Stereo optical system and imaging apparatus

Abstract

To provide a stereo optical system capable of taking an image with good stereoscopic effect while being small sized and with a large diameter.SOLUTION: A stereo optical system includes two optical systems OSR and OSL arranged in parallel. The two optical systems are co-axial optical systems, respectively, and include an aperture diaphragm SP and at least two positive lenses arranged closer to an image side than the aperture diaphragm. If a distance between optical axes of the two optical systems is D, focal distances of the two optical systems are respectively f, and maximum viewing angles of the two optical systems are respectively ω, a condition 1.8≤D / (f.tanω)≤5.5 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] 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 and Patent Document 2 disclose a stereo optical system that accommodates two image circles formed by two optical systems within the imaging plane of a single imaging device.

[0003] In the stereo optical system of Patent Document 1, by using two reflecting surfaces that bend the optical paths in the middle of each of the two optical systems, two image circles are accommodated within a single imaging plane while ensuring a sufficient baseline length. In the stereo optical system of Patent Document 2, two coaxial optical systems are arranged with a small baseline length to accommodate two image circles within a single imaging plane.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the stereo optical system of Patent Document 1, a sufficient baseline length can be ensured, but since two reflecting surfaces are used for each of the two optical systems, the stereo optical system becomes larger in size.

[0006] In addition, in the stereo optical system of Patent Document 2, a coaxial optical system that does not include a reflecting surface is used. However, since the baseline length is small, the three-dimensional effect of the obtained image is weakened. Moreover, since a pan-focus type optical system without a focus mechanism is used for miniaturization, the F-number increases (becomes darker), and it is difficult to generate the blur for easily obtaining the three-dimensional effect. Furthermore, since the number of lenses is reduced for weight reduction, the incident angle of off-axis light rays on the imaging surface is large, and since the off-axis light rays enter the imaging surface in the opposite direction to the off-axis light rays from a general monocular optical system, the image quality is likely to deteriorate due to coloration of the image generated on the imaging surface (hereinafter referred to as color shading).

[0007] The present invention provides a stereo optical system capable of imaging for obtaining a large aperture and a good three-dimensional effect while being small, and an imaging device including the same.

Means for Solving the Problems

[0008] The stereo optical system as one aspect of the present invention has two optical systems arranged in parallel. Each of the two optical systems is a coaxial optical system, and has an aperture stop and at least two positive lenses arranged on the image side of the aperture stop. When the distance between the optical axes of the two optical systems is D, the focal length of each of the two optical systems is f, and the maximum angle of view of each of the two optical systems is ω, 1.8 ≦ D / (f · tan ω) ≦ 5.5 It is characterized by satisfying the following conditions. Note that an imaging device including the above stereo optical system also constitutes another aspect of the present invention.

Effects of the Invention

[0009] According to the present invention, it is possible to provide a stereo optical system capable of imaging for obtaining a large aperture and a good three-dimensional effect while being small.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 5

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Figure 7

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Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Best Mode for Carrying Out the Invention

[0011] Hereinafter, examples of the present invention will be described with reference to the drawings.

[0012] Before explaining Specific Examples 1 to 5, matters common to each example will be described. FIG. 11 shows the stereo optical system of Example 1 as a representative example viewed from above. The stereo optical system of each example is composed of a right optical system OSR and a left optical system OSL as two coaxial optical systems arranged in parallel. These right optical system OSR and left optical system OSL are arranged such that their optical axes extend parallel to each other with a baseline length D, which is the distance between their optical axes. The right optical system OSR and the left optical system OSL each have an aperture stop SP. IP indicates the image plane. On the image plane IP, the imaging surface (light-receiving surface) of the imaging device or the film surface (photosensitive surface) of the silver halide film is arranged.

[0013] FIGS. 1, 3, 5, 7, and 9 each show a cross-section of one of the right optical system OSR and the left optical system OSL that make up the stereo optical system of Examples 1 to 5 in a state of being focused on an infinite object (hereinafter referred to as the infinite focus state).

[0014] Each optical system (OSR and OSL) has a front lens group F, an aperture stop SP, and a rear lens group R arranged in order from the object side to the image side. The rear lens group R includes at least two positive lenses (a first positive lens Rp1 and a second positive lens Rp2).

[0015] FIG. 12 shows an image circle ICR formed on the image plane IP (for example, the imaging surface of a single imaging device) by the right optical system OSR and an image circle ICL formed on the same image plane IP by the left optical system OSL. The right image circle ICR and the left image circle ICL are formed side by side on the image plane IP. Thereby, an imaging device such as a digital camera equipped with a single imaging device can acquire two imaging images (a pair of parallax images) that have parallax with each other and enable stereoscopic viewing.

[0016] In each embodiment, each optical system realizes wide-angle conversion of the optical system by arranging a negative lens Fn on the most object side in the front lens group F. Further, each optical system arranges a second positive lens Rp2 on the most image side in the rear lens group R, and arranges negative lenses (a first negative lens Rn1 and a second negative lens Rn2) on the object side of the second positive lens Rp2, thereby reducing the incident angle of off-axis light rays on the image plane (the imaging plane of the imaging device) IP. As a result, reduction of color shading generated in the imaging device is realized.

[0017] Furthermore, each optical system arranges a first positive lens Rp1 having a high refractive index on the object side of the second positive lens Rp2 on the most image side in the rear lens group R, thereby favorably correcting spherical aberration generated in the first negative lens Rn1 while efficiently converging light rays. As a result, both large aperture and miniaturization of the optical system are achieved.

[0018] In each optical system of each embodiment, the whole or a part of the optical system moves on the optical axis during focusing. In FIGS. 1, 3, 5, 7, and 9, the moving directions of lenses and an aperture stop SP that move during focusing from an infinite object to a near-distance object are indicated by arrows.

