Stereo optical system and imaging apparatus

Abstract

To provide a stereo optical system with which a sufficient magnification ratio and high optical performance can be obtained.SOLUTION: A stereo optical system 100 has two magnification-variable optical systems 101, 102 that are arranged in parallel. The two optical systems each comprise a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group, and a rear group including a fourth lens group and having positive refractive power as a whole. The third lens group includes a first reflecting surface PR1, a second reflecting surface PR2, and an aperture stop SP, and bending of an optical path by the first and second reflecting surfaces reduces the optical axis interval between the rear groups compared to the optical axis interval between the first lens groups in the two optical systems. When the amount of movement of the fourth lens group from a wide-angle end to a telephoto end in zooming is defined as m4, and the focal length of the fourth lens group as f4, the condition of 0.16≤|m4 / f4|≤1.28 is satisfied.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a stereo optical system used for stereoscopic imaging.

Background Art

[0002] As a stereo optical system in which two optical systems are arranged in parallel, Patent Document 1 discloses a positive-zoom type variable-power optical system having a first lens group with a positive refractive power, a second lens group with a negative refractive power, and a rear group including one or more subsequent lens groups. Two such optical systems are used. In this stereo optical system, two reflecting surfaces are provided between the second lens group and the rear group in each optical system to bend the optical path, thereby ensuring the optical axis interval (baseline length) between the first lens groups while narrowing the optical axis interval of the rear group, and forming two subject images by the two optical systems on a single imaging device. Further, zooming is performed by moving the second lens group on the object side of the aperture stop arranged on the object side of the two reflecting surfaces.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the stereo optical system of Patent Document 1, when trying to perform zooming while making each optical system wider-angle and moving the second lens group, the diameter of the lens on the object side becomes the largest, and the lenses on the object side interfere with each other, making it impossible to arrange the two optical systems in parallel.

[0005] The present invention provides a stereo optical system that has a configuration for bending the optical path and in which two variable-power optical systems are arranged in parallel so as to obtain a sufficient zoom ratio and high optical performance, and an imaging device including the same.

Means for Solving the Problems

[0006] As one aspect of the present invention, a stereo optical system has two zoomable optical systems arranged in parallel. Each of the two optical systems includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group, and a fourth lens group, which are arranged in order from the object side to the image side, and a rear group having a positive refractive power as a whole. The distance between adjacent lens groups changes during zooming. The third lens group includes a first reflecting surface, a second reflecting surface, and an aperture stop. Due to the bending of the optical path by the first and second reflecting surfaces, the optical axis distance between the rear groups is narrower than the optical axis distance between the first lens groups in the two optical systems. When the moving amount during zooming from the wide-angle end to the telephoto end of the fourth lens group is m4 and the focal length of the fourth lens group is f4, each of the two optical systems is composed of a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group, and a fourth lens group, which are arranged in order from the object side to the image side, and a rear group having a positive refractive power as a whole. The distance between adjacent lens groups changes during zooming. The third lens group includes a first reflecting surface, a second reflecting surface, and an aperture stop. Due to the bending of the optical path by the first and second reflecting surfaces, the optical axis distance between the rear groups is narrower than the optical axis distance between the first lens groups in the two optical systems. When the moving amount during zooming from the wide-angle end to the telephoto end of the fourth lens group is m4 and the focal length of the fourth lens group is f4, 0.16 ≦ |m4 / f4| ≦ 1.28 is characterized by satisfying the following conditions. An imaging device including the above stereo optical system also constitutes another aspect of the present invention.

Effect of the Invention

[0007] According to the present invention, in a stereo optical system in which two zoomable optical systems having a configuration for bending the optical path are arranged in parallel, a sufficient zoom ratio and high optical performance can be obtained.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Best Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0010] FIG. 7 shows the basic configuration of the stereo optical system 100 of Examples 1 to 6 as viewed from above. In FIG. 7, the left side is the object side and the right side is the image side. The stereo optical system 100 has two optical systems 101 and 102 arranged in parallel. The stereo optical system 100 is detachable or integrally provided in various imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, and surveillance cameras.

[0011] IP is the image plane (paraxial imaging position). The two optical systems 101 and 102 each form an optical image (image circle) on the image plane IP. On the image plane IP, the imaging surface (light-receiving surface) of an imaging element such as a CCD sensor or a CMOS sensor or the film surface (photosensitive surface) of a silver halide film is arranged.

[0012] The stereo optical system 100 of each embodiment is composed of two optical systems 101 and 102, each including a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3, and a rear group including a fourth lens group L4 and having positive refractive power as a whole, which are arranged in order from the object side to the image side. The third lens group 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 embodiment, both the first reflecting surface PR1 and the second reflecting surface PR2 are formed as reflecting members in the form of prisms having an incident surface, a reflecting surface (PR1 or PR2), and an exit surface, but they may be provided on mirrors as reflecting members having no incident surface and exit surface for the reflecting surface.

[0013] The first reflecting surface PR1 and the second reflecting surface PR2 are provided to bend the optical path (optical axis) in each optical system. Specifically, the first reflecting surface PR1 of each optical system reflects the light incident from the object side to the other optical system side 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 optical axis interval Dout between the rear groups (the fourth lens group L4) is narrower than the baseline length Din, which is the optical axis interval between the first lens groups L1 of the two optical systems 101 and 102.

[0014] For this reason, as shown in FIG. 8, on the image plane IP (for example, the imaging plane of a single imaging element), an image circle 201 and an image circle 202 are formed side by side by the optical system 101 and the optical system 102, respectively. Thereby, an imaging device such as a digital camera equipped with a single imaging element can acquire two imaging images (a pair of parallax images) having stereoscopic vision with mutual parallax.

[0015] In addition, the two optical systems 101 and 102 are each configured as a zoom optical system that can be zoomed between a wide-angle end and a telephoto end. In each optical system, when zooming, the second lens group L2 and the fourth lens group L4 (the sub-lens group inside) move, so that the interval between adjacent lens groups changes.

[0016] In a zoom optical system, a lens group (and a sub-lens group) is a collection of one or more lenses that move together during zooming. That is, the distance between adjacent lens groups changes during zooming. The wide-angle end and the telephoto end respectively indicate the zoom states of the maximum angle of view (shortest focal length) and the minimum angle of view (longest focal length) when the lens group that moves during zooming is located at both ends of the range where it can move mechanically or controllably on the optical axis.

