Optical system and imaging apparatus

Abstract

To make an optical system having a tilt function small in size and light in weight.SOLUTION: The optical system L0 includes, in order from the object side to the image side, a first eccentric lens group L4 and a second eccentric lens group L5 that are movable so as to be eccentric with respect to a reference optical axis. A condition of 0.4 ≤ tan θ / tan ω ≤ 1.0 is satisfied, where ω is a half angle of view of the optical system in a first state in which the first and second eccentric lens groups are not moved with respect to the reference optical axis, and θ is an angle formed with respect to the reference optical axis when a principal ray that is incident on the optical system from outside the reference optical axis and reaches a center of an image plane is incident on the optical system in a second state in which the first and second eccentric lens groups are moved with respect to the reference optical axis.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system having a tilt function. [Background technology]

[0002] Some optical systems used for imaging have a tilt function that allows for shifting and the like. Summary of the Invention [Problem to be solved by the invention]

[0003] An optical system having a tilt function is required to be small, lightweight, and have good optical performance. [Means for solving the problem]

[0004] An optical system according to one aspect of the present invention includes, in this order from the object side to the image side, a first decentered lens group and a second decentered lens group that are movable so as to be decentered relative to a reference optical axis. When the half angle of view of the optical system in a first state in which the first and second decentered lens groups are not moved relative to the reference optical axis is ω, and when the first and second decentered lens groups are moved relative to the reference optical axis in a second state in which the first and second decentered lens groups have moved relative to the reference optical axis, the angle that a chief ray makes with the reference optical axis when entering the optical system and reaching the center of the image plane is θ, 0.4≦tan θ / tan ω≦1.0 An optical system characterized by satisfying the following conditions:

[0005] Another aspect of the present invention provides an optical system having, in this order from the object side to the image side, a first decentered lens group and a second decentered lens group that are movable so as to be decentered relative to a reference optical axis. Each of the first and second decentered lens groups includes two or more lenses. An imaging device including each of the above optical systems also constitutes another aspect of the present invention. [Brief explanation of the drawings]

[0006] [Figure 1]1A is a cross-sectional view of the optical system of Example 1 in a normal state and a shifted state. FIG. [Figure 2] FIG. 4 is a longitudinal aberration diagram of the optical system of Example 1 in a normal state. [Figure 3] 4A and 4B are lateral aberration diagrams of the optical system of Example 1 in a normal state and a shifted state, respectively. [Figure 4] 10A is a cross-sectional view of the optical system of Example 2 in a normal state and a shifted state. FIG. [Figure 5] FIG. 10 is a longitudinal aberration diagram of the optical system of Example 2 in a normal state. [Figure 6] 10A and 10B are lateral aberration diagrams of the optical system of Example 2 in a normal state and a shifted state, respectively. [Figure 7] 10A is a cross-sectional view of the optical system of Example 3 in a normal state and a shifted state. FIG. [Figure 8] FIG. 10 is a longitudinal aberration diagram of the optical system of Example 3 in a normal state. [Figure 9] 10A and 10B are lateral aberration diagrams of the optical system of Example 3 in a normal state and a shifted state, respectively. [Figure 10] 10A is a cross-sectional view of the optical system of Example 4 in a normal state and a shifted state. FIG. [Figure 11] FIG. 10 is a longitudinal aberration diagram of the optical system of Example 4 in a normal state. [Figure 12] 10A and 10B are lateral aberration diagrams of the optical system of Example 4 in a normal state and a shifted state, respectively. [Figure 13] 10A is a cross-sectional view of the optical system of Example 5 in a normal state and a shifted state. FIG. [Figure 14] FIG. 10 is a longitudinal aberration diagram of the optical system of Example 5 in a normal state. [Figure 15] 10A and 10B are lateral aberration diagrams of the optical system of Example 5 in a normal state and a shifted state, respectively. [Figure 16] 10A is a cross-sectional view of the optical system of Example 6 in a normal state and a shifted state. FIG. [Figure 17] FIG. 13 is a longitudinal aberration diagram of the optical system of Example 6 in a normal state. [Figure 18] 10A and 10B are lateral aberration diagrams of the optical system of Example 6 in a normal state and a shifted state, respectively. [Figure 19]10A is a cross-sectional view of the optical system of Example 7 in a normal state and a shifted state. FIG. [Figure 20] FIG. 13 is a longitudinal aberration diagram of the optical system of Example 7 in a normal state. [Figure 21] 10A and 10B are lateral aberration diagrams of the optical system of Example 7 in a normal state and a shifted state, respectively. [Figure 22] FIG. 1 is a schematic diagram of an imaging device equipped with the optical system of Examples 1 to 7. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, examples of the present invention will be described with reference to the drawings. First, before specifically describing the optical systems of Examples 1 to 7, matters common to all Examples will be described.

[0008] The optical system of each embodiment is used in various imaging devices such as digital video cameras, digital cameras, television cameras, silver halide film cameras, and surveillance cameras. The optical system of each embodiment has a shift function that moves (shifts) a subject image on the image plane, and is small, lightweight, and has good optical performance. In the following description, a state in which the shift function is not used is referred to as a normal state (first state), and a state in which the subject image is shifted using the shift function is referred to as a shift state (second state).

[0009] FIGS. 1A, 4A, 7A, 10A, 13A, 16A, and 19A show cross sections of the optical systems of Examples 1 to 7 in a normal state and in a state where an object at infinity is focused (hereinafter referred to as an infinity focused state), respectively. FIGS. 1B, 4B, 7B, 10B, 13B, 16B, and 19B show cross sections of the optical systems of Examples 1 to 7 in a shifted state and in a state where an object at infinity is focused, respectively. In each figure, the left side is the object side (front side), and the right side is the image side (rear side). In each figure (A), the optical axis of the optical system in a normal state is shown by a dashed line. This optical axis is the optical axis that serves as the reference for the shift function (reference optical axis; hereinafter, simply referred to as the optical axis). The dashed line shown in each figure (B) is the line connecting the centers of each lens in the shifted state.

[0010] The optical system of each embodiment has multiple lens groups Li (i = 1, 2, 3, ... from the object side to the image side). A lens group is a group of one or more lenses that move or remain stationary in the direction in which the optical axis extends (optical axis direction) during zooming and focusing, and move or remain stationary relative to the optical axis during shifting. In other words, the relative positions between the lens groups (the spacing along the optical axis and the position in the direction perpendicular to the optical axis) change during zooming, focusing, and shifting. The lens groups may include an aperture stop SP that determines (limits) the light beam at the maximum F-number (Fno).

[0011] The image plane IP is provided with an imaging surface of an imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor, or a film surface (photosensitive surface) of a silver halide film. Although not shown, optical blocks such as an optical filter, a face plate, a low-pass filter, and an infrared cut filter may be provided on the object side of the image plane IP.

[0012] The shift function of the optical system of each embodiment will now be described. The shift function decenters some lenses in the optical system relative to the other lenses, thereby achieving an image shift effect that shifts the position of the subject image formed on the image plane (i.e., the composition). While image stabilization (image shake correction) decenters the lenses relative to the optical axis to suppress image shift, the shift function, which shifts the composition, decenters the lenses to increase image shift. Therefore, in the optical system of each embodiment, a shiftable decentered lens group A (first decentered lens group) and a shifter lens group B (second decentered lens group) are appropriately positioned to correct various aberrations caused by lens shift. These two decentered lens groups A and B mutually correct various aberrations caused by decentering while maintaining image shift. This achieves an optical system that achieves a large image shift effect while effectively correcting various aberrations.