[0019] Each optical system of each embodiment satisfies the condition of the following formula (1) when the baseline length is D, the focal length of the entire optical system is f, and the maximum angle of view of the optical system is ω.

[0020] 1.8 ≦ D / (f·tan ω) ≦ 5.5 (1) The condition of formula (1) shows an appropriate relationship between the baseline length and the size of the imaging device in order to obtain good stereoscopic effect from two captured images while improving the image quality of each captured image. If the baseline length D increases so that D / (f·tan ω) exceeds the upper limit of formula (1), the size of the image circle on the imaging device becomes too small and the image quality of the captured image deteriorates, which is not preferable. If the baseline length D decreases so that D / (f·tan ω) is below the lower limit of formula (1), the stereoscopic effect obtained from two captured images weakens, and two image circles overlap on the imaging device, and an appropriate parallax image cannot be obtained, which is not preferable.

[0021] In addition, it is more preferable if the numerical range of formula (1) is as follows.

[0022] 1.9 ≦ D / (f·tanω) ≦ 5.0 (1a) Also, it is even more preferable if the numerical range of formula (1) is as follows.

[0023] 2.0 ≦ D / (f·tanω) ≦ 4.5 (1b) With the above configuration and by satisfying the conditions of formula (1), it is possible to perform good stereoscopic imaging while being small-sized and having a small baseline length, and a large-aperture and high-performance stereo optical system can be realized.

[0024] Each optical system in each embodiment preferably satisfies at least one of the conditions of the following formulas (2) to (12). In these formulas, the focal length of the front lens group F on the object side with respect to the aperture stop SP is fF, and the focal length of the rear lens group R on the image side with respect to the aperture stop SP is fR. The focal length of the first negative lens Rn1 with the strongest refractive power among at least one negative lens included in the rear lens group R is fRn1. In the rear lens group R, the focal length of the second positive lens Rp2 with the strongest refractive power among at least one positive lens arranged on the image side with respect to the first negative lens Rn1 is fRp2. In the rear lens group R, the focal length of the first positive lens Rp1 with the strongest refractive power among at least one positive lens arranged on the object side with respect to the second lens Rp2 is fRp1.

[0025] Also, the focal length of the positive lens Fp with the strongest refractive power among at least one positive lens included in the front lens group F is fFp. In the front lens group F, the focal length of the negative lens Fn with the strongest refractive power arranged on the object side with respect to the positive lens Fp is fFn.

[0026] Further, let the radius of curvature of the image-side surface of the first negative lens Rn1 be R1, and the radius of curvature of the object-side surface of the second negative lens Rn2 adjacent to the first negative lens Rn1 with an air gap on the image side be R2. Let the refractive index of the material of the first positive lens Rp1 at the d-line be ndRp1. Let the length on the optical axis from the most object-side surface (frontmost surface) of the optical system to the image plane IP (overall optical length) in the infinite-focus state be L, the back focus of the optical system in the infinite-focus state be sk, and the distance on the optical axis from the frontmost surface of the optical system to the entrance pupil position be t1.

[0027] -1.0 ≦ f / fF ≦ 1.4 (2) -0.9 ≦ fR / fF ≦ 2.4 (3) -6.0 ≦ fR / fRn1 ≦ -1.4 (4) -3.2 ≦ fRp2 / fRn1 ≦ -1.0 (5) 0.4 ≦ fRp2 / fRp1 ≦ 4.5 (6) -2.0 ≦ fFn / fFp ≦ -0.1 (7) -0.8 ≦ (R2 + R1) / (R2 - R1) ≦ 0.3 (8) 1.6 ≦ ndRp1 ≦ 2.2 (9) 2.0 ≦ L / f ≦ 5.5 (10) 0.3 ≦ sk / f ≦ 0.9 (11) 0.2 ≦ t1 / f ≦ 1.3 (12) The condition of formula (2) shows an appropriate relationship between the focal length of the entire optical system and the focal length of the front lens group F in order to suppress coma aberration and distortion aberration in the entire optical system while ensuring the back focus of the optical system. If the positive refractive power of the front lens group F becomes strong such that f / fF exceeds the upper limit of formula (2), the principal point position of the optical system moves to the object side, making it difficult to ensure the back focus, which is not preferable. If the negative refractive power of the front lens group F becomes strong such that f / fF is below the lower limit of formula (2), it becomes difficult to correct the coma aberration and distortion aberration generated in the rear lens group R, which is not preferable.

[0028] The condition of Equation (3) shows an appropriate relationship between the focal length of the rear lens group R and the focal length of the front lens group F in order to suppress spherical aberration in the entire optical system while miniaturizing the optical system. If the refractive power of the rear lens group R becomes weak such that fR / fF exceeds the upper limit of Equation (3), the overall length of the optical system increases, which is not preferable. If the refractive power of the rear lens group R becomes strong such that fR / fF is below the lower limit of Equation (3), it becomes difficult to correct the spherical aberration generated in the rear lens group R, which is not preferable.

[0029] The condition of Equation (4) shows an appropriate relationship between the focal length of the rear lens group R and the focal length of the first negative lens Rn1 in order to reduce color shading while suppressing the field curvature of the rear lens group R. If the refractive power of the first negative lens Rn1 becomes strong such that fR / fRn1 exceeds the upper limit of Equation (4), it becomes difficult to correct the field curvature generated in the rear lens group R, which is not preferable. If the refractive power of the first negative lens Rn1 becomes weak such that fR / fRn1 is below the lower limit of Equation (4), the incident height of off-axis light rays incident on the second positive lens Rp2 decreases, resulting in a large incident angle of light rays on the imaging device, and the occurrence of color shading becomes significant, which is not preferable.

