Stereo optical system and imaging apparatus

Abstract

To provide a stereo optical system with a sufficient base line length, a wide angle, and a high magnification ratio.SOLUTION: Two magnification-variable optical systems arranged in parallel in a stereo optical system 100 each comprise a positive first lens group L1, a negative second lens group L2, a third lens group L3, and a rear group LR including at least one lens group. The third lens group includes a first reflecting surface M1 and a second reflecting surface M2, 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. In each of the two optical systems, the second lens group moves in zooming, and when the focal length at a wide-angle end of the optical system is defined as fw, and the focal length of the first lens group as f1, the condition of 3.5≤f1 / fw≤32.0 is satisfied.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] As a stereo optical system in which two optical systems are arranged in parallel, Patent Document 1 discloses a positive-bleed type variable magnification 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 of these 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 securing 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 two optical systems on a single imaging element.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, it cannot be said that the stereo optical system of Patent Document 1 has a sufficient baseline length and is wide-angle and has a high magnification ratio.

[0005] The present invention provides a stereo optical system having a sufficient baseline length, wide angle, and high magnification ratio, and an imaging device equipped with the same, after arranging two variable magnification optical systems having a configuration for bending the optical path in parallel.

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 is composed of a first lens group with a positive refractive power, a second lens group with a negative refractive power, a third lens group, and a rear group including at least one lens group, 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 and a second reflecting surface, and due to the bending of the optical path by the first and second reflecting surfaces, 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. In each of the two optical systems, at least the second lens group moves during zooming. When the focal length at the wide-angle end of the optical system is fw and the focal length of the first lens group is f1, 3.5 ≦ f1 / fw ≦ 32.0 It is characterized by satisfying the condition. In addition, an imaging device equipped with the above stereo optical system also constitutes another aspect of the present invention.

Effects 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 baseline length, a wide angle, and a high zoom ratio can be realized.

Brief Description of the Drawings

[0008]

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Modes for Carrying Out the Invention

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

[0010] FIG. 21 shows the basic configuration of the stereo optical system 100 of Embodiments 1 to 4 as viewed from above. In FIG. 21, 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 detachably 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] IM 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 IM. On the image plane IM, 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.

[0012] The stereo optical system 100 of each embodiment is composed of a first lens group L1 with a positive refractive power, a second lens group L2 with a negative refractive power, a third lens group L3, and a rear group LR including at least one lens group, which are arranged in order from the object side to the image side in the two optical systems 101 and 102. The third lens group L3 includes a first reflecting surface M1 arranged on the object side, a second reflecting surface M2 arranged on the image side, and an aperture stop SP. The aperture stop SP determines (limits) the open F-number (Fno) light beam.

[0013] In each embodiment, both the first reflecting surface M1 and the second reflecting surface M2 are formed on a reflecting member as a prism having an incident surface, a reflecting surface (M1 or M2), and an exit surface, but may be provided on a mirror as a reflecting member having no incident surface and exit surface for the reflecting surface.

[0014] The first reflecting surface M1 and the second reflecting surface M2 are provided for bending the optical path (optical axis) in each optical system. Specifically, the first reflecting surface M1 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 M2 reflects the light reflected by the first reflecting surface M1 to the image side. By bending the optical path in this way, the optical axis interval Dout between the rear lens groups LR becomes 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.

[0015] Therefore, as shown in FIG. 22, on the image plane IM (for example, the imaging plane of a single imaging device), 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 device can acquire two imaging images (paired parallax images) that can perform stereoscopic vision with mutual parallax.

[0016] Also, 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, at least the second lens group L2 moves during zooming.

[0017] In a zoom optical system, a lens group is a collection of one or more lenses that move integrally during zooming or focusing. That is, the interval between adjacent lens groups changes during zooming or focusing. The wide - angle end and the telephoto end in zooming respectively indicate the 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.

[0018] FIG. 1, FIG. 6, FIG. 11, and FIG. 16 each show one of the two optical systems 101 and 102 that constitute the stereo optical system of Examples 1 to 4 (hereinafter referred to as each optical system). OA in each figure indicates the optical axis.

[0019] Each optical system is a positive-zoom optical system in which the first lens group L1 on the object side has a positive refractive power. While miniaturizing the entire optical system, a high zoom ratio is achieved. As described above, in each embodiment, at least the second lens group L2 moves during zooming. This makes it possible to obtain a high zoom ratio. In Embodiments 1, 3, and 4, the second lens group L2 and the fourth lens group L4 move during zooming. This can avoid the situation where the movement amount of the fourth lens group L4 becomes too large and the lens diameter (effective diameter) of the fourth lens group L4 becomes too large. In Embodiment 2, the first lens group L1 and the second lens group L2 move during zooming.

[0020] In the above configuration, when the focal length at the wide-angle end of each optical system is fw and the focal length of the first lens group L1 is f1, the following condition of formula (1) is satisfied.

[0021] 3.5 ≤ f1 / fw ≤ 32.0 (1) If f1 becomes too long such that f1 / fw exceeds the upper limit of formula (1), it is not preferable because the entire optical system becomes large and it becomes difficult to obtain a high zoom ratio. If fw becomes too long such that f1 / fw is below the lower limit of formula (1), it is not preferable because it becomes difficult to widen the angle of each optical system.

