Stereoscopic optical system and imaging apparatus

Abstract

The invention discloses a stereoscopic optical system and an image pickup apparatus. A stereoscopic optical system includes two optical systems configured to vary magnification and arranged in parallel. Each optical system includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit, and a rear group including a fourth lens unit and having a positive refractive power as a whole. A distance between adjacent lens units varies during zooming. The third lens unit includes a first reflection surface, a second reflection surface, and an aperture stop, and a distance between optical axes of the rear groups in the two optical systems is narrower than a distance between optical axes of the first lens unit in the two optical systems by bending an optical path by the first reflection surface and the second reflection surface. A predetermined inequality is satisfied.

Description

Technical Field

[0001] The present disclosure relates to a stereo optical system for three-dimensional imaging. Background Art

[0002] As disclosed in Japanese Unexamined Patent Application Publication No. 2023-74578 etc., for three-dimensional imaging, a stereo optical system including two optically systems arranged in parallel is used. Summary of the Invention

[0003] A stereo optical system according to one aspect of the present disclosure includes two optical systems configured to perform zooming and arranged in parallel. Each of the two optical systems includes, in order from the object side to the image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit, and a rear group including a fourth lens unit and having a positive refractive power as a whole. The distance between adjacent lens units changes during zooming. The third lens unit includes a first reflecting surface, a second reflecting surface, and an aperture stop, and due to bending of the optical path by the first reflecting surface and the second reflecting surface, the distance between the optical axes of the rear groups in the two optical systems is narrower than the distance between the optical axes of the first lens units in the two optical systems. The following inequality is satisfied:

[0004] 0.16 ≤ |m4 / f4| ≤ 1.28,

[0005] where m4 is the movement amount of the fourth lens unit during zooming from the wide-angle end to the telephoto end, and f4 is the focal length of the fourth lens unit.

[0006] A stereo optical system according to another aspect of the present disclosure includes two optical systems configured to perform zooming and arranged in parallel. Each of the two optical systems includes, in order from the object side to the image side: a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit, and a rear group including at least one lens unit. The distance between adjacent lens units changes during zooming. The third lens unit has a first reflecting surface and a second reflecting surface, and due to bending of the optical path by the first reflecting surface and the second reflecting surface, the distance between the optical axes of the rear groups in the two optical systems is narrower than the distance between the optical axes of the first lens units in the two optical systems. In each of the two optical systems, at least the second lens unit moves during zooming. The following inequality is satisfied:

[0007] 3.5 ≤ f1 / fw ≤ 32.0,

[0008] where fw is the focal length of each of the two optical systems at the wide-angle end, and f1 is the focal length of the first lens unit.

[0009] An imaging device having the above-described three-dimensional optical system also constitutes another aspect of the present disclosure.

[0010] Other features of various embodiments of the present disclosure will become apparent from the following description of the embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1A is a cross-sectional view of the three-dimensional optical system according to Example 1 at the wide-angle end.

[0012] Figure 1B and Figure 1C are longitudinal aberration diagrams of the three-dimensional optical system according to Example 1 at the wide-angle end and the telephoto end, respectively.

[0013] Figure 2A is a cross-sectional view of the three-dimensional optical system according to Example 2 at the wide-angle end.

[0014] Figure 2B and Figure 2C are longitudinal aberration diagrams of the three-dimensional optical system according to Example 2 at the wide-angle end and the telephoto end, respectively.

[0015] Figure 3A is a cross-sectional view of the three-dimensional optical system according to Example 3 at the wide-angle end.

[0016] Figure 3B and Figure 3C are longitudinal aberration diagrams of the three-dimensional optical system according to Example 3 at the wide-angle end and the telephoto end, respectively.

[0017] Figure 4A is a cross-sectional view of the three-dimensional optical system according to Example 4 at the wide-angle end.

[0018] Figure 4B and Figure 4C are longitudinal aberration diagrams of the three-dimensional optical system according to Example 4 at the wide-angle end and the telephoto end, respectively.

[0019] Figure 5A is a cross-sectional view of the three-dimensional optical system according to Example 5 at the wide-angle end.

[0020] Figure 5B and Figure 5C are longitudinal aberration diagrams of the three-dimensional optical system according to Example 5 at the wide-angle end and the telephoto end, respectively.

[0021] Figure 6A is a cross-sectional view of the three-dimensional optical system according to Example 6 at the wide-angle end.

[0022] Figure 6B and Figure 6C are longitudinal aberration diagrams of the three-dimensional optical system according to Example 6 at the wide-angle end and the telephoto end, respectively.

[0023] Figure 7 Shows a top view of each of the stereoscopic optical systems according to each of Examples 1 to 6.

[0024] Figure 8 Shows a schematic diagram of two image circles formed by the stereoscopic optical systems according to each of Examples 1 to 6.

[0025] Figure 9 Is a cross-sectional view of the stereoscopic optical system according to Example 7.

[0026] Figure 10 Is a longitudinal aberration diagram of the stereoscopic optical system according to Example 7 at wide angle in the infinite focus state.

[0027] Figure 11 Is a longitudinal aberration diagram of the stereoscopic optical system according to Example 7 at wide angle in the near focus state.

[0028] Figure 12 Is a longitudinal aberration diagram of the stereoscopic optical system according to Example 7 at telephoto end in the infinite focus state.

[0029] Figure 13 Is a longitudinal aberration diagram of the stereoscopic optical system according to Example 7 at telephoto end in the near focus state.

[0030] Figure 14 Is a cross-sectional view of the stereoscopic optical system according to Example 8.

[0031] Figure 15 Is a longitudinal aberration diagram of the stereoscopic optical system according to Example 8 at wide angle in the infinite focus state.

[0032] Figure 16 Is a longitudinal aberration diagram of the stereoscopic optical system according to Example 8 at wide angle in the near focus state.

[0033] Figure 17 Is a longitudinal aberration diagram of the stereoscopic optical system according to Example 8 at telephoto end in the infinite focus state.

[0034] Figure 18 Is a longitudinal aberration diagram of the stereoscopic optical system according to Example 8 at telephoto end in the near focus state.

[0035] Figure 19 Is a cross-sectional view of the stereoscopic optical system according to Example 9.

[0036] Figure 20 Is a longitudinal aberration diagram of the stereoscopic optical system according to Example 9 at wide angle end in the infinite focus state.

[0037] Figure 21Longitudinal aberration diagram of the three-dimensional optical system according to Example 9 in the wide-angle end in the close-focus state.

[0038] Figure 22 Longitudinal aberration diagram of the three-dimensional optical system according to Example 9 in the telephoto end in the infinity-focus state.

[0039] Figure 23 Longitudinal aberration diagram of the three-dimensional optical system according to Example 9 in the telephoto end in the close-focus state.

[0040] Figure 24 Cross-sectional view of the three-dimensional optical system according to Example 10.

[0041] Figure 25 Longitudinal aberration diagram of the three-dimensional optical system according to Example 10 in the wide-angle in the infinity-focus state.

[0042] Figure 26 Longitudinal aberration diagram of the three-dimensional optical system according to Example 10 in the wide-angle in the close-focus state.

[0043] Figure 27 Longitudinal aberration diagram of the three-dimensional optical system according to Example 10 in the telephoto end in the infinity-focus state.

[0044] Figure 28 Longitudinal aberration diagram of the three-dimensional optical system according to Example 10 in the telephoto end in the close-focus state.

[0045] Figure 29 Top views of the three-dimensional optical systems according to Examples 7 to 10, respectively.

[0046] Figure 30 Schematic diagrams of the image circles formed by the three-dimensional optical systems according to Examples 7 to 10, respectively.

[0047] Figure 31 Schematic diagram of an imaging device including the three-dimensional optical system according to any one of Examples 1 to 10. Detailed Description of the Embodiments

[0048] Now, with reference to the accompanying drawings, a detailed description of embodiments according to the present disclosure will be given. The embodiments described below are examples of means for implementing the present disclosure and can be appropriately modified or changed according to the configuration of the device to which the present disclosure is applied and various conditions. In addition, the respective embodiments can be appropriately combined.

[0049] Figure 7 The basic configurations of the three-dimensional optical systems 100 according to Examples 1 to 6, respectively, are shown as viewed from above. Figure 7In the figure, the left side is the object side, and the right side is the image side. The stereo optical system 100 includes two optical systems 101 and 102 arranged in parallel. The stereo optical system 100 can be attached to various imaging devices such as digital cameras, digital still cameras, broadcast cameras, film cameras, and surveillance cameras, and can be detached from or integrated with these imaging devices.