[0013] The optical system of each embodiment is configured with a front group having a strong negative refractive power and a rear group having a positive refractive power, which is a so-called retrofocus type refractive power arrangement, thereby realizing a compact size and a wide angle of view.

[0014] The optical system of each embodiment has two decentered lens groups that move (shift) in a direction including a component perpendicular to the optical axis or move (rotate) in a direction including a component tilted relative to the optical axis.

[0015] The optical system of each embodiment is an inner focus type optical system in which, when focusing from infinity to a close distance, the lens group closest to the image side of the lens group closest to the object side of the optical system is driven in the direction of the optical axis.

[0016] The conditions and configurations that the optical system of each example should preferably satisfy are described below. The optical system of each example should preferably satisfy at least one of the conditions in the following expressions (1) to (6) or at least one of the following configurations.

[0017] 1A and 1B, the optical system of each embodiment has a half angle of view (°) in the normal state as ω, and a principal ray that enters the optical system from off the optical axis in the shifted state (passes through the center of the aperture stop SP) and reaches the center of the image plane IP as an angle formed with the optical axis when entering the optical system. In this case, it is preferable to satisfy the condition of the following formula (1):

[0018] 0.4≦tan θ / tan ω ≦1.0 (1) The condition of formula (1) is a condition related to the image shift effect that shifts the subject image. If tan θ / tan ω is below the lower limit of formula (1), the amount of composition shift obtained will be too small, and a sufficient image shift effect will not be obtained, which is undesirable. If tan θ / tan ω is above the upper limit of formula (1), it will be difficult to correct the various aberrations that occur due to decentering of the decentered lens group, which is also undesirable.

[0019] It is more preferable that the lower limit of the formula (1) is 0.45, 0.50, or 0.53, and it is more preferable that the upper limit of the formula (1) is 0.9, 0.8, 0.7, or 0.6.

[0020] In the optical system of each embodiment, it is preferable that the condition of the following formula (2) be satisfied, where Ma is the amount of decentering (amount of movement) of the decentered lens unit A from the normal state, Sa is the decentering sensitivity of the decentered lens unit A, Mb is the amount of decentering of the decentered lens unit B from the normal state, Sb is the decentering sensitivity of the decentered lens unit B, and f is the focal length of the entire optical system in the normal state.

[0021] 0.4≦|(Ma×Sa+Mb×Sb) / (f×tanω)|≦1.0 (2) The decentering sensitivity in equation (2) is defined as follows: The image shift amount on the image surface is, in other words, the amount of movement of the central ray on the image surface in the shifted state from the normal state.

[0022] When the decentered lens group shifts in a direction that includes a component perpendicular to the optical axis (hereinafter simply referred to as the perpendicular direction) Decentration sensitivity [mm / mm] = Image shift on the image plane [mm] / Decentration in the orthogonal direction [mm] When the decentered lens group rotates in a direction that includes a tilt component relative to the optical axis (hereinafter simply referred to as the tilt direction) Decentration sensitivity [mm / °] = Image shift amount on the image plane [mm] / Decentration amount in the tilt direction [°] Furthermore, the sign of the decentering amount of the decentered lens group is + for the upward direction and - for the downward direction when shifting in the perpendicular direction, and when rotating in the tilting direction, + indicates the direction in which the top of the drawing tilts toward the object side and - indicates the direction in which it tilts toward the image side when rotating in the tilting direction.

[0023] The condition of formula (2) is a condition regarding the image shift effect caused by the decentered lens group. If |(Ma×Sa+Mb×Sb) / (f×tanω)| falls below the lower limit of formula (2), the amount of composition shift obtained will be too small, and a sufficient image shift effect will not be obtained, which is undesirable. If |(Ma×Sa+Mb×Sb) / (f×tanω)| exceeds the upper limit of formula (2), it will become difficult to correct the various aberrations caused by the decentering of the decentered lens group, which is undesirable.

[0024] It is more preferable that the lower limit of the formula (2) is 0.42, 0.45, 0.48, or 0.49, and it is more preferable that the upper limit of the formula (2) is 0.9, 0.8, 0.7, 0.6, or 0.55.

[0025] In the optical systems of each embodiment, it is preferable that each decentered lens group includes two or more lenses. This makes it possible to reduce aberration fluctuations due to decentering of each decentered lens group. It is also preferable that each decentered lens group includes a cemented lens formed by cementing together positive-negative or negative-positive lenses. This makes it possible to effectively correct chromatic aberration.

[0026] It is preferable that both decentered lens groups A and B rotate in the tilt direction as in the optical systems of Examples 4 to 6. This makes it possible to prevent the optical system from becoming too large in the radial direction.

[0027] In the optical systems of Examples 1 and 3 to 6, the length on the optical axis from the lens surface closest to the object in the normal state of the decentered lens unit A that can be rotated in the tilt direction to the lens surface closest to the image in the decentered lens unit A (lens unit length) is defined as La, and the length on the optical axis from the lens surface closest to the object in the optical system in the normal state to the image plane (total optical length) is defined as TL. In this case, it is preferable to satisfy the condition of the following formula (3):

[0028] 0.05≦La / TL≦0.30 (3) The condition of formula (3) indicates the appropriate relationship between the lens group length La of the rotating decentered lens group A and the total optical length TL of the optical system. If La / TL is below the lower limit of formula (3), the lens group length of the decentered lens group A becomes too short, which undesirably reduces the decentering sensitivity in the shift state. If La / TL is above the upper limit of formula (3), the decentered lens group A becomes too large, which is undesirable.

[0029] It is more preferable that the lower limit of the formula (3) is 0.06, 0.07, or 0.08, and it is more preferable that the upper limit of the formula (3) is 0.27, 0.25, 0.23, 0.20, or 0.16.

[0030] In the optical systems of Examples 2 and 4 to 6, when the length on the optical axis (lens group length) from the lens surface of decentered lens group B that is rotatable in the tilt direction that is closest to the object in the normal state to the lens surface of decentered lens group B that is closest to the image is taken as Lb, it is preferable that the condition of the following formula (4) be satisfied:

[0031] 0.05≦Lb / TL≦0.30 (4) The condition of formula (4) indicates the appropriate relationship between the lens group length Lb of the rotating decentered lens group B and the total optical length TL of the optical system. If Lb / TL is below the lower limit of formula (4), the lens group length of the decentered lens group B becomes too short, which undesirably reduces the decentering sensitivity in the shift state. If Lb / TL is above the upper limit of formula (4), the decentered lens group B becomes too large, which undesirably.

[0032] It is more preferable that the lower limit of the formula (4) is 0.06, 0.08, 1.00, or 1.14, and it is more preferable that the upper limit of the formula (4) is 0.27, 0.25, 0.23, 0.20, or 0.16.

[0033] In the optical system of each embodiment, it is preferable to satisfy the condition of the following formula (5).