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

[0023] 3.6 ≤ f1 / fw ≤ 30.0 (1a) Also, it is even more preferable to set the numerical range of formula (1) as follows.

[0024] 3.7 ≤ f1 / fw ≤ 28.0 (1b) By satisfying the above configuration and conditions, 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 baseline length, a wide angle, and a high zoom ratio can be realized.

[0025] The following describes the configurations and conditions that each optical system preferably satisfies. Each optical system preferably satisfies at least one of the following configurations and the conditions of formulas (2) to (9).

[0026] Each optical system preferably has a configuration that does not form an intermediate image. Thereby, the overall length of the optical system can be shortened.

[0027] In each optical system, it is preferable that the third lens group L3 does not move (is fixed) during zooming. Thereby, the mechanism for driving the lens group that moves during zooming can be simplified.

[0028] Each optical system preferably has an aperture stop SP between the first reflecting surface M1 and the second reflecting surface M2. Thereby, an increase in the lens diameter of the entire optical system can be suppressed, and the entire optical system can be miniaturized.

[0029] In each optical system, when the distance on the optical axis between the first reflecting surface M1 and the second reflecting surface M2 is Dm, and the overall optical length at the wide-angle end of the optical system is Lw, it is preferable to satisfy the condition of the following formula (2).

[0030] 0.05 ≦ Dm / Lw ≦ 0.50 (2) If Dm becomes too long such that Dm / Lw exceeds the upper limit of formula (2), the entire optical system becomes large, which is not preferable. If Dm becomes too short such that Dm / Lw is below the lower limit of formula (2), it becomes difficult to ensure a sufficient baseline length, which is not preferable.

[0031] When the focal length of the partial group GM disposed between the first reflecting surface M1 and the second reflecting surface M2 in the third lens group L3 of each optical system is fm, it is preferable to satisfy the condition of the following formula (3).

[0032] 0.05 ≦ Dm / fm ≦ 0.80 (3) If Dm becomes too long such that Dm / fm exceeds the upper limit of Expression (3), the entire optical system becomes large, which is not preferable. Further, if fm becomes too short such that Dm / fm exceeds the upper limit of Expression (3), it becomes difficult to correct coma aberration, which is not preferable. If Dm becomes too short such that Dm / fm is below the lower limit of Expression (3), it becomes difficult to secure a sufficient baseline length, which is not preferable. Further, if fm becomes too long such that Dm / fm is below the lower limit of Expression (3), the effective diameter of the second reflecting surface M2 increases, which is not preferable.

[0033] In each optical system, when the length (thickness) on the optical axis from the most object-side surface to the most image-side surface of the first lens group L1 is D1 and the thickness on the optical axis from the object-side surface to the most image-side surface of the third lens group L3 is D3, the following condition of Expression (4) is satisfied.

[0034] 1.7 ≦ D3 / D1 ≦ 10.0 (4) If D3 becomes too long such that D3 / D1 exceeds the upper limit of Expression (4), the entire optical system becomes large, which is not preferable. If D3 becomes too short such that D3 / D1 is below the lower limit of Expression (4), it becomes difficult to secure a sufficient baseline length, which is not preferable.

[0035] In each optical system, it is preferable to satisfy the following condition of Expression (5).

[0036] 0.9 ≦ Dm / D1 ≦ 5.0 (5) If Dm becomes too long such that Dm / D1 exceeds the upper limit of Expression (5), the entire optical system becomes large, which is not preferable. If Dm becomes too short such that Dm / D1 is below the lower limit of Expression (5), it becomes difficult to secure a sufficient baseline length, which is not preferable.

[0037] In each optical system, when the thickness on the optical axis from the object-side surface to the most image-side surface of the second lens group L2 is D2, the following condition of Expression (6) is satisfied.

[0038] 0.35 ≦ D2 / D1 ≦ 2.50 (6) If D2 becomes too long such that D2 / D1 exceeds the upper limit of Equation (6), the entire optical system becomes large, which is not preferable. If D2 becomes too short such that D2 / D1 is below the lower limit of Equation (6), it becomes difficult to ensure a sufficient zoom ratio, which is not preferable.

[0039] In each optical system, when the distance on the optical axis between the first reflecting surface M1 and the aperture stop SP is dp1, 0.30 ≦ dp1 / Dm ≦ 0.90 (7) If dp1 becomes too long such that dp1 / Dm exceeds the upper limit of Equation (7), the effective diameter of the first lens group L1 or the effective diameter of the first reflecting surface M1 increases, which is not preferable. If dp1 becomes too short such that dp1 / Dm is below the lower limit of Equation (7), there is a risk of interference between the first reflecting surface M1 and the aperture stop SP, which is not preferable.

[0040] In each optical system, when the focal length of the third lens group L3 is f3, 0.9 ≦ f3 / Dm ≦ 3.5 (8) If f3 becomes too long such that f3 / Dm exceeds the upper limit of Equation (8), the effective diameter of the rear group LR increases, which is not preferable. If f3 becomes too short such that f3 / Dm is below the lower limit of Equation (8), it becomes difficult to correct coma aberration, which is not preferable.

[0041] In the two optical systems, when the optical axis interval (baseline length) between the first lens groups L1 is Din and the optical axis interval between the rear groups LR is Dout, it is preferable to satisfy the condition of the following Equation (9).

