Stereo imaging system, stereo optical system, and imaging device

Abstract

When arranging two optical systems in parallel for stereo imaging, miniaturization is required while avoiding interference between image sensors. [Solution] The stereo imaging system 10 comprises two imaging devices 11 and 12, each having an optical system including a first lens group L1, arranged so that the first lens groups are in parallel. The optical system of each of the two imaging devices includes a first optical element 121 that bends the optical path from the first lens group, a second optical element 122 positioned on the image side of the first optical element and branching the optical path into multiple optical paths, a first lens group L1 positioned on the object side of the first optical element and having refractive power, and second lens groups L21 and L22 with positive refractive power, respectively, positioned on the multiple optical paths branched toward multiple imaging planes by the second optical element. Each first lens group includes an aperture diaphragm S and a focus group L1A.

Description

[Technical Field]

[0001] This invention relates to an optical system suitable for stereo imaging. [Background technology]

[0002] As an optical system used for imaging, Patent Document 1 discloses an optical system that uses an optical path separation element to guide light from a subject to multiple image sensors. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2010-160312 [Overview of the project] [Problems that the invention aims to solve]

[0004] When arranging two such optical systems in parallel for stereo imaging, miniaturization of the optical system is required while avoiding interference between the image sensors. [Means for solving the problem]

[0005] One aspect of the present invention is a stereo imaging system comprising two imaging devices, each having an optical system including a first lens group, arranged so that the first lens groups are in parallel. The optical system of each of the two imaging devices includes a first optical element that bends the optical path from the first lens group, a second optical element positioned on the image side of the first optical element that branches the optical path into multiple optical paths, and a second lens group with positive refractive power, each positioned on the multiple optical paths branched by the second optical element toward multiple imaging planes. Each of the first lens groups of the two imaging devices is characterized by having an aperture diaphragm and a focus group that moves during focusing.

[0006] Another aspect of the present invention is a stereo optical system, which has two optical systems, each including a first lens group, and the first lens groups are arranged in parallel. Each of the two optical systems includes a first optical element that bends the optical path from the first lens group, a second optical element positioned on the image side of the first optical element that branches the optical path into multiple optical paths, and a second lens group with positive refractive power, each positioned on the multiple optical paths branched toward multiple image planes by the second optical element. Each of the first lens groups in the two optical systems is characterized by having an aperture diaphragm and a focus group that moves during focusing. An imaging device having the above stereo optical system also constitutes another aspect of the present invention. [Effects of the Invention]

[0007] According to the present invention, a compact stereo optical system and a stereo imaging device can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] A diagram showing the configuration of a stereo imaging system as an example. [Figure 2] A diagram showing the configuration of another imaging system as an example. [Figure 3] Cross-sectional view and aberration diagram of the optical system of Example 1. [Figure 4] Cross-sectional view and aberration diagram of the optical system of Example 2. [Figure 5] Cross-sectional view and aberration diagram of the optical system of Example 3. [Modes for carrying out the invention]

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

[0010] Figure 1(A) shows the configuration of a stereo imaging system (hereinafter simply referred to as the imaging system) 10 using the optical systems of Examples 1 to 3 described later. The imaging system 10 is used for stereoscopic imaging and consists of imaging devices 11 and 12 arranged so that their respective optical systems have parallax with each other. This imaging system 10 can be used for various imaging applications such as general-purpose imaging, broadcast imaging, cinema imaging, surveillance imaging, and in-vehicle imaging.

[0011] Each imaging device 11 and 12 simultaneously images the same subject by directing light from the subject to multiple image sensors via an optical system. By combining the multiple images obtained by simultaneously imaging the same subject in each imaging device, high-resolution composite images and composite images with a wide dynamic range can be generated. Because the images generated by imaging devices 11 and 12 have parallax with each other, these captured images can be viewed in 3D.

[0012] The optical system of each imaging device has a first lens group L1 closest to the object. The first lens groups L1 of imaging devices 11 and 12 are arranged in parallel so that their optical axes are parallel to each other at a predetermined interval (baseline length).