[0050] IP represents the image plane (paraxial imaging position). Each of the two optical systems 101 and 102 forms an optical image (image circle) on the image plane IP. Arranged on the image plane IP is the imaging surface (light receiving surface) of an image sensor such as a CCD sensor or a CMOS sensor, or the film surface (photosensitive surface) of a silver film.

[0051] In the stereo optical system 100 according to each of Examples 1 to 6, each of the two optical systems 101 and 102 sequentially includes, from the object side to the image side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, a third lens unit L3, and a rear group including a fourth lens unit L4 and having a positive refractive power as a whole. The third lens unit L3 includes a first reflecting surface PR1 arranged on the object side, a second reflecting surface PR2 arranged on the image side, and an aperture stop SP. In each of Examples 1 to 6, both the first reflecting surface PR1 and the second reflecting surface PR2 are formed on a reflector that is a prism having an incident surface, a reflecting surface (PR1 or PR2), and an exit surface, but the reflecting surface can be provided on a mirror that is a reflector without an incident surface or an exit surface. The first reflecting surface PR1 and the second reflecting surface PR2 are arranged to bend the optical path (optical axis) in each optical system. More specifically, the first reflecting surface PR1 of each optical system reflects the light incident from the object side to the other optical system in the left-right direction, and the second reflecting surface PR2 reflects the light reflected by the first reflecting surface PR1 to the image side. By bending the optical path in this way, the distance Dout between the optical axes of the rear groups (fourth lens units L4) in the two optical systems 101 and 102 is narrower than the baseline length Din, where the baseline length Din is the distance between the optical axes of the first lens units L1 in the two optical systems 101 and 102.

[0052] Therefore, as Figure 8 shown, image circles 201 and 202 are formed side by side on the image plane IP (such as the imaging surface of a single image sensor, etc.) by the optical systems 101 and 102 respectively. This configuration can provide two captured images (paired parallax images) having parallax with each other, and can be stereoscopically viewed by an imaging device having a single image sensor (such as a digital camera, etc.).

[0053] The two optical systems 101 and 102 are each configured as a zoom optical system that can be variable in magnification between a wide angle end and a telephoto end. In each optical system, the second lens unit L2 and the fourth lens unit L4 (the sub-lens units therein) move during variable magnification and change the distance between adjacent lens units.

[0054] In a zoom optical system, a lens unit (and sub-lens unit) is a group of one or more lenses that move together during zooming. That is, the distance between adjacent lens units changes during zooming. The wide-angle end and the telephoto end respectively indicate zoom states with a maximum angle of view (shortest focal length) and a minimum angle of view (longest focal length) when the lens unit that moves during zooming is located at both ends of a mechanically or controllable movable range on the optical axis.

[0055] Figure 1A , Figure 2A , Figure 3A , Figure 4A , Figure 5A and Figure 6A One of two optical systems 101 and 102 (hereinafter referred to as individual optical systems) in the stereoscopic optical systems according to Examples 1 to 6 is respectively shown.

[0056] Each optical system is a positive lead zoom optical system with a positive refractive power in the first lens unit L1 closest to the object side, and achieves a high magnification ratio while reducing the overall system size of each optical system. As described above, at least the second lens unit L2 and the fourth lens unit L4 move during magnification. The fourth lens unit L4 is divided into a plurality of sub-lens units L4s (hereinafter referred to as the fourth sub-lens unit L4s, where s=1 to 3), and each fourth sub-lens unit L4s moves to depict different trajectories. Moving the second lens unit L2 during magnification can prevent the movement amount of the fourth lens unit L4 and the lens diameter of the fourth lens unit L4 from increasing. In Examples 5 and 6, the first lens unit L1 also moves. In this specification, the fourth lens unit L4 is divided into a plurality of fourth sub-lens units L4s, but the plurality of fourth sub-lens units L4s can be regarded as a fourth lens unit, a fifth lens unit, a sixth lens unit, etc. That is, the rear group may include a plurality of lens units including the fourth lens unit.

[0057] In the above configuration, the following inequality (1) can be satisfied:

[0058] 0.16≤|m4 / f4|≤1.28 (1)

[0059] Here, m4 is the movement amount of the fourth lens unit L4 (fourth sub-lens unit L4s) during zooming from the wide-angle end to the telephoto end, and f4 is the focal length of the fourth lens unit L4 (fourth sub-lens unit L4s).

[0060] The movement amount of the lens unit (or sub-lens unit) is the difference between the positions of the lens unit on the optical axis at the wide-angle end and the telephoto end, and does not include the reciprocating movement amount. When the position of the lens unit is closer to the image side at the telephoto end than at the wide-angle end, the sign of the movement amount is positive.

[0061] To reduce the lens diameter of the first lens unit L1, interference between the two optical systems 101 and 102 arranged in parallel is avoided. Therefore, if the first lens unit L1 and the second lens unit L2 arranged on the object side of the first reflecting surface PR1 move significantly during zooming, the distance between the aperture stop SP and the first lens unit L1 and the lens diameter of the first lens unit L1 determined by off-axis rays increase. Therefore, moving the fourth lens unit L4 to a certain extent during zooming can achieve a high zoom ratio while reducing the lens diameter of the first lens unit L1.

[0062] When the movement amount of the fourth lens unit L4 during zooming increases such that |m4 / f4| becomes higher than the upper limit of the inequality (1), the distance between the aperture stop SP and the fourth lens unit L4 and the lens diameter of the fourth lens unit L4 increase. As a result, interference between the fourth lens units L4 of the two optical systems 101 and 102 becomes inevitable. When the focal length of the fourth lens unit L4 decreases such that |m4 / f4| becomes higher than the upper limit of the inequality (1), the variation in field curvature and distortion during zooming increases, and it becomes difficult to obtain high optical performance. When the movement amount of the fourth lens unit L4 during zooming decreases such that |m4 / f4| becomes lower than the lower limit of the inequality (1), a high zoom ratio cannot be obtained.

[0063] Inequality (1) can be replaced by the following inequality (1a):

[0064] 0.19 ≤ |m4 / f4| ≤ 1.09 (1a)

[0065] Inequality (1) can be replaced by the following inequality (1b):

[0066] 0.22 ≤ |m4 / f4| ≤ 0.94 (1b)

[0067] Satisfying the above configuration and conditions can provide a stereoscopic optical system having two optical systems capable of zooming while bending the optical path, and achieving a high zoom ratio and high optical performance.

[0068] A description of the conditions and configurations that the three-dimensional optical system according to each example can satisfy will now be given. The three-dimensional optical system according to each example can satisfy at least one of the following inequalities (2) to (11) and configurations.

[0069] β2w and β4w are the imaging magnifications of the second lens unit L2 and the fourth lens unit L4, respectively, in a focused state on an object at infinity (hereinafter referred to as an infinity focus state) at the wide-angle end. β2t and β4t are the imaging magnifications of the second lens unit L2 and the fourth lens unit L4, respectively, in an infinity focus state at the telephoto end. Z2 and Z4 are the zoom ratios of the second lens unit L2 and the fourth lens unit L4, respectively, from the wide-angle end to the telephoto end in an infinity focus state, and are defined as follows:

[0070] Z2 = β2t / β2w

[0071] Z4 = β4t / β4w

[0072] In this case, the three-dimensional optical system according to each example can satisfy the following inequality (2):

[0073] 0.01 ≤ |Z2 / Z4| ≤ 2.26 (2)

[0074] In the case where |Z2 / Z4| becomes higher than the upper limit of inequality (2), the zoom ratio of the second lens unit L2 becomes higher relative to the zoom ratio of the fourth lens unit L4, and the movement amount of the second lens unit L2 during zooming increases. As a result, the distance from the first lens unit L1 to the aperture stop SP and the lens diameter of the first lens unit L1 determined by the off-axis light rays increase, and interference between the two optical systems 101 and 102 becomes inevitable. In the case where |Z2 / Z4| becomes lower than the lower limit of inequality (2), the zoom ratio of the fourth lens unit L4 becomes higher relative to the zoom ratio of the second lens unit L2, and the movement amount of the fourth lens unit L4 during zooming increases. As a result, the lens diameter of the fourth lens unit L4 determined by the off-axis light rays increases, and interference between the two optical systems 101 and 102 becomes inevitable. In addition, the refractive power of the fourth lens unit L4 increases, and the variation of the field curvature and distortion aberration during zooming increases, and high optical performance cannot be obtained.

[0075] Inequality (2) can be replaced by the following inequality (2a):

[0076] 0.03 ≤ |Z2 / Z4| ≤ 2.16 (2a)

[0077] Inequality (2) can be replaced by the following inequality (2b):

[0078] 0.05 ≤ |Z2 / Z4| ≤ 2.08 (2b)

[0079] The three-dimensional optical systems according to the respective examples satisfy the following inequality (3):

[0080] 0.01 ≤ Dout / Din ≤ 0.74 (3)

[0081] Wherein, Din is the distance (baseline length) between the optical axes of the first lens unit L1 in the two optical systems, and Dout is the distance between the optical axes of the rear group (the fourth lens unit L4) in the two optical systems.

