Optical system, optical device, and method for manufacturing optical system

Abstract

This optical system is configured so as to satisfy the conditional expression below, and comprises: a first optical system that has a front-side lens group, an optical path branching member having a branching surface for branching incident light, and a first rear-side lens group on which one branched light is incident; and a second optical system that has a front-side lens group, an optical path branching member, and a second rear-side lens group on which the other branched light is incident. The total optical length of the first optical system is equal to the total optical length of the second optical system, or greater than the total optical length of the second optical system.　0.50 < T(gr1) / (-f(gr1)) < 4.50, where T(gr1) is the distance on the optical axis from a lens surface closest to an object side of the front-side lens group to a lens surface closest to an image side of the front-side lens group, and f(gr1) is the composite focal length of the front-side lens group.

Description

Optical system, optical device, and method for manufacturing optical system

[0001] The present disclosure relates to optical systems, optical devices, and methods for manufacturing optical systems.

[0002] An optical system has been proposed that separates incident light into a first light and a second light and outputs the first light and the second light (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2006-324810

[0004] The optical system of the present disclosure includes a first optical system having, in order from the object side, a front lens group, an optical path branching member having a branching surface that transmits a portion of incident light and reflects at least another portion different from the incident light, and a first rear lens group onto which one of the transmitted light and the reflected light is incident, and a second optical system having, in order from the object side, the front lens group, the optical path branching member, and a second rear lens group onto which the other of the transmitted light and the reflected light is incident, and satisfies the following conditional expression: (18) 0.50 < T(gr1) / (-f(gr1)) < 4.50 where, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, f(gr1): the composite focal length of the front lens group.

[0005] The optical system of the present disclosure includes, in order from the object side, a first optical system having a front lens group, a prism having a splitting surface that transmits a portion of incident light and reflects at least a portion different from the incident light, and a first rear lens group onto which one of the transmitted light and the reflected light is incident, and a second optical system having, in order from the object side, the front lens group, the prism, and a second rear lens group onto which the other of the transmitted light and the reflected light is incident, wherein the total optical length of the first optical system is longer than the total optical length of the second optical system and both of the following conditional expressions are satisfied: Note that in the present disclosure, the total optical length is the distance on the optical axis from the lens surface closest to the object to the lens surface closest to the image plane plus the back focus in air equivalent length. (20) 1.10 < T(gr1) / f(fL) < 5.20 (21) 1.00 < T(pfL) / f(fL) < 11.50 Where, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, f(fL): the focal length of the first optical system or the focal length of the second optical system, whichever is longer, and T(pfL): the length on the optical axis of the prism in the optical system with the longer focal length of the first optical system or the second optical system.

[0006] The optical system of the present disclosure comprises, in order from the object side, a first optical system having a front lens group, a prism having a branching surface that transmits a portion of incident light and reflects at least another portion different from the incident light, and a first rear lens group into which one of the transmitted light and the reflected light is incident, and a second optical system having, in order from the object side, the front lens group, a prism, and a second rear lens group into which the other of the transmitted light and the reflected light is incident, wherein the total optical length of the first optical system is longer than the total optical length of the second optical system, and both of the following conditional expressions are satisfied: (22) 2.50 < T(gr1) / f(fS) < 9.50 (23) 3.00 < T(pfS) / f(fS) < 20.00 where, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, f(fS): the focal length of the first optical system or the focal length of the second optical system, whichever is shorter, and T(pfS): the length on the optical axis of the prism in the optical system with the shorter focal length of the first optical system or the second optical system.

[0007] The method for manufacturing an optical system disclosed herein includes, in order from the object side, a first optical system having a front lens group, an optical path branching member having a branching surface that transmits a portion of incident light and reflects at least another portion different from the incident light, and a first rear lens group into which one of the transmitted light and the reflected light is incident, and a second optical system having, in order from the object side, the front lens group, the optical path branching member, and a second rear lens group into which the other of the transmitted light and the reflected light is incident, wherein the total optical length of the first optical system is equal to or longer than the total optical length of the second optical system, and the lens groups and the optical path branching member are arranged so as to satisfy the following conditional expression: (18) 0.50 < T(gr1) / (-f(gr1)) < 4.50, where T(gr1) is the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, and f(gr1) is the composite focal length of the front lens group.

[0008] 1 is a schematic diagram illustrating a general configuration of an optical system of a first embodiment; a cross-sectional view of a first optical system included in the optical system of the first embodiment; a cross-sectional view of a second optical system included in the optical system of the first embodiment; a cross-sectional view of aberrations of the second optical system included in the optical system of the first embodiment; a cross-sectional view of a first optical system included in the optical system of the second embodiment; a cross-sectional view of aberrations of the first optical system included in the optical system of the second embodiment; a cross-sectional view of a second optical system included in the optical system of the second embodiment; a cross-sectional view of aberrations of the second optical system included in the optical system of the second embodiment; a cross-sectional view of a first optical system included in an optical system of a third embodiment; a cross-sectional view of aberrations of the first optical system included in the optical system of the third embodiment; a cross-sectional view of aberrations of the second optical system included in the optical system of the third embodiment; a cross-sectional view of aberrations of the second optical system included in the optical system of the third embodiment; a schematic diagram illustrating a general configuration of an optical system of a fourth embodiment; a cross-sectional view of a first optical system included in the optical system of the fourth embodiment; a cross-sectional view of aberrations of the ... the second optical system included in the optical system of the fourth embodiment. FIG. 10 is a diagram showing various aberrations of the second optical system included in the optical system of Example 4. FIG. 11 is a schematic diagram explaining the general configuration of the optical system of Example 5. FIG. 12 is a cross-sectional view of the first optical system included in the optical system of Example 5. FIG. 13 is a cross-sectional view of the second optical system included in the optical system of Example 5. FIG. 14 is a diagram showing various aberrations of the second optical system included in the optical system of Example 5. FIG. 15 is a schematic diagram of an optical device including the optical system of this embodiment. FIG. 16 is a flowchart showing an outline of a method for manufacturing the optical system of this embodiment.

[0009] An optical system, an optical device, and a method for manufacturing an optical system according to embodiments of the present application will be described below.

[0010] The optical system of this embodiment comprises a first optical system having, in order from the object side, a front lens group, an optical path branching member having a branching surface that transmits a portion of incident light and reflects at least another portion different from the incident light, and a first rear lens group onto which one of the transmitted light and the reflected light is incident, and a second optical system having, in order from the object side, the front lens group, the optical path branching member, and a second rear lens group onto which the other of the transmitted light and the reflected light is incident, and satisfies the following conditional expression: (18) 0.50 < T(gr1) / (-f(gr1)) < 4.50 where, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, f(gr1): the composite focal length of the front lens group.

[0011] In the optical system of this embodiment, the front lens group is used in the first optical system and the second optical system, thereby making it possible to reduce the size of the entire optical system.

[0012] Conditional expression (18) defines the ratio of the axial distance from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane to the composite focal length of the front lens group. By satisfying conditional expression (18), the optical system of this embodiment can suppress an increase in the overall optical length of the first optical system and the second optical system while suppressing an increase in the lens diameter of the lens closest to the object, and can appropriately correct various aberrations such as field curvature and distortion.

[0013] In the optical system of this embodiment, if the value of conditional expression (18) exceeds the upper limit, the lens diameter of the lens closest to the object side becomes too large, and it becomes difficult to correct various aberrations such as field curvature, astigmatism, and distortion.

[0014] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (18) to 4.50. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (18) to 3.80, 3.20, or even 2.60.

[0015] Furthermore, in the optical system of this embodiment, if the value of conditional expression (18) falls below the lower limit, the lens diameter of the lens closest to the object side becomes too large, and it becomes difficult to correct various aberrations such as field curvature and distortion.

[0016] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (18) to 0.50. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (18) to 0.70, 0.90, or even 1.00.

[0017] In the optical system of this embodiment, it is preferable to satisfy the following condition (19): 0.80<T(gr1) / (-f(gr1n))<4.60, where f(gr1n) is the composite focal length of the negative lenses in the front lens group that are located closest to the object and that are successively located on the image plane side.

[0018] Conditional expression (19) defines the ratio of the axial distance from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane to the composite focal length of the negative lenses in the front lens group that are consecutively arranged on the image plane side from the negative lens that is closest to the object side among the negative lenses in the front lens group. By satisfying conditional expression (19), the optical system of this embodiment can suppress an increase in the overall optical length of the first optical system while suppressing an increase in the lens diameter of the lens closest to the object, and can appropriately correct various aberrations such as field curvature and distortion.

[0019] In the optical system of this embodiment, if the value of conditional expression (19) exceeds the upper limit, the total optical length of the first optical system becomes too large, and correction of various aberrations such as field curvature and distortion becomes difficult.

[0020] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (19) to 4.60. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (19) to 3.80, 3.10, or even 2.40.

[0021] Furthermore, in the optical system of this embodiment, if the value of conditional expression (19) falls below the lower limit, the lens diameter of the lens closest to the object side becomes too large, and it becomes difficult to correct various aberrations such as field curvature and distortion.

[0022] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (19) to 0.80. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (19) to 0.95, 1.10, or even 1.20.

[0023] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression (26): 1.00<TL(L) / TL(S)<3.50 TL(L): total optical length of the first optical system TL(S): total optical length of the second optical system

[0024] Conditional expression (26) defines the ratio between the total optical length of the first optical system and the total optical length of the second optical system. By satisfying conditional expression (26), the optical system of this embodiment can appropriately correct various aberrations, such as spherical aberration and coma, while suppressing an increase in the total optical length of the first optical system.

[0025] In the optical system of this embodiment, if the value of conditional expression (26) exceeds the upper limit, the total optical length of the first optical system becomes too large, and correction of various aberrations such as spherical aberration and coma becomes difficult.

