Zoom lens and imaging device
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-11-20
- Publication Date
- 2026-08-13
Smart Images
Figure JP2025040543_13082026_PF_FP_ABST
Abstract
Description
Zoom Lens and Imaging Device
[0001] The present invention relates to a zoom lens suitable for imaging.
[0002] Among zoom lenses, there is a positive lead type zoom lens in which a lens group with the most positive refractive power is arranged on the object side. Patent Documents 1 and 2 disclose a zoom lens using a floating method that is of the positive lead type and moves two lens groups during focusing.
[0003] WO2022 / 259650 Gazette JP-A 2024-133428 Gazette
[0004] In a positive lead type and floating method zoom lens, those having better optical performance than conventional ones have been demanded.
[0005] The zoom lens as one aspect of the present invention is a zoom lens in which the distance between adjacent lens groups changes during zooming, having a first lens group with positive refractive power arranged on the most object side, and having a first negative lens group, a second negative lens group, and a third negative lens group as lens groups with negative refractive power arranged on the image side from the first lens group. During focusing from infinity to the nearest subject, the second negative lens group and the third negative lens group move toward the image side. When the focal length at the wide-angle end of the zoom lens is fw, the focal length at the telephoto end of the zoom lens is ft, the air-equivalent distance on the optical axis from the most image-side final lens surface to the image plane in a state of being focused on an infinite object at the wide-angle end of the zoom lens is Skw, the distance obtained by adding the air-equivalent distance on the optical axis from the final lens surface to the image plane to the distance on the optical axis from the most object-side lens surface to the final lens surface in a state of being focused on an infinite object at the telephoto end of the zoom lens is OVLt, the focal length of the second negative lens group is fn2, and the focal length of the third negative lens group is fn3, it is characterized by satisfying the conditions of 0.33 ≦ Skw / fw ≦ 1.00, 0.50 ≦ OVLt / ft ≦ 0.85, and 1.3 ≦ fn3 / fn2 ≦ 10.0. Note that an imaging device equipped with the above zoom lens also constitutes another aspect of the present invention.
[0006] According to the present invention, it is possible to provide a positive-lead type and floating-type zoom lens that has good optical performance.
[0007] Cross-sectional views of the zoom lens of Example 1 at its wide-angle and telephoto ends. Longitudinal aberration diagram of the zoom lens of Example 1 at infinity focus and wide-angle end. Longitudinal aberration diagram of the zoom lens of Example 1 at infinity focus and intermediate zoom position. Longitudinal aberration diagram of the zoom lens of Example 1 at infinity focus and telephoto end. Longitudinal aberration diagram of the zoom lens of Example 1 at object distance of 0.57m and wide-angle end. Longitudinal aberration diagram of the zoom lens of Example 1 at object distance of 0.57m and intermediate zoom position. Longitudinal aberration diagram of the zoom lens of Example 1 at object distance of 0.57m and telephoto end. Cross-sectional views of the zoom lens of Example 2 at its wide-angle and telephoto ends. Longitudinal aberration diagram of the zoom lens of Example 2 at infinity focus and wide-angle end. Longitudinal aberration diagram of the zoom lens of Example 2 at infinity focus and intermediate zoom position. Longitudinal aberration diagram of the zoom lens of Example 2 at infinity focus and telephoto end. Longitudinal aberration diagram of the zoom lens of Example 2 at an object distance of 0.59m and at the wide-angle end. Longitudinal aberration diagram of the zoom lens of Example 2 at an object distance of 0.59m and at the intermediate zoom position. Longitudinal aberration diagram of the zoom lens of Example 2 at an object distance of 0.59m and at the telephoto end. Cross-sectional views of the zoom lens of Example 3 at the wide-angle and telephoto ends. Longitudinal aberration diagram of the zoom lens of Example 3 at infinity focus and at the wide-angle end. Longitudinal aberration diagram of the zoom lens of Example 3 at infinity focus and at the intermediate zoom position. Longitudinal aberration diagram of the zoom lens of Example 3 at infinity focus and at the telephoto end. Longitudinal aberration diagram of the zoom lens of Example 3 at an object distance of 0.58m and at the wide-angle end. Longitudinal aberration diagram of the zoom lens of Example 3 at an object distance of 0.58m and at the intermediate zoom position. Longitudinal aberration diagram of the zoom lens of Example 3 at an object distance of 0.58m and at the telephoto end. Cross-sectional views of the zoom lens of Example 4 at the wide-angle and telephoto ends. Longitudinal aberration diagram of the zoom lens of Example 4 at infinity focus and wide-angle end. Longitudinal aberration diagram of the zoom lens of Example 4 at infinity focus and intermediate zoom position. Longitudinal aberration diagram of the zoom lens of Example 4 at infinity focus and telephoto end. Longitudinal aberration diagram of the zoom lens of Example 4 at object distance of 0.55m and wide-angle end. Longitudinal aberration diagram of the zoom lens of Example 4 at object distance of 0.55m and intermediate zoom position. Longitudinal aberration diagram of the zoom lens of Example 4 at object distance of 0.55m and telephoto end. Cross-sectional views of the zoom lens of Example 5 at wide-angle and telephoto ends. Longitudinal aberration diagram of the zoom lens of Example 5 at infinity focus and wide-angle end. Longitudinal aberration diagram of the zoom lens of Example 5 at infinity focus and intermediate zoom position.Longitudinal aberration diagram of the zoom lens of Example 5 at infinity focus and telephoto end. Longitudinal aberration diagram of the zoom lens of Example 5 at object distance of 0.57m and wide-angle end. Longitudinal aberration diagram of the zoom lens of Example 5 at object distance of 0.57m and intermediate zoom position. Longitudinal aberration diagram of the zoom lens of Example 5 at object distance of 0.57m and telephoto end. Cross-sectional views of the zoom lens of Example 6 at wide-angle and telephoto ends. Longitudinal aberration diagram of the zoom lens of Example 6 at infinity focus and wide-angle end. Longitudinal aberration diagram of the zoom lens of Example 6 at infinity focus and intermediate zoom position. Longitudinal aberration diagram of the zoom lens of Example 6 at infinity focus and telephoto end. Longitudinal aberration diagram of the zoom lens of Example 6 at object distance of 0.53m and wide-angle end. Longitudinal aberration diagram of the zoom lens of Example 6 at object distance of 0.53m and intermediate zoom position. A longitudinal aberration diagram of the zoom lens of Example 6 at an object distance of 0.53 m and at the telephoto end. A diagram showing the relationship between the Abbe number and the partial dispersion ratio in each example. A schematic diagram of an imaging device equipped with the zoom lens of each example.
[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0009] Figures 1, 8, 15, 22, 29, and 36 show cross-sections of the zoom lenses of Examples 1 to 6 at their wide-angle and telephoto ends, respectively. The zoom lenses of each example are used as imaging optical systems in imaging devices such as video cameras, digital cameras, surveillance cameras, and TV cameras.
[0010] In each cross-sectional view, the left side is the object side (front), and the right side is the image side (rear). L0 is a zoom lens. i indicates the order of the lens groups when counted from the object side, and Li is the i-th lens group. In the zoom lens L0, a lens group is a collection of one or more lenses that move together or not move together during zooming between the wide-angle end and the telephoto end. That is, the distance between adjacent lens groups changes during zooming. The lens group may include an aperture diaphragm. The wide-angle end and telephoto end represent the zoom states of the maximum angle of view (shortest focal length) and minimum angle of view (maximum focal length), respectively, when the lens groups that move during zooming are located at the ends of the range that is mechanically or controllly movable along the optical axis.
[0011] LR is the rear group, which includes one or more lens groups. SP is the aperture diaphragm, which determines (limits) the light beam at the widest aperture F-number (Fno). IP is the image plane. The image plane IP is where the imaging surface of an image sensor such as a CCD sensor or CMOS sensor, or the film surface (photosensitive surface) of a silver halide film, is located.