[0082] In the case where Dout / Din becomes lower than the lower limit of the inequality (3), the baseline length becomes insufficient, and sufficient three-dimensional sense cannot be obtained from a pair of parallax images. In the case where Dout / Din becomes lower than the upper limit of the inequality (3), the parallax between this pair of parallax images becomes too large.

[0083] The inequality (3) can be replaced by the following inequality (3a):

[0084] 0.03 ≤ Dout / Din ≤ 0.53 (3a)

[0085] The inequality (3) can be replaced by the following inequality (3b):

[0086] 0.18 ≤ Dout / Din ≤ 0.41 (3b)

[0087] In the three-dimensional optical systems according to the respective examples, the aperture stop SP can be disposed between the first reflecting surface PR1 and the second reflecting surface PR2 of the third lens unit L3. In the case where the aperture stop SP is disposed on the object side of the first reflecting surface PR1, the distance between the aperture stop SP and the fourth lens unit L4 and the lens diameter of the fourth lens unit L4 increase, and interference between the two optical systems 101 and 102 becomes inevitable. In the case where the aperture stop SP is disposed on the image side of the second reflecting surface PR2, the distance between the aperture stop SP and the first lens unit L1 and the lens diameter of the first lens unit L1 increase, and interference between the two optical systems 101 and 102 becomes inevitable.

[0088] The three-dimensional optical systems according to the respective examples satisfy the following inequality (4):

[0089] 0.79 ≤ dG1SP / dSPI ≤ 1.50 (4)

[0090] Wherein, dG1SP is the distance on the optical axis from the object surface of the lens closest to the object side in the first lens unit L1 at the wide-angle end to the aperture stop SP, and dSPI is the distance on the optical axis from the aperture stop SP to the image plane IP at the wide-angle end.

[0091] When dG1SP / dSPI becomes higher than the upper limit of inequality (4), the distance between the aperture stop SP and the first lens unit L1 and the lens diameter of the first lens unit L1 increase, and interference between the two optical systems 101 and 102 becomes inevitable. When dG1SP / dSPI becomes lower than the lower limit of inequality (4), the distance between the aperture stop SP and the fourth lens unit L4 and the lens diameter of the fourth lens unit L4 increase, and interference between the two optical systems 101 and 102 becomes inevitable.

[0092] Inequality (4) can be replaced by the following inequality (4a):

[0093] 0.82 ≤ dG1SP / dSPI ≤ 1.33 (4a)

[0094] Inequality (4) can be replaced by the following inequality (4b):

[0095] 0.87 ≤ dG1SP / dSPI ≤ 1.21 (4b)

[0096] The three-dimensional optical system according to each example can satisfy the following inequality (5):

[0097] 4.28 ≤ dG1SP / fw ≤ 11.32 (5)

[0098] where fw is the focal length of each optical system at the wide-angle end.

[0099] When dG1SP / fw becomes higher than the upper limit of inequality (5), the distance between the aperture stop SP and the first lens unit L1 and the lens diameter of the first lens unit L1 increase, and interference between the two optical systems 101 and 102 becomes inevitable. When dG1SP / fw becomes lower than the lower limit of inequality (5), the distance between the aperture stop SP and the first lens unit L1 increases. As a result, the amount of movement during the zooming of the first lens unit L1 and the second lens unit L2 decreases, and it becomes difficult to ensure a high zoom ratio and sufficiently correct the changes in field curvature and distortion during zooming.

[0100] Inequality (5) can be replaced by the following inequality (5a):

[0101] 4.91 ≤ dG1SP / fw ≤ 10.24 (5a)

[0102] Inequality (5) can be replaced by the following inequality (5b):

[0103] 5.53 ≤ dG1SP / fw ≤ 9.44 (5b)

[0104] The three-dimensional optical system according to each example satisfies the following inequality (6):

[0105] 5.28 ≤ dSPI / fw ≤ 19.09 (6)

[0106] When dSPI / fw becomes higher than the upper limit of inequality (6), the distance between the aperture stop SP and the fourth lens unit L4 and the lens diameter of the fourth lens unit L4 increase, and interference between the two optical systems 101 and 102 becomes inevitable. When dSPI / fw becomes lower than the lower limit of inequality (6), the distance between the aperture stop SP and the fourth lens unit L4 and the amount of movement during zooming of the fourth lens unit L4 decrease, and it becomes difficult to ensure a high magnification ratio.

[0107] Inequality (6) can be replaced by the following inequality (6a):

[0108] 5.68 ≤ dG1SP / fw ≤ 14.79 (6a)

[0109] Inequality (6) can be replaced by the following inequality (6b):

[0110] 6.08 ≤ dG1SP / fw ≤ 11.57 (6b)

[0111] The three-dimensional optical system according to each example satisfies the following inequality (7):

[0112] 9.55 ≤ Lw / fw ≤ 30.18 (7)

[0113] Here, Lw is the distance on the optical axis from the object side surface of the lens closest to the object side in the first lens unit L1 to the image plane IP at the wide-angle end.

[0114] When Lw / fw becomes higher than the upper limit of inequality (7), the distances between the aperture stop SP and the respective lens units in the first lens unit L1 and the fourth lens unit L4 and the lens diameters of the first lens unit L1 and the fourth lens unit L4 increase, and interference between the two optical systems 101 and 102 becomes inevitable. When Lw / fw becomes lower than the lower limit of inequality (7), the amount of movement of the lens unit that moves during zooming decreases, and it becomes difficult to ensure a high magnification ratio.

[0115] Inequality (7) can be replaced by the following inequality (7a):

[0116] 10.67 ≤ Lw / fw ≤ 24.74 (7a)

[0117] Inequality (7) can be replaced by the following inequality (7b):

[0118] 11.80 ≤ Lw / fw ≤ 20.66 (7b)

[0119] In the stereoscopic optical system according to each example, the third lens unit L3 may have a positive refractive power. The positive refractive power of the third lens unit L3 can reduce the height of off-axis light rays and the lens diameter of the fourth lens unit L4.

[0120] In the stereoscopic optical system according to each example, the following inequality (8) may be satisfied:

[0121] 3.43 ≤ f3 / fw ≤ 8.46 (8)

[0122] where f3 is the focal length of the third lens unit L3.

[0123] When f3 / fw becomes higher than the upper limit of inequality (8), the refractive power of the third lens unit L3 becomes too small, and the lens diameter of the fourth lens unit L4 becomes too large. When f3 / fw becomes lower than the lower limit of inequality (8), the refractive power of the third lens unit L3 becomes too large, generating spherical aberration and coma, and it becomes difficult to achieve high image quality.

[0124] Inequality (8) may be replaced by the following inequality (8a):

[0125] 3.78 ≤ f3 / fw ≤ 8.26 (8a)

[0126] Inequality (8) may be replaced by the following inequality (8b):

[0127] 4.14 ≤ f3 / fw ≤ 8.11 (8b)

[0128] In the stereoscopic optical system according to each example, the third lens unit L3 may not move (be fixed) during zooming. In particular, by fixing the third lens unit L3 including a reflecting surface that has a large influence on the optical axis shift during zooming, the optical axis shift between the two optical systems 101 and 102 becomes less likely, and the captured image can have high image quality.

[0129] In the stereoscopic optical system according to each example, the first lens unit L1 may be fixed during zooming. Such a configuration can eliminate the optical axis shift of the first lens unit L1 during zooming and improve the quality of the captured image.

[0130] In the stereoscopic optical system according to each example, the following inequality (9) may be satisfied:

[0131] 5.42 ≤ f1 / fw ≤ 17.20 (9)

[0132] where f1 is the focal length of the first lens unit L1.

[0133] When f1 / fw becomes higher than the upper limit of inequality (9), the refractive power of the first lens unit L1 decreases, and it becomes difficult to reduce the size of the first lens unit L1. When f1 / fw becomes lower than the lower limit of inequality (9), the refractive power of the first lens unit, and thus the lateral chromatic aberration and distortion, increase, and it becomes difficult to achieve high performance.

[0134] Inequality (9) can be replaced by the following inequality (9a):

[0135] 5.96 ≤ f1 / fw ≤ 14.62 (9a)

[0136] Inequality (9) can be replaced by the following inequality (9b):

[0137] 6.49 ≤ f1 / fw ≤ 12.68 (9b)

[0138] The stereoscopic optical system according to each example can satisfy the following inequality (10):

[0139] -12.61 ≤ f1 / f2 ≤ -4.91 (10)

[0140] where f2 is the focal length of the second lens unit L2.

