Lens device and imaging device having the same

Abstract

To provide a wide field angle and compact zoom lens, etc., which can obtain high optical performance though it is robust against manufacturing errors.SOLUTION: A lens device has, in order from an object side, a positive first lens group L1, a negative second lens group L2, a positive third lens group L3, a zoom lens composed of a rear group, and an actuator for moving a focus group included in the zoom lens. When zooming from a wide angle end to a telephone end, the first lens group moves, an interval between the first and second lens groups expands, and an interval between the second and third lens groups narrows. When the third lens group or a lens group continuous to an image side with respect to the third lens group is a positive lens group, and these lens groups are defined as a positive group GP, the positive group includes a negative first cemented lens A and a positive second cemented lens B, the first cemented lens A being composed of a positive lens AP and a negative lens AN, both concave shaped. The positive group and the first cemented lens satisfy a prescribed conditional expression.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a lens device, and is suitable for digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and the like.

Background Art

[0002] Conventionally, in zoom lenses used in photographic cameras, video cameras, etc., an inner focus method or a rear focus method has been proposed, in which a lens group behind (image side) the first lens group on the object side is moved for focusing.

[0003] Furthermore, in digital cameras and video cameras, the number of pixels of solid-state imaging devices such as CCDs and CMOS sensors has been increasing. Also, in photographic lenses, high optical performance including chromatic aberration is required, and miniaturization is progressing.

[0004] Patent Document 1 discloses a zoom lens having a five-group configuration including lens groups with positive, negative, positive, negative, and positive refractive powers in order from the object side. In Patent Document 1, the number of lenses is reduced by adopting an aspherical lens in the fourth lens group.

[0005] Patent Document 2 discloses a zoom lens having a five-group configuration including lens groups with positive, negative, positive, negative, and negative refractive powers in order from the object side. In Patent Document 2, a high zoom ratio is achieved by optimizing the refractive power of each group.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In recent years, there has been a strong demand for lens systems used in imaging devices that are compact overall while possessing high optical performance. To achieve good optical performance while miniaturizing the entire lens system, it is important to appropriately set the refractive power and configuration of each lens group, as well as the movement conditions of each lens group during zooming. In particular, when miniaturizing the lens system in cameras with large image sensors, high refractive index glass materials are often used extensively, and it is necessary to suppress chromatic aberration while ensuring robustness against lens polarization.

[0008] As shown in Patent Document 1, it is possible to shorten the overall lens length by using many aspherical lenses and increasing the refractive power of each lens, but it is difficult to suppress axial chromatic aberration across the entire zoom range.

[0009] As described in Patent Document 2, when a high zoom ratio is achieved while also securing a telephoto focal length, it becomes difficult to suppress various aberrations at the wide-angle end, particularly chromatic aberration, making it difficult to achieve a wider field of view.

[0010] The present invention aims to provide a wide-angle, compact zoom lens or the like that is robust against manufacturing errors while achieving high optical performance. [Means for solving the problem]

[0011] One aspect of the present invention is a lens device arranged in order from the object side to the image side, consisting of a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power. 2A lens device comprising a rear group including the above lens group, a zoom lens in which the spacing between adjacent lens groups changes during zooming, and an actuator for moving a focus group included in the zoom lens that moves during focusing, wherein when zooming from the wide-angle end to the telephoto end, the first lens group moves, the spacing between the first lens group and the second lens group widens, and the spacing between the second lens group and the third lens group narrows, and when the third lens group, or the lens group arranged continuously on the image side with respect to the third lens group, is a lens group with positive refractive power, then when the lens group composed of the third lens group and the lens group with positive refractive power is considered the positive group, the positive group is ,negative The refractive power of the first cemented lens And, positioned adjacent to the image side of the first cemented lens The first cemented lens includes a second cemented lens with positive refractive power, the first cemented lens consisting of a biconvex first lens with positive refractive power and a second lens with negative refractive power, arranged sequentially from the object side to the image side, the focal length at the wide-angle end of the positive group is fGP, the focal length of the second lens as a single lens is fAN, the radius of curvature of the first lens on the object side is APR1, and the radius of curvature of the first lens on the image side is APR2 νdAP is the Abbe number of the first lens in the first cemented lens, and νdAN is the Abbe number of the second lens in the first cemented lens. In that case, -1.200 <fAN / fGP<-0.795 0.001<|APR2 / APR1| ≦1.060 0.60 < νdAN / νdAP < 0.85 It is characterized by satisfying the following conditional expression.

[0013] Other objects and features of the present invention are described in the following embodiments. [Effects of the Invention]

[0014] According to the present invention, it is possible to realize a wide-angle, compact zoom lens and the like that is robust against manufacturing errors while also providing high optical performance. [Brief explanation of the drawing]

[0015] [Figure 1] These are cross-sectional views of the zoom lens of Example 1 at its wide-angle end, intermediate zoom position, and telephoto end. [Figure 2] It is an aberration diagram at the wide-angle end (A), intermediate zoom position (B), and telephoto end (C) of the zoom lens of Example 1. [Figure 3] It is a lens cross-sectional view at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 2. [Figure 4] It is an aberration diagram at the wide-angle end (A), intermediate zoom position (B), and telephoto end (C) of the zoom lens of Example 2. [Figure 5] It is a lens cross-sectional view at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 3. [Figure 6] It is an aberration diagram at the wide-angle end (A), intermediate zoom position (B), and telephoto end (C) of the zoom lens of Example 3. [Figure 7] It is a lens cross-sectional view at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 4. [Figure 8] It is an aberration diagram at the wide-angle end (A), intermediate zoom position (B), and telephoto end (C) of the zoom lens of Example 4. [Figure 9] It is a lens cross-sectional view at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 5. [Figure 10] It is an aberration diagram at the wide-angle end (A), intermediate zoom position (B), and telephoto end (C) of the zoom lens of Example 5. [Figure 11] It is a lens cross-sectional view at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 6. [Figure 12] It is an aberration diagram at the wide-angle end (A), intermediate zoom position (B), and telephoto end (C) of the zoom lens of Example 6. [Figure 13] It is a schematic diagram of an imaging device. [Figure 14] It is a diagram showing the configuration of a camera system including a lens device and a camera body.

Mode for Carrying Out the Invention

[0016] Hereinafter, a zoom lens, a lens device having the same, and an imaging device will be described based on the accompanying drawings.

[0017] Figure 1 is a cross-sectional view of the zoom lens of Example 1 at its wide-angle end (short focal length end), intermediate zoom position, and telephoto end (long focal length end). Figures 2(A), 2(B), and 2(C) are aberration diagrams of the zoom lens of Example 1 at its wide-angle end, intermediate zoom position, and telephoto end, respectively. The aberration diagrams for each example are for when the zoom lens is focused on an object at infinity. The zoom lens of Example 1 is a zoom lens with a zoom ratio of approximately 4.4 and an aperture ratio of approximately 4.1.

[0018] Figure 3 is a cross-sectional view of the zoom lens of Example 2 at the wide-angle end, intermediate zoom position, and telephoto end. Figures 4(A), 4(B), and 4(C) are aberration diagrams of the zoom lens of Example 2 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. The zoom lens of Example 2 is a zoom lens with a zoom ratio of 4.4 and an aperture ratio of approximately 2.9 to 4.1.

[0019] Figure 5 is a cross-sectional view of the zoom lens of Example 3 at the wide-angle end, intermediate zoom position, and telephoto end. Figures 6(A), 6(B), and 6(C) are aberration diagrams of the zoom lens of Example 3 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. The zoom lens of Example 3 is a zoom lens with a zoom ratio of 4.4 and an aperture ratio of approximately 2.9 to 4.1.

[0020] Figure 7 is a cross-sectional view of the zoom lens of Example 4 at the wide-angle end, intermediate zoom position, and telephoto end. Figures 8(A), 8(B), and 8(C) are aberration diagrams of the zoom lens of Example 4 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. The zoom lens of Example 4 is a zoom lens with a zoom ratio of 5.4 and an aperture ratio of approximately 2.9 to 5.8.

[0021] Figure 9 is a cross-sectional view of the zoom lens of Example 5 at the wide-angle end, intermediate zoom position, and telephoto end. Figures 10(A), 10(B), and 10(C) are aberration diagrams of the zoom lens of Example 5 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. The zoom lens of Example 5 is a zoom lens with a zoom ratio of 5.1 and an aperture ratio of approximately 2.9 to 5.8.

[0022] Figure 11 is a cross-sectional view of the zoom lens of Example 6 at the wide-angle end, intermediate zoom position, and telephoto end. Figures 12(A), 12(B), and 12(C) are aberration diagrams of the zoom lens of Example 6 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. The zoom lens of Example 6 is a zoom lens with a zoom ratio of 5.1 and an aperture ratio of approximately 2.9 to 5.8.

[0023] The zoom lenses in each embodiment are imaging optical systems used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, and surveillance cameras. Furthermore, the zoom lenses in each embodiment can also be used as projection optical systems for projection devices (projectors).