[0034] 5.0≦TL / f≦15.0 (5) The condition of formula (5) indicates the appropriate relationship between the focal length f of the entire optical system and the total optical length TL. If TL / f is below the lower limit of formula (5), the refractive power of each lens group in the optical system becomes too large, making it difficult to maintain optical performance, which is undesirable. If TL / f is above the upper limit of formula (5), the optical system becomes large, which is undesirable.

[0035] It is more preferable that the lower limit of the formula (5) is 6.0, 7.0, 8.0 or 8.3, and it is more preferable that the upper limit of the formula (5) is 14.0, 12.0, 10.0 or 9.0.

[0036] In the optical system of each embodiment, when the back focus in a normal state (the air-equivalent distance on the optical axis from the lens surface closest to the image side of the optical system to the image plane) is Sk, it is preferable to satisfy the condition of the following equation (6):

[0037] 0.7≦Sk / f≦1.2 (6) The condition of formula (6) indicates the appropriate relationship between the focal length f of the optical system and the back focal length Sk. If Sk / f is below the lower limit of formula (6), the back focal length becomes too short, making it difficult to ensure the flange focal length (the distance from the lens mount surface of the imaging device to the image plane), which is undesirable. If Sk / f is above the upper limit of formula (6), the back focal length becomes too long, which increases the size of the optical system, which is undesirable.

[0038] It is more preferable that the lower limit of the formula (6) is 0.75, 0.80, or 0.83, and it is more preferable that the upper limit of the formula (6) is 1.1, 1.0, or 0.98.

[0039] The optical systems of Examples 1 to 7 will be specifically described below. After Example 7, Numerical Examples 1 to 7 corresponding to Examples 1 to 7, respectively, are shown. [Example]

[0040] The optical system L0 of Example 1 (Numerical Example 1) shown in FIGS. 1(a) and 1(b) is composed of, arranged in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 with positive refractive power, and a sixth lens group L6 with negative refractive power.

[0041] In the shift state, the fourth lens group L4 as the decentered lens group A rotates in the tilt direction relative to the normal state, and the fifth lens group L5 as the decentered lens group B shifts in the orthogonal direction. Furthermore, the second lens group L2 moves toward the object side.

[0042] During focusing from infinity to a close distance, the second lens unit L2 moves toward the image side.

[0043] FIG. 2 shows longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the optical system of Numerical Example 1 in a normal state and focused at infinity. In the spherical aberration diagram, Fno indicates the F-number, the solid line indicates spherical aberration at the d-line (wavelength 587.6 nm), and the two-dot chain line indicates spherical aberration at the g-line (wavelength 435.8 nm). In the astigmatism diagram, the solid line S indicates astigmatism at the sagittal image plane, and the dashed line M indicates astigmatism at the meridional image plane. The distortion diagram shows distortion at the d-line. The chromatic aberration diagram shows chromatic aberration of magnification at the g-line. ω is the half angle of view (°). 3A and 3B respectively show the lateral aberrations at the d-line, g-line, F-line (486.1 nm), and C-line (656.3 nm) in the normal state, the shifted state, and the infinity-focused state in the optical system of Numerical Example 1. The explanations for these aberration diagrams are the same for the aberration diagrams of the other Numerical Examples described later. [Example]

[0044] The optical system L0 of Example 2 (Numerical Example 2) shown in FIGS. 4(a) and 4(b) is composed of, arranged in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 with positive refractive power, and a sixth lens group L6 with negative refractive power.

[0045] In the shift state, the fourth lens group L4 as the decentered lens group A shifts in the orthogonal direction, and the fifth lens group L5 as the decentered lens group B rotates in the tilt direction, relative to the normal state. Furthermore, the second lens group L2 moves toward the object side.

[0046] During focusing from infinity to a close distance, the second lens unit L2 moves toward the image side.

[0047] Fig. 5 shows longitudinal aberrations in the normal state and in the infinity-focused state of the optical system of Numerical Example 2. Fig. 6(A) and Fig. 6(B) show transverse aberrations at the d-line, g-line, F-line, and C-line in the normal state and shift state and in the infinity-focused state of the optical system of Numerical Example 2, respectively. [Example]

[0048] The optical system L0 of Example 3 (Numerical Example 3) shown in Figures 7(a) and (b) is composed of, arranged in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 with positive refractive power, a sixth lens group L6 with negative refractive power, and a seventh lens group L7 with negative refractive power.

[0049] In the shift state, the fourth lens group L4 as the decentered lens group A rotates in the tilt direction relative to the normal state, and the sixth lens group L6 as the decentered lens group B shifts in the orthogonal direction. Furthermore, the second lens group L2 moves toward the image side.

[0050] During focusing from infinity to a close distance, the second lens unit L2 moves toward the image side.

[0051] Fig. 8 shows longitudinal aberrations in the normal state and in the infinity-focused state of the optical system of Numerical Example 3. Fig. 9(A) and Fig. 9(B) show transverse aberrations at the d-line, g-line, F-line, and C-line in the normal state and shift state and in the infinity-focused state of the optical system of Numerical Example 3, respectively. [Example]

[0052] The optical system L0 of Example 4 (Numerical Example 4) shown in Figures 10(a) and (b) is composed of, arranged in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 with positive refractive power, and a sixth lens group L6 with negative refractive power.

[0053] In the shift state, the fourth lens group L4 serving as the decentered lens group A rotates in a tilting direction relative to the normal state, and the fifth lens group L5 serving as the decentered lens group B rotates in a tilting direction on the same side as the fourth lens group L4. Furthermore, the second lens group L2 moves toward the object side.

[0054] During focusing from infinity to a close distance, the second lens unit L2 moves toward the image side.

[0055] Fig. 11 shows longitudinal aberrations in the normal state and in the infinity-focused state of the optical system of Numerical Example 4. Fig. 12(A) and (B) show transverse aberrations at the d-line, g-line, F-line, and C-line of the optical system of Numerical Example 4 in the normal state, shift state, and in the infinity-focused state, respectively. [Example]

[0056] The optical system L0 of Example 5 (Numerical Example 5) shown in Figures 13(a) and (b) is composed of, arranged in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 with positive refractive power, and a sixth lens group L6 with negative refractive power.

[0057] In the shift state, the second lens group L2 serving as the decentered lens group A rotates in a tilting direction relative to the normal state, and the fifth lens group L5 serving as the decentered lens group B rotates in a tilting direction opposite to the second lens group L2. Furthermore, the third lens group L3 moves toward the object side.

[0058] During focusing from infinity to a close distance, the third lens unit L3 moves toward the image side.

[0059] Fig. 14 shows longitudinal aberrations in the normal state and in the infinity-focused state of the optical system of Numerical Example 5. Fig. 15(A) and (B) show transverse aberrations at the d-line, g-line, F-line, and C-line of the optical system of Numerical Example 5 in the normal state, shift state, and in the infinity-focused state, respectively. [Example]

[0060] The optical system L0 of Example 6 (Numerical Example 6) shown in Figures 16(a) and (b) is composed of, arranged in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 with negative refractive power, and a sixth lens group L6 with negative refractive power.

[0061] In the shift state, the second lens group L2 serving as the decentered lens group A rotates in a tilt direction relative to the normal state, and the fourth lens group L4 serving as the decentered lens group B rotates in a tilt direction opposite to the second lens group L2. Furthermore, the fifth lens group L5 moves toward the object side.