[0030] The condition of Equation (5) shows an appropriate relationship between the focal length of the second positive lens Rp2 and the focal length of the first negative lens Rn1 in order to suppress coma aberration and distortion aberration generated in the rear lens group R while reducing color shading. If the refractive power of the second positive lens Rp2 becomes weak such that fRp2 / fRn1 exceeds the upper limit of Equation (5), the incident angle of light rays on the imaging device increases, and the occurrence of color shading becomes significant, which is not preferable. If the refractive power of the second positive lens Rp2 becomes strong such that fRp2 / fRn1 is below the lower limit of Equation (5), it becomes difficult to correct the coma aberration and distortion aberration generated in the second positive lens Rp2, which is not preferable.

[0031] The condition of Equation (6) shows an appropriate relationship between the focal length of the second positive lens Rp2 and the focal length of the first positive lens Rp1 in order to miniaturize the optical system while suppressing the spherical aberration generated in the rear lens group R. If the refractive power of the first positive lens Rp1 becomes strong such that fRp2 / fRp1 exceeds the upper limit of Equation (6), it becomes difficult to correct the spherical aberration generated in the first positive lens Rp1, which is not preferable. If the refractive power of the first positive lens Rp1 becomes weak such that fRp2 / fRp1 is below the lower limit of Equation (6), the overall length of the optical system increases and the optical system becomes large, which is not preferable.

[0032] The condition of Equation (7) shows an appropriate relationship between the focal length of the negative lens Fn and the focal length of the positive lens Fp within the front lens group F in order to miniaturize the optical system while suppressing the spherical aberration generated in the front lens group F. If the refractive power of the positive lens Fp becomes strong such that fFn / fFp exceeds the upper limit of (7), it becomes difficult to correct the spherical aberration generated in the positive lens Fp, which is not preferable. If the refractive power of the positive lens Fp becomes weak such that fFn / fFp is below the lower limit value of (7), the overall length of the optical system increases and the optical system becomes large, which is not preferable.

[0033] The condition of Equation (8) shows an appropriate range of the shape factor of the air lens between the first negative lens Rn1 and the second negative lens Rn2 in order to suppress the field curvature and coma aberration generated in the rear lens group R. If the radius of curvature of the object side surface of the second negative lens Rn2 becomes large such that (R2 + R1) / (R2 - R1) exceeds the upper limit of Equation (8), it becomes difficult to correct the field curvature generated in the rear lens group R, which is not preferable. If the radius of curvature of the object side surface of the second negative lens Rn2 becomes small such that (R2 + R1) / (R2 - R1) is below the lower limit of Equation (8), it becomes difficult to correct the coma aberration generated in the rear lens group R, which is not preferable.

[0034] The condition of Equation (9) indicates an appropriate range of the refractive index of the material of the first positive lens Rp1 for suppressing the spherical aberration and axial chromatic aberration generated by the first positive lens Rp1 while miniaturizing the optical system. When the refractive index of the material of the first positive lens Rp1 becomes high such that ndRp1 exceeds the upper limit of Equation (9), the dispersion of the lens increases, making it difficult to correct the axial chromatic aberration generated by the first positive lens Rp1, which is not preferable. When the refractive index of the material of the first positive lens Rp1 becomes low such that ndRp1 is below the lower limit of Equation (9), the radius of curvature of that surface becomes small when giving the refractive power required for the first positive lens Rp1, making it difficult to correct the spherical aberration generated by the first positive lens Rp1, which is not preferable. On the other hand, reducing the refractive power of the first positive lens Rp1 weakens the converging action of light rays, expanding the overall length of the optical system and enlarging the optical system, which is not preferable.

[0035] The condition of Equation (10) indicates an appropriate relationship between the overall optical length of the optical system and the focal length of the entire optical system for achieving both miniaturization and high performance of the optical system. When the overall optical length of the optical system expands such that L / f exceeds the upper limit of Equation (10), the optical system becomes large, which is not preferable. When the overall optical length of the optical system shrinks such that L / f is below the lower limit of Equation (10), the radius of curvature of each lens surface becomes small, and the occurrence of higher-order aberrations becomes prominent, making it difficult to improve the performance of the optical system, which is not preferable.

[0036] The condition of Equation (11) indicates an appropriate relationship between the back focus of the optical system and the focal length of the entire optical system for achieving both miniaturization of the optical system and reduction of color shading. When the back focus of the optical system expands such that sk / f exceeds the upper limit of Equation (11), the overall optical length expands and the optical system becomes large, which is not preferable. When the back focus of the optical system shrinks such that sk / f is below the lower limit of Equation (11), the incident angle of light rays on the imaging element increases, and the occurrence of color shading becomes prominent, which is not preferable.

[0037] The condition of Equation (12) shows an appropriate relationship between the distance from the front surface of the optical system to the entrance pupil position and the focal length of the entire optical system in order to suppress coma aberration and distortion aberration of the entire optical system while miniaturizing the optical system. If the entrance pupil position moves toward the image side such that t1 / f exceeds the upper limit of Equation (12), the diameter of the most object-side lens increases and the optical system becomes larger, which is not preferable. If the entrance pupil position moves toward the object side such that t1 / f is below the lower limit of Equation (12), the negative refractive power of the front lens group F becomes too strong, making it difficult to correct the coma aberration and distortion aberration generated in the front lens group F, which is not preferable.

[0038] Note that it is more preferable if the numerical ranges of Equations (2) to (12) are as follows.