[0024] In each cross-sectional view of the lens, the left side is the object side (front) and the right side is the image side (rear). The zoom lens of each embodiment is composed of multiple lens groups. In this specification, a lens group is a collection of lenses that move or remain stationary as a whole during zooming. That is, in the zoom lens of each embodiment, the distance between adjacent lens groups changes when zooming from the wide-angle end to the telephoto end. A lens group may consist of one lens or multiple lenses. Furthermore, a lens group may include an aperture diaphragm.

[0025] In each lens cross-sectional view, if i represents the order of the lens group from the object side, then Li represents the i-th lens group. SP is the aperture diaphragm that determines (limits) the light beam at the open F-number (Fno). IP is the image plane, and when the zoom lens of each embodiment is used as the imaging optical system of a digital still camera or digital video camera, the imaging surface of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor is located there. When the zoom lens of each embodiment is used as the imaging optical system of a silver halide film camera, a photosensitive surface corresponding to the film plane is placed on the image plane IP. The arrows related to focus indicate the direction of movement of the lens group when focusing from infinity to near distance.

[0026] In the spherical aberration diagram, Fno is the F-number and indicates the amount of spherical aberration for the d-line (wavelength 587.56 nm) and the g-line (wavelength 435.835 nm). In the astigmatism diagram, ΔS indicates the amount of astigmatism on the sagittal image plane, and ΔM indicates the amount of astigmatism on the meridional image plane. In the distortion diagram, the amount of distortion for the d-line is shown. In the chromatic aberration diagram, the amount of chromatic aberration for the g-line is shown. ω is the half-angle of view (°) and is the angle of view determined by ray tracing. In each of the following embodiments, the wide-angle end and telephoto end refer to the zoom positions when the lens group for zooming is located at both ends of the range in which it can move along the optical axis due to the mechanism.

[0027] Next, we will describe the characteristic configurations of the zoom lenses in each embodiment.

[0028] The zoom lens in each embodiment consists of a first lens group L1 with positive refractive power (optical power = reciprocal of focal length), a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, and a rear group RG including one or more lens groups, arranged sequentially from the object side to the image side. In other words, the zoom lens consists of four or more lens groups. The spacing between adjacent lens groups changes when zooming. When zooming from the wide-angle end to the telephoto end, the first lens group L1 moves, the spacing between the first lens group L1 and the second lens group L2 widens, and the spacing between the second lens group L2 and the third lens group L3 narrows. If the third lens group L3, or a lens group arranged continuously on the image side relative to the third lens group L3, is a lens group with positive refractive power, the lens group consisting of the third lens group L3 and the lens group with positive refractive power is called lens group GP (positive group). In this case, the lens group GP includes a cemented lens A (first cemented lens) with negative refractive power and a cemented lens B (second cemented lens) with positive refractive power, arranged in order from the object side to the image side. The cemented lens A consists of a biconvex lens AP (first lens) with positive refractive power and a lens AN (second lens) with negative refractive power, arranged in order from the object side to the image side.

[0029] Furthermore, the zoom lens of each embodiment satisfies the following conditions (1) and (2).

[0030] -1.200 <fAN / fGP<-0.795 ···(1) 0.001<|APR2 / APR1|<1.150 ···(2) Here, fGP is the focal length of the lens group GP at its wide-angle end, and fAN is the focal length of the negative lens AN as a single lens. APR1 and APR2 are the object-side and image-side radii of the positive lens AP, respectively.

[0031] Each embodiment of the zoom lens is configured to have first to third lens groups with positive, negative, and positive refractive powers arranged sequentially from the object side to the image side, in order to shorten the overall length of the lens at the wide-angle end while effectively correcting aberrations throughout the entire zoom range. By having a configuration consisting of at least four groups, spherical aberration and coma aberration occurring in the first lens group L1 and the second lens group L2 are effectively corrected. Furthermore, in the telephoto range, variations in spherical aberration and coma aberration due to manufacturing tolerances become larger. For this reason, each embodiment of the zoom lens is a so-called positive-lead type zoom lens in which the first lens group L1 has positive refractive power, and the incident height of on-axial light rays is suppressed for each lens element on the image side from the second lens group L2 onwards, thereby improving miniaturization and robustness.

[0032] Furthermore, in order to achieve miniaturization and ensure a high magnification ratio, the spacing between each lens group is changed so that the distance between the first lens group L1 and the second lens group L2 is wider at the telephoto end compared to the wide-angle end, and the distance between the second lens group L2 and the third lens group L3 is narrower, and zooming is performed accordingly.

[0033] The lens group GP consists of the third lens group L3, or, if the lens group arranged continuously on the image side relative to the third lens group L3 is a lens group with positive refractive power, then the lens group GP consists of the third lens group L3 and the lens group with positive refractive power. Furthermore, the lens group GP includes a cemented lens A with negative refractive power and a cemented lens B with positive refractive power, arranged sequentially from the object side to the image side. The lens group GP that performs zooming has positive refractive power as a whole and has multiple lenses. In order to achieve miniaturization and suppress fluctuations in spherical aberration and coma aberration due to zooming, the spacing of some of the lens groups with positive refractive power may be changed.

[0034] The cemented lens A consists of a biconvex positive lens AP and a negative lens AN, arranged sequentially from the object side to the image side. By incorporating cemented lens A, it becomes easier to suppress wavelength-dependent variations in spherical aberration and coma aberration, which are challenges when increasing aperture size. Furthermore, when the refractive power of the positive lens AP is increased, the radius of curvature decreases. As a result, by incorporating cemented lens A, robustness against manufacturing errors in coma aberration caused by eccentricity is ensured, making it easier to secure good optical performance.

[0035] When the refractive index of the negative lens AN is increased relative to the positive lens AP, the cemented surface exhibits divergence, which is unfavorable for correcting chromatic aberration but makes it easier to correct spherical aberration. Conversely, when the refractive index is increased, the cemented surface exhibits convergence, which is advantageous for correcting chromatic aberration but makes it difficult to correct spherical aberration. Therefore, by placing cemented lens B on the image side of cemented lens A, and using a configuration with two sets of cemented lenses, it is possible to compensate for insufficient correction of various aberrations caused by the selection of glass materials and suppress various aberrations without using many aspherical lenses.

[0036] Conditional equation (1) defines the focal length of the negative lens AN as the focal length of the lens group GP at the wide-angle end, ensuring the magnification sharing of the lens group GP and effectively correcting spherical aberration and coma aberration. If the upper limit of conditional equation (1) is exceeded and the refractive power of the negative lens AN becomes stronger than that of the lens group GP, it becomes difficult to ensure the magnification sharing, leading to an increase in the overall lens length at the telephoto end. If the lower limit of conditional equation (1) is exceeded and the refractive power of the negative lens AN becomes weak, the axially incident light beam to the cemented lens B becomes strongly converged light, making it difficult to suppress coma aberration in the wide-angle range.

[0037] Condition (2) specifies the ratio of the object-side radius of curvature to the image-side radius of curvature of the positive lens AP, optimizing the chromatic aberration correction effect while ensuring the refractive power of the positive lens AP. If the upper limit of condition (2) is exceeded and the object-side radius of curvature of the positive lens AP becomes small, it is advantageous for correcting spherical aberration, but it becomes difficult to suppress the wavelength-dependent variation of coma aberration. If the lower limit of condition (2) is exceeded and the object-side radius of curvature of the positive lens AP becomes large, the radius of curvature of the cemented surface becomes too small, leading to fluctuations in spherical aberration due to zooming.

[0038] Furthermore, it is preferable that the numerical ranges of conditional expressions (1) and (2) be within the ranges of the following conditional expressions (1a) and (2a).

[0039] -1.100 <fAN / fGP<-0.800 ···(1a) 0.100<|APR2 / APR1|<1.100 ···(2a) By satisfying condition (1a), axial chromatic aberration in the wide-angle range is suppressed while coma aberration is easily controlled. By satisfying condition (2a), spherical aberration in the telephoto range is suppressed while the overall length of the lens can be shortened, which is preferable.

[0040] Furthermore, it is even more preferable to set the numerical ranges of conditional expressions (1) and (2) to the ranges of the following conditional expressions (1b) and (2b).

[0041] -1.050 <fAN / fGP<-0.802 ···(1b) 0.150<|APR2 / APR1|<1.095 ···(2b) As described above, by appropriately configuring each lens group and simultaneously satisfying conditions (1) and (2), various aberrations such as chromatic aberration and spherical aberration can be well corrected, and a wide-angle, compact zoom lens can be realized that is robust against manufacturing errors.

[0042] Furthermore, the zoom lens in each embodiment can also adopt the following configuration as an alternative.

[0043] As an alternative, the zoom lens in each embodiment consists of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, and a rear group RG including one or more lens groups, arranged sequentially from the object side to the image side. In other words, the zoom lens consists of four or more lens groups. The spacing between adjacent lens groups changes with zooming. When zooming from the wide-angle end to the telephoto end, the first lens group L1 moves, the spacing between the first lens group L1 and the second lens group L2 widens, and the spacing between the second lens group L2 and the third lens group L3 narrows. If the third lens group L3, or a lens group arranged continuously on the image side relative to the third lens group L3, is a lens group with positive refractive power, the lens group consisting of the third lens group L3 and the lens group with positive refractive power is called lens group GP (positive group). In this case, the lens group GP includes a cemented lens A (first cemented lens) with negative refractive power and a cemented lens B (second cemented lens) with positive refractive power, arranged in order from the object side to the image side. The cemented lens A consists of a biconvex lens AP (first lens) with positive refractive power and a lens AN (second lens) with negative refractive power, arranged in order from the object side to the image side.