[0062] During focusing from infinity to a close distance, the fifth lens unit L5 moves toward the image side.

[0063] Fig. 17 shows longitudinal aberrations in the normal state and in the infinity-focused state of the optical system of Numerical Example 6. Also, Figs. 18(A) and 18(B) show transverse aberrations at the d-line, g-line, F-line, and C-line of the optical system of Numerical Example 6 in the normal state, shift state, and in the infinity-focused state, respectively. [Example]

[0064] The optical system L0 of Example 7 (Numerical Example 7) shown in Figures 19(a) and (b) is composed of, arranged in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 with positive refractive power, a sixth lens group L6 with negative refractive power, and a seventh lens group L7 with positive refractive power.

[0065] In the shifted state, the fourth lens group L4 serving as the decentered lens group A shifts in the orthogonal direction relative to the normal state, and the sixth lens group L6 serving as the decentered lens group B shifts in the orthogonal direction on the side opposite to the fourth lens group L4. Furthermore, the second lens group L2 moves toward the image side.

[0066] During focusing from infinity to a close distance, the second lens unit L2 moves toward the image side.

[0067] Fig. 20 shows longitudinal aberrations in the normal state and in the infinity-focused state of the optical system of Numerical Example 7. Also, Fig. 21(A) and (B) show transverse aberrations at the d-line, g-line, F-line, and C-line of the optical system of Numerical Example 7 in the normal state, shift state, and in the infinity-focused state, respectively.

[0068] Numerical Examples 1 to 7 are shown below. Each numerical example shows various values ​​under normal conditions. In each numerical example, surface number i indicates the order of the optical surface from the object side. r is the radius of curvature (mm) of the i-th surface, and d is the distance (mm) on the optical axis between the i-th surface and the (i+1)-th surface. nd is the refractive index of the medium (optical element) between the i-th surface and the (i+1)-th surface with respect to the d-line. νd is the Abbe number based on the d-line of the optical material between the i-th surface and the (i+1)-th surface. The Abbe number based on the d-line, νd, is expressed as νd = (Nd-1) / (NF-NC), where Nd, NF, and NC are the refractive indices at the Fraunhofer d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm). The effective diameter is the radius (mm) of the area of ​​the i-th lens surface through which light rays contributing to image formation pass. The effective diameter indicates the effective diameter required in the normal state and the shift state.

[0069] Sk represents the back focal length mentioned above. The back focal length is the distance on the optical axis from the final surface of the optical system (the lens surface closest to the image) to the paraxial image plane, expressed as an air-equivalent length. The total lens length is the distance on the optical axis from the foreground surface of the optical system (the lens surface closest to the object) to the final surface plus the back focal length, and corresponds to the total optical length of the entire optical system mentioned above.

[0070] In each numerical example, the focal length (mm), F-number, and half angle of view (°) are all values ​​when the lens is focused at infinity.

[0071] An "*" next to a surface number indicates that the surface has an aspherical shape. The aspherical shape is expressed by the following formula, where x is the displacement from the vertex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, the direction of light travel is positive, R is the paraxial radius of curvature, K is the conic constant, and A4 to A10 are aspherical coefficients. The conic constant and the aspherical coefficients "e±Z" are expressed as x10 ±Z means.