[0017] FIG. 1(a), FIG. 2(a), FIG. 3(a), FIG. 4(a), FIG. 5(a) and FIG. 6(a) respectively show one of the two optical systems 101 and 102 that constitute the stereo optical system of Examples 1 to 6 (hereinafter referred to as each optical system).

[0018] Each optical system is a positive-reading type zoom optical system in which the first lens group L1 on the object side has a positive refractive power, and while miniaturizing the entire optical system, a high zoom ratio is realized. As described above, at least the second lens group L2 and the fourth lens group L4 move during zooming. The fourth lens group L4 is divided into a plurality of sub-lens groups L4s (hereinafter referred to as the fourth sub-lens groups L4s, where s = 1 to 3), and each of the fourth sub-lens groups L4s moves along different trajectories. By the movement of the second lens group L2 during zooming, it is possible to avoid the movement amount of the fourth lens group L4 becoming too large and the lens diameter of the fourth lens group L4 becoming too large. In Examples 5 and 6, the first lens group L1 also moves. In this embodiment, the case where the fourth lens group L4 is divided into a plurality of fourth sub-lens groups L4s will be described, but the plurality of fourth sub-lens groups L4s may be regarded as the fourth lens group, the fifth lens group, the sixth lens group, etc. That is, the rear group may have a plurality of lens groups including the fourth lens group.

[0019] In the above configuration, when the moving amount of the fourth lens group L4 (fourth sub-lens group L4s) during zooming from the wide-angle end to the telephoto end is m4 and the focal length of the fourth lens group L4 (fourth sub-lens group L4s) is f4, the condition of the following formula (1) is satisfied. Here, the moving amount of the lens group (and sub-lens group) is the difference in the positions on the optical axis of the lens group at the wide-angle end and the telephoto end, and does not include the reciprocating moving amount. The sign of the moving amount is positive when the lens group is located on the image side at the telephoto end compared to the wide-angle end.

[0020] 0.16 ≦ |m4 / f4| ≦ 1.28 (1) The lens diameter of the first lens group L1 needs to be small in order to avoid interference between the two optical systems 101 and 102 arranged in parallel. For this reason, when the first lens group L1 and the second lens group L2 on the object side of the first reflecting surface PR1 move greatly during zooming, the distance between the aperture stop SP and the first lens group L1 becomes too large, and the lens diameter of the first lens group L1 determined by the off-axis rays becomes too large. Therefore, by moving the fourth lens group L4 to a certain extent during zooming, it becomes possible to realize a high zoom ratio while reducing the lens diameter of the first lens group L1.

[0021] When the moving amount of the fourth lens group L4 during zooming becomes large such that |m4 / f4| exceeds the upper limit of formula (1), the distance between the aperture stop SP and the fourth lens group L4 becomes too large and the lens diameter of the fourth lens group L4 becomes large. As a result, interference between the fourth lens groups L4 of the two optical systems 101 and 102 cannot be avoided, which is not preferable. Also, when the focal length of the fourth lens group L4 becomes too short such that |m4 / f4| exceeds the upper limit of formula (1), the fluctuations in the image surface aberration and distortion aberration during zooming become large, and high optical performance cannot be obtained, which is not preferable. When the moving amount of the fourth lens group L4 during zooming becomes small such that |m4 / f4| is below the lower limit of the conditional formula (1), a high zoom ratio cannot be obtained, which is not preferable.

[0022] Note that it is more preferable if the numerical range of formula (1) is as follows.

[0023] 0.19 ≦ |m4 / f4| ≦ 1.09 (1a) Also, it is more preferable to set the numerical range of formula (1) as follows.

[0024] 0.22 ≦ |m4 / f4| ≦ 0.94 (1b) By satisfying the above configuration and conditions, a stereo optical system can be obtained that has two optical systems capable of changing magnification while bending the optical path and achieves a high magnification ratio and high optical performance.

[0025] Next, the preferable conditions and configurations satisfied by the stereo optical systems of the respective embodiments will be described. The stereo optical systems of the respective embodiments preferably satisfy at least one of the conditions and configurations of the following formulas (2) to (11).

[0026] Let the imaging magnifications of the second lens group L2 and the fourth lens group L4 in the state of being focused on an object at infinity at the wide-angle end (hereinafter referred to as the infinity-focus state) be β2w and β4w, respectively. Also, let the imaging magnifications of the second lens group L2 and the fourth lens group L4 in the state of being focused on an object at infinity at the telephoto end be β2t and β4t, respectively. Let the magnification ratios of the second lens group L2 and the fourth lens group L4 in the infinity-focus state from the wide-angle end to the telephoto end be Z2 and Z4, respectively, Z2 = β2t / β2w Z4 = β4t / β4w and assume this. At this time, the stereo optical systems of the respective embodiments preferably satisfy the condition of the following formula (2).

[0027] 0.01 ≦ |Z2 / Z4| ≦ 2.26 (2) When |Z2 / Z4| exceeds the upper limit of Equation (2), the magnification ratio of the second lens group L2 becomes too large with respect to the magnification ratio of the fourth lens group L4, and the movement amount during the zooming of the second lens group L2 increases. As a result, the distance from the aperture stop SP of the first lens group L1 becomes too long, the lens diameter of the first lens group L1 determined by the off-axis rays becomes large, and interference between the two optical systems 101 and 102 cannot be avoided, which is not preferable. When |Z2 / Z4| is below the lower limit of Equation (2), the magnification ratio of the fourth lens group L4 becomes too large with respect to the magnification ratio of the second lens group L2, and the movement amount during the zooming of the fourth lens group L4 increases. As a result, the lens diameter of the fourth lens group L4 determined by the off-axis rays becomes large, and interference between the two optical systems 101 and 102 cannot be avoided, which is not preferable. In addition, the refractive power of the fourth lens group L4 becomes too large, and fluctuations in the field curvature and distortion during zooming become large, making it impossible to obtain high optical performance, which is not preferable.

[0028] Note that it is more preferable if the numerical range of Equation (2) is as follows.

[0029] 0.03 ≦ |Z2 / Z4| ≦ 2.16 (2a) Also, it is even more preferable if the numerical range of Equation (2) is as follows.

[0030] 0.05 ≦ |Z2 / Z4| ≦ 2.08 (2b) For the stereo optical system of each embodiment, when the optical axis interval (baseline length) between the first lens groups L1 in the two optical systems is Din and the optical interval of the rear group (the fourth lens group L4) is Dout, it is preferable to satisfy the condition of the following Equation (3).