[0141] When f1 / f2 becomes higher than the upper limit of inequality (10), the refractive power of the first lens unit L1 decreases, and it becomes difficult to reduce the size of the first lens unit L1. When f1 / f2 becomes lower than the lower limit of inequality (10), the refractive power of the first lens unit L1, and the lateral chromatic aberration and distortion, increase, and it becomes difficult to achieve high performance.

[0142] Inequality (10) can be replaced by the following inequality (10a):

[0143] -11.20 ≤ f1 / f2 ≤ -5.29 (10a)

[0144] Inequality (10) can be replaced by the following inequality (10b):

[0145] -9.78 ≤ f1 / f2 ≤ -5.40 (10b)

[0146] The stereoscopic optical system according to each example can satisfy the following inequality (11):

[0147] 2.56 ≤ f4w / fw ≤ 6.75 (11)

[0148] where f4 is the focal length of the fourth lens unit L4 at the wide-angle end.

[0149] When f4w / fw becomes higher than the upper limit of inequality (11), the refractive power of the fourth lens unit L4 decreases, and it becomes difficult to reduce the size of the fourth lens unit L4. When f4w / fw becomes lower than the lower limit of inequality (11), the refractive power, lateral chromatic aberration, and distortion of the fourth lens unit L4 increase, and it becomes difficult to achieve high performance.

[0150] Inequality (11) can be replaced by the following inequality (11a):

[0151] 2.70 ≤ f4w / fw ≤ 5.74 (11a)

[0152] Inequality (11) can be replaced by the following inequality (11b):

[0153] 2.92 ≤ f4w / fw ≤ 4.98 (11b)

[0154] A description of the specific configurations of the optical systems according to Examples 1 to 6 will now be given. As described above, each of the optical systems in Examples 1 to 6 includes, in order from the object side to the image side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, a third lens unit L3, and a fourth lens unit L4 having a positive refractive power. The third lens unit L3 has a first reflecting surface PR1 on the object side and a second reflecting surface PR2 on the image side. The aperture stop SP is disposed between the first reflecting surface PR1 and the second reflecting surface PR2 in the third lens unit L3. The third lens unit L3 in each example has a positive refractive power.

[0155] In Examples 1 to 4, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 and the third lens unit L3 do not move, and the second lens unit L2 moves toward the image side. The L4A subunit, L4B subunit, and L4C subunit, which are the fourth sub-lens units in the fourth lens unit L4, move toward the object side or the image side to draw different trajectories, or move to draw a trajectory that bulges toward the object side or the image side. The fourth lens unit L4 (each of the L4A subunit, L4B subunit, and L4C subunit) satisfies inequalities (1) and (2).

[0156] In Examples 5 and 6, during zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves to draw a trajectory that bulges toward the image side, the third lens unit L3 does not move, and the second lens unit L2 moves toward the image side. The L4A subunit and L4B subunit, which are the fourth sub-lens units constituting the fourth lens unit L4, move to draw trajectories that are different from each other toward the object side. The fourth lens unit L4 (each of the L4A subunit and L4B subunit) satisfies inequalities (1) and (2).

[0157] In Examples 1 to 6, the fourth lens unit L4 moves during focusing from infinity to a short distance (or near distance).

[0158] Descriptions of Numerical Examples 1 to 6 corresponding to Examples 1 to 6 will now be given. Numerical Examples 1, 2, 5, and 6 are numerical examples with an image height of 8.55 mm and a baseline length of 60 mm. Numerical Examples 3 and 4 are numerical examples with an image height of 8.55 mm and a baseline length of 65 mm.

[0159] In the surface data of each numerical example, the surface number i indicates the order of the surface counted from the object side. r represents the radius of curvature of the i-th surface from the object side (mm), d represents the lens thickness or air gap between the i-th surface and the (i + 1)-th surface (mm), and nd represents the refractive index of the d-line of the optical material between the i-th surface and the (i + 1)-th surface. νd represents 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 νd based on the d-line is expressed as νd = (Nd - 1) / (NF - NC), where Nd, NF, and NC are the refractive indices of the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) in the Fraunhofer lines.

[0160] BF represents the back focal length (mm). The back focal length is the distance on the optical axis from the final surface (the lens surface closest to the image plane) of each optical system to the paraxial image plane expressed in air equivalent length. The total lens length is the distance on the optical axis from the frontmost surface (the lens surface closest to the object side) of each optical system to the final surface plus the back focal length. The focal length L4w in the lens unit data represents the focal length f4w of the fourth lens unit L4 at the wide-angle end.

[0161] An asterisk "*" next to the surface number indicates that the surface has an aspherical shape. The aspherical shape is expressed as follows:

[0162] x = (h 2 / R) / [1 + {1 - (1 + k)(h / R) 2}] 1 / 2 + A4 × h 4 + A6 × h 6 + A8 × h 8 + A10 × h 10

[0163] where x is the displacement amount from the surface vertex in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, and A10 are aspherical coefficients. "e±Z" in the conic constant and aspherical coefficients represents ×10 ±Z .

[0164] Table 1 summarizes the values ​​corresponding to inequalities (1) to (11) in Numerical Examples 1 to 6. Table 1 shows the values ​​at the d-line as the reference wavelength. Each of the Numerical Examples satisfies all of the inequalities (1) to (11).

[0165] Figure 1B , Figure 2B , Figure 3B , Figure 4B , Figure 5B and Figure 6B Longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the optical systems according to Numerical Examples 1 to 6 in an infinitely focused state at the wide-angle end are respectively shown. Figure 1C , Figure 2C , Figure 3C , Figure 4C , Figure 5C and Figure 6C Longitudinal aberrations of the optical systems according to Numerical Examples 1 to 6 in an infinitely focused state at the telephoto end are respectively shown.

[0166] In the spherical aberration diagram, Fno represents the F value. The solid line indicates the spherical aberration amount of the d-line (wavelength of 587.6nm), and the dotted line indicates the spherical aberration amount of the g-line (wavelength of 435.8nm). In the astigmatism diagram, the solid line ΔS indicates the astigmatism amount on the sagittal image plane, and the dotted line ΔM indicates the astigmatism amount on the meridional image plane. The distortion aberration illustrates the distortion amount of the d-line. The chromatic aberration diagram illustrates the lateral chromatic aberration amount of the g-line. ω is the half angle of view (°).

[0167] Numerical Example 1

[0168] Unit: mm

[0169] Area data

[0170]

[0171]

[0172] Aspheric surface data

[0173] Page 6

[0174] K=0.00000e+00 A4=1.79021e-05 A6=-2.28987e-08 A8=-9.85171e-11

[0175] A10=2.62132e-13

[0176] Page 20

[0177] K = 0.00000e+00 A4 = -2.53762e-05 A6 = 9.39343e-09 A8 = -3.36281e-10

[0178] A10 = 2.37435e-13

[0179] All kinds of data

[0180]

[0181]

[0182] Lens unit data

[0183]

[0184] Numerical example 2

[0185] Unit: mm

[0186] Surface data

[0187]

[0188]

[0189]

[0190] Aspherical data

[0191] The 6th surface

[0192] K = 0.00000e+00 A4 = 1.98792e-05 A6 = -5.12977e-08 A8 = 1.19023e-10

[0193] A10 = -1.39437e-13

[0194] The 20th surface

[0195] K = 0.00000e+00 A4 = 3.16475e-05 A6 = 4.91822e-07 A8 = -2.57805e-09

[0196] A10 = -4.03369e-11

[0197] The 21st surface

[0198] K = 0.00000e+00 A4 = 1.20888e-04 A6 = 7.65121e-07 A8 = -7.08168e-09

[0199] A10 = -1.61213e-11

[0200] Page 27

[0201] K = 0.00000e+00 A4 = 6.98682e-04 A6 = -1.24476e-05 A8 = 1.15600e-07

[0202] A10 = -1.44487e-10

[0203] Page 28

[0204] K = 0.00000e+00 A4 = 7.16637e-04 A6 = -1.04228e-05 A8 = 5.01853e-08

[0205] A10 = 7.22580e-10

[0206] Various data

[0207]

[0208]

[0209] Lens unit data

[0210]

[0211] Numerical example 3 Unit: mm Surface data

[0212]

[0213]

[0214] Aspherical data

[0215] Surface 6

[0216] K = 0.00000e+00 A4 = 2.45514e-05 A6 = -5.93442e-08 A8 = 1.15631e-10

[0217] A10 = -1.26900e-13

[0218] Surface 20

[0219] K = 0.00000e+00 A4 = -1.10517e-05 A6 = 4.37172e-08 A8 = -8.66814e-10

[0220] A10 = 4.72732e-12

[0221] Various data

[0222]