[0042] 0.05 ≦ Dout / Din ≦ 0.50 (9) If Dout becomes too long such that Dout / Din exceeds the upper limit of Equation (9), it becomes difficult to form the image circles of the two optical systems on a single imaging device, which is not preferable. If Din becomes too short such that Dout / Din exceeds the upper limit of Equation (9), it becomes difficult to ensure a sufficient baseline length, which is not preferable. If Dout becomes too short such that Dout / Din is below the lower limit of Equation (9), there is a risk of interference between the rear groups LR, which is not preferable. If Din becomes too long such that Dout / Din is below the lower limit of Equation (9), the entire optical system becomes large, which is not preferable.

[0043] Note that it is more preferable if the numerical ranges of Equation (1) are as follows.

[0044] 0.07 ≦ Dm / Lw ≦ 0.40 (2a) 0.07 ≦ Dm / fm ≦ 0.70 (3a) 1.8 ≦ D3 / D1 ≦ 8.5 (4a) 1.0 ≦ Dm / D1 ≦ 4.0 (5a) 0.38 ≦ D2 / D1 ≦ 2.20 (6a) 0.40 ≦ dp1 / Dm ≦ 0.80 (7a) 1.0 ≦ f3 / Dm ≦ 3.2 (8a) 0.08 ≦ Dout / Din ≦ 0.45 (9a) Also, it is even more preferable if the numerical ranges of Equation (1) are as follows.

[0045] 0.09 ≦ Dm / Lw ≦ 0.30 (2b) 0.09 ≦ Dm / fm ≦ 0.60 (3b) 1.9 ≦ D3 / D1 ≦ 7.0 (4b) 1.1 ≦ Dm / D1 ≦ 3.5 (5b) 0.41 ≦ D2 / D1 ≦ 1.90 (6b) 0.50 ≦ dp1 / Dm ≦ 0.75 (7b) 1.1 ≦ f3 / Dm ≦ 2.9 (8b) 0.11 ≦ Dout / Din ≦ 0.40 (9b) Hereinafter, the optical systems of Examples 1 to 4 and Numerical Examples 1 to 4 corresponding to each of them will be specifically described.

Example

[0046] The optical system of Example 1 (Numerical Example 1) shown in FIG. 1 is a zoom optical system with an aperture ratio of about 4.0 and a half field angle of about 39.0° at the wide-angle end, and an aperture ratio of about 4.0 and a half field angle of about 17.2° at the telephoto end.

[0047] The optical system of this example is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, and a fifth lens group L5 with negative refractive power, which are arranged in order from the object side to the image side. When zooming, the first lens group L1, the third lens group L3, and the fifth lens group L5 do not move. When zooming from the wide-angle end to the telephoto end, as shown by the diagonal arrows in the figure, the second lens group L2 moves toward the image side and the fourth lens group L4 moves toward the object side. When focusing from an infinite object to a near-distance object, as shown by the horizontal arrow in the figure, the fourth lens group L4 moves toward the object side.

[0048] The third lens group L3 includes a first reflecting surface M1 and a second reflecting surface M2, and an aperture stop SP is arranged between the first reflecting surface M1 and the second reflecting surface M2. Also, between the first reflecting surface M1 and the aperture stop SP (the second reflecting surface M2) in the third lens group L3, a partial group GM composed of a cemented lens in which a negative lens and a positive lens are cemented is arranged.

[0049] FIG. 2 and FIG. 3 respectively show the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) in the state where the optical system of Numerical Example 1 is focused on an object at infinity at the wide-angle end (hereinafter referred to as the infinity focusing state) and the state where it is focused on a near-distance object (referred to as the near-distance focusing state). FIG. 4 and FIG. 5 respectively show the longitudinal aberrations in the state where the optical system of Example 1 is focused on an object at infinity at the telephoto end and the near-distance focusing state.

[0050] In the spherical aberration diagram, Fno indicates the F-number. The solid line represents the spherical aberration for the d-line (wavelength 587.6 nm), and the two-dot chain line represents the spherical aberration for the g-line (wavelength 435.8 nm). In the astigmatism diagram, the solid line S represents the astigmatism at the sagittal image plane, and the dashed line M represents the astigmatism at the meridional image plane. The distortion diagram shows the distortion at the d-line. The chromatic aberration diagram shows the longitudinal chromatic aberration at the g-line. ω is the semi-field angle (°). The explanations of the above aberration diagrams are the same for the aberration diagrams of other numerical examples described later.

Example

[0051] The optical system of Example 2 (numerical example 2) shown in FIG. 6 is a zoom optical system with an aperture ratio of about 4.0 at the wide-angle end, a semi-field angle of about 31.7°, an aperture ratio of about 4.0 at the telephoto end, and a semi-field angle of about 14.3°.

[0052] The optical system of this example is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, and a fifth lens group L5 with negative refractive power, which are arranged in order from the object side to the image side. When zooming, the third lens group L3, the fourth lens group L4, and the fifth lens group L5 do not move. When zooming from the wide-angle end to the telephoto end, the first lens group L1 moves toward the object side, and the second lens group L2 moves toward the image side. When focusing from an infinite object to a close object, the fourth lens group L4 moves toward the object side.