[0012] In the zoom lens L0 of each embodiment, optical blocks such as optical filters, faceplates, low-pass filters, and infrared cut filters may be arranged on the object side of the image plane IP.
[0013] In each cross-sectional view, the lens group labeled "focus" is the lens group that moves during focusing, and the arrow shown with "focus" indicates the direction of movement of the lens group when focusing from infinity to near distance.
[0014] The zoom lens L0 of each embodiment has multiple lens groups. The multiple lens groups consist of a first lens group L1 with positive refractive power positioned closest to the object, and a rear group LR positioned closer to the image than the first lens group L1. The rear group LR includes a first negative lens group, a second negative lens group, and a third negative lens group adjacent to the second negative lens group on the image side, which are negative refractive power lens groups positioned from the object side. When focusing from infinity to near, the second and third negative lens groups move towards the image side.
[0015] The zoom lens L0 in each embodiment is a positive lead type, with the positive lens group positioned closest to the object, resulting in a telephoto-type lens configuration. This allows for a miniaturization of the entire system while achieving high optical performance with a high zoom ratio.
[0016] Furthermore, in each embodiment, the zoom lens L0 has the aperture diaphragm SP placed within the positive lens group located on the image side of the first negative lens group in the rear group LR, thereby making the effective diameter of the light beam in the optical system on the image side smaller than that of the aperture diaphragm SP.
[0017] Furthermore, as the magnification increases from infinity to close range, the fluctuations in various aberrations associated with focusing, particularly field curvature and chromatic aberration, increase, leading to a decrease in optical performance. For this reason, the zoom lens L0 in each embodiment employs a floating system that moves two lens groups, the second and third negative lens groups, which are positioned closer to the image than the first negative lens group in the rear group LR, during focusing. This suppresses aberration fluctuations during focusing. In addition, by using appropriate glass materials for the lens groups that move during focusing, fluctuations in chromatic aberration are reduced. As a result, high optical performance can be easily obtained even when photographing close-range objects at the telephoto end, where the magnification is 0.5x or more.
[0018] Furthermore, by moving the second and third negative lens groups, which are positioned closer to the image than the aperture diaphragm SP and have relatively small lens diameters and are lightweight within the zoom lens L0, during focusing, the focus drive mechanism that drives them is simplified, and the zoom lens L0 is made smaller. In the zoom lens L0 of each embodiment, the second and third negative lens groups move towards the image when focusing from infinity to close.
[0019] Furthermore, by moving the lens group on the image side during focusing, rather than the aperture diaphragm SP which has a small magnification effect, the change in image magnification during focusing can be reduced. This is effective when capturing video because it reduces the change in the angle of view associated with focusing when an object moves from infinity to very close.
[0020] Figure 1 shows cross-sections of the zoom lens L0 of Example 1 at its wide-angle and telephoto ends. The zoom lens L0 of Numerical Example 1, which corresponds to Example 1, is a zoom lens with a zoom ratio of 4.05 and an F-number of 4.49 to 5.88.
[0021] Figures 2, 3, and 4 show the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the zoom lens L0 of Numerical Example 1 when it is in focus on an object at infinity (hereinafter referred to as the infinity focus state) at the wide-angle end, intermediate zoom position, and telephoto end, respectively. Figures 5, 6, and 7 show the longitudinal aberrations of the zoom lens L0 of Numerical Example 1 at an object distance of 0.57m, which is the distance from the image plane to the object, at the wide-angle end, intermediate zoom position, and telephoto end, respectively.
[0022] In the spherical aberration diagram, Fno indicates the F number, the solid line shows the spherical aberration at the d line (wavelength 587.6 nm), and the dashed line shows the spherical aberration at the g line (wavelength 435.8 nm). In the astigmatism diagram, the solid line S shows the astigmatism at the sagittal image plane, and the dashed line M shows the astigmatism at the meridional image plane. The distortion diagram shows the distortion at the d line. The chromatic aberration diagram shows the lateral chromatic aberration at the g line. ω is the half-angle of view (°). The explanations of these aberration diagrams are the same for the aberration diagrams of other numerical examples described later.
[0023] Figure 8 shows cross-sections of the zoom lens L0 of Example 2 at its wide-angle and telephoto ends. The zoom lens L0 of Numerical Example 2, which corresponds to Example 2, is a zoom lens with a zoom ratio of 4.05 and an F-number of 4.49 to 5.88.
[0024] Figures 9, 10, and 11 show the longitudinal aberrations of the zoom lens L0 of numerical example 2, corresponding to embodiment 2, at infinity focus and at the wide-angle end, intermediate zoom position, and telephoto end, respectively. Figures 12, 13, and 14 show the longitudinal aberrations of the zoom lens L0 of numerical example 2 at an object distance of 0.59 m and at the wide-angle end, intermediate zoom position, and telephoto end, respectively.
[0025] Figure 15 shows cross-sections of the zoom lens L0 of Example 3 at its wide-angle and telephoto ends. The zoom lens L0 of Numerical Example 3, which corresponds to Example 3, is a zoom lens with a zoom ratio of 4.05 and an F-number of 4.49 to 5.88.
[0026] Figures 16, 17, and 18 show the longitudinal aberrations of the zoom lens L0 of numerical example 3 at infinity focus and at the wide-angle end, intermediate zoom position, and telephoto end, respectively. Figures 19, 20, and 21 show the longitudinal aberrations of the zoom lens L0 of numerical example 3 at an object distance of 0.58m and at the wide-angle end, intermediate zoom position, and telephoto end, respectively.
[0027] Figure 22 shows cross-sections of the zoom lens L0 of Example 4 at its wide-angle and telephoto ends. The zoom lens L0 of Numerical Example 4, which corresponds to Example 4, is a zoom lens with a zoom ratio of 4.05 and an F-number of 4.49 to 5.88.
[0028] Figures 23, 24, and 25 show the longitudinal aberrations of the zoom lens L0 of numerical example 4 at infinity focus and at the wide-angle end, intermediate zoom position, and telephoto end, respectively. Figures 26, 27, and 28 show the longitudinal aberrations of the zoom lens L0 of numerical example 4 at an object distance of 0.55m and at the wide-angle end, intermediate zoom position, and telephoto end, respectively.
[0029] Figure 29 shows cross-sections of the zoom lens L0 of Example 5 at its wide-angle and telephoto ends. The zoom lens L0 of Numerical Example 5, which corresponds to Example 5, is a zoom lens with a zoom ratio of 4.05 and an F-number of 4.49 to 5.88.
[0030] Figures 30, 31, and 32 show the longitudinal aberrations of the zoom lens L0 of numerical example 5 at infinity focus and at the wide-angle end, intermediate zoom position, and telephoto end, respectively. Figures 33, 34, and 35 show the longitudinal aberrations of the zoom lens L0 of numerical example 5 at an object distance of 0.57m and at the wide-angle end, intermediate zoom position, and telephoto end, respectively.
[0031] Figure 36 shows cross-sections of the zoom lens L0 of Example 6 at its wide-angle and telephoto ends. The zoom lens L0 of Numerical Example 6, which corresponds to Example 6, is a zoom lens with a zoom ratio of 4.05 and an F-number of 4.49 to 5.88.
[0032] Figures 37, 38, and 39 show the longitudinal aberrations of the zoom lens L0 of numerical example 6 at infinity focus and at the wide-angle end, intermediate zoom position, and telephoto end, respectively. Figures 40, 41, and 42 show the longitudinal aberrations of the zoom lens L0 of numerical example 6 at an object distance of 0.53m and at the wide-angle end, intermediate zoom position, and telephoto end, respectively.
[0033] The following describes the conditions that are preferable for the zoom lens L0 of each embodiment to satisfy.
