Stereo optical system and imaging device

Abstract

To provide a stereo optical system which has a variable range of a sufficient base line length, and with which a change of image quality due to a change of the base line length is small.SOLUTION: A stereo optical system L0 comprises two optical systems LR, LL that are juxtaposed, each of the two optical systems having a first group L1 including at least one lens and a first reflection surface RS1, and a second reflection surface RS2 for reflecting light toward the image side that has entered the first group from the object side and then reflected at the first reflection surface, with the interval between the second reflection surfaces being narrower than the base line length between the first groups of the two optical systems. The base line length can be varied by changing the distance on optical axis between the first reflection surface and the second reflection surface in at least one of the two optical systems.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In a stereo optical system in which two optical systems are arranged in parallel with a baseline length, which is the distance between their optical axes, the three-dimensional effect of the stereoscopically viewed image changes when the baseline length changes. Patent Document 1 discloses a stereo optical system in which the baseline length can be changed by driving the diaphragms arranged in each of the two optical systems.

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, since the aperture diameter of the diaphragm changes when the baseline length is changed, the brightness and image quality of the image change. In addition, the variable range of the baseline length is narrow.

[0005] The present invention provides a stereo optical system having a sufficient variable range of the baseline length and little change in image quality even when the baseline length changes.

Means for Solving the Problems

[0006] As one aspect of the present invention, a stereo optical system has two optical systems arranged in parallel. Each of the two optical systems includes a first group including at least one lens and a first reflecting surface, and a second reflecting surface that reflects the light incident on the first group from the object side and reflected by the first reflecting surface to the image side. The distance between the second reflecting surfaces is narrower than the baseline length between the first groups in the two optical systems. The baseline length is variable by changing the distance on the optical axis between the first reflecting surface and the second reflecting surface in at least one of the two optical systems. Note that an imaging device including the above stereo optical system also constitutes another aspect of the present invention.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a stereo optical system having a sufficient variable range of baseline length and little change in image quality even when the baseline length changes.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, using FIGS. 1 to 3 showing the stereo optical system of Example 1, matters common to the stereo optical systems of Examples 1 to 4 will be described.

[0010] In FIG. 1, the left side is the object side and the right side is the image side. The stereo optical system L0 has two optically parallel systems (right optical system and left optical system) LR and LL. The two optical systems LR and LL are held by a holding member (such as the housing of the lens device) not shown. The stereo optical system L0 is housed in a lens device that is detachable or integrally provided in various imaging devices such as a digital video camera, a digital still camera, a broadcast camera, a silver halide film camera, and a surveillance camera.

[0011] Since the two optical systems LR and LL have the same configuration except for the directions of the two reflecting surfaces described later, the right optical system LR will be mainly described below.

[0012] The right optical system LR has a first reflecting surface RS1 and a second reflecting surface RS2. The first reflecting surface RS1 and the second reflecting surface RS2 are each formed on a reflecting optical element such as a prism having an incident surface, a reflecting surface (RS1 or RS2), and an exit surface. However, a mirror having only a reflecting surface without an incident surface and an exit surface may be used as or instead of the reflecting optical element.

[0013] The right optical system LR also has an aperture stop SP on the object side of the first reflecting surface RS1. IP is the image plane (paraxial imaging position). The two optical systems LR and LL each form an optical image on the image plane IP. On the image plane IP, an imaging surface (light receiving surface) of an imaging element such as a CCD sensor or a CMOS sensor or a film surface (photosensitive surface) of a silver halide film is arranged.

[0014] The first reflecting surface RS1 and the second reflecting surface RS2 are provided to bend the optical path (optical axis) in the right optical system LR. Specifically, the first reflecting surface RS1 reflects the light incident from the object side to the left direction, and the second reflecting surface RS2 reflects the light reflected by the first reflecting surface RS1 to the image side. On the other hand, the first reflecting surface RS1 in the left optical system LL reflects the light incident from the object side to the right direction, and the second reflecting surface RS2 reflects the light reflected by the first reflecting surface RS1 to the image side. By bending the optical path in this way, the optical axis distance between the portions on the image side from the second reflecting surface RS2 (between the second groups described later) becomes narrower than the baseline length BL, which is the optical axis distance between the portions on the object side from the first reflecting surface RS1 of the two optical systems LR and LL.

[0015] For this reason, as shown in FIG. 2, on the image plane IP (for example, the imaging plane of a single imaging device), a right image circle ICR and a left image circle ICL are formed side by side by the right optical system LR and the left optical system LL, respectively. Thereby, an imaging device such as a digital camera equipped with a single imaging device can acquire two imaging images (paired parallax images) having mutual parallax and enabling stereoscopic vision.