[0013] Furthermore, the optical system of each imaging device includes one or more first optical elements 121 that bend the optical path (i.e., the optical axis of the optical system) from the first lens group, and one or more second optical elements 122 that are positioned closer to the image than all the first optical elements and branch the optical path (optical axis) to lead to multiple imaging planes (image sensors 131, 132). The one or more first optical elements include the first optical element closest to the object, and the one or more second optical elements include the second optical element closest to the image. Figure 1(A) shows an optical system having one (closest to the object) first optical element 121 and one (closest to the image) second optical element 122.

[0014] In the first optical element, the surface that bends the optical path by reflection or the like is called a bending surface, and in the second optical element, the surface that branches the optical path by transmission, reflection, or the like is called a branching surface. The bending direction of the optical path at the bending surface or the branching direction of the optical path at the branching surface may be perpendicular to the original optical path or deviate from the perpendicular direction.

[0015] Each optical system also has a second - 1 lens group (second lens group) L21 with positive refractive power, which is arranged on the first optical path branched by the second optical element 122 toward the imaging element 131 on the most image - side. Further, the optical system has a second - 2 lens group (second lens group) L22 with positive refractive power, which is arranged on the second optical path branched by the second optical element 122 toward the imaging element 132 on the most image - side. The imaging elements 131 and 132 are arranged such that their imaging surfaces (light - receiving surfaces) are located on the image surface on the image - side of the second - 1 lens group L21 and the second - 2 lens group L22. The lens group includes one or more lenses.

[0016] The optical systems of each of the imaging devices 11 and 12 have the same configuration as each other, except for the bending direction of the optical path by the first optical element 121 and the branching direction of the optical path by the second optical element 122. In the optical systems of each of the imaging devices 11 and 12, by bending the optical path on the image - side of the first optical element 121 in opposite directions to each other and then branching the optical path by the second optical element 122, interference between the imaging elements can be avoided. Also, by branching a part of the image - side of each optical system, a small - sized imaging system can be configured.

[0017] Since the second - 1 lens group L21 and the second - 2 lens group L22 have positive refractive power, the optical path length from the first optical element 122 to the imaging element 131 can be increased. As a result, the distance between the imaging element 131 and the imaging element 132 can be increased to avoid their interference.

[0018] The first lens group L1 includes an aperture stop S and a first sub-lens group L1A as a focus group that moves along the optical axis during focusing. A sub-lens group is a collection of one or more lenses that move so as to change the distance between adjacent sub-lens groups during focusing. By disposing the aperture stop S and the first sub-lens group L1A on the object side of the first optical element 121, it is possible to dispense with aperture adjustment and focusing for each imaging element, and simplify the configuration of the imaging device.

[0019] Note that the first optical element may be a prism having a reflecting surface as shown in FIG. 1(A), or may be a mirror. Also, the second optical element may be a beam splitter as a prism as shown in FIG. 1(A), or may be a half mirror. Furthermore, it may be an element that branches the optical path according to wavelength, such as a color separation prism or a dichroic mirror. By using an element that branches the optical path according to wavelength (color) and imaging with imaging elements provided for each color like a so-called three-plate camera, a higher-resolution color composite image can be obtained compared to the case of imaging without separating wavelengths.

[0020] The optical path of the light that forms an image on the imaging element 131 through the second-1 lens group L21 is bent twice in total by the first optical element 121 and the second optical element 122. On the other hand, the optical path of the light that forms an image on the imaging element 132 through the second-2 lens group L22 is bent only once by the first optical element 121. Therefore, the subject image formed on the imaging element 131 and the subject image formed on the imaging element 132 are images that are inverted with respect to each other. Therefore, it is preferable to perform image processing for inverting one of the imaging images obtained by the imaging element 131 and the imaging image obtained by the imaging element 132 to align the orientations of these imaging images.

[0021] Figure 1(B) shows an imaging device 11 using an optical system with a different configuration than that of Figure 1(A), viewed from the same direction as Figure 1(A) (a direction perpendicular to the optical axis of the first lens group L1). Figure 1(C) shows the imaging device 11 of Figure 1(B) viewed from the object side in the direction of the optical axis of the first lens group L1. The optical systems shown in Figures 1(B) and (C) have the same components as the optical system of Figure 1(A), but the bending direction of the optical path of the second optical element 122 is different from that of Figure 1(A), and as a result, the orientation of the optical axis of the second-second lens group L22 (position of the image sensor 132) is different from that of Figure 1(A).