[0031] 0.01 ≦ Dout / Din ≦ 0.74 (3) When Dout / Din is below the lower limit of Equation (3), the baseline length is insufficient and sufficient stereoscopic effect cannot be obtained from the pair of parallax images, which is not preferable. When Dout / Din is below the upper limit of Equation (3), the parallax between the pair of parallax images becomes excessive, which is not preferable.

[0032] In addition, it is more preferable if the numerical range of formula (3) is as follows.

[0033] 0.03 ≦ Dout / Din ≦ 0.53 (3a) Also, it is even more preferable if the numerical range of formula (3) is as follows.

[0034] 0.18 ≦ Dout / Din ≦ 0.41 (3b) In the stereo optical system of each embodiment, it is preferable that the aperture stop SP is disposed between the first reflecting surface PR1 and the second reflecting surface PR2 in the third lens group L3. If 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 group L4 becomes too large, and the lens diameter of the fourth lens group L4 increases, making it impossible to avoid interference between the two optical systems 101 and 102, which is not preferable. If 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 group L1 becomes too large, and the lens diameter of the first lens group L1 increases, making it impossible to avoid interference between the two optical systems 101 and 102, which is not preferable.

[0035] In the stereo optical system of each embodiment, when the distance on the optical axis from the object side surface of the lens closest to the object side in the first lens group L1 at the wide-angle end to the aperture stop SP is dG1SP, and the distance on the optical axis from the aperture stop SP to the image plane IP at the wide-angle end is dSPI, it is preferable to satisfy the condition of the following formula (4).

[0036] 0.79 ≦ dG1SP / dSPI ≦ 1.50 (4) If dG1SP / dSPI exceeds the upper limit of formula (4), the distance between the aperture stop SP and the first lens group L1 becomes too large, and the lens diameter of the first lens group L1 increases, making it impossible to avoid interference between the two optical systems 101 and 102, which is not preferable. If dG1SP / dSPI is below the lower limit of formula (4), the distance between the aperture stop SP and the fourth lens group L4 becomes too large, and the lens diameter of the fourth lens group L4 increases, making it impossible to avoid interference between the two optical systems 101 and 102, which is not preferable.

[0037] Incidentally, it is more preferable if the numerical range of formula (4) is as follows.

[0038] 0.82 ≦ dG1SP / dSPI ≦ 1.33 (4a) Also, it is even more preferable if the numerical range of formula (4) is as follows.

[0039] 0.87 ≦ dG1SP / dSPI ≦ 1.21 (4b) When the total focal length of each optical system at the wide-angle end is fw, the stereo optical system of each embodiment preferably satisfies the condition of the following formula (5).

[0040] 4.28 ≦ dG1SP / fw ≦ 11.32 (5) When dG1SP / fw exceeds the upper limit of formula (5), the distance between the aperture stop SP and the first lens group L1 becomes too large, and the lens diameter of the first lens group L1 increases, making it impossible to avoid interference between the two optical systems 101 and 102, which is not preferable. When dG1SP / fw is below the lower limit of formula (5), the distance between the aperture stop SP and the first lens group L1 becomes too small. As a result, the amount of movement during zooming of the first lens group L1 and the second lens group L2 becomes small, making it impossible to ensure a high zoom ratio, or it becomes difficult to sufficiently correct fluctuations in image plane aberration and distortion aberration during zooming, which is not preferable.

[0041] Incidentally, it is more preferable if the numerical range of formula (5) is as follows.

[0042] 4.91 ≦ dG1SP / fw ≦ 10.24 (5a) Also, it is even more preferable if the numerical range of formula (5) is as follows.

[0043] 5.53 ≦ dG1SP / fw ≦ 9.44 (5b) The stereo optical system of each embodiment preferably satisfies the condition of the following formula (6).

[0044] 5.28 ≦ dSPI / fw ≦ 19.09 (6) When dSPI / fw exceeds the upper limit of Equation (6), the distance between the aperture stop SP and the fourth lens group L4 becomes too large, and the lens diameter of the fourth lens group L4 increases, making it impossible to avoid interference between the two optical systems 101 and 102, which is not preferable. When dSPI / fw is less than the lower limit of Equation (6), the distance between the aperture stop SP and the fourth lens group L4 becomes too small, and the moving amount during the zooming of the fourth lens group L4 becomes small, making it difficult to ensure a high zoom ratio, which is not preferable.

[0045] Note that it is more preferable if the numerical range of Equation (6) is as follows.

[0046] 5.68 ≦ dG1SP / fw ≦ 14.79 (6a) Also, it is even more preferable if the numerical range of Equation (6) is as follows.

[0047] 6.08 ≦ dG1SP / fw ≦ 11.57 (6b) When the distance from the object-side surface of the most object-side lens in the first lens group L1 at the wide-angle end to the image plane IP on the optical axis is Lw in the stereo optical system of each embodiment, it is preferable to satisfy the condition of the following Equation (7).

[0048] 9.55 ≦ Lw / fw ≦ 30.18 (7) When Lw / fw exceeds the upper limit of Equation (7), the distances between the aperture stop SP and the first lens group L1 and the fourth lens group L4 become too large, and the lens diameters of the first lens group L1 and the fourth lens group L4 increase, making it impossible to avoid interference between the two optical systems 101 and 102, which is not preferable. When Lw / fw is less than the lower limit of the conditional equation (7), the moving amount of the lens group that moves during zooming becomes too small, making it difficult to ensure a high zoom ratio, which is not preferable.

[0049] Note that it is more preferable if the numerical range of Equation (7) is as follows.

[0050] 10.67 ≦ Lw / fw ≦ 24.74 (7a) Also, it is even more preferable if the numerical range of Equation (7) is as follows.

[0051] 11.80 ≦ Lw / fw ≦ 20.66 (7b) In each embodiment, the stereo optical system preferably has a positive refractive power in the third lens group L3. By the positive refractive power of the third lens group L3, the height of off-axis light rays can be reduced, and the lens diameter of the fourth lens group L4 can be made smaller.

[0052] In each embodiment, when the focal length of the third lens group L3 is f3, the stereo optical system preferably satisfies the conditions of the following formula (8).

[0053] 3.43 ≦ f3 / fw ≦ 8.46 (8) If f3 / fw exceeds the upper limit of formula (8), the refractive power of the third lens group L3 becomes too small, and the lens diameter of the fourth lens group L4 becomes too large, which is not preferable. If f3 / fw is below the lower limit of formula (8), the refractive power of the third lens group L3 becomes too large, spherical aberration and coma aberration occur, and it becomes difficult to achieve high image quality, which is not preferable.