[0039] -0.6 ≦ f / fF ≦ 1.2 (2a) -0.7 ≦ fR / fF ≦ 2.2 (3a) -5.5 ≦ fR / fRn1 ≦ -1.6 (4a) -3.0 ≦ fRp2 / fRn1 ≦ -1.2 (5a) 0.8 ≦ fRp2 / fRp1 ≦ 4.0 (6a) -1.6 ≦ fFn / fFp ≦ -0.2 (7a) -0.7 ≦ (R2 + R1) / (R2 - R1) ≦ 0.2 (8a) 1.7 ≦ ndRp1 ≦ 2.1 (9a) 2.3 ≦ L / f ≦ 5.0 (10a) 0.40 ≦ sk / f ≦ 0.82 (11a) 0.3 ≦ t1 / f ≦ 1.2 (12a) Also, it is even more preferable if the numerical ranges of Equations (2) to (12) are as follows.

[0040] -0.4 ≦ f / fF ≦ 1.0 (2b) -0.5 ≦ fR / fF ≦ 2.0 (3b) -5.0 ≦ fR / fRn1 ≦ -1.8 (4b) -2.8 ≦ fRp2 / fRn1 ≦ -1.4 (5b) 1.0 ≦ fRp2 / fRp1 ≦ 3.5 (6b) -1.2 ≤ fFn / fFp ≤ -0.3 (7b) -0.6 ≤ (R2 + R1) / (R2 - R1) ≤ 0.1 (8b) 1.8 ≤ ndRp1 ≤ 2.0 (9b) 2.6 ≤ L / f ≤ 4.5 (10b) 0.5 ≤ sk / f ≤ 0.7 (11b) 0.4 ≤ t1 / f ≤ 1.1 (12b) Hereinafter, the optical systems of Examples 1 to 5 will be specifically described.

[0041] In Examples 1, 3, 4, and 5, the front lens group F is composed of a negative lens Fn and a positive lens Fp arranged in order from the object side. In Example 2, the front lens group F is composed of a negative lens Fn, a positive lens, and a positive lens Fp arranged in order from the object side.

[0042] In Examples 1, 2, 3, and 4, the rear lens group R is composed of a cemented lens in which a first positive lens Rp1 and a first negative lens Rn1 are cemented, a second negative lens Rn2, and a second positive lens Rp2, arranged in order from the object side. In Example 5, the rear lens group R is composed of a cemented lens in which a first positive lens Rp1 and a first negative lens Rn1 are cemented, a second negative lens Rn2, a second positive lens Rp2, and a third positive lens, arranged in order from the object side. As described above, the optical systems of each example are composed of six or more lenses (a cemented lens in which two lenses are cemented is counted as two lenses).

[0043] By arranging a negative lens on the most object side as in each example, a wide-angle of the optical system is realized.

[0044] Also, by arranging a first negative lens Rn1 and a second positive lens Rp2 on the image side with respect to the first negative lens Rn1 in the rear lens group R, the incident angle of off-axis light to the imaging element is reduced. Thereby, reduction of color shading is realized.

[0045] Also, by arranging the first positive lens Rp1 with a high refractive index of the material closer to the object side than the second positive lens Rp2 in the rear lens group R, it is possible to miniaturize the optical system by the good convergence action of light rays while satisfactorily correcting the spherical aberration generated in the first negative lens Rn1. Moreover, by arranging the second negative lens Rp2 adjacent to the first negative lens Rn1 with an air gap on the image side, it is possible to satisfactorily correct the coma aberration and the field curvature generated in the rear lens group R. By these means, both miniaturization and large aperture of the optical system are realized.

[0046] Also, regarding focusing, in Example 1, an overall extension method is adopted in which the entire optical system moves toward the object side when focusing from an infinite object to a near-distance object. In Example 2, a front focus method is adopted in which a partial group (the front lens group F, the aperture stop SP, and the first positive and first negative lenses Rp1 and Rn1 among the rear lens group R) including the lens closest to the object side of the optical system moves integrally toward the object side during the above focusing. Further, in Examples 3 and 4, a rear focus method is adopted in which a partial group including the lens closest to the image side of the optical system moves integrally during the above focusing. In Example 3, the aperture stop SP and the rear lens group R move integrally toward the object side, and in Example 4, the rear lens group R moves toward the object side. In Example 5, a floating focus method is adopted in which two different partial groups (the positive lens Fp of the front lens group F and the rear lens group R) of the optical system move toward the object side along different trajectories during the above focusing.

[0047] Hereinafter, numerical examples 1 to 5 corresponding to Examples 1 to 5 are shown. In each numerical example, the surface number 1 indicates the order of the surfaces from the object side. r is the radius of curvature (mm) of the i-th surface, d is the lens thickness or air gap on the optical axis between the i-th surface and the (i + 1)-th surface (mm), nd is the refractive index of the optical material at the d-line 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, and the effective diameter is the effective diameter of the light ray of the i-th surface.

[0048] The Abbe number νd with respect to the d-line is expressed as νd = (nd - 1) / (nF - nC), where nd, nF, and nC are the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines, respectively.

[0049] BF represents the back focus (mm). The back focus is the distance on the optical axis from the most image-side lens surface (the final surface) of the optical system to the paraxial image plane, expressed in air-equivalent length. The overall lens length (mm) 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, corresponding to the overall optical length.

[0050] The "*" attached to the surface number means that the surface is a lens surface with an aspherical shape. The aspherical shape is expressed by the following formula when x is the displacement amount from the surface vertex in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, the direction of light propagation is positive, R is the paraxial curvature radius, K is the conic constant, and A4, A6, A8, A10 are the aspherical coefficients. The "e±M" of the conic constant and aspherical coefficients means ×10 ±M is meant.