[0022] Figure 2(A) shows an imaging device 11 using an optical system with a different configuration from that of Figure 1(A), viewed from the same direction as Figure 1(A). Figure 2(B) shows the imaging device 11 of Figure 2(A) viewed from the object side in the optical axis direction of the first lens group L1. The optical systems shown in Figures 2(A) and (B) have one first optical element 121 and two second optical elements 122 and 123, which branch the optical path into three. Specifically, another second optical element 123 is placed between the first optical element 121 and the second optical element 122. In order to make the optical path lengths equal between the optical path passing through the second optical element 123 and the second optical element 122 and the optical path that does not pass through the second optical element 122, a glass block 124 is provided on the image side of the second optical element 122.

[0023] Although Figures 2(A) and (B) show a configuration with multiple (two) second optical elements 122 and 123, a configuration with multiple first optical elements 121 may also be adopted.

[0024] Figures 3(A) and 4(A) show cross-sections along the optical axis of the optical systems of Example 1 and Example 2, respectively, when in focus on an object at infinity (hereinafter referred to as the infinity focus state). The optical systems of Examples 1 and 2 have a first lens group L1 with positive refractive power, a first optical element 121, a second optical element 122, and a second-first lens group L21 with positive refractive power in the optical path not bent by the second optical element 122, arranged in order from the object side to the image side. Light emitted from the second-first lens group L21 is imaged on the image sensor 131. Although not shown, the second-second lens group L22 with positive refractive power in the optical path bent by the second optical element 122 has the same configuration as the second-first lens group L21, and light emitted from the second-second lens group L22 is imaged on the image sensor 132. The first lens group L1 includes an aperture diaphragm S and a first sub-lens group L1A.

[0025] Following the description of the optical system of Example 3, which will be discussed later, numerical examples 1 to 3 corresponding to Examples 1 to 3 are shown. Figures 3(B) and 4(B) show the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the optical systems of numerical example 1 and numerical example 2 at infinity focus, respectively. In the spherical aberration diagram, Fno indicates the F number, the solid line shows the spherical aberration at the d line (wavelength 587.6 nm), and the dashed line shows the spherical aberration at the g line (wavelength 435.8 nm). In the astigmatism diagram, the solid line S shows the astigmatism at the sagittal image plane, and the dashed line M shows the astigmatism at the meridional image plane. The distortion diagram shows the distortion at the d line. The chromatic aberration diagram shows the lateral chromatic aberration at the g line. ω is the half-angle of view (°).

[0026] Figure 5(A) shows a cross-section along the optical axis of the optical system of Example 3 in the infinity focus state. The optical system of Example 3 has, arranged in order from the object side to the image side, a first lens group L1 with negative refractive power, a first optical element 121, an intermediate lens group LM with positive refractive power, a second optical element 122, and a second-first lens group L21 with positive refractive power on the optical path that is not bent by the second optical element 122. Light emitted from the second-first lens group L21 is imaged on the image sensor 131. Although not shown, the second-second lens group L22 with positive refractive power on the optical path bent by the second optical element 122 has the same configuration as the second-first lens group L21, and light emitted from the second-second lens group L22 is imaged on the image sensor 132. The first lens group L1 has an aperture diaphragm S and a first sub-lens group L1A.

[0027] By arranging the intermediate lens group LM between the first optical element 121 and the second optical element 122, the second-first lens group L21 and the second-second lens group L22 can be miniaturized, resulting in a compact imaging device overall.

[0028] Figure 5(B) shows the longitudinal aberration of the optical system of numerical example 3 when it is in focus at infinity.

[0029] In each embodiment (each numerical example), the optical system preferably satisfies the following condition (1), where D1 is the distance along the optical axis from the lens surface closest to the object in the first lens group L1 to the lens surface closest to the image in the first lens group L1, and f is the focal length of the entire optical system.