[0054] Note that it is more preferable if the numerical range of formula (8) is as follows.

[0055] 3.78 ≦ f3 / fw ≦ 8.26 (8a) Also, it is even more preferable if the numerical range of formula (8) is as follows.

[0056] 4.14 ≦ f3 / fw ≦ 8.11 (8b) In each embodiment, the stereo optical system preferably has the third lens group L3 fixed (not moving) during zooming. In particular, by fixing the third lens group L3 including a reflecting surface that has a large influence on the optical axis deviation during zooming, a structure with less optical axis deviation between the two optical systems 101 and 102 can be realized, and the captured image can be made of high image quality.

[0057] In the stereo optical system of each embodiment, it is preferable that the first lens group L1 is fixed during zooming. This can eliminate the optical axis deviation of the first lens group L1 during zooming, which is preferable for improving the image quality of the captured image.

[0058] In the stereo optical system of each embodiment, when the focal length of the first lens group L1 is f1, it is preferable to satisfy the condition of the following formula (9).

[0059] 5.42≦f1 / fw≦17.20 (9) When f1 / fw exceeds the upper limit of formula (9), the refractive power of the first lens group L1 becomes too small, and the first lens group L1 cannot be miniaturized, which is not preferable. When f1 / fw is below the lower limit of formula (9), the refractive power of the first lens group becomes too large, and the magnification chromatic aberration and distortion aberration increase, making it difficult to improve the performance, which is not preferable.

[0060] Note that it is more preferable if the numerical range of formula (9) is as follows.

[0061] 5.96≦f1 / fw≦14.62 (9a) Also, it is even more preferable if the numerical range of formula (9) is as follows.

[0062] 6.49≦f1 / fw≦12.68 (9b) In the stereo optical system of each embodiment, when the focal length of the second lens group L2 is f2, it is preferable to satisfy the condition of the following formula (10).

[0063] -12.61≦f1 / f2≦-4.91 (10) When f1 / f2 exceeds the upper limit of formula (10), the refractive power of the first lens group L1 becomes too small, and the first lens group L1 cannot be miniaturized, which is not preferable. When f1 / f2 is below the lower limit of formula (10), the refractive power of the first lens group L1 becomes too large, and the magnification chromatic aberration and distortion aberration increase, making it difficult to improve the performance, which is not preferable.

[0064] It is more preferable that the numerical range of the formula (10) is as follows.

[0065] -11.20 ≦ f1 / f2 ≦ -5.29 (10a) Also, it is even more preferable that the numerical range of the formula (10) is as follows.

[0066] -9.78 ≦ f1 / f2 ≦ -5.40 (10b) When the focal length of the fourth lens group L4 at the wide-angle end is f4w in the stereo optical system of each embodiment, it is preferable to satisfy the condition of the following formula (11).

[0067] 2.56 ≦ f4w / fw ≦ 6.75 (11) When f4w / fw exceeds the upper limit of the formula (11), the refractive power of the fourth lens group L4 becomes too small and the fourth lens group L4 cannot be miniaturized, which is not preferable. When f4w / fw is below the lower limit of the formula (11), the refractive power of the fourth lens group L4 becomes too large, chromatic aberration of magnification and distortion increase, and it becomes difficult to improve the performance, which is not preferable.

[0068] It is more preferable that the numerical range of the formula (11) is as follows.

[0069] 2.70 ≦ f4w / fw ≦ 5.74 (11a) Also, it is even more preferable that the numerical range of the formula (11) is as follows.

[0070] 2.92 ≦ f4w / fw ≦ 4.98 (11b) Next, the specific configurations of the optical systems of Examples 1 to 6 will be described. Each optical system of each example is composed of a first lens group L1 having a positive refractive power, a second lens group L2 having a negative refractive power, a third lens group L3, and a fourth lens group L4 having a positive refractive power, which are arranged in order from the object side to the image side as described above. The third lens group L3 has a first reflecting surface PR1 on the object side and a second reflecting surface PR2 on the image side. An aperture stop SP is arranged between the first reflecting surface PR1 and the second reflecting surface PR2 in the third lens group L3. The third lens group L3 of each example has a positive refractive power.

[0071] In Examples 1 to 4, when zooming from the wide-angle end to the telephoto end, the first lens group L1 and the third lens group L3 do not move, and the second lens group L2 moves toward the image side. Also, the L4A group, L4B group, and L4C group, which are the fourth sub-lens groups constituting the fourth lens group L4, move toward the object side or the image side, or move along a locus convex toward the object side or a locus convex toward the image side so as to draw mutually different loci. The fourth lens group L4 (each of the L4A group, L4B group, and L4C group) satisfies the conditions of formulas (1) and (2).

[0072] Also, in Examples 5 and 6, when zooming from the wide-angle end to the telephoto end, the first lens group L1 moves along a locus convex toward the image side, the third lens group L3 does not move, and the second lens group L2 moves toward the image side. Also, the L4A group and L4B group, which are the fourth sub-lens groups constituting the fourth lens group L4, move along mutually different loci toward the object side. The fourth lens group L4 (each of the L4A group and L4B group) satisfies the conditions of formulas (1) and (2).

[0073] Note that in Examples 1 to 6, the fourth lens group L4 moves during focusing from infinity to the closest distance.

[0074] Numerical examples 1 to 6 corresponding to Examples 1 to 6 are shown below. 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.

[0075] In the surface data of each numerical example, the surface number i indicates the order of the surface when counted from the object side. r is the radius of curvature (mm) of the i-th surface from the object side, d is the lens thickness or air gap (mm) between the i-th and (i + 1)-th surfaces, nd is the refractive index at the d-line of the optical material between the i-th surface and the (i + 1)-th surface. 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 νd based on the d-line is expressed as νd=(Nd - 1) / (NF - NC), where Nd, NF, and NC are the refractive indices at the d-line (587.6nm), F-line (486.1nm), and C-line (656.3nm) of the Fraunhofer lines, respectively.

[0076] BF represents the back focus (mm). The back focus is the distance on the optical axis from the final surface (the lens surface closest to the image side) of each optical system to the paraxial image plane, expressed in terms of the air-equivalent length. The overall length of the lens is the length obtained by adding the back focus to 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. Among the lens group data, the focal length of L4w means the focal length f4w of the fourth lens group L4 at the wide-angle end.

[0077] The "*" attached to the surface number means that the surface has an aspherical shape. The aspherical shape is expressed by the following formula when 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 direction of light propagation is positive, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, A10 are the aspherical coefficients. "e±Z" in the conic constant and aspherical coefficients means ×10 ±Z means.