[0051] x=(h 2 / R) / [1+{1-(1+K)(h / R) 2}] 1 / 2 +A4×h 4 +A6×h 6 +A8×h 8 +A8×h 8 +A10×h 10 Also, the values of the conditions of the aforementioned formulas (1) to (12) in Numerical Examples 1 to 5 are summarized in Table 1. The optical systems of each numerical example satisfy all the conditions of formulas (1) to (12).

[0052] Figures 2, 4, 6, 8, and 10 respectively show the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the optical systems of Numerical Examples 1 to 5. In the spherical aberration figure, Fno indicates the F-number. The solid line represents the spherical aberration with respect to the d-line (wavelength 587.6 nm), and the two-dot chain line represents the spherical aberration with respect to the g-line (wavelength 435.8 nm). In the astigmatism figure, the solid line ΔS represents the astigmatism of the sagittal image plane, and the broken line ΔM represents the astigmatism of the meridional image plane. The distortion figure shows the distortion aberration with respect to the d-line. The chromatic aberration figure shows the longitudinal chromatic aberration at the g-line. ω is the semi-field angle (°).

[0053] [Numerical Example 1] Unit: mm Surface Data Surface No. r d nd νd Effective Diameter 1 16.997 1.07 1.49700 81.54 9.68 2 5.396 5.36 7.68 3* 22.689 2.36 1.53160 55.84 6.22 4* -53.190 2.31 6.38 5 (Aperture Stop) ∞ 1.35 6.53 6 9.291 5.00 1.81600 46.62 6.66 7 -9.291 0.87 1.69895 30.13 5.46 8 15.129 2.65 4.90 9* -3.947 1.30 1.63550 23.89 5.94 10* -5.679 2.86 7.28 11 19.265 5.40 1.53775 74.70 13.63 12 -19.265 (Variable) 14.66 Image Plane ∞ Aspherical Surface Data The Third Surface K = 0.00000e+000 A4 = 3.42924e-004 A6 = 5.40239e-008 A8 = 7.15673e-007 The 4th surface K = 0.00000e+000 A4 = -2.06201e-005 A6 = -3.16817e-006 A8 = 7.24155e-007 The 9th surface K = 0.00000e+000 A4 = 2.41018e-003 A6 = 1.49517e-004 A8 = 7.38145e-006 A10 = -8.67755e-007 A12 = 7.20535e-008 The 10th surface K = 0.00000e+000 A4 = 1.79265e-003 A6 = 7.50567e-005 A8 = 2.80419e-007 Various data Focal length 13.20 F-number 2.85 Half field angle (°) 31.23 Image height 8.00 Overall lens length 38.54 BF 8.00 Single lens data Lens starting surface Focal length 1 1 -16.41 2 3 30.25 3 6 6.48 4 7 -8.12 5 9 -28.77 6 11 18.84 [Numerical example 2] Unit: mm Surface data Surface number r d nd νd Effective diameter 1 20.324 0.92 1.59522 67.74 11.74 2 6.338 3.74 9.57 3 80.516 3.00 1.89286 20.36 8.99 4 -49.602 4.11 8.35 5* 456.535 3.00 1.53160 55.84 6.87 6* -9.213 2.05 7.14 7 (Diaphragm) ∞ 0.57 6.35 8 14.220 4.03 1.88300 40.76 6.10 9 -14.220 1.05 1.89286 20.36 4.85 10 9.514 2.32 4.32 11* -5.492 1.35 1.63550 23.89 6.41 12* -7.258 3.42 7.73 13 30.818 4.42 1.96300 24.11 14.50 14 -30.818 (Variable) 15.28 Image plane ∞ Aspherical data The 5th surface K = 0.00000e+000 A 4=-1.20930e-004 A 6=-1.54004e-006 A 8= 3.10157e-008 The 6th surface K = 0.00000e+000 A 4=-1.80501e-005 A 6=-1.39998e-006 A 8= 5.23245e-008 The 11th surface K = 0.00000e+000 A 4= 2.37707e-003 A 6=-1.46625e-005 A 8= 7.89300e-006 A10=-6.07443e-007 A12= 1.31406e-008 The 12th surface K = 0.00000e+000 A 4= 1.61376e-003 A 6= 6.13982e-006 A 8= 1.14249e-006 A10=-7.30382e-008 A12= 8.76937e-010 Various data Focal length 13.50 F number 2.85 Half picture angle (°) 30.65 Image height 8.00 Overall lens length 41.99 BF 8.00 Single lens data Lens starting surface focal length 1 1 -15.87 2 3 34.75 3 5 17.03 4 8 8.63 5 9 -6.25 6 11 -50.53 7 13 16.59 [Numerical example 3] Unit mm Surface data Surface number