[0223]

[0224] Lens unit data

[0225]

[0226] Numerical example 4

[0227] Unit: mm

[0228] Surface data

[0229]

[0230]

[0231] Aspherical surface data

[0232] The 6th surface

[0233] K = 0.00000e+00 A4 = 1.26227e-05 A6 = -3.13028e-08 A8 = -2.71222e-11

[0234] A10 = 1.54592e-13

[0235] The 20th surface

[0236] K = 0.00000e+00 A4 = 3.46778e-05 A6 = 6.66170e-07 A8 = -5.39970e-09

[0237] A10 = 1.12567e-10

[0238] The 21st surface

[0239] K = 0.00000e+00 A4 = 1.49005e-04 A6 = 8.76476e-07 A8 = -6.22349e-09

[0240] A10 = 1.31982e-10

[0241] Various data

[0242]

[0243] Lens unit data

[0244]

[0245]

[0246] Numerical Example 5

[0247] Unit: mm

[0248] Surface data

[0249]

[0250]

[0251] Aspherical surface data

[0252] The 6th surface

[0253] K = 0.00000e+00 A4 = 3.48110e-05 A6 = -1.58823e-07 A8 = 5.07462e-10

[0254] A10 = -9.45667e-13

[0255] The 20th surface

[0256] K = 0.00000e+00 A4 = -1.41902e-05 A6 = 1.53238e-07 A8 = -2.70259e-09

[0257] A10 = 4.22423e-11

[0258] The 21st surface

[0259] K = 0.00000e+00 A4 = 5.59996e-05 A6 = 1.52335e-08 A8 = -7.94237e-11

[0260] A10 = 3.28230e-11

[0261] Various data

[0262]

[0263]

[0264] Lens unit data

[0265]

[0266] Numerical Example 6

[0267] Unit: mm

[0268] Surface data

[0269]

[0270]

[0271] Aspherical data

[0272] The 6th surface

[0273] K = 0.00000e+00 A4 = 2.21645e-05 A6 = -9.05090e-08 A8 = 2.08340e-10

[0274] A10 = -5.50415e-13

[0275] The 20th surface

[0276] K = 0.00000e+00 A4 = -2.43104e-05 A6 = 6.87502e-08 A8 = -1.89488e-09

[0277] A10 = 1.25521e-11

[0278] Various data

[0279]

[0280]

[0281] Lens unit data

[0282]

[0283] Table 1

[0284]

[0285] Figure 29 Shows the basic configurations of the three-dimensional optical systems 400 according to Examples 7 to 10 as viewed from above. In Figure 29 it, the left side is the object side and the right side is the image side. The three-dimensional optical system 400 includes two optical systems 401 and 402 arranged in parallel. The three-dimensional optical system 400 can be attached to various imaging devices such as digital cameras, digital still cameras, broadcast cameras, film cameras, and surveillance cameras, and can be detached from or integrated with these imaging devices.

[0286] IM represents the image plane (paraxial imaging position). Each of the two optical systems 401 and 402 forms an optical image (image circle) on the image plane IM. Arranged on the image plane IM is the imaging surface (light-receiving surface) of an image sensor such as a CCD sensor or a CMOS sensor, or the film surface (photosensitive surface) of a silver film.

[0287] In the three-dimensional optical system 400 according to each example, each of the two optical systems 401 and 402 includes, in order from the object side to the image side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, a third lens unit L3, and a rear group LR including at least one lens unit. The third lens unit L3 includes a first reflecting surface M1 disposed on the object side, a second reflecting surface M2 disposed on the image side, and an aperture stop SP. The aperture stop SP determines (limits) a light beam having a maximum opening (minimum F value or Fno).

[0288] In each embodiment, both the first reflecting surface M1 and the second reflecting surface M2 are formed on a reflector that is a prism having an incident surface, a reflecting surface (M1 or M2), and an exit surface, but the reflecting surface may be provided on a mirror that is a reflector not having an incident surface or an exit surface.

[0289] The first reflecting surface M1 and the second reflecting surface M2 are provided to bend an optical path (optical axis) in each optical system. More specifically, the first reflecting surface M1 of each optical system reflects light incident from the object side to the other optical system in the left-right direction, and the second reflecting surface M2 reflects the light reflected by the first reflecting surface M1 to the image side. By bending the optical path in this way, the distance Dout between the optical axes of the rear group LR is narrower than the baseline length Din, where the baseline length Din is the distance between the optical axes of the first lens units L1 of the two optical systems 401 and 402.

[0290] As Figure 30 shown, image circles 501 and 502 are formed side by side on an image plane IM (such as an imaging plane of a single image sensor, etc.) by the optical systems 401 and 402. Such a configuration can obtain two captured images having parallax with respect to each other (paired parallax images), and can be stereoscopically viewed by an imaging device having a single image sensor (such as a digital camera, etc.).

[0291] Each of the two optical systems 401 and 402 is configured as a zoom optical system that can be zoomed between a wide-angle end and a telephoto end. In each optical system, at least the second lens unit L2 moves during zooming.

[0292] In a zoom optical system, a lens unit is a group of one or more lenses that move together during zooming or focusing. That is, during zooming or focusing, the distance between adjacent lens units changes. The wide-angle end and the telephoto end during zooming indicate the maximum viewing angle (shortest focal length) and the minimum viewing angle (longest focal length) states when the lens unit that moves during zooming is located at both ends of a mechanically or controllably movable range on the optical axis.

[0293] Figure 9 、 Figure 14 、 Figure 19 andFigure 24 One of the two optical systems 401 and 402 of the stereoscopic optical system according to Examples 7 to 10 is shown (hereinafter referred to as each optical system). OA in each figure indicates the optical axis.

[0294] Each optical system is a positive front-zoom optical system in which the first lens unit L1 closest to the object side has a positive refractive power, and a high magnification ratio is achieved while reducing the total size of each optical system. As described above, in each example, at least the second lens unit L2 moves during zooming. Such a configuration can achieve a high magnification ratio. In Examples 1, 3, and 4, the second lens unit L2 and the fourth lens unit L4 move during zooming. Such a configuration can prevent an increase in the amount of movement of the fourth lens unit L4 and the lens diameter (effective diameter) of the fourth lens unit L4. In Example 2, the first lens unit L1 and the second lens unit L2 move during zooming.

[0295] In the above configuration, the following inequality (12) can be satisfied:

[0296] 3.5 ≤ f1 / fw ≤ 32.0 (12)

[0297] Where fw is the focal length of each optical system at the wide-angle end, and f1 is the focal length of the first lens unit L1.

[0298] In the case where f1 increases such that f1 / fw becomes higher than the upper limit of inequality (12), the size of the entire optical system increases, and it becomes difficult to obtain a high magnification ratio. In the case where fw increases such that f1 / fw becomes lower than the lower limit of inequality (12), it becomes difficult to achieve the wide angle of each optical system.

[0299] Inequality (12) can be replaced by the following inequality (12a):

[0300] 3.6 ≤ f1 / fw ≤ 30.0 (12a)

[0301] Inequality (12) can be replaced by the following inequality (12b):

[0302] 3.7 ≤ f1 / fw ≤ 28.0 (12b)

[0303] Satisfying the above configuration and conditions can achieve a stereoscopic optical system including two optical systems in a parallel configuration that can zoom and are configured to bend the optical path, and having a sufficient baseline length, wide angle, and high magnification ratio.

[0304] Now, a description will be given of the configuration and conditions that each optical system can satisfy. Each optical system can satisfy at least one of the following configuration and inequalities (13) to (20).

[0305] Each optical system may have a configuration that does not form an intermediate image. This configuration reduces the total length of the optical system.

[0306] In each optical system, the third lens unit L3 may not move (be fixed) during zooming. This configuration can simplify the mechanism for driving the lens units that move during zooming.

[0307] In each optical system, an aperture stop SP may be provided between the first reflecting surface M1 and the second reflecting surface M2. This configuration can suppress an increase in the lens diameter of the entire optical system and reduce the size of the entire optical system.

[0308] In each optical system, the following inequality (13) may be satisfied:

[0309] 0.05 ≤ Dm / Lw ≤ 0.50 (13)

[0310] Where Dm is the distance on the optical axis between the first reflecting surface M1 and the second reflecting surface M2, and Lw is the total optical length of the optical system at the wide-angle end.

[0311] When Dm increases such that Dm / Lw becomes higher than the upper limit of inequality (13), the size of the entire optical system increases. When Dm decreases such that Dm / Lw becomes lower than the lower limit of inequality (13), it is difficult to ensure a sufficient baseline length.