[0034] In the zoom lens L0 of each embodiment, let fw be the focal length of the entire system at the wide-angle end and ft be the focal length of the entire system at the telephoto end. Skw is the air-equivalent distance (back focus) on the optical axis from the lens surface closest to the image to the image plane when the zoom lens L0 is at the wide-angle end and in focus at infinity, and OVLt is the total optical length of the entire system when the zoom lens L0 is at the telephoto end and in focus at infinity. The total optical length is the length on the optical axis from the lens surface closest to the object to the image plane of the zoom lens L0 (the length on the optical axis from the lens surface closest to the object to the lens surface closest to the image plus the back focus). Also, let fn2 be the focal length of the second negative lens group and fn3 be the focal length of the third negative lens group. In this case, it is preferable that the zoom lens L0 of each embodiment satisfies at least one of the following conditions of equations (1), (2), and (3). It is more preferable that all of the conditions of equations (1), (2), and (3) are satisfied.
[0035] 0.33 ≤ Skw / fw ≤ 1.00 (1) 0.50 ≤ OVLt / ft ≤ 0.85 (2) 1.3 ≤ fn3 / fn2 ≤ 10.0 (3) The conditions in equation (1) indicate an appropriate relationship between the back focus at the wide-angle end and the focal length at the wide-angle end when the lens is in focus at infinity. If Skw / fw falls below the lower limit of equation (1), the back focus becomes too short, making it difficult to secure space for attachment optical units such as rear converters, which is undesirable. If Skw / fw exceeds the upper limit of equation (1), the back focus becomes too long, making the zoom lens larger, which is also undesirable.
[0036] Furthermore, it is more preferable to set the lower limit of formula (1) to 0.40, 0.45, 0.50, or 0.52. Also, it is more preferable to set the upper limit of formula (1) to 0.90, 0.80, 0.70, or 0.60.
[0037] The conditions in equation (2) indicate an appropriate relationship between the total optical length of the entire system and the focal length at the telephoto end when the lens is in focus at infinity. If OVLt / ft falls below the lower limit of equation (2), the refractive power of each lens group becomes too strong, making it difficult to obtain good optical performance throughout the entire zoom range, which is undesirable. If OVLt / ft exceeds the upper limit of equation (2), the refractive power of each lens group becomes too weak, increasing the total optical length and making the zoom lens larger, which is also undesirable.
[0038] Furthermore, it is more preferable to set the lower limit of formula (2) to 0.60, 0.70, or 0.75. Also, it is more preferable to set the upper limit of formula (2) to 0.845 or 0.843.
[0039] The condition in equation (3) indicates an appropriate relationship between the focal length of the second negative lens group, which moves towards the image side during focusing from infinity to near, and the focal length of the third negative lens group. By satisfying this condition, variations in field curvature can be suppressed across the entire object distance from infinity to near. If fn3 / fn2 falls below the lower limit of equation (3), the refractive power of the third negative lens group becomes too strong, overcompensating for variations in field curvature during focusing, which is undesirable. If fn3 / fn2 exceeds the upper limit of equation (3), the refractive power of the third negative lens group becomes too weak, making it difficult to suppress variations in field curvature during focusing, which is also undesirable.
[0040] Furthermore, it is more preferable to set the lower limit of formula (3) to 1.5, 1.8, or 2.0. Also, it is more preferable to set the upper limit of formula (3) to 9.0, 8.0, or 7.0.
[0041] By satisfying the conditions of equations (1) to (3), it is possible to realize a zoom lens that provides high optical performance across all object distances from infinity to the nearest object, with a high zoom ratio.
[0042] When the focal length of the first lens group L1 is f1, the zoom lens L0 of each embodiment preferably satisfies the condition of the following formula (4).
[0043] 1. 0 ≤ |f1 / fn2| ≤ 3.6 (4) The condition of formula (4) shows an appropriate relationship between the focal length of the first lens group L1 and the focal length of the second negative lens group. When |f1 / fn2| is below the lower limit of formula (4), the refractive power of the second negative lens group that moves toward the image side during focusing from infinity to the closest distance becomes too weak, and the movement amount of the second negative lens group increases. As a result, in order to secure the movement space of the second negative lens group, the zoom lens becomes larger, which is not preferable. When |f1 / fn2| exceeds the upper limit of formula (4), the refractive power of the first lens group L1 becomes too weak, and the zoom lens becomes larger, which is not preferable.
[0044] It is more preferable that the lower limit of formula (4) is 1.2, 1.5, 1.8 or 2.0. Also, it is more preferable that the upper limit of formula (4) is 3.2, 3.0 or 2.8.
[0045] In order to obtain high optical performance over the entire object distance with a high zoom ratio while achieving miniaturization, it is preferable to arrange at least one positive lens group between the first negative lens group and the second negative lens group, like the zoom lens L0 of each embodiment. Thereby, a variable magnification action can be caused within the rear group LR.
[0046] In order to obtain higher optical performance in the zoom lens L0 of each embodiment, a first positive lens group as a lens group with positive refractive power is arranged adjacent to the first negative lens group on the image side. At this time, when the focal length of the first lens group L1 is f1 and the focal length of the first positive lens group is fp1, it is preferable to satisfy the condition of the following formula (5).
[0047] 1.0 ≤ f1 / fp1 ≤ 4.6 (5) The condition of formula (5) indicates an appropriate relationship between the focal length of the first lens group L1 and the focal length of the first positive lens group. If f1 / fp1 is below the lower limit of formula (4), the refractive power of the first lens group L1 becomes too strong, making it difficult to obtain good optical performance over the entire zoom range, which is not preferable. If f1 / fp1 exceeds the upper limit of formula (5), the refractive power of the first lens group L1 becomes too weak, causing the zoom lens L0 to increase in size, which is not preferable.
[0048] It is more preferable that the lower limit of formula (5) be 1.2, 1.5, 1.8, or 2.0. It is also more preferable that the upper limit of formula (5) be 4.4, 4.2, 4.0, or 3.5.
[0049] To obtain higher optical performance during focusing, like the zoom lenses L0 of Examples 1, 2, 3, 5, and 6, it is preferable that the second negative lens group be composed of two lenses, a positive lens and a negative lens, arranged in order from the object side to the image side. This allows for good correction of chromatic aberration by the second negative lens group and reduction of the variation in chromatic aberration due to focusing over the entire object distance.
[0050] In the zoom lens L0 of each example, to obtain even higher optical performance during focusing from infinity to the closest distance, when the Abbe number based on the d-line of the negative lens included in the third negative lens group is νdn and the partial dispersion ratio at the g-line and F-line is θgFn, it is preferable to satisfy the conditions of the following formulas (6), (7), and (8).
[0051] 65 ≤ νdn ≤ 100 (6) θgFn ≤ 0.55 (7) θgFn ≥ -0.001682 × νdn + 0.6438 (8) The Abbe number νd based on the d-line and the partial dispersion ratio θgF at the g-line and F-line are expressed as follows: When the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), C-line (656.3 nm), and g-line (wavelength 435.8 nm) are Nd, NF, NC, and Ng, respectively, νd = (Nd - 1) / (NF - NC) θgF = (Ng - NF) / (NF - NC)
[0052] Figure 43 shows the relationship between the Abbe number of a lens material, relative to the d-line, and the partial dispersion ratios of the g-line and F-line. This figure shows, as an example, the Abbe numbers and partial dispersion ratios of two materials manufactured by Ohara Corporation: product name PBM2 (νd = 36.26, θgF = 0.5828) and product name NSL7 (νd = 60.49, θgF = 0.5436). The line connecting the coordinates of these materials in Figure 43 is considered the reference line. For low-dispersion materials, using materials located above the reference line is effective for correcting the secondary spectrum, and the correction effect increases as the material moves further away from the reference line.
[0053] By using materials with appropriate Abbe numbers and partial dispersion ratios for the negative lenses in the third negative lens group that move during focusing, fluctuations in chromatic aberration during focusing can be reduced, and high optical performance can be obtained, especially at close range. Furthermore, with respect to lateral chromatic aberration, the curvature of the g-line as the image height increases can be suppressed.