r d nd νd Effective diameter 1 15.477 1.64 1.49700 81.54 9.97 2 5.491 5.01 7.64 3* 34.014 2.38 1.53160 55.84 6.20 4* -57.423 2.62 6.42 5 (Aperture) ∞ 1.27 6.73 6 8.900 5.00 1.81600 46.62 6.95 7 -9.441 1.50 1.69895 30.13 5.75 8 14.193 2.79 4.93 9* -4.372 1.44 1.63550 23.8 6.02 10* -6.443 2.64 7.54 11 20.670 5.40 1.53775 74.70 13.47 12 -17.749 (Variable) 14.59 Image plane ∞ Aspherical data The 3rd surface K = 0.00000e+000 A 4= 3.82508e-004 A 6=-4.13980e-006 A 8= 1.12882e-006 A10=-3.79296e-008 A12= 7.27467e-010 Fourth surface K = 0.00000e+000 A 4= 4.87047e-005 A 6=-7.07670e-006 A 8= 1.06393e-006 A10=-5.13271e-008 A12= 1.69678e-009 Ninth surface K = 0.00000e+000 A 4= 9.24841e-004 A 6= 6.23435e-005 A 8= 7.91063e-006 A10=-3.42356e-007 A12= 1.27129e-008 Tenth surface K = 0.00000e+000 A 4= 9.90906e-004 A 6= 3.91752e-005 A 8= 1.59837e-006 A10=-2.31958e-009 A12=-1.36600e-009 Various data Focal length 13.94 F-number 2.85 Half field angle (°) 29.84 Image height 8.00 Overall lens length 39.68 BF 8.00 Single lens data Lens starting surface Focal length 1 1 -18.11 2 3 40.55 3 6 6.40 4 7 -7.91 5 9 -29.34 6 11 18.68 [Numerical example 4] Unit: mm Surface data Surface number r d nd νd Effective diameter 1 174.301 1.20 1.52841 76.46 9.02 2 7.436 5.00 7.58 3* 20.936 3.00 1.53160 55.84 9.35 4* -17.572 1.81 9.66 5 (Diaphragm) ∞ 1.53 9.49 6 10.065 4.73 1.81600 46.62 9.30 7 -13.587 1.33 1.70585 30.24 7.82 8 7.179 2.42 6.31 9* -7.166 1.16 1.63550 23.89 6.32 10* -9.575 1.06 7.50 11 40.577 4.20 1.53775 74.70 10.01 12 -9.716 (Variable) 11.29 Image plane ∞ Aspherical data The third surface K = 0.00000e+000 A4 = 4.92834e-005 A6 = -7.58139e-007 A8 = 9.66877e-009 A10 = 5.28887e-010 A12 = -3.82528e-011 The fourth surface K = 0.00000e+000 A4 = -2.87709e-005 A6 = -1.94063e-006 A8 = 1.07057e-008 A10 = 6.57759e-010 A12 = -3.75875e-011 The ninth surface K = 0.00000e+000 A4 = 1.26314e-004 A6 = -2.69131e-005 A8 = 9.33030e-007 A10 = 8.34209e-008 A12 = -5.77848e-009 The tenth surface K = 0.00000e+000 A4 = 4.86267e-004 A6 = -4.20015e-006 A8 = 8.70440e-007 A10 = -6.49799e-009 A12 = -5.42622e-011 Various data Focal length 13.61 F-number 2.04 Half field angle (°) 27.21 Image height 7.00 Overall lens length 38.54 BF 11.11 Single lens data Lens starting surface focal length 1 1 -14.74 2 3 18.47 3 6 7.79 4 7 -6.48 5 9 -55.09 6 11 15.02 [Numerical example 5] Unit: mm Surface data Surface number r d nd νd Effective diameter 1 99.659 1.15 1.49700 81.54 12.92 2 8.360 11.00 10.61 3* 21.148 3.00 1.58313 59.38 9.05 4* -19.042 2.43 9.15 5 (Aperture) ∞ 2.68 8.47 6 9.955 3.50 1.88300 40.76 7.68 7 -22.499 1.50 1.80518 25.42 6.41 8 7.650 2.27 5.22 9* -7.831 1.14 1.63550 23.89 6.26 10* -36.815 0.20 7.72 11 23.602 2.90 1.81554 44.36 8.96 12 -14.497 0.21 9.89 13 49.278 2.49 1.88300 40.76 10.53 14 -200.014 (Variable) 10.83 Image plane ∞ Aspherical data The third surface K = 0.00000e+000 A 4=-3.31939e-005 A 6= 1.00057e-007 A 8=-2.74914e-008 The fourth surface K = 0.00000e+000 A 4=-2.85162e-005 A 6= 1.59757e-007 A 8=-2.80716e-008 The ninth surface K = 0.00000e+000 A 4= 7.25303e-004 A 6=-1.24640e-005 A 8= 8.86812e-007 A10=-7.98689e-008 The tenth surface K = 0.00000e+000 A 4= 1.09100e-003 A 6=-9.24396e-006 A 8=-6.60088e-008 A10= 3.33401e-009 Various data Focal length 10.00 F-number 1.83 Half field angle (°) 30.96 Image height 6.00 Overall lens length 40.48 BF 6.00 Single lens data Lens starting surface Focal length 1 1 -18.44 2 3 17.67 3 6 8.23 4 7 -6.94 5 9 -15.89 6 11 11.40 7 13 44.99