[0053] The third lens group L3 includes a first reflecting surface M1 and a second reflecting surface M2, and an aperture stop SP is arranged between the first reflecting surface M1 and the second reflecting surface M2. Also, between the first reflecting surface M1 and the aperture stop SP (the second reflecting surface M2) in the third lens group L3, a subgroup GM composed of a cemented lens in which a negative lens and a positive lens are cemented is arranged.

[0054] Figures 7 and 8 respectively show the longitudinal aberration of the optical system of Numerical Example 2 in the wide-angle end and the infinite-focus state and the close-focus state. Figures 9 and 10 respectively show the longitudinal aberration of the optical system of Numerical Example 2 in the telephoto end and the infinite-focus state and the close-focus state.

Example

[0055] The optical system of Example 3 (Numerical Example 3) shown in Fig. 11 is a zoom optical system with an aperture ratio of about 5.6 and a half field angle of about 48.7° at the wide-angle end, and an aperture ratio of about 5.6 and a half field angle of about 19.8° at the telephoto end.

[0056] The optical system of this example is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, and a fifth lens group L5 with negative refractive power, which are arranged in order from the object side to the image side. When zooming, the first lens group L1, the third lens group L3, and the fifth lens group L5 do not move. When zooming from the wide-angle end to the telephoto end, the second lens group L2 moves toward the image side and the fourth lens group L4 moves toward the object side. When adjusting the focus from an infinite object to a close object, the fourth lens group L4 moves toward the object side.

[0057] The third lens group L3 includes a first reflecting surface M1 and a second reflecting surface M2, and an aperture stop SP is arranged between the first reflecting surface M1 and the second reflecting surface M2. Also, between the first reflecting surface M1 and the aperture stop SP (the second reflecting surface M2) in the third lens group L3, a partial group GM composed of a cemented lens in which a negative lens and a positive lens are cemented is arranged.

[0058] Figures 12 and 13 respectively show the longitudinal aberration of the optical system of Numerical Example 3 in the wide-angle end and the infinite-focus state and the close-focus state. Figures 14 and 15 respectively show the longitudinal aberration of the optical system of Numerical Example 3 in the telephoto end and the infinite-focus state and the close-focus state.

Example

[0059] The optical system of Example 4 (numerical example 4) shown in FIG. 16 is a zoom optical system with an aperture ratio of about 4.0 and a half field angle of about 34.8° at the wide-angle end, and an aperture ratio of about 4.0 and a half field angle of about 17.2° at the telephoto end.

[0060] The optical system of this example is composed of a first lens group L1 with a positive refractive power, a second lens group L2 with a negative refractive power, a third lens group L3 with a positive refractive power, and a fourth lens group L4 with a positive refractive power, which are arranged in order from the object side to the image side. When zooming, the first lens group L1 and the third lens group L3 do not move. When zooming from the wide-angle end to the telephoto end, the second lens group L2 moves toward the image side and the fourth lens group L4 moves toward the object side. When focusing from an infinite object to a near object, the fourth lens group L4 moves toward the object side.

[0061] The third lens group L3 includes a first reflecting surface M1 and a second reflecting surface M2, and an aperture stop SP is arranged between the first reflecting surface M1 and the second reflecting surface M2. Also, between the first reflecting surface M1 and the aperture stop SP (the second reflecting surface M2) in the third lens group L3, a partial group GM composed of a cemented lens in which a negative lens and a positive lens are cemented is arranged.

[0062] FIG. 17 and FIG. 18 respectively show the longitudinal aberration of the optical system of numerical example 4 in the wide-angle end and in the infinite-focus state and the near-focus state. FIG. 19 and FIG. 20 respectively show the longitudinal aberration of the optical system of numerical example 4 in the telephoto end and in the infinite-focus state and the near-focus state.

[0063] Hereinafter, numerical examples 1 to 4 are shown. Note that for numerical examples 1 to 3, a baseline length of 80 mm is set, and for numerical example 4, a baseline length of 70 mm is set.

[0064] In each numerical example, 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, and 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 (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines, respectively.

[0065] 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 lens length 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, and the overall lens length at the wide-angle end corresponds to the overall optical length Lw in Equation (2).

[0066] The "*" attached to the surface number means that the surface has an aspherical shape. The aspherical shape is expressed by the following equation 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.

[0067] 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 Furthermore, at the end of each numerical example, the movement amount of the focus lens group (the fourth lens group L4) from the wide-angle end and the infinite focus state to the close-focus state, and the movement amount of the focus lens group from the telephoto end and the infinite focus state to the close-focus state are shown. The movement amount of the focus lens group is the difference between the position of the focus lens group in the infinite focus state and the position of the focus lens group at the telephoto end, and a case where the focus lens group is located on the image side in the close-focus state with respect to the infinite focus state is taken as positive.