[0026] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (26) to 3.50. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (26) to 2.80, 2.20, or even 1.60.

[0027] The optical system of this embodiment comprises, in order from the object side, a first optical system having a front lens group, a prism having a branching surface that transmits a portion of incident light and reflects at least another portion different from the incident light, and a first rear lens group into which one of the transmitted light and the reflected light is incident, and a second optical system having, in order from the object side, the front lens group, a prism, and a second rear lens group into which the other of the transmitted light and the reflected light is incident, wherein the total optical length of the first optical system is longer than the total optical length of the second optical system, and both of the following conditional expressions are satisfied: (20) 1.10 < T(gr1) / f(fL) < 5.20 (21) 1.00 < T(pfL) / f(fL) < 11.50 Where, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, f(fL): the focal length of the first optical system or the focal length of the second optical system, whichever is longer, and T(pfL): the length on the optical axis of the prism in the optical system with the longer focal length of the first optical system or the second optical system.

[0028] In the optical system of this embodiment, the front lens group is used in the first optical system and the second optical system, thereby making it possible to reduce the size of the entire optical system.

[0029] Conditional expression (20) defines the ratio of the axial distance from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane to the focal length of the first optical system or the focal length of the second optical system, whichever is longer. By satisfying conditional expression (20), the optical system of this embodiment can suppress an increase in the lens diameter of the lens closest to the object, suppress an increase in the overall optical length of the first optical system or the second optical system, whichever has the longer focal length, and appropriately correct various aberrations such as field curvature and distortion.

[0030] In the optical system of this embodiment, if the value of conditional expression (20) exceeds the upper limit, the total optical length of the first optical system or the second optical system, whichever has the longer focal length, becomes too large, and it becomes difficult to correct various aberrations such as field curvature and distortion.

[0031] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (20) to 5.20. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (20) to 4.70, 4.20, or even 3.80.

[0032] Furthermore, in the optical system of this embodiment, if the value of conditional expression (20) falls below the lower limit, the lens diameter of the lens closest to the object side becomes too large, and it becomes difficult to correct various aberrations such as field curvature and distortion.

[0033] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (20) to 1.10. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (20) to 1.50, 1.80, or even 2.10.

[0034] Conditional expression (21) defines the ratio of the length on the optical axis of the prism in the optical system having the longer focal length of either the first optical system or the second optical system to the focal length of the longer of the first optical system or the second optical system. By satisfying conditional expression (21), the optical system of this embodiment can suppress an increase in the lens diameter of the lens closest to the object, suppress an increase in the overall optical length of either the first optical system or the second optical system having the longer focal length, and appropriately correct various aberrations such as field curvature and distortion.

[0035] In the optical system of this embodiment, if the value of conditional expression (21) exceeds the upper limit, the total optical length of the first optical system or the second optical system, whichever has the longer focal length, becomes too large, and it becomes difficult to correct various aberrations such as field curvature and distortion.

[0036] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (21) to 11.50. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (21) to 8.80, 7.10, or even 6.50.

[0037] Furthermore, in the optical system of this embodiment, if the value of conditional expression (21) falls below the lower limit, it becomes difficult to correct various aberrations such as curvature of field and distortion.

[0038] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (21) to 1.00. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (21) to 1.40, 1.80, or even 2.20.

[0039] The optical system of this embodiment comprises, in order from the object side, a first optical system having a front lens group, a prism having a branching surface that transmits a portion of incident light and reflects at least another portion different from the incident light, and a first rear lens group into which one of the transmitted light and the reflected light is incident, and a second optical system having, in order from the object side, the front lens group, a prism, and a second rear lens group into which the other of the transmitted light and the reflected light is incident, wherein the total optical length of the first optical system is longer than the total optical length of the second optical system, and both of the following conditional expressions are satisfied: (22) 2.50 < T(gr1) / f(fS) < 9.50 (23) 3.00 < T(pfS) / f(fS) < 20.00 where, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, f(fS): the focal length of the first optical system or the focal length of the second optical system, whichever is shorter, and T(pfS): the length on the optical axis of the prism in the optical system with the shorter focal length of the first optical system or the second optical system.

[0040] In the optical system of this embodiment, the front lens group is used in the first optical system and the second optical system, thereby making it possible to reduce the size of the entire optical system.

[0041] Conditional expression (22) defines the ratio of the axial distance from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane to the focal length of the first optical system or the focal length of the second optical system, whichever is shorter. By satisfying conditional expression (22), the optical system of this embodiment can suppress an increase in the overall optical length of the first optical system or the second optical system, whichever has the shorter focal length, and can appropriately correct various aberrations such as field curvature and distortion.

[0042] In the optical system of this embodiment, if the value of conditional expression (22) exceeds the upper limit, the total optical length of the first optical system or the second optical system, whichever has the shorter focal length, becomes too large, and it becomes difficult to correct various aberrations such as field curvature and distortion.

[0043] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (22) to 9.50. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (22) to 8.60, 7.70, or even 6.80.

[0044] Furthermore, in the optical system of this embodiment, if the value of conditional expression (22) falls below the lower limit, the lens diameter of the lens closest to the object side becomes too large, and it becomes difficult to correct various aberrations such as field curvature and distortion.

[0045] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (22) to 2.50. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (22) to 3.00, 3.50, or even 3.90.

[0046] Conditional expression (23) defines the ratio of the length on the optical axis of the prism in the optical system having the shorter focal length of either the first optical system or the second optical system to the focal length of the shorter of the first optical system and the second optical system. By satisfying conditional expression (23), the optical system of this embodiment can suppress an increase in the overall optical length of either the first optical system or the second optical system having the shorter focal length, and can appropriately correct various aberrations such as field curvature and distortion.

[0047] In the optical system of this embodiment, if the value of conditional expression (23) exceeds the upper limit, the total optical length of the first optical system or the second optical system, whichever has the shorter focal length, becomes too large, and it becomes difficult to correct various aberrations such as field curvature and distortion.

[0048] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (23) to 20.00. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (23) to 19.00, 18.00, or even 17.00.

[0049] Furthermore, in the optical system of this embodiment, if the value of conditional expression (23) falls below the lower limit, it becomes difficult to correct various aberrations such as curvature of field and distortion.

[0050] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (23) to 3.00. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (23) to 3.40, 3.80, or even 4.20.

[0051] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression (2): 1.10<T(pL) / T(pS)<5.50, where T(pL) is the length of the prism in the first optical system on the optical axis, and T(pS) is the length of the prism in the second optical system on the optical axis.

[0052] Conditional expression (2) defines the ratio between the axial length of the prism in the first optical system and the axial length of the prism in the second optical system. By satisfying conditional expression (2), the optical system of this embodiment can appropriately correct various aberrations such as spherical aberration and coma, and ensure sufficient peripheral illumination.

[0053] In the optical system of this embodiment, if the value of conditional expression (2) exceeds the upper limit, it becomes difficult to correct various aberrations such as spherical aberration and coma.

[0054] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (2) to 5.50. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (2) to 4.70, 3.80, or even 3.00.

[0055] Furthermore, in the optical system of this embodiment, if the value of conditional expression (2) is below the lower limit, it becomes difficult to correct various aberrations such as spherical aberration and coma. Also, the peripheral light flux of the first optical system is limited, resulting in a decrease in the amount of peripheral illumination.

[0056] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (2) to 1.10. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (2) to 1.60, 2.10, or even 2.60.

[0057] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression (12): 1.20<T(pS) / f(S)<6.40, where T(pS) is the length of the prism in the second optical system on the optical axis, and f(S) is the focal length of the second optical system.

[0058] Conditional expression (12) defines the ratio between the axial length of the prism in the second optical system and the focal length of the second optical system. By satisfying conditional expression (12), the optical system of this embodiment can appropriately correct various aberrations, such as spherical aberration, coma, and field curvature, in the second optical system while suppressing an increase in the overall optical length.

[0059] In the optical system of this embodiment, if the value of conditional expression (12) is below the upper limit, the total optical length of the second optical system becomes too large, and it becomes difficult to correct various aberrations such as spherical aberration, coma, and field curvature.

[0060] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (12) to 6.40. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (12) to 5.70, 5.00, or even 4.40.

[0061] In the optical system of this embodiment, if the value of conditional expression (12) is below the lower limit, it becomes difficult to correct various aberrations such as spherical aberration, coma, and curvature of field in the second optical system.

[0062] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (12) to 1.20. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (12) to 1.50, 1.80, or even 2.20.

[0063] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression (13): 2.40<T(pL) / f(L)<20.50, where T(pL) is the length of the prism in the first optical system on the optical axis, and f(L) is the focal length of the first optical system.

[0064] Conditional expression (13) defines the ratio between the axial length of the prism in the first optical system and the focal length of the second optical system. By satisfying conditional expression (13), the optical system of this embodiment can appropriately correct various aberrations, such as spherical aberration, coma, and curvature of field, in the first optical system, while suppressing an increase in the overall optical length.

[0065] In the optical system of this embodiment, if the value of conditional expression (13) is below the upper limit, the total optical length of the first optical system becomes too large, and it becomes difficult to correct various aberrations such as spherical aberration, coma, and field curvature.

[0066] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (13) to 20.50. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (13) to 19.00, 17.50, or even 16.50.

[0067] In the optical system of this embodiment, if the value of conditional expression (13) falls below the lower limit, it becomes difficult to correct various aberrations such as spherical aberration, coma, and curvature of field in the first optical system.

[0068] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (13) to 2.40. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (13) to 3.20, 4.00, or even 4.80.

[0069] In the optical system of this embodiment, the prism preferably has a total reflection surface that totally reflects at least the light on the optical axis among the light that has passed through the front lens group and then been reflected by the splitting surface.