[0044] Furthermore, the zoom lens of each embodiment as an alternative means satisfies the following conditions (1) and (3).

[0045] -1.200 <fAN / fGP<-0.795 ···(1) 1.45 <ndAN<1.64 ···(3) Here, fGP is the focal length of the lens group GP at its wide-angle end, and fAN is the focal length of the negative lens AN. ndAN is the refractive index of the negative lens AN (optical element) at the d-line.

[0046] Furthermore, any parts of the above-mentioned zoom lens configuration and conditions that overlap with those previously mentioned will be omitted from the explanation.

[0047] Condition (3) specifies the refractive index of the negative lens AN at the d line. If the refractive index of the negative lens AN is high, spherical aberration is easier to correct, but the cementing surface becomes divergent, which is disadvantageous for correcting chromatic aberration. In particular, in the wide-angle range, optimizing the refractive index of the negative lens AN is important to achieve both chromatic aberration and spherical aberration correction with cemented lens A. If the refractive index is higher than the upper limit of condition (3), the radius of curvature at the cementing surface of cemented lens A becomes too large, making it difficult to achieve both first-order chromatic aberration correction and coma aberration correction. If the refractive index is lower than the lower limit of condition (3), it becomes difficult to suppress higher-order spherical aberration.

[0048] Furthermore, it is preferable that the numerical ranges of conditional expressions (1) and (3) be within the ranges of the following conditional expressions (1a) and (3a).

[0049] -1.100 <fAN / fGP<-0.800 ···(1a) 1.47 <ndAN<1.60 ···(3a) By satisfying condition (1a), axial chromatic aberration in the wide-angle range is suppressed while coma aberration is easily controlled. By satisfying condition (3a), spherical aberration and coma aberration are easily controlled throughout the entire zoom range, which is preferable.

[0050] Furthermore, it is even more preferable to set the numerical ranges of conditional expressions (1) and (3) to the ranges of the following conditional expressions (1b) and (3b).

[0051] -1.050 <fAN / fGP<-0.802 ···(1b) 1.51 <ndAN<1.58 ···(3b) As described above, by appropriately configuring each lens group and simultaneously satisfying conditions (1) and (3), various aberrations such as chromatic aberration and spherical aberration can be well corrected, and a wide-angle, compact zoom lens can be realized that is robust against manufacturing errors.

[0052] Next, we will describe the conditions that are preferably satisfied in the zoom lens of each embodiment. It is preferable that the zoom lens of each embodiment satisfies one or more of the following conditional equations (4) to (13).

[0053] -0.10 <SFA<1.20 ···(4) 0.7 < |APR2 / fGP| < 1.8 ···(5) 70.5 < νdAP < 100.0 ... (6) 0.60<νdAN / νdAP<0.85 (7) -2.00 <fA / fB<-0.50 ···(8) 4.2 < |f1 / f2| < 7.0 ... (9) 3.8 <f1 / fw<5.5 ···(10) 1.0 < |f3 / f2| < 2.8 ···(11) 0.16 <f3 / ft<0.50 ···(12) 56<νd3P<80 ···(13) Here, SFA is the shape factor of cemented lens A. νdAP is the Abbe number of positive lens AP. νdAN is the Abbe number of negative lens AN. fA is the focal length of cemented lens A. fB is the focal length of cemented lens B. f1, f2, and f3 are the focal lengths of the first lens group L1, the second lens group L2, and the third lens group L3, respectively. fw and ft are the focal lengths of the zoom lens at the wide-angle end and the telephoto end, respectively. νd3P is the average Abbe number of the positive lenses in the third lens group L3.

[0054] The Abbe number νd and the partial dispersion ratio θgF are defined by the following equations, where the refractive indices of the Fraunhofer lines d, F, C, and g are Nd, NF, NC, and Ng, respectively.

[0055] νd = (Nd-1) / (NF-NC) θgF = (Ng - NF) / (NF - NC) The shape factor SFA is defined by the following equation, where APR1 is the radius of curvature of the object-side lens surface of cemented lens A, and ANR2 is the radius of curvature of the image-side lens surface. If the lens surface is aspherical, it represents its base R (radius of the reference quadratic surface).

[0056] SFA = -(ANR2 + APR1) / (ANR2 - APR1) Conditional equation (4) is a conditional equation that defines the shape factor of cemented lens A, and is intended to achieve miniaturization while simultaneously correcting spherical aberration and axial chromatic aberration. When the value of conditional equation (4) is 1, cemented lens A has a plano-concave shape with the concave surface facing the image side. If the value exceeds the upper limit of conditional equation (4), it becomes difficult to adequately correct coma aberration at the wide-angle end, and the zoom variation of spherical aberration becomes large, which is undesirable. If the value falls below the lower limit of conditional equation (4), spherical aberration and axial chromatic aberration at the telephoto end become large, which is undesirable.

[0057] Conditional equation (5) is an equation that defines the radius of curvature of the bonding surface of the cemented lens A by the focal length of the lens group GP at the wide-angle end. In order to miniaturize zoom lenses, it is effective to increase the magnification contribution of the lens group GP, but it is necessary to balance this with achromatic aberration, and conditional equation (5) is intended to correct axial chromatic aberration and optimize the magnification contribution. If the upper limit of conditional equation (5) is exceeded, the radius of curvature of the bonding surface becomes too large for the magnification contribution, leading to insufficient correction of axial chromatic aberration at the telephoto end, which is undesirable. If the lower limit of conditional equation (5) is exceeded, the refractive power of the lens group GP becomes weak, and in order to maintain the predetermined magnification ratio, it leads to an increase in the amount of movement of the lens group GP from the wide-angle end to the telephoto end, which is undesirable as it leads to a larger zoom lens.

[0058] Conditional equation (6) specifies the Abbe number of the material for the positive lens AP, and is intended to suppress axial chromatic aberration and correct the insufficient correction of chromatic aberration in the first lens group L1 and the second lens group L2 with lens group GP. Exceeding the upper limit of conditional equation (6) is advantageous for correcting axial chromatic aberration, but it becomes difficult to secure the desired refractive power as a glass material. Exceeding the lower limit of conditional equation (6) is undesirable because it becomes difficult to correct the first-order aberration of axial chromatic aberration and lateral chromatic aberration.

[0059] Conditional equation (7) specifies the ratio of the Abbe number of the positive lens AP to the Abbe number of the negative lens AN in cemented lens A, and is intended to achieve both correction of axial chromatic aberration and correction of spherical and coma aberrations. If the upper limit of conditional equation (7) is exceeded, the Abbe numbers of the positive lens AP and the negative lens AN become closer, the achromatic effect due to the glass material properties weakens, and achromatic correction becomes necessary in lenses other than cemented lens A, leading to an increase in the number of lenses or an increase in the overall length of the lens, which is undesirable. If the lower limit of conditional equation (7) is exceeded, the achromatic effect due to the glass material properties is ensured, but the radius of curvature of the cemented surface becomes large, making it difficult to ensure the refractive power of the positive lens AP, and problems tend to arise in correcting chromatic aberration, which is undesirable.

[0060] Conditional equation (8) defines the ratio of the focal length fA of cemented lens A to the focal length fB of cemented lens B, and is intended to achieve both axial chromatic aberration correction and correction of spherical aberration and coma aberration. Furthermore, satisfying conditional equation (8) optimizes the aberration correction distribution between the two sets of cemented lenses A and B, making it easier to ensure robustness against polarization, which becomes a problem when increasing aperture or zoom ratio. Exceeding the upper limit of conditional equation (8) is undesirable because the refractive power of cemented lens A becomes too strong, the incident light beam to cemented lens B tends to become divergent light, and this tends to lead to an increase in coma aberration due to polarization of cemented lens B. Exceeding the lower limit of conditional equation (8) is undesirable because the refractive power of cemented lens A becomes too weak, which tends to result in insufficient correction of spherical aberration, especially at the telephoto end.

[0061] Conditional equation (9) is an equation that defines the focal length of the first lens group L1 as the focal length of the second lens group L2, and is intended to maintain an appropriate magnification ratio and miniaturize the zoom lens. In zoom lenses with a relatively bright telephoto end, if the refractive power of the first lens group L1 is not appropriately secured within the range where aberration correction is possible, the overall length of the zoom lens on the telephoto end will increase, and furthermore, the diameter of the front element will have to be enlarged in order to secure peripheral illumination. If the upper limit of conditional equation (9) is exceeded, the aberration fluctuations of the first lens group L1 and the second lens group L2 during zooming will become large, making it difficult to correct spherical aberration in particular, which is undesirable. If the lower limit of conditional equation (9) is exceeded, the refractive power of the first lens group L1 will become small, increasing the overall length of the zoom lens, and furthermore, it will become difficult to secure peripheral illumination, which is undesirable.