[0068] The values corresponding to the conditions of the above-described formulas (1) to (9) in Numerical Examples 1 to 6 are collectively shown in Table 1. Each numerical example satisfies all the conditions of formulas (1) to (9). [Numerical Example 1] Unit: mm Surface data Surface number r d nd νd 1 288.733 2.70 1.80810 22.8 2 83.557 6.28 1.72916 54.7 3 -1363.692 0.13 4 40.455 3.98 1.85838 42.4 5 65.589 (Variable) 6 53.435 1.50 2.00100 29.1 7 11.444 4.93 8 -109.225 1.00 1.88300 40.8 9 29.873 3.06 10 -47.855 1.00 1.88300 40.8 11 -124.802 0.20 12 30.283 3.08 1.80810 22.8 13 -165.831 (Variable) 14 ∞ 8.00 1.60311 60.6 15 ∞ 8.00 1.60311 60.6 16 ∞ 1.00 17 163.860 1.00 1.77580 49.0 18 12.803 5.75 1.72916 54.7 19 -48.936 3.00 20 (Aperture) ∞ 4.00 21 ∞ 8.00 1.60311 60.6 22 ∞ 8.00 1.60311 60.6 23 ∞ 1.00 24 15.958 4.00 2.00100 29.1 25 13.937 (Variable) 26 15.396 3.01 1.49700 81.5 27 -500.909 0.20 28 46.329 0.80 2.00100 29.1 29 13.934 3.62 1.49700 81.5 30 -41.238 0.20 31 17.677 4.24 1.69895 30.1 32 -15.252 0.79 1.86769 41.8 33 20.913 (Variable) 34 26.682 0.80 2.00100 29.1 35 12.126 3.49 1.49700 81.5 36 3125.864 13.50 Image plane ∞ Various data Zoom ratio 2.92 Wide angle Middle Telephoto Focal length 9.49 14.56 27.66 F-number 4.00 4.00 4.00 Half field angle (°) 39.05 30.43 17.17 Overall lens length 159.15 159.15 159.15 BF 13.50 13.50 13.50 d 5 0.70 13.14 25.58 d13 26.88 14.44 2.00 d25 16.24 11.46 2.31 d33 5.07 9.85 19.00 Lens group data Group starting surface Focal length 1 1 90.24 2 6 -12.67 3 14 55.16 4 26 34.30 5 34 -279.18 First reflecting surface M1 15 Second reflecting surface M2 22 Focus lens group Starting surface 26 End surface 33 Movement amount of the focus lens group to the close - focusing state (-0.5 m) at the wide - angle end -0.23 (mm) Movement amount of the focus lens group to the close - focusing state (-1.0 m) at the telephoto end -0.91 (mm) [Numerical example 2] Unit: mm Surface data Surface number r d nd νd 1 2607.354 2.70 1.80810 22.8 2 53.754 8.78 1.60311 60.6 3 638.030 0.20 4 83.680 5.00 1.83481 42.7 5 377.126 0.20 6 37.634 6.87 1.88148 40.5 7 85.603 (Variable) 8* -437.903 1.50 1.59201 67.0 9 8.841 6.30 10 -14.111 1.00 1.48749 70.2 11 -51.597 0.20 12 38.160 2.11 1.80810 22.8 13 -571.101 (Variable) 14 ∞ 8.00 1.60311 60.6 15 ∞ 8.00 1.60311 60.6 16 ∞ 1.00 17 241.799 1.00 1.90984 37.4 18 13.972 5.53 1.72916 54.7 19 -30.309 3.22 20 (Aperture) ∞ 4.00 21 ∞ 8.00 1.60311 60.6 22 ∞ 8.00 1.60311 60.6 23 ∞ 1.00 24 20.935 4.00 2.00100 29.1 25 23.685 (Variable) 26 88.819 2.55 1.60311 60.6 27 -24.461 2.98 28 35.507 4.02 1.48749 70.2 29 -14.467 0.79 2.00096 28.3 30 -56.140 (Variable) 31 -5132.513 0.80 1.77250 49.6 32 14.179 3.86 1.49700 81.5 33 -49.224 13.50 Image plane ∞ Aspherical data 8th surface K = 0.00000e+00 A 4= 7.25708e-05 A 6=-3.54113e-07 A 8= 1.63113e-09 A10=-3.97443e-12 Various data Zoom ratio 2.43 Wide angle Middle Telephoto Focal length 13.86 14.85 33.58 F number 4.00 4.00 4.00 Half angle of view (°) 31.67 29.94 14.28 Overall lens length 133.49 135.40 145.62 BF 13.50 13.50 13.50 d7 0.84 3.17 21.50 d13 10.53 10.10 2.00 d25 2.09 2.09 2.09 d30 4.93 4.93 4.93 Lens group data Group Starting surface Focal length 1 1 56.60 2 8 -14.52 3 14 41.63 4 26 33.76 5 31 -111.41 First reflecting surface M1 15 Second reflecting surface M2 22 Focus lens group Starting surface 26 Ending surface 30 Movement amount of the focus lens group