[0030] 7.50 ≤ D1 / f ≤ 16.00 (1) If D1 / f falls below the lower limit of equation (1), it becomes difficult to arrange the aperture diaphragm S and the first sub-lens group L1A, which is the focusing group, in the first lens group L1, which is undesirable. If D1 / f exceeds the upper limit of equation (1), the diameter of the lens closest to the object becomes large, causing interference between the lenses closest to the object in the imaging devices 11 and 12, which is also undesirable.

[0031] Furthermore, it is more preferable to set the lower limit of equation (1) to 7.80, 8.00, or 8.20 (6.76 3.47). Also, it is more preferable to set the upper limit of equation (1) to 15.00, 14.00, or 13.00 (19.35 21.59).

[0032] Furthermore, it is preferable that the optical system of each embodiment satisfies the following condition (2) when the focal length of the second-first lens group L21 and the second-second lens group L22 is f2.

[0033] 5.71 ≤ f² / f ≤ 7.82 (2) If f2 / f falls below the lower limit of equation (2), the refractive power of the second-first lens group L21 and the second-second lens group L22 becomes too large, making it difficult to correct the chromatic aberration and field curvature occurring in the first lens group L1, which is undesirable. If f2 / f exceeds the upper limit of equation (2), it becomes difficult to correct the various aberrations occurring in the first lens group L1, which is also undesirable.

[0034] Furthermore, it is more preferable to set the lower limit of equation (2) to 5.90, 6.10, or 6.30 (5.04 2.66). Also, it is more preferable to set the upper limit of equation (2) to 7.40, 7.00, or 6.80 (8.91 9.64).

[0035] Furthermore, it is preferable that the optical system of each embodiment satisfies the following condition (3), when D2 is the distance along the optical axis from the branching surface of the second optical element 122 to the imaging surface (image plane).

[0036] 5.00 ≤ D2 / f ≤ 7.44 (3) It is preferable that D2 / f falls below the lower limit of equation (3), as this is undesirable because the distance from the bifurcation surface to the imaging surface becomes too short, causing the image sensors 131 and 132 to interfere with each other. It is also undesirable that D2 / f exceeds the upper limit of equation (3), as this causes the distance from the bifurcation surface to the imaging surface to become too long, resulting in a larger imaging device.

[0037] Furthermore, it is more preferable to set the lower limit of equation (3) to 5.20, 5.40, or 5.60 (4.37 2.19). Also, it is more preferable to set the upper limit of equation (3) to 7.30, 7.20, or 7.00 (7.89 8.19).

[0038] Furthermore, in each embodiment, it is preferable that the optical system satisfies the following condition (4), where DM is the distance along the optical axis from the bending surface of the first optical element 121 to the branching surface of the second optical element 122.

[0039] 2.47 ≤ DM / f ≤ 8.22 (4) If DM / f falls below the lower limit of equation (4), the first optical element 121 and the second optical element 122 will interfere with each other, which is undesirable. If DM / f exceeds the upper limit of equation (4), the distance from the first optical element 121 to the second optical element 122 will become too long, which is undesirable because the imaging device will become larger.

[0040] Furthermore, it is more preferable to set the lower limit of equation (4) to 2.60, 2.80, or 2.90 (2.01 0.83). Also, it is more preferable to set the upper limit of equation (4) to 7.80, 7.50, 7.00, or 6.40 (10.30 11.69).

[0041] Furthermore, it is preferable that the optical system of each embodiment satisfies the following condition (5), where DS is the distance along the optical axis from the aperture diaphragm S to the imaging plane (image plane).

[0042] 11.87 ≤ DS / f ≤ 20.01 (5) If DS / f falls below the lower limit of equation (5), it becomes difficult to position the aperture diaphragm S closer to the object than the first optical element 121, which is undesirable. If DS / f exceeds the upper limit of equation (5), the distance between the aperture diaphragm S and the second-first lens group L21 and the second-second lens group L22 becomes too long, causing the diameters of the second-first lens group L2-1 and the second-second lens group L22 to increase. As a result, the imaging device becomes larger, which is undesirable.