[0078] 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 The values corresponding to the conditions of the aforementioned formulas (1) to (11) in Numerical Examples 1 to 6 are summarized in Table 1. Note that Table 1 shows the values at the d-line, which is the reference wavelength. Each numerical example satisfies all the conditions of formulas (1) to (11).

[0079] Figures 1(b), 2(b), 3(b), 4(b), 5(b), and 6(b) respectively show the longitudinal aberration (spherical aberration, astigmatism, distortion, and chromatic aberration) at the wide-angle end in the infinity focus state of each optical system in Numerical Examples 1 to 6. Figures 1(c), 2(c), 3(c), 4(c), 5(c), and 6(c) respectively show the longitudinal aberration at the telephoto end in the infinity focus state of each optical system in Numerical Examples 1 to 6.

[0080] In the spherical aberration diagram, Fno indicates the F-number. The solid line shows the spherical aberration with respect to the d-line (wavelength 587.6 nm), and the one-dot chain line shows the spherical aberration with respect to the g-line (wavelength 435.8 nm). In the astigmatism diagram, the solid line ΔS indicates the astigmatism on the sagittal image plane, and the broken line ΔM indicates the astigmatism on the meridional image plane. The distortion is shown with respect to the d-line. The chromatic aberration diagram shows the lateral chromatic aberration at the g-line. ω is the half field angle (°). [Numerical Example 1] Unit: mm Surface data Surface number r d nd νd 1 70.960 1.40 1.85478 24.8 2 41.105 6.75 1.65160 58.5 3 545.417 0.13 4 50.902 2.72 1.77250 49.6 5 82.654 (Variable) 6* 109.835 0.80 1.85400 40.4 7 11.171 7.11 8 -24.805 0.80 1.65160 58.5 9 33.425 0.20 10 26.597 3.03 1.84666 23.8 11 -333.322 (Variable) 12 ∞ 12.69 1.60311 60.6 13 ∞ 1.00 14 (Diaphragm) ∞ 1.00 15 24.213 1.00 1.77250 49.6 16 12.947 3.67 1.51823 58.9 17 -76.343 1.38 18 ∞ 12.69 1.60311 60.6 19 ∞ (Variable) 20* 17.896 2.82 1.58313 59.4 21 -223.699 0.07 22 61.799 0.80 1.83481 42.7 23 16.759 3.01 1.49700 81.5 24 -44.366 (Variable) 25 32.639 0.79 1.83481 42.7 26 17.139 (Variable) 27 30.205 0.79 1.85150 40.8 28 13.144 0.31 29 13.781 3.90 1.49700 81.5 30 -64.874 (Variable) Image plane ∞ Aspherical data The 6th surface K = 0.00000e+00 A 4= 1.79021e-05 A 6=-2.28987e-08 A 8=-9.85171e-11 A10= 2.62132e-13 The 20th surface K = 0.00000e+00 A 4=-2.53762e-05 A 6= 9.39343e-09 A 8=-3.36281e-10 A10= 2.37435e-13 Various data Zoom ratio 2.92 Wide angle Telephoto Focal length 9.49 27.66 F-number 3.55 4.00 Half angle of view (°) 42.03 17.17 Image height 8.55 8.55 Overall lens length 131.09 131.09 BF 22.09 27.01 d 5 0.50 23.61 d11 26.11 3.00 d19 10.77 0.50 d24 1.57 5.98 d26 1.18 2.11 d30 22.09 27.01 Lens group data Group Starting surface Focal length L1 1 84.06 L2 6 -12.02 L3 12 52.42 L4w 20 37.10 L4A 20 25.74 L4B 25 -44.26 L4C 27 127.13 [Numerical example 2] Unit mm Surface data Surface number r d nd νd 1 92.007 1.40 1.84666 23.8 2 47.964 4.59 1.69680 55.5 3 122.207 0.13 4 44.067 3.91 1.77250 49.6 5 92.340 (Variable) 6* 84.056 1.20 1.85135 40.1 7 12.156 9.30 8 -25.060 0.80 1.65160 58.5 9 54.936 0.20 10 30.941 3.17 1.85478 24.8 11 900.218 (Variable) 12 ∞ 12.88 1.60311 60.6 13 ∞ 2.88 14 (Aperture) ∞ 1.00 15 22.760 1.00 1.85150 40.8 16 15.035 2.49 1.51742 52.4 17 206.824 0.50 18 ∞ 12.88 1.60311 60.6 19 ∞ (Variable) 20* 16.294 2.81 1.58313 59.4 21* 194.929 0.50 22 51.836 3.17 1.57501 41.5 23 -21.849 0.50 24 -25.879 1.00 1.85150 40.8 25 16.661 4.51 1.49700 81.5 26 -16.174 (Variable) 27* -36.831 1.20 1.76802 49.2 28* 63.090 (Variable) 29 94.355 0.79 1.85150 40.8 30 15.448 0.20 31 15.407 4.03 1.49700 81.5 32 -33.625 (Variable) Image plane ∞ Aspherical data The 6th surface K = 0.00000e+00 A 4= 1.98792e-05 A 6=-5.12977e-08 A 8= 1.19023e-10 A10=-1.39437e-13 The 20th surface K = 0.00000e+00 A 4= 3.16475e-05 A 6= 4.91822e-07 A 8=-2.57805e-09 A10=-4.03369e-11 The 21st surface K = 0.00000e+00 A 4= 1.20888e-04 A 6= 7.65121e-07 A 8=-7.08168e-09 A10=-1.61213e-11 The 27th surface K = 0.00000e+00 A 4= 6.98682e-04 A 6=-1.24476e-05 A 8= 1.15600e-07 A10=-1.44487e-10 The 28th surface K = 0.00000e+00 A 4= 7.16637e-04 A 6=-1.04228e-05 A 8= 5.01853e-08 A10= 7.22580e-10 Various data Zoom ratio 4.37 Wide angle Telephoto Focal length 9.49 41.50 F-number 3.85 5.60 Half field angle (°) 42.03 11.64 Image height 8.55 8.55 Overall lens length 156.30 156.30 BF 19.92 13.50 d 5 0.50 33.59 d11 36.15 3.06 d19 18.64 0.50 d26 2.94 5.18 d28 1.11 23.43 d32 19.92 13.50 Lens group data Group Starting surface Focal length L1 1 101.98 L2 6 -13.24 L3 12 75.45 L4w 20 40.04 L4A 20 22.68 L4B 27 -30.12 L4C 29 515.74 [Numerical Example 3] Unit: mm Surface data Surface number r d nd νd 1 102.069 1.40 1.84666 23.8 2 49.796 4.12 1.69680 55.5 3 119.088 0.13 4 43.606 4.16 1.77250 49.6 5 102.177 (variable) 6* 191.960 0.80 1.85150 40.8 7 12.787 7.83 8 -26.768 0.80 1.65160 58.5 9 39.717 0.20 10 30.906 3.29 1.85478 24.8 11 -314.792 (variable) 12 ∞ 15.33 1.60311 60.6 13 ∞ 4.54 14 34.319 1.00 1.85150 40.8 15 17.568 4.05 1.51742 52.4 16 -56.025 5.34 17 (aperture) ∞ 0.50 18 ∞ 15.33 1.60311 60.6 19 ∞ (variable) 20* 21.928 2.68 1.58313 59.4 21 -95.663 4.00 22 68.963 