[0062] Conditional equation (10) defines the focal length of the first lens group L1 as the focal length of the zoom lens at the wide-angle end, and is intended to optimize the distribution of magnification while miniaturizing the lens. By setting a desired refractive power for the first lens group L1, the amount of movement of the first lens group L1 during zooming can be suppressed. If the upper limit of conditional equation (10) is exceeded, the refractive power of the first lens group L1 becomes weak, and the magnification effect weakens. If the amount of movement of the first lens group L1 is increased during zooming to compensate for the magnification effect, the overall length increases at the telephoto end, which is undesirable. Also, if the upper limit of conditional equation (10) is exceeded, the distribution of magnification must be ensured by the lens groups from the third lens group L3 onwards, in which case various aberrations such as spherical aberration and coma aberration will occur at the telephoto end. As a result, the number of lenses and aspherical lenses will increase to correct aberrations, which tends to lead to a loss of robustness against manufacturing errors, and is undesirable. If the value falls below the lower limit of condition (10), the refractive power of the first lens group L1 becomes too strong, and more spherical aberration occurs than in the first lens group L1 at the telephoto end, which is undesirable.

[0063] Conditional equation (11) is an equation that defines the focal length of the third lens group L3 as the focal length of the second lens group L2, and is intended to ensure a good balance between spherical aberration and coma aberration while maintaining a good balance between zoom and refraction. If the upper limit of conditional equation (11) is exceeded, the refractive power of the third lens group L3 becomes too weak, the zoom effect weakens, and it is undesirable because it leads to an increase in the amount of movement of the third lens group L3 during zooming. If the lower limit of conditional equation (11) is exceeded, the refractive power of the third lens group L3 becomes too strong, which is undesirable because it causes spherical aberration, coma aberration, and astigmatism in the center of the image at the telephoto end.

[0064] Conditional equation (12) defines the focal length of the third lens group L3 as the focal length of the zoom lens at the telephoto end, and is intended to achieve both correction of field curvature in the telephoto range and miniaturization of the zoom lens. If the upper limit of conditional equation (12) is exceeded, the refractive power of the third lens group L3 becomes too weak, making it easy for field curvature at the telephoto end to increase, which is undesirable. If the lower limit of conditional equation (12) is exceeded, the refractive power of the third lens group L3 becomes too strong, causing fluctuations in coma aberration with respect to image height at the telephoto end, which is also undesirable.

[0065] Conditional equation (13) is an equation that specifies the average Abbe number of the positive lenses included in the third lens group L3, and is intended to reduce the overall length of the lens and suppress axial chromatic aberration and lateral chromatic aberration. Exceeding the upper limit of conditional equation (13) is advantageous in suppressing axial chromatic aberration and lateral chromatic aberration, but it is undesirable because the radius of curvature of the lens approaches zero, leading to insufficient correction of spherical aberration and coma aberration. Exceeding the lower limit of conditional equation (13) is undesirable because chromatic aberration becomes large, making it difficult to correct aberrations for the zoom lens as a whole.

[0066] Furthermore, it is more preferable that the numerical ranges of conditional expressions (4) to (13) be within the ranges of the following conditional expressions (4a) to (13a).

[0067] -0.07 <SFA<1.00 ···(4a) 0.8 < |APR2 / fGP| < 1.7 ···(5a) 70.6 < νdAP < 96.0 ···(6a) 0.65<νdAN / νdAP<0.80 (7a) -1.70 <fA / fB<-0.54 ···(8a) 4.4 < |f1 / f2| < 6.0 ···(9a) 4.0 <f1 / fw<5.0 ···(10a) 1.1 < |f3 / f2| < 2.4 ···(11a) 0.18 <f3 / ft<0.45 ···(12a) 60 < νd3P < 77 ···(13a) By satisfying condition (4a), spherical aberration correction in the wide-angle range becomes more appropriate, making it easier to achieve a larger aperture. By satisfying condition (5a), correction of axial chromatic aberration and optimization of magnification distribution become easier. By satisfying condition (6a), axial chromatic aberration in the telephoto range becomes easier to correct. By satisfying condition (7a), fluctuations in axial chromatic aberration due to zooming become easier to suppress. By satisfying condition (8a), it becomes easier to optimize the aberration correction distribution of the two sets of cemented lenses. By satisfying condition (9a), the overall length of the lens becomes easier to shorten. By satisfying condition (10a), correction of chromatic aberration at the wide-angle end and spherical aberration at the telephoto end becomes easier to achieve simultaneously. By satisfying condition (11a), the magnification distribution of the third lens group L3 becomes more appropriate, making it easier to suppress zooming fluctuations in coma aberration. By satisfying condition (12a), it becomes easier to suppress variations in coma aberration with respect to the angle of view in the telephoto range. By satisfying condition (13a), it becomes easier to reduce the overall length of the lens.

[0068] Furthermore, it is even more preferable that the numerical ranges of conditional expressions (4) to (13) be within the ranges of the following conditional expressions (4b) to (13b).

[0069] -0.05 <SFA<0.70 ···(4b) 0.90<|APR2 / fGP|<1.65 (5b) 70.69 < νdAP < 83.00 ···(6b) 0.68<νdAN / νdAP<0.75 (7b) -1.60 <fA / fB<-0.57 ···(8b) 4.6 < |f1 / f2| < 5.4 ... (9b) 4.1 <f1 / fw<4.8 ···(10b) 1.2 < |f3 / f2| < 2.2 ···(11b) 0.20 <f3 / ft<0.40 ···(12b) 62<νd3P<74 ···(13b) Next, we will describe the preferred configurations for each embodiment of the zoom lens.

[0070] The first lens group L1 preferably consists of three or fewer lenses.

[0071] This configuration allows for a reduction in the number of elements in the first lens group L1, which has a large lens diameter, thus enabling miniaturization and weight reduction. Furthermore, it lowers the height of the light rays emitted from the first lens group L1, allowing for better correction of off-axis aberrations such as coma and field curvature.

[0072] The first lens group L1 preferably consists of a cemented lens of a negative lens and a positive lens, and a single meniscus-shaped lens with positive refractive power, arranged in order from the object side to the image side. This configuration makes it easy to effectively correct chromatic aberration across the entire zoom range, as well as spherical aberration and axial chromatic aberration at the telephoto end.

[0073] Furthermore, the second lens group L2 preferably consists of four spherical lenses arranged in order from the object side to the image side: a lens with negative refractive power, a lens with negative refractive power, a lens with positive refractive power, and a lens with negative refractive power. By configuring the second lens group L2 with spherical lenses, surface shape errors (so-called asymmetric or quirky component errors) that tend to occur with aspherical lenses can be suppressed.

[0074] This configuration enhances the refractive power of the second lens group L2 while simultaneously correcting chromatic aberration and field curvature in the wide-angle range and spherical aberration in the telephoto range. By positioning the negative lens closest to the object in the second lens group L2, the power distribution within the second lens group L2 can be made retrofocus type, resulting in excellent correction of field curvature and coma aberration in the wide-angle range.

[0075] The third lens group L3 preferably includes a single convex lens with positive refractive power that is positioned closest to the object. The light beam incident on the third lens group from the second lens group L2, which is the main magnification group, has a higher ray height, which causes higher-order spherical aberration and coma aberration. Therefore, in order to effectively suppress the occurrence of spherical aberration and coma aberration, a single convex lens with positive refractive power is positioned closest to the object in the third lens group L3, thereby focusing the light beam diverged by the second lens group L2.

[0076] Furthermore, in the lens group positioned closest to the image sensor, it is preferable that the lens positioned closest to the image sensor is a positive lens that is convex toward the image sensor. This configuration makes it relatively easy to secure back focus and suppresses the collection of unwanted light (ghosting) caused by the image sensor.

[0077] Furthermore, it is preferable that the rear group RG has at least one aspherical surface. This configuration allows for effective correction of field curvature at the wide-angle end while also enabling miniaturization of the zoom lens.

[0078] Furthermore, it is preferable that the image-side lens adjacent to the aperture diaphragm SP consists of a biconvex lens element (single lens or cemented lens) with a strongly convex shape toward the object. By positioning the lens surface with a strongly convex shape facing the aperture diaphragm SP, it becomes easier to suppress spherical aberration associated with large apertures and to correct off-axis aberrations in the wide-angle range. Moreover, by configuring the strongly convex lens element to have an aspherical surface, it becomes easier to correct both spherical aberration and coma aberration, as well as field curvature.

[0079] In the zoom lenses of each embodiment, vibration isolation can be achieved by moving any entire lens group or a part thereof as a vibration isolation group so as to include a component perpendicular to the optical axis, or by rotating (oscillating) it in an in-plane direction including the optical axis. In particular, it is preferable to use cemented lens B as the vibration isolation group. There are no particular restrictions on the number or shape of lenses in the vibration isolation group. Furthermore, it is preferable that the vibration isolation group has a positive refractive power. Furthermore, it is preferable that the vibration isolation group consists of a part of one lens group, and more preferably consists of the central part of one lens group divided into three parts.

[0080] In the zoom lenses of each embodiment, focusing can also be achieved by moving any entire lens group or a part thereof as a focusing group to include a component in the optical axis direction.

[0081] Next, we will describe the zoom lenses of each embodiment in detail.

