from the wide angle end to the telephoto end. The first lens group is moved to correct a variation in the image plane position due to a change in magnification.
[0004]
In such a lens, there is a well-known structure in which two positions of the second lens group have joint surfaces to achieve correction of ideal axial chromatic aberration and chromatic aberration of magnification, or control deterioration of imaging performance due to decentering between lenses.
For example, a zoom lens including two pairs of cemented lenses in the second lens group is disclosed in JP2001-281545A, JP2003-107348A, JP2003-241091A and JP 2006-113554A. As another example, a zoom lens including three cemented lenses in the second lens group is disclosed in JP2004-102211A, JP2004-325975A, JP2005-24804A, JP2005-37576A and JP 2006-39523A.
JP2001-281545A discloses in embodiments 1 to 8 thereof that correction of ideal axial chromatic aberration and chromatic aberration of magnification is achieved with two pairs of cemented lenses in the second lens group. However, since the half-angle of view is less than 34 degrees, the requirement cannot be satisfied in the wide-angle view.
[0005]
In the same way, JP2003-241091A discloses in its embodiments 11 and 12 that correction of ideal axial chromatic aberration and chromatic aberration of magnification is achieved by using two pairs of cemented lenses in the second group of lenses. In this case, since the half viewing angle is less than 34 degrees, the requirement cannot be satisfied also in the wide viewing angle.
JP2004-102211A discloses in embodiments 11, 15 and 17 thereof a structure in which three cemented lenses are employed in the second lens group, in consideration of deterioration of imaging performance due to decentering between the lenses. However, since the half viewing angle is less than 33 degrees, it is also not satisfactory in terms of a wide viewing angle.
JP2004-325975A, JP2005-37576A and JP2006-39523A disclose a structure in which three cemented lenses are employed in the second lens group, in view of deterioration of imaging performance due to decentering between the respective lenses, with which the overall size of the zoom lens can be made relatively small, however, since the half angle of view is about 30 to 33 degrees, it is also not satisfactory in terms of a wide angle of view.
[0006]
JP2003-107348A discloses a zoom lens which can also obtain a relatively wide half angle of view of about 39 degrees by employing two pairs of cemented lenses in the second lens group to achieve ideal axial chromatic aberration and chromatic aberration of magnification correction. The half viewing angle of 39 degrees still cannot satisfy the requirement of the half viewing angle of 42 degrees or more.
JP2005-24804A discloses a zoom lens that can also obtain a relatively wide half angle of view of about 39 degrees by employing three cemented lenses in the second lens group to achieve ideal axial chromatic aberration and chromatic aberration of magnification correction. The half viewing angle of 39 degrees still cannot satisfy the requirement of the half viewing angle of 42 degrees or more, similarly to the case of JP 2003-107348A.
[0007]
JP2006-113554A discloses in some embodiments thereof a zoom lens that obtains a half angle of view of 43 degrees or more, which satisfies the requirement of a wide angle of view, by using two pairs of cemented lenses in the second lens group. However, in order to achieve the desired correction of chromatic aberration of magnification, the negative lens of the first lens group needs to employ a low-dispersion glass having an abbe number of 80 or more. The low dispersion glass having an abbe number of 80 or more is so-called special low dispersion glass, and the material cost is high, the process difficulty is large, and the yield is small as the lens size is large. A common lens process includes a process of cleaning each lens with, for example, ultrasonic waves. Ultrasonic cleaning is a simple and widely used cleaning method, but a lens made of special low dispersion glass cannot be cleaned by ultrasonic waves, and only can be manually cleaned with cloth. Accordingly, the larger the size of the lens, the more difficult the lens process and the lower the yield. Therefore, using it to the first lens group whose lens diameter tends to increase drastically increases the cost of the lens system, which is not preferable.
[0009]
Therefore, there is a need for a zoom lens that controls various aberrations without significantly increasing the manufacturing cost, realizes a sufficiently wide angle of view at the wide angle end, is small in size, and has high resolving power. There is also a need for cameras and personal digital assistants that employ the zoom lens described above.
Disclosure of Invention
[0012]
The present invention focuses on a zoom lens that satisfies this need, and the present invention also describes a camera and a personal digital assistant that include such a zoom lens.
[0013]
Another aspect of the present invention includes a zoom lens having a first lens group with a negative refractive index; a second lens group having a positive refracting power; a third lens group having a positive refracting power, the first lens group, the second lens group, and the third lens group being disposed from the object side; an aperture stop disposed on an object side of the second lens group and moving together with the second lens group, wherein at least the first lens group and the second lens group move in such a manner that a distance between the first lens group and the second lens group decreases and a distance between the second lens group and an image plane increases while varying magnification from a wide-angle end to a telephoto end, and the second lens group includes a first cemented lens composed of at least three pieces of combined lenses and a second cemented lens composed of at least two pieces of combined lenses.
[0014]
The second cemented lens is adapted to be disposed on the image side of the first cemented lens, a surface of the first cemented lens closest to the object side and a surface of the first cemented lens closest to the image side are convex toward the object side, and the second cemented lens has a positive refractive index as a whole.
The second cemented lens is adapted to be disposed on the image side of the first cemented lens composed of three positive lenses, one negative lens, and one positive lens, which are disposed in this order from the object side and are bonded to each other, the second cemented lens having a positive refractive index as a whole.
[0015]
The zoom lens is adapted to satisfy the conditional expression: 1.65 < n c1-1 ＜1.90，1.65＜n c1-2 ＜1.90，4＜v c1-1 -v c1-2 < 25, and 68 < v c1-3 < 98, wherein n c1-1 Is the refractive index of the positive lens closest to the object side of the first cemented lens, n c1-2 Is the refractive index, v, of the negative lens in the first cemented lens c1-1 Is the Abbe number, v, of the positive lens closest to the object side of the first cemented lens c1-2 Is the Abbe number, v, of the negative lens in the first cemented lens c1-3 Is the abbe number of the positive lens closest to the image side of the first cemented lens.
[0016]
The zoom lens is adapted to satisfy: d is more than 0.10 c1-2 /d c1-a11 < 0.19, wherein d c1-2 Is the central thickness of the negative lens in the first cemented lens, measured along the optical axis of the lens, d c1-a11 Is the center thickness of all of the cemented lenses.
The zoom lens is adapted to satisfy: 0.2 < (R) c1-1 -R c1-3 )/(R c1-1 +R c1-3 ) < 0.5, and-0.4 < (R) c1-3 -R c1-4 )/ (R c1-3 +R c1-4 ) < -0.1, wherein R c1-1 Is the radius of curvature, R, of the surface closest to the object side of the first cemented lens c1-3 Is a radius of curvature, R, of a bonding surface on the image side of the two bonding surfaces in the first cemented lens c1-4 Is the radius of curvature of the surface closest to the image side of the first cemented lens.
[0017]
A second cemented lens adapted to be placed on the image side of the first cemented lens, the second cemented lens being composed of a negative lens and a positive lens that are placed in order from the object side and cemented to each other, the zoom lens satisfying: 68 < v 21-2 < 98, wherein v c2-2 Is the abbe number of the positive lens in the second cemented lens.
The second cemented lens is adapted to be placed image-wise of the first cemented lens and at least one positive lens is placed on the object side of the first cemented lens.
[0018]
Preferably, at least one positive lens placed on the object side of the first cemented lens has at least one aspherical surface.
Preferably, the first cemented lens has only one spherical surface in structure, and the second lens group includes at least one aspherical surface.
Drawings
[0105]
Fig. 1 is a typical sectional view showing the structure of an optical system taken along the optical axis of a zoom lens of a first embodiment of the present invention.
Fig. 2 is a typical sectional view showing the structure of an optical system taken along the optical axis of a zoom lens of a second embodiment of the present invention.
Fig. 3 is a typical sectional view showing the structure of an optical system taken along the optical axis of a zoom lens of a third embodiment of the present invention.
Fig. 4 is a typical sectional view showing the structure of an optical system taken along the optical axis of a zoom lens according to a fourth embodiment of the present invention.
Fig. 5 is a typical sectional view showing the structure of an optical system taken along the optical axis of a zoom lens according to a fifth embodiment of the present invention.
Fig. 6 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at the wide-angle end according to the zoom lens of the first embodiment shown in fig. 1.
Fig. 7 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at an intermediate focal length of the zoom lens according to the first embodiment shown in fig. 1.
Fig. 8 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at the telephoto end of the zoom lens according to the first embodiment shown in fig. 1.
Fig. 9 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at the wide-angle end according to the zoom lens of the second embodiment shown in fig. 2.
Fig. 10 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at an intermediate focal length of the zoom lens according to the second embodiment shown in fig. 2.
Fig. 11 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at the telephoto end of the zoom lens according to the second embodiment shown in fig. 2.
Fig. 12 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at the wide-angle end according to the zoom lens of the third embodiment shown in fig. 3.
Fig. 13 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at an intermediate focal length of the zoom lens according to the third embodiment shown in fig. 3.
Fig. 14 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at the telephoto end of the zoom lens according to the third embodiment shown in fig. 3.
Fig. 15 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at the wide-angle end according to the zoom lens of the fourth embodiment shown in fig. 4.
Fig. 16 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at the intermediate focal length of the zoom lens according to the fourth embodiment shown in fig. 4.
Fig. 17 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at the telephoto end according to the zoom lens of the fourth embodiment shown in fig. 4.
Fig. 18 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at the wide-angle end according to the zoom lens of the fifth embodiment shown in fig. 5.
Fig. 19 shows aberration curves of spherical aberration, astigmatism, distortion, and coma at the intermediate focal length of the zoom lens according to the fifth embodiment shown in fig. 5.
Fig. 20 is an aberration curve showing spherical aberration, astigmatism, distortion, and coma at the telephoto end according to the zoom lens of the fifth embodiment shown in fig. 5.
Fig. 21A is a perspective view showing an appearance of a photographing apparatus of a model according to an embodiment of the present invention, in which a photographing lens is in a collapsed state inside a main body of the photographing apparatus, viewed from an object side.
Fig. 21B is a perspective view showing an appearance of a photographing apparatus of a model according to an embodiment of the present invention, in which a photographing lens protrudes outward from a main body of the photographing apparatus, viewed from an object side.
Fig. 22 is a perspective view showing an appearance of the photographing apparatus shown in fig. 21 viewed from the photographer;
fig. 23 is a typical block diagram illustrating a functional structure of the photographing apparatus shown in fig. 21.
Detailed Description
[0027]
The zoom lens, the photographing apparatus, and the personal digital assistant of the present invention will be described in detail below based on embodiments in conjunction with the drawings of the present invention. To facilitate an understanding of the principles of the invention, the structure and function of embodiments of the invention will be described before describing particular embodiments.
A zoom lens according to an embodiment of the present invention includes a first lens group having a negative refracting power, a second lens group having a positive refracting power, and an aperture stop; the first lens group, the aperture diaphragm and the second lens group are arranged in sequence from the object side; the aperture stop moves with the second lens group; with varying magnification from a wide-angle end to a telephoto end, at least the first lens group and the second lens group move in such a manner that an interval between the first lens group and the second lens group decreases and an interval between the second lens group and an image surface increases. Also, each zoom lens has the following features.
[0028]
In the zoom lens according to the embodiment of the present invention, the second lens group includes a first cemented lens including at least three lenses attached to and cemented together, and a second cemented lens including at least two lenses attached to and cemented together.
The zoom lens according to the embodiment of the present invention further includes a third lens group having a positive focal length on the image side of the second lens group; at least the first lens group and the second lens group move in such a manner that an interval between the second lens group and the third lens group gradually increases as a magnification is changed from a wide-angle end to a telephoto end; and the second lens group includes a first cemented lens composed of at least three lens cemented and a second cemented lens composed of at least two lens cemented.
A zoom lens according to an embodiment of the present invention adopts a structure in which a second cemented lens is placed on the image side of a first cemented lens; the surface closest to the object side in the first cemented lens is convex toward the object side, and the surface closest to the image side in the first cemented lens is convex toward the object side, that is, both surfaces are convex toward the object side; the second cemented lens has a positive refractive index as a whole.
[0029]
A zoom lens according to an embodiment of the present invention takes a structure in which a second cemented lens having three positive lenses, a negative lens, and a positive lens, which are placed in order from an object side and cemented with each other, is placed on an image side of a first cemented lens; the second cemented lens has a positive refractive index as a whole.