[0072] x=(h 2 / R) / [1+√{1-(1+K)(h / R) 2}] +A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 Numerical values ​​relating to the above-mentioned formulas (1) to (6) in Numerical Examples 1 to 7 are summarized in Table 1. Note that each value is based on the d-line wavelength. (Numerical Example 1) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 51.484 3.50 1.76385 48.5 66.77 2 24.505 4.08 45.61 3* 37.431 3.50 1.58313 59.4 44.45 4* 16.924 9.62 36.39 5 54.274 2.00 1.53775 74.7 34.62 6 16.271 8.02 25.44 7 -71.242 1.20 1.49700 81.5 24.23 8 15.842 0.50 20.29 9 15.838 6.98 1.64769 33.8 20.19 10 -53.329 0.81 18.29 11 -32.804 1.20 2.05090 26.9 17.41 12 -258.347 (variable) 16.62 13 29.936 1.00 2.00069 25.5 15.19 14 13.309 5.00 1.69895 30.1 13.85 15 -74.614 (variable) 12.18 16 43.590 3.00 1.69895 30.1 12.12 17 -106.025 2.00 12.12 18 (Aperture) ∞ 3.00 11.93 19 693.528 1.20 1.91082 35.2 11.67 20 21.101 3.19 1.49700 81.5 11.57 21 -48.232 (variable) 11.75 22 497.332 10.00 1.49700 81.5 26.02 23 -16.893 1.20 1.81600 46.6 28.59 24 -30.396 1.26 34.45 25 -55.676 10.00 1.59522 67.7 39.60 26 -28.074 (variable) 43.75 27 92.247 10.00 1.49700 81.5 50.06 28 -71.282 1.20 1.91082 35.2 49.77 29 239.071 0.50 50.15 30 69.754 10.00 1.49700 81.5 51.36 31* -73.446 (variable) 51.19 32 -127.608 7.23 1.86966 20.0 32.55 33 -24.277 1.50 2.05090 26.9 32.58 34 -71.891 3.65 33.56 35 -30.006 1.50 2.00069 25.5 33.48 36 -54.371 (variable) 35.54 Image plane ∞ Aspheric data 3rd page K = 0.00000e+00 A 4= 5.24353e-05 A 6=-1.26025e-07 A 8= 1.47656e-10 A10=-5.90236e-14 Side 4 K =-3.95231e+00 A 4= 1.44227e-04 A 6=-3.81341e-07 A 8= 3.24673e-10 A10=-9.02355e-14 Page 31 K = 0.00000e+00 A 4= 7.86949e-06 A 6=-8.40872e-09 A 8= 5.43729e-12 A10=-2.87438e-17 Various data Focal length 17.20 F-number 4.10 Half angle of view (°) 51.52 Image height 21.64 Lens length 146.51 Sk 15.00 Normal state Shift state d12 0.69 0.57 d15 2.99 3.11 d21 3.50 3.50 d26 3.00 3.00 d31 3.50 3.50 d36 15.00 15.00 Lens group data Lens group starting surface focal length Lens group length 1 1 -10.40 41.40 2 13 49.91 6.00 3 16 64.29 12.39 4 22 50.37 22.46 5 27 106.35 21.70 6 32 -69.87 13.88 (Numerical Example 2) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 50.319 3.50 1.76385 48.5 65.54 2 24.101 4.13 44.83 3* 35.774 3.50 1.58313 59.4 43.75 4* 17.702 7.61 35.88 5 38.696 2.00 1.53775 74.7 34.66 6 14.689 8.85 25.24 7 -86.308 1.20 1.49700 81.5 24.13 8 15.243 0.50 20.24 9 14.649 7.60 1.68893 31.1 20.11 10 -80.748 0.84 17.60 11 -38.588 1.20 2.05090 26.9 16.76 12 45.393 (variable) 15.55 13 24.149 1.00 2.05090 26.9 14.66 14 13.950 5.00 1.62004 36.3 13.70 15 -34.076 (variable) 12.63 16 35.087 3.00 1.76182 26.5 12.61 17 -1670.959 2.00 12.55 18 (Aperture) ∞ 3.00 12.44 19 -139.965 1.20 1.85150 40.8 12.29 20 28.897 3.17 1.49700 81.5 12.31 21 -41.104 (variable) 12.55 22 51.167 9.00 1.49700 81.5 35.89 23 -47.728 1.20 1.87070 40.7 36.77 24 454.095 0.30 39.44 25 60.529 8.00 1.59522 67.7 44.05 26 -128.553 (variable) 44.58 27 95.051 8.00 1.49700 81.5 33.50 28 -35.280 1.20 1.91082 35.2 34.28 29 -118.697 4.45 36.49 30 64.841 9.00 1.49700 81.5 43.52 31* -36.030 (variable) 43.93 32 -111.995 7.17 1.86966 20.0 30.99 33 -22.503 1.50 2.05090 26.9 31.04 34 -99.257 3.76 32.19 35 -30.639 1.50 2.00330 28.3 32.20 36 -52.942 (variable) 34.16 Image plane ∞ Aspheric data 3rd page K = 0.00000e+00 A 4= 2.90081e-05 A 6=-4.94325e-08 A 8= 7.16006e-11 A10=-3.42108e-14 Side 4 K =-1.94563e+00 A 4= 6.01440e-05 A 6=-8.30954e-08 A 8= 8.67346e-11 A10=-2.08615e-13 Page 31 K = 0.00000e+00 A 4= 1.91579e-05 A 6= 6.38108e-10 A 8=-1.42507e-11 A10= 2.07924e-14 Various data Focal length 17.00 F-number 4.10 Half angle of view (°) 51.84 Image height 21.64 Lens length 146.52 Sk 15.00 Normal state Shift state d12 1.38 1.21 d15 3.76 3.93 d21 3.50 3.50 d26 5.00 5.00 d31 3.50 3.50 d36 15.00 15.00 Lens group data Lens group starting surface focal length Lens group length 1 1 -7.39 40.93 2 13 32.95 6.00 3 16 60.07 12.37 4 22 71.91 18.50 5 27 46.71 22.65 6 32 -52.37 13.93 (Numerical Example 3) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 51.433 3.50 1.76385 48.5 67.20 2 24.552 3.80 45.70 3* 68.578 3.50 1.58313 59.4 44.39 4* 28.186 9.38 37.17 5 57.812 2.00 1.53775 74.7 36.07 6 14.488 8.83 25.52 7 -179.054 1.20 1.49700 81.5 24.85 8 16.034 0.50 21.88 9 14.799 7.64 1.68893 31.1 22.02 10 -83.785 0.56 20.46 11 -59.245 1.20 2.05090 26.9 19.77 12 22.501 (variable) 17.90 13 15.098 1.00 2.05090 26.9 17.71 14 10.494 6.70 1.59551 39.2 16.24 15 -24.910 (variable) 15.65 16 22.982 3.00 1.49700 81.5 12.55 17 -116.957 2.00 12.36 18 (Aperture) ∞ 3.00 11.91 19 -33.275 1.20 1.90525 35.0 11.40 20 15.817 3.92 1.84666 23.8 11.57 21 -62.267 (variable) 11.80 22 -563.988 10.00 1.49700 81.5 22.78 23 -13.825 1.20 1.80518 25.4 25.30 24 -30.324 0.57 32.94 25 -92.610 10.00 1.59522 67.7 39.64 26* -26.601 (variable) 42.69 27 62.298 4.71 1.49700 81.5 32.53 28 -241.379 (variable) 32.36 29 -128.854 3.22 1.89286 20.4 41.68 30 -76.350 2.00 1.75500 52.3 41.99 31* 203.073 (variable) 42.73 32 80.350 10.00 1.59270 35.3 30.54 33 -21.112 1.50 2.05090 26.9 30.12 34 -60.466 3.07 31.79 35 -29.276 1.50 2.05090 26.9 31.81 36 -47.460 (variable) 33.82 Image plane ∞ Aspheric data 3rd page K = 0.00000e+00 A 4= 7.04652e-05 A 6=-9.00378e-08 A 8= 6.61476e-11 A10=-5.55951e-14 Side 4 K =-3.13661e+00 A 4= 9.27393e-05 A 6= 5.29036e-08 A 8=-8.15116e-10 A10= 1.02187e-12 Page 26 K = 0.00000e+00 A 4= 3.38164e-06 A 6= 2.22922e-09 A 8=-4.50788e-12 A10= 1.39529e-14 Page 31 K = 0.00000e+00 A 4=-6.86388e-07 A 6=-6.90636e-10 A 8= 2.86724e-12 A10=-4.67347e-15 Various data Focal length 17.04 F-number 4.10 Half angle of view (°) 51.78 Image height 21.64 Lens length 146.51 Sk 15.00 Normal state Shift state d12 0.92 0.93 d15 4.89 4.87 d21 3.50 3.50 d26 2.50 2.50 d28 5.00 5.00 d31 4.00 4.00 d36 15.00 15.00 Lens group data Lens group starting surface focal length Lens group length 1 1 -6.14 42.11 2 13 20.83 7.70 3 16 88.26 13.12 4 22 48.89 21.77 5 27 100.15 4.71 6 29 -112.54 5.22 7 32 -108.88 16.07 (Numerical Example 4) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 62.070 3.50 1.76385 48.5 66.73 2 23.449 4.02 43.58 3* 31.892 3.50 1.58313 59.4 42.60 4* 16.110 8.76 35.37 5 46.576 2.00 1.53775 74.7 33.85 6 15.816 7.15 25.75 7 166.534 1.20 1.49700 81.5 24.78 8 16.623 0.50 21.56 9 16.547 8.00 1.69895 30.1 21.45 10 -129.334 1.13 18.51 11 -37.364 1.20 1.64000 60.1 17.78 12 38.739 (variable) 15.89 13 24.965 1.00 2.05090 26.9 15.15 14 15.080 5.00 1.58144 40.8 14.73 15 -63.020 (variable) 14.76 16 35.584 3.00 1.51742 52.4 14.32 17 -38.681 2.00 13.96 18 (Aperture) ∞ 3.00 12.52 19 -237.788 1.20 1.88100 40.1 11.64 20 23.639 3.03 1.49700 81.5 11.56 21 -57.508 (variable) 11.71 22 112.640 9.00 1.49700 81.5 26.41 23 -19.768 1.20 1.85150 40.8 28.72 24 -41.774 0.30 33.67 25 -144.436 8.00 1.59522 67.7 38.10 26 -29.987 (variable) 39.86 27 -112.347 8.00 1.49700 81.5 31.10 28 -24.326 1.20 1.83400 37.2 32.39 29 -76.545 8.98 35.85 30 359.975 8.50 1.49700 81.5 45.49 31* -29.710 (variable) 46.45 32 -53.271 7.09 1.86966 20.0 33.52 33 -22.366 1.50 1.72342 38.0 34.09 34 -62.085 3.35 35.10 35 -31.319 1.50 2.00330 28.3 35.00 36 -51.463 (variable) 36.92 Image plane ∞ Aspheric data 3rd page K = 0.00000e+00 A 4= 2.81750e-05 A 6=-5.57286e-08 A 8= 6.04624e-11 A10=-5.83916e-17 Side 4 K =-2.56179e+00 A 4= 8.45674e-05 A 6=-2.00095e-07 A 8= 2.84311e-10 A10=-2.90879e-13 Page 31 K = 0.00000e+00 A 4= 1.66955e-05 A 6= 2.67805e-09 A 8=-5.85414e-12 A10= 1.42374e-14 Various data Focal length 17.50 F-number 4.10 Half angle of view (°) 51.03 Image height 21.64 Lens length 146.51 Sk 15.00 Normal state Shift state d12 1.53 1.11 d15 2.17 2.58 d21 3.50 3.50 d26 3.00 3.00 d31 3.50 3.50 d36 15.00 15.00 Lens group data Lens group starting surface focal length Lens group length 1 1 -9.79 40.97 2 13 49.26 6.00 3 16 55.46 12.23 4 22 45.27 18.50 5 27 75.88 26.68 6 32 -102.55 13.43 (Numerical Example 5) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 53.608 3.50 1.76385 48.5 78.02 2 30.155 8.00 56.48 3* 32.870 3.50 1.58313 59.4 55.06 4* 13.975 (variable) 40.21 5 120.000 2.00 1.59522 67.7 32.19 6 27.193 5.29 27.08 7 -99.449 1.20 1.49700 81.5 26.17 8 21.378 0.60 23.05 9 23.156 7.58 1.67270 32.1 22.98 10 -98.312 1.90 20.62 11 -25.822 1.20 1.49700 81.5 20.05 12 -148.441 (variable) 18.90 13 29.129 1.00 1.88100 40.1 12.89 14 12.902 5.31 1.67270 32.1 12.81 15 -743.008 (variable) 13.16 16 -333.891 1.99 1.63980 34.5 13.30 17 -40.724 2.00 13.46 18 (Aperture) ∞ 2.00 13.36 19 23.751 3.19 1.51742 52.4 13.24 20 -21.391 0.40 12.97 21 -23.526 1.20 1.95375 32.3 12.56 22 23.037 3.00 1.49700 81.5 12.36 23 -249.548 (variable) 12.53 24 43.994 10.00 1.49700 81.5 23.44 25 -15.755 1.20 1.71736 29.5 25.15 26 -23.912 3.81 28.02 27 64.961 10.00 1.59522 67.7 35.46 28* -24.345 (variable) 35.79 29 -31.003 5.58 1.84666 23.8 24.08 30 -15.062 1.20 1.88100 40.1 24.07 31 -453.601 4.42 24.37 32 -22.534 3.00 1.85400 40.4 24.40 33* -155.616 3.50 28.11 34 200.589 5.69 1.84666 23.9 33.92 35 -53.699 1.50 1.51633 64.1 34.99 36 -63.527 (variable) 35.89 Image plane ∞ Aspheric data 3rd page K = 0.00000e+00 A 4=-5.12234e-06 A 6= 8.44527e-10 A 8= 2.76766e-12 A10=-4.53500e-15 Side 4 K =-1.03189e+00 A 4= 6.98434e-06 A 6=-1.38569e-08 A 8= 8.47276e-11 A10=-1.76557e-13 Page 28 K = 0.00000e+00 A 4= 1.90344e-05 A 6= 1.01387e-11 A 8= 1.95743e-11 A10=-1.24321e-15 Page 33 K = 0.00000e+00 A 4= 9.77235e-06 A 6= 1.94067e-08 A 8=-1.43774e-10 A10= 3.45245e-13 Various data Focal length 17.50 F-number 4.10 Half angle of view (°) 51.03 Image height 21.64 Lens length 146.35 Sk 15.04 Normal state Shift state d 4 16.00 16.00 d12 3.00 2.70 d15 2.04 2.34 d23 3.00 3.00 d28 2.50 2.50 d36 15.04 15.04 Lens group data Lens group starting surface focal length Lens group length 1 1 -28.66 15.00 2 5 -38.54 19.77 3 13 65.75 6.31 4 16 164.23 13.79 5 24 20.52 25.01 6 29 -29.04 24.90 (Numerical Example 6) Unit: mm Surface number rd nd νd Effective diameter 1 51.292 3.50 1.76385 48.5 76.07 2 29.450 8.00 55.12 3* 43.784 3.50 1.58313 59.4 53.45 4* 18.276 11.90 41.65 5 120.000 2.00 1.59522 67.7 40.19 6 17.732 8.23 ​​28.93 7 -54422.146 1.20 1.49700 81.5 28.26 8 20.185 1.02 25.14 9 23.342 7.59 1.69895 30.1 25.11 10 -41.775 0.52 23.91 11 -37.347 1.20 1.49700 81.5 22.91 12 22.303 (variable) 19.25 13 15.312 4.19 1.51742 52.4 15.72 14 360.656 0.50 14.36 15 38.875 1.00 2.00330 28.3 13.33 16 9.904 6.76 1.71736 29.5 12.34 17 207.177 (variable) 12.40 18 -81.966 1.93 1.53775 74.7 12.65 19 -30.527 2.00 12.81 20 (Aperture) ∞ 2.00 12.65 21 25.229 2.87 1.72151 29.2 12.68 22 -23.664 0.53 12.45 23 -22.902 1.20 2.05090 26.9 12.00 24 21.708 3.00 1.59282 68.6 11.81 25 158.195 (variable) 11.99 26 56.566 10.00 1.49700 81.5 20.75 27 -12.735 1.20 1.59551 39.2 22.69 28 -21.152 0.50 26.39 29 88.291 9.95 1.53775 74.7 31.37 30* -20.077 (variable) 32.18 31 -23.376 4.68 1.86966 20.0 21.97 32 -14.418 1.20 1.88100 40.1 22.31 33 -132.185 (variable) 23.36 34 -21.144 3.00 1.85400 40.4 23.60 35* -56.412 3.50 27.18 36 -210.189 5.86 1.84666 23.8 31.71 37 -32.288 1.50 1.78800 47.4 32.90 38 -50.853 (variable) 34.65 Image plane ∞ Aspheric data 3rd page K = 0.00000e+00 A 4= 1.84447e-05 A 6=-3.73633e-08 A 8= 3.94282e-11 A10=-1.89228e-14 Side 4 K =-7.79455e-01 A 4= 2.05710e-05 A 6=-1.79568e-08 A 8=-9.13771e-11 A10= 6.72824e-14 Page 30 K = 0.00000e+00 A 4= 2.18033e-05 A 6= 1.93567e-08 A 8=-3.42454e-11 A10= 2.61435e-13 Page 35 K = 0.00000e+00 A 4= 8.46172e-06 A 6= 1.62777e-08 A 8=-1.29489e-10 A10= 3.96568e-13 Various data Focal length 17.14 F-number 4.10 Half angle of view (°) 51.61 Image height 21.64 Lens length 146.51 Sk 15.00 Normal state Shift state d12 3.00 3.00 d17 2.34 2.34 d25 3.00 3.00 d30 2.80 2.70 d33 4.35 4.44 d38 15.00 15.00 Lens group data Lens group starting surface focal length Lens group length 1 1 -9.72 48.65 2 13 35.72 12.45 3 18 181.84 13.53 4 26 19.01 21.65 5 31 -32.66 5.88 6 34 -141.90 13.86 (Numerical Example 7) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 52.654 3.50 1.80400 46.5 66.68 2 24.327 3.80 45.27 3* 32.207 3.50 1.58313 59.4 44.07 4* 16.627 9.86 36.87 5 65.299 2.00 1.59522 67.7 35.63 6 15.917 9.42 25.94 7 -43.490 1.20 1.49700 81.5 25.01 8 20.745 0.50 22.53 9 21.275 7.96 1.59551 39.2 22.55 10 -38.663 1.54 21.16 11 -21.961 1.20 1.92119 24.0 20.58 12 -38.709 (variable) 20.67 13 40.742 1.00 2.05090 26.9 19.16 14 22.387 5.00 1.62004 36.3 18.30 15 -32.567 (variable) 18.44 16 42.866 3.00 1.84666 23.9 16.25 17 79917.028 2.00 15.58 18 (Aperture) ∞ 3.00 14.42 19 -267.994 1.20 1.95375 32.3 12.74 20 20.851 4.02 1.49700 81.5 12.22 21 -33.571 (variable) 12.40 22 66.137 9.00 1.49700 81.5 36.72 23 -43.050 1.20 1.95375 32.3 37.73 24 -128.410 (variable) 40.11 25 647.567 4.31 1.49700 81.5 24.33 26 -34.725 (variable) 25.33 27 -65.302 3.91 1.86966 20.0 35.87 28 -39.072 1.20 1.83481 42.7 36.43 29* 68.581 (variable) 38.71 30 31.361 9.00 1.59522 67.7 35.95 31 -121.553 2.09 35.63 32 -217.750 3.00 1.76385 48.5 34.42 33* 100.396 3.44 33.21 34 145.636 9.00 1.49700 81.5 34.25 35 -28.866 1.50 2.00069 25.5 35.08 36 -39.995 (variable) 37.00 Image plane ∞ Aspheric data 3rd page K = 0.00000e+00 A 4= 4.45530e-05 A 6=-1.19946e-07 A 8= 1.80321e-10 A10=-1.23816e-13 Side 4 K =-6.46881e-01 A 4= 5.65598e-05 A 6=-1.49536e-07 A 8=-9.57652e-11 A10= 1.80023e-13 Page 29 K = 0.00000e+00 A 4=-2.53588e-06 A 6=-1.65591e-09 A 8= 7.22433e-12 A10=-7.32258e-15 Page 33 K = 0.00000e+00 A 4= 1.91894e-05 A 6= 1.49522e-08 A 8=-3.11964e-11 A10= 8.40338e-14 Various data Focal length 17.00 F-number 4.10 Half angle of view (°) 51.84 Image height 21.64 Lens length 148.50 Sk 16.76 Normal state Shift state d12 0.64 0.67 d15 7.25 7.22 d21 2.00 2.00 d24 3.00 3.00 d26 3.50 3.50 d29 4.00 4.00 d36 16.76 16.76 Lens group data Lens group starting surface focal length Lens group length 1 1 -10.73 44.48 2 13 39.70 6.00 3 16 94.03 13.22 4 22 222.82 10.20 5 25 66.45 4.31 6 27 -39.98 5.11 7 30 46.04 28.03