[0312] The following inequality (14) may be satisfied:

[0313] 0.05 ≤ Dm / fm ≤ 0.80 (14)

[0314] Where fm is the focal length of the sub-group GM disposed between the first reflecting surface M1 and the second reflecting surface M2 in the third lens unit L3 of each optical system.

[0315] When Dm increases such that Dm / fm becomes higher than the upper limit of inequality (14), the size of the entire optical system increases. When fm decreases such that Dm / fm becomes higher than the upper limit of inequality (14), it is difficult to correct coma. When Dm decreases such that Dm / fm becomes lower than the lower limit of inequality (14), it is difficult to ensure a sufficient baseline length. When fm increases such that Dm / fm becomes lower than the lower limit of inequality (14), the effective diameter of the second reflecting surface M2 increases.

[0316] Each optical system may satisfy the following inequality (15):

[0317] 1.7 ≤ D3 / D1 ≤ 10.0 (15)

[0318] Here, D1 is the length (thickness) on the optical axis from the surface closest to the object side to the surface closest to the image side of the first lens unit L1, and D3 is the thickness on the optical axis from the surface closest to the object side to the surface closest to the image side of the third lens unit L3.

[0319] When D3 is increased such that D3 / D1 becomes higher than the upper limit of inequality (15), the size of the entire optical system increases. When D3 is decreased such that D3 / D1 becomes lower than the lower limit of inequality (15), it becomes difficult to ensure a sufficient baseline length.

[0320] Each optical system can satisfy the following inequality (16):

[0321] 0.9 ≤ Dm / D1 ≤ 5.0 (16)

[0322] When Dm is increased such that Dm / D1 becomes higher than the upper limit of inequality (16), the size of the entire optical system increases. When Dm is decreased such that Dm / D1 becomes lower than the lower limit of inequality (16), it becomes difficult to ensure a sufficient baseline length.

[0323] Each optical system can satisfy the following inequality (17):

[0324] 0.35 ≤ D2 / D1 ≤ 2.50 (17)

[0325] Here, D2 is the thickness on the optical axis from the object side surface of the second lens unit L2 to the surface closest to the image side of the second lens unit L2.

[0326] When D2 is increased such that D2 / D1 becomes higher than the upper limit of inequality (17), the size of the entire optical system increases. When D2 is decreased such that D2 / D1 becomes lower than the lower limit of inequality (17), it becomes difficult to ensure sufficient variable magnification.

[0327] Each optical system can satisfy the following inequality (18):

[0328] 0.30 ≤ dp1 / Dm ≤ 0.90 (18)

[0329] Here, dp1 is the distance on the optical axis between the first reflecting surface M1 and the aperture stop SP.

[0330] When dp1 is increased such that dp1 / Dm becomes higher than the upper limit of inequality (18), the effective diameter of the first lens unit L1 or the effective diameter of the first reflecting surface M1 increases. When dp1 is decreased such that dp1 / Dm becomes lower than the lower limit of inequality (18), interference may occur between the first reflecting surface M1 and the aperture stop SP.

[0331] Each optical system satisfies the following inequality (19):

[0332] 0.9 ≤ f3 / Dm ≤ 3.5 (19)

[0333] where f3 is the focal length of the third lens unit L3.

[0334] When f3 increases such that f3 / Dm becomes higher than the upper limit of inequality (19), the effective diameter of the rear group LR increases. When f3 decreases such that f3 / Dm becomes lower than the lower limit of inequality (19), it becomes difficult to correct coma.

[0335] Each optical system satisfies the following inequality (20):

[0336] 0.05 ≤ Dout / Din ≤ 0.50 (20)

[0337] where Din is the distance between the optical axes of the first lens unit L1 (baseline length), and Dout is the distance between the optical axes of the rear group LR.

[0338] When Dout increases such that Dout / Din becomes higher than the upper limit of inequality (20), it is difficult to form the image circles of the two optical systems on a single image sensor. When Din decreases such that Dout / Din becomes higher than the upper limit of inequality (20), it is difficult to ensure a sufficient baseline length. When Dout decreases such that Dout / Din becomes lower than the lower limit of inequality (20), interference may occur between the rear groups LR. When Din increases such that Dout / Din becomes lower than the lower limit of inequality (20), the size of the entire optical system increases.

[0339] Inequalities (13) to (20) can be replaced by the following inequalities (13a) to (20a):

[0340] 0.07 ≤ Dm / Lw ≤ 0.40 (13a)

[0341] 0.07 ≤ Dm / fm ≤ 0.70 (14a)

[0342] 1.8 ≤ D3 / D1 ≤ 8.5 (15a)

[0343] 1.0 ≤ Dm / D1 ≤ 4.0 (16a)

[0344] 0.38 ≤ D2 / D1 ≤ 2.20 (17a)

[0345] 0.40 ≤ dp1 / Dm ≤ 0.80 (18a)

[0346] 1.0 ≤ f3 / Dm ≤ 3.2 (19a)

[0347] 0.08 ≤ Dout / Din ≤ 0.45 (20a)

[0348] Inequalities (13) to (20) can be replaced with the following inequalities (13b) to (20b):

[0349] 0.09 ≤ Dm / Lw ≤ 0.30 (13b)

[0350] 0.09 ≤ Dm / fm ≤ 0.60 (14b)

[0351] 1.9 ≤ D3 / D1 ≤ 7.0 (15b)

[0352] 1.1 ≤ Dm / D1 ≤ 3.5 (16b)

[0353] 0.41 ≤ D2 / D1 ≤ 1.90 (17b)

[0354] 0.50 ≤ dp1 / Dm ≤ 0.75 (18b)

[0355] 1.1 ≤ f3 / Dm ≤ 2.9 (19b)

[0356] 0.11 ≤ Dout / Din ≤ 0.40 (20b)

[0357] Specific descriptions of the optical systems in Examples 7 to 10 and their corresponding numerical Examples 7 to 10 will now be given.

[0358] Example 7

[0359] Figure 9 The optical system according to Example 7 (Numerical Example 7) shown has an aperture ratio of approximately 4.0 and a half field angle of approximately 39.0° at the wide-angle end and an aperture ratio of approximately 4.0 and a half field angle of approximately 17.2° at the telephoto end.

[0360] The optical systems according to Examples 7 to 10 each include, in order from the object side to the image side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, a third lens unit L3 having a positive refractive power, a fourth lens unit L4 having a positive refractive power, and a fifth lens unit L5 having a negative refractive power. During zooming, the first lens unit L1, the third lens unit L3, and the fifth lens unit L5 do not move, and during zooming from the wide-angle end to the telephoto end, as Figure 9 indicated by the slanted arrow in, the second lens unit L2 moves toward the image side, and the fourth lens unit L4 moves toward the object side. During focusing from an object at infinity to an object at a close distance, as Figure 9 indicated by the horizontal arrow in, the fourth lens unit L4 moves toward the object side.

[0361] The third lens unit L3 includes a first reflecting surface M1 and a second reflecting surface M2, and an aperture stop SP is disposed between the first reflecting surface M1 and the second reflecting surface M2. A sub-group GM including cemented lenses is disposed between the first reflecting surface M1 and the aperture stop SP (the second reflecting surface M2) in the third lens unit L3, wherein a negative lens and a positive lens are cemented together in the cemented lenses.

[0362] Figure 10 and Figure 11 respectively show the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the optical system according to Numerical Example 7 in an infinitely distant focusing state and in a close focusing state at the wide-angle end. Figure 12 and Figure 13 respectively show the longitudinal aberrations of the optical system according to Example 7 in an infinitely distant focusing state and in a close focusing state at the telephoto end.

[0363] Example 8

[0364] Figure 14 The optical system shown in [Example 8 (Numerical Example 8)] is a zoom optical system that has an aperture ratio of approximately 4.0 and a half field angle of approximately 31.7° at the wide-angle end and an aperture ratio of approximately 4.0 and a half field angle of approximately 14.3° at the telephoto end.

[0365] The optical system according to this example sequentially includes a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, a third lens unit L3 having a positive refractive power, a fourth lens unit L4 having a positive refractive power, and a fifth lens unit L5 having a negative refractive power from the object side to the image side. During zooming, the third lens unit L3, the fourth lens unit L4, and the fifth lens unit L5 do not move, and during zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves toward the object side, and the second lens unit L2 moves toward the image side. During focusing from an object at infinity to an object at a close distance, the fourth lens unit L4 moves toward the object side.

[0366] The third lens unit L3 has a first reflecting surface M1 and a second reflecting surface M2, and an aperture stop SP is disposed between the first reflecting surface M1 and the second reflecting surface M2. A sub-group GM formed by cemented lenses is disposed between the first reflecting surface M1 and the aperture stop SP (the second reflecting surface M2) in the third lens unit L3, wherein a negative lens and a positive lens are cemented together in the cemented lenses.