The zoom lens according to an embodiment of the present invention satisfies:
1.65＜n c1-1 ＜1.90，
1.65＜n c1-2 ＜1.90，
4＜v c1-1 -v c1-2 < 25, and
68＜v c1-3 ＜98，
wherein n is c1-1 Refractive index of positive lens at object side of first cemented lens, n c1-2 Is the refractive index, v, of the negative lens in the first cemented lens c1-1 Abbe number, v, of positive lens on object side of first cemented lens c1-2 Is the Abbe number, v, of the negative lens in the first cemented lens c1-3 Is the abbe number of the positive lens on the image side of the first cemented lens.
[0030]
The zoom lens according to the embodiment of the present invention satisfies the conditional expression: d is more than 0.10 c1-2 /d c1-a11 < 0.19, wherein d c1-2 Is the center thickness (thickness measured along the optical axis) of the negative lens in the first cemented lens, d c1-a11 Is the center thickness of all of the first cemented lenses.
The zoom lens according to the embodiment of the present invention satisfies the conditional expression:
[0031]
0.2＜(R c1-1 -R c1-3 )/(R c1-1 +R c1-3 ) < 0.5, and
-0.4＜(R c1-3 -R c1-4 )/(R c1-3 +R c1-4 )＜-0.1，
wherein R is c1-1 Is the radius of curvature, R, of the most object-side surface of the first cemented lens c1-3 Radius of curvature, R, of a joint surface on the image side of both joint surfaces of the first joint lens c1-4 Is the radius of curvature of the surface of the first cemented lens closest to the image side.
A zoom lens according to an embodiment of the present invention takes a structure in which a second cemented lens having two negative and positive lenses that are placed in order from an object side and cemented with each other is placed on an image side of a first cemented lens; the zoom lens satisfies the conditional expression:
68＜v c2-2 ＜98，
wherein v is c2-2 Is the abbe number of the positive lens in the second cemented lens.
A zoom lens according to an embodiment of the present invention takes a structure in which the second cemented lens is placed on the image side of the first cemented lens, and at least one positive lens is placed on the object side of the first cemented lens.
A zoom lens according to an embodiment of the present invention takes a structure in which at least one positive lens placed on the object side of a first cemented lens has at least one aspherical surface.
[0032]
A zoom lens according to an embodiment of the present invention takes a structure in which the first cemented lens is constituted with only an aspherical surface, and the second lens group includes at least one aspherical surface.
As a photographing optical system, a photographing apparatus according to an embodiment of the present invention has a zoom lens according to an embodiment of the present invention.
A personal digital assistant according to an embodiment of the present invention has a zoom lens according to an embodiment of the present invention as a photographing optical system of an imaging function section of a photographing apparatus.
Next, embodiments and functions of the present invention will be specifically explained.
In the zoom lens according to the present invention, in the zoom lens in which the first lens group having a negative refractive power and the second lens group having a positive refractive power are disposed in order from the object side, in general, the second lens group monotonously moves from the image side to the object side with changing the magnification number from the wide angle end to the telephoto end. The first lens group is moved to correct variation in the position of the image plane due to changing the magnification. A third lens group having a positive refractive power may be added to distance the viewpoint from the image plane, or to achieve rear focusing (rear focusing). In this case, the second group of lenses plays a major role in changing the magnification.
[0033]
In order to realize a zoom lens with low aberration and high resolution, it is necessary to reduce aberration variation (aberration fluctuation) caused by changing the magnification; especially, the second lens group as the one that mainly varies the magnification needs to achieve ideal aberration correction in the entire range of magnification variation. In particular, in order to realize a wider angle of view at a short focal end, that is, at a wide-angle end, it is necessary to reduce chromatic aberration of magnification, which increases as the angle of view is wider. The structure of the second lens is still very important in order to achieve ideal chromatic aberration of magnification correction over the entire range of magnification variation.
As the structure of the second lens group, three-piece structures of positive lens/negative lens/positive lens, three-piece structures of positive lens/negative lens, four-piece structures of positive lens/negative lens/positive lens, and four-piece structures of positive lens/negative lens/positive lens, and the like may be placed in order from the object side. Known structures are those comprising two sets of cemented lenses and those comprising three cemented lenses.
The structure of the second lens group according to the present invention is superior to the conventional existing or well-known structure, and has a higher capability of correcting aberrations; it is also desirable to realize a zoom lens of high performance, small size, wide angle of view while suppressing an increase in cost.
[0034]
Specifically, in the present invention, the second lens group is configured to include a first cemented lens composed of at least three lens cemented, and a second cemented lens composed of at least two lens cemented. The reason is as follows:
first, the three cemented surfaces in the second lens group all have different distances from the aperture stop, and the axial rays and the off-axial rays have different paths. Now if only the chromatic aberration needs to be corrected, the two joint surfaces can realize the independent correction of the axial chromatic aberration and the magnification chromatic aberration to a certain extent, thereby obtaining enough high performance. However, if it is necessary to consider both correction of the off-axis monochromatic aberration (coma, astigmatism) and chromatic aberration, it is necessary to control the curvature of at least one of the two joining surfaces. Therefore, by providing one more joint surface, the degree of freedom for correcting chromatic aberration can be secured, so that both monochromatic aberration correction and chromatic aberration correction can be maintained at a high level.
[0035]
In order to provide the second lens group having three cemented surfaces, three pairs of cemented lenses may be employed. However, the three pairs of cemented lenses require six lenses, which is disadvantageous for achieving a small size. Also in order to suppress deterioration of imaging performance due to decentering between the lenses during assembly, it is necessary to make two faces of the three joint faces constitute three joint lenses. If the priority for downsizing and reducing lens shift is highest, four cemented lenses having three cemented surfaces may be used. However, such a structure may largely impair the degree of freedom in correcting monochromatic aberrations. Accordingly, the inventors of the present patent application consider a method of using three cemented lenses and two cemented lenses to provide three cemented surfaces. In order to suppress color blur around an image, it is necessary to effectively correct difference between the magnification chromatic aberration and the coma aberration, that is, the coma aberration shape due to the wavelength. Therefore, the method of the present invention has a good effect, and can ensure a greater degree of freedom in chromatic aberration correction than the conventional method.
[0036]
The above structure of the second lens group is very effective, particularly in the case where the half angle of view exceeds 40 degrees at the wide angle end, by which it is possible to achieve very desirable chromatic aberration correction, particularly chromatic aberration of magnification and coma, while off-axis monochromatic aberration, which increases as the angle of view widens, can be effectively suppressed. Therefore, the first lens group having a large lens diameter can obtain a sufficiently wide angle of view without using special low dispersion glass, and can suppress an increase in the overall cost.
It is generally desirable to add a positive third lens group to form a negative/positive three-group structure. The addition of the third lens group having a positive refractive power not only makes it easy to secure the viewpoint height, but also enables focusing by moving the third lens group.
In addition to the chromatic aberration correction, in order to achieve ideal monochromatic aberration correction such as spherical aberration and astigmatism, the second cemented lens is preferably placed on the image side of the first cemented lens. Both a surface of the first cemented lens closest to the image side and a surface of the first cemented lens closest to the object side are convex toward the object side, and the second cemented lens has a positive refractive index as a whole.
[0037]
Making the first cemented lens in a meniscus shape with the convex surface facing the convex object side as a whole will generate aberrations in opposite directions at the entrance surface and the exit surface, so that ideal aberration correction can be achieved as a whole. Also, placing the second cemented lens having a positive refractive power on the image side of the first cemented lens, in which the surface of the first cemented lens closest to the image side has a negative refractive power set at the center, makes it easy for the second lens group to have a positive/negative/positive symmetrical structure. Therefore, both the chromatic aberration correction and the curvature correction of the field are kept at a high level.
The first cemented lens may be composed of a positive lens, a negative lens, and a positive lens that are placed in order from the object side and cemented to each other.
In the case where the second lens group simultaneously corrects axial chromatic aberration and chromatic aberration of magnification using only one cemented lens group, it is preferable to select three cemented lenses cemented in the order of negative lens/positive lens/negative lens. However, if two sets of cemented lenses according to the present invention are used, the first cemented lens and the second cemented lens can collectively perform correction of axial chromatic aberration and chromatic aberration of magnification; the two situations are not related to each other. In the overall structure, the first cemented lens is made into a positive/negative/positive triplet structure, and the second cemented lens having a positive refractive index is placed on the image side, so that the positive power can be kept away from the aperture stop, thereby facilitating correction of off-axis aberration; therefore, the degree of freedom of chromatic aberration correction is increased, thereby facilitating the realization of a wider angle of view.
[0038]
When the first cemented lens has a positive lens, a negative lens, and a positive lens that are placed in order from the object side and cemented to each other, in order to achieve ideal aberration correction, the lenses preferably satisfy the following conditional expressions:
1.65＜n c1-1 ＜1.90，
1.65＜n c1-2 ＜1.90，
4＜v c1-1 -v c1-2 ＜25，
68＜v c1-3 ＜98，
wherein n is c1-1 Is a refractive index of a positive lens on the object side of the first cemented lens, n c1-2 Is the refractive index, v, of the negative lens in the first cemented lens c1-1 Is the Abbe number, v, of the positive lens on the object side of the first cemented lens c1-2 Is the Abbe number, v, of the negative lens in the first cemented lens c1-3 Is the abbe number of the positive lens on the image side of the first cemented lens.
[0039]
More specifically, n is preferably n c1-1 And n c1-2 Greater than 1.65 and less than 1.90. If n is c1-1 Or n c1-2 Less than 1.65, the surface curvature of the refractive index required to obtain chromatic aberration correction becomes large, and excessive chromatic aberration occurs, which is undesirable. If n is c1-1 Or n c1-2 1.90 or more, the optional glass type is limited and it is difficult to obtain a balanced color difference. With respect to the equilibrium color difference, v c1-1 And v c1-2 It is required to be limited to a predetermined range, that is, v c1-1 -v c1-2 Greater than 4 and less than 25 if v c1-1 -v c1-2 When the value is 4 or less, it becomes difficult to exhibit the effect of chromatic aberration correction obtained by the joint surface on the object side. If v is c1-1 -v c1-2 When the value is 25 or more, it becomes difficult to obtain balanced axial chromatic aberration and magnification chromatic aberration. Further, v c1-3 Is required to be greater than 68 and less than 98. If v is c1-3 Equal to or less than 68, correction of the secondary spectrum of the chromatic aberration may be insufficient. It is difficult to obtain v c1-3 A type equal to or greater than 98 is not practical, or the type is very costly.
[0040]
In the first cemented lens in which a positive lens, a negative lens, and a positive lens cemented with each other are placed in order from the object side, in order to achieve small size and workability, the following conditional expressions need to be satisfied:
0.10＜d c1-2 /d c1-a11 ＜0.19，
wherein d is c1-2 Is the central thickness of the negative lens in the first cemented lens, measured along the optical axis of the lens, d c1-a11 Is the center thickness of all of the first cemented lenses.
In other words, d c1-2 /d c1-a11 Is required to be less than 0.19 and greater than 0.1. If d is c1-2 /d c1-a1 When 0.10 or less, the center thickness of the negative lens becomes too thin, resulting in difficulty in processing. If d is c1-2 /d c1-a1 When 0.19 or more, the peripheral thickness of the positive lens becomes too thin, resulting in difficulty in processing. In any case, increasing the center thickness of all of the cemented lenses would cause the processing to exceed the range of the conditional expressions; however, this would prevent the reduction in size, which is undesirableAnd (4) raw.
[0041]
In the first cemented lens in which a positive lens, a negative lens, and a positive lens cemented with each other are placed in order from the object side, in order to achieve ideal monochromatic aberration and chromatic aberration correction, the following conditional expressions need to be satisfied:
0.2＜(R c1-1 -R c1-3 )/(R c1-1 +R c1-3 ) < 0.5, and
-0.4＜(R c1-3 -R c1-4 )/(R c1-3 +R c1-4 )＜-0.1，
wherein R is c1-1 Is the radius of curvature, R, of the surface of the first cemented lens closest to the object side c1-3 Radius of curvature, R, of a cemented surface on the image side of the two cemented surfaces of the first cemented lens c1-4 Is the radius of curvature of the surface of the first cemented lens closest to the image side.
[0042]
In other words, (R) c1-1 -R c1-3 )/(R c1-1 +R c1-3 ) Is required to be greater than 0.2 and less than 0.5, (R) c1-3 -R c1-4 )/ (R c1-3 +R c1-4 ) Is required to be greater than-0.4 and less than-0.1. If (R) c1-1 -R c1-3 )/(R c1-1 +R c1-3 ) Equal to or less than 0.2, or if (R) c1-3 -R c1-4 )/(R c1-3 +R c1-4 ) Equal to or greater than-0.1, the refractive index of each of the first cemented lens becomes too large, resulting in excessively high aberration, which is difficult to be achievedTo obtain balanced aberrations.