[0016] FIGS. 3(A) and 3(B) show the specific configuration of the right optical system LR. The right optical system LR includes a first group L1 including at least one lens and the first reflecting surface RS1, and a second reflecting surface RS2 that reflects the light incident on the first group L1 from the object side and reflected by the first reflecting surface RS1 to the image side. The portion on the image side from the first reflecting surface RS1 is configured as a second group L2 including the second reflecting surface RS2 and at least one lens.

[0017] In the stereo optical system L0 of each embodiment, in at least one of the two optical systems LR and LL (here, the right optical system LR), the distance between the first reflecting surface RS1 and the second reflecting surface RS2 (hereinafter referred to as the reflecting surface interval) is changed to make the baseline length BL variable. Specifically, the first group L1 is configured to be movable in the baseline length direction (left - right direction) indicated by double - headed arrows with respect to the second group L2. More specifically, although not shown in the figure, the lens device equipped with the stereo optical system L0 is provided with a mechanism for moving the first group L1 in the baseline length direction by manual operation by the user or a driving force by an actuator.

[0018] FIG. 3(A) shows the right optical system LR when the reflecting surface interval is maximum, and FIG. 3(B) shows the right optical system LR when the reflecting surface interval is minimum. Note that the maximum and minimum reflecting surface intervals refer to the positions where, due to the mechanism, the reflecting surface interval is at both ends of the range where it can be changed or the light amount of the maximum picture angle on the image plane is 5% or less with respect to the maximum light amount within the said picture angle.

[0019] In FIG. 3(A), the air interval AL on the optical axis between the exit surface of the first reflecting optical element as a prism provided with the first reflecting surface RS1 and the entrance surface of the second reflecting optical element as a prism provided with the second reflecting surface RS2 is shown. When the reflecting surface interval is maximum and minimum, the air interval AL also becomes maximum and minimum. Also, in the right optical system LR of Embodiments 3 and 4 shown in FIGS. 5(A) and 7(A), the air interval AL on the optical axis between the first and second reflecting optical elements as mirrors provided with the first and second reflecting surfaces RS1 respectively is shown. In this case, the reflecting surface interval is equal to the air interval AL.

[0020] In this way, since the reflecting surface interval in at least one of the two optical systems LR and LL can be changed, it is possible to adjust the baseline length BL, the adjustment range (variable range) is sufficiently large, and it is possible to realize a stereo optical system with little change in image quality when adjusting the baseline length.

[0021] Next, a preferable configuration that the stereo optical system L0 of each embodiment satisfies will be described.

[0022] First, as described with reference to FIG. 2, it is preferable to form two optical images formed by two optical systems LR and LL on the imaging surface of a single imaging device. Thereby, while ensuring a sufficient baseline length of the two optical systems LR and LL, they can be arranged closely, and it becomes easy to miniaturize the stereo optical system.

[0023] Also, in the second group L2 on the image side from the first reflecting surface RS1, a lens is not necessarily provided. However, by providing a lens in the second group L2, not only can the refractive power be shared between the first group L1 and the second group L2, but also it becomes possible to satisfactorily correct aberration fluctuations when adjusting the baseline length with the lens. For example, by providing a plurality of lenses including at least one positive lens and at least one negative lens in the second group L2, or by providing an aspherical lens, it is possible to satisfactorily correct aberration fluctuations and suppress a decrease in image quality accompanying the adjustment of the baseline length.

[0024] Also, it is preferable that an intermediate imaging point P at which an on-axis light beam forms an image is provided on the object side from the first reflecting surface RS1 in the first group L1. Thereby, when the stereo optical system L0 is a wide-angle lens with a particularly large angle of view, it is possible to reduce the change in peripheral light quantity when adjusting the baseline length. Also, it becomes easy to increase the adjustment range of the baseline length.

[0025] Furthermore, a lens may be arranged between the first reflecting surface RS1 and the second reflecting surface RS2, or the incident surface or the exit surface of the first reflecting optical element as a prism or the incident surface or the exit surface of the second reflecting optical element may be formed as a surface having refractive power.

[0026] Next, the conditions that the stereo optical system L0 of each embodiment preferably satisfies will be described. The right optical system LR (and the left optical system LL if the interval between reflecting surfaces is variable) preferably satisfies at least one of the following conditions (1) to (8).