[0082] In Example 1 of Figure 1, L1 is the first lens group with positive refractive power, L2 is the second lens group with negative refractive power, L3 is the third lens group with positive refractive power, L4 is the fourth lens group with positive refractive power, L5 is the fifth lens group with negative refractive power, L6 is the sixth lens group with negative refractive power, and L7 is the seventh lens group with positive refractive power. Lens group GP consists of the third lens group L3 and the fourth lens group L4. Joined lens A is a negative refractive power lens element formed by joining the ninth lens (counting from the object side) and the tenth lens (counting from the object side). Joined lens B is a positive refractive power lens element formed by joining the eleventh lens (counting from the object side) and the twelfth lens (counting from the object side).

[0083] In the zoom lens of Example 1, when zooming from the wide-angle end to the telephoto end, the first lens group L1 moves monotonically toward the object. At the telephoto end, the distance between the first lens group L1 and the second lens group L2 is wider than at the wide-angle end, the distance between the second lens group L2 and the third lens group L3 is narrower, and the distance between the third lens group L3 and the fourth lens group L4 is wider. The fifth lens group L5 moves when focusing is achieved.

[0084] In Examples 2, 3, and 4 shown in Figures 3, 5, and 7, L1 is the positive first lens group, L2 is the negative second lens group, L3 is the positive third lens group, L4 is the negative fourth lens group, L5 is the negative fifth lens group, and L6 is the positive sixth lens group. Lens group GP is the third lens group L3.

[0085] In Examples 2 and 4, cemented lens A is a negative refractive power lens element formed by joining the 9th lens and the 10th lens. Cemented lens B is a positive refractive power lens element formed by joining the 11th lens and the 12th lens. In Example 3, cemented lens A is a negative refractive power lens element formed by joining the 10th lens and the 11th lens, and cemented lens B is a positive refractive power lens element formed by joining the 12th lens and the 13th lens.

[0086] In the zoom lenses of Examples 2, 3, and 4, the first lens group L1 moves monotonically toward the object when zooming from the wide-angle end to the telephoto end. The lens groups move such that the distance between the first lens group L1 and the second lens group L2 is wider at the telephoto end compared to the wide-angle end, and the distance between the second lens group L2 and the third lens group L3 is narrower. The fourth lens group L4 moves when focusing.

[0087] In Example 5 of Figure 9, L1 is the positive first lens group, L2 is the negative second lens group, L3 is the positive third lens group, L4 is the negative fourth lens group, and L5 is the positive fifth lens group. Lens group GP is the third lens group L3. Bonded lens A is a negative refractive power lens element formed by bonding the ninth lens and the tenth lens. Bonded lens B is a positive refractive power lens element formed by bonding the eleventh lens and the twelfth lens.

[0088] In the zoom lens of Example 5, when zooming from the wide-angle end to the telephoto end, the first lens group L1 moves monotonically toward the object. The lens groups move such that the distance between the first lens group L1 and the second lens group L2 is wider at the telephoto end compared to the wide-angle end, and the distance between the second lens group L2 and the third lens group L3 is narrower. When focusing, the fourth lens group L4 moves.

[0089] In Embodiment 6 of Figure 11, L1 is the positive first lens group, L2 is the negative second lens group, L3 is the positive third lens group, L4 is the positive fourth lens group, L5 is the negative fifth lens group, and L6 is the positive sixth lens group. Lens group GP consists of the third lens group L3 and the fourth lens group L4. Bonded lens A is a negative refractive power lens element formed by bonding the ninth lens and the tenth lens. Bonded lens B is a positive refractive power lens element formed by bonding the eleventh lens and the twelfth lens.

[0090] In the zoom lens of Example 6, the first lens group L1 moves monotonically toward the object when zooming from the wide-angle end to the telephoto end. At the telephoto end, the distance between the first lens group L1 and the second lens group L2 is wider than at the wide-angle end, the distance between the second lens group L2 and the third lens group L3 is narrower, and the distance between the third lens group L3 and the fourth lens group L4 is narrower. When focusing, the fifth lens group L4 moves.

[0091] The numerical values ​​corresponding to Examples 1 to 6 are shown below.

[0092] In the surface data for each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axial spacing (distance along the optical axis) between the m-th surface and the (m+1)-th surface. Here, m is the surface number counted from the light incidence side. Furthermore, nd represents the refractive index of each optical element with respect to the d-line, and νd represents the Abbe number of the optical element. Note that the Abbe number νd and partial dispersion ratio θgF of a certain material are given by Nd, NF, and NC, respectively, when the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), C-line (656.3 nm), and g-line (435.8 nm) are Nd, NF, and NC. νd = (Nd-1) / (NF-NC) θgF = (Ng - NF) / (NF - NC) It is represented as follows.

[0093] In each numerical example, d, focal length (mm), F-number, and half-angle of view (°) are all values ​​when the zoom lens of each example is focused on an object at infinity. "Back focus BF" is the distance along the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image plane, expressed in terms of air equivalent length. "Total lens length" is the length obtained by adding the back focus to the distance along the optical axis from the frontmost lens surface (the lens surface closest to the object) to the final surface of the zoom lens. "Lens group" includes not only cases where it is composed of multiple lenses, but also cases where it is composed of a single lens.

[0094] Furthermore, if the optical surface is aspherical, the sign * is added to the right of the surface number. The aspherical shape is defined as follows, where X is the displacement from the surface vertex in the optical axis direction, h is the height from the optical axis perpendicular to the optical axis, R is the paraaxial radius of curvature, k is the cone constant, and A4, A6, A8, A10, and A12 are the aspherical coefficients of their respective orders. x=( h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 ]+A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h 12 This is expressed as follows. Note that "e±XX" in each aspherical coefficient means "×10±XX".