If (R) c1-1 -R c1-3 )/(R c1-1 +R c1-3 ) Equal to or greater than 0.5, or if (R) c1-3 -R c1-4 )/(R c1-3 +R c1-4 ) Equal to or less than-0.4, the refractive index of each of the first cemented lenses is too weak, and it is easy to make the correction of monochromatic aberration and chromatic aberration insufficient.
In the zoom lens of the present invention, in order to achieve ideal chromatic aberration of magnification correction, the second cemented lens needs to be placed on the image side of the first cemented lens, and the second cemented lens has a negative lens and a positive lens placed in order from the object side and cemented with each other, and the zoom lens satisfies the following conditional expression:
68＜v c2-2 ＜98，
wherein v is c2-2 Is the abbe number of the positive lens in the second cemented lens.
[0043]
The second cemented lens placed on the image side of the cemented lens is far from the aperture stop and greatly contributes to the off-axis correction. In this case, the second cemented lens plays a great role in chromatic aberration of magnification correction, and by adopting the above configuration, the best effect is achieved. In particular, v c2-2 Is required to be greater than 68 and less than 98. If v is c2-2 Equal to or less than 68, correction of the secondary spectrum of chromatic aberration cannot be sufficiently achieved. On the other hand, it is difficult to obtain v c2-2 98 or more glass, or such glass is extremely costly and impractical.
[0044]
Since the diameter of the lens is relatively small, the positive lens of the second cemented lens can be made of not only a glass with low dispersion but also a glass with particularly low dispersion. Thus, a lens can be provided with particularly low dispersion glass, achieving ideal aberration correction.
In the zoom lens of the present invention, in order to achieve ideal chromatic aberration correction, the second cemented lens is required to be placed on the image side of the first cemented lens, and at least one positive lens is placed on the object side of the first cemented lens. In other words, the second lens group adopts a structure in which a positive lens, a first cemented lens, and a second cemented lens are placed in order from the image side. Also, in order to achieve ideal spherical aberration and coma aberration correction, at least one aspherical surface is applied to at least one positive lens placed on the object side of the first cemented lens.
Further, in the second lens group, it is required that the first cemented lens is provided with only a spherical surface, and the other lenses than the second cemented lens include at least one aspherical surface. Since the first cemented lens described above is provided with at least three cemented lenses, control of decentering of the lenses in the process of cementing the lenses becomes complicated. If the first cemented lens is provided with an aspherical surface, the imaging performance is deteriorated by decentering the lens during the lens cementing process.
[0045]
The second lens group relating to the zoom lens of the present invention may be configured such that a positive lens, a first cemented lens, and a second cemented lens are disposed in this order from the object side. Here, the first cemented lens is provided with three lenses of a convex surface facing the convex object side, a negative lens facing a concave surface facing the image side, and a positive meniscus lens facing a convex surface facing the convex object side, which are placed in order from the object side and cemented to each other; the second cemented lens is provided with two lenses, a negative meniscus lens and a positive lens, which are placed in order from the object side and cemented to each other, and have convex surfaces facing the convex side toward the image side. The three groups of structures formed by the six lenses adopt the overall layout of positive, negative, positive, negative and positive; in this way, the refractive index layout is close to symmetrical, resulting in well balanced aberration correction.
To achieve better aberration correction, the second lens group may use a plurality of aspherical surfaces. Here, it is required that two aspherical surfaces are used for the lens closest to the object side and the lens closest to the image side. The lens closest to the object side is close to the aperture stop, thereby facilitating correction of spherical aberration and coma. The lens closest to the image side is away from the aperture stop and the off-axis light beams pass through the lens, respectively, to some extent, thereby facilitating correction of astigmatic aberration in addition to correction of spherical aberration and coma.
[0046]
The above-described structure of the second lens adds many features to the zoom lens according to the present invention, and further description will be given in order to obtain better performance of the zoom lens. The first lens group requires a cemented lens provided with a negative meniscus lens, a negative lens and a positive lens facing a concave surface facing the image side, which are placed in order from the object side, or four lenses divided into three groups, a negative meniscus lens, a negative lens, a positive lens and a negative lens facing a concave surface facing the image side, which are placed in order from the object side, respectively. Since two negative lenses are disposed on the object side of the first lens group, the four surfaces of the two negative lenses gradually refract off-axis light beams having a large incident angle, and therefore, the occurrence of a drop in off-axis aberration can be suppressed.
To achieve better monochromatic aberration correction, a first lens group having one or more aspheric surfaces may be provided. In particular, an aspherical surface is provided for the image side surface of any one of two negative lenses placed on the object side. Introducing an aspherical surface at this position can effectively correct distortion, astigmatism, and the like, particularly at the short focal end.
[0047]
The third lens group is composed of a positive lens facing a surface having a large curvature toward the object side, and is required to have at least one aspherical surface. Although the thickness of the third lens group is suppressed to the minimum, this structure can better correct off-axis aberrations such as astigmatism. In the case where only one positive lens is disposed in the third lens group, it is necessary to use nitrate with as small dispersion as possible from the viewpoint of correcting chromatic aberration.
The third group of lenses may be fixed during the changing of the magnification; however, a small movement will increase the freedom of aberration correction.
To simplify the mechanism, it is required that the opening diameter of the aperture stop is fixed to a constant regardless of the change in magnification. However, by making the opening diameter larger at the long focal end (telephoto end) rather than at the short focal end (wide-angle end), it is possible to reduce the variation in F-number (F-number) while changing the magnification. When it is necessary to reduce the amount of light reaching the image plane, the aperture stop can be made smaller; it is then preferable to reduce the amount of light by inserting a filter for ND (medium density) because this can prevent the resolution from being lowered due to the diffraction phenomenon.
[0048]
The following lenses may be employed as the aspherical lens: lenses molded from optical glass and optical plastic (glass-molded aspherical lenses, plastic-molded aspherical lenses), lenses in which a thin resin layer is formed on the plane of a glass lens, the surface of the resin layer is made aspherical (referred to as a hybrid aspherical lens, or a replica aspherical lens), and the like.
A photographing apparatus configured with the above-described zoom lens as a photographing optical system can achieve higher image quality with a high resolution while having a smaller size because the zoom lens can achieve a sufficiently wide half angle of view of 42 degrees or more, desirably correct chromatic aberration, particularly chromatic aberration of magnification and coma, in a wide-angle end, and can achieve a resolving power corresponding to an imaging device having 800 to 1000 ten thousand pixels or more in the case of a smaller size.
A personal digital assistant configuring the zoom lens described earlier as a photographing optical system can achieve higher image quality with high resolution while having a smaller size because the zoom lens can achieve a sufficiently wide half angle of view of 42 degrees or more in the wide-angle end, desirably correct chromatic aberration, particularly chromatic aberration of magnification and coma, and can achieve a resolving power corresponding to an imaging device having 800 to 1000 ten thousand pixels or more in the case of a smaller size.
Example 1
[0049]
Next, based on the foregoing embodiments of the invention, specific examples will be described in detail. Hereinafter, embodiment 1, embodiment 2, embodiment 3, embodiment 4, and embodiment 5 are specific configuration examples based on specific numerical examples of the zoom lens of the present invention. Here, an embodiment of a photographing apparatus or a personal digital assistant according to the present invention will be described later, with a lens unit composed of the zoom lens described in embodiment 1 to embodiment 5 as a photographing optical system.
Optical elements composed of parallel flat plates disposed on the image surface side of the third lens group in embodiments 1 to 4, or disposed on the image surface side of the second lens group in embodiment 5 are assumed to be optical filters such as an optical low-pass filter and an infrared cut filter, and cover glasses (shielding glasses) of light receiving elements such as CCD detectors; herein, referred to as various filters.
[0050]
In embodiment 1 to embodiment 5, a surface of the first lens group closest to the image side of the lens on the object side, and a surface of the second lens group closest to the object side and a surface closest to the image side are aspheric; in embodiments 1 to 4, a surface of the third lens group closest to the image side is an aspherical surface. Here, regarding the aspherical surfaces in embodiments 1 to 5, it is assumed that the surface of each lens is directly made aspherical, similarly to a so-called molded aspherical lens. However, the aspherical lens may be a so-called hybrid aspherical lens (hybrid aspherical lens) in which a thin resin layer having an aspherical surface is attached on a spherical lens to obtain an equivalent aspherical surface.
The aberrations in embodiments 1 to 5 are sufficiently corrected, and the performance of the zoom lens can correspond to a light receiving element having 800 to 1000 ten thousand or more pixels. As is apparent from embodiment 1 to embodiment 5, the zoom lens configured according to the present invention can achieve a desired imaging performance while achieving a sufficiently small size.
[0051]
The symbols and meanings in example 1 to example 5 are as follows:
[0052]
f: focal length of the whole system
F: f number
ω: half angle of view
R: radius of curvature
D: spacing between inner surfaces
N d : refractive index
v d : abbe number
K: conic constant of aspheric surface
A 4 : fourth order aspherical surface coefficient
A 6 : coefficient of six aspheric surfaces
A 8 : coefficient of eight aspheric surfaces
A 10 : ten order aspheric surface coefficient
A 12 : coefficient of twelve aspheric surfaces
A 14 : fourteen aspheric coefficients
A 16 : coefficient of sixteen aspheric surfaces
A 18 : coefficient of eighteenth order aspheric surface
The aspherical surface used here is given by the following formula.
[0053]
[ equation 1]
Wherein C is paraxial curveInverse of the radius of curvature (paraxial curvature), H being the height from the optical axis, A 4 ，A 6 ，A 8 … … is an aspheric coefficient.
[0054]
Fig. 1 illustrates a structure of an optical system of a zoom lens according to embodiment 1, and in fig. 1, arrows indicate moving trajectories of each lens group from a short focal end, i.e., a wide-angle end, to a long focal end, i.e., a telephoto end, through an intermediate focal length during zooming.
The zoom lens shown in fig. 1 includes a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, a tenth lens E10, a tenth lens E11, an aperture stop FA, and various filters MF. In this case, the first lens E1 to the fourth lens E4 constitute a first lens group G1, the fifth lens E5 to the tenth lens E10 constitute a second lens group G2, and the eleventh lens E11 constitutes the third lens group G3 alone, each lens group being supported by an appropriate common structure. In the zooming operation, each lens group moves together as a whole, and the aperture stop FA and the second lens group G2 move together. Fig. 1 also shows the number of surfaces per optical surface. Here, the reference numerals of fig. 1 are used independently of the other embodiments, so that description confusion due to the increase in the number in the reference numerals can be avoided; in other words, each specific structure is given a separate reference numeral. Therefore, the same reference numerals in fig. 2 to 5 do not necessarily represent the same elements as those of the other embodiments.
[0055]
In fig. 1, optical elements constituting an optical system of the zoom lens are disposed in order from the object side of the object to be photographed, such as a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, an aperture stop FA, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, a tenth lens E10, an eleventh lens E11, and various filters MF. An image is formed behind the various filters MF.
The first lens E1 is a negative meniscus lens convex toward the object side, and has an aspherical surface on the image side. The second lens E2 is a negative lens, both surfaces of which are concave surfaces. The third lens E3 is a positive lens, and its surfaces are all convex surfaces. The fourth lens E4 is a negative lens, and both surfaces thereof are concave surfaces. The two pieces of the third lens E3 and the fourth lens E4 are adhered integrally to form a cemented lens C0, and the first lens group G1 composed of the first lens E1 to the fourth lens E4 has a negative refractive index as a whole.
[0056]
The fifth lens E5 is a positive meniscus lens convex toward the object side, and has an aspherical surface on the object side. The sixth lens E6 is a positive meniscus lens convex toward the object side. The seventh lens E7 is a negative meniscus lens convex toward the object side. The eighth lens E8 is a positive meniscus lens convex toward the object side. The sixth lens E6 to the eighth lens E8 are integrally adhered to form a first cemented lens C1. The ninth lens E9 is a negative meniscus lens convex toward the object side. The tenth lens E10 is a positive lens having an aspherical surface on the image side, and both surfaces thereof are convex surfaces. The ninth lens E9 and the tenth lens E10 are integrally adhered to form a second cemented lens C2. The second lens group G2 composed of the fifth lens E5 to the tenth lens E1 has a positive refractive index as a whole.