[0027] 0.00000 ≦ |(fmax - fmin) / fmin| ≦ 0.10000 (1) 0.00000 ≦ |fmin / f1| ≦ 0.05000 (2) 0.50 ≦ (ALmax - ALmin) / f2 ≦ 1.50 (3) 0.0000 ≦ |f2 / f1| ≦ 0.3000 (4) 0.030 ≦ |fmin / f2| ≦ 3.000 (5) 0.0 < |ω12| ≦ 25.0 (6) 1.50 ≦ TLH / BF ≦ 14.00 (7) 0.500 ≦ f1R / f2 ≦ 2.000 (8) In formulas (1) to (8), fmax represents the focal length of the right optical system LR when the reflection surface interval (air interval AL) is the largest, fmin represents the focal length of the right optical system LR when the reflection surface interval is the smallest, f1 represents the focal length of the first group L1, f2 represents the focal length of the second group L2. ALmax represents the maximum value of the air interval AL, and ALmin represents the minimum value of the air interval AL. ω12 represents the angle formed by the central ray of the light beam with the maximum angle of view of the right optical system LR between the first reflection surface RS1 and the second reflection surface RS2 of the right optical system LR and the optical axis. TLH represents the sum of the distance on the optical axis from the surface with the most refractive power on the object side (the frontmost surface) to the first reflection surface RS1 and the distance on the optical axis from the second reflection surface RS2 to the image plane in the right optical system LR. BF represents the back focus of the right optical system LR. The back focus is the air-equivalent distance from the surface with the most refractive power on the image side (the final surface) to the image plane in the right optical system LR. f1R represents the focal length of the subgroup on the image side of the intermediate imaging point P in the first group L1.

[0028] The condition of formula (1) indicates an appropriate range of change in the focal length when adjusting the baseline length. If |(fmax - fmin) / fmin| exceeds the upper limit value of formula (1), at least one of the changes in the maximum angle of view and the maximum image height becomes too large when adjusting the baseline length, which is not preferable. Also, it becomes difficult to ensure the peripheral light quantity when increasing the baseline length, which is not preferable.

[0029] The condition of Equation (2) shows an appropriate relationship between the focal length of the right optical system RL when the reflector interval is minimum and the focal length of the first group L1. If |fmin / f1| exceeds the upper limit value of Equation (2), at least one of the maximum field angle and the maximum image height changes too much when adjusting the baseline length, which is not preferable. Also, when the adjustment range of the baseline length is increased, the diameters of the lenses constituting the right optical system LR and the first and second reflectors RS1 and RS2 increase, and the right optical system LR becomes large, which is not preferable.

[0030] The condition of Equation (3) shows an appropriate relationship between the variable range of the air interval AL and the focal length of the second group L2. If (ALmax - ALmin) / f2 exceeds the upper limit value of Equation (3), the right optical system LR becomes large, which is not preferable. Also, the minimum baseline length between the two optical systems LR and LL becomes too large, which is not preferable. If (ALmax - ALmin) / f2 is below the lower limit value of Equation (3), the adjustment range of the baseline length becomes too small, which is not preferable.

[0031] The condition of Equation (4) shows an appropriate relationship between the focal length of the first group L1 and the focal length of the second group L2. If |f2 / f1| exceeds the upper limit value of Equation (4), the changes in spherical aberration and chromatic aberration during the adjustment of the baseline length become large, and it becomes difficult to reduce the change in image quality, which is not preferable.

[0032] The condition of Equation (5) shows an appropriate relationship between the focal length of the right optical system LR when the reflector interval is minimum and the focal length of the second group L2. If |fmin / f2| exceeds the upper limit value of Equation (5), it becomes difficult to reduce the aberration generated in the second group L2, which is not preferable. Also, the light incident angle on the image plane becomes large and the shading becomes large, which is not preferable. If |fmin / f2| is below the lower limit value of Equation (5), it becomes difficult to reduce the F-number (brighten) of the right optical system LR, which is not preferable. Also, the minimum baseline length between the two optical systems LR and LL becomes too large, which is not preferable.

[0033] The condition of Equation (6) indicates an appropriate range of the angle formed by the central ray of the light beam with the maximum picture angle of the right optical system LR between the first and second reflecting surfaces RS1 and RS2 with respect to the optical axis. If |ω12| exceeds the upper limit value of Equation (6), the diameters of the first and second reflecting surfaces RS1 and RS2 increase, which is not preferable. Also, if the adjustment range of the baseline length is increased, it becomes difficult to ensure the peripheral light quantity, which is not preferable.

[0034] The condition of Equation (7) indicates an appropriate relationship between the length of the right optical system LR and the back focus. If TLH / BF exceeds the upper limit value of Equation (7), the right optical system LR becomes large-sized, which is not preferable. If TLH / BF is below the lower limit value of Equation (7), it becomes difficult to reduce the spherical aberration and chromatic aberration generated in the right optical system LR, which is not preferable.