[0070] In the optical system of this embodiment, by providing a total reflection surface, the angle of incidence of incident light on the branching surface can be reduced, thereby reducing the difficulty of manufacturing a branching surface with the specified performance.

[0071] In the optical system of this embodiment, it is preferable to satisfy the following condition (14): 1.40<T(gr1) / f(S)<6.90, where T(gr1) is the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, and f(S) is the focal length of the second optical system.

[0072] Conditional expression (14) defines the ratio of the axial distance from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane to the focal length of the second optical system. By satisfying conditional expression (14), the optical system of this embodiment can appropriately correct various aberrations, such as spherical aberration, coma, and curvature of field, in the second optical system while suppressing an increase in the overall optical length.

[0073] In the optical system of this embodiment, if the value of conditional expression (14) is below the upper limit, the total optical length of the second optical system becomes too large, and it becomes difficult to correct various aberrations such as spherical aberration, coma, and field curvature.

[0074] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (14) to 6.90. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (14) to 6.30, 5.70, or even 5.10.

[0075] In the optical system of this embodiment, if the value of conditional expression (14) falls below the lower limit, it becomes difficult to correct various aberrations such as spherical aberration, coma, and curvature of field in the second optical system.

[0076] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (14) to 1.40. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (14) to 1.90, 2.40, or even 2.80.

[0077] In the optical system of this embodiment, it is preferable to satisfy the following condition (15): 1.00<T(gr1) / f(L)<9.80, where T(gr1) is the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, and f(L) is the focal length of the first optical system.

[0078] Conditional expression (15) defines the ratio of the axial distance from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane to the focal length of the first optical system. By satisfying conditional expression (15), the optical system of this embodiment can appropriately correct various aberrations, such as spherical aberration, coma, and curvature of field, in the first optical system, while suppressing an increase in the overall optical length.

[0079] In the optical system of this embodiment, if the value of conditional expression (15) is below the upper limit, the total optical length of the first optical system becomes too large, and it becomes difficult to correct various aberrations such as spherical aberration, coma, and field curvature.

[0080] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (15) to 9.80. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (15) to 8.80, 7.80, or even 6.80.

[0081] In the optical system of this embodiment, if the value of conditional expression (15) falls below the lower limit, it becomes difficult to correct various aberrations such as spherical aberration, coma, and curvature of field in the first optical system.

[0082] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (15) to 1.00. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (15) to 1.40, 1.80, or even 2.10.

[0083] In the optical system of this embodiment, it is preferable to satisfy the following condition: (1) 0.80<-f(gr1n) / f(L)<4.30, where f(gr1n) is the composite focal length of the negative lenses in the front lens group that are positioned closest to the object and then consecutively to the negative lenses positioned closest to the image plane, and f(L) is the focal length of the first optical system.

[0084] Conditional expression (1) defines the ratio between the focal length of the first optical system and the composite focal length of the negative lenses in the front lens group, which are arranged consecutively from the negative lens arranged closest to the object side to the negative lens arranged closest to the image plane side. By satisfying conditional expression (1), the optical system of this embodiment can appropriately correct various aberrations such as field curvature, astigmatism, and distortion while suppressing an increase in the lens diameter of the lens arranged closest to the object side.

[0085] In the optical system of this embodiment, if the value of conditional expression (1) exceeds the upper limit, the lens diameter of the lens closest to the object side becomes too large, and it becomes difficult to correct various aberrations such as field curvature, astigmatism, and distortion.

[0086] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (1) to 4.30. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (1) to 3.80, 3.35, or even 2.90.

[0087] Furthermore, in the optical system of this embodiment, if the value of conditional expression (1) is below the lower limit, the total optical length of the second optical system becomes too long, and it becomes difficult to correct various aberrations such as spherical aberration and coma. Furthermore, the peripheral light flux of the first optical system is limited, and the amount of peripheral illumination decreases.

[0088] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (1) to 0.80. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (1) to 1.10, 1.40, or even 1.70.

[0089] In addition, in the optical system of this embodiment, it is preferable to satisfy the following conditional expression (3): 0.50<-f(gr1n) / f(S)<4.40, where f(S) is the focal length of the second optical system.

[0090] Conditional expression (3) defines the ratio between the composite focal length of the negative lenses in the front lens group, which are located closest to the object, and the negative lenses located consecutively on the image plane side, and the focal length of the second optical system. By satisfying conditional expression (3), the optical system of this embodiment can appropriately correct various aberrations, such as curvature of field, astigmatism, and distortion, while suppressing an increase in the lens diameter of the lens located closest to the object.

[0091] In the optical system of this embodiment, if the value of conditional expression (3) exceeds the upper limit, the lens diameter of the lens closest to the object side becomes too large, and it becomes difficult to correct various aberrations such as field curvature, astigmatism, and distortion.

[0092] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (3) to 4.40. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (3) to 4.00, 3.70, or even 3.40.

[0093] Furthermore, in the optical system of this embodiment, if the value of conditional expression (3) falls below the lower limit, it becomes difficult to correct various aberrations such as curvature of field, astigmatism, and distortion.

[0094] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (3) to 0.50. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.80, 1.15, or even 1.50.

[0095] In the optical system of this embodiment, it is preferable that the second rear lens group has an aperture stop and satisfies the following condition (6): 0.50<f(gr2S) / (-f(gr1))<3.40, where f(gr2S) is the composite focal length of the lenses in the second rear lens group that are closer to the image plane than the aperture stop, and f(gr1) is the composite focal length of the front lens group.

[0096] Conditional expression (6) defines the ratio of the composite focal length of the lens in the second rear lens group that is closer to the image plane than the aperture stop to the composite focal length of the front lens group. By satisfying conditional expression (6), the optical system of this embodiment can suppress an increase in the lens diameter of the lens closest to the object, suppress an increase in the overall optical length of the second optical system, and appropriately correct various aberrations such as field curvature, coma, and distortion.

[0097] In the optical system of this embodiment, if the value of conditional expression (6) exceeds the upper limit, the refractive power of the lens on the image plane side of the aperture stop in the second optical system will be weak, causing the total optical length to become too long and making it difficult to correct various aberrations such as field curvature, coma, and distortion.

[0098] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (6) to 3.40. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (6) to 3.10, 2.80, or even 2.50.

[0099] Furthermore, in the optical system of this embodiment, if the value of conditional expression (6) falls below the lower limit, the refractive power of the front lens group will be weak, the lens diameter of the lens closest to the object will become too large, and it will become difficult to correct various aberrations such as field curvature and distortion in the second optical system.

[0100] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (6) to 0.50. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (6) to 0.65, 0.80, or even 0.95.

[0101] In the optical system of this embodiment, it is preferable that the first rear lens group has an aperture stop and satisfies the following condition (7): 0.40<f(gr2L) / (-f(gr1))<4.20, where f(gr2L) is the composite focal length of the lenses in the first rear lens group that are closer to the image plane than the aperture stop, and f(gr1) is the composite focal length of the front lens group.

[0102] Conditional expression (7) defines the ratio of the composite focal length of the lens in the first rear lens group that is closer to the image plane than the aperture stop to the composite focal length of the front lens group. By satisfying conditional expression (7), the optical system of this embodiment can suppress an increase in the lens diameter of the lens closest to the object, suppress an increase in the overall optical length of the first optical system, and appropriately correct various aberrations such as field curvature, coma, and distortion.

[0103] In the optical system of this embodiment, if the value of conditional expression (7) exceeds the upper limit, the refractive power of the lens on the image plane side of the aperture stop in the first optical system will be weak, causing the total optical length to become too long and making it difficult to correct various aberrations such as field curvature, coma, and distortion.

[0104] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (7) to 4.20. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (7) to 3.80, 3.50, or even 3.20.

[0105] Furthermore, in the optical system of this embodiment, if the value of conditional expression (7) falls below the lower limit, the refractive power of the front lens group becomes weak, the lens diameter of the lens closest to the object becomes too large, and it becomes difficult to correct various aberrations such as field curvature and distortion in the first optical system.

[0106] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (7) to 0.40. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (7) to 0.75, 1.10, or even 1.45.

[0107] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression (8): 0.70<f(lS) / (-f(gr1n))<5.90, where f(lS) is the focal length of the lens in the second rear lens group that is closest to the image plane.

[0108] Conditional expression (8) defines the ratio between the focal length of the lens closest to the image surface in the second rear lens group and the composite focal length of the negative lenses in the front lens group that are arranged consecutively toward the image surface from the negative lens that is arranged closest to the object. By satisfying conditional expression (8), the optical system of this embodiment can suppress an increase in the lens diameter of the lens closest to the object, suppress an increase in the overall optical length of the second optical system, and appropriately correct various aberrations such as field curvature, coma, and distortion.

[0109] In the optical system of this embodiment, if the value of conditional expression (8) is below the upper limit, the refractive power of the lens closest to the image plane in the second optical system will be weak, the total optical length will become too long, and it will become difficult to correct various aberrations such as field curvature, coma, and distortion.

[0110] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (8) to 5.90. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (8) to 5.30, 4.80, or even 4.20.

[0111] In the optical system of this embodiment, if the value of conditional expression (8) falls below the lower limit, the refractive power of the front lens group becomes weak, the lens diameter of the lens closest to the object becomes too large, and it becomes difficult to correct various aberrations such as field curvature and distortion in the second optical system.

[0112] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (8) to 0.70. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (8) to 1.00, 1.35, or even 1.70.

[0113] In the optical system of this embodiment, it is preferable to satisfy the following condition (9): 1.50<f(lL) / (-f(gr1n))<7.70, where f(lL) is the focal length of the lens in the first rear lens group that is closest to the image plane.