1.00 1.85150 40.8 23 15.007 3.19 1.49700 81.5 24 -70.170 (variable) 25 36.048 0.79 1.80400 46.5 26 20.601 (variable) 27 24.453 0.79 1.85150 40.8 28 12.887 0.27 29 13.304 3.85 1.49700 81.5 30 -95.905 (variable) Image plane ∞ Aspherical data Surface 6 K = 0.00000e+00 A 4= 2.45514e-05 A 6=-5.93442e-08 A 8= 1.15631e-10 A10=-1.26900e-13 Surface 20 K = 0.00000e+00 A 4=-1.10517e-05 A 6= 4.37172e-08 A 8=-8.66814e-10 A10= 4.72732e-12 Various data Zoom ratio 2.91 Wide angle Telephoto Focal length 9.50 27.66 F-number 3.27 4.00 Half field angle (°) 41.98 17.18 Image height 8.55 8.55 Overall lens length 157.50 157.50 BF 22.76 18.81 d 5 0.50 26.02 d11 28.53 3.00 d19 17.74 0.50 d24 1.27 10.74 d26 1.31 13.04 d30 22.76 18.81 Lens group data Group Starting surface Focal length L1 1 101.76 L2 6 -13.22 L3 12 66.61 L4w 20 39.20 L4A 20 34.51 L4B 25 -61.19 L4C 27 84.07 [Numerical Example 4] Unit: mm Surface data Surface number r d nd νd 1 67.518 1.40 1.85478 24.8 2 37.899 6.53 1.69680 55.5 3 148.754 0.30 4 51.376 3.89 1.77250 49.6 5 120.870 (Variable) 6* 86.308 0.80 1.85400 40.4 7 11.675 5.80 8 -41.114 0.80 1.77250 49.6 9 25.244 0.30 10 22.648 2.17 2.00069 25.5 11 48.264 (Variable) 12 246.513 2.17 1.68893 31.1 13 -16.340 1.00 2.00100 29.1 14 -29.961 1.00 15 ∞ 12.35 1.60311 60.6 16 ∞ 2.40 17 (Aperture) ∞ 1.00 18 ∞ 12.35 1.60311 60.6 19 ∞ (Variable) 20* 15.290 3.09 1.58313 59.4 21* -247.681 0.57 22 58.830 0.80 1.71700 47.9 23 11.908 6.44 1.49700 81.5 24 -15.403 (variable) 25 221.388 0.79 1.83481 42.7 26 14.591 (variable) 27 20.787 0.79 2.00069 25.5 28 15.133 0.30 29 14.942 3.97 1.49700 81.5 30 -310.982 (variable) Image plane ∞ Aspherical data The 6th surface K = 0.00000e+00 A 4= 1.26227e-05 A 6=-3.13028e-08 A 8=-2.71222e-11 A10= 1.54592e-13 The 20th surface K = 0.00000e+00 A 4= 3.46778e-05 A 6= 6.66170e-07 A 8=-5.39970e-09 A10= 1.12567e-10 The 21st surface K = 0.00000e+00 A 4= 1.49005e-04 A 6= 8.76476e-07 A 8=-6.22349e-09 A10= 1.31982e-10 Various data Zoom ratio 2.92 Wide angle Telephoto Focal length 9.49 27.66 F number 3.46 4.00 Half field angle (°) 42.03 17.17 Image height 8.55 8.55 Overall lens length 126.15 126.15 BF 20.26 14.65 d 5 1.00 21.49 d11 21.49 1.00 d19 10.38 1.00 d24 1.00 6.89 d26 1.00 10.10 d30 20.26 14.65 Lens group data Group start surface Focal length L1 1 79.54 L2 6 -10.09 L3 12 57.72 L4w 20 28.47 L4A 20 17.08 L4B 25 -18.74 L6C 27 56.90 [Numerical example 5] Unit: mm Surface data Surface number r d nd νd 1 144.838 1.40 2.00069 25.5 2 45.321 6.50 1.65160 58.5 3 -1499.692 0.10 4 40.196 4.46 1.91082 35.2 5 112.258 (Variable) 6* 74.986 0.80 1.85400 40.4 7 9.788 7.95 8 -18.639 0.80 1.75500 52.3 9 37.411 0.52 10 31.164 3.07 1.84666 23.8 11 -40.889 (Variable) 12 ∞ 12.35 1.60311 60.6 13 ∞ 1.94 14(Diaphragm) ∞ 0.83 15 20.460 1.00 1.90043 37.4 16 13.834 4.33 1.48749 70.2 17 -64.755 0.30 18 ∞ 12.35 1.60311 60.6 19 ∞ (Variable) 20* 12.793 5.56 1.58313 59.4 21* -44.483 0.56 22 449.325 0.80 1.85150 40.8 23 9.511 4.80 1.49700 81.5 24 40.349 (Variable) 25 -99.879 2.75 1.51823 58.9 26 -10.958 0.43 27 -10.278 1.00 1.71700 47.9 28 -19.656 (Variable) Image plane ∞ Aspherical data The 6th surface K = 0.00000e+00 A 4= 3.48110e-05 A 6=-1.58823e-07 A 8= 5.07462e-10 A10=-9.45667e-13 The 20th surface K = 0.00000e+00 A 4=-1.41902e-05 A 6= 1.53238e-07 A 8=-2.70259e-09 A10= 4.22423e-11 The 21st surface K = 0.00000e+00 A 4= 5.59996e-05 A 6= 1.52335e-08 A 8=-7.94237e-11 A10= 3.28230e-11 Various data Zoom ratio 2.92 Wide angle Telephoto Focal length 9.49 27.66 F-number 3.61 4.00 Half drawing angle (°) 42.02 17.18 Image height 8.55 8.55 Overall lens length 128.15 128.15 BF 16.32 27.72 d5 0.50 20.68 d11 21.18 1.00 d19 13.21 0.50 d24 2.34 3.65 d28 16.32 27.72 Lens group data Group Starting surface Focal length L1 1 68.40 L2 6 -11.70 L3 12 45.70 L4w 20 38.14 L4A 20 48.97 L4B 25 98.74 [Numerical example 6] Unit: mm Surface data Surface number r d nd νd 1 91.888 1.40 2.00069 25.5 2 47.090 6.75 1.51633 64.1 3 -1258.987 0.13 4 38.679 4.39 1.80400 46.5 5 105.557 (variable) 6* 54.811 0.80 1.85400 40.4 7 9.450 6.56 8 -20.945 0.80 1.75500 52.3 9 34.554 1.54 10 30.437 3.00 1.84666 23.8 11 -69.701 (variable) 12 ∞ 12.35 1.60311 60.6 13 ∞ 0.35 14 (Aperture) ∞ 0.30 15 24.119 1.00 1.85150 40.8 16 13.915 4.26 1.51633 64.1 17 -43.688 2.48 18 ∞ 12.35 1.60311 60.6 19 ∞ (Variable) 20* 17.361 3.38 1.58313 59.4 21 -2140.456 0.05 22 32.099 0.80 1.85150 40.8 23 13.137 3.44 1.49700 81.5 24 -75.609 (Variable) 25 43.571 0.79 1.77250 49.6 26 15.989 1.06 27 35.841 0.79 1.83481 42.7 28 15.881 0.30 29 15.879 3.00 1.49700 81.5 30 -45.290 (Variable) Image plane ∞ Aspherical data The 6th surface K = 0.00000e+00 A 4= 2.21645e-05 A 6=-9.05090e-08 A 8= 2.08340e-10 A10=-5.50415e-13 The 20th surface K = 0.00000e+00 A 4=-2.43104e-05 A 6= 6.87502e-08 A 8=-1.89488e-09 A10= 1.25521e-11 Various data Zoom ratio 2.92 Wide angle Telephoto Focal length 9.49 27.66 F-number 3.82 4.00 Semi-angle (°) 42.03 17.17 Image height 8.55 8.55 Overall lens length 126.06 126.06 BF 19.54 28.32 d5 0.50 21.26 d11 21.76 1.00 d19 11.18 0.50 d24 1.00 2.90 d30 19.54 28.32 Lens group data Group Starting surface Focal length L1 1 68.88 L2 6 -11.42 L3 12 43.70 L4w 20 38.26 L4A 20 25.31 L4B 25 -64.34