[0057]
The eleventh lens E11 is a positive lens having an aspherical surface on the image side, and both surfaces thereof are convex surfaces. The eleventh lens E11 alone constitutes the third lens group G3, and has a positive refractive power.
When the magnification is varied between the short focal end, i.e., the wide-angle end, and the long focal end, i.e., the telephoto end, the variable interval between the lens groups varies, i.e., the interval DA between the surface of the first lens group G1 closest to the image side, i.e., the image side surface (surface number 7) of the fourth lens E4, and the aperture stop FA (surface number 8) disposed at the object side of the second lens group G2 moving together with the second lens group G2, the surface of the second lens group G2 closest to the image side, i.e., the image side surface (surface number 17) of the tenth lens E10 and the surface of the third lens group G3 closest to the object side, i.e., the interval DB between the surface of the object side of the eleventh lens (surface 18), the surface of the third lens group G3 closest to the image side, i.e., the image side surface (surface 19) of the eleventh lens E11, and the surface of the object side (surface 20) of the various filter MF, DC varies. And, as the magnification varies from the wide-angle end to the telephoto end, the first lens group G1, the second lens group G2, and the third lens group G3 move in such a manner that the interval DA between the first lens group G1 and the aperture stop FA (moving integrally with the second lens group G2) gradually decreases, the interval DB between the second lens group G2 and the third lens group G3 gradually increases, and the interval DC between the third lens group G3 and the different type filter MF temporarily increases and then decreases. In the movement varying with the magnification from the wide-angle end to the telephoto end, the second lens group G2 is moved almost monotonously to the object side, the first lens group G1 is moved to the image side temporarily, and then moved to the object side, and the third lens group G3 is moved to the object side temporarily, and then moved to the image side.
In embodiment 1, the focal length F, F-number F, and half angle of view ω of the entire system are changed during zooming in the following ranges: f =5.204-14.996, f =2.66-4.67, ω =43.26-17.51. The optical properties of the optical element are given in the table below.
[0058]
[ Table 1]
Optical characteristics
| Number of surfaces | R | D | N d | v d | Marking | Name of glass type |
| 01 | 24.422 | 1.60 | 1.73310 | 48.89 | E1 | OHARA L-LAM72 |
| 02* | 9.225 | 4.11 | ||||
| 03 | -180.153 | 1.20 | 1.77250 | 49.60 | E2 | OHARA S-LAH66 |
| 04 | 11.584 | 4.10 | ||||
| 05 | 20.498 | 3.55 | 1.80100 | 34.97 | E3 | OHARA S-LAM66 |
| 06 | -34.360 | 1.00 | 1.75700 | 47.82 | E4 | OHARA S-LAM54 |
| 07 | 232.236 | (DA) Variable | ||||
| 08 | Aperture diaphragm | 1.00 | FA | |||
| 09* | 8.821 | 1.56 | 1.77250 | 49.60 | E5 | OHARA S- |
| 10 | 2.899 | 0.10 | ||||
| 11 | 7.072 | 1.45 | 1.80440 | 39.59 | E6 | OHARA S- |
| 12 | 11.355 | 0.70 | 1.80100 | 34.97 | E7 | OHARA S- |
| 13 | 3.897 | 2.25 | 1.48749 | 70.24 | E8 | OHARA S- |
| 14 | 6.572 | 0.33 | ||||
| 15 | 11.142 | 0.60 | 1.74950 | 35.28 | E9 | OHARA S- |
| 16 | 4.205 | 2.13 | 1.49700 | 81.54 | E10 | OHARA S- |
| 17* | -100.000 | (DB) Variable | ||||
| 18 | 12.952 | 2.50 | 1.43875 | 94.94 | E11 | OHARA S- |
| 19* | -153.191 | (DC) Variable | ||||
| 20 | ∞ | 1.24 | 1.51680 | 64.20 | |
|
| 21 | ∞ | |||||
[0059]
In table 1, the numbers of the second surface, the ninth surface, the seventeenth surface and the nineteenth surface marked with asterisk are aspheric surfaces, and the parameters of the aspheric surfaces in formula (1) are as follows.
Aspheric surface: second surface
K＝0.0
A 4 ＝-1.28414×10 -4
A 6 ＝-6.57446×10 -7
A 8 ＝-6.30308×10 -9
A 10 ＝-1.72874×10 -10
A 12 ＝-2.57252×10 -12
A 14 ＝2.13910×10 -14
A 16 ＝7.39915×10 -16
A 18 ＝-1.13603×10 -17
[0060]
Aspheric surface: ninth surface
K＝0.0
A 4 ＝-7.05273×10 -5
A 6 ＝5.04003×10 -7
A 8 ＝-6.78678×10 -8
A 10 ＝1.47308×10 -9
Aspheric surface: seventeenth aspect of the invention
K＝0.0
A 4 ＝4.43634×10 -5
A 6 ＝1.20686×10 -5
A 8 ＝-4.69301×10 -6
A 10 ＝1.28473×10 -7
Aspherical surface: the nineteenth aspect
K＝0.0
A 4 ＝6.54212×10 -5
A 6 ＝-8.10291×10 -6
A 8 ＝1.98320×10 -7
A 10 ＝-2.19065×10 -9
A variable interval DA between the first lens group G1 and the aperture stop FA (second lens group G2), a variable interval DB between the second lens group G2 and the third lens group G3, and a variable interval DC between the third lens group G3 and the various filters MF are varied during zooming as shown in the following table.
[0061]
[ Table 2]
Variable spacing
| Short focus end | Intermediate focal length | Long focal point end | |
| f | 5.20 | 8.83 | 15.00 |
| DA | 21.349 | 7.868 | 1.825 |
| DB | 3.669 | 7.448 | 17.837 |
| DC | 4.009 | 4.883 | 2.771 |
[0062]
The values relating to the conditional expressions described above in example 1 are as follows.
Value of conditional expression
n c1-1 ＝1.80440
n c1-2 ＝1.80100
v c1-1 -v c1-2 ＝4.62
v c1-3 ＝70.24
d c1-2 /d c1-a11 ＝0.159
(R c1-1 -R c1-3 )/(R c1-1 +R c1-3 )＝0.289
(R c1-3 -R c1-4 )/(R c1-3 +R c1-4 )＝-0.256
v c2-2 ＝81.54
Therefore, the aforementioned numerical values relating to the aforementioned conditional expressions in example 1 are within the ranges of the conditional expressions.
Example 2
[0063]
Fig. 2 shows a structure of an optical system of a zoom lens relating to embodiment 2, and in fig. 2, arrows indicate moving loci of each lens group from a short focal end (wide-angle end) to a long focal end (telephoto end) through an intermediate focal length during zooming.
The zoom lens shown in fig. 2 includes a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, a tenth lens E10, a tenth lens E11, an aperture stop FA, and various filters MF. In this case, the first lens E1 to the fourth lens E4 constitute a first lens group G1, the fifth lens E5 to the tenth lens E10 constitute a second lens group G2, and the eleventh lens E11 individually constitutes a third lens group G3, each lens group being supported by an appropriate common structure. In the zooming operation, each lens group moves together as a whole, and the aperture stop FA and the second lens group G2 move together. Fig. 2 also shows the number of surfaces per optical surface. Here, the reference numerals of fig. 2 are used independently of the other embodiments, so that description confusion due to the increase in the number in the reference numerals can be avoided; in other words, each specific structure is given a separate reference numeral. Thus, like reference numerals in fig. 1, 3, and 4 do not necessarily refer to like elements in other embodiments.
[0064]
In fig. 2, the optical elements constituting the optical system of the zoom lens are disposed, in order from the object side, a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, an aperture stop FA, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, a tenth lens E10, an eleventh lens E11, and various filters MF. An image is formed behind the various filters MF.
The first lens E1 is a negative meniscus lens convex toward the object side, and has an aspherical surface on the image side. The second lens E2 is a negative lens, and both surfaces thereof are concave surfaces. The third lens E3 is a positive lens, and both surfaces thereof are convex surfaces. The fourth lens E4 is a negative lens, and both surfaces thereof are concave surfaces. The two pieces of the third lens E3 and the fourth lens E4 are adhered integrally to form a cemented lens C0, and the first lens group G1 composed of the first lens E1 to the fourth lens E4 has a negative refractive index as a whole.
[0065]
The fifth lens E5 is a positive meniscus lens convex toward the object side, and has an aspherical surface on the object side. The sixth lens E6 is a positive meniscus lens convex toward the object side. The seventh lens E7 is a negative meniscus lens convex toward the object side. The eighth lens E8 is a positive meniscus lens convex toward the object side. The sixth lens E6 to the eighth lens E8 are integrally adhered to form a first cemented lens C1. The ninth lens E9 is a negative meniscus lens convex toward the object side. The tenth lens E10 is a positive lens having an aspherical surface on the image side, and both surfaces thereof are convex surfaces. The ninth lens E9 and the tenth lens E10 are integrally adhered to form a second cemented lens C2. The second lens group G2 composed of the fifth lens E5 to the tenth lens E10 has a positive refractive power as a whole.
The eleventh lens E11 is a positive lens having an aspherical surface on the image side, and both surfaces thereof are convex surfaces. The eleventh lens E11 alone constitutes the third lens group G3, and has a positive refractive power.
[0066]
When the magnification is changed between the short focal end (wide-angle end) and the long focal end (telephoto end), the variable intervals between the lens groups are changed, that is, the interval DA between the face of the first lens group G1 closest to the image side, that is, the face of the fourth lens E4 on the image side (the number of faces 7) and the face of the aperture stop FA placed at the object side of the second lens group G2 moving together with the second lens group G2 (the number of faces 8), the face of the second lens group G2 closest to the image side, that is, the face of the tenth lens E10 on the image side (the number of faces 17) and the face of the third lens group G3 closest to the object side, that is, the interval DB between the face of the eleventh lens on the object side (the face 18), the face of the third lens group G3 closest to the image side, that is, the face of the eleventh lens E11 on the image side (the face 19) and the face of the object side (the face of the various filters MF 20). And, as the magnification is varied from the wide-angle end to the telephoto end, the first lens group G1, the second lens group G2, and the third lens group G3 move in such a manner that the interval DA between the first lens group G1 and the aperture stop FA (moving integrally with the second lens group G2) gradually decreases, the interval DB between the second lens group G2 and the third lens group G3 gradually increases, and the interval DC between the third lens group G3 and the various types of filters MF temporarily increases and then decreases. In the movement with the magnification varying from the wide-angle end to the telephoto end, the second lens group G2 is moved almost monotonously to the object side, the first lens group G1 is temporarily moved to the image side and then moved to the object side, and the third lens group G3 is temporarily moved to the object side and then moved to the image side.
In embodiment 2, the focal length F, F-number F, and half angle of view ω of the entire system are changed during zooming in the following ranges: f =5.204-14.993, f =2.64-4.59, ω =43.27-17.51. The optical properties of the optical element are given in the table below.
[0067]
[ Table 3]
Optical characteristics
| Number of surfaces | R | D | N d | v d | Marking | Name of glass type |
| 01 | 23.933 | 1.60 | 1.73310 | 48.89 | E1 | OHARA L-LAM72 |
| 02* | 9.257 | 4.18 | ||||
| 03 | -120.099 | 1.20 | 1.77250 | 49.60 | E2 | OHARA S-LAH66 |
| 04 | 11.127 | 3.62 | ||||
| 05 | 19.306 | 3.69 | 1.80100 | 34.97 | E3 | OHARA S-LAM66 |
| 06 | -32.934 | 1.00 | 1.75700 | 47.82 | E4 | OHARA S-LAM54 |
| 07 | 336.795 | (DA) Variable | ||||
| 08 | Aperture diaphragm | 1.00 | ||||
| 09* | 7.961 | 1.68 | 1.77250 | 49.60 | E5 | OHARA S- |
| 10 | 27.338 | 0.65 | ||||
| 11 | 8.555 | 1.36 | 1.74320 | 49.34 | E6 | OHARA S- |
| 12 | 15.735 | 0.70 | 1.80100 | 34.97 | E7 | OHARA S- |
| 13 | 4.000 | 2.19 | 1.48749 | 70.24 | E8 | OHARA S- |
| 14 | 6.098 | 0.35 | ||||
| 15 | 10.495 | 0.61 | 1.69895 | 30.13 | E9 | OHARA S- |
| 16 | 6.280 | 1.84 | 1.43875 | 94.94 | E10 | OHARA S- |
| 17* | -75.820 | (DB) Variable | ||||
| 18 | 12.809 | 2.50 | 1.43875 | 94.94 | E11 | OHARA S- |
| 19* | -282.974 | (DC) Variable | ||||
| 20 | ∞ | 1.24 | 1.51680 | 64.20 | |
|
| 21 | ∞ | |||||
[0068]
In table 3, the numbers of the second surface, the ninth surface, the seventeenth surface and the nineteenth surface marked with asterisks on the surfaces are aspheric surfaces, and the parameters of the aspheric surfaces in formula (1) are as follows.