[0054] Materials that satisfy equations (6) to (8) have low dispersion while possessing anomalous dispersion. This makes it possible to reduce the variation in chromatic aberration due to focusing across all object distances. If νdn falls below the lower limit of equation (6), the achromatic effect becomes insufficient, making it difficult to reduce the variation in chromatic aberration, which is undesirable. If νdn exceeds the upper limit of equation (6), such a material does not exist, which is undesirable. If θgFn exceeds the upper limit of equation (7) or falls below the lower limit of equation (8), the anomalous dispersion of the negative lens material becomes too small, making it difficult to adequately correct lateral chromatic aberration, which is undesirable.
[0055] Furthermore, it is more preferable to set the lower limit of formula (6) to 68 or 70. Also, it is more preferable to set the upper limit of formula (6) to 95, 90, or 85. It is more preferable to set the upper limit of formula (7) to 0.545 or 0.542. It is more preferable to set the lower limit of formula (8) to 0.48 or 0.50.
[0056] In the zoom lens L0 of each embodiment, in order to obtain even higher optical performance during focusing, it is preferable that the following condition of equation (9) is satisfied when the radii of curvature of the object-side and image-side lens surfaces of the negative lens in the third negative lens group are Rnf and Rnr, respectively.
[0057] -10.0 ≤ (Rnf + Rnr) / (Rnf - Rnr) ≤ -1.0 (9) Equation (9) shows an appropriate range for the shape factor that indicates the meniscus shape of the negative lens in the third negative lens group. By satisfying this condition, the variation in field curvature due to focusing can be reduced over the entire object distance. If the shape factor falls below the lower limit of equation (9), the radius of curvature of the object-side lens surface of the negative lens becomes too small, which is undesirable because it overcompensates for the variation in field curvature during focusing. If the shape factor exceeds the upper limit of equation (9), the radius of curvature of the object-side lens of the negative lens becomes too large, which is undesirable because it becomes difficult to suppress the variation in field curvature during focusing.
[0058] Furthermore, it is more preferable to set the lower limit of equation (9) to -8.0, -6.0, or -5.0. Also, it is more preferable to set the upper limit of equation (9) to -1.05, -1.1, or -2.0.
[0059] To achieve even greater compactness and higher optical performance, it is preferable to configure the third negative lens group with a single negative lens, as in the zoom lens L0 of Examples 1, 2, 3, 5, and 6. This makes it possible to lighten the entire focus group consisting of the second and third negative lens groups, simplify the focus drive mechanism, and miniaturize the zoom lens L0.
[0060] To achieve even greater compactness and higher optical performance, it is preferable that the positive lens group adjacent to the second negative lens group on the object side and the third negative lens group move together during zooming, as in the zoom lens L0 of Examples 1 to 6. This simplifies the zoom drive mechanism and allows for miniaturization of the zoom lens L0.
[0061] To achieve even greater compactness and higher optical performance, it is preferable to arrange the first lens group L1 with positive refractive power, the first negative lens group, and the first positive lens group in order from the object side to the image side, as in the zoom lens L0 of Examples 1 to 5. This arrangement results in a positive lead type lens configuration, making it easy to obtain high optical performance across the entire object distance at a high zoom ratio in a telephoto type zoom lens.
[0062] To achieve even greater compactness and higher optical performance, it is preferable that the first negative lens group remains immobile (fixed) relative to the image plane during zooming, as in the zoom lens L0 of Examples 1, 3, 4, 5, and 6. This simplifies the zoom drive mechanism and allows for miniaturization of the zoom lens L0. Furthermore, by immobilizing the first negative lens group during zooming, it is suitable for reducing (correcting) image shake caused by camera shake, etc., by moving the first negative lens group in a direction that includes a component perpendicular to the optical axis.
[0063] To achieve even greater compactness and higher optical performance, it is preferable to arrange a positive lens group as the final lens group between the third negative lens group and the image plane, as in the zoom lens L0 of Examples 1, 2, 3, 5, and 6. This allows for an appropriate setting of the refractive power of the third negative lens group, enabling a balance between suppressing aberration fluctuations associated with changes in object distance and achieving appropriate focus sensitivity.
[0064] To achieve even greater compactness and higher optical performance, it is preferable that the final lens group remains immobile relative to the image plane during zooming, as in the zoom lens L0 of Examples 1, 2, 5, and 6. This simplifies the zoom drive mechanism and allows for a smaller zoom lens L0.
[0065] The zoom lens L0 of each embodiment will be described in detail below.
[0066] The zoom lens L0 of Embodiment 1 (Numerical Example 1) shown in Figure 1 is composed of a first lens group L1 and a rear lens group LR, which are arranged in order from the object side to the image side, and have positive refractive power. The rear lens group LR is composed of a second lens group L2 as the first negative lens group, a third lens group L3 as the first positive lens group, a fourth lens group L4 as the second negative lens group, a fifth lens group L5 as the third negative lens group, and a sixth lens group L6 as the final lens group with positive refractive power, which are arranged in order from the object side to the image side.
[0067] The first lens group L1 consists of a positive lens and a cemented lens formed by a negative lens and a positive lens, arranged in order from the object side to the image side. The second lens group L2 consists of a negative lens, a positive lens, a negative lens and a negative lens, arranged in order from the object side to the image side. The third lens group L3 is a positive lens group adjacent to the second negative lens group on the object side, and consists of a cemented lens formed by a negative lens and a positive lens, a cemented lens formed by a positive lens and a negative lens, an aperture diaphragm SP, a cemented lens formed by a negative lens and a positive lens, and a positive lens, arranged in order from the object side to the image side. The fourth lens group L4 consists of a positive lens and a negative lens, arranged in order from the object side to the image side. The fifth lens group L5 consists of a single negative meniscus lens that is convex on the image side, arranged in order from the object side to the image side. The sixth lens group L5 consists of a single positive lens.
[0068] When zooming from the wide-angle end to the telephoto end, the first lens group L1, the third lens group L3, the fourth lens group L4, and the fifth lens group L5 move toward the object, with the third lens group L3 and the fifth lens group L5 moving together. The second lens group L2 and the sixth lens group L6 remain stationary relative to the image plane IP. When focusing from infinity to close, the fourth lens group L4 and the fifth lens group L5 move toward the image.
[0069] As is clear from the aberration diagrams in Figures 2 to 7, the zoom lens in numerical example 1 shows that various aberrations are well corrected.
[0070] The zoom lens L0 of Embodiment 2 (Numerical Example 2) shown in Figure 8 is composed of a first lens group L1 and a rear lens group LR, which are arranged in order from the object side to the image side, and have positive refractive power. The rear lens group LR is composed of a second lens group L2 as the first negative lens group, a third lens group L3 as the first positive lens group, a fourth lens group L4 as the second negative lens group, a fifth lens group L5 as the third negative lens group, and a sixth lens group L6 as the final lens group with positive refractive power, which are arranged in order from the object side to the image side.
[0071] The first lens group L1 consists of a positive lens and a cemented lens formed by a negative lens and a positive lens, arranged in order from the object side to the image side. The second lens group L2 consists of a negative lens, a positive lens, a negative lens and a negative lens L24, arranged in order from the object side to the image side. The third lens group L3 is a positive lens group adjacent to the second negative lens group on the object side, and consists of a cemented lens formed by a negative lens and a positive lens, a cemented lens formed by a positive lens and a negative lens, an aperture diaphragm SP, a cemented lens formed by a negative lens and a positive lens and a positive lens, arranged in order from the object side to the image side. The fourth lens group L4 consists of a positive lens and a negative lens, arranged in order from the object side to the image side. The fifth lens group L5 consists of a single negative meniscus lens that is convex on the image side, arranged in order from the object side to the image side. The sixth lens group L6 consists of a single positive lens.