[0054]

Table 1

[0055] [Imaging device] FIG. 13 shows an imaging device (digital still camera) using the stereo optical systems of Examples 1 to 5. In FIG. 13, ID is the camera body, and SO is an imaging optical system SO composed of any one of the stereo optical systems (right optical system OSR and left optical system OSL) of Examples 1 to 5. The imaging optical system SO may be detachable from the camera body ID or may be provided integrally. S is an imaging element such as a CCD sensor or a CMOS sensor that is built into the camera body ID and photoelectrically converts the optical image formed by the imaging optical system SO (i.e., captures the subject).

[0056] The imaging device may be a single-lens reflex camera having a quick-turn mirror or a mirrorless camera without a quick-turn mirror.

[0057] According to the imaging device using the stereo optical systems of Examples 1 to 5 as the imaging optical system, it is possible to obtain an imaging image that is bright and has a good three-dimensional effect while being small as a whole.

[0058] The above embodiments include the following configurations.

[0059] (Configuration 1) A stereo optical system having two optical systems arranged in parallel, each of the two optical systems is a coaxial optical system and has an aperture stop and at least two positive lenses arranged on the image side of the aperture stop, when the distance between the optical axes of the two optical systems is D, the focal length of each of the two optical systems is f, and the maximum angle of view of each of the two optical systems is ω, 1.8 ≦ D / (f·tanω) ≦ 5.5 A stereo optical system characterized by satisfying the above conditions. (Configuration 2) Each of the two optical systems has a front lens group on the object side of the aperture stop, when the focal length of the front lens group is fF, -1.0 ≦ f / fF ≦ 1.4 The stereo optical system according to Configuration 1, characterized by satisfying the condition. (Configuration 3) Each of the two optical systems has a rear lens group on the image side of the aperture stop, when the focal length of the rear lens group is fR, -0.9 ≦ fR / fF ≦ 2.4 The stereo optical system according to Configuration 1 or 2, characterized by satisfying the condition.

[0060] (Configuration 4) Each of the two optical systems has a rear lens group on the image side of the aperture stop, when the focal length of the first negative lens with the strongest refractive power among at least one negative lens included in the rear lens group is fRn1, -6.0 ≦ fR / fRn1 ≦ -1.4 The stereo optical system according to any one of Configurations 1 to 3, characterized by satisfying the condition. (Configuration 5) when the focal length of the second positive lens with the strongest refractive power among at least one positive lens arranged on the image side of the first negative lens in the rear lens group is fRp2, -3.2 ≦ fRp2 / fRn1 ≦ -1.0 The stereo optical system according to Configuration 4, characterized by satisfying the condition.

[0061] (Configuration 6) when the focal length of the first positive lens with the strongest refractive power among at least one positive lens arranged on the object side of the second positive lens in the rear lens group is fRp1, 0.4 ≦ fRp2 / fRp1 ≦ 4.5 The stereo optical system according to Configuration 5, characterized by satisfying the condition. (Configuration 7) Each of the two optical systems has a front lens group on the object side of the aperture stop, When the focal length of the most powerful negative lens among at least one negative lens included in the front lens group is fFn, and the focal length of the most powerful positive lens among at least one positive lens included in the front lens group is fFp, -2.0 ≦ fFn / fFp ≦ -0.1 The stereo optical system according to any one of Configurations 1 to 6, characterized by satisfying the condition. (Configuration 8) Each of the two optical systems has a rear lens group on the image side of the aperture stop, When the radius of curvature of the image-side surface of the first negative lens, which is the most powerful negative lens among at least one negative lens included in the rear lens group, is R1, and the radius of curvature of the object-side surface of the second negative lens, which is adjacent to the first negative lens with an air gap on the image side, is R2, -0.8 ≦ (R2 + R1) / (R2 - R1) ≦ 0.3 The stereo optical system according to any one of Configurations 1 to 7, characterized by satisfying the condition. (Configuration 9) When the refractive index of the material of the first positive lens at the d-line is ndRp1, 1.6 ≦ ndRp1 ≦ 2.2 The stereo optical system according to Configuration 6, characterized by satisfying the condition. (Configuration 10) When the distance on the optical axis from the most object-side surface of each of the two optical systems to the image plane is L, 2.0 ≦ L / f ≦ 5.5 The stereo optical system according to any one of Configurations 1 to 9, characterized by satisfying the condition.

[0062] (Configuration 11) When the back focus of each of the two optical systems is sk, 0.3 ≦ sk / f ≦ 0.9 The stereo optical system according to any one of Configurations 1 to 10, characterized by satisfying the condition. (Configuration 12) When the distance from the most object-side surface of each of the two optical systems to the entrance pupil position is t1, 0.2 ≦ t1 / f ≦ 1.3 The stereo optical system according to any one of Configurations 1 to 11, characterized by satisfying the condition. (Configuration 13) The stereo optical system according to any one of Configurations 1 to 12, characterized in that each of the two optical systems has six or more lenses. (Configuration 14) The stereo optical system according to any one of Configurations 1 to 13, characterized in that each of the two optical systems has a positive lens on the most image side. (Configuration 15) The stereo optical system according to any one of Configurations 1 to 14, characterized in that each of the two optical systems has a negative lens on the most object side. (Configuration 16) The stereo optical system according to any one of Configurations 1 to 15, characterized in that each of the two optical systems has at least one lens that moves during focusing. (Configuration 17) The stereo optical system according to any one of Configurations 1 to 16, characterized in that two optical images formed by the two optical systems are formed on a single image sensor. (Configuration 18) In each of the two optical systems, The front lens group on the object side of the aperture stop is composed of a negative lens and a positive lens arranged in order from the object side to the image side, The rear lens group on the image side of the aperture stop is composed of a cemented lens in which a first positive lens and a first negative lens are cemented, a second negative lens, and a second positive lens, arranged in order from the object side to the image side, and is characterized by the stereo optical system according to any one of Configurations 1 to 17. (Configuration 19) In each of the two optical systems, The front lens group on the object side of the aperture stop is composed of a negative lens, a positive lens, and a positive lens, which are arranged in order from the object side to the image side. The rear lens group on the image side of the aperture stop is composed of a cemented lens in which a first positive lens and a first negative lens are cemented, a second negative lens, and a second positive lens, which are arranged in order from the object side to the image side. The stereo optical system according to any one of Configurations 1 to 17, characterized in that. (Configuration 20) In each of the two optical systems, The front lens group on the object side of the aperture stop is composed of a negative lens and a positive lens, which are arranged in order from the object side to the image side. The rear lens group on the image side of the aperture stop is composed of a cemented lens in which a first positive lens and a first negative lens are cemented, a second negative lens, a second positive lens, and a third positive lens, which are arranged in order from the object side to the image side. The stereo optical system according to any one of Configurations 1 to 17, characterized in that. (Configuration 21) The stereo optical system according to any one of Configurations 1 to 20, An imaging device comprising an imaging element that images a subject through the stereo optical system.