[0043] Furthermore, it is more preferable to set the lower limit of equation (5) to 12.00, 12.20, or 12.40 (11.27 7.97). Also, it is more preferable to set the upper limit of equation (5) to 18.00, 17.00, or 16.00 (23.53 25.89).

[0044] The above describes a case in which an imaging system is configured using two imaging devices, each having an optical system that satisfies the above configuration and conditions. However, it is also possible to configure a stereo optical system and an integrated imaging device having the same, each including two optical systems that satisfy the above configuration and conditions. In this case, the stereo optical system consists of two optical systems, each including a first lens group, arranged so that the first lens groups are in parallel. Each of the two optical systems includes one or more first optical elements that bend the optical path from the first lens group, and a second optical element that is positioned closer to the image than the first optical element closest to the image, and that branches the optical path into multiple optical paths. Each first lens group includes an aperture diaphragm S and a focus group.

[0045] Numerical examples 1 to 3 are shown below. In each numerical example, the surface number i indicates the order of the surfaces when counted from the object side. r is the radius of curvature (mm) of the i-th surface from the object side, d is the lens thickness or air gap on the optical axis between the i-th and (i+1)-th surfaces (mm), and nd is the refractive index of the optical material at the d-line between the i-th and (i+1)-th surfaces. νd is the Abbe number with respect to the d-line of the optical material between the i-th and (i+1)-th surfaces. The Abbe number νd with respect to the d-line is expressed as νd = (Nd-1) / (NF-NC), where Nd, NF, and NC are the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm), respectively.

[0046] d, focal length (mm), F-number, and half-angle of view (°) are all values ​​when the lens is in focus at infinity. BF represents the back focus (mm). Back focus is the distance along the optical axis from the image-side lens surface (final surface) of the optical system to the paraxial image plane, expressed in terms of air equivalent length. The total length of the lens is the distance along the optical axis from the object-side lens surface (frontmost surface) to the final surface of the optical system, plus the back focus.

[0047] 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 taken as positive, R is the paraxial curvature radius, K is the conic constant, and A4, A6, A8, A10 are aspherical coefficients. "e±xx" of the conic constant and aspherical coefficients means ×10 , , means.