to the close focusing state (-0.5 m) at the wide-angle end -0.37 (mm) Movement amount of the focus lens group to the close focusing state (-1.5 m) at the telephoto end -0.59 (mm) [Numerical example 3] Unit mm Surface data Surface number r d nd νd 1 52.704 2.90 1.80810 22.8 2 41.136 9.27 1.72916 54.7 3 78.200 (variable) 4* 122.204 1.60 1.85400 40.4 5 17.266 8.90 6 -45.084 1.10 1.88300 40.8 7 20.764 0.76 8 23.807 4.37 1.80810 22.8 9 295.963 (Variable) 10 ∞ 7.00 1.60311 60.6 11 ∞ 7.00 1.60311 60.6 12 ∞ 1.04 13 -153.632 1.00 1.53269 66.6 14 14.946 7.71 1.48749 70.2 15 -42.890 3.00 16 (Aperture) ∞ 4.00 17 ∞ 7.00 1.60311 60.6 18 ∞ 7.00 1.60311 60.6 19 ∞ 1.00 20 47.103 4.00 2.00100 29.1 21 69.505 (Variable) 22* 10.955 6.74 1.49710 81.6 23 -39.985 0.20 24 87.323 0.80 1.88300 40.8 25 8.324 3.45 1.49700 81.5 26 323.109 0.20 27 108.869 3.48 1.69895 30.1 28 -8.755 0.79 1.89826 38.8 29 -60.102 (Variable) 30 37.409 0.80 1.88300 40.8 31 10.416 3.53 1.49700 81.5 32 -165.808 16.91 Image plane ∞ Aspherical data Fourth surface K = 0.00000e+00 A 4= 1.30577e-05 A 6= 1.74397e-08 A 8=-1.06744e-10 A10= 1.75114e-13 The 22nd surface K = 0.00000e+00 A 4=-3.57428e-05 A 6=-3.03374e-07 A 8= 1.95630e-10 A10=-4.04960e-11 Various data Zoom ratio 3.15 Wide angle Middle Telephoto Focal length 7.52 11.61 23.71 F number 5.60 5.60 5.60 Half angle of view (°) 48.66 36.38 19.83 Overall lens length 179.72 179.72 179.72 BF 16.91 16.91 16.91 d 3 0.70 19.64 38.59 d 9 40.12 21.18 2.23 d21 18.17 13.53 1.92 d29 5.18 9.82 21.43 Lens group data Group Starting surface Focal length 1 1 198.46 2 4 -12.14 3 10 80.01 4 22 37.84 5 30 -99.77 The 1st reflecting surface M1 11 The 2nd reflecting surface M2 18 Focus lens group Starting surface 22 Ending surface 29 Movement amount of the focus lens group to the close focusing state (-0.5 m) at the wide angle end -0.11 (mm) Movement amount of the focus lens group to the close - distance focusing state (-1.0 m) at the far - end: -0.52 (mm) [Numerical example 4] Unit: mm Surface data Surface number r d nd νd 1 66.529 2.50 1.84666 23.8 2 44.459 6.78 1.72916 54.7 3 303.617 (variable) 4 49.566 1.50 1.83481 42.7 5 11.682 5.98 6 -50.450 1.00 1.72916 54.7 7 34.160 3.31 8 29.572 2.92 1.84666 23.8 9 558.484 (variable) 10 ∞ 6.70 1.51633 64.1 11 ∞ 6.70 1.51633 64.1 12 ∞ 1.00 13 154.682 1.00 1.85123 37.8 14 17.252 6.35 1.72916 54.7 15 -39.355 2.00 16 (aperture) ∞ 2.00 17 ∞ 6.70 1.51633 64.1 18 ∞ 6.70 1.51633 64.1 19 ∞ (variable) 20 15.001 3.66 1.49700 81.5 21 169.042 4.62 22 26.128 0.80 1.90043 37.4 23 12.047 4.18 1.49700 81.5 24 -65.731 0.20 25 24.487 4.61 1.59270 35.3 26 -10.743 0.79 1.88697 40.2 27 27.201 (variable) Image plane ∞ Various data Zoom ratio 2.50 Wide angle Intermediate Telephoto Focal length 11.07 16.30 27.66 F number 4.00 4.00 4.00 Half field angle (°) 34.81 27.67 17.18 Overall lens length 144.46 144.46 144.46 BF 14.14 18.12 25.24 d 3 1.01 14.35 27.68 d 9 28.75 15.41 2.08 d19 18.56 14.57 7.45 d27 14.14 18.12 25.24 Lens group data Group Starting surface Focal length 1 1 127.16 2 4 -17.93 3 10 58.73 4 20 43.07 First reflecting surface M1 11 Second reflecting surface M2 18 Focus lens group Starting surface 20 End surface 27 Movement amount of the focus lens group to the close - focus state (-0.5 m) at the wide - angle end -0.33 (mm) Movement amount of the focus lens group to the close - focus state (-1.0 m) at the telephoto end -0.85 (mm)