[0035] The condition of Equation (8) indicates an appropriate relationship between the focal length of the subgroup on the image side of the intermediate imaging point P in the first group L1 and the focal length of the second group L2. If f1R / f2 exceeds the upper limit value of Equation (8), the right optical system LR becomes large-sized, which is not preferable. If f1R / f2 is below the lower limit value of Equation (8), it becomes difficult to reduce the F-number of the right optical system LR, which is not preferable.

[0036] Note that it is more preferable if at least one of the upper limit value and the lower limit value of the numerical range of Equations (1) to (8) is as follows.

[0037] 0.00000 ≦ |(fmax - fmin) / fmin| ≦ 0.03000 (1a) 0.00000 ≦ |fmin / f1| ≦ 0.02000 (2a) 0.75 ≦ (ALmax - ALmin) / f2 ≦ 1.40 (3a) 0.0000 ≦ |f2 / f1| ≦ 0.1000 (4a) 0.070 ≦ |fmin / f2| ≦ 2.500 (5a) 0.0 < |ω12| ≦ 20.0 (6a) 1.80 ≦ TLH / BF ≦ 11.00 (7a) 0.750 ≦ f1R / f2 ≦ 1.400 (8a) Furthermore, it is more preferable that at least one of the upper limit value and the lower limit value of the numerical ranges of formulas (1) to (8) is as follows.

[0038] 0.00000 ≦ |(fmax - fmin) / fmin| ≦ 0.00100 (1b) 0.00000 ≦ |fmin / f1| ≦ 0.00050 (2b) 0.80 ≦ (ALmax - ALmin) / f2 ≦ 1.20 (3b) 0.0000 ≦ |f2 / f1| ≦ 0.0010 (4b) 0.100 ≦ |fmin / f2| ≦ 1.800 (5b) 0.0 < |ω12| ≦ 15.0 (6b) 2.00 ≦ TLH / BF ≦ 9.50 (7b) 0.900 ≦ f1R / f2 ≦ 1.200 (8b) Next, numerical examples 1 to 4 corresponding to each of the right optical systems LR of Examples 1 to 4 will be described. The detailed data of each numerical example will be summarized after Example 4.

Example

[0039] The right optical system LR of Example 1 (numerical example 1) shown in FIG. 1 is an optical system having a half angle of view of 96.7° when the distance between the reflecting surfaces is minimum.

[0040] In Example 1, both the first reflective optical element and the second reflective optical element are constituted by prisms, and the air gap AL is the distance between the prisms. The minimum value of the air gap AL is 1 mm and the maximum value is 40.2 mm. An intermediate imaging point P is formed within the first group L1. Thereby, while increasing the half angle of view, a large adjustment range of the baseline length is ensured.

[0041] When the right optical system LR and the left optical system LL are arranged such that their image circles are in contact with each other, the minimum baseline length is 37 mm and the maximum baseline length is 115.4 mm.

[0042] Figures 4(A) and (B) show the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the right optical system LR in Numerical Example 1. Figure 4(A) shows the longitudinal aberrations when the reflection surface interval is maximum, and Figure 4(B) shows the longitudinal aberrations when the reflection surface interval is minimum. In the spherical aberration diagram, Fno indicates the F-number. The solid line indicates the spherical aberration for the d-line (wavelength 587.6 nm), and the two-dot chain line indicates the spherical aberration for the g-line (wavelength 435.8 nm). In the astigmatism diagram, the solid line ΔS indicates the astigmatism at the sagittal image plane, and the broken line ΔM indicates the astigmatism at the meridional image plane. The distortion aberration diagram shows the distortion aberration for the d-line. The chromatic aberration diagram shows the magnification chromatic aberration for the g-line. ω is the half field angle (°).

[0043] Note that the above description regarding the longitudinal aberration diagrams is the same for the longitudinal aberration diagrams ((A), (B)) in other numerical examples.

Example

[0044] The right optical system LR in Example 2 (Numerical Example 2) shown in FIG. 5 is an optical system with a half field angle of 31.4° when the reflection surface interval L is minimum.

[0045] Also in Example 2, both the first reflective optical element and the second reflective optical element are composed of prisms, and the air interval AL is the air interval between the prisms. The minimum value of the air interval AL is 1 mm, and the maximum value is 68 mm. An intermediate imaging point P is formed within the first group L1.

[0046] When the right optical system LR and the left optical system LL are arranged such that their image circles are in contact with each other, the minimum baseline length is 35 mm, and the maximum baseline length is 115.4 mm.

[0047] Figures 6(A) and (B) show the longitudinal aberrations when the reflection surface interval of the right optical system LR in Numerical Example 2 is maximum and the longitudinal aberrations when the reflection surface interval is minimum, respectively.

Example

[0048] The right optical system LR in Example 3 (numerical example 3) shown in FIG. 7 is an optical system with a half angle of view of 3.05° when the reflector interval L is at its minimum.