[0073] [Table 1]

[0074] [Imaging device] 22 shows a digital still camera (imaging device) that uses the optical system of Examples 1 to 7 as an imaging optical system. Reference numeral 13 denotes a camera body, and 11 denotes an imaging optical system. Reference numeral 12 denotes an imaging element (photoelectric conversion element) that is built into camera body 13 and photoelectrically converts a subject image formed by imaging optical system 11.

[0075] The camera body 13 may be a single-lens reflex camera with a quick-turn mirror or a mirrorless camera without a quick-turn mirror. The imaging optical system 11 may be configured as an integral part of the camera body 13, or may be configured as a detachable part.

[0076] In this way, by using the optical system of each embodiment in an imaging device, it is possible to obtain an imaging device that can capture images with the optical system in a shifted state and can obtain good images.

[0077] The above embodiment includes the following configurations.

[0078] (Configuration 1) An optical system having, in this order from the object side to the image side, a first decentered lens group and a second decentered lens group that are movable so as to be decentered with respect to a reference optical axis, Let ω be the half angle of view of the optical system in a first state in which the first and second decentered lens groups have not moved with respect to the reference optical axis, and θ be the angle that a chief ray that enters the optical system from outside the reference optical axis and reaches the center of the image surface makes with the reference optical axis when it enters the optical system in a second state in which the first and second decentered lens groups have moved with respect to the reference optical axis, 0.4≦tan θ / tan ω≦1.0 An optical system characterized by satisfying the following conditions: (Configuration 2) Let Ma be the movement amount of the first decentered lens group in the second state, Sa be the movement amount of the central ray on the image surface from the first state per unit movement amount of the first decentered lens group, Mb be the movement amount of the second decentered lens group in the second state, Sb be the movement amount of the central ray on the image surface from the first state per unit movement amount of the second decentered lens group, and f be the focal length of the optical system. 0.4≦|(Ma×Sa+Mb×Sb) / (f×tanω)|≦1.0 The optical system according to configuration 1, characterized in that the following condition is satisfied: (Configuration 3) 3. The optical system according to configuration 1 or 2, wherein at least one of the first and second decentered lens groups is movable from the first state in a direction including a tilt component with respect to the reference optical axis. (Configuration 4) The optical system described in any one of configurations 1 to 3, characterized in that the first and second decentered lens groups are each movable from the first state to the same side or opposite sides in a direction including a component tilted relative to the reference optical axis. (Configuration 5) the first decentered lens group is movable from the first state to have a component in a direction tilting with respect to the reference optical axis, Let La be the length on the reference optical axis from the lens surface of the first decentered lens group closest to the object side to the lens surface of the first decentered lens group closest to the image side in the first state, and TL be the length on the reference optical axis from the lens surface of the optical system closest to the object side to the image plane in the first state, 0.05≦La / TL≦0.30 5. The optical system according to any one of configurations 1 to 4, wherein the following condition is satisfied: (Configuration 6) the second decentered lens group is movable from the first state to have a component in a direction tilting with respect to the reference optical axis, Let Lb be the length on the reference optical axis from the lens surface of the second decentered lens group closest to the object in the first state to the lens surface of the second decentered lens group closest to the image, and TL be the length on the reference optical axis from the lens surface of the optical system closest to the object in the first state to the image plane, 0.05≦Lb / TL≦0.30 6. The optical system according to any one of configurations 1 to 5, wherein the following condition is satisfied: (Configuration 7) When the focal length of the optical system in the first state is f and the length on the reference optical axis from the lens surface of the optical system closest to the object side in the first state to the image plane is TL, 0.10≦TL / f≦0.30 7. The optical system according to any one of configurations 1 to 6, wherein the following condition is satisfied: (Configuration 8) When the focal length of the optical system in the first state is f and the air-equivalent distance on the reference optical axis from the lens surface of the optical system closest to the image side in the first state to the image plane is Sk, 0.7≦Sk / f≦1.2 8. The optical system according to any one of configurations 1 to 7, wherein the following condition is satisfied: (Configuration 9) 9. The optical system according to any one of configurations 1 to 8, wherein at least one of the first and second decentered lens groups includes two or more lenses. (Configuration 10) 10. The optical system according to any one of configurations 1 to 9, wherein at least one of the first and second decentered lens groups includes a cemented lens in which two or more lenses are cemented together. (Configuration 11) 11. The optical system according to any one of configurations 1 to 10, characterized in that it is composed of, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power as the first decentered lens group, a fifth lens group having positive refractive power as the second decentered lens group, and a sixth lens group having negative refractive power. (Configuration 12) 11. The optical system according to any one of configurations 1 to 10, characterized in that it is configured with, arranged in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, a third lens group with positive refractive power, a fourth lens group with positive refractive power as the first decentered lens group, a fifth lens group with positive refractive power, a sixth lens group with negative refractive power as the second decentered lens group, and a seventh lens group with negative refractive power. (Configuration 13) 11. The optical system according to any one of configurations 1 to 10, characterized in that it is composed of, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having negative refractive power as the first decentered lens group, a third lens group having positive refractive power, a fourth lens group having positive refractive power, a fifth lens group having positive refractive power as the second decentered lens group, and a sixth lens group having negative refractive power. (Configuration 14) 11. The optical system according to any one of configurations 1 to 10, characterized in that it is composed of, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power as the first decentered lens group, a third lens group having positive refractive power, a fourth lens group having positive refractive power as the second decentered lens group, a fifth lens group having negative refractive power, and a sixth lens group having negative refractive power. (Configuration 15) 11. The optical system according to any one of configurations 1 to 10, characterized in that it is configured with, arranged in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, a third lens group with positive refractive power, a fourth lens group with positive refractive power as the first decentered lens group, a fifth lens group with positive refractive power, a sixth lens group with negative refractive power as the second decentered lens group, and a seventh lens group with positive refractive power. (Configuration 16) An optical system having, in this order from the object side to the image side, a first decentered lens group and a second decentered lens group that are movable so as to be decentered with respect to an optical axis, An optical system characterized in that the first and second decentered lens groups each include two or more lenses. (Configuration 17) The optical system according to any one of configurations 1 to 16; and an image sensor that captures an image of a subject through the optical system.