Aspheric surface: second surface
A 4 ＝-1.32978×10 -4
A 6 ＝-7.12156×10 -7
A 8 ＝-5.44124×10 -9
A 10 ＝-1.64121×10 -10
A 12 ＝-3.45408×10 -12
A 14 ＝2.29505×10 -14
A 16 ＝9.05635×10 -16
A 18 ＝-1.23794×10 -17
[0069]
Aspheric surface: ninth surface
K＝0.0
A 4 ＝-1.04029×10 -4
A 6 ＝-2.77447×10 -7
A 8 ＝-6.56948×10 -8
A 10 ＝1.04196×10 -9
Aspheric surface: seventeenth aspect of the invention
K＝0.0
A 4 ＝1.48398×10 -4
A 6 ＝1.72916×10 -5
A 8 ＝-3.99171×10 -6
A 10 ＝1.80296×10 -7
Aspheric surface: the nineteenth aspect
K＝0.0
A 4 ＝7.02797×10 -5
A 6 ＝-7.99511×10 -6
A 8 ＝1.94122×10 -7
A 10 ＝-2.22699×10 -9
A variable interval DA between the first lens group G1 and the aperture stop FA (second lens group G2), a variable interval DB between the second lens group G2 and the third lens group G3, and a variable interval DC between the third lens group G3 and the various filters MF are varied during zooming as shown in the following table.
[0070]
[ Table 4]
Variable spacing
| Short focus end | Intermediate focal length | Long focal point end | |
| f | 5.20 | 8.83 | 14.99 |
| DA | 21.394 | 7.964 | 1.817 |
| DB | 3.670 | 7.459 | 17.706 |
| DC | 3.942 | 4.803 | 2.819 |
[0071]
The values relating to the conditional expressions described above in example 2 are as follows.
Value of conditional expression
n c1-1 ＝1.77250
n c1-2 ＝1.80100
v c1-1 -v c1-2 ＝14.37
v c1-3 ＝70.24
d c1-2 /d c1-a11 ＝0.165
(R c1-1 -R c1-3 )/(R c1-1 +R c1-3 )＝0.363
(R c1-3 -R c1-4 )/(R c1-3 +R c1-4 )＝-0.208
v c2-2 ＝94.94
Therefore, the aforementioned numerical values relating to the aforementioned conditional expressions in example 2 are within the ranges of the conditional expressions.
Example 3
[0072]
Fig. 3 shows the structure of an optical system of a zoom lens relating to embodiment 3, and in fig. 3, arrows indicate moving loci of each lens group from a short focal end (wide-angle end) to a long focal end (telephoto end) through an intermediate focal length during zooming.
The zoom lens shown in fig. 3 includes a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, a tenth lens E10, a tenth lens E11, an aperture stop FA, and various filters MF. In this case, the first lens E1 to the fourth lens E4 constitute a first lens group G1, the fifth lens E5 to the tenth lens E10 constitute a second lens group G2, and the eleventh lens E11 constitutes the third lens group G3 alone, each lens group being supported by an appropriate common structure. In the zooming operation, each lens group moves together as a whole, and the aperture stop FA and the second lens group G2 move together. Fig. 3 also shows the number of surfaces per optical surface. Here, the reference numerals of fig. 3 are used independently of the other embodiments, so that description confusion due to the increase in the number in the reference numerals can be avoided; in other words, each specific structure is given a separate reference numeral. Thus, the same reference numerals of fig. 1, 2, and 4 do not necessarily represent the same elements in other embodiments.
[0073]
In fig. 3, the optical elements constituting the optical system of the zoom lens have disposed in order from the object side a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, an aperture stop FA, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, a tenth lens E10, an eleventh lens E11, and various filters MF. The image is formed behind the various filters MF.
The first lens E1 is a negative meniscus lens convex toward the object side, and has an aspherical surface on the image side. The second lens E2 is a negative lens, and both surfaces thereof are concave surfaces. The third lens E3 is a positive lens, and both surfaces thereof are convex surfaces. The fourth lens E4 is a negative lens, and both surfaces thereof are concave surfaces. The two pieces of the third lens E3 and the fourth lens E4 are adhered integrally to form a cemented lens C0, and the first lens group G1 composed of the first lens E1 to the fourth lens E4 has a negative refracting power as a whole.
[0074]
The fifth lens E5 is a positive meniscus lens convex toward the object side, and has an aspherical surface on the object side. The sixth lens E6 is a positive meniscus lens convex toward the object side. The seventh lens E7 is a negative meniscus lens convex toward the object side. The eighth lens E8 is a positive meniscus lens convex toward the object side. The sixth lens E6 to the eighth lens E8 are integrally adhered to form a first cemented lens C1. The ninth lens E9 is a negative meniscus lens convex toward the object side. The tenth lens E10 is a positive lens having an aspherical surface on the image side, and both surfaces thereof are convex surfaces. The ninth lens E9 and the tenth lens E10 are integrally adhered to form a second cemented lens C2. The second lens group G2 composed of the fifth lens E5 to the tenth lens E10 has a positive refractive power as a whole.
The eleventh lens E11 is a positive lens having an aspherical surface on the image side, and both surfaces thereof are convex surfaces. The eleventh lens E11 constitutes the third lens group G3 alone, and naturally has a positive refractive power.
[0075]
When magnification is changed between a short focal end (wide-angle end) and a long focal end (telephoto end), the variable interval between the lens groups changes, that is, the interval DA between the surface of the first lens group G1 closest to the image side, that is, the surface of the fourth lens E4 on the image side (surface number 7) and the surface of the aperture stop FA placed on the object side of the second lens group G2 moving together with the second lens group G2 (surface number 8), the surface of the second lens group G2 closest to the image side, that is, the surface of the tenth lens E10 on the image side (surface number 17) and the surface of the third lens group G3 closest to the object side, that is, the interval DB between the surface of the eleventh lens on the object side (surface 18), the surface of the third lens group G3 closest to the image side, that is, the surface of the eleventh lens E11 on the image side (surface 19) and the surface of the object side of the various filters MF (surface 20). And, as the magnification varies from the wide-angle end to the telephoto end, the first lens group G1, the second lens group G2, and the third lens group G3 move in such a manner that the interval DA between the first lens group G1 and the aperture stop FA (moving integrally with the second lens group G2) gradually decreases, the interval DB between the second lens group G2 and the third lens group G3 gradually increases, and the interval DC between the third lens group G3 and the different-type filter MF temporarily increases and then decreases. In the movement varying with magnification from the wide-angle end to the telephoto end, the second lens group G2 is moved almost monotonously to the object side, the first lens group G1 is temporarily moved to the image side, and then moved to the object side, and the third lens group G3 is temporarily moved to the object side, and then moved to the image side.
In embodiment 2, the focal length F, F-number F, and half angle of view ω of the entire system are changed during zooming in the following ranges: f =5.206-14.991, f =2.59-4.54, ω =43.25-17.54. The optical properties of the optical element are given in the table below.
[0076]
[ Table 5]
Optical characteristics
| Number of surfaces | R | D | N d | v d | Marking | Name of type of glass | |
| 01 | 24.836 | 1.60 | 1.73310 | 48.89 | E1 | OHARA L-LAM72 | |
| 02* | 9.152 | 3.92 | |||||
| 03 | -291.648 | 0.90 | 1.77250 | 49.60 | E2 | OHARA S-LAH66 | |
| 04 | 11.095 | 3.78 | |||||
| 05 | 19.286 | 3.48 | 1.80100 | 34.97 | E3 | OHARA S-LAM66 | |
| 06 | -35.278 | 0.80 | 1.75700 | 47.82 | E4 | OHARA S-LAM54 | |
| 07 | 200.518 | (DA) Variable | |||||
| 08 | Aperture diaphragm | 1.00 | |||||
| 09* | 8.011 | 1.66 | 1.79952 | 42.22 | E5 | OHARA S- |
|
| 10 | 28.538 | 0.59 | |||||
| 11 | 8.349 | 1.38 | 1.77250 | 49.60 | E6 | OHARA S- |
|
| 12 | 56.832 | 0.54 | 1.80100 | 34.97 | E7 | OHARA S- |
|
| 13 | 4.000 | 2.03 | 1.48749 | 70.24 | E8 | OHARA S- |
|
| 14 | 5.976 | 0.44 | |||||
| 15 | 12.402 | 0.50 | 1.68893 | 31.07 | E9 | OHARA S- |
|
| 16 | 6.376 | 1.85 | 1.43875 | 94.94 | E10 | OHARA S- |
|
| 17* | -48.301 | (DB) Variable | |||||
| 18 | 12.225 | 2.77 | 1.43875 | 94.94 | E11 | OHARA S- |
|
| 19* | -120.579 | (DC) Variable | |||||
| 20 | ∞ | 1.24 | 1.51680 | 64.20 | |
||
| 21 | ∞ | ||||||
[0077]
In table 5, the numbers of the second surface, the ninth surface, the seventeenth surface and the nineteenth surface marked with asterisks are aspheric surfaces, and the parameters of the aspheric surfaces in formula (1) are as follows.
Aspheric surface: second side
K＝0.0
A 4 ＝-1.39387×10 -4
A 6 ＝-7.80179×10 -7
A 8 ＝-6.87645×10 -9
A 10 ＝-1.52963×10 -10
A 12 ＝-3.38847×10 -12
A 14 ＝2.20046×10 -14
A 16 ＝8.85391×10 -16
A 18 ＝-1.29685×10 -17
[0078]
Aspheric surface: ninth surface
K＝0.0
A 4 ＝-1.06101×10 -4
A 6 ＝2.72443×10 -7
A 8 ＝-1.08617×10 -7
A 10 ＝2.33258×10 -9
Aspheric surface: seventeenth aspect of the invention
K＝0.0
A 4 ＝1.38067×10 -4
A 6 ＝2.21574×10 -5
A 8 ＝-4.54215×10 -6
A 10 ＝2.25263×10 -7
Aspherical surface: nineteenth surface
K＝0.0
A 4 ＝7.83132×10 -5
A 6 ＝-7.56154×10 -6
A 8 ＝1.72007×10 -7
A 10 ＝-1.73437×10 -9
The variable interval DA between the first lens group G1 and the aperture stop FA (second lens group G2), the variable interval DB between the second lens group G2 and the third lens group G3, and the variable interval DC between the third lens group G3 and the various filters MF vary during zooming, as shown in the following table.
[0079]
[ Table 6]
Variable spacing
| Short focus end | Intermediate focal length | Long focal point end | |
| f | 5.21 | 8.84 | 14.99 |
| DA | 20.728 | 7.873 | 1.828 |
| DB | 3.666 | 7.944 | 18.091 |
| DC | 3.876 | 4.489 | 2.828 |
[0080]
The values relating to the conditional expressions described above in example 3 are as follows.
Value of conditional expression
n c1-1 ＝1.77250
n c1-2 ＝1.80100
v c1-1 -v c1-2 ＝14.63
v c1-3 ＝70.24
d c1-2 /d c1-a11 ＝0.137
(R c1-1 -R c1-3 )/(R c1-1 +R c1-3 )＝0.352
(R c1-3 -R c1-4 )/(R c1-3 +R c1-4 )＝-0.198
v c2-2 ＝94.94
Therefore, the aforementioned numerical values relating to the aforementioned conditional expressions in example 3 are within the ranges of the conditional expressions.
Example 4
[0081]
Fig. 4 shows a structure of an optical system of a zoom lens relating to embodiment 4, and in fig. 4, arrows indicate moving loci of each lens group from a short focal end (wide-angle end) to a long focal end (telephoto end) through an intermediate focal length during zooming.