[0081]

Table 1

[0082] [Imaging device] Figure 9 shows an imaging device 300 equipped with a stereo optical system according to any one of Examples 1 to 6. The imaging device 300 includes a camera body 320 and a lens device 100 having a stereo optical system according to any one of Examples 1 to 6. The camera body 320 has an imaging element 310 such as a CCD sensor or a CMOS sensor that photoelectrically converts two optical images formed by the stereo optical system (i.e., captures a subject).

[0083] The lens device 100 may be detachable from the camera body 320 or may be provided integrally with the camera body 320. Also, the camera body 320 may be a single-lens reflex camera having a quick-turn mirror, or may be a mirrorless camera without a quick-turn mirror.

[0084] According to the imaging device 300 equipped with the stereo optical system of each embodiment, it is possible to obtain a sufficient zoom ratio and a high-quality captured image (paired parallax images).

[0085] The above embodiments include the following configurations.

[0086] [Configuration 1] A stereo optical system having two zoomable optical systems arranged in parallel, each of the two optical systems is composed of a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group, and a rear group including a fourth lens group, which are arranged in order from the object side to the image side, and the distance between adjacent lens groups changes during zooming, the third lens group 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 and second reflecting surfaces, the optical axis distance between the rear groups is narrower than the optical axis distance between the first lens groups in the two optical systems, when the moving amount during zooming from the wide-angle end to the telephoto end of the fourth lens group is m4 and the focal length of the fourth lens group is f4, 0.16 ≦ |m4 / f4| ≦ 1.28 A stereo optical system characterized by satisfying the above conditions. [Configuration 2] When the imaging magnifications of the second lens group and the fourth lens group in the state of being focused on an object at the wide-angle end and infinity are β2w and β4w respectively, and the imaging magnifications of the second lens group and the fourth lens group in the state of being focused on an object at the telephoto end and infinity are β2t and β4t respectively, Z2 = β2t / β2w Z4 = β4t / β4w when, 0.01 ≦ |Z2 / Z4| ≦ 2.26 The stereo optical system according to Configuration 1, characterized by satisfying the above conditions. [Configuration 3] When the optical axis distance of the first lens group in the two optical systems is Din and the optical interval of the rear group is Dout, 0.01 ≦ Dout / Din ≦ 0.74 The stereoscopic optical system according to Configuration 1 or 2, characterized by satisfying the following conditions. [Configuration 4] The stereoscopic optical system according to any one of Configurations 1 to 3, characterized in that the aperture stop is disposed between the first reflecting surface and the second reflecting surface in the third lens group. [Configuration 5] When the distance on the optical axis from the object-side surface of the most object-side lens in the first lens group at the wide-angle end to the aperture stop is dG1SP, and the distance on the optical axis from the aperture stop to the image plane at the wide-angle end is dSPI, 0.79 ≦ dG1SP / dSPI ≦ 1.50 The stereoscopic optical system according to any one of Configurations 1 to 4, characterized by satisfying the following conditions. [Configuration 6] When the distance on the optical axis from the object-side surface of the most object-side lens in the first lens group at the wide-angle end to the aperture stop is dG1SP, and the focal length of each of the two optical systems at the wide-angle end is fw, 4.28 ≦ dG1SP / fw ≦ 11.32 The stereoscopic optical system according to any one of Configurations 1 to 5, characterized by satisfying the following conditions. [Configuration 7] When the distance on the optical axis from the aperture stop to the image plane at the wide-angle end is dSPI, and the focal length of each of the two optical systems at the wide-angle end is fw, 5.28 ≦ dSPI / fw ≦ 19.09 The stereoscopic optical system according to any one of Configurations 1 to 6, characterized by satisfying the following conditions. [Configuration 8] When the distance on the optical axis from the object-side surface of the most object-side lens in the first lens group at the wide-angle end to the image plane is Lw, and the focal length of each of the two optical systems at the wide-angle end is fw, 9.55 ≦ Lw / fw ≦ 30.18 The stereoscopic optical system according to any one of Configurations 1 to 7, characterized by satisfying the following conditions. [Configuration 9] The third lens group is the stereo optical system according to any one of Configurations 1 to 6, which is characterized by having a positive refractive power. [Configuration 10] When the focal length of the third lens group is f3 and the focal lengths of the two optical systems at the wide-angle end are fw, 3.43 ≤ f3 / fw ≤ 8.46 The stereo optical system according to Configuration 9, which is characterized by satisfying the above condition. [Configuration 11] The third lens group is the stereo optical system according to any one of Configurations 1 to 10, which is characterized by not moving during zooming. [Configuration 12] The first lens group is the stereo optical system according to any one of Configurations 1 to 11, which is characterized by not moving during zooming. [Configuration 13] When the focal length of the first lens group is f1 and the focal lengths of the two optical systems at the wide-angle end are fw, 5.42 ≤ f1 / fw ≤ 17.20 The stereo optical system according to any one of Configurations 1 to 12, which is characterized by satisfying the above condition. [Configuration 14] When the focal length of the first lens group is f1 and the focal length of the second lens group is f2, -12.61 ≤ f1 / f2 ≤ -4.91 The stereo optical system according to any one of Configurations 1 to 13, which is characterized by satisfying the above condition. [Configuration 15] When the focal length of the fourth lens group at the wide-angle end is f4w and the focal lengths of the two optical systems at the wide-angle end are fw, 2.56 ≤ f4w / fw ≤ 6.75 The stereo optical system according to any one of Configurations 1 to 14, which is characterized by satisfying the above condition. [Configuration 16] The stereo optical system according to any one of Configurations 1 to 15, and An imaging device, which is characterized by having an image sensor that images a subject through the stereo optical system.