[0114] Conditional expression (9) defines the ratio between the focal length of the lens closest to the image surface in the first rear lens group and the composite focal length of the negative lenses in the front lens group that are consecutively arranged on the image surface side from the negative lens closest to the object side. By satisfying conditional expression (9), the optical system of this embodiment can suppress an increase in the lens diameter of the lens closest to the object side, suppress an increase in the overall optical length of the first optical system, and appropriately correct various aberrations such as field curvature, coma, and distortion.

[0115] In the optical system of this embodiment, if the value of conditional expression (9) is below the upper limit, the refractive power of the lens closest to the image plane in the first optical system will be weak, making the total optical length too long and making it difficult to correct various aberrations such as field curvature, coma, and distortion.

[0116] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (9) to 7.70. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (9) to 6.30, 5.00, or even 3.90.

[0117] In the optical system of this embodiment, if the value of conditional expression (9) falls below the lower limit, the refractive power of the front lens group becomes weak, the lens diameter of the lens closest to the object becomes too large, and it becomes difficult to correct various aberrations such as field curvature and distortion in the first optical system.

[0118] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (9) to 1.50. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (9) to 1.70, 1.90, or even 2.10.

[0119] In the optical system of this embodiment, it is preferable that the second rear lens group has an aperture stop and satisfies the following condition (10): 1.60<f(gr2S) / f(S)<5.60, where f(gr2S) is the composite focal length of the lenses in the second rear lens group that are closer to the image plane than the aperture stop, and f(S) is the focal length of the second optical system.

[0120] Conditional expression (10) defines the ratio between the composite focal length of the lenses in the second rear lens group that are closer to the image plane than the aperture stop, and the focal length of the second optical system. By satisfying conditional expression (10), the optical system of this embodiment can suppress an increase in the overall optical length of the second optical system and can appropriately correct various aberrations, such as spherical aberration, coma, and curvature of field.

[0121] In the optical system of this embodiment, if the value of conditional expression (10) is below the upper limit, the refractive power of the lens on the image plane side of the aperture stop in the second optical system will be weak, causing the total optical length to become too long and making it difficult to correct various aberrations such as spherical aberration, coma, and field curvature.

[0122] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (10) to 5.60. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (10) to 5.00, 4.50, or even 3.90.

[0123] In the optical system of this embodiment, if the value of conditional expression (10) falls below the lower limit, the refractive power of the lens in the second optical system that is closer to the image plane than the aperture stop becomes strong, making it difficult to correct various aberrations such as spherical aberration, coma, and field curvature in the second optical system.

[0124] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (10) to 1.60. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (10) to 2.00, 2.40, or even 2.80.

[0125] In the optical system of this embodiment, it is preferable that the first rear lens group has an aperture stop and satisfies the following condition (11): 2.30<f(gr2L) / f(L)<8.80, where f(gr2L) is the composite focal length of the lenses in the first rear lens group that are closer to the image plane than the aperture stop, and f(L) is the focal length of the first optical system.

[0126] Conditional expression (11) defines the ratio between the composite focal length of the lenses in the first rear lens group that are closer to the image plane than the aperture stop, and the focal length of the first optical system. By satisfying conditional expression (11), the optical system of this embodiment can suppress an increase in the overall optical length of the first optical system and can appropriately correct various aberrations, such as spherical aberration, coma, and curvature of field.

[0127] In the optical system of this embodiment, if the value of conditional expression (11) is below the upper limit, the refractive power of the lens on the image plane side of the aperture stop in the first optical system will be weak, causing the total optical length to become too long and making it difficult to correct various aberrations such as spherical aberration, coma, and field curvature.

[0128] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (11) to 8.80. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (11) to 8.00, 7.20, or even 6.40.

[0129] In the optical system of this embodiment, if the value of conditional expression (11) falls below the lower limit, the refractive power of the lens on the image plane side of the aperture stop in the first optical system becomes strong, making it difficult to correct various aberrations such as spherical aberration, coma, and field curvature in the second optical system.

[0130] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (11) to 2.30. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (11) to 3.00, 3.70, or even 4.30.

[0131] In the optical system of this embodiment, it is preferable to satisfy the following condition (17): 0.23<f(lS) / f(lL)<1.50, where f(lS) is the focal length of the lens in the second rear lens group that is closest to the image surface, and f(lL) is the focal length of the lens in the first rear lens group that is closest to the image surface.

[0132] Conditional expression (17) defines the ratio between the focal length of the lens in the second rear lens group closest to the image plane and the focal length of the lens in the first rear lens group closest to the image plane. By satisfying conditional expression (17), the optical system of this embodiment can reduce the deviation of the imaging positions on the image plane for a given angle of view in the first optical system and the second optical system.

[0133] In the optical system of this embodiment, if the value of conditional expression (17) falls below the upper limit, it becomes difficult to correct the distortion of the first optical system and the distortion of the second optical system so that they approach each other, and the deviation of the imaging position on the image plane for a given angle of view in each optical system becomes large.

[0134] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (17) to 1.50. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (17) to 1.40, 1.30, or even 1.20.

[0135] In the optical system of this embodiment, if the value of conditional expression (17) falls below the lower limit, it becomes difficult to correct the distortions of the first optical system and the second optical system so that they approach each other, and the deviation of the imaging positions on the image plane for a given angle of view in each optical system becomes large.

[0136] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (17) to 0.23. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (17) to 0.36, 0.49, or even 0.62.

[0137] In the optical system of this embodiment, it is preferable to satisfy the following condition (5): 0.01<-f(gr1n) / f(gr1p)<0.21, where f(gr1p) is the composite focal length of the positive lenses in the front lens group that are arranged closest to the object and are successively arranged on the image plane side.

[0138] Conditional expression (5) defines the ratio between the composite focal length of the negative lenses arranged consecutively from the negative lens arranged closest to the object among the negative lenses in the front lens group toward the image plane side, and the composite focal length of the positive lenses arranged consecutively from the positive lens arranged closest to the object among the positive lenses in the front lens group toward the image plane side. By satisfying conditional expression (5), the optical system of this embodiment can suppress an increase in the lens diameter of the lens closest to the object, appropriately correct various aberrations such as field curvature and distortion, and reduce the difficulty of manufacturing a split surface having predetermined performance.

[0139] In the optical system of this embodiment, if the value of conditional expression (5) exceeds the upper limit, the angle of incidence on the splitting surface becomes too large, making it difficult to manufacture a splitting surface having the desired performance.

[0140] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (5) to 0.21. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (5) to 0.18, 0.15, or even 0.12.

[0141] Furthermore, in the optical system of this embodiment, if the value of conditional expression (5) falls below the lower limit, the refractive power of the front lens group will be weak, the lens diameter of the lens closest to the object will become too large, and it will become difficult to correct various aberrations such as field curvature and distortion.

[0142] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (5) to 0.01. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (5) to 0.02, 0.03, or even 0.04.

[0143] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression (16): 1.50<Nave(s)<1.90, where Nave(s) is the average refractive index for the s-line of the negative lenses included in the front lens group.

[0144] Conditional expression (16) defines the average refractive index for the s-line of the negative lenses included in the front lens group. By satisfying conditional expression (16), the optical system of this embodiment can appropriately correct various aberrations, such as distortion and curvature of field.

[0145] In the optical system of this embodiment, if the value of conditional expression (16) falls below the upper limit, the refractive power of the negative lens included in the front lens group for the s-line becomes too strong, making it difficult to correct various aberrations such as distortion and field curvature.

[0146] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (16) to 1.90. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (16) to 1.84, 1.77, or even 1.70.

[0147] In the optical system of this embodiment, if the value of conditional expression (16) falls below the lower limit, the refractive power of the negative lens included in the front lens group for the s-line becomes too weak, making it difficult to correct various aberrations such as distortion and field curvature.

[0148] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (16) to 1.50. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (16) to 1.55, 1.57, 1.58, or even 1.60.

[0149] In the optical system of this embodiment, it is preferable that the front lens group has negative refractive power.

[0150] In the optical system of this embodiment, by having such a configuration, it is possible to suppress an increase in the lens diameter of the lens closest to the object side.

[0151] In the optical system of this embodiment, it is preferable that the front lens group has at least one positive lens and at least one negative lens.

[0152] With this configuration, the optical system of this embodiment can appropriately correct various aberrations such as field curvature and astigmatism.

[0153] In the optical system of this embodiment, it is preferable that each of the first optical system and the second optical system has a positive lens closest to the image plane.

[0154] With the optical system of this embodiment having such a configuration, various aberrations such as distortion, curvature of field, astigmatism, and coma can be corrected well.

[0155] In the optical system of this embodiment, it is preferable that both of the following conditional expressions are satisfied: (24) 80.0°<2ωL (25) 80.0°<2ωS where, 2ωL: total angle of view of the first optical system, and 2ωS: total angle of view of the second optical system.

[0156] Conditional expression (24) defines the full angle of view of the first optical system. By satisfying conditional expression (24), the optical system of this embodiment can obtain an image representing a wider range with the first optical system.

[0157] In the optical system of this embodiment, if the value of conditional expression (24) falls below the lower limit, it is not possible to obtain an image representing a wide range with the first optical system.

[0158] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (24) to 80.0°. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (24) to 84.00°, 87.00°, or even 90.00°.

[0159] Conditional expression (25) defines the full angle of view of the second optical system. By satisfying conditional expression (25), the optical system of this embodiment can obtain an image representing a wider range with the second optical system.

[0160] In the optical system of this embodiment, if the value of conditional expression (25) falls below the lower limit, it is not possible to obtain an image representing a wide range by the second optical system.

[0161] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (25) to 80.0°. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (25) to 84.00°, 87.00°, or even 90.00°.