[0063] 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

[0064] F Front lens group R Rear lens group Fn Negative lens Fp Positive lens Rp1 First positive lens Rn1 First negative lens Rn2 Second negative lens Rp2 Second positive lens SP Aperture stop IP Image plane

Claims

1. A stereo optical system having two optically systems arranged in parallel, wherein each of the two optical systems is a coaxial optical system and has a diaphragm and at least two positive lenses arranged on the image side of the diaphragm, when the distance between the optical axes of the two optical systems is D, the focal length of each of the two optical systems is f, and the maximum angle of view of each of the two optical systems is ω, 1.8 ≤ D / (f·tanω) ≤ 5.5 A stereo optical system characterized by satisfying the above condition.

2. Each of the two optical systems has a front lens group on the object side of the diaphragm, when the focal length of the front lens group is fF, -1.0 ≤ f / fF ≤ 1.4 The stereo optical system according to claim 1, characterized by satisfying the above condition.

3. Each of the two optical systems has a rear lens group on the image side of the diaphragm, when the focal length of the rear lens group is fR, -0.9 ≤ fR / fF ≤ 2.4 The stereo optical system according to claim 1, characterized by satisfying the above condition.

4. Each of the two optical systems has a rear lens group on the image side of the diaphragm, when the focal length of the first negative lens having the strongest refractive power among at least one negative lens included in the rear lens group is fRn1, -6.0 ≤ fR / fRn1 ≤ -1.4 The stereo optical system according to claim 1, characterized by satisfying the above condition.

5. When the focal length of the second positive lens having the strongest refractive power among at least one positive lens arranged on the image side of the first negative lens in the rear lens group is fRp2, -3.2 ≤ fRp2 / fRn1 ≤ -1.0 The stereo optical system according to claim 4, characterized by satisfying the above condition.

6. When the focal length of the first positive lens having the strongest refractive power among at least one positive lens arranged on the object side of the second positive lens in the rear lens group is fRp1, 0.4 ≤ fRp2 / fRp1 ≤ 4.5 The stereo optical system according to claim 5, characterized by satisfying the above condition.

7. Each of the two optical systems has a front lens group on the object side of the diaphragm, when the focal length of the negative lens having the strongest refractive power among at least one negative lens included in the front lens group is fFn, and the focal length of the positive lens having the strongest refractive power among at least one positive lens included in the front lens group is fFp, -2.0 ≤ fFn / fFp ≤ -0.1 The stereo optical system according to claim 1, characterized by satisfying the condition.

8. Each of the two optical systems has a rear lens group on the image side of the aperture stop, When the radius of curvature of the image-side surface of the first negative lens having the strongest refractive power among at least one negative lens included in the rear lens group is R1, and the radius of curvature of the object-side surface of the second negative lens adjacent to the first negative lens with an air interval on the image side with respect to the first negative lens is R2, -0.8 ≤ (R2 + R1) / (R2 - R1) ≤ 0.3 The stereo optical system according to claim 1, characterized by satisfying the condition.

9. When the refractive index of the material of the first positive lens at the d-line is ndRp1, 1.6 ≤ ndRp1 ≤ 2.2 The stereo optical system according to claim 6, characterized by satisfying the condition.

10. When the distance on the optical axis from the most object-side surface of each of the two optical systems to the image surface is L, 2.0 ≤ L / f ≤ 5.5 The stereo optical system according to claim 1, characterized by satisfying the condition.

11. When the back focus of each of the two optical systems is sk, 0.3 ≤ sk / f ≤ 0.9 The stereo optical system according to claim 1, characterized by satisfying the condition.

12. When the distance from the most object-side surface of each of the two optical systems to the entrance pupil position is t1, 0.2 ≤ t1 / f ≤ 1.3 The stereo optical system according to claim 1, characterized by satisfying the condition.

13. The stereo optical system according to claim 1, characterized in that each of the two optical systems has six or more lenses.

14. The stereo optical system according to claim 1, characterized in that each of the two optical systems has a positive lens on the most image side.

15. The stereo optical system according to claim 1, characterized in that each of the two optical systems has a negative lens on the most object side.

16. The stereo optical system according to claim 1, characterized in that each of the two optical systems has at least one lens that moves during focusing.

17. The stereo optical system according to claim 1, characterized in that two optical images formed by the two optical systems are formed on a single imaging device.

18. In each of the two optical systems, The front lens group on the object side with respect to the aperture stop is composed of a negative lens and a positive lens, which are arranged in order from the object side to the image side. The rear lens group on the image side with respect to the aperture stop is composed of a cemented lens in which a first positive lens and a first negative lens are cemented, a second negative lens, and a second positive lens, which are arranged in order from the object side to the image side. The stereo optical system according to claim 1, characterized in that.

19. In each of the two optical systems, The front lens group on the object side with respect to the aperture stop is composed of a negative lens, a positive lens, and a positive lens, which are arranged in order from the object side to the image side. The rear lens group on the image side with respect to the aperture stop is composed of a cemented lens in which a first positive lens and a first negative lens are cemented, a second negative lens, and a second positive lens, which are arranged in order from the object side to the image side. The stereo optical system according to claim 1, characterized in that.

20. In each of the two optical systems, The front lens group on the object side with respect to the aperture stop is composed of a negative lens and a positive lens, which are arranged in order from the object side to the image side. The rear lens group on the image side with respect to the aperture stop is composed of a cemented lens in which a first positive lens and a first negative lens are cemented, a second negative lens, a second positive lens, and a third positive lens, which are arranged in order from the object side to the image side. The stereo optical system according to claim 1, characterized in that.

21. A stereo optical system according to any one of claims 1 to 20, An imaging device, characterized by comprising an imaging element that images a subject through the stereo optical system.

Images