[0069]

Table 1

[0070] [Imaging device] Figure 23 shows an imaging device (single-lens reflex digital camera) equipped with the stereo optical system of any one of Embodiments 1 to 4. In Figure 23, reference numeral 10 denotes a lens device having the stereo optical system of any one of Embodiments 1 to 4 as an imaging optical system 1. The photographing optical system 1 is held by a lens barrel member 2. The lens device 10 is detachably attached to the camera body 20.

[0071] The camera body 20 includes a quick return mirror 3 that reflects the light beam from the lens device 10 upward, a focusing screen 4 disposed at a position where an inverted image of the subject image is formed by the imaging optical system 1, and a penta dach prism 5 that converts the inverted image formed on the focusing screen 4 into an erect image. The camera body 20 also includes an eyepiece lens 6 for the user to observe the erect image (finder image).

[0072] Reference numeral 7 denotes an imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor. The quick return mirror 3 disposed in the optical path during observation of the finder image retracts out of the optical path during imaging. Thereby, the subject image is formed on the imaging surface of the imaging element 7. The imaging element 7 photoelectrically converts the subject image (that is, captures the subject) and outputs image data.

[0073] Note that the lens device 10 may be detachably attached to a mirrorless camera that does not have a quick return mirror, or may be provided integrally with the imaging device.

[0074] As described above, by using the stereo optical system of each embodiment for various imaging devices such as digital cameras and video cameras, it is possible to obtain a high-quality captured image with good stereoscopic vision.

[0075] The above embodiments include the following configurations.

[0076] (Configuration 1) A stereo optical system having two variably magnifiable 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 at least one lens group, which are arranged in order from the object side to the image side. When zooming, the distance between adjacent lens groups changes. The third lens group includes a first reflecting surface and a second reflecting surface. 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. In each of the two optical systems, at least the second lens group moves when zooming. When the focal length at the wide-angle end of the optical system is fw and the focal length of the first lens group is f1, 3.5 ≦ f1 / fw ≦ 32.0 A stereo optical system characterized by satisfying the above conditions. (Configuration 2) The stereo optical system according to Configuration 1, wherein each of the two optical systems has a configuration that does not form an intermediate image. (Configuration 3) The stereo optical system according to Configuration 1 or 2, wherein the third lens group does not move when zooming. (Configuration 4) The stereo optical system according to any one of Configurations 1 to 3, wherein an aperture stop is arranged between the first reflecting surface and the second reflecting surface in the third lens group. (Configuration 5) The stereo optical system according to any one of Configurations 1 to 4, wherein when zooming, the second lens group and the fourth lens group, which is the most object-side lens group in the first lens group or the rear group, move. (Configuration 6) When the distance on the optical axis between the first reflecting surface and the second reflecting surface is Dm and the optical overall length at the wide-angle end of each of the two optical systems is Lw, 0.05 ≦ Dm / Lw ≦ 0.50 The stereo optical system according to any one of Configurations 1 to 5, characterized by satisfying the above conditions. (Configuration 7) When the distance on the optical axis between the first reflecting surface and the second reflecting surface is Dm, and the focal length of the subgroup disposed between the first reflecting surface and the second reflecting surface in the third lens group is fm, 0.05 ≦ Dm / fm ≦ 0.80 The stereo optical system according to any one of Configurations 1 to 6, characterized in that the condition is satisfied. (Configuration 8) When the thickness on the optical axis from the most object-side surface to the most image-side surface of the first lens group is D1, and the thickness on the optical axis from the most object-side surface to the most image-side surface of the third lens group is D3, 1.7 ≦ D3 / D1 ≦ 10.0 The stereo optical system according to any one of Configurations 1 or 73, characterized in that the condition is satisfied. (Configuration 9) When the distance on the optical axis between the first reflecting surface and the second reflecting surface is Dm, and the thickness on the optical axis from the most object-side surface to the most image-side surface of the first lens group is D1, 0.9 ≦ Dm / D1 ≦ 5.0 The stereo optical system according to any one of Configurations 1 to 8, characterized in that the condition is satisfied. (Configuration 10) When the thickness on the optical axis from the most object-side surface to the most image-side surface of the first lens group is D1, and the thickness on the optical axis from the most object-side surface to the most image-side surface of the second lens group is D2, 0.35 ≦ D2 / D1 ≦ 2.50 The stereo optical system according to any one of Configurations 1 to 9, characterized in that the condition is satisfied. (Configuration 11) The third lens group includes an aperture stop, When the distance on the optical axis between the first reflecting surface and the aperture stop is dp1, and the distance on the optical axis between the first reflecting surface and the second reflecting surface is Dm, 0.30 ≦ dp1 / Dm ≦ 0.90 The stereo optical system according to any one of Configurations 1 to 10, characterized in that the condition is satisfied. (Configuration 12) When the focal length of the third lens group L3 is f3 and the distance on the optical axis between the first reflecting surface and the second reflecting surface is Dm, 0.9 ≦ f3 / Dm ≦ 3.5 The stereo optical system according to any one of Configurations 1 to 11, characterized by satisfying the condition. (Configuration 13) When the interval between the optical axes between the first lens groups in each of the two optical systems is Din and the interval between the optical axes of the rear group is Dout, 0.05 ≦ Dout / Din ≦ 0.50 The stereo optical system according to any one of Configurations 1 to 12, characterized by satisfying the condition. (Configuration 14) The lens groups arranged in order from the object side to the image side in each of the two optical systems are composed of the first lens group, the second lens group, the third lens group with positive refractive power, the fourth lens group with positive refractive power, and the fifth lens group with negative refractive power. During zooming, The first lens group, the third lens group, and the fifth lens group do not move. The stereo optical system according to any one of Configurations 1 to 13, characterized in that the second lens group and the fourth lens group move. (Configuration 15) The lens groups arranged in order from the object side to the image side in each of the two optical systems are composed of the first lens group, the second lens group, the third lens group with positive refractive power, the fourth lens group with positive refractive power, and the fifth lens group with negative refractive power. During zooming, The third lens group, the fourth lens group, and the fifth lens group do not move. The stereo optical system according to any one of Configurations 1 to 13, characterized in that the first lens group and the second lens group move. (Configuration 16) The lens groups arranged in order from the object side to the image side in each of the two optical systems are composed of the first lens group, the second lens group, the third lens group with positive refractive power, and the fourth lens group with positive refractive power. Upon zooming, the first lens group and the third lens group do not move, The stereo optical system according to any one of Configurations 1 to 13, wherein the second lens group and the fourth lens group move. (Configuration 17) A stereo optical system according to any one of Configurations 1 to 16, and an imaging device having an imaging element that images a subject through the stereo optical system.