[0048] X = (H 2 / R) / [1 + {1 - (1 + K)(H / R) 2} 1 / 2 + A4×h 4 + A6×h 6 + A8×h 8 + A10×h 10 + A12×h 12 [Numerical Example 1] Unit: mm Surface Data Surface Number r d nd νd 1 58.960 2.50 2.00100 29.1 2 19.260 12.58 3 128.130 2.00 2.00069 25.5 4 35.789 7.47 5 -35.180 1.50 2.00100 29.1 6 35.840​​​​​​​​​​​​​​​​14 35.263 6.79 1.51742 52.4 15 -21.761 9.61 16 (aperture) ∞ 2.00 17 182.035 4.21 1.71736 29.5 18 -39.049 2.00 19 ∞ 16.04 1.51633 64.1 20 ∞ 16.04 1.51633 64.1 21 ∞ 16.04 1.51633 64.1 22 ∞ 16.04 1.51633 64.1 23 ∞ 1.00 24 25.707 14.34 1.43875 94.7 25 -56.775 0.46 26 -66.697 1.70 2.00100 29.1 27 24.577 11.14 1.43875 94.7 28 -85.408 0.20 29 65.673 7.80 1.43875 94.7 30 -231.395 0.20 31 31.585 16.16 1.43875 94.7 32 -39.217 1.70 1.87070 40.7 33 -106.953 15.07 Image plane ∞ Aspherical data Page 13 K = 0.00000e+00 A 4= 9.63772e-06 A 6= 3.80437e-08 A 8= 4.11555e-13 A10 = -3.99834e-14 Various data Focal length 10.90 F-number 2.91 Half-angle (°): 95.00 Image height 18.00 Lens length: 225.60 BF 15.07 Lens group data Group Starting plane Ending plane Focal length L1 1 18 24.64 L1A 10 12 49.16 L2-1 24 33 69.68 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd 1 61.892 2.50 2.00100 29.1 2 18.845 12.30 3 96.205 2.00 2.00100 29.1 4 33.863 9.08 5 -25.497 1.50 1.80400 46.5 6 55.942 1.39 7 107.758 10.22 1.84666 23.8 8 -28.587 5.75 9 1065.446 1.50 2.00100 29.1 10 22.701 8.60 1.53172 48.8 11 -107.956 4.29 12 4355.929 9.58 1.53172 48.8 13 -14.863 1.50 1.72916 54.7 14 -20.340 3.62 15* -17.902 1.05 2.00100 29.1 16 75.458 7.44 1.51742 52.4 17 -19.147 10.00 18 192.746 2.00 2.00069 25.5 19 60.263 10.13 1.72825 28.5 20 -37.726 2.00 21 (aperture) ∞ 2.00 22 ∞ 16.74 1.51633 64.1 23 ∞ 16.74 1.51633 64.1 24 ∞ 16.74 1.51633 64.1 25 ∞ 16.74 1.51633 64.1 26 ∞ 16.74 1.51633 64.1 27 ∞ 16.74 1.51633 64.1 28 ∞ 1.00 29 25.774 11.39 1.43875 94.7 30 -83.126 0.15 31 -144.020 2.00 2.00100 29.1 32 31.298 2.07 33 44.533 13.15 1.43875 94.7 34 -24.083 2.00 1.87070 40.7 35 -119.868 0.20 36 147.604 9.71 1.43875 94.7 37 -35.095 0.20 38 38.964 17.12 1.43875 94.7 39 -28.428 1.70 1.87070 40.7 40 -57.958 15.07 Image plane ∞ Aspherical data Page 15 K = 0.00000e+00 A 4= 4.41006e-06 A 6= 3.09378e-08 A 8= 2.42081e-11 A10 = 5.76305e-13 Various data Focal length 10.90 F-number 2.91 Half-angle (°): 95.00 Image height 18.00 Lens length: 284.68 BF 15.07 Lens group data Group Starting plane Ending plane Focal length L1 1 21 17.79 L1A 12 14 43.33 L2-1 29 40 73.36 [Numerical Example 3] Unit: mm Surface data Face number rd nd νd 1 43.749 1.95 2.00100 29.1 2 14.861 8.41 3* -174.867 1.30 2.00100 29.1 4 24.881 6.96 5 -16.683 1.30 2.00100 29.1 6 -296.826 0.37 7 -180.603 9.76 1.75211 25.0 8 -19.291 0.19 9 58.407 1.30 1.96300 24.1 10 29.267 1.80 11 32.899 11.99 1.53172 48.8 12 -17.423 1.30 1.49700 81.5 13 -46.042 0.65 14* 69.188 4.78 1.62041 60.3 15 -36.922 0.98 1.51633 64.1 16 49.355 24.47 17 (aperture) ∞ 1.95 18 ∞ 8.83 1.51633 64.1 19 ∞ 8.83 1.51633 64.1 20 ∞ 1.30 21 35.125 0.97 1.65160 58.5 22 15.583 3.28 1.49700 81.5 23 -49.533 0.19 24 ∞ 8.83 1.51633 64.1 25 ∞ 8.83 1.51633 64.1 26 ∞ 6.48 27 26.820 5.77 1.43875 94.7 28 -22.721 0.19 29 -75.166 4.18 1.43875 94.7 30 -16.807 1.30 1.87070 40.7 31 21.259 0.48 32 22.993 6.01 1.43875 94.7 33 -42.175 0.19 34 20.791 11.66 1.43875 94.7 35 -18.205 1.10 1.95375 32.3 36 -28.909 8.77 Image plane ∞ Aspherical data 3rd page K = 0.00000e+00 A 4= 4.36079e-06 A 6=-5.43863e-08 A 8= 1.42166e-10 A10 = -1.96625e-13 Side 14 K = 0.00000e+00 A 4=-1.52652e-06 A 6= 9.29124e-09 A 8=-3.92721e-11 A10 = 8.37057e-14 Various data Focal length 7.05 F-number 2.91 Half-angle (°): 95.00 Image height 11.70 Lens length: 166.71 BF 8.77 Lens group data Group Starting plane Ending plane Focal length L1 1 17 -45.66 L1A 14 16 622.90 LM 21 23 54.14 L2-1 27 36 47.41 The values ​​of equations (1) to (5) for numerical examples 1 to 3 are summarized in Table 1. The optical systems in each numerical example satisfy all the conditions of equations (1) to (5).