The zoom lens shown in fig. 4 includes a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, a tenth lens E10, an aperture stop FA, and various filters MF. In this case, the first lens E1 to the third lens E3 constitute a first lens group G1, the fourth lens E4 to the ninth lens E9 constitute a second lens group G2, and the tenth lens E10 constitutes the third lens group G3 alone, each lens group being supported by an appropriate common structure. In the zooming operation, each lens group moves together as a whole, and the aperture stop FA and the second lens group G2 move together. Fig. 4 also shows the number of surfaces per optical surface. Here, the reference numerals of fig. 4 are used independently of the other embodiments. In other words, each specific structure is given a separate reference numeral. Thus, the same reference numerals of fig. 1 to 3 do not necessarily represent the same elements in other embodiments.
[0082]
In fig. 4, the optical elements constituting the optical system of the zoom lens are disposed, in order from the object side, a first lens E1, a second lens E2, a third lens E3, an aperture stop FA, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, a tenth lens E10, and various filters MF. An image is formed behind the various filters MF.
The first lens E1 is a negative meniscus lens convex toward the object side, and has an aspherical surface on the image side. The second lens E2 is a negative lens, and both surfaces thereof are concave surfaces. The third lens E3 is a positive meniscus lens convex toward the object side. The first lens group G1 composed of the first lens E1 to the fourth lens E4 has a negative refractive index as a whole.
The fourth lens E4 is a positive meniscus lens convex toward the object side, and has an aspherical surface on the object side. The fifth lens E5 is a positive meniscus lens convex toward the object side, and the sixth lens E6 is a negative meniscus lens convex toward the object side. The seventh lens E7 is a positive meniscus lens convex toward the object side. Three lenses from the fifth lens to the seventh lens are integrally adhered to form a first cemented lens C1.
[0083]
The eighth lens E8 is a negative meniscus lens convex toward the object side. The ninth lens E9 is a positive lens having an aspherical surface on the image side, and both surfaces thereof are convex surfaces. The eighth lens E8 and the ninth lens E9 are integrally adhered to each other to form a second cemented lens C2. The second lens group G2 composed of the fourth lens E4 to the ninth lens E9 has a positive refractive power as a whole.
The tenth lens E10 is a positive lens having an aspherical surface on the image side, and both surfaces thereof are convex surfaces. The tenth lens E10 alone constitutes the third lens group G3, and naturally has a positive refractive power.
[0084]
When magnification is varied between a short focus end (wide-angle end) and a long focus end (telephoto end), the variable interval between the lens groups varies, that is, the interval DA between the surface of the first lens group G1 closest to the image side, that is, the surface of the third lens E3 on the image side (surface number 6) and the surface of the aperture stop FA placed at the object side of the second lens group G2 moving together with the second lens group G2 (surface number 7), the surface of the second lens group G2 closest to the image side, that is, the surface of the ninth lens E9 (surface number 16) and the surface of the third lens group G3 closest to the object side, that is, the interval DB between the surface of the tenth lens on the object side (surface 17), the surface of the third lens group G3 closest to the image side, that is, the surface of the tenth lens E10 on the image side (surface 18) and the surface of the various filters MF on the object side (surface 19). And, as the magnification varies from the wide-angle end to the telephoto end, the first lens group G1, the second lens group G2, and the third lens group G3 move in such a manner that the interval DA between the first lens group G1 and the aperture stop FA (moving integrally with the second lens group G2) gradually decreases, the interval DB between the second lens group G2 and the third lens group G3 gradually increases, and the interval DC between the third lens group G3 and the various types of filters MF temporarily increases and then decreases.
In the movement varying with magnification from the wide-angle end to the telephoto end, the second lens group G2 is moved almost monotonously to the object side, the first lens group G1 is temporarily moved to the image side and then moved to the object side, and the third lens group G3 is temporarily moved to the object side and then moved to the image side.
In embodiment 4, the focal length F, F-number F, and half angle of view ω of the entire system are changed during zooming in the following ranges: f =5.203-14.987, f =2.67-4.65, ω =43.29-17.55. The optical properties of the optical element are given in the table below.
[0085]
[ Table 7]
Optical characteristics
| Number of surfaces | R | D | N d | v d | Marking | Name of glass type |
| 01 | 24.174 | 1.60 | 1.73310 | 48.89 | E1 | OHARA L-LAM72 |
| 02* | 9.083 | 4.04 | ||||
| 03 | -235.224 | 0.90 | 1.74400 | 44.79 | E2 | OHARA S-LAM2 |
| 04 | 12.103 | 4.49 | ||||
| 05 | 22.320 | 2.40 | 1.80518 | 25.42 | E3 | OHARA S-TIH6 |
| 06 | 250.000 | (DA) Variable | ||||
| 07 | Aperture diaphragm | 1.00 | ||||
| 08* | 7.942 | 1.60 | 1.79952 | 42.22 | E4 | OHARA S-LAH52 |
| 09 | 21.855 | 0.12 | ||||
| 10 | 6.936 | 1.40 | 1.80610 | 40.93 | E5 | OHARA S- |
| 11 | 20.381 | 0.50 | 1.85000 | 32.40 | E6 | SUMITA K- |
| 12 | 3.806 | 1.99 | 1.48749 | 70.24 | E7 | OHARA S- |
| 13 | 5.329 | 0.62 | ||||
| 14 | 9.407 | 0.84 | 1.68893 | 31.07 | E8 | OHARA S- |
| 15 | 4.986 | 1.96 | 1.43875 | 94.94 | E9 | OHARA S- |
| 16* | -97.685 | (DB) Variable | ||||
| 17 | 11.518 | 2.75 | 1.43875 | 94.94 | E10 | OHARA S- |
| 18* | -267.775 | (DC) Variable | ||||
| 19 | ∞ | 1.24 | 1.51680 | 64.20 | |
|
| 20 | ∞ | |||||
[0086]
In table 7, the numbers of the second, eighth, sixteenth and eighteenth surfaces marked with asterisks are aspheric surfaces, and the aspheric parameters in formula (1) are as follows.
Aspheric surface: second surface
K＝0.0
A 4 ＝-1.27855×10 -4
A 6 ＝-6.57584×10 -7
A 8 ＝-8.49625×10 -9
A 10 ＝-1.27642×10 -10
A 12 ＝-3.39257×10 -12
A 14 ＝2.28913×10 -14
A 16 ＝9.13355×10 -16
A 18 ＝-1.41491×10 -17
[0087]
Aspherical surface: eighth aspect of the invention
K＝0.0，
A 4 ＝-9.07488×10 -5 ，
A 6 ＝5.83969×10 -7 ，
A 8 ＝-1.21765×10 -7 ，
A 10 ＝3.21079×10 -9
Aspheric surface: sixteenth aspect of the invention
K＝0.0，
A 4 ＝4.63337×10 -5 ，
A 6 ＝1.96988×10 -5 ，
A 8 ＝-6.18745×10 -6 ，
A 10 ＝2.53045×10 -7
Aspheric surface: eighteenth aspect of the invention
K＝0.0，
A 4 ＝1.02119×10 -4 ，
A 6 ＝-8.13158×10 -6 ，
A 8 ＝1.72125×10 -7 ，
A 10 ＝-1.60528×10 -9
A variable interval DA between the first lens group G1 and the aperture stop FA (second lens group G2), a variable interval DB between the second lens group G2 and the third lens group G3, and a variable interval DC between the third lens group G3 and the various filters MF are varied during zooming as shown in the following table.
[0088]
[ Table 8]
Variable spacing
| Short focus end | Intermediate focal length | Long focal point end | |
| f | 5.20 | 8.83 | 15.00 |
| DA | 21.126 | 8.000 | 1.822 |
| DB | 3.668 | 7.597 | 17.361 |
| DC | 3.513 | 4.265 | 2.813 |
[0089]
The values relating to the conditional expressions described above in example 4 are as follows.
Value of conditional expression
n c1-1 ＝1.80610
n c1-2 ＝1.85000
v c1-1 -v c1-2 ＝8.53
v c1-3 ＝70.24
d c1-2 /d c1-a11 ＝0.129
(R c1-1 -R c1-3 )/(R c1-1 +R c1-3 )＝0.291
(R c1-3 -R c1-4 )/(R c1-3 +R c1-4 )＝-0.167
v c2-2 ＝94.94
Therefore, the aforementioned numerical values related to the aforementioned conditional expressions in example 4 are within the ranges of the conditional expressions.
Example 5
[0090]
Fig. 5 shows a structure of an optical system of a zoom lens relating to embodiment 5, and in fig. 5, arrows indicate moving loci of each lens group from a short focal end (wide-angle end) to a long focal end (telephoto end) through an intermediate focal length during zooming.
The zoom lens shown in fig. 5 includes a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, an aperture stop FA, and various filters MF. In this case, the first lens E1 to the third lens E3 constitute a first lens group G1, and the fourth lens E4 to the ninth lens E9 constitute a second lens group G2. The third lens group G3 is not present in embodiment 5. The first lens group G1 and the second lens group G2 are both supported by an appropriate common structure. In the zooming operation, each lens group moves together as a whole, and the aperture stop FA and the second lens group G2 move together. Fig. 5 also shows the number of surfaces per optical surface. Here, the reference numerals of fig. 5 are used independently of the other embodiments, in other words, independent reference numerals are used for each embodiment. Thus, the same reference numerals in fig. 1 to 4, 5 do not necessarily represent the same elements as in the other embodiments.
[0073]
In fig. 5, the optical elements constituting the optical system of the zoom lens are disposed, in order from the object side, a first lens E1, a second lens E2, a third lens E3, an aperture stop FA, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, and various filters MF. An image is formed behind the various filters MF.
The first lens E1 is a negative meniscus lens convex toward the object side, and has an aspherical surface on the image side. The second lens E2 is a negative meniscus lens facing a convex surface toward the object side. The third lens E3 is a positive meniscus lens convex toward the object side. The first lens group G1 composed of the first lens E1 to the third lens E3 has a negative refractive index as a whole.
[0092]
The fourth lens E4 is a positive meniscus lens convex toward the object side, and has an aspherical surface on the object side. The fifth lens E5 is a biconvex lens. The sixth lens is a double-sided concave lens, and the seventh lens E7 is a positive meniscus lens convex toward the object side. Three lenses of the fifth lens E5 to the seventh lens E7 are integrally adhered to form a first cemented lens C1. The eighth lens is a negative meniscus lens convex toward the object side, and the ninth lens E9 is a positive lens having an aspherical surface on the image side, both surfaces of which are convex surfaces. The two lenses of the eighth lens E8 and the ninth lens E9 are integrally adhered to form a second cemented lens C2. The second lens group G2 composed of the fourth lens E4 to the ninth lens E9 has a positive refracting power as a whole.
Unlike embodiments 1 to 4, embodiment 5 does not use the third lens group G3 composed of a positive lens having an aspherical surface on the image side.
[0093]
When the magnification is varied between the short focal end (wide-angle end) and the long focal end (telephoto end), the variable interval between the lens groups varies, that is, the interval DA between the surface closest to the image side of the first lens group G1, that is, the surface on the image side of the third lens E3 (the number of surfaces 6) and the surface placed on the aperture stop FA moving together with the second lens group G2 at the object side of the second lens group G2 (the number of surfaces 7), and the interval DB between the surface closest to the image side of the second lens group G2, that is, the surface on the image side of the ninth lens E9 (the number of surfaces 16) and the surface on the object side of the various filters MF (the surface 17). Also, the first lens group G1 and the second lens group G2 move in such a manner that the interval DA between the first lens group G1 and the aperture stop FA (moving integrally with the second lens group G2) gradually decreases and the interval DB between the second lens group G2 and the various filters MF gradually increases as the magnification varies from the wide-angle end to the telephoto end. In the movement with varying magnification from the wide-angle end to the telephoto end, the first lens group G1 and the second lens group G2 move along the locus shown in fig. 5.
In example 5, the focal length F, F-number F, and half-angle of view ω of the entire system were varied within the following ranges: f = 5.240-13.102, f =2.90-4.20, ω =43.05-19.72. The optical characteristics of the optical element are given in the table below.