[0162] In the optical system of this embodiment, it is preferable that one of the transmitted light and the reflected light is visible light and the other is near-infrared light, and that, of the first optical system and the second optical system, the optical system that uses visible light on the image plane side from the branching surface has a cemented lens, and the optical system that uses near-infrared light on the image plane side from the branching surface consists of only a single lens.

[0163] In the optical system of this embodiment, the optical system using visible light on the image plane side from the splitting surface has a cemented lens, so that chromatic aberration can be appropriately corrected. Also, in the optical system of this embodiment, the optical system using near-infrared light on the image plane side from the splitting surface is configured with only a single lens, so that the optical system can be made compact.

[0164] With the above configuration, it is possible to realize an optical system that appropriately forms an image from the light transmitted by the splitting surface and the light reflected by the splitting surface out of the incident light.

[0165] The optical device of this embodiment has the optical system configured as described above, which makes it possible to realize an optical device that can appropriately form images of the light transmitted through the splitting surface and the light reflected by the splitting surface out of the incident light, and can perform processing using each image.

[0166] The manufacturing method of the optical system disclosed herein is a manufacturing method of an optical system including: a first optical system having, in order from the object side, a front lens group, an optical path branching member having a branching surface that transmits a portion of incident light and reflects at least another portion different from the incident light, and a first rear lens group into which one of the transmitted light and the reflected light is incident; and a second optical system having, in order from the object side, the front lens group, the optical path branching member, and a second rear lens group into which the other of the transmitted light and the reflected light is incident, wherein the total optical length of the first optical system is equal to or longer than the total optical length of the second optical system, and each lens group and the optical path branching member are arranged so as to satisfy the following conditional expression: (18) 0.50 < T(gr1) / (-f(gr1)) < 4.50, where T(gr1) is the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, and f(gr1) is the composite focal length of the front lens group.

[0167] The method for manufacturing an optical system disclosed herein is a method for manufacturing an optical system including: a first optical system having, in order from the object side, a front lens group, a prism having a branching surface that transmits a portion of incident light and reflects at least a portion different from the incident light, and a first rear lens group into which one of the transmitted light and the reflected light is incident; and a second optical system having, in order from the object side, the front lens group, a prism, and a second rear lens group into which the other of the transmitted light and the reflected light is incident, wherein the total optical length of the first optical system is longer than the total optical length of the second optical system, and the lens groups and prisms are arranged so as to satisfy both of the following conditional expressions: (20) 1.10 < T(gr1) / f(fL) < 5.20 (21) 1.00 < T(pfL) / f(fL) < 11.50 Where, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, f(fL): the focal length of the first optical system or the focal length of the second optical system, whichever is longer, and T(pfL): the length on the optical axis of the prism in the optical system with the longer focal length of the first optical system or the second optical system.

[0168] The method for manufacturing an optical system disclosed herein is a method for manufacturing an optical system including: a first optical system having, in order from the object side, a front lens group, a prism having a branching surface that transmits a portion of incident light and reflects at least a portion different from the incident light, and a first rear lens group into which one of the transmitted light and the reflected light is incident; and a second optical system having, in order from the object side, the front lens group, a prism, and a second rear lens group into which the other of the transmitted light and the reflected light is incident, wherein the total optical length of the first optical system is longer than the total optical length of the second optical system, and the lens groups and prisms are arranged so as to satisfy both of the following conditional expressions: (22) 2.50 < T(gr1) / f(fS) < 9.50 (23) 3.00 < T(pfS) / f(fS) < 20.00 where, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, f(fS): the focal length of the first optical system or the focal length of the second optical system, whichever is shorter, and T(pfS): the length on the optical axis of the prism in the optical system with the shorter focal length of the first optical system or the second optical system.

[0169] By using such a method for manufacturing an optical system, it is possible to manufacture an optical system that appropriately forms an image from each of the light transmitted through the splitting surface and the light reflected by the splitting surface out of the incident light.

[0170] Numerical Examples Hereinafter, examples of the present invention will be described with reference to the drawings.

[0171] First Example FIG. 1 is a schematic diagram illustrating the general configuration of an optical system according to a first example.

[0172] The optical system 1 of this embodiment includes a first optical system OS1 including, in order from the object side, a front lens group GR1, an optical path branching member OB having a branching surface BF, and a first rear lens group GR2L onto which light incident on the front lens group GR1 and the optical path branching member OB and transmitted by the branching surface BF is incident. The optical system 1 of this embodiment also includes a second optical system OS2 including, in order from the object side, the front lens group GR1, the optical path branching member OB, and a second rear lens group GR2S onto which light incident on the front lens group GR1 and the optical path branching member OB and reflected by the branching surface BF is incident. The total optical length of the first optical system OS1 is longer than the total optical length of the second optical system OS2.

[0173] In FIG. 1, the first optical axis X1 of the first optical system OS1 and the second optical axis X2 of the second optical system OS2 are depicted so as not to overlap with each other on the object side of the splitting surface BF for the sake of explanation.

[0174] In the optical system 1 of this embodiment, the optical path branching member OB is a dichroic prism having a branching surface BF that transmits visible light and reflects near-infrared light. Visible light includes, for example, the d-line (wavelength 587.6 nm) or the g-line (wavelength 435.8 nm), and near-infrared light includes, for example, the s-line (wavelength 852.1 nm).

[0175] The first optical system OS1 of this embodiment images, on an image plane I1, light (near-infrared light) that is emitted from the front lens group GR1 and reflected by the splitting surface BF and the total internal reflection surface TRF of the optical path splitting member OB. The second optical system OS2 of this embodiment images, on an image plane I2, light (visible light) that is emitted from the front lens group GR1 and transmitted by the splitting surface BF of the optical path splitting member OB.

[0176] The optical system 1 of this embodiment can appropriately image the light reflected by the branching surface BF and the light transmitted by the branching surface BF, respectively, using the first optical system OS1 and the second optical system OS2.

[0177] FIG. 2 is a cross-sectional view of the first optical system OS1 included in the optical system 1 of the first embodiment.

[0178] The first optical system OS1 of this embodiment has, in order from the object side, a meniscus-shaped negative lens L1 with a convex surface facing the object side, a biconcave negative lens L2, a meniscus-shaped positive lens L3 with a concave surface facing the object side, an optical path branching member OB, a biconvex positive lens L11, an aperture stop ST1, a meniscus-shaped positive lens L12 with a convex surface facing the object side, a meniscus-shaped negative lens L13 with a concave surface facing the object side, and a biconvex positive lens L14.

[0179] An image pickup element made up of a CCD, CMOS or the like is disposed on the image plane I1.

[0180] A filter FL1 is disposed between the image surface I1 and the positive lens L14, which is disposed closest to the image surface I1.

[0181] In the first optical system OS1 of this embodiment, the negative lens L1, the negative lens L2, and the positive lens L3 are included in a front lens group GR1, and the positive lens L11, the aperture stop ST1, the positive lens L12, the negative lens L13, and the positive lens L14 are included in a first rear lens group GR2L.

[0182] Table 1-1 below lists the values ​​of the specifications of the first optical system OS1 of this embodiment. In the [Lens specifications] of Table 1-1, m is the order of the optical surface counted from the object side, r is the radius of curvature, d is the surface spacing, n(d) is the refractive index for the d-line, n(s) is the refractive index for the s-line, and νd is the Abbe number for the d-line. A radius of curvature of r=∞ indicates a flat surface. Also, in the [Lens specifications], an optical surface marked with an "*" is an aspherical surface.

[0183] In [Aspherical Data], m indicates the optical surface corresponding to the aspherical data, K indicates the conic constant, and A4 to A10 indicate the aspherical coefficients.

[0184] The aspherical surface is expressed by the following formula (a), where y is the height in the direction perpendicular to the optical axis, S(y) is the distance (amount of sag) along the optical axis from the tangent plane of the vertex of each aspherical surface at height y to each aspherical surface, r is the radius of curvature (paraxial radius of curvature) of the reference spherical surface, K is the conic constant, and An is the n-th order aspherical coefficient. In each example, the second order aspherical coefficient A2 is 0. Also, "En" is expressed as "×10 -n " indicates.

[0185] (a) S(y) = (y 2 / r) / 1 + (1-K×y 2 / r 2 ) 1 / 2 + A4×y 4 + A6×y 6 + A8×y 8 + A10×y 10

[0186] In the [Overall Specifications] of Table 1-1, Fno is the F-number of the optical system, f is the focal length of the entire optical system, TL is the total optical length, Y is the image height, and 2ω is the total angle of view (degrees). Note that these values ​​listed in [Overall Specifications] are values ​​for the d-line.

[0187] The focal length f, radius of curvature r, and other length values ​​listed in Table 1-1 are in mm. However, this is not limited to this, as the same optical performance can be obtained even when the optical system is proportionally enlarged or reduced.

[0188] The symbols in Table 1-1 described above are also used in the second optical system OS2 of this embodiment and in tables of other embodiments, which will be described later.

[0189] (Table 1-1) [Lens specifications] m r d n(d) νd ns 1) 23.24716 2.500 1.618 63.34 1.610 2) 8.85754 6.000 3) -62.73425 1.300 1.618 63.34 1.610 4) 10.07820 2.940 5) -62.37902 5.500 1.755 27.57 1.735 6) -30.02650 0.800 7) ∞ 32.500 1.517 63.88 1.510 (Optical path branching member OB) 8) ∞ 0.230 9) 15.44687 2.850 1.835 42.73 1.819 10) -300.00000 1.400 11> ∞ 1.650 (Aperture stop ST1) 12) 10.79653 2.850 1.835 42.73 1.819 13) 350.00000 0.920 14) -15.64213 0.500 1.835 42.73 1.819 15) -83.64620 1.190 *16) 300.00000 4.150 1.835 42.73 1.819 *17) -25.21347 3.490 18) ∞ 0.210 1.517 63.88 1.510 (Filter FL1) 19) ∞ 0.343 [Aspherical data] m K A4 A6 A8 A10 16) 9.2225 7.80E-05 2.38E-06 1.06E-06 -3.67E-08 17) -2.9888 4.80E-04 -1.15E-05 3.76E-06 -1.49E-07 [Overall specifications] Fno 1.18 f 2.81 TL 71.25 Y 2.29 2ω 92.00

[0190] FIG. 3 is a diagram showing various aberrations of the first optical system OS1 included in the optical system 1 of the first embodiment.