[0095] [Numerical Example 1] Unit: mm Surface data Face number rd nd νd θgF 1 123.206 1.50 1.92286 20.88 0.6391 2 66.828 5.58 1.61800 63.40 0.5395 3 -464.077 0.25 4 43.861 4.97 1.69680 55.53 0.5434 5 151.415 (variable) 6 111.979 0.90 1.95375 32.32 0.5898 7 12.847 5.64 8 -27.915 0.80 1.87070 40.73 0.5686 9 48.809 0.20 10 28.449 4.57 1.92119 23.96 0.6203 11 -26.495 0.59 12 -19.303 0.80 1.72916 54.68 0.5444 13 -68.905 (variable) 14 (aperture) ∞ 0.60 15* 15.738 4.27 1.55332 71.69 0.5402 16* -45.933 0.25 17 52.284 4.08 1.49700 81.54 0.5375 18 -15.890 0.80 1.51823 58.90 0.5457 19 13.720 2.31 20 27.621 0.80 1.83400 37.21 0.5807 21 15.339 3.16 1.59282 68.62 0.5458 22 -315.513 (variable) 23 23.005 4.57 1.61800 63.40 0.5395 24 -13.556 0.80 1.91650 31.60 0.5911 25 -24.224 (variable) 26 67.433 0.80 1.74100 52.64 0.5467 27 13.200 (Variable) 28* -219.833 1.80 1.58313 59.38 0.5423 29 * 193.213 (variable) 30 -79.761 3.77 1.62041 60.29 0.5427 31 -25.977 (variable) Image plane ∞ Aspherical data Page 15 K = 0.00000e+000 A 4=-2.68014e-005 A 6=-1.51087e-007 A 8= 1.84722e-009 A10 = -2.71938e-011 Page 16 K = 0.00000e+000 A 4= 2.76611e-005 A 6=-1.59524e-007 A 8= 2.00775e-009 A10 = -2.74372e-011 Page 28 K = 0.00000e+000 A 4=-2.04383e-004 A 6=-1.04758e-006 A 8= 4.38595e-008 A10=-6.31993e-010 A12= 3.09385e-012 Page 29 K = 0.00000e+000 A 4=-1.81227e-004 A 6=-3.38180e-007 A 8= 2.34179e-008 A10=-3.02899e-010 A12= 1.25523e-012 Various data Zoom ratio 4.40 Wide-angle, Medium, Telephoto Focal length 15.45 36.03 67.94 F-number 4.12 4.12 4.12 Half-angle (°): 41.27, 19.59, 10.60 Image height 12.66 13.66 13.66 Lens length: 100.14, 108.00, 120.23 BF 10.46 10.79 12.37 d 5 0.70 12.96 25.75 d13 22.92 8.59 3.29 d22 0.80 1.27 1.35 d25 1.56 3.50 3.36 d27 8.85 6.45 6.51 d29 1.05 10.66 13.82 d31 10.46 10.79 12.37 Zoom lens group data Group starting plane focal length 1 1 64.00 2 6 -13.48 3 14 26.77 4 23 24.17 5 26 -22.29 6 28 -176.06 7 30 60.47 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd θgF 1 101.257 1.50 1.92286 20.88 0.6391 2 60.291 5.73 1.59282 68.62 0.5458 3 -4456.172 0.25 4 42.966 4.60 1.69680 55.53 0.5434 5 158.953 (variable) 6 99.609 0.90 1.95375 32.32 0.5898 7 13.291 5.85 8 -32.886 0.80 1.87070 40.73 0.5686 9 38.107 0.20 10 27.182 4.69 1.92119 23.96 0.6203 11 -34.023 1.04 12 -19.649 0.80 1.55200 70.70 0.5421 13 -92.753 (variable) 14 (aperture) ∞ 0.60 15* 16.457 4.63 1.58313 59.38 0.5423 16* -68.118 0.25 17 48.885 3.47 1.53775 74.70 0.5392 18 -19.399 0.80 1.51742 52.43 0.5564 19 15.364 2.05 20 29.727 0.80 1.83481 42.74 0.5648 21 16.042 2.96 1.59282 68.62 0.5458 22 -364.901 0.84 23 29.252 5.18 1.72916 54.68 0.5444 24 -11.979 0.80 1.91650 31.60 0.5911 25 -25.127 (variable) 26 975.106 0.80 1.85150 40.78 0.5695 27 15.191 (Variable) 28* 197.091 1.90 1.53110 55.91 0.5684 29 * 60.563 (variable) 30 4252.772 5.11 1.59410 60.47 0.5550 31 -26.104 (variable) Image plane ∞ Aspherical data Page 15 K = 0.00000e+000 A 4=-2.53346e-006 A 6= 1.78537e-007 A 8=-8.04903e-010 A10 = 6.70995e-011 Page 16 K = 0.00000e+000 A 4= 5.48471e-005 A 6= 2.41490e-007 A 8=-1.10585e-009 A10 = 9.23529e-011 Page 28 K = 0.00000e+000 A 4=-2.17094e-004 A 6=-1.28876e-006 A 8= 4.43371e-008 A10=-6.71659e-010 A12= 3.68763e-012 Page 29 K = 0.00000e+000 A 4=-1.88532e-004 A 6=-4.86363e-007 A 8= 2.32061e-008 A10=-2.91056e-010 A12= 1.30530e-012 Various data Zoom ratio 4.40 Wide-angle, Medium, Telephoto Focal length 15.45 36.49 68.04 F-numbers: 2.88, 3.86, 4.12 Half-angle (°): 41.38, 19.53, 10.61 Image height 12.66 13.66 13.66 Lens length: 100.32, 110.44, 118.71 BF 10.62 11.68 15.59 d 5 0.70 14.07 25.79 d13 22.06 8.62 1.17 d25 1.69 3.05 3.66 d27 7.78 6.42 5.81 d29 0.91 10.04 10.13 d31 10.62 11.68 15.59 Zoom lens group data Group starting plane focal length 1 1 64.00 2 6 -13.50 3 14 16.59 4 26 -18.13 5 28 -165.42 6 30 43.69 [Numerical Example 3] Unit: mm Surface data Face number rd nd νd θgF 1 97.661 1.50 1.92286 20.88 0.6391 2 58.555 5.87 1.59282 68.62 0.5458 3 -1996.145 0.25 4 44.217 4.84 1.69680 55.53 0.5434 5 169.020 (variable) 6 130.464 0.90 1.95375 32.32 0.5898 7 13.417 5.61 8 -33.393 0.80 1.87070 40.73 0.5686 9 33.979 0.20 10 25.723 4.84 1.92119 23.96 0.6203 11 -33.108 1.05 12 -19.402 0.80 1.55200 70.70 0.5421 13 -71.066 (variable) 14 (aperture) ∞ 0.60 15 15.204 0.70 1.65160 58.55 0.5425 16 9.870 4.90 1.51633 64.06 0.5333 17* -95.198 0.25 18 22.963 3.84 1.55200 70.70 0.5421 19 -24.345 0.80 1.57099 50.80 0.5588 20 15.024 1.55 21 27.122 0.80 1.85150 40.78 0.5695 22 15.005 3.00 1.59282 68.62 0.5458 23 -233.617 0.58 24 28.481 4.97 1.72916 54.68 0.5444 25 -12.138 0.80 1.83400 37.34 0.5790 26 -30.268 (variable) 27 272.727 0.80 1.85150 40.78 0.5695 28 14.980 (Variable) 29* -304.916 1.90 1.53110 55.91 0.5684 30 * 166.458 (variable) 31 -209.281 3.84 1.59410 60.47 0.5550 32 -28.556 (variable) Image plane ∞ Aspherical data Page 17 K = 0.00000e+000 A 4= 3.94800e-005 A 6=-2.50399e-008 A 8=-1.60986e-010 A10 = -6.81649e-012 Page 29 K = 0.00000e+000 A 4=-2.34513e-004 A 6=-7.30053e-007 A 8= 3.42430e-008 A10=-6.55075e-010 A12= 4.36794e-012 Page 30 K = 0.00000e+000 A 4=-1.90964e-004 A 6=-2.32987e-007 A 8= 1.99577e-008 A10=-3.06930e-010 A12= 1.65135e-012 Various data Zoom ratio 4.40 Wide-angle, Medium, Telephoto Focal length 15.45 36.47 68.05 F-numbers: 2.88, 3.81, 4.12 Half-angle (°): 41.28, 19.17, 10.42 Image height 12.66 13.66 13.66 Lens length: 100.14, 109.96, 118.75 BF 11.46 9.98 13.02 d 5 0.70 14.51 25.88 d13 22.49 9.61 2.72 d26 1.67 2.83 3.01 d28 6.99 5.82 5.65 d30 0.84 11.22 12.49 d32 11.46 9.98 13.02 Zoom lens group data Group starting plane focal length 1 1 63.50 2 6 -13.80 3 14 16.60 4 27 -18.64 5 29 -202.46 6 31 55.22 [Numerical Example 4] Unit: mm Surface data Face number rd nd νd θgF 1 87.053 1.80 1.92119 23.96 0.6203 2 55.246 6.60 1.52841 76.46 0.5396 3 4555.935 0.25 4 51.113 4.99 1.69680 55.53 0.5434 5 211.575 (variable) 6 88.373 0.90 1.95375 32.32 0.5898 7 13.186 5.83 8 -37.162 0.80 1.87070 40.73 0.5686 9 35.339 0.20 10 24.993 4.60 1.92119 23.96 0.6203 11 -39.335 1.20 12 -19.465 0.80 1.49700 81.54 0.5375 13 -141.682 (variable) 14 (aperture) ∞ 0.60 15* 16.997 4.59 1.58313 59.38 0.5423 16* -53.106 0.25 17 92.533 3.52 1.55200 70.70 0.5421 18 -16.940 0.80 1.51742 52.43 0.5564 19 15.864 2.13 20 26.027 0.80 1.83400 37.21 0.5807 21 14.231 3.39 1.59282 68.62 0.5458 22 -180.390 0.91 23 39.643 4.31 1.75500 52.32 0.5474 24 -14.321 0.80 1.91650 31.60 0.5911 25 -27.389 (variable) 26 124.907 0.80 1.85150 40.78 0.5695 27 16.724 (Variable) 28* -310.168 1.90 1.53110 55.91 0.5684 29 * 60.508 (variable) 30 191.151 4.62 1.61800 63.40 0.5395 31 -33.418 (variable) Image plane ∞ Aspherical data Page 15 K = 0.00000e+000 A 4=-1.60043e-005 A 6= 2.57695e-007 A 8=-4.70731e-009 A10 = 6.82356e-011 Page 16 K = 0.00000e+000 A 4= 4.50517e-005 A 6= 3.46001e-007 A 8=-6.66873e-009 A10 = 9.29389e-011 Page 28 K = 0.00000e+000 A 4=-2.30614e-004 A 6= 2.60574e-008 A 8= 2.37314e-008 A10=-3.80826e-010 A12= 2.01550e-012 Page 29 K = 0.00000e+000 A 4=-2.06759e-004 A 6= 7.95814e-007 A 8= 5.13152e-009 A10=-1.10127e-010 A12= 5.43574e-013 Various data Zoom ratio 5.42 Wide-angle, Medium, Telephoto Focal length 15.45 36.29 83.77 F-number 2.88 4.00 5.80 Half-angle (°): 41.36, 19.65, 8.71 Image height 12.66 13.66 13.66 Lens length: 101.54 x 116.35 x 133.85 BF 12.12 12.61 16.91 d 5 0.70 15.37 34.25 d13 20.64 8.48 0.93 d25 1.48 2.89 2.93 d27 8.36 6.94 6.91 d29 0.86 12.68 14.53 d31 12.12 12.61 16.91 Zoom lens group data Group starting plane focal length 1 1 73.20 2 6 -13.60 3 14 16.95 4 26 -22.75 5 28 -95.16 6 30 46.39 [Numerical Example 5] Unit: mm Surface data Face number rd nd νd θgF 1 86.086 1.80 1.92119 23.96 0.6203 2 52.542 6.59 1.52841 76.46 0.5396 3 1004.135 0.25 4 47.766 5.32 1.69680 55.53 0.5434 5 205.752 (variable) 6 63.302 0.90 1.95375 32.32 0.5898 7 12.905 6.22 8 -36.053 0.80 1.87070 40.73 0.5686 9 38.451 0.20 10 28.453 4.43 1.92119 23.96 0.6203 11 -35.825 1.22 12 -18.744 0.80 1.49700 81.54 0.5375 13 -180.756 (variable) 14 (aperture) ∞ 0.60 15* 18.234 4.11 1.58313 59.38 0.5423 16* -71.410 0.25 17 26.853 4.09 1.52841 76.46 0.5396 18 -26.171 0.80 1.51742 52.43 0.5564 19 14.660 2.37 20 23.248 0.80 1.83400 37.21 0.5807 21 13.128 3.58 1.59282 68.62 0.5458 22 4631.643 0.98 23 177.568 3.93 1.75500 52.32 0.5474 24 -13.676 0.80 1.91650 31.60 0.5911 25 -27.550 (variable) 26 -37.269 0.80 1.85150 40.78 0.5695 27 43.931 (Variable) 28* -283.811 1.90 1.69350 53.18 0.5482 29* 103.220 0.30 30 42.041 5.62 1.51633 64.14 0.5353 31 -37.748 (variable) Image plane ∞ Aspherical data Page 15 K = 0.00000e+000 A 4=-1.41740e-005 A 6= 3.99398e-011 A 8=-4.41008e-011 A10 = 7.66400e-012 Page 16 K = 0.00000e+000 A 4= 1.83828e-005 A 6= 5.05825e-008 A 8=-3.04607e-010 A10 = 8.35527e-012 Page 28 K = 0.00000e+000 A 4=-2.29240e-004 A 6= 3.80091e-007 A 8= 1.87469e-008 A10=-2.85983e-010 A12= 1.26659e-012 Page 29 K = 0.00000e+000 A 4=-1.99561e-004 A 6= 9.53036e-007 A 8= 3.72688e-009 A10=-8.61757e-011 A12= 3.56878e-013 Various data Zoom ratio 5.09 Wide-angle, Medium, Telephoto Focal length 16.45 36.35 83.81 F-number 2.88 4.00 5.80 Half-angle (°): 39.72, 20.12, 8.62 Image height 12.66 13.66 13.66 Lens length: 104.42, 114.62, 126.76 BF 11.42 21.32 15.06 d 5 0.70 14.73 33.41 d13 22.19 8.47 0.86 d25 3.37 5.16 7.88 d27 7.29 5.49 10.10 d31 11.42 21.32 15.06 Zoom lens group data Group starting plane focal length 1 1 72.00 2 6 -13.42 3 14 18.72 4 26 -23.57 5 28 59.66 [Numerical Example 6] Unit: mm Surface data Face number rd nd νd θgF 1 85.769 1.80 1.92119 23.96 0.6203 2 52.890 6.70 1.52841 76.46 0.5396 3 4501.929 0.25 4 49.755 5.07 1.69680 55.53 0.5434 5 219.491 (variable) 6 68.665 0.90 1.95375 32.32 0.5898 7 13.105 6.06 8 -34.525 0.80 1.87070 40.73 0.5686 9 35.789 0.20 10 27.935 4.52 1.92119 23.96 0.6203 11 -35.000 1.26 12 -18.276 0.80 1.49700 81.54 0.5375 13 -108.531 (variable) 14 (aperture) ∞ 0.60 15* 18.233 4.11 1.58313 59.38 0.5423 16* -74.739 0.25 17 28.571 3.68 1.55032 75.50 0.5405 18 -31.238 0.80 1.51742 52.43 0.5564 19 14.821 2.01 20 23.757 0.80 1.83400 37.21 0.5807 21 13.197 3.58 1.59282 68.62 0.5458 22 -294.751 (variable) 23 -12460.363 3.68 1.75500 52.32 0.5474 24 -13.773 0.80 1.91650 31.60 0.5911 25 -27.092 (variable) 26 -44.781 0.80 1.85150 40.78 0.5695 27 42.378 (Variable) 28* -226.791 1.60 1.69350 53.18 0.5482 29* 108.870 0.30 30 41.390 5.47 1.51633 64.14 0.5353 31 -39.101 (variable) Image plane ∞ Aspherical data Page 15 K = 0.00000e+000 A 4=-1.46301e-005 A 6=-8.71553e-009 A 8= 1.00002e-010 A10 = 3.85899e-012 Page 16 K = 0.00000e+000 A 4= 1.92197e-005 A 6= 4.43348e-008 A 8=-3.28205e-010 A10 = 5.72268e-012 Page 28 K = 0.00000e+000 A 4=-2.54596e-004 A 6= 4.00949e-007 A 8= 2.01627e-008 A10=-2.77109e-010 A12= 1.16550e-012 Page 29 K = 0.00000e+000 A 4=-2.28119e-004 A 6= 1.12921e-006 A 8= 3.59935e-009 A10=-8.29769e-011 A12= 3.36865e-013 Various data Zoom ratio 5.09 Wide-angle, Medium, Telephoto Focal length 16.48 36.15 83.82 F-number 2.88 4.00 5.80 Half-angle (°): 39.58, 20.07, 8.56 Image height 12.66 13.66 13.66 Lens length: 104.85, 114.65, 126.77 BF 11.80 21.57 15.84 d 5 0.70 14.45 33.20 d13 22.40 8.58 0.89 d22 1.63 1.91 0.78 d25 3.37 5.38 8.39 d27 8.08 5.92 10.81 d31 11.80 21.57 15.84 Zoom lens group data Group starting plane focal length 1 1 71.50 2 6 -13.42 3 14 22.47 4 23 45.02 5 26 -25.46 6 28 61.60 The various values ​​in each numerical example are summarized in Table 1 below.