[0094]
[ Table 9]
Optical characteristics
| Number of surfaces | R | D | N d | v d | Marking | Name of glass type |
| 01 | 26.994 | 1.60 | 1.73310 | 48.89 | E1 | OHARA L-LAM72 |
| 02* | 9.233 | 3.01 | ||||
| 03 | 54.196 | 0.90 | 1.77250 | 49.60 | E2 | OHARA S-LAH66 |
| 04 | 8.750 | 3.60 | ||||
| 05 | 16.669 | 2.89 | 1.71736 | 29.52 | E3 | OHARA S-TIH1 |
| 06* | 250.000 | Variable (DA) | ||||
| 07 | Aperture diaphragm | 1.00 | FA | |||
| 08* | 8.038 | 1.57 | 1.79952 | 42.22 | E4 | OHARA S-LAH52 |
| 09 | 35.515 | 0.10 | ||||
| 10 | 10.515 | 1.56 | 1.77250 | 49.60 | E5 | OHARA S-LAH66 |
| 11 | -13.804 | 0.96 | 1.83400 | 37.16 | E6 | OHARA S- |
| 12 | 4.277 | 3.53 | 1.49700 | 81.54 | E7 | OHARA S- |
| 13 | 8.000 | 0.25 | ||||
| 14 | 7.230 | 0.50 | 1.73400 | 51.47 | E8 | OHARA S- |
| 15 | 4.239 | 3.40 | 1.43875 | 94.94 | E9 | OHARA S- |
| 16* | -19.927 | Variable (DB) | ||||
| 17 | ∞ | 1.24 | 1.51680 | 64.20 | |
|
| 18 | ∞ | |||||
[0095]
In table 9, the numbers of the surfaces marked with an asterisk on the optical surfaces of the second surface, the sixth surface, the eighth surface, and the sixteenth surface are aspheric surfaces, and the parameters of the aspheric surfaces in formula (1) are as follows.
Aspheric surface: second surface
K＝0.0，
A 4 ＝-1.05887×10 -4 ，
A 6 ＝-2.34930×10 -6 ，
A 8 ＝8.58632×10 -9 ，
A 10 ＝-8.29139×10 -11 ，
A 12 ＝-4.17598×10 -12 ，
A 14 ＝1.45126×10 -14 ，
A 16 ＝9.40862×10 -16 ，
A 18 ＝-1.23380×10 -17
Aspheric surface: sixth surface
K＝0.0，
A 4 ＝-2.66404×10 -5 ，
A 6 ＝2.51497×10 -7 ，
A 8 ＝-1.81549×10 -8 ，
A 10 ＝9.02091×10 -11
Aspheric surface: eighth aspect of the invention
K＝0.0，
A 4 ＝-8.70033×10 -5 ，
A 6 ＝4.18211×10 -7 ，
A 8 ＝-1.17839×10 -7 ，
A 10 ＝4.35044×10 -9
Aspheric surface: sixteenth aspect of the invention
K＝0.0，
A 4 ＝2.47518×10 -4 ，
A 6 ＝4.61017×10 -6 ，
A 8 ＝-2.17379×10 -6 ，
A 10 ＝1.54197×10 -8
The variable interval DA between the first lens group G1 and the aperture stop FA (second lens group G2) and the variable interval DB between the second lens group G2 and the various filters MF vary during zooming, as shown in the following table.
[0096]
[ Table 10]
Variable spacing
| Short focus end | Intermediate focal length | Long focal point end | |
| f | 5.24 | 8.13 | 13.10 |
| DA | 22.434 | 10.222 | 1.816 |
| DB | 6.760 | 9.309 | 13.696 |
[0097]
Example 5 relates to the values of the conditional expressions described above as follows.
Value of the conditional expression
n c1-1 ＝1.79952
n c1-2 ＝1.77250
v c1-1 -v c1-2 ＝12.44
v c1-3 ＝81.54
d c1-2 /d c1-a11 ＝0.159
(R c1-1 -R c1-3 )/(R c1-1 +R c1-3 )＝0.422
(R c1-3 -R c1-4 )/(R c1-3 +R c1-4 )＝-0.303
v c2-2 ＝94.94
Thus, example 5 relates that the foregoing values of the foregoing conditional expressions are within the ranges of the conditional expressions.
[0098]
Fig. 6 to 8 show aberration curves of chromatic aberration, astigmatism, distortion, and coma of the zoom lens of embodiment 1 shown in fig. 1, in which fig. 6 shows an aberration curve at the wide-angle end, fig. 7 shows an aberration curve at the intermediate focal length, and fig. 8 shows an aberration curve at the telephoto end. In each aberration curve, the dotted line in the spherical aberration curve represents a sinusoidal case; the solid lines in the astigmatism curves represent the radial, the dashed lines the meridian, the bold lines the d-lines and the thin lines the g-lines.
Fig. 9 to 11 show aberration curves of spherical aberration, astigmatism, distortion and coma aberration of the zoom lens of embodiment 2 shown in fig. 2, in which fig. 9 shows the aberration curve at the wide-angle end, fig. 10 shows the aberration curve at the intermediate focal length, and fig. 11 shows the aberration curve at the telephoto end. In each aberration curve, the broken line in the spherical aberration curve represents a sinusoidal case; the solid lines in the astigmatism curves represent the radial, the dashed lines the meridian, the bold lines the d-lines and the thin lines the g-lines.
[0099]
Fig. 12 to 14 show aberration curves of spherical aberration, astigmatism, distortion and coma of the zoom lens of embodiment 3 shown in fig. 3, in which fig. 12 shows the aberration curve at the wide-angle end, fig. 13 shows the aberration curve at the intermediate focal length, and fig. 14 shows the aberration curve at the telephoto end. In each aberration curve, the broken line in the spherical aberration curve represents a sinusoidal case; the solid lines in the astigmatism curves represent the radial, the dashed lines the meridian, the bold lines the d-lines and the thin lines the g-lines.
Fig. 15 to 17 show aberration curves of spherical aberration, astigmatism, distortion and coma aberration of the zoom lens of embodiment 4 shown in fig. 4, in which fig. 15 shows the aberration curve at the wide-angle end, fig. 16 shows the aberration curve at the intermediate focal length, and fig. 17 shows the aberration curve at the telephoto end. In each aberration curve, the broken line in the spherical aberration curve represents a sinusoidal case; the solid lines in the astigmatism curves represent the radial, the dashed lines the meridian, the bold lines the d-lines and the thin lines the g-lines.
[0100]
Fig. 18 to 20 show aberration curves of spherical aberration, astigmatism, distortion and coma of the zoom lens of embodiment 5 shown in fig. 5, in which fig. 18 shows the aberration curve at the wide-angle end, fig. 19 shows the aberration curve at the intermediate focal length, and fig. 20 shows the aberration curve at the telephoto end. In each aberration curve, the dashed line in the spherical aberration curve represents the sinusoidal case; the solid lines in the astigmatism curves represent the radial, the dashed lines the meridian, the bold lines the d-lines and the thin lines the g-lines.
The aberration curves shown in fig. 6 to 20 demonstrate that aberrations are well corrected and suppressed in the zoom lenses having the structures of embodiments 1 to 5 of the present invention shown in fig. 1 to 5.
[0101]
Model of embodiment
A model relating to an embodiment of the present invention in which a photographing apparatus constitutes a photographing optical system using the zoom lenses of the foregoing embodiments 1 to 5 will be described with reference to fig. 21 to 23. Fig. 21 is a perspective view showing an appearance of the apparatus for photographing from the object side, in which fig. 21A is a view showing a state in which a photographing lens is retracted inside a main body of the apparatus, and fig. 21B is a view showing a state in which the photographing lens is extended out of the main body of the apparatus. Fig. 22 is a perspective view showing an appearance of the photographing apparatus as a photographer viewed from the back. Fig. 23 is a block diagram illustrating a functional structure of the photographing apparatus. The description herein relates to PDAs such as photographing apparatuses and portable phones, however, in recent years, the functions of cellular phones have been incorporated into PDAs (personal digital assistants). Such a personal digital assistant includes substantially the same functions and structures as those of a photographing apparatus, and although slightly different in appearance, it is suggested that the zoom lens relating to the present invention be used in such a personal digital assistant.
As shown in fig. 21a,21b, and fig. 22, the photographing apparatus includes a photographing lens 101, a shutter button 102, a zoom lever 103, a viewfinder 104, an electronic flash 105, a liquid crystal monitor 106, an operation button 107, a power switch 108, a memory card slot 109, a communication card slot 110, and the like.
[0102]
As shown in fig. 23, the photographing apparatus further includes a light receiving element 201, a signal processor 202, an image processor 203, a central processing unit 204, a semiconductor memory 205, a communication card 206, and the like.
The photographing apparatus uses the photographing lens 101 and the light receiving element 201 as an area sensor such as a CCD (charge coupled device) imaging device, and the light receiving element 201 of the photographing apparatus reads an image of a subject to be photographed, that is, a subject formed by the photographing lens 101 by an imaging optical system. The zoom lens as described in embodiments 1 to 5 according to the present invention is used as the photographing lens 101.
The signal processor 202 controlled by the central processing unit 204 processes the output of the light receiving element 201, and the processing result is converted into digital image information. The image information digitized by the signal processor 202 is subjected to predetermined image processing in the image processor 203, which is also controlled by the central processing unit 204; thereafter, the processing result is recorded in the semiconductor memory 205 such as a nonvolatile memory. In this case, the semiconductor memory 205 is a memory card inserted in the memory card slot 109 or a semiconductor memory mounted inside the photographing apparatus. The liquid crystal monitor can display an image being photographed and an image that has been recorded in the semiconductor memory card 205. The image recorded on the semiconductor memory card 205 can be output through a communication card inserted in the communication card slot 110.
[0103]
As shown in fig. 21A, when the user carries the photographing apparatus, the photographing lens 101 is in a retracted state inside the photographing apparatus; as shown in fig. 21B, the user turns on the photographing device by operating the power switch 108, and the photographing device cone is pulled out and extended out of the photographing device. At this time, the optical system of each lens group constituting the zoom lens assumes a structure at the wide-angle end, for example, within the photographing apparatus cone of the photographing lens 101. By operating the zoom lever 103, the structure of the optical system of each lens group is changed, and the user can change the magnification for the telephoto end. Here, the viewfinder 104 may be used to change magnification, internally locking the image angle change of the photographing lens 101.
In most cases, half-pressing the shutter button 102 can perform focusing. According to an embodiment of the present invention, or the zoom lens described in embodiment 1 to embodiment 5, focusing is achieved by movement of the first lens group G1 and movement of the light receiving element; the zoom lenses of embodiments 1 to 4, focus is achieved by movement of the third lens group. The shooting can be carried out by fully pressing the shutter button; after the shutter is pressed, the above-mentioned processing will be performed.
[0104]
The user operates the button 107 by a predetermined operation to display the image recorded in the semiconductor memory 205 on the liquid crystal monitor 106 or output the image through the communication card 206. When using devices such as the semiconductor memory 205 and the communication card 206, the user inserts them into dedicated or general-purpose slots such as the memory card slot 109 and the communication card slot 110.
When the photographing lens is inside the photographing apparatus in a collapsed state, it is not necessary that all lens groups in the zoom lens are disposed on the optical axis. If at least one of the second lens group G2 and the third lens group G3 is withdrawn from the optical axis and stored in parallel with the other lens groups when the photographing lens 101 is in the collapsed state, the volume of the photographing apparatus can be further reduced by adopting the above-described mechanism.
The photographing lens equipped with the zoom lens described in embodiments 1 to 5 can be applied to the aforementioned photographing apparatus or personal digital assistant as a photographing optical system. So that a high image quality, small-sized photographing apparatus or personal digital assistant can be realized by using light receiving elements of eight million pixels to ten million pixels.
[0019]
According to one embodiment of the present invention, a zoom lens has a configuration in which a first lens group having a negative refractive power and a second lens group having a positive refractive power are arranged in order from an object side, and at least the first lens group and the second lens group move in such a manner that an interval between the first lens group and the second lens group decreases and an interval between the second lens group and an image plane increases as a magnification is changed from a wide-angle end to a telephoto end. The present invention can thus provide a zoom lens capable of effectively controlling various kinds of aberrations with substantially no change in cost, which can achieve a sufficiently large wide angle of view at the wide angle end, and can achieve a smaller size and higher resolution. The present invention can also provide a photographing apparatus and a personal digital assistant using such a zoom lens.
Specifically, the zoom lens includes: a first lens group having a negative refractive power, a second lens group having a positive refractive power, and an aperture stop which is located on the object side of the second lens group and moves together with the second lens group are placed in order from the object side, wherein at least the first lens group and the second lens group move in such a manner that an interval between the first lens group and the second lens group decreases and an interval between the second lens group and an image plane increases as a magnification is changed from a wide-angle end to a telephoto end. The second lens group comprises a first joint lens formed by at least three lenses in a joint mode. Thus, the zoom lens can realize a sufficiently large half-width angle of view of 42 degrees or more at the wide-angle end, can realize excellent chromatic aberration correction, particularly, chromatic aberration of magnification and coma, and can achieve a resolution corresponding to an imaging device having eight million to ten million pixels or more while realizing miniaturization.