[0087] Each of the embodiments described above is merely a representative example, and various modifications and changes can be made to each embodiment when implementing the present invention.

Description of Reference Numerals

[0088] L1 First lens group L2 Second lens group L3 Third lens group L4 Fourth lens group L4A (L4s), L4B, L4C Sub-lens groups PR1 First reflecting surface PR2 Second reflecting surface SP Aperture stop

Claims

1. A stereo optical system having two variable magnification optical systems arranged in parallel, each of the two optical systems is composed of a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group, and a rear group including a fourth lens group having positive refractive power as a whole, which are arranged in order from the object side to the image side, and the interval between adjacent lens groups changes during zooming, the third lens group includes a first reflecting surface, a second reflecting surface, and an aperture stop, and the optical axis interval between the rear groups is narrower than the optical axis interval between the first lens groups in the two optical systems due to the bending of the optical path by the first and second reflecting surfaces, when the moving amount during zooming from the wide-angle end to the telephoto end of the fourth lens group is m4 and the focal length of the fourth lens group is f4, 0.16 ≦ |m4 / f4| ≦ 1.28 A stereo optical system characterized by satisfying the condition.

2. The imaging magnifications of the second lens group and the fourth lens group in the state of being focused on an object at the wide-angle end and at infinity are β2w and β4w respectively, and the imaging magnifications of the second lens group and the fourth lens group in the state of being focused on an object at the telephoto end and at infinity are β2t and β4t respectively, Z2 = β2t / β2w Z4 = β4t / β4w when, 0.01 ≦ |Z2 / Z4| ≦ 2.26 The stereo optical system according to claim 1, characterized by satisfying the condition.

3. When the optical axis interval of the first lens group in the two optical systems is Din and the optical interval of the rear group is Dout, 0.01 ≦ Dout / Din ≦ 0.74 The stereo optical system according to claim 1, characterized by satisfying the condition.

4. The stereo 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 group.

5. When the distance on the optical axis from the object-side surface of the most object-side lens in the first lens group at the wide-angle end to the aperture stop is dG1SP, and the distance on the optical axis from the aperture stop to the image plane at the wide-angle end is dSPI, 0.79 ≦ dG1SP / dSPI ≦ 1.50 The stereo optical system according to claim 1, characterized by satisfying the condition.

6. When the distance on the optical axis from the object-side surface of the most object-side lens in the first lens group at the wide-angle end to the aperture stop is dG1SP, and the focal lengths of the two optical systems at the wide-angle end are fw, 4.28 ≤ dG1SP / fw ≤ 11.32 The stereo optical system according to claim 1, characterized by satisfying the condition.

7. When the distance on the optical axis from the aperture stop to the image plane at the wide-angle end is dSPI, and the focal length of each of the two optical systems at the wide-angle end is fw 5.28 ≤ dSPI / fw ≤ 19.09 The stereo optical system according to claim 1, characterized by satisfying the condition.

8. When the distance on the optical axis from the object-side surface of the lens closest to the object in the first lens group at the wide-angle end to the image plane is Lw, and the focal length of each of the two optical systems at the wide-angle end is fw 9.55 ≤ Lw / fw ≤ 30.18 The stereo optical system according to claim 1, characterized by satisfying the condition.

9. The stereo optical system according to claim 1, characterized in that the third lens group has a positive refractive power.

10. When the focal length of the third lens group is f3, and the focal length of each of the two optical systems at the wide-angle end is fw 3.43 ≤ f3 / fw ≤ 8.46 The stereo optical system according to claim 9, characterized by satisfying the condition.

11. The stereo optical system according to claim 1, characterized in that the third lens group does not move during zooming.

12. The stereo optical system according to claim 1, characterized in that the first lens group does not move during zooming.

13. When the focal length of the first lens group is f1, and the focal length of each of the two optical systems at the wide-angle end is fw 5.42 ≤ f1 / fw ≤ 17.20 The stereo optical system according to claim 1, characterized by satisfying the condition.

14. When the focal length of the first lens group is f1, and the focal length of the second lens group is f2 -12.61 ≤ f1 / f2 ≤ -4.91 The stereo optical system according to claim 1, characterized by satisfying the condition.

15. When the focal length of the fourth lens group at the wide-angle end is f4w, and the focal length of each of the two optical systems at the wide-angle end is fw 2.56 ≤ f4w / fw ≤ 6.75 The stereo optical system according to claim 1, characterized by satisfying the condition.

16. An imaging device, comprising the stereo optical system according to any one of claims 1 to 15, and an imaging element that images an object through the stereo optical system.

Images