[0096] [Table 1]

[0097] [Imaging device] Next, an embodiment of a digital still camera (imaging device) 10 using the above-described zoom lens as an imaging optical system will be described with reference to FIG. 13. In FIG. 13, reference numeral 13 denotes a camera body, and reference numeral 11 denotes an imaging optical system constituted by any one of the zoom lenses described in Embodiments 1 to 6. Reference numeral 12 denotes a solid-state imaging device (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built in the camera body and receives and photoelectrically converts an optical image formed by the imaging optical system 11. The camera body 13 may be a so-called single-lens reflex camera having a quick return mirror, or a so-called mirrorless camera not having a quick return mirror.

[0098] By applying the above-described zoom lens to an imaging device such as a digital still camera in this way, an imaging device with a small-sized lens can be obtained. [Lens device] Next, the lens device of the present invention will be described.

[0099] FIG. 14 shows a configuration of a camera system including a lens device 100 as an interchangeable lens for a single-lens camera and a camera body (imaging device) 200 to which the lens device 100 is detachably and communicably attached.

[0100] The lens device 100 has a zoom lens (imaging optical system) similar to those in Embodiments 1 to 6 described above.

[0101] The zoom lens group 102 and the focus lens group 104 perform zooming (changing of the zoom state) and focus adjustment of the imaging optical system by moving in the optical axis direction (the direction of the arrow in the figure), respectively. The lens groups 101 and 103 are fixed lens groups. The aperture unit 114 has a variable aperture opening diameter in order to adjust the amount of light passing through the imaging optical system. Note that the zoom lens group 102 and the focus lens group 104 merely schematically show the lens groups that move during zooming and focusing in the zoom lens of each embodiment, and the positions, lens configurations, and numbers of the lens groups are not limited to the display in FIG. 14.

[0102] The variable magnification lens group 102 and the focus lens group 104 are each held by lens holding frames 105 and 106. The lens holding frames 105 and 106 are held so as to be movable in the optical axis direction by a guide shaft (not shown), and are driven in the optical direction by receiving a driving force from stepping motors 107 and 108 as actuators. Note that the variable magnification lens group 102 may be driven without using the stepping motor 107, and a driving force corresponding to an operation of an operation member such as a zoom ring by the user may be transmitted to the variable magnification lens group 102 using a mechanical cam. Further, in the aperture unit 11, the aperture blades 114a and 114b are driven in the opening and closing directions by a driving force from the aperture actuator 113, thereby changing the aperture opening diameter (that is, the aperture position).

[0103] The lens device 100 has a lens microcomputer (hereinafter referred to as a lens microcomputer) 111 as lens control means. The lens microcomputer 111 controls the driving of the focus lens group 104 (stepping motor 108) and the variable magnification lens group 102 (stepping motor 107) according to user operations such as a focus operation ring 130 and a zoom switch (not shown). The focus operation ring 130, the zoom switch, etc. are operation members provided on the lens device 100.

[0104] During zooming, the optical arrangement of each lens of the imaging optical system changes. The zoom position detection unit 116 is a detection unit that detects at least one position (hereinafter referred to as the zoom position) of the lenses constituting the variable magnification lens group 102 that moves during zooming. The zoom position detection unit 116 is composed of a measuring instrument using a variable resistor, a laser beam, or the like. The zoom position detected by the zoom position detection unit 116 is input to the lens microcomputer 111. Note that the zoom position may be detected by other methods, for example, by detecting a change in the distance between two certain lenses.

[0105] Stepping motors 107 and 108 are driven by zoom drive circuit 119 and focus drive circuit 120, respectively, which receive zoom control signals and focus control signals from lens microcontroller 111. To compensate for focus fluctuations associated with zooming due to the movement of the variable magnification lens group 102, the lens microcontroller 111 controls the focus lens group 104 (stepping motor 108) using electronic cam data stored in memory 112. The lens microcontroller 111 also performs control in response to various lens control commands transmitted from the camera body 200 (camera microcontroller 205, described later).