[0072] When zooming from the wide-angle end to the telephoto end, the first lens group L1, the third lens group L3, the fourth lens group L4, and the fifth lens group L5 move toward the object. At this time, the third lens group L3 and the fifth lens group L5 move together. The second lens group L2 also moves toward the image. The sixth lens group L6 remains stationary relative to the image plane IP. When focusing from infinity to close, the fourth lens group L4 and the fifth lens group L5 move toward the image.
[0073] As is clear from the aberration diagrams in Figures 9 to 14, the zoom lens in numerical example 2 shows good correction of various aberrations.
[0074] The zoom lens L0 of Embodiment 3 (Numerical Example 3) shown in Figure 15 is composed of a first lens group L1 and a rear lens group LR, which are arranged in order from the object side to the image side and have positive refractive power. The rear lens group LR is composed of a second lens group L2 as the first negative lens group, a third lens group L3 as the first positive lens group, a fourth lens group L4 as the second negative lens group, a fifth lens group L5 as the third negative lens group, and a sixth lens group L6 as the final positive lens group, which are arranged in order from the object side to the image side.
[0075] The first lens group L1 consists of a positive lens and a cemented lens formed by a negative lens and a positive lens, arranged in order from the object side to the image side. The second lens group L2 consists of a negative lens, a positive lens, a negative lens and a negative lens, arranged in order from the object side to the image side. The third lens group L3 is a positive lens group adjacent to the second negative lens group on the object side, and consists of a cemented lens formed by a negative lens and a positive lens, a cemented lens formed by a positive lens and a negative lens, an aperture diaphragm SP, a cemented lens formed by a negative lens and a positive lens and a positive lens, arranged in order from the object side to the image side. The fourth lens group L4 consists of a positive lens and a negative lens, arranged in order from the object side to the image side. The fifth lens group L5 consists of a single negative meniscus lens that is convex on the image side, arranged in order from the object side to the image side. The sixth lens group L6 consists of a single positive lens.
[0076] When zooming from the wide-angle end to the telephoto end, the first lens group L1, the third lens group L3, the fourth lens group L4, the fifth lens group L5, and the sixth lens group L6 move toward the object, with the third lens group L3 and the fifth lens group L5 moving together. The second lens group L2 remains stationary relative to the image plane IP. When focusing from infinity to close, the fourth lens group L4 and the fifth lens group L5 move toward the image.
[0077] As is clear from the aberration diagrams in Figures 16 to 21, the zoom lens in numerical example 3 shows that various aberrations are well corrected.
[0078] The zoom lens L0 of Embodiment 4 (Numerical Example 4) shown in Figure 22 is composed of a first lens group L1 and a rear lens group LR, both with positive refractive power, arranged sequentially from the object side to the image side. The rear lens group LR is composed of a second lens group L2 as the first negative lens group, a third lens group L3 as the first positive lens group, a fourth lens group L4 as the second negative lens group, and a fifth lens group L5 as the third negative lens group and the final lens group, all arranged sequentially from the object side to the image side.
[0079] The first lens group L1 consists of a positive lens and a cemented lens formed by a negative lens and a positive lens, arranged in order from the object side to the image side. The second lens group L2 consists of a negative lens, a positive lens, a negative lens and a negative lens, arranged in order from the object side to the image side. The third lens group L3 is a positive lens group adjacent to the second negative lens group on the object side, and consists of a cemented lens formed by a negative lens and a positive lens, a cemented lens formed by a positive lens and a negative lens, an aperture diaphragm SP, a cemented lens formed by a negative lens and a positive lens, and a positive lens, arranged in order from the object side to the image side. The fourth lens group L4 consists of a positive lens and a negative lens, arranged in order from the object side to the image side. The fifth lens group L5 consists of a negative meniscus lens and a positive lens that are convex towards the image side, arranged in order from the object side to the image side.
[0080] When zooming from the wide-angle end to the telephoto end, the first lens group L1, the third lens group L3, the fourth lens group L4, and the fifth lens group L5 move toward the object, with the third lens group L3 and the fifth lens group L5 moving together. The second lens group L2 remains stationary relative to the image plane IP. When focusing from infinity to close, the fourth lens group L4 and the fifth lens group L5 move toward the image.
[0081] As is clear from the aberration diagrams in Figures 23 to 28, the zoom lens in numerical example 4 shows that various aberrations are well corrected.
[0082] The zoom lens L0 of Embodiment 5 (Numerical Example 5) shown in Figure 29 is composed of a first lens group L1 and a rear lens group LR, which are arranged in order from the object side to the image side, and have positive refractive power. The rear lens group LR is composed of a second lens group L2 as the first negative lens group, a third lens group L3 as the first positive lens group, a fourth lens group L4 as the second positive lens group, a fifth lens group L5 as the second negative lens group, a sixth lens group L6 as the third negative lens group, and a seventh lens group L7 as the final lens group with positive refractive power, which are arranged in order from the object side to the image side.
[0083] The first lens group L1 consists of a positive lens and a cemented lens formed by a negative lens and a positive lens, arranged in order from the object side to the image side. The second lens group L2 consists of a negative lens, a positive lens, a negative lens and a negative lens, arranged in order from the object side to the image side. The third lens group L3 consists of a cemented lens formed by a negative lens and a positive lens, a cemented lens formed by a positive lens and a negative lens, and an aperture diaphragm SP, arranged in order from the object side to the image side. The fourth lens group L4 is a positive lens group adjacent to the second negative lens group on the object side, and consists of a cemented lens formed by a negative lens and a positive lens, and a positive lens, arranged in order from the object side to the image side. The fifth lens group L5 consists of a positive lens and a negative lens, arranged in order from the object side to the image side. The sixth lens group L6 consists of a single negative meniscus lens that is convex on the image side, arranged in order from the object side to the image side. The seventh lens group L7 consists of a single positive lens.
[0084] When zooming from the wide-angle end to the telephoto end, the first lens group L1, the third lens group L3, the fourth lens group L4, the fifth lens group L5, and the sixth lens group L6 move toward the object, with the fourth lens group L4 and the sixth lens group L5 moving together. The second lens group L2 and the seventh lens group L7 remain stationary relative to the image plane IP. When focusing from infinity to close, the fifth lens group L5 and the sixth lens group L6 move toward the image.
[0085] As is clear from the aberration diagrams in Figures 30 to 35, the zoom lens in numerical example 5 shows that various aberrations are well corrected.
[0086] The zoom lens L0 of Embodiment 6 (Numerical Example 6) shown in Figure 36 is composed of a first lens group L1 and a rear lens group LR, which are arranged in order from the object side to the image side and have positive refractive power. The rear lens group LR is composed of a second lens group L2 as a positive lens group, a third lens group L3 as a first negative lens group, a fourth lens group L4 as a first positive lens group, a fifth lens group L5 as a second negative lens group, a sixth lens group L6 as a third negative lens group, and a seventh lens group L7 as the final lens group with positive refractive power, which are arranged in order from the object side to the image side.
[0087] The first lens group L1 consists of a positive lens and a cemented lens formed by a negative lens and a positive lens, arranged in order from the object side to the image side. The second lens group L2 consists of a single positive lens. The third lens group L3 consists of a negative lens, a positive lens, a negative lens and a negative lens, arranged in order from the object side to the image side. The fourth lens group L4 is a positive lens group adjacent to the second negative lens group on the object side, and consists of a cemented lens formed by a negative lens and a positive lens, a cemented lens formed by a positive lens and a negative lens, an aperture diaphragm SP, a cemented lens formed by a negative lens and a positive lens, and a positive lens, arranged in order from the object side to the image side. The fifth lens group L5 consists of a positive lens and a negative lens, arranged in order from the object side to the image side. The sixth lens group L6 consists of a single negative meniscus lens that is convex on the image side, arranged in order from the object side to the image side. The seventh lens group L7 consists of a single positive lens.