[0049] [Table 1]

[0050] The above embodiments include the following configuration.

[0051] (Composition 1) A stereo imaging system comprising two imaging devices, each having an optical system including a first lens group, arranged such that the first lens groups are in parallel, The optical systems of each of the two imaging devices are A first optical element that bends the optical path from the first lens group, A second optical element is positioned closer to the image than the first optical element and branches the optical path into multiple optical paths, The system comprises a group of second lenses with positive refractive power, each arranged on a plurality of optical paths branched toward a plurality of imaging surfaces by the second optical element, A stereo imaging system characterized in that each of the two imaging devices has a first lens group, each of which has an aperture diaphragm and a focus group that moves during focusing. (Configuration 2) The stereo imaging system according to configuration 1, characterized in that the two imaging devices are arranged such that the direction in which the first optical element in each of the optical systems bends the optical path is in opposite directions to each other. (Composition 3) When D1 is the distance along the optical axis from the lens surface closest to the object in the first lens group to the lens surface closest to the image in the first lens group, and f is the focal length of the optical system, 7.50 ≤ D1 / f ≤ 16.00 A stereo imaging system according to configuration 1 or 2, characterized by satisfying the following conditions. (Composition 4) When the focal length of the second lens group is f2 and the focal length of the optical system is f, 5.71 ≤ f² / f ≤ 7.82 A stereo imaging system according to any one of configurations 1 to 3, characterized by satisfying the following conditions. (Composition 5) When D2 is the distance along the optical axis from the surface that branches the optical path toward the plurality of imaging surfaces in the second optical element to each of the plurality of imaging surfaces, and f is the focal length of the optical system, 5.00 ≤ D2 / f ≤ 7.44 A stereo imaging system according to any one of configurations 1 to 4, characterized in that it satisfies the following conditions. (Composition 6) When DM is the distance along the optical axis from the surface in the first optical element that bends the optical path to the surface in the second optical element that branches the optical path, and f is the focal length of the optical system, 2.47 ≤ DM / f ≤ 8.22 A stereo imaging system according to any one of configurations 1 to 5, characterized in that it satisfies the following conditions. (Composition 7) When DS is the distance along the optical axis from the aperture diaphragm to the imaging plane, and f is the focal length of the optical system, 11.87 ≤ DS / f ≤ 20.01 A stereo imaging system according to any one of configurations 1 to 6, characterized in that it satisfies the following conditions. (Composition 8) A stereo imaging system comprising two imaging devices, each having an optical system including a first lens group, arranged such that the first lens groups are in parallel, The optical systems of the two imaging devices are, A first optical element that bends the optical path from the first lens group, A stereo imaging system characterized by having a second optical element positioned closer to the image than the first optical element, which branches the optical path into multiple optical paths toward multiple imaging surfaces. (Composition 9) A stereo optical system having two optical systems, each including a first lens group, and arranged so that the first lens groups are in parallel, The two aforementioned optical systems are, A first optical element that bends the optical path from the first lens group, A second optical element is positioned closer to the image than the first optical element and branches the optical path into multiple optical paths, The device comprises a group of second lenses with positive refractive power, each arranged on a plurality of optical paths branched toward a plurality of image planes by the second optical element, A stereo optical system characterized in that each of the two optical systems has a first lens group, an aperture diaphragm, and a focus group that moves during focusing. (Composition 10) The stereo optical system according to configuration 9, characterized in that the direction in which the first optical element in each of the two optical systems bends the optical path is in opposite directions. (Composition 11) A stereo optical system having two optical systems, each including a first lens group, and arranged so that the first lens groups are in parallel, The two aforementioned optical systems are, A first optical element that bends the optical path from the first lens group, A stereo optical system characterized by having a second optical element positioned closer to the image than the first optical element, which branches the optical path into multiple optical paths toward multiple image planes. (Composition 12) An imaging apparatus characterized by having a stereo optical system as described in any one of configurations 9 to 11.