[0367] Figure 15 and Figure 16 respectively show the longitudinal aberrations of the optical system according to Numerical Example 8 in an infinitely distant focusing state and in a close focusing state at the wide-angle end.Figure 17 and Figure 18 show the longitudinal aberration of the optical system according to Numerical Example 8 in the telephoto end at the infinite focus state and in the close focus state, respectively.

[0368] Example 9

[0369] Figure 19 The optical system shown according to Example 9 (Numerical Example 9) is a zoom optical system, which has an aperture ratio of about 5.6 and a half field angle of about 48.7° at the wide-angle end and an aperture ratio of about 5.6 and a half field angle of about 19.8° at the telephoto end.

[0370] The optical system according to this example includes, in order from the object side to the image side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, a third lens unit L3 having a positive refractive power, a fourth lens unit L4 having a positive refractive power, and a fifth lens unit L5 having a negative refractive power. During zooming, the first lens unit L1, the third lens unit L3, and the fifth lens unit L5 do not move, and during zooming from the wide-angle end to the telephoto end, the second lens unit L2 moves toward the image side, and the fourth lens unit L4 moves toward the object side. During focusing from an object at infinity to an object at a close distance, the fourth lens unit L4 moves toward the object side.

[0371] The third lens unit L3 has a first reflecting surface M1 and a second reflecting surface M2, and the aperture stop SP is disposed between the first reflecting surface M1 and the second reflecting surface M2. A sub-group GM formed by cemented lenses is disposed between the first reflecting surface M1 and the aperture stop SP (the second reflecting surface M2) in the third lens unit L3, where a negative lens and a positive lens are cemented together in the cemented lenses.

[0372] Figure 20 and Figure 21 show the longitudinal aberration of the optical system according to Numerical Example 9 in the wide-angle end at the infinite focus state and in the close focus state, respectively. Figure 22 and Figure 23 show the longitudinal aberration of the optical system according to Numerical Example 9 in the telephoto end at the infinite focus state and in the close focus state, respectively.

[0373] Example 10

[0374] Figure 24 The optical system shown in is a zoom optical system, which has an aperture ratio of about 4.0 and a half field angle of about 34.8° at the wide-angle end and an aperture ratio of about 4.0 and a half field angle of about 17.2° at the telephoto end.

[0375] The optical system according to this example includes, in order from the object side to the image side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, a third lens unit L3 having a positive refractive power, and a fourth lens unit L4 having a positive refractive power. The first lens unit L1 and the third lens unit L3 do not move during zooming, and during zooming from the wide-angle end to the telephoto end, the second lens unit L2 moves toward the image side and the fourth lens unit L4 moves toward the object side. During focusing from an object at infinity to an object at a short distance, the fourth lens unit L4 moves toward the object side.

[0376] The third lens unit L3 has a first reflecting surface M1 and a second reflecting surface M2, and the aperture stop SP is disposed between the first reflecting surface M1 and the second reflecting surface M2. A sub-group GM formed by cemented lenses is disposed between the first reflecting surface M1 and the aperture stop SP (the second reflecting surface M2) in the third lens unit L3, where a negative lens and a positive lens are cemented together in the cemented lenses.

[0377] Figure 25 and Figure 26 show the longitudinal aberrations of the optical system according to Numerical Example 10 in the infinite-focus state and in the short-distance focus state at the wide-angle end, respectively. Figure 27 and Figure 28 show the longitudinal aberrations of the optical system according to Numerical Example 10 in the infinite-focus state and in the short-distance focus state at the telephoto end, respectively.

[0378] Numerical Examples 7 to 10 will be shown below. For Numerical Examples 7 to 9, the baseline length is set to 80 mm, and for Numerical Example 10, the baseline length is set to 70 mm. The descriptions of the symbols in each numerical example are similar to those of Numerical Examples 1 to 6.

[0379] At the end of each numerical example, the movement amount of the focusing lens unit (the fourth lens unit L4) from the infinite-focus state to the short-distance focus state at the wide-angle end and the movement amount of the focusing lens unit from the infinite-focus state to the short-distance focus state at the telephoto end are shown. The movement amount of the focusing lens unit is the difference between the position of the focusing lens unit in the infinite-focus state and the position of the focusing lens unit at the telephoto end, and when the focusing lens unit is located closer to the image plane in the short-distance focus state than in the infinite-focus state, the movement amount of the focusing lens unit is considered positive.

[0380] Table 2 summarizes the values corresponding to inequalities (12) to (20) in Numerical Examples 7 to 10. Each numerical example satisfies all of inequalities (12) to (20).

[0381] Numerical Example 7

[0382] Unit: mm

[0383]

[0384]

[0385]

[0386] All kinds of data

[0387]

[0388] Lens unit data

[0389]

[0390] First reflecting surface M1 15

[0391] Second reflecting surface M2 22

[0392] Focusing lens unit

[0393] Starting surface 26

[0394] Ending surface 33

[0395] Movement amount of the focusing lens unit towards the near - distance focusing state (-0.5 m) at the wide - angle end: -0.23 (mm)

[0396] Movement amount of the focusing lens unit towards the near - distance focusing state (-1.0 m) at the wide - angle end: -0.91 (mm)

[0397] Numerical example 8

[0398] Unit: mm

[0399] Surface data

[0400]

[0401]

[0402] Aspherical surface data of the 8th surface

[0403] K = 0.00000e+00 A4 = 7.25708e - 05 A6 = -3.54113e - 07 A8 = 1.63113e - 09

[0404] A10 = -3.97443e - 12

[0405] All kinds of data

[0406]

[0407] Lens unit data

[0408]

[0409] First reflecting surface M1 15

[0410] Second reflecting surface M2 22

[0411] Focusing lens unit

[0412] Starting surface 26

[0413] Ending surface 30

[0414] Movement amount of the focusing lens unit to the near - distance focusing state (-0.5 m) at the wide - angle end -0.37 (mm)

[0415] Movement amount of the focusing lens unit to the near - distance focusing state (-1.5 m) at the wide - angle end -0.59 (mm)

[0416] Numerical example 9

[0417] Unit: mm

[0418] Surface data

[0419]

[0420]

[0421] Aspherical surface data

[0422] The 4th surface

[0423] K = 0.00000e+00 A4 = 1.30577e - 05 A6 = 1.74397e - 08 A8 = -1.06744e - 10

[0424] A10 = 1.75114e - 13

[0425] The 22nd surface

[0426] K = 0.00000e+00 A4 = -3.57428e - 05 A6 = -3.03374e - 07 A8 = 1.95630e - 10

[0427] A10 = -4.04960e - 11

[0428] Various data

[0429]

[0430] Lens unit data

[0431]

[0432] The first reflecting surface M1 11

[0433] The second reflecting surface M2 18

[0434] Focus lens unit

[0435] Starting surface 22

[0436] Ending surface 29

[0437] Movement amount of the focus lens unit towards the close-focus state (-0.5 m) at the wide-angle end -0.11 (mm)

[0438] Movement amount of the focus lens unit towards the close-focus state (-1.0 m) at the wide-angle end -0.52 (mm)

[0439] Numerical example 10

[0440] Unit: mm

[0441] Surface data

[0442]

[0443]

[0444] Various data

[0445]

[0446]

[0447] Lens unit data

[0448]

[0449] The first reflecting surface M1 11

[0450] The second reflecting surface M2 18

[0451] Focus lens unit

[0452] Starting surface 20

[0453] Ending surface 27

[0454] Movement amount of the focus lens unit towards the close-focus state (-0.5 m) at the wide-angle end -0.33 (mm)

[0455] Movement amount of the focus lens unit towards the close-focus state (-1.0 m) at the wide-angle end -0.85 (mm)

[0456] Table 2

[0457]

[0458] Imaging device

[0459] Figure 31 An imaging device 300 is shown that includes the stereo optical system 100 or 400 according to any one of Examples 1 to 10. The imaging device 300 includes a camera body 320 and a lens device having the stereo optical system 100 or 400 according to any one of Examples 1 to 10. The camera body 320 includes an image sensor 310, such as a CCD sensor or a CMOS sensor, for photoelectrically converting two optical images formed by the stereo optical system 100 or 400 (i.e., imaging an object).

[0460] The lens device can be attached to and detached from the camera body 320, or can be integrated with the camera body 320. The camera body 320 can be a single-lens reflex camera having a quick-return mirror, or a mirrorless camera without a quick-return mirror.

[0461] The imaging device 300 having the stereo optical system 100 or 400 according to each example can provide high-quality captured images (a pair of parallax images) that allow for good stereoscopic viewing.