[0106] In the aperture unit 114, the aperture position, which is the position of the aperture blades 114a and 114b in the opening and closing direction, is detected by the aperture position detection unit 115, and this aperture position information is input to the lens microcontroller 111. The aperture position detection unit 115 may be configured as a relative position sensor (incremental encoder) using a photo interrupter or magnetic sensor, or as an absolute position sensor (absolute encoder). The lens microcontroller 111 refers to the detected aperture position and outputs an aperture control signal to the aperture drive circuit 121. The aperture drive circuit 121 drives the aperture actuator 113 according to the aperture control signal. In this embodiment, a stepping motor is used as the aperture actuator 113, but other actuators such as a voice coil motor may also be used.

[0107] The focus operation ring 130 is an operating member for manual focus (MF) operation, which allows the user to input instructions to move the focus lens group 104 to any position. The rotation direction and amount of rotation of the focus operation ring 130 are detected by the rotation detection unit 131. The rotation detection unit 131 consists of a photo interrupter and a slit light-shielding plate that rotates between the light-emitting part and the light-receiving part of the photo interrupter in accordance with the rotation of the focus operation ring 130. The photo interrupter outputs a pulse signal by alternating the position of the slit-shaped light-transmitting part and the light-shielding part of the slit light-shielding plate between the light-emitting part and the light-receiving part. The pulse signal is input to the lens microcontroller 111. The lens microcontroller 111 detects the amount of rotation of the focus operation ring 130 by counting the pulse signal.

[0108] The rotation detection unit 131 is composed of two photointerrupters and one slit light-shielding plate, which are arranged at a predetermined distance from each other. The lens microcontroller 111 can determine the rotation direction of the focus operation ring 130 by identifying which of the output pulse waveforms from the two photointerrupters is leading in phase.

[0109] Furthermore, the rotation speed of the focus operation ring 130 can be detected (calculated) by measuring the time from the edge where the level of the output signal of one photointerrupter switches to the edge of the output signal of the other photointerrupter. However, if the two photointerrupters are not positioned at the interval specified in the design, the dimensional error will appear as a time error between the edges, making it impossible to detect the rotation speed accurately. Since this problem does not occur between the edges of the output signals of one photointerrupter, in this embodiment, the lens microcontroller 111 detects the rotation speed of the focus operation ring 130 using the time interval in which these edges appear.

[0110] The lens microcontroller 111 controls the drive of the focus lens group 104 (stepping motor 108) via the focus drive circuit 120 in response to MF operation information detected through the rotation detection unit 131 and focus drive commands transmitted from the camera microcontroller 205. The MF operation information includes the direction of rotation, the amount of rotation, and the rotation speed. In this embodiment, the rotation detection unit 131 is configured using a photo interrupter, but it may also be configured using a capacitive sensor, a magnetic sensor, or the like.

[0111] Furthermore, the lens microcontroller 111 controls the drive of the aperture unit 114 (aperture actuator 113) via the aperture drive circuit 121 in response to aperture drive commands transmitted from the camera microcontroller 205.

[0112] Next, the camera body 200 will be described. The camera body 200 has an image sensor 201, which is composed of a CCD sensor or CMOS sensor, etc., that captures (photoelectrically converts) the subject image formed by the lens device 100. The camera body 200 also has an A / D conversion circuit 202, a signal processing circuit 203, a recording unit 204, a camera microcomputer (camera microcontroller) 205 as a camera control means, and a display unit 206.

[0113] The image sensor 201 converts the subject image into an electrical signal (analog signal) via photoelectric conversion. This analog signal is converted into a digital signal by the A / D conversion circuit 202, and this digital signal is input to the signal processing circuit 203. The signal processing circuit 203 performs various signal processing on the input digital signal to generate a focus signal representing the focus state of the imaging optical system (subject image), a luminance signal representing the exposure state, and a video signal. The video signal generated by the signal processing circuit 203 is sent to the recording unit 204, and still image data and video data obtained from this video signal are recorded in the recording unit 204. In addition, the video corresponding to the video signal is displayed as a live view image on the display unit 206. The user can check the imaging composition and focus state by viewing the live view image.

[0114] The camera body 200 and the lens unit 100 are mechanically and electrically connected by a mounting mechanism, the mount 300. The lens unit 100 receives power from the camera body 200 via a power terminal provided on the mount 300. The camera microcontroller 205 and the lens microcontroller 111 communicate with each other via a communication terminal provided on the mount 300.

[0115] The camera microcontroller 205 controls the camera body 200 in response to inputs from an image capture instruction switch, a camera setting switch, and other switches located on the camera body 200 (not shown). The camera microcontroller 205 also transmits zoom drive commands, aperture drive commands, and focus drive commands to the lens microcontroller 111.

[0116] Although preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of its gist. [Explanation of Symbols]

[0117] 100 Lens device L1 First lens group L2 Second lens group L3 Third lens group RG rear group A First cemented lens B. Second cemented lens AP 1st Lens AN 2nd lens

Claims

1. A zoom lens comprising a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a rear group including two or more lens groups, arranged in order from the object side to the image side, wherein the spacing between adjacent lens groups changes during zooming, and a lens device having an actuator for moving the focus group included in the zoom lens that moves during focusing, When zooming from the wide-angle end to the telephoto end, the first lens group moves, the distance between the first lens group and the second lens group widens, and the distance between the second lens group and the third lens group narrows. If the third lens group, or the lens group arranged continuously on the image side relative to the third lens group, is a lens group with positive refractive power, then the lens group composed of the third lens group and the lens group with positive refractive power is considered a positive group. The positive group includes a first cemented lens with negative refractive power and a second cemented lens with positive refractive power positioned adjacent to the image side of the first cemented lens. The first cemented lens consists of a first lens with positive refractive power and a biconvex shape, arranged in order from the object side to the image side, and a second lens with negative refractive power. When fGP is the focal length at the wide-angle end of the positive group, fAN is the focal length of the second lens as a single lens, APR1 is the radius of curvature on the object side of the first lens, APR2 is the radius of curvature on the image side of the first lens, νdAP is the Abbe number of the first lens in the first cemented lens, and νdAN is the Abbe number of the second lens in the first cemented lens, -1.200<fAN / fGP<-0.795 0.001<|APR2 / APR1|≦1.060 0.60<νdAN / νdAP<0.85 A lens device characterized by satisfying the following conditional equation.

2. When the radius of curvature of the image side of the first cemented lens is APR2, 0.7<|APR2 / fGP|<1.8 The lens device according to claim 1, characterized in that it satisfies the following condition.

3. 70.5<νdAP<100.0 The lens device according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

4. When the focal length of the first cemented lens is fA and the focal length of the second cemented lens is fB, -2.00<fA / fB<-0.50 A lens device according to any one of claims 1 to 3, characterized in that it satisfies the following conditional expression.

5. When the focal length of the first lens group is f1 and the focal length of the second lens group is f2, 4.2<|f1 / f2|<7.0 A lens device according to any one of claims 1 to 4, characterized in that it satisfies the following conditional expression.

6. When the focal length of the first lens group is f1 and the focal length of the zoom lens at the wide-angle end is fw, 3.8<f1 / fw<5.5 A lens device according to any one of claims 1 to 5, characterized in that it satisfies the following conditional expression.

7. When the focal length of the second lens group is f2 and the focal length of the third lens group is f3, 1.0<|f3 / f2|<2.8 A lens device according to any one of claims 1 to 6, characterized in that it satisfies the following conditional expression.

8. When the focal length of the third lens group is f3 and the focal length of the zoom lens at the telephoto end is ft, 0.16<f3 / ft<0.50 A lens device according to any one of claims 1 to 7, characterized in that it satisfies the following conditional expression.

9. When the average Abbe number of the positive lenses in the third lens group is νd3P, 56 < νd3P < 80 A lens device according to any one of claims 1 to 8, characterized in that it satisfies the following conditional expression.

10. The lens device according to any one of claims 1 to 9, characterized in that the first lens group consists of three or fewer lenses.

11. The lens device according to any one of claims 1 to 10, characterized in that the first lens group consists of a cemented lens of a negative lens and a positive lens, and a single lens with a positive refractive power in a meniscus shape, arranged in order from the object side to the image side.

12. The lens device according to any one of claims 1 to 11, characterized in that the second lens group consists of four spherical lenses, arranged in order from the object side to the image side, consisting of a negative lens, a negative lens, a positive lens, and a negative lens.

13. The lens apparatus according to any one of claims 1 to 12, characterized in that the third lens group includes a single lens that is positioned closest to the object and has a positive refractive power, and is convex towards the object.

14. The lens device according to any one of claims 1 to 13, characterized in that the lens positioned furthest towards the image side among the lens group positioned furthest towards the image side is a positive lens that is convex toward the image side.

15. The lens apparatus according to any one of claims 1 to 14, characterized in that the rear group has an aspherical surface.

16. The lens device according to any one of claims 1 to 15, characterized in that the image-side lens adjacent to the aperture diaphragm is a biconvex lens element.

17. The lens apparatus according to any one of claims 1 to 16, characterized in that the rear group includes a fourth lens group and a fifth lens group having positive refractive power, arranged in order from the object side to the image side.

18. The lens apparatus according to any one of claims 1 to 16, characterized in that the aforementioned rear group includes a fourth lens group and a fifth lens group having negative refractive power, arranged in order from the object side to the image side.

19. An imaging device characterized by having a lens device according to any one of claims 1 to 18 and an image sensor that receives an image formed by the lens device.

Images