[0049] In Example 3, both the first reflective optical element and the second reflective optical element are composed of mirrors, and the air interval AL is the interval between the mirrors. The minimum value of the air interval AL is 16 mm, and the maximum value is 122 mm. In this example, no intermediate imaging point P is formed on the object side of the first reflective surface RS1.

[0050] When the right optical system LR and the left optical system LL are arranged such that their image circles are in contact with each other, the minimum baseline length is 32 mm, and the maximum baseline length is 244 mm.

[0051] FIGS. 8(A) and (B) respectively show the longitudinal aberration when the reflector interval of the right optical system LR in numerical example 3 is at its maximum and the longitudinal aberration when the reflector interval is at its minimum.

Example

[0052] The right optical system LR in Example 4 (numerical example 4) shown in FIG. 9 is an optical system with a half angle of view of 2.06° when the reflector interval L is at its minimum.

[0053] Also in Example 4, both the first reflective optical element and the second reflective optical element are composed of mirrors, and the air interval AL is the interval between the mirrors. The minimum value of the air interval AL is 20.8 mm, and the maximum value is 182.5 mm. Also in this example, no intermediate imaging point P is formed on the object side of the first reflective surface RS1.

[0054] When the right optical system LR and the left optical system LL are arranged such that their image circles are in contact with each other, the minimum baseline length is 41.6 mm, and the maximum baseline length is 365 mm.

[0055] FIGS. 10(A) and (B) respectively show the longitudinal aberration when the reflector interval of the right optical system LR in numerical example 4 is at its maximum and the longitudinal aberration when the reflector interval is at its minimum.

[0056] The numerical data of Numerical Examples 1 to 4 are shown below. In the surface data, m indicates the order of the surface counted from the object side, r indicates the radius of curvature (mm) of the m-th surface, d indicates the axial interval (distance on the optical axis) (mm) between the m-th surface and the (m + 1)-th surface. nd indicates the refractive index of the optical material between the m-th surface and the (m + 1)-th surface at the d-line, and νd indicates the Abbe number based on the d-line of the optical material between the m-th surface and the (m + 1)-th surface. The Abbe number νd based on the d-line is defined as follows: when the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), C-line (656.3 nm), and g-line (wavelength 435.8 nm) of the Fraunhofer lines are nd, nF, nC, and ng respectively, νd=(nd-1) / (nF-nC) is expressed as

[0057] In each numerical example, d, focal length (mm), F-number, and half angle (°) are all values in the state where the optical system is focused on an infinitely distant object. The back focus BF is as described above. 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 to the final surface of the optical system.