[0052] The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention. [Explanation of Symbols]

[0053] L1 First lens group L1A First sub-lens group (focusing group) L21 2-1 lens group L22 2nd-2nd lens group 121 First optical elements 122 Second Optical Related 131,132 Image sensors S Aperture diaphragm

Claims

1. A stereo imaging system comprising two imaging devices, each having an optical system including a first lens group, arranged such that the first lens groups are in parallel, The optical systems of each of the two imaging devices are A first optical element that bends the optical path from the first lens group, A second optical element is positioned closer to the image than the first optical element and branches the optical path into multiple optical paths, The device comprises a group of second lenses with positive refractive power, each arranged on a plurality of optical paths branched toward a plurality of imaging surfaces by the second optical element, A stereo imaging system characterized in that each of the two imaging devices has a first lens group, each of which has an aperture diaphragm and a focus group that moves during focusing.

2. The stereo imaging system according to claim 1, characterized in that the two imaging devices are arranged such that the direction in which the first optical element in each of the optical systems bends the optical path is in opposite directions to each other.

3. When D1 is the distance along the optical axis from the lens surface closest to the object in the first lens group to the lens surface closest to the image in the first lens group, and f is the focal length of the optical system, 7.50 ≤ D1 / f ≤ 16.00 The stereo imaging system according to claim 1, characterized in that it satisfies the following conditions.

4. When the focal length of the second lens group is f2 and the focal length of the optical system is f, 5.71 ≤ f² / f ≤ 7.82 The stereo imaging system according to claim 1, characterized in that it satisfies the following conditions.

5. When D2 is the distance along the optical axis from the surface that branches the optical path toward the plurality of imaging surfaces in the second optical element to each of the plurality of imaging surfaces, and f is the focal length of the optical system, 5.00 ≤ D² / f ≤ 7.44 The stereo imaging system according to claim 1, characterized in that it satisfies the following conditions.

6. When DM is the distance along the optical axis from the surface in the first optical element that bends the optical path to the surface in the second optical element that branches the optical path, and f is the focal length of the optical system, 2.47 ≤ DM / f ≤ 8.22 The stereo imaging system according to claim 1, characterized in that it satisfies the following conditions.

7. When DS is the distance along the optical axis from the aperture diaphragm to the imaging plane, and f is the focal length of the optical system, 11.87 ≤ DS / f ≤ 20.01 The stereo imaging system according to claim 1, characterized in that it satisfies the following conditions.

8. A stereo imaging system comprising two imaging devices, each having an optical system including a first lens group, arranged such that the first lens groups are in parallel, The optical systems of the two imaging devices are, A first optical element that bends the optical path from the first lens group, A stereo imaging system characterized by having a second optical element positioned closer to the image than the first optical element, which branches the optical path into multiple optical paths toward multiple imaging surfaces.

9. A stereo optical system having two optical systems, each including a first lens group, and arranged so that the first lens groups are in parallel, The two optical systems described above are, A first optical element that bends the optical path from the first lens group, A second optical element is positioned closer to the image than the first optical element and branches the optical path into multiple optical paths, The device comprises a group of second lenses with positive refractive power, each arranged on a plurality of optical paths branched toward a plurality of image planes by the second optical element, A stereo optical system characterized in that each of the two optical systems has a first lens group, an aperture diaphragm, and a focus group that moves during focusing.

10. The stereo optical system according to claim 9, characterized in that the direction in which the first optical element in each of the two optical systems bends the optical path is in opposite directions.

11. A stereo optical system having two optical systems, each including a first lens group, and arranged so that the first lens groups are in parallel, The two optical systems described above are, A first optical element that bends the optical path from the first lens group, A stereo optical system characterized by having a second optical element positioned closer to the image than the first optical element, which branches the optical path into multiple optical paths toward multiple image planes.

12. An imaging device characterized by having a stereo optical system as described in any one of claims 9 to 11.

Images