[0020]
According to one embodiment of the present invention, a zoom lens has a configuration in which a first lens group having a negative refracting power, a second lens group having a positive refracting power and a third lens group having a positive refracting power, and an aperture stop located on an object side of the second lens group and moving together with the second lens group are arranged in order from the object side, wherein, as a magnification is changed from a wide-angle end to a telephoto end, at least the first lens group and the second lens group move in such a manner that an interval between the first lens group and the second lens group decreases and an interval between the second lens group and the third lens group increases. The second lens group comprises a first joint lens formed by at least three lenses in a joint mode and a second joint lens formed by at least two lenses in a joint mode. With this structure, the zoom lens can realize a sufficiently large half-width angle of view of 42 degrees or more at the wide-angle end, can have excellent chromatic aberration correction, particularly chromatic aberration of magnification and coma, can acquire the eye height and simplify the focusing mechanism, and can achieve a resolution corresponding to an imaging apparatus having eight to ten million pixels or more while realizing miniaturization.
[0021]
According to one embodiment of the present invention, the zoom lens has a structure in which the second cemented lens is disposed on the image side of the first cemented lens, a surface closest to the object side and a surface closest to the image side in the first cemented lens are both convex toward the object side, and the second cemented lens has a positive refractive index as a whole. So that the zoom lens can correct monochromatic aberrations such as spherical aberration and astigmatism well for better performance.
According to one embodiment of the present invention, a zoom lens has a structure in which a second cemented lens is disposed on an image side of a first cemented lens including a positive lens, a negative lens, and a positive lens that are disposed in order from an object side and are cemented to each other; the second cemented lens has a positive refractive index as a whole. So that a zoom lens having a wider angle of view and maintaining high performance can be easily obtained.
[0022]
According to an embodiment of the present invention, the zoom lens satisfies the conditional expression: 1.65 < n c1-1 ＜1.90，1.65＜n c1-2 ＜1.90， 4＜v c1-1 -v c1-2 < 25, and 68 < v c1-3 < 98, wherein n c1-1 Refractive index of positive lens at object side of first cemented lens, n c1-2 Is the refractive index of the negative lens in the first cemented lens, v c1-1 Abbe number, v, of positive lens at object side of first cemented lens c1-2 Is Abbe number, v, of the negative lens in the first cemented lens c1-3 Is a first cemented lensAbbe number of the positive lens on the image side. So that the zoom lens can correct chromatic aberration well to achieve better performance.
[0023]
According to an embodiment of the present invention, the zoom lens satisfies the conditional expression: d is more than 0.10 c1-2 /d c1-a11 < 0.19, wherein d c1-2 Is the center thickness (thickness measured along the optical axis of the lens) of the negative lens in the first cemented lens, d c1-a11 Is the center thickness of all of the first cemented lenses. Therefore, the manufacturing difficulty of the cemented lens is reduced, and it is easier to manufacture a smaller-sized zoom lens.
According to an embodiment of the present invention, the zoom lens satisfies the conditional expression: 0.2 < (R) c1-1 -R c1-3 )/(R c1-1 +R c1-3 ) < 0.5, and-0.4 < (R) c1-3 -R c1-4 )/(R c1-3 +R c1-4 ) < -0.1, wherein R c1-1 Is the radius of curvature, R, of the surface of the first cemented lens closest to the object side c1-3 Is a curvature radius R of a joint surface on the image side of two joint surfaces of the first joint lens c1-4 Is the radius of curvature of the surface closest to the image side in the first cemented lens. So that the zoom lens can correct monochromatic aberration and chromatic aberration well to achieve better performance.
[0024]
According to one embodiment of the present invention, a zoom lens has a structure in which a second cemented lens including a negative lens and a positive lens that are placed in order from an object side and cemented to each other is placed on an image side of a first cemented lens, the zoom lens satisfying a conditional expression: 68 < v c2-2 < 98, wherein v c2-2 Is the abbe number of the positive lens in the second cemented lens. So that the zoom lens can correct chromatic aberration of magnification well for better performance.
According to an embodiment of the present invention, the zoom lens has a structure in which the second cemented lens is disposed on the image side of the first cemented lens, and at least one positive lens is disposed on the object side of the first cemented lens. So that the zoom lens can correct various aberrations well for better performance.
[0025]
According to an embodiment of the present invention, the zoom lens has a structure in which at least one positive lens placed on the object side of the first cemented lens has at least one aspherical surface. So that the zoom lens can correct spherical aberration and coma well to achieve better performance.
According to an embodiment of the present invention, the zoom lens has a structure in which the first cemented lens has only a spherical surface, and the second lens group has at least one aspherical surface. Thus, the zoom lens can suppress the influence of the deviation of the three lenses engaged in the manufacturing process from the optical axis, can obtain more stable performance, and can well correct spherical aberration and coma to achieve better performance.
According to one embodiment of the present invention, a photographing apparatus includes a zoom lens as a photographing optical system; by using a zoom lens that can obtain a sufficiently wide half angle of view of 42 degrees or more at the wide-angle end, chromatic aberration, particularly chromatic aberration of magnification and coma, is corrected well, it is possible to make a photographing apparatus smaller in size and have higher resolution to make the photographing apparatus achieve better image quality, and to achieve resolution corresponding to an imaging device having pixels of eight million to ten million or more in a small-sized condition.
[0026]
According to an embodiment of the present invention, a personal digital assistant includes a zoom lens of a photographing optical system as a photographing function section; by using a zoom lens that can obtain a wide enough half angle of view of 42 degrees wide-angle end or more, chromatic aberration, particularly chromatic aberration of magnification and coma, is corrected well, and resolution corresponding to an imaging device having pixels of eight million to ten million or more is achieved under a small size condition, it is possible to make a personal digital assistant smaller in size at a low cost, and to have higher resolution to make a photographing apparatus achieve better image quality.
Although the present invention is illustrated by the example embodiments, the present invention is not limited thereto. Various modifications may be made thereto without departing from the appended claims. Further, the number, position, shape of the elements are not limited to the above-described embodiments, and may be modified to be applied to various cases of the present invention. Furthermore, any element or component disclosed in the present application should be protected whether or not it is included in the following claims.
Claims (13)
1. A zoom lens, comprising:
a first lens group having a negative refracting power;
a second lens group having a positive refracting power, the first lens group and the second lens group being disposed in order from an object side; and
an aperture stop disposed on an object side of the second lens group, moving together with the second lens group;
wherein at least the first lens group and the second lens group move in such a manner that an interval between the first lens group and the second lens group decreases and an interval between the second lens group and an image surface increases as a magnification is changed from a wide-angle end to a telephoto end, and
the second lens group includes:
a first cemented lens composed of at least three lens cemented; and
a second cemented lens consisting of at least two lens cemented.
2. A zoom lens, comprising:
a first lens group having a negative refracting power;
a second lens group having a positive refracting power;
a third lens group having a positive refracting power, the first lens group, the second lens group, and the third lens group being disposed in order from an object side; and
an aperture stop disposed on an object side of the second lens group, moving together with the second lens group;
wherein at least the first lens group and the second lens group move in such a manner that an interval between the first lens group and the second lens group decreases and an interval between the second lens group and the third lens group increases as a magnification is changed from a wide-angle end to a telephoto end, and
the second lens group includes:
a first cemented lens composed of at least three lens cemented; and
a second cemented lens consisting of at least two lens cemented.
3. The zoom lens according to claim 1 or 2, wherein the second cemented lens is disposed on an image side of the first cemented lens, a surface of the first cemented lens closest to the object side and a surface convex to the object side closest to the image side, the second cemented lens having a positive refractive index as a whole.
4. The zoom lens according to claim 1 or 2, wherein the second cemented lens having three positive lenses, a negative lens, and a positive lens that are placed in order from an object side and cemented with each other is placed on an image side of the first cemented lens, the second cemented lens having a positive refractive index as a whole.
5. The zoom lens according to claim 4, wherein the following conditional expression is satisfied:
1.65＜n c1-1 ＜1.90，
1.65＜n c1-2 ＜1.90，
4＜v c1-1 -v c1-2 ＜25，
68＜v c1-3 ＜98，
wherein n is c1-1 Is a refractive index of a positive lens on the object side of the first cemented lens, n c1-2 Is the refractive index, v, of the negative lens of the first cemented lens c1-1 Is the Abbe number, v, of a positive lens on the object side of the first cemented lens c1-2 Is the Abbe number, v, of the negative lens of the first cemented lens c1-3 Is an abbe number of a positive lens on the image side of the first cemented lens.
6. The zoom lens according to claim 4, wherein the following conditional expression is satisfied:
0.10＜d c1-2 /d c1-a11 ＜0.19，
wherein d is c1-2 Is the central thickness of the negative lens of said first cemented lens, measured along the optical axis of the lens, d c1-a11 Is the center thickness of all of the first cemented lenses.
7. The zoom lens according to claim 4, wherein the following conditional expression is satisfied:
0.2＜(R c1-1 -R c1-3 )/(R c1-1 +R c1-3 ) < 0.5, and
-0.4＜(R c1-3 -R c1-4 )/(R c1-3 +R c1-4 )＜-0.1，
wherein R is c1-1 Is a radius of curvature, R, of a surface of the first cemented lens closest to the object side c1-3 Is a radius of curvature, R, of a joint surface on the image side of the two joint surfaces of the first joint lens c1-4 Is a radius of curvature of a surface of the first cemented lens closest to the image side.
8. The zoom lens according to claim 1 or 2, wherein the second cemented lens having a negative lens and a positive lens which are placed in order from an object side and cemented with each other is placed on an image side of the first cemented lens, and the zoom lens satisfies the following conditional expression:
68＜v c2-2 ＜98，
wherein v is c2-2 Is the abbe number of the positive lens in the second cemented lens.
9. The zoom lens of claim 1 or 2, wherein the second cemented lens is disposed on an image side of the first cemented lens, and at least one positive lens is disposed on an object side of the first cemented lens.
10. The zoom lens of claim 9, wherein at least one positive lens disposed on the first cemented lens object side has at least one aspherical surface.
11. A zoom lens according to claim 1 or 2, wherein the first cemented lens is provided with only a spherical surface, and the second lens group has at least one aspherical surface.
12. A photographing apparatus including the zoom lens according to claim 1 or 2 as a photographing optical system.
13. A personal digital assistant comprising the zoom lens according to claim 1 or 2 as a photographing optical system of a photographing function section.
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| CN101566724A (en) * | 2008-04-22 | 2009-10-28 | 株式会社尼康 | Lens system and optical apparatus having this lens system |
| CN101526667B (en) * | 2008-03-03 | 2012-09-19 | 株式会社尼康 | Zoom lens and optical apparatus equipped with this zoom lens |
| CN103430075A (en) * | 2011-03-11 | 2013-12-04 | 富士胶片株式会社 | Variable magnification optical assembly and image capture device |
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- 2007-06-29 CN CNB2007101290317A patent/CN100520481C/en not_active Expired - Fee Related
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101526667B (en) * | 2008-03-03 | 2012-09-19 | 株式会社尼康 | Zoom lens and optical apparatus equipped with this zoom lens |
| CN101566724A (en) * | 2008-04-22 | 2009-10-28 | 株式会社尼康 | Lens system and optical apparatus having this lens system |
| CN101566724B (en) * | 2008-04-22 | 2012-11-28 | 株式会社尼康 | Lens system and optical apparatus having this lens system |
| CN103430075A (en) * | 2011-03-11 | 2013-12-04 | 富士胶片株式会社 | Variable magnification optical assembly and image capture device |
| CN103430075B (en) * | 2011-03-11 | 2016-01-20 | 富士胶片株式会社 | Variable magnification optical system and imaging device |
| CN104076490A (en) * | 2014-06-28 | 2014-10-01 | 青岛歌尔声学科技有限公司 | Wide-angle distortion-removing dual-band confocal optical lens |
| CN104076490B (en) * | 2014-06-28 | 2017-04-26 | 青岛歌尔声学科技有限公司 | Wide-angle distortion-removing dual-band confocal optical lens |
| CN105974567A (en) * | 2015-03-13 | 2016-09-28 | 佳能株式会社 | Zoom lens and image pickup apparatus having same |
| US10120171B2 (en) | 2015-03-13 | 2018-11-06 | Canon Kabushiki Kaisha | Zoom lens and image pickup apparatus having the same |
| CN112334813A (en) * | 2019-06-18 | 2021-02-05 | 深圳市大疆创新科技有限公司 | Lens system, imaging device, and moving object |
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