[0191] In each aberration diagram, the spherical aberration diagram (LONGITUDINAL SPHERICAL ABERRATION) shows the ratio to the maximum aperture, the astigmatism diagram (ASTIGMATIC FIELD CURVES) and distortion diagram (DISTORTION) show values ​​for half the angle of view, and the coma diagram shows the ratio to the maximum image height. Each aberration diagram shows values ​​for the s-line. In the astigmatism diagrams, S indicates the sagittal image plane, and T indicates the meridional image plane. The same symbols as those used in the aberration diagrams of this embodiment are used in the aberration diagrams of other embodiments described below.

[0192] From each aberration diagram, it can be seen that the first optical system OS1 of this embodiment appropriately corrects various aberrations and has high optical performance for the s-line.

[0193] FIG. 4 is a cross-sectional view of the second optical system OS2 included in the optical system 1 of the first embodiment.

[0194] The second optical system OS2 of this embodiment has, in order from the object side, a meniscus negative lens L1 with a convex surface facing the object side, a biconcave negative lens L2, a meniscus positive lens L3 with a concave surface facing the object side, an optical path branching member OB, a meniscus positive lens L21 with a convex surface facing the object side, an aperture stop ST2, a meniscus positive lens L22 with a convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L23 and a biconcave negative lens L24, a meniscus positive lens L25 with a convex surface facing the object side, and a meniscus positive lens L26 with a convex surface facing the object side.

[0195] An image pickup element made up of a CCD, CMOS or the like is disposed on the image plane I2.

[0196] A filter FL2 is disposed between the positive lens L26, which is disposed closest to the image plane I2, and the image plane I2.

[0197] In the second optical system OS2 of this embodiment, the negative lens L1, the negative lens L2, and the positive lens L3 are included in the front lens group GR1, and the positive lens L21, the aperture stop ST2, the positive lens L22, the cemented negative lens formed by the positive lens L23 and the negative lens L24, the positive lens L25, and the positive lens L26 are included in the second rear lens group GR2S.

[0198] Table 1-2 below lists the specifications of the second optical system OS2 of this embodiment.

[0199] (Table 1-2) [Lens specifications] m r d n(d) νd 1) 23.24716 2.500 1.618 63.34 2) 8.85754 6.000 3) -62.73425 1.300 1.618 63.34 4) 10.07820 2.940 5) -62.37902 5.500 1.755 27.57 6) -30.02650 0.800 7) ∞ 11.000 1.517 63.88 (Optical path branching member OB) 8) ∞ 0.150 9) 18.88785 5.650 1.700 48.10 10) 300.00000 1.540 11> ∞ 1.550 (Aperture stop ST2) 12) 14.36704 2.600 1.697 55.52 13) 313.89814 0.150 14) 15.11805 2.200 1.519 69.89 15) -25.38622 0.400 1.755 27.57 16) 9.06631 0.930 17) 9.42227 2.400 1.623 58.12 18) 42.81721 1.830 *19) 11.33584 4.500 1.623 58.12 *20) 23.57318 4.660 21) ∞ 0.500 1.517 63.88 (Filter FL2) 22) ∞ 0.359 [Aspheric data] m K A4 A6 A8 A10 19) -1.1497 -7.48E-05 -1.27E-06 -8.15E-08 7.15E-10 20) -4.4220 8.96E-05 -2.30E-06 -3.03E-08 3.23E-10 [Overall specifications] Fno 2.00 f 4.99 TL 59.29 Y 4.01 2ω 92.00

[0200] 5A to 5C are diagrams showing various aberrations of the second optical system OS2 included in the optical system 1 of Example 1. Each aberration diagram shows values ​​for the d-line and the g-line.

[0201] From each aberration diagram, it can be seen that the second optical system OS2 of this embodiment appropriately corrects various aberrations and has high optical performance for the d-line and g-line.

[0202] Second Example The optical system 1 of this example has the same general configuration as the optical system 1 of the first example described with reference to FIG.

[0203] In the optical system 1 of this embodiment, the optical path branching member OB is a dichroic prism having a branching surface BF that transmits near-infrared light and reflects visible light.

[0204] The first optical system OS1 of this embodiment images, on an image plane I1, light (visible light) that is emitted from the front lens group GR1 and reflected by the splitting surface BF and the total internal reflection surface TRF of the optical path splitting member OB. The second optical system OS2 of this embodiment images, on an image plane I2, light (near-infrared light) that is emitted from the front lens group GR1 and transmitted by the splitting surface BF of the optical path splitting member OB.

[0205] The optical system 1 of this embodiment can appropriately image the light reflected by the branching surface BF and the light transmitted by the branching surface BF, respectively, using the first optical system OS1 and the second optical system OS2.

[0206] FIG. 6 is a cross-sectional view of the first optical system OS1 included in the optical system 1 of the second embodiment.

[0207] The first optical system OS1 of this embodiment has, in order from the object side, a meniscus negative lens L1 with a convex surface facing the object side, a biconcave negative lens L2, a meniscus positive lens L3 with a convex surface facing the object side, an optical path branching member OB, a meniscus positive lens L11 with a convex surface facing the object side, an aperture stop ST1, a meniscus negative lens L12 with a convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L13 and a biconcave negative lens L14, a meniscus positive lens L15 with a convex surface facing the object side, and a meniscus positive lens L16 with a convex surface facing the object side.

[0208] An image pickup element made up of a CCD, CMOS or the like is disposed on the image plane I1.

[0209] A filter FL1 is disposed between the image plane I1 and the positive lens L16, which is disposed closest to the image plane I1.

[0210] In the first optical system OS1 of this embodiment, the negative lens L1, the negative lens L2, and the positive lens L3 are included in a front lens group GR1, and the positive lens L11, the aperture stop ST1, the negative lens L12, the cemented negative lens formed by the negative lens L13 and the positive lens L14, the positive lens L15, and the positive lens L16 are included in a first rear lens group GR2L.

[0211] Table 2-1 below lists the specifications of the first optical system OS1 of this embodiment.

[0212] (Table 2-1) [Lens specifications] m r d n(d) νd 1) 29.68900 1.200 1.640 60.19 2) 9.70090 5.000 3) -195.75730 1.200 1.618 63.34 4) 11.92140 1.550 5) 28.18830 2.000 1.755 27.57 6) 43.38750 1.000 7) ∞ 32.500 1.517 63.88 (Optical path branching member OB) 8) ∞ 0.500 9) 12.82210 2.620 1.700 48.10 10) 302.64820 3.760 11> ∞ 0.100 (Aperture stop ST1) 12) 30.12150 0.955 1.651 56.24 13) 26.67870 0.100 14) 10.81720 2.710 1.519 69.89 15) -14.47040 0.350 1.755 27.57 16) 16.24750 0.100 17) 9.11660 1.150 1.620 60.24 18) 10.15080 1.039 *19) 14.74820 5.500 1.620 60.24 *20) 270.84350 1.000 21) ∞ 0.300 1.517 63.88 (Filter FL1) 22) ∞ 7.217 [Aspheric data] m K A4 A6 A8 A10 19) -3.2435 -2.20E-04 -3.59E-06 3.52E-09 2.17E-10 20) 11.0000 -4.40E-05 -1.45E-06 4.57E-08 -2.20E-10 [Overall specifications] Fno 2.10 f 5.03 TL 71.75 Y 4.02 2ω 92.00

[0213] 7A and 7B are diagrams showing various aberrations of the first optical system OS1 included in the optical system 1 of Example 2. Each aberration diagram shows values ​​for the d-line and the g-line.

[0214] From each aberration diagram, it can be seen that the first optical system OS1 of this embodiment appropriately corrects various aberrations and has high optical performance for the d-line and g-line.

[0215] FIG. 8 is a cross-sectional view of the second optical system OS2 included in the optical system 1 of the second embodiment.

[0216] The second optical system OS2 of this embodiment has, in order from the object side, a meniscus-shaped negative lens L1 with a convex surface facing the object side, a biconcave negative lens L2, a meniscus-shaped positive lens L3 with a convex surface facing the object side, an optical path branching member OB, a meniscus-shaped negative lens L21 with a convex surface facing the object side, an aperture stop ST2, a biconvex positive lens L22, a meniscus-shaped positive lens L23 with a convex surface facing the object side, and a biconvex positive lens L24.

[0217] An image pickup element made up of a CCD, CMOS or the like is disposed on the image plane I2.

[0218] In the second optical system OS2 of this embodiment, the negative lens L1, the negative lens L2, and the positive lens L3 are included in the front lens group GR1, and the negative lens L21, the aperture stop ST2, the positive lens L22, the positive lens L23, and the positive lens L24 are included in the second rear lens group GR2S.

[0219] Table 2-2 below lists the values ​​of the specifications of the second optical system OS2 of this embodiment.