[0079] The embodiments described above are merely representative examples, and various modifications and alterations are possible to each embodiment when implementing the present invention. [Explanation of symbols]

[0080] L0 optical system Li i-th lens group SP aperture stop IP image plane

Claims

1. An optical system having, in this order from an object side to an image side, a first decentered lens group and a second decentered lens group that are movable so as to be decentered with respect to a reference optical axis, Let ω be a half angle of view of the optical system in a first state in which the first and second decentered lens groups are not moved with respect to the reference optical axis, and θ be an angle formed by a chief ray, which is incident on the optical system from outside the reference optical axis and reaches the center of the image surface, with respect to the reference optical axis when the chief ray is incident on the optical system in a second state in which the first and second decentered lens groups are moved with respect to the reference optical axis, 0.4≦tan θ / tan ω≦1.0 An optical system characterized by satisfying the following conditions:

2. Let Ma be the movement amount of the first decentered lens group in the second state, Sa be the movement amount of the central ray on the image surface from the first state per unit movement amount of the first decentered lens group, Mb be the movement amount of the second decentered lens group in the second state, Sb be the movement amount of the central ray on the image surface from the first state per unit movement amount of the second decentered lens group, and f be the focal length of the optical system. 0.4≦|(Ma×Sa+Mb×Sb) / (f×tan ω)|≦1.0 2. The optical system according to claim 1, wherein the following condition is satisfied:

3. 2. The optical system according to claim 1, wherein at least one of the first and second decentered lens groups is movable from the first state in a direction including a component tilted with respect to the reference optical axis.

4. 2. The optical system according to claim 1, wherein the first and second decentered lens groups are movable from the first state to the same side or opposite sides in a direction including a component tilted relative to the reference optical axis.

5. the first decentered lens group is movable from the first state to have a component in a direction tilting with respect to the reference optical axis, Let La be the length on the reference optical axis from the lens surface of the first decentered lens group closest to the object side in the first state to the lens surface of the first decentered lens group closest to the image side, and TL be the length on the reference optical axis from the lens surface of the optical system closest to the object side in the first state to the image plane, 0.05≦La / TL≦0.30 2. The optical system according to claim 1, wherein the following condition is satisfied:

6. the second decentered lens group is movable from the first state to have a component in a direction tilting with respect to the reference optical axis, Let Lb be the length on the reference optical axis from the lens surface of the second decentered lens group closest to the object side to the lens surface of the second decentered lens group closest to the image side in the first state, and TL be the length on the reference optical axis from the lens surface of the optical system closest to the object side to the image plane in the first state, 0.05≦Lb / TL≦0.30 2. The optical system according to claim 1, wherein the following condition is satisfied:

7. When the focal length of the optical system in the first state is f and the length on the reference optical axis from the lens surface of the optical system closest to the object side in the first state to the image plane is TL, 0.10≦TL / f≦0.30 2. The optical system according to claim 1, wherein the following condition is satisfied:

8. When the focal length of the optical system in the first state is f and the air-equivalent distance on the reference optical axis from the lens surface of the optical system closest to the image side in the first state to the image plane is Sk, 0.7≦Sk / f≦1.2 2. The optical system according to claim 1, wherein the following condition is satisfied:

9. 2. The optical system according to claim 1, wherein at least one of the first and second decentered lens groups includes two or more lenses.

10. 2. The optical system according to claim 1, wherein at least one of the first and second decentered lens groups includes a cemented lens in which two or more lenses are cemented together.

11. 2. The optical system according to claim 1, comprising, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power as the first decentered lens group, a fifth lens group having positive refractive power as the second decentered lens group, and a sixth lens group having negative refractive power.

12. 2. The optical system according to claim 1, comprising, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power as the first decentered lens group, a fifth lens group having positive refractive power, a sixth lens group having negative refractive power as the second decentered lens group, and a seventh lens group having negative refractive power.

13. 2. The optical system according to claim 1, comprising, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having negative refractive power as the first decentered lens group, a third lens group having positive refractive power, a fourth lens group having positive refractive power, a fifth lens group having positive refractive power as the second decentered lens group, and a sixth lens group having negative refractive power.

14. 2. The optical system according to claim 1, comprising, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power as the first decentered lens group, a third lens group having positive refractive power, a fourth lens group having positive refractive power as the second decentered lens group, a fifth lens group having negative refractive power, and a sixth lens group having negative refractive power.

15. 2. The optical system according to claim 1, comprising, arranged in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power as the first decentered lens group, a fifth lens group having positive refractive power, a sixth lens group having negative refractive power as the second decentered lens group, and a seventh lens group having positive refractive power.

16. An optical system having, in this order from an object side to an image side, a first decentered lens group and a second decentered lens group that are movable so as to be decentered with respect to an optical axis, An optical system characterized in that the first and second decentered lens groups each include two or more lenses.

17. An optical system according to any one of claims 1 to 16; and an image sensor that captures an image of a subject through the optical system.

Images