[0462] Although the present disclosure describes exemplary embodiments, it should be understood that the present disclosure is not limited to the exemplary embodiments. The scope of the appended claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0463] Each example can provide a stereo optical system including two optical systems in a parallel configuration that are capable of zooming and configured to bend an optical path, and having sufficient zoom ratio and high optical performance.

Claims

1. A stereo optical system, comprising: Two optical systems, which are configured for zooming and are arranged in parallel, Characterized in that each of the two optical systems successively includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit, and a rear group from the object side to the image side, the rear group includes a fourth lens unit and has a positive refractive power as a whole, Wherein, the distance between adjacent lens units changes during zooming, Wherein, the third lens unit includes a first reflecting surface, a second reflecting surface, and an aperture stop, and due to the bending of the optical path by the first reflecting surface and the second reflecting surface, the distance between the optical axes of the rear groups in the two optical systems is narrower than the distance between the optical axes of the first lens units in the two optical systems, and Wherein, the following inequality is satisfied: 0.16 ≤ |m4 / f4| ≤ 1.28, Wherein, m4 is the moving amount of the fourth lens unit during zooming from the wide-angle end to the telephoto end, and f4 is the focal length of the fourth lens unit.

2. The stereoscopic optical system according to claim 1, wherein The following inequality is satisfied: 0.01 ≤ |Z2 / Z4| ≤ 2.26, Wherein, β2w and β4w are the imaging magnifications of the second lens unit and the fourth lens unit in the focused state for an object at infinity at the wide-angle end, respectively, and β2t and β4t are the imaging magnifications of the second lens unit and the fourth lens unit in the focused state for an object at infinity at the telephoto end, respectively, and Z2 = β2t / β2w, Z4 = β4t / β4w.

3. The three-dimensional optical system according to claim 1, characterized in that, The following inequality is satisfied: 0.01 ≤ Dout / Din ≤ 0.74, Wherein, Din is the distance between the optical axes of the first lens units in the two optical systems, and Dout is the distance between the optical axes of the rear groups in the two optical systems.

4. The three-dimensional optical system according to claim 1, characterized in that The aperture stop is arranged between the first reflecting surface and the second reflecting surface in the third lens unit.

5. The three-dimensional optical system according to claim 1, characterized in that, The following inequality is satisfied: 0.79 ≤ dG1SP / dSPI ≤ 1.50, Wherein, dG1SP is the distance on the optical axis from the object side surface of the lens closest to the object in the first lens unit to the aperture stop at the wide-angle end, and dSPI is the distance on the optical axis from the aperture stop to the image plane at the wide-angle end.

6. The three-dimensional optical system according to claim 1, wherein The following inequality is satisfied: 4.28 ≤ dG1SP / fw ≤ 11.32, Wherein, dG1SP is the distance on the optical axis from the object side surface of the lens closest to the object in the first lens unit to the aperture stop at the wide-angle end, and fw is the focal length of each of the two optical systems at the wide-angle end.

7. The three-dimensional optical system according to claim 1, characterized in that, The following inequality is satisfied: 5.28 ≤ dSPI / fw ≤ 19.09, Wherein, dSPI is the distance on the optical axis from the aperture stop to the image plane at the wide-angle end, and fw is the focal length of each of the two optical systems at the wide-angle end.

8. The three-dimensional optical system according to claim 1, wherein, The following inequality is satisfied: 9.55 ≤ Lw / fw ≤ 19.09, Wherein, Lw is the distance on the optical axis from the object side surface of the lens closest to the object in the first lens unit to the image plane at the wide-angle end, and fw is the focal length of each of the two optical systems at the wide-angle end.

9. The three-dimensional optical system according to claim 1, wherein The third lens unit has a positive refractive power.

10. The three-dimensional optical system according to claim 1, characterized in that, The following inequality is satisfied: 3.43 ≤ f3 / fw ≤ 8.46, Wherein, f3 is the focal length of the third lens unit, and fw is the focal length of each of the two optical systems at the wide-angle end.

11. The three-dimensional optical system according to claim 1, characterized in that, The following inequality is satisfied: 5.42 ≤ f1 / fw ≤ 17.20, Wherein, f1 is the focal length of the first lens unit, and fw is the focal length of each of the two optical systems at the wide-angle end.

12. The three-dimensional optical system according to claim 1, characterized in that The following inequality is satisfied: -12.61 ≤ f1 / f2 ≤ -4.91, Wherein, f1 is the focal length of the first lens unit, and f2 is the focal length of the second lens unit.

13. The stereoscopic optical system according to any one of claims 1 to 12, characterized in that, The following inequality is satisfied: 2.56 ≤ f4w / fw ≤ 6.75, Wherein, f4w is the focal length of the fourth lens unit at the wide-angle end, and fw is the focal length of each of the two optical systems at the wide-angle end.

14. A stereo optical system, comprising: Two optical systems, which are configured to perform zooming and are arranged in parallel, Characterized in that each of the two optical systems sequentially includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit, and a rear group from the object side to the image side, and the rear group includes at least one lens unit, Wherein, the distance between adjacent lens units changes during zooming, and Wherein, the third lens unit has a first reflecting surface and a second reflecting surface, and due to the bending of the optical path by the first reflecting surface and the second reflecting surface, the distance between the optical axes of the rear groups in the two optical systems is narrower than the distance between the optical axes of the first lens units in the two optical systems.

15. The stereoscopic optical system according to claim 14, wherein In each of the two optical systems, at least the second lens unit moves during zooming, and Wherein, the following inequality is satisfied: 3.5 ≤ f1 / fw ≤ 32.0, Wherein, fw is the focal length of each of the two optical systems at the wide-angle end, and f1 is the focal length of the first lens unit.

16. The three-dimensional optical system according to claim 14, characterized in that, An aperture stop is arranged between the first reflecting surface and the second reflecting surface in the third lens unit.

17. The three-dimensional optical system according to claim 14, wherein The following inequality is satisfied: 0.05 ≤ Dm / Lw ≤ 0.50, Wherein, Dm is the distance on the optical axis between the first reflecting surface and the second reflecting surface, and Lw is the total optical length of each of the two optical systems at the wide-angle end.

18. The three-dimensional optical system according to claim 14, wherein The following inequality is satisfied: 0.05 ≤ Dm / fm ≤ 0.80, Wherein, Dm is the distance on the optical axis between the first reflecting surface and the second reflecting surface, and fm is the focal length of the subgroup arranged between the first reflecting surface and the second reflecting surface in the third lens unit.

19. The three-dimensional optical system according to claim 14, characterized in that, The following inequality is satisfied: 1.7 ≤ D3 / D1 ≤ 10.0, Here, D1 is the thickness on the optical axis from the surface of the first lens unit closest to the object to the surface of the first lens unit closest to the image plane, and D3 is the thickness on the optical axis from the surface of the third lens unit closest to the object to the surface of the third lens unit closest to the image plane.

20. The three-dimensional optical system according to claim 14, characterized in that, The following inequality is satisfied: 0.9 ≤ Dm / D1 ≤ 5.0, where Dm is the distance on the optical axis between the first reflecting surface and the second reflecting surface, and D1 is the thickness on the optical axis from the surface of the first lens unit closest to the object to the surface of the first lens unit closest to the image plane.

21. The three-dimensional optical system according to claim 14, wherein The following inequality is satisfied: 0.35 ≤ D2 / D1 ≤ 2.50, where D1 is the thickness on the optical axis from the surface of the first lens unit closest to the object to the surface of the first lens unit closest to the image plane, and D2 is the thickness on the optical axis from the surface of the second lens unit closest to the object to the surface of the second lens unit closest to the image plane.

22. The three-dimensional optical system according to claim 14, wherein The third lens unit includes an aperture stop, where the following inequality is satisfied: 0.30 ≤ dp1 / Dm ≤ 0.90, where dp1 is the distance on the optical axis between the first reflecting surface and the aperture stop, and Dm is the distance on the optical axis between the first reflecting surface and the second reflecting surface.

23. The three-dimensional optical system according to claim 14, characterized in that, The following inequality is satisfied: 0.9 ≤ f3 / Dm ≤ 3.5, where f3 is the focal length of the third lens unit L3, and Dm is the distance on the optical axis between the first reflecting surface and the second reflecting surface.

24. The three-dimensional optical system according to any one of claims 14 to 23, characterized in that The following inequality is satisfied: 0.05 ≤ Dout / Din ≤ 0.50, where Din is the distance between the optical axes of the first lens units in the two optical systems, and Dout is the distance between the optical axes of the rear groups in the two optical systems.

25. An imaging device, comprising: the stereo optical system according to any one of claims 1 to 24; and an image sensor configured to image an object via the stereo optical system.

Images