[0058] The values of formulas (1) to (8) in each numerical example are summarized in Table 1. Each numerical example satisfies all the conditions of formulas (1) to (8). [Numerical Example 1] Unit: mm Surface data Surface number r d nd νd 1 20.672 1.90 2.00100 29.1 2 6.211 5.78 3 17.415 1.05 2.00100 29.1 4 6.592 5.84 5 -4.878 0.85 1.62588 35.7 6 -5.687 0.95 7 -57.693 2.98 1.80518 25.4 8 -9.433 2.02 9 (Aperture) ∞ 1.67 10 -17.781 0.50 1.90043 37.4 11 15.390 3.27 1.54072 47.2 12 -10.015 1.13 13 10.281 3.76 1.80809 22.8 14 8.985 6.04 15 73.571 4.23 1.49700 81.6 16 -20.393 0.53 17 12.358 5.97 1.49700 81.6 18 -176.868 0.56 19 -119.883 0.75 2.00069 25.5 20 10.785 8.88 1.49700 81.6 21 -23.027 22.36 22 -47.655 3.48 1.80518 25.4 23 -24.812 36.53 24 45.444 8.76 1.48749 70.2 25 -18.811 2.90 1.68893 31.1 26 -26.411 0.48 27 -30.622 0.77 1.59270 35.3 28 103.208 0.54 29 107.590 3.05 1.84666 23.9 30 -77.477 0.52 31 73.013 1.00 2.00330 28.3 32 22.136 5.15 1.49700 81.7 33 -94.617 0.50 34 ∞ 10.00 1.51633 64.1 35 ∞ -10.00 36 ∞ (variable) 37 ∞ -7.50 1.51633 64.1 38 ∞ 7.50 39 ∞ 2.80 40 35.484 1.43 2.00100 29.1 41 17.379 0.20 42 14.469 3.25 1.48749 70.2 43 29758.415 0.49 44 15.047 2.44 1.84666 23.8 45 39.359 4.22 46 -75.053 2.77 1.63636 35.4 47 14.623 1.68 48 38.300 6.52 1.69680 55.5 49 -7.776 2.05 1.85025 30.1 50 -27.364 BF Image plane ∞ Various data Maximum AL Minimum AL Focal length -5.11 -5.11 F-number 2.91 2.91 Half field angle (°) 96.8 96.7 Image height 8.55 8.55 Overall lens length 272.22 233.02 d36 -40.20 -1.00 BF 24.47 24.47 Lens group data Group Starting surface Focal length 1 1 -56508.05 2 37 42.01 Intermediate imaging position (paraxial): 67.85 mm on the image side from surface number 1 Projection method: Orthogonal projection [Numerical example 2] Unit mm Surface data Surface number r d nd νd 1 26.706 1.00 2.00069 25.5 2 10.564 7.11 3 -13.019 1.00 1.49700 81.6 4 -15.567 0.50 5 24.296 6.85 1.48749 70.2 6 -18.180 0.50 7 13.496 4.08 2.00330 28.3 8 29.908 2.54 9 -626.898 1.17 1.62588 35.7 10 4.257 3.25 11 (Aperture) ∞ 2.00 12 -17.585 3.88 1.48749 70.2 13 -6.276 0.50 14 48.293 4.38 1.49700 81.6 15 -10.813 1.16 1.90366 31.3 16 -16.110 38.43 17 -29.949 5.01 1.78800 47.4 18 -17.980 0.50 19 16.571 3.77 2.00100 29.1 20 18.134 1.97 21 28.976 2.71 1.89286 20.4 22 226.587 1.23 23 -98.893 0.75 1.78472 25.7 24 14.033 32.52 25 66.515 3.05 1.96300 24.1 26 -37.365 0.50 27 -36.751 1.00 2.00330 28.3 28 27.578 0.50 29 26.958 4.78 1.49700 81.7 30 -22.572 0.50 31 ∞ 9.00 1.51633 64.1 32 ∞ -9.00 33 ∞ (Variable) 34 ∞ -7.50 1.51633 64.1 35 ∞ 7.50 36 ∞ 0.50 37 19.377 2.65 1.49700 81.7 38 791.452 0.97 39 -68.030 3.01 1.84666 23.8 40 -26.484 0.78 41 -20.670 2.60 1.76200 40.1 42 25.576 0.50 43 16.401 10.00 1.49700 81.7 44 -22.533 8.64 45 -10.121 1.00 1.70154 41.2 46 -14.648 BF Image plane ∞ Various data Maximum AL Minimum AL Focal length -14.00 -14.00 F-number 4.12 4.12 Half field angle (°) 31.5 31.4 Image height 8.55 8.55 Overall lens length 301.50 234.50 d33 -68.00 -1.00 BF 32.71 32.71 Lens group data Group Starting surface Focal length 1 1 153575.65 2 34 58.97 Intermediate imaging position (paraxial): 62.63 mm on the image side from surface number 1 Projection method: Orthographic projection [Numerical example 3] Unit mm Surface data Surface number r d nd νd 1 32.164 2.90 1.48749 70.2 2 121.654 0.72 3 27.985 0.75 1.83400 37.2 4 20.759 5.29 1.49700 81.6 5 344.533 9.00 6 -227.502 0.71 1.85150 40.8 7 23.558 1.57 8 63.617 0.71 1.72916 54.7 9 17.865 2.20 1.85025 30.1 10 56.504 8.48 11 ∞ (variable) 12 ∞ 8.00 13 19.034 3.10 1.49700 81.5 14 -50.341 5.27 15 -27.738 0.92 1.89190 37.1 16 -183.939 13.49 17 28.975 0.92 1.83481 42.7 18 14.876 6.82 19 22.828 1.63 1.76182 26.5 20 47.083 BF Image plane ∞ Various data AL maximum AL minimum Focal length 159.98 159.99 F-number 7.75 7.75 Half field angle (°) 3.06 3.05 Image height 8.55 8.55 Overall lens length 247.03 141.03 d11 -122.00 -16.00 BF 52.55 52.55 Lens group data Group Starting surface Focal length 1 1 -2206189.13 2 12 100.96 Projection method: Orthographic projection [Numerical example 4] Unit mm Surface data Surface number r d nd νd 1 34.816 4.25 1.48749 70.2 2 112.835 0.50 3 32.205 1.11 1.83400 37.2 4 23.432 6.25 1.49700 81.6 5 175.125 10.78 6 -502.073 1.05 1.85150 40.8 7 25.630 1.79 8 54.636 1.05 1.72916 54.7 9 19.674 3.07 1.85025 30.1 10 58.301 12.52 11 ∞ (variable) 12 ∞ 10.50 13 29.607 2.60 1.49700 81.5 14 -55.681 7.06 15 -35.775 1.36 1.89190 37.1 16 -123.352 33.27 17 128.613 1.36 1.83481 42.7 18 22.804 6.34 19 32.052 1.40 1.76182 26.5 20 133.371 BF Image plane ∞ Various data AL maximum AL minimum Focal length 236.75 236.76 F number 11.30 11.30 Half field angle (°) 2.08 2.06 Image height 8.55 8.55 Overall lens length 346.52 184.10 d11 -182.50 -20.08 BF 57.76 57.76 Lens group data Group Starting surface Focal length 1 1 -6037018.63 2 12 147.16 Projection method: Orthographic projection