[0088] When zooming from the wide-angle end to the telephoto end, the first lens group L1, the fourth lens group L4, the fifth lens group L5, and the sixth lens group L6 move toward the object. At this time, the fourth lens group L4 and the sixth lens group L5 move together. The third lens group L3 moves toward the image. The second lens group L2 and the seventh lens group L7 remain stationary relative to the image plane IP. When focusing from infinity to close, the fifth lens group L5 and the sixth lens group L6 move toward the image.
[0089] As is clear from the aberration diagrams in Figures 37 to 42, the zoom lens in numerical example 6 shows that various aberrations are well corrected.
[0090] Numerical examples 1 to 6 are shown below. In each numerical example, the surface number i indicates the order of the surfaces when counted from the object side. r is the radius of curvature (mm) of the i-th surface from the object side, d is the lens thickness or air gap on the optical axis between the i-th and (i+1)-th surfaces (mm), and nd is the refractive index of the optical material at the d-line between the i-th and (i+1)-th surfaces. νd is the Abbe number with respect to the d-line of the optical material between the i-th and (i+1)-th surfaces, and θgF is the partial dispersion ratio at the g-line and F-line of the optical material between the i-th and (i+1)-th surfaces. The definitions of the Abbe number with respect to the d-line and the partial dispersion ratio at the g-line and F-line are as described above.
[0091] The focal length (mm), F-number, and half-angle of view (°) are values for the zoom lens when it is in focus at infinity. BF is the back focus, and as mentioned above, it is the air-equivalent distance from the final lens surface to the image plane (paraxial image plane) of the zoom lens. The total lens length is the distance along the optical axis from the lens surface closest to the object (front lens surface) to the final lens surface, plus the back focus BF, and corresponds to the total optical length. Note that at least one of the lens surfaces included in the zoom lens may be an aspherical surface.
[0092] [Numerical Example 1] Unit: mm Surface Data Surface Number rd nd νd θgF 1 156.072 4.74 1.48749 70.2 0.5300 2 -379.959 0.20 3 89.102 2.00 1.62004 36.3 0.5879 4 45.448 7.93 1.49700 81.5 0.5375 5 834.293 (Variable) 6 340.873 1.80 1.83481 42.7 0.5648 7 32.059 1.71 8 32.770 5.07 1.77830 23.9 0.6248 9 -75.829 0.20 10 -119.825 1.30 1.67790 55.4 0.5434 11 39.509 4.04 12 -33.889 1.20 1.95375 32.3 0.5905 13 -137.422 (variable) 14 133.011 1.20 1.92286 20.9 0.6391 15 49.654 3.73 1.90043 37.4 0.5766 16 -104.383 0.20 17 53.759 4.74 1.49700 81.5 0.5375 18 -40.183 1.30 1.80400 46.5 0.5577 19 -922.643 2.00 20 (aperture) ∞ 27.36 21 106.669 1.50 1.95375 32.3 0.5905 22 35.148 3.82 1.49700 81.5 0.5375 23 -71.963 0.20 24 42.594 2.70 1.79952 42.2 0.5672 25 297.401 (variable) 26 112.494 2.70 1.75211 25.0 0.6190 27 -81.357 3.15 28 -75.018 1.20 1.83400 37.2 0.5807 29 32.978 (Variable) 30 -30.283 1.20 1.49700 81.5 0.5375 31 -53.525 (Variable) 32 60.000 2.62 2.00100 29.1 0.5997 33 93.112 (Variable) Image plane ∞ Various data Wide angle Intermediate Telephoto focal length 72.11 135.40 292.05 F number 4.49 5.30 5.88 Half-angle of view (°) 16.70 9.08 4.24 Image height 21.64 21.64 21.64 Lens length 189.82 214.13 238.44 BF 40.89 40.89 40.89 d 5 5.00 29.31 53.61 d13 29.50 15.50 1.50 d25 2.00 5.69 2.00 d29 16.70 13.01 16.70 d31 5.91 19.91 33.92 Focusing state at object distance of 0.57m Magnification -0.164 -0.283 -0.501 d25 4.69 13.66 30.85 d29 17.93 13.30 6.02 d31 2.00 11.66 15.75 Lens Group Data Group Starting Surface Focal Length 1 1 123.72 2 6 -29.11 3 14 42.14 4 26 -54.68 5 30 -142.77 6 32 162.14 [Numerical Example 2] Unit mm Surface Data Surface Number rd nd νd θgF 1 187.178 4.45 1.48749 70.2 0.5300 2 -338.572 0.20 3 97.513 2.00 1.62004 36.3 0.5879 4 48.327 7.70 1.49700 81.5 0.5375 5 1316.674 (Variable) 6 421.888 1.80 1.80400 46.5 0.5577 7 30.239 0.80 8 31.007 5.87 1.80518 25.4 0.6161 9 -87.889 0.20 10 -173.132 1.30 1.72916 54.1 0.5448 11 43.617 3.92 12 -36.703 1.20 2.00100 29.1 0.5997 13 -115.290 (Variable) 14 129.084 1.20 1.92286 20.9 0.6391 15 63.461 3.25 1.90043 37.4 0.5766 16 -136.129 0.20 17 43.090 4.61 1.49700 81.5 0.5375 18 -54.814 1.30 1.91082 35.3 0.5834 19 1941.547 2.00 20 (aperture) ∞ 25.37 21 85.562 1.50 1.95375 32.3 0.5898 22 30.502 3.63 1.49700 81.5 0.5375 23 -86.539 0.20 24 40.615 2.45 1.91082 35.3 0.5834 25 150.826 (variable) 26 174.983 2.42 2.00069 25.5 0.6136 27 -79.758 2.18 28 -70.438 1.20 1.80610 40.9 0.5713 29 29.162 (variable) 30 -26.721 1.20 1.49700 81.5 0.5375 31 -43.150 (variable) 32 45.687 3.05 1.63930 44.9 0.5683 33 73.812 (Variable) Image plane ∞ Various data Wide-angle Intermediate Telephoto focal length 72.11 136.94 292.05 F-number 4.49 5.32 5.88 Half-angle of view (°) 16.70 8.98 4.24 Image height 21.64 21.64 21.64 Lens length 190.13 212.02 233.90 BF 41.31 41.31 41.31 d 5 5.00 31.04 57.08 d13 36.86 19.18 1.50 d25 2.00 4.81 1.05 d29 13.88 11.07 14.84 d31 5.89 19.41 32.94 Focusing state at object distance of 0.59m Magnification -0.157 -0.274 -0.502 d25 4.39 12.20 27.75 d29 15.38 11.07 6.04 d31 2.00 12.02 15.03 Lens group data group Starting plane Focal length 1 1 133.49 2 6 -34.27 3 14 41.36 4 26 -52.75 5 30 -144.72 6 32 179.94 [Numerical example 3] Unit mm Plane data plane number rd nd νd θgF 1 166.650 4.62 1.48749 70.2 0.5300 2 -365.619 0.20 3 82.598 2.00 1.63980 34.5 0.5922 4 45.817 7.86 1.49700 81.5 0.5375 5 780.601 (variable) 6 306.514 1.80 1.80400 46.5 0.5577 7 29.801 0.96 8 30.711 5.14 1.77830 23.9 0.6248 9 -76.642 0.20 10 -137.117 1.30 1.72916 54.1 0.5448 11 40.224 3.86 12 -33.778 1.20 2.00100 29.1 0.5997 13 -143.999 (variable) 14 206.074 1.20 1.92286 18.9 0.6495 15 88.537 3.26 1.95375 32.3 0.5898 16 -82.206 0.20 17 62.546 4.49 1.49700 81.5 0.5375 18 -41.140 1.30 2.00100 29.1 0.5997 19 -197.239 2.00 20 (aperture) ∞ 29.34 21 82.967 1.50 2.00100 29.1 0.5997 