[0077] 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

[0078] L1 First lens group L2 Second lens group L3 Third lens group L4 Fourth lens group L5 Fifth lens group LR Rear group M1 First reflecting surface M2 Second reflecting surface SP Aperture stop

Claims

1. A stereo optical system having two variably magnifiable optical systems arranged in parallel, wherein 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 rear group including at least one 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 and a second reflecting surface, 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, in each of the two optical systems, at least the second lens group moves during zooming, when the focal length at the wide-angle end of the optical system is fw and the focal length of the first lens group is f1, 3.5 ≤ f1 / fw ≤ 32.0 A stereo optical system characterized by satisfying the above conditions.

2. The stereo optical system according to claim 1, wherein each of the two optical systems has a configuration that does not form an intermediate image.

3. The stereo optical system according to claim 1, wherein the third lens group does not move during zooming.

4. The stereo optical system according to claim 1, wherein an aperture stop is arranged between the first reflecting surface and the second reflecting surface in the third lens group.

5. The stereo optical system according to claim 1, wherein during zooming, the second lens group and the fourth lens group, which is the most object-side lens group in the first lens group or the rear group, move.

6. When the distance on the optical axis between the first reflecting surface and the second reflecting surface is Dm and the optical overall length at the wide-angle end of each of the two optical systems is Lw, 0.05 ≤ Dm / Lw ≤ 0.50 A stereo optical system characterized by satisfying the above conditions.

7. When the distance on the optical axis between the first reflecting surface and the second reflecting surface is Dm and the focal length of the partial group arranged between the first reflecting surface and the second reflecting surface in the third lens group is fm, 0.05 ≤ Dm / fm ≤ 0.80 A stereo optical system characterized by satisfying the above conditions.

8. When the thickness on the optical axis from the most object-side surface to the most image-side surface of the first lens group is D1 and the thickness on the optical axis from the most object-side surface to the most image-side surface of the third lens group is D3, 1.7 ≤ D3 / D1 ≤ 10.0 The stereo optical system according to claim 1, characterized by satisfying the following conditions.

9. When the distance on the optical axis between the first reflecting surface and the second reflecting surface is Dm, and the thickness on the optical axis from the most object-side surface of the first lens group to the most image-side surface of the first lens group is D1, 0.9 ≦ Dm / D1 ≦ 5.0 The stereo optical system according to claim 1, characterized by satisfying the following conditions.

10. When the thickness on the optical axis from the most object-side surface of the first lens group to the most image-side surface of the first lens group is D1, and the thickness on the optical axis from the most object-side surface of the second lens group to the most image-side surface of the second lens group is D2, 0.35 ≦ D2 / D1 ≦ 2.50 The stereo optical system according to claim 1, characterized by satisfying the following conditions.

11. The third lens group includes an aperture stop. When the distance on the optical axis between the first reflecting surface and the aperture stop is dp1, and the distance on the optical axis between the first reflecting surface and the second reflecting surface is Dm, 0.30 ≦ dp1 / Dm ≦ 0.90 The stereo optical system according to claim 1, characterized by satisfying the following conditions.

12. When the focal length of the third lens group L3 is f3, and the distance on the optical axis between the first reflecting surface and the second reflecting surface is Dm, 0.9 ≦ f3 / Dm ≦ 3.5 The stereo optical system according to claim 1, characterized by satisfying the following conditions.

13. When the distance between the optical axes of the first lens groups in each of the two optical systems is Din, and the distance between the optical axes of the rear group is Dout, 0.05 ≦ Dout / Din ≦ 0.50 The stereo optical system according to claim 1, characterized by satisfying the following conditions.

14. The lens groups arranged in order from the object side to the image side in each of the two optical systems are composed of the first lens group, the second lens group, the third lens group with positive refractive power, the fourth lens group with positive refractive power, and the fifth lens group with negative refractive power. During zooming, The first lens group, the third lens group, and the fifth lens group do not move. The stereo optical system according to claim 1, characterized in that the second lens group and the fourth lens group move.

15. The lens groups arranged in order from the object side to the image side in each of the two optical systems are composed of the first lens group, the second lens group, the third lens group with positive refractive power, the fourth lens group with positive refractive power, and the fifth lens group with negative refractive power. During zooming, The third lens group, the fourth lens group, and the fifth lens group do not move, The stereo optical system according to claim 1, wherein the first lens group and the second lens group move.

16. In each of the two optical systems, the lens groups arranged in order from the object side to the image side are composed of the first lens group, the second lens group, the third lens group having a positive refractive power, and the fourth lens group having a positive refractive power. During zooming, The first lens group and the third lens group do not move, The stereo optical system according to claim 1, wherein the second lens group and the fourth lens group move.

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

Images