[0059]

Table 1

[0060] [Imaging device] FIG. 11 shows an imaging device (digital still camera) 10 using the stereo optical system L0 of Examples 1 to 4. In FIG. 11, 13 is a camera body, and 11 is an imaging optical system constituted by any one of the stereo optical systems L0 (right optical system LR and left optical system LL) of Examples 1 to 4. The lens device including the imaging optical system may be detachable from the camera body 13 or may be integrally provided. 12 is an imaging element such as a CCD sensor or a CMOS sensor that is built in the camera body 13 and photoelectrically converts the optical image formed by the imaging optical system 11 (i.e., captures an object).

[0061] The camera body 13 may be a single-lens reflex camera having a quick-turn mirror or a mirrorless camera not having a quick-turn mirror.

[0062] Thus, an imaging device using the stereo optical system L0 of Examples 1 to 4 as an imaging optical system can obtain a pair of parallax images with a large adjustment range of stereoscopic effect and a small change in image quality due to the adjustment of stereoscopic effect.

[0063] The above embodiments include the following configurations.

[0064] (Configuration 1) A stereo optical system having two optical systems arranged in parallel, each of the two optical systems includes a first group including at least one lens and a first reflecting surface, and a second reflecting surface that reflects the light incident on the first group from the object side and reflected by the first reflecting surface to the image side, and the interval between the second reflecting surfaces is narrower than the baseline length between the first groups in the two optical systems, A stereo optical system, characterized in that the baseline length is variable by changing the distance on the optical axis between the first reflecting surface and the second reflecting surface in at least one of the two optical systems. (Configuration 2) The stereo optical system according to Configuration 1, wherein each of the two optical systems is arranged on the image side of the first reflecting surface and has a second group including the second reflecting surface and at least one lens. (Configuration 3) When the focal length of at least one of the optical systems when the distance is minimum is fmin, and the focal length of at least one of the optical systems when the distance is maximum is fmax, 0.00000 ≦ |(fmax - fmin) / fmin| ≦ 0.10000 The stereo optical system according to Configuration 1 or 2, characterized in that the condition is satisfied. (Configuration 4) When the focal length of at least one of the optical systems when the distance is minimum is fmin, and the focal length of the first group is f1, 0.00000 ≦ |fmin / f1| ≦ 0.05000 The stereo optical system according to any one of Configurations 1 to 3, characterized in that the condition is satisfied. (Configuration 5) The first reflecting surface is provided on a first reflecting optical element, and the second reflecting surface is provided on a second reflecting optical element. When the maximum value of the distance on the optical axis between the first reflecting optical element and the second reflecting optical element is ALmax, the minimum value of the air gap is ALmin, and the focal length of the second group is f2, 0.50 ≦ (ALmax - ALmin) / f2 ≦ 1.50 The stereo optical system according to Configuration 2, characterized in that the condition is satisfied. (Configuration 6) When the focal length of the first group is f1 and the focal length of the second group is f2, 0.0000 ≦ |f2 / f1| ≦ 0.3000 The stereo optical system according to Configuration 2 or 5, characterized in that the condition is satisfied. (Configuration 7) When the focal length of at least one of the optical systems at the time when the distance is minimum is fmin and the focal length of the second group is f2, 0.030 ≦ |fmin / f2| ≦ 3.000 The stereo optical system according to Configuration 2, 5, or 6, characterized by satisfying the condition. (Configuration 8) When the angle formed by the central ray of the light beam with the maximum image angle of at least one of the optical systems and the optical axis is ω12 between the first reflecting surface and the second reflecting surface, 0.0 < |ω12| ≦ 25.0 The stereo optical system according to any one of Configurations 1 to 7, characterized by satisfying the condition. (Configuration 9) When the sum of the distance on the optical axis from the most object-side surface of at least one of the optical systems to the first reflecting surface and the distance on the optical axis from the second reflecting surface to the image surface is TLH and the back focus of at least one of the optical systems is BF, 1.50 ≦ TLH / BF ≦ 14.00 The stereo optical system according to any one of Configurations 1 to 8, characterized by satisfying the condition. (Configuration 10) The stereo optical system according to any one of Configurations 1 to 9, characterized by having an intermediate imaging point on the image side of the first reflecting surface in the first group where the on-axis light beam forms an image. (Configuration 11) The first group has an intermediate imaging point on the image side of the first reflecting surface where the on-axis light beam forms an image, When the focal length of the subgroup on the image side of the intermediate imaging point in the first group is f1R and the focal length of the second group is f2, 0.500 ≦ f1R / f2 ≦ 2.000 The stereo optical system according to Configuration 2, 5, 6, or 7, characterized by satisfying the condition. (Configuration 12) The stereo optical system according to any one of Configurations 1 to 9, characterized in that two optical images formed by the two optical systems are formed on the imaging surface of a single imaging device. (Configuration 13) The stereoscopic optical system according to any one of Configurations 1 to 12, and an imaging device having an imaging element that images a subject through the stereoscopic optical system.