[0220] (Table 2-2) [Lens specifications] m r d n(d) νd ns 1) 29.68897 1.200 1.640 60.20 1.631 2) 9.70092 5.000 3) -195.75734 1.200 1.618 63.34 1.610 4) 11.92145 1.550 5) 28.18828 2.000 1.755 27.57 1.735 6) 43.38751 1.000 7) ∞ 12.000 1.517 63.88 1.510 (Optical path branching member OB) 8) ∞ 0.500 9) 16.64118 0.350 1.532 48.78 1.523 10) 9.69527 11.748 11> ∞ 0.100 (Aperture stop ST2) 12) 16.58651 3.000 1.755 27.57 1.735 13) -531.70077 4.273 14) 10.44070 5.497 1.755 27.57 1.735 15) 14.92879 0.647 *16) 13.31421 5.500 1.774 47.18 1.760 17) -128.00260 4.854 [Aspherical data] m K A4 A6 A8 A10 16) -4.0120 -1.07E-04 -5.73E-06 1.74E-08 6.04E-10 [Overall specifications] Fno 1.20 f 2.77 TL 60.42 Y 2.20 2ω 92.00

[0221] 9A to 9C are diagrams showing various aberrations of the second optical system OS2 included in the optical system 1 of Example 2. Each aberration diagram shows values ​​for the s-line.

[0222] From each aberration diagram, it can be seen that the second optical system OS2 of this embodiment appropriately corrects various aberrations and has high optical performance for the s-line.

[0223] Third Embodiment The optical system 1 of this embodiment has the same general configuration as the optical system 1 of the first embodiment described with reference to FIG.

[0224] In the optical system 1 of this embodiment, the optical path branching member OB is a dichroic prism having a branching surface BF that transmits visible light and reflects near-infrared light.

[0225] The first optical system OS1 of this embodiment images, on an image plane I1, light (near-infrared light) that is emitted from the front lens group GR1 and reflected by the splitting surface BF and the total internal reflection surface TRF of the optical path splitting member OB. The second optical system OS2 of this embodiment images, on an image plane I2, light (visible light) that is emitted from the front lens group GR1 and transmitted by the splitting surface BF of the optical path splitting member OB.

[0226] The optical system 1 of this embodiment can appropriately image the light reflected by the branching surface BF and the light transmitted by the branching surface BF, respectively, using the first optical system OS1 and the second optical system OS2.

[0227] FIG. 10 is a cross-sectional view of the first optical system OS1 included in the optical system 1 of the third embodiment.

[0228] The first optical system OS1 of this embodiment has, in order from the object side, a meniscus-shaped negative lens L1 with a convex surface facing the object side, a biconcave negative lens L2, a meniscus-shaped positive lens L3 with a concave surface facing the object side, an optical path branching member OB, a biconvex positive lens L11, an aperture stop ST1, a meniscus-shaped positive lens L12 with a convex surface facing the object side, a meniscus-shaped positive lens L13 with a convex surface facing the object side, a meniscus-shaped positive lens L14 with a convex surface facing the object side, and a meniscus-shaped positive lens L15 with a concave surface facing the object side.

[0229] An image pickup element made up of a CCD, CMOS or the like is disposed on the image plane I1.

[0230] A filter FL1 is disposed between the image plane I1 and the positive lens L15, which is disposed closest to the image plane I1.

[0231] In the first optical system OS1 of this embodiment, the negative lens L1, the negative lens L2, and the positive lens L3 are included in a front lens group GR1, and the positive lens L11, the aperture stop ST1, the positive lens L12, the positive lens L13, the positive lens L14, and the positive lens L15 are included in a first rear lens group GR2L.

[0232] Table 3-1 below lists the values ​​of the specifications of the first optical system OS1 of this embodiment.

[0233] (Table 3-1) [Lens specifications] m r d n(d) νd ns 1) 22.65975 2.000 1.603 60.69 1.595 2) 8.58484 6.013 3) -46.67377 0.800 1.519 69.89 1.512 4) 10.08192 3.049 5) -69.22039 2.313 1.755 27.57 1.735 6) -40.41329 0.988 7) ∞ 47.000 1.517 63.88 1.510 (Optical path branching member OB) 8) ∞ 1.805 9) 33.91430 3.017 1.720 50.27 1.708 10) -66.06093 0.100 11) ∞ 0.100 (Aperture stop ST1) 12) 26.49772 2.147 1.623 58.12 1.614 13) 74.01188 0.100 14) 19.60218 2.271 1.593 67.90 1.586 15) 46.09410 0.100 16) 13.36196 2.584 1.487 70.31 1.481 17) 29.13116 4.967 *18) -19.16636 5.496 1.487 70.31 1.481 *19) -9.49217 0.182 20) ∞ 0.300 1.517 63.88 1.510 (Filter FL1) 21) ∞ 3.000 [Aspheric data] m K A4 A6 A8 A10 18) -2.2395 -3.29E-04 3.25E-06 1.17E-07 -4.08E-09 19) 0.3196 -1.85E-05 1.28E-05 -1.34E-07 -8.44E-09 [Overall specifications] Fno 1.20 f 2.93 TL 88.00 Y 2.29 2ω 92.00

[0234] 11A to 11C are diagrams showing various aberrations of the first optical system OS1 included in the optical system 1 of Example 3. Each aberration diagram shows values ​​for the s-line.

[0235] From each aberration diagram, it can be seen that the first optical system OS1 of this embodiment appropriately corrects various aberrations and has high optical performance for the s-line.

[0236] FIG. 12 is a cross-sectional view of the second optical system OS2 included in the optical system 1 of the third embodiment.

[0237] The second optical system OS2 of this embodiment has, in order from the object side, a meniscus negative lens L1 with a convex surface facing the object side, a biconcave negative lens L2, a meniscus positive lens L3 with a concave surface facing the object side, an optical path branching member OB, a meniscus positive lens L21 with a convex surface facing the object side, an aperture stop ST2, a meniscus positive lens L22 with a convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L23 and a biconcave negative lens L24, a meniscus positive lens L25 with a convex surface facing the object side, and a meniscus positive lens L26 with a convex surface facing the object side.

[0238] An image pickup element made up of a CCD, CMOS or the like is disposed on the image plane I2.

[0239] A filter FL2 is disposed between the positive lens L26, which is disposed closest to the image plane I2, and the image plane I2.

[0240] In the second optical system OS2 of this embodiment, the negative lens L1, the negative lens L2, and the positive lens L3 are included in the front lens group GR1, and the positive lens L21, the aperture stop ST2, the positive lens L22, the cemented negative lens formed by the positive lens L23 and the negative lens L24, the positive lens L25, and the positive lens L26 are included in the second rear lens group GR2S.

[0241] Table 3-2 below lists the specifications of the second optical system OS2 of this embodiment.

[0242] (Table 3-2) [Lens specifications] m r d n(d) νd 1) 22.65975 2.000 1.603 60.69 2) 8.58484 6.013 3) -46.67377 0.800 1.519 69.89 4) 10.08192 3.049 5) -69.22039 2.313 1.755 27.57 6) -40.41329 0.988 7) ∞ 17.000 1.517 63.88 (Optical path branching member OB) 8) ∞ 0.384 9) 15.15381 2.574 1.720 50.27 10) 516.88017 4.098 11> ∞ 0.100 (Aperture stop ST2) 12) 15.83971 2.165 1.651 56.24 13) 42.97328 0.100 14) 12.34848 2.119 1.519 69.89 15) -21.04824 0.350 1.755 27.57 16) 10.90829 0.100 17) 9.48441 2.289 1.620 60.24 18) 23.82029 1.297 *19) 12.79368 5.503 1.620 60.24 *20) 25.72131 1.000 21) ∞ 0.300 1.517 63.88 (Filter FL2) 22) ∞ 3.960 [Aspheric data] m K A4 A6 A8 A10 19) -2.0024 -1.76E-04 -2.50E-06 -1.86E-08 3.06E-10 20) 11.0000 8.87E-05 -1.45E-06 1.92E-08 4.13E-09 [Overall specifications] Fno 2.00 f 4.93 TL 58.40 Y 4.01 2ω 92.00

[0243] 13A and 13B are diagrams showing various aberrations of the second optical system OS2 included in the optical system 1 of Example 3. Each aberration diagram shows values ​​for the d-line and the g-line.

[0244] From each aberration diagram, it can be seen that the second optical system OS2 of this embodiment appropriately corrects various aberrations and has high optical performance for the d-line and g-line.

[0245] Fourth Example FIG. 14 is a schematic diagram illustrating the general configuration of an optical system according to a fourth example.

[0246] The optical system 1 of this embodiment includes a first optical system OS1 including, in order from the object side, a front lens group GR1, an optical path branching member OB having a branching surface BF, and a first rear lens group GR2L onto which light incident on the front lens group GR1 and the optical path branching member OB and transmitted by the branching surface BF is incident. The optical system 1 of this embodiment also includes a second optical system OS2 including, in order from the object side, the front lens group GR1, the optical path branching member OB, and a second rear lens group GR2S onto which light incident on the front lens group GR1 and the optical path branching member OB and reflected by the branching surface BF is incident. The total optical length of the first optical system OS1 is longer than the total optical length of the second optical system OS2.

[0247] In FIG. 14, for the sake of explanation, the first optical axis X1 of the first optical system OS1 and the second optical axis X2 of the second optical system OS2 are drawn so as not to overlap with each other on the object side of the splitting surface BF.

[0248] In the optical system 1 of this embodiment, the optical path branching member OB is a dichroic prism having a branching surface BF that transmits near-infrared light and reflects visible light.

[0249] The first optical system OS1 of this embodiment images, on an image plane I1, light (near-infrared light) that is emitted from the front lens group GR1 and transmitted by the splitting surface BF and the total internal reflection surface TRF of the optical path splitting member OB. The second optical system OS2 of this embodiment images, on an image plane I2, light (visible light) that is emitted from the front lens group GR1 and reflected by the splitting surface BF of the optical path splitting member OB.

[0250] The optical system 1 of this embodiment can appropriately image the light transmitted by the branching surface BF and the light reflected by the branching surface BF, respectively, using the first optical system OS1 and the second optical system OS2.