22 39.135 3.87 1.49700 81.5 0.5375 23 -66.208 0.20 24 48.835 2.41 1.89190 37.1 0.5780 25 165.110 (variable) 26 70.450 2.71 1.85896 22.7 0.6284 27 -162.604 3.70 28 -139.778 1.20 1.95375 32.3 0.5898 29 28.537 (Variable) 30 -32.139 1.20 1.52841 76.5 0.5396 31 -78.325 (Variable) 32 60.000 3.51 1.72342 38.0 0.5819 33 210.685 (Variable) Image plane ∞ Various data Wide-angle Intermediate Telephoto focal length 72.11 135.10 292.05 F-number 4.49 5.29 5.88 Half-angle of view (°) 16.70 9.10 4.24 Image height 21.64 21.64 21.64 Lens length 190.13 214.03 237.93 BF 39.77 44.83 49.88 d 5 5.00 28.90 52.80 d13 29.50 15.50 1.50 d25 2.00 5.80 2.00 d29 15.88 12.07 15.87 d31 6.75 15.70 24.65 Focusing state at object distance of 0.58m Magnification -0.161 -0.279 -0.501 d25 4.21 13.16 29.50 d29 18.32 12.50 6.13 d31 2.09 7.91 6.90 Lens group data group Starting plane Focal length 1 1 120.72 2 6 -28.16 3 14 42.43 4 26 -51.72 5 30 -104.08 6 32 114.84 [Numerical Example 4] Unit: mm Surface Data Surface Number rd nd νd θgF 1 168.115 3.85 1.48749 70.2 0.5300 2 -2531.670 0.20 3 90.029 2.00 1.64769 33.8 0.5938 4 50.721 7.83 1.49700 81.5 0.5375 5 -2188.880 (Variable) 6 407.904 1.80 1.77250 49.6 0.5520 7 29.544 0.78 8 30.094 5.34 1.74077 27.8 0.6095 9 -70.334 0.20 10 -131.603 1.30 1.71300 53.9 0.5459 11 46.190 3.82 12 -34.279 1.20 1.85150 40.8 0.5695 13 -570.551 (variable) 14 171.971 1.20 2.00100 29.1 0.5997 15 42.105 4.49 1.80610 40.9 0.5713 16 -65.325 0.20 17 56.572 4.75 1.49700 81.5 0.5375 18 -40.749 1.30 1.88100 40.1 0.5706 19 -195.248 2.00 20 (aperture) ∞ 29.38 21 84.991 1.50 1.91082 35.3 0.5834 22 39.428 4.05 1.49700 81.5 0.5375 23 -64.034 0.20 24 50.069 2.55 1.65160 58.5 0.5390 25 438.313 (variable) 26 62.291 2.73 1.95203 26.2 0.6101 27 -176.790 2.81 28 -124.709 1.20 1.91082 35.3 0.5834 29 26.526 (variable) 30 -36.537 1.20 1.55397 71.8 0.5389 31 -688.389 6.16 32 63.284 3.48 1.70154 41.2 0.5765 33 1736.877 (Variable) Image plane ∞ Various data Wide-angle Intermediate Telephoto focal length 72.11 135.00 292.05 F-number 4.49 5.22 5.88 Half-angle of view (°) 16.70 9.10 4.24 Image height 21.64 21.64 21.64 Lens length 189.63 216.51 243.39 BF 39.12 52.78 66.43 d 5 5.00 31.88 58.76 d13 28.82 15.16 1.50 d25 2.00 4.74 1.31 d29 17.18 14.44 17.87 Focusing state at object distance of 0.55m Magnification -0.173 -0.294 -0.503 d25 4.72 13.36 31.38 d29 21.14 14.13 6.04 Lens group data group Starting plane Focal length 1 1 132.80 2 6 -29.53 3 14 42.50 4 26 -57.16 5 30 -384.74 [Numerical example 5] Unit mm Plane data plane number rd nd νd θgF 1 153.864 4.65 1.48749 70.2 0.5300 2 -427.705 0.20 3 89.485 2.00 1.62004 36.3 0.5879 4 45.442 8.04 1.49700 81.5 0.5375 5 1155.872 (variable) 6 442.840 1.80 1.80400 46.5 0.5577 7 30.551 1.71 8 31.559 5.07 1.75211 25.0 0.6190 9 -77.145 0.20 10 -153.665 1.30 1.72916 54.1 0.5448 11 41.995 3.99 12 -33.446 1.20 1.91082 35.3 0.5834 13 -139.320 (variable) 14 210.881 1.20 1.92286 18.9 0.6495 15 87.815 3.14 1.91082 35.3 0.5834 16 -95.250 0.20 17 48.039 4.80 1.49700 81.5 0.5375 18 -43.866 1.30 1.91082 35.3 0.5834 19 -341.976 2.00 20 (aperture) ∞ (variable) 21 126.586 1.50 1.95375 32.3 0.5905 22 36.579 3.93 1.49700 81.5 0.5375 23 -66.677 0.20 24 44.553 2.63 1.85150 40.8 0.5695 25 281.698 (variable) 26 118.880 2.65 1.80518 25.4 0.6161 27 -85.814 3.31 28 -74.157 1.20 1.83400 37.2 0.5807 29 34.099 (variable) 30 -31.650 1.20 1.49700 81.5 0.5375 31 -58.815 (variable) 32 60.000 2.54 2.00100 29.1 0.5997 33 90.269 (Variable) Image plane ∞ Various data Wide-angle Intermediate Telephoto focal length 72.11 135.43 292.05 F-number 4.49 5.30 5.88 Half angle of view (°) 16.70 9.08 4.24 Image height 21.64 21.64 21.64 Lens length 190.13 214.47 238.80 BF 40.92 40.92 40.92 d 5 5.00 29.34 53.67 d13 29.14 15.32 1.50 d20 27.09 26.91 26.73 d25 2.00 5.82 2.00 d29 17.93 14.10 17.92 d31 6.09 20.09 34.10 Focusing state at object distance of 0.57m Magnification -0.165 -0.284 -0.503 d25 4.71 14.01 32.06 d29 19.31 14.21 5.90 d31 2.00 11.80 16.07 Lens group data Group Starting plane Focal length 1 1 123.30 2 6 -28.89 3 14 56.40 4 21 52.87 5 26 -57.80 6 30 -139.93 7 32 171.55 [Numerical Example 6] Unit: mm Surface Data Surface Number rd nd νd θgF 1 91.052 2.00 1.95375 32.3 0.5898 2 57.888 8.62 1.59282 68.6 0.5458 3 -463.930 (Variable) 4 64.039 3.91 1.59282 68.6 0.5458 5 -1273.561 (Variable) 6 -312.989 1.80 1.81600 46.6 0.5568 7 32.148 2.82 8 33.572 4.89 1.75211 25.0 0.6190 9 -81.887 0.20 10 -304.051 1.30 1.76385 48.5 0.5589 11 37.143 3.82 12 -33.261 1.20 1.88300 40.8 0.5667 13 -226.195 (variable) 14 454.732 1.20 1.92286 18.9 0.6495 15 171.797 3.12 1.95375 32.3 0.5905 16 -66.177 0.20 17 59.747 4.65 1.48749 70.2 0.5300 18 -40.458 1.30 2.00069 25.5 0.6136 19 -193.139 2.00 20 (aperture) ∞ 28.48 21 123.431 1.50 1.85451 25.2 0.6102 22 39.619 3.73 1.52841 76.5 0.5396 23 -77.551 0.20 24 58.857 2.48 1.91082 35.3 0.5834 25 3121.817 (variable) 26 62.589 2.73 1.89286 20.4 0.6393 27 -170.705 2.40 28 -144.408 1.20 1.95375 32.3 0.5898 29 26.903 (Variable) 30 -37.330 1.20 1.49700 81.5 0.5375 31 -98.667 (Variable) 32 43.518 3.85 1.48749 70.2 0.5300 33 101.326 (Variable) Image plane ∞ Various data Wide-angle Intermediate Telephoto focal length 72.11 135.00 292.05 F-number 4.49 5.07 5.88 Half-angle of view (°) 16.70 9.10 4.24 Image height 21.64 21.64 21.64 Lens length 189.82 217.83 245.83 BF 40.65 40.65 40.65 d 3 1.00 29.00 57.00 d 5 2.00 7.00 12.00 d13 29.50 15.50 1.50 d25 2.00 5.45 1.02 d29 17.32 13.87 18.30 d31 6.55 15.55 24.55 Focusing state at object distance of 0.53m Magnification -0.182 -0.301 -0.501 d25 4.35 13.40 29.65 d29 19.52 13.20 7.67 d31 2.00 8.27 6.55 Lens Group Data Group Starting Plane Focal Length 1 1 180.47 2 4 102.96 3 6 -22.18 4 14 41.51 5 26 -51.13 6 30 -121.62 7 32 153.13 Table 1 summarizes the values related to equations (1) to (9) in numerical examples 1 to 6. All values in Table 1 are values at the d line as the reference wavelength. The zoom lenses in each numerical example satisfy all the conditions of equations (1) to (9).