[0065] 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.

Explanation of Reference Numerals

[0066] L0 Stereoscopic optical system LR Right optical system LL Left optical system L1 First group L2 Second group RS1 First reflecting surface RS2 Second reflecting surface

Claims

1. A stereo optical system having two optical systems arranged in parallel, each of the two optical systems includes a first group including at least one lens and a first reflecting surface, and a second reflecting surface that reflects light incident on the first group from the object side and reflected by the first reflecting surface to the image side, and the distance between the second reflecting surfaces is narrower than the baseline length between the first groups in the two optical systems, A stereo optical system characterized in that the baseline length is variable by changing the distance on the optical axis between the first reflecting surface and the second reflecting surface in at least one of the two optical systems.

2. The stereo optical system according to claim 1, wherein each of the two optical systems is disposed on the image side of the first reflecting surface and has a second group including the second reflecting surface and at least one lens.

3. When the focal length of at least one of the optical systems when the distance is minimum is fmin, and the focal length of at least one of the optical systems when the distance is maximum is fmax, 0.00000 ≤ |(fmax - fmin) / fmin| ≤ 0.10000 The stereo optical system according to claim 1, characterized in that the condition is satisfied.

4. When the focal length of at least one of the optical systems when the distance is minimum is fmin, and the focal length of the first group is f1, 0.00000 ≤ |fmin / f1| ≤ 0.05000 The stereo optical system according to claim 1, characterized in that the condition is satisfied.

5. The first reflecting surface is provided on a first reflecting optical element, the second reflecting surface is provided on a second reflecting optical element, When the maximum value of the distance on the optical axis between the first reflecting optical element and the second reflecting optical element is ALmax, the minimum value of the air gap is ALmin, and the focal length of the second group is f2, 0.50 ≤ (ALmax - ALmin) / f2 ≤ 1.50 The stereo optical system according to claim 2, characterized in that the condition is satisfied.

6. When the focal length of the first group is f1 and the focal length of the second group is f2, 0.0000 ≤ |f2 / f1| ≤ 0.3000 The stereo optical system according to claim 2, characterized in that the condition is satisfied.

7. When the focal length of at least one of the optical systems when the distance is minimum is fmin, and the focal length of the second group is f2, 0.030 ≤ |fmin / f2| ≤ 3.000 The stereo optical system according to claim 2, characterized by satisfying the following conditions.

8. When the central ray of the light beam with the maximum picture angle of at least one of the optical systems forms an angle ω12 with the optical axis between the first reflecting surface and the second reflecting surface, 0.0 < |ω12| ≤ 25.0 The stereo optical system according to claim 1, characterized by satisfying the following conditions.

9. When the sum of the distance on the optical axis from the most object-side surface of at least one of the optical systems to the first reflecting surface and the distance on the optical axis from the second reflecting surface to the image surface is TLH, and the back focus of at least one of the optical systems is BF, 1.50 ≤ TLH / BF ≤ 14.00 The stereo optical system according to claim 1, characterized by satisfying the following conditions.

10. The stereo optical system according to claim 1, characterized by having an intermediate imaging point on the image side of the first reflecting surface in the first group, where the on-axis light beam forms an image.

11. On the image side of the first reflecting surface in the first group, it has an intermediate imaging point where the on-axis light beam forms an image, When the focal length of the subgroup on the image side of the intermediate imaging point in the first group is f1R and the focal length of the second group is f2, 0.500 ≤ f1R / f2 ≤ 2.000 The stereo optical system according to claim 2, characterized by satisfying the following conditions.

12. The stereo optical system according to claim 1, characterized by forming two optical images formed by the two optical systems on the imaging surface of a single imaging device.

13. An imaging device, comprising the stereo optical system according to any one of claims 1 to 12, and an imaging device that images a subject through the stereo optical system.

Images