[0251] FIG. 15 is a cross-sectional view of the first optical system OS1 included in the optical system 1 of the fourth embodiment.

[0252] The first optical system OS1 of this embodiment has, in order from the object side, a meniscus-shaped negative lens L1 with its convex surface facing the object side, a biconcave negative lens L2, a meniscus-shaped positive lens L3 with its convex surface facing the object side, an optical path branching member OB, a biconvex positive lens L11, an aperture stop ST1, a biconvex positive lens L12, a meniscus-shaped positive lens L13 with its convex surface facing the object side, and a biconvex positive lens L14.

[0253] An image pickup element made up of a CCD, CMOS or the like is disposed on the image plane I1.

[0254] A filter FL1 is disposed between the image surface I1 and the positive lens L14, which is disposed closest to the image surface I1.

[0255] In the first optical system OS1 of this embodiment, the negative lens L1, the negative lens L2, and the positive lens L3 are included in a front lens group GR1, and the positive lens L11, the aperture stop ST1, the positive lens L12, the positive lens L13, and the positive lens L14 are included in a first rear lens group GR2L.

[0256] Table 4-1 below lists the values ​​of the specifications of the first optical system OS1 of this embodiment.

[0257] (Table 4-1) [Lens specifications] m r d n(d) νd ns 1) 31.56470 1.190 1.640 60.20 1.631 2) 8.14860 5.800 3) -75.53150 1.190 1.618 63.34 1.610 4) 9.75210 1.550 5) 23.57220 5.500 1.755 27.57 1.735 6) 23.35310 1.000 7) ∞ 11.000 1.517 63.88 1.510 (Optical path branching member OB) 8) ∞ 0.870 9) 505.32550 5.500 1.487 70.31 1.481 10) -42.66070 8.800 11) ∞ 0.000 (Aperture stop ST1) 12) 21.15710 3.000 1.755 27.57 1.735 13) -193.50380 0.400 14) 9.59100 4.950 1.755 27.57 1.735 15) 13.32120 2.000 *16) 10.35130 5.500 1.541 46.97 1.531 *17) -58.16010 0.550 18) ∞ 0.300 1.517 63.88 1.510 (Filter FL1) 19) ∞ 2.715 [Aspherical data] m K A4 A6 A8 A10 16) -7.0241 3.20E-04 -2.94E-05 5.31E-07 -2.57E-09 17) -9.0000 -1.88E-04 -1.08E-06 8.31E-07 -5.15E-09 [Overall specifications] Fno 1.24 f 2.81 TL 61.71 Y 2.29 2ω 92.00

[0258] 16 is a diagram showing various aberrations of the first optical system OS1 included in the optical system 1 of Example 4. Each aberration diagram shows values ​​for the s-line.

[0259] From each aberration diagram, it can be seen that the first optical system OS1 of this embodiment appropriately corrects various aberrations and has high optical performance for the s-line.

[0260] FIG. 17 is a cross-sectional view of the second optical system OS2 included in the optical system 1 of the fourth example.

[0261] The second optical system OS2 of this embodiment has, in order from the object side, a meniscus negative lens L1 with a convex surface facing the object side, a biconcave negative lens L2, a meniscus positive lens L3 with a convex surface facing the object side, an optical path branching member OB, a biconvex positive lens L21, an aperture stop ST2, a meniscus positive lens L22 with a convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L7 and a biconcave negative lens L8, a meniscus positive lens L25 with a convex surface facing the object side, and a meniscus positive lens L26 with a convex surface facing the object side.

[0262] An image pickup element made up of a CCD, CMOS or the like is disposed on the image plane I2.

[0263] A filter FL2 is disposed between the positive lens L26, which is disposed closest to the image plane I2, and the image plane I2.

[0264] In the second optical system OS2 of this embodiment, the negative lens L1, the negative lens L2, and the positive lens L3 are included in the front lens group GR1, and the positive lens L21, the aperture stop ST2, the positive lens L22, the cemented negative lens formed by the positive lens L23 and the negative lens L24, the positive lens L25, and the positive lens L26 are included in the second rear lens group GR2S.

[0265] Table 4-2 below lists the specifications of the second optical system OS2 of this embodiment.

[0266] (Table 4-2) [Lens specifications] m r d n(d) νd 1) 31.56470 1.190 1.640 60.19 2) 8.14860 5.800 3) -75.53150 1.190 1.618 63.34 4) 9.75210 1.550 5) 23.57220 5.500 1.755 27.57 6) 23.35310 1.000 7) ∞ 11.000 1.517 63.88 (Optical path branching member OB) 8) ∞ 0.770 9) 20.16450 3.000 1.700 48.10 10) -37.07530 6.760 11> ∞ 0.100 (Aperture stop ST2) 12) 9.12160 1.650 1.651 56.24 13) 23.81970 1.050 14) 14.35620 2.100 1.519 69.89 15) -22.90500 0.350 1.755 27.57 16) 7.95000 0.100 17) 7.86080 1.510 1.620 60.24 18) 12.41850 0.710 *19) 9.06350 5.500 1.620 60.24 *20) 256.56200 1.000 21) ∞ 0.300 1.517 63.88 (Filter FL2) 22) ∞ 4.275 [Aspheric data] m K A4 A6 A8 A10 19) -1.2102 -1.11E-04 -3.56E-06 -1.97E-07 1.67E-09 20) -9.0000 5.03E-05 -4.33E-06 -2.03E-08 3.18E-10 [Overall specifications] Fno 1.91 f 4.02 TL 56.30 Y 3.96 2ω 116.00

[0267] 18A and 18B are diagrams showing various aberrations of the second optical system OS2 included in the optical system 1 of Example 4. Each aberration diagram shows values ​​for the d-line and the g-line.

[0268] From each aberration diagram, it can be seen that the second optical system OS2 of this embodiment appropriately corrects various aberrations and has high optical performance for the d-line and g-line.

[0269] Fifth Example FIG. 19 is a schematic diagram illustrating the general configuration of an optical system according to a fifth example.

[0270] The optical system 1 of this embodiment includes a first optical system OS1 including, in order from the object side, a front lens group GR1, an optical path branching member OB having a branching surface BF, and a first rear lens group GR2L onto which light incident on the front lens group GR1 and the optical path branching member OB and reflected by the branching surface BF is incident. The optical system 1 of this embodiment also includes a second optical system OS2 including, in order from the object side, the front lens group GR1, the optical path branching member OB, and a second rear lens group GR2S onto which light incident on the front lens group GR1 and the optical path branching member OB and transmitted by the branching surface BF is incident. The total optical length of the first optical system OS1 is longer than the total optical length of the second optical system OS2.

[0271] In FIG. 19, the first optical axis X1 of the first optical system OS1 and the second optical axis X2 of the second optical system OS2 are drawn so as not to overlap with each other on the object side of the splitting surface BF for the sake of explanation.

[0272] In the optical system 1 of this embodiment, the optical path branching member OB is a dichroic mirror having a branching surface BF that transmits near-infrared light and reflects visible light.

[0273] The first optical system OS1 of this embodiment images, on an image plane I1, light (visible light) that is emitted from the front lens group GR1 and reflected by the splitting surface BF and the total internal reflection surface TRF of the optical path splitting member OB. The second optical system OS2 of this embodiment images, on an image plane I2, light (near-infrared light) that is emitted from the front lens group GR1 and transmitted by the splitting surface BF of the optical path splitting member OB.

[0274] The optical system 1 of this embodiment can appropriately image the light reflected by the branching surface BF and the light transmitted by the branching surface BF, respectively, using the first optical system OS1 and the second optical system OS2.

[0275] FIG. 20 is a cross-sectional view of the first optical system OS1 included in the optical system 1 of the fifth embodiment.

[0276] The first optical system OS1 of this embodiment has, in order from the object side, a meniscus negative lens L1 with a convex surface facing the object side, a meniscus negative lens L2 with a convex surface facing the object side, a meniscus negative lens L3 with a concave surface facing the object side, a biconvex positive lens L11, an aperture stop ST1, a meniscus positive lens L12 with a convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L13 and a biconcave negative lens L14, a meniscus positive lens L15 with a convex surface facing the object side, and a biconvex positive lens L16.

[0277] An image pickup element made up of a CCD, CMOS or the like is disposed on the image plane I1.

[0278] A filter FL1 is disposed between the image plane I1 and the positive lens L16, which is disposed closest to the image plane I1.

[0279] In the first optical system OS1 of this embodiment, the negative lens L1, negative lens L2, and negative lens L3 are included in a front lens group GR1, and the positive lens L11, aperture stop ST1, positive lens L12, a cemented negative lens formed by a positive lens L13 and a negative lens L14, positive lens L15, and positive lens L16 are included in a first rear lens group GR2L.

[0280] Table 5-1 below lists the values ​​of the specifications of the first optical system OS1 of this embodiment.

[0281] (Table 5-1) [Lens specifications] m r d n(d) νd 1) 29.39415 1.200 1.700 48.10 2) 7.87468 3.100 3) 31.19550 1.200 1.487 70.32 4) 8.16096 4.050 5) -10.84631 4.650 1.744 44.80 6) -13.43511 7.000 7) ∞ 7.300 (Branch plane BF) 8) 15.01135 3.000 1.700 48.10 9) -73.65866 4.550 10> ∞ 0.100 (Aperture stop ST1) 11) 23.57922 1.000 1.487 70.32 12) 23.57922 1.480 13) 18.35557 2.600 1.487 70.32 14) -9.05030 1.000 1.795 28.69 15) 22.40141 0.100 16) 13.35807 3.730 1.487 70.32 17) 149.95808 1.000 *18) 15.09709 5.500 1.497 81.56 *19) -26.56453 3.000 20) ∞ 0.300 1.517 63.88 (Filter FL1) 21) ∞ 4.789 [Aspherical