[0093]
[0094] [Imaging Device] Figure 44 shows an imaging device (digital still camera) 10 equipped with a zoom lens of each embodiment. The imaging device 10 has a camera body 11 and a lens device 12 that can be attached to or removed from the camera body 11. The lens device 12 includes a zoom lens of any of Embodiments 1 to 6 as an imaging optical system.
[0095] 13 is an image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor, which is built into the camera body 11 and converts the optical image formed by the lens device 12 into photoelectric data (that is, it captures an image of the subject through the zoom lens).
[0096] The camera body 11 may be a single-lens reflex camera with a quick-turn mirror, or a mirrorless camera without a quick-turn mirror. The imaging device may also be a lens-integrated imaging device in which the camera body and lens device are configured as one unit. The zoom lens in each embodiment can be used not only in digital still cameras, but also as the imaging optical system of various imaging devices such as broadcast cameras, silver halide film cameras, and surveillance cameras.
[0097] Thus, by using the zoom lenses of each embodiment in the imaging device, an imaging device can be realized that can produce good image captures across all object distances from infinity to the nearest object with a high zoom ratio.
[0098] The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention.
Claims
1. A zoom lens in which the spacing between adjacent lens groups changes during zooming, having a first lens group with positive refractive power positioned closest to the object, and a third negative lens group, a second negative lens group, and a third negative lens group positioned closer to the image than the first lens group, with negative refractive power, and during focusing from infinity to near, the second and third negative lens groups move toward the image side. A zoom lens characterized by satisfying the following conditions, where fw is the focal length at the wide-angle end of the zoom lens, ft is the focal length at the telephoto end of the zoom lens, Skw is the air-equivalent distance on the optical axis from the final lens surface closest to the image to the image plane when the zoom lens is at the wide-angle end and in focus on an object at infinity, OVLt is the distance on the optical axis from the lens surface closest to the object to the final lens surface plus the air-equivalent distance on the optical axis from the final lens surface to the image plane when the zoom lens is at the telephoto end and in focus on an object at infinity, fn2 is the focal length of the second negative lens group, and fn3 is the focal length of the third negative lens group: 0.33 ≤ Skw / fw ≤ 1.00 0.50 ≤ OVLt / ft ≤ 0.85 1.3 ≤ fn3 / fn2 ≤ 10.0 2. The zoom lens according to claim 1, characterized in that when the focal length of the first lens group is f1, the condition 1.0 ≤ |f1 / (fn2)| ≤ 3.6 is satisfied.
3. The zoom lens according to claim 1 or 2, characterized in that it has at least one group of lenses with positive refractive power positioned between the first negative lens group and the second negative lens group.
4. A zoom lens according to any one of claims 1 to 3, wherein the first negative lens group has a first positive lens group as a group of lenses with positive refractive power adjacent to the first negative lens group on the image side, and when the focal length of the first lens group is f1 and the focal length of the first positive lens group is fp1, the condition 1.0 ≤ f1 / fp1 ≤ 4.6 is satisfied.
5. The zoom lens according to any one of claims 1 to 4, characterized in that the second negative lens group is composed of two lenses, a positive lens and a negative lens, arranged in order from the object side to the image side.
6. The zoom lens according to any one of claims 1 to 5, characterized in that when νdn is the Abbe number with respect to the d line of a negative lens included in the third negative lens group, and θgFn is the partial dispersion ratio between the g line and the F line of the negative lens, the following conditions are satisfied: 42 ≤ νdn ≤ 100 - 0.001682 × νdn + 0.6438 ≤ θgFn ≤ 0.
55.
7. The zoom lens according to any one of claims 1 to 6, characterized in that, when the radii of curvature of the object-side and image-side faces of the negative lenses included in the third negative lens group are Rnf and Rnr, respectively, the condition -10.0 ≤ (Rnf + Rnr) / (Rnf - Rnr) ≤ -1.0 is satisfied.
8. The zoom lens according to any one of claims 1 to 7, characterized in that the third negative lens group is composed of a single negative lens.
9. The zoom lens according to any one of claims 1 to 8, characterized in that the lens group with positive refractive power adjacent to the second negative lens group on the object side and the third negative lens group move together as a single unit during zooming.
10. The zoom lens according to any one of claims 1 to 9, characterized in that the first lens group, the first negative lens group, and the first positive lens group with positive refractive power are arranged in this order from the object side to the image side.
11. The zoom lens according to any one of claims 1 to 10, characterized in that the first negative lens group is immovable during zooming.
12. The zoom lens according to claim 1, characterized in that the third negative lens group is adjacent to the second negative lens group on the image side.
13. The zoom lens according to any one of claims 1 to 12, characterized in that a final lens group with positive refractive power is provided between the third negative lens group and the image plane.
14. The zoom lens according to claim 13, characterized in that the final lens group remains stationary during zooming.
15. The zoom lens according to any one of claims 1 to 13, characterized in that it is composed of a first lens group, a second lens group as the first negative lens group, a third lens group as the first positive lens group with positive refractive power, a fourth lens group as the second negative lens group, a fifth lens group as the third negative lens group, and a sixth lens group as the final lens group with positive refractive power, arranged in order from the object side to the image side.
16. The zoom lens according to any one of claims 1 to 12, characterized in that it is composed of the first lens group, the second lens group as the first negative lens group, the third lens group as the first positive lens group with positive refractive power, the fourth lens group as the second negative lens group, and the fifth lens group as the third negative lens group and the final lens group, arranged in order from the object side to the image side.
17. The zoom lens according to any one of claims 1 to 14, characterized in that it is composed of the first lens group, the second lens group as the first negative lens group, the third lens group as the first positive lens group with positive refractive power, the fourth lens group with positive refractive power, the fifth lens group as the second negative lens group, the sixth lens group as the third negative lens group, and the seventh lens group as the final lens group with positive refractive power, arranged in order from the object side to the image side.
18. The zoom lens according to any one of claims 1 to 9 and 11 to 14, characterized in that it is composed of a first lens group, a second lens group with positive refractive power, a third lens group as the first negative lens group, a fourth lens group as the first positive lens group with positive refractive power, a fifth lens group as the second negative lens group, a sixth lens group as the third negative lens group, and a seventh lens group as the final lens group with positive refractive power, arranged in order from the object side to the image side.
19. A zoom lens in which the spacing between adjacent lens groups changes during zooming, comprising a first lens group with positive refractive power positioned closest to the object, and a third negative lens group, a second negative lens group, and a third negative lens group positioned closer to the image than the first lens group, characterized in that the second and third negative lens groups move toward the image side during focusing from infinity to near.
20. An imaging device characterized by having a zoom lens according to any one of claims 1 to 19 and an image sensor that captures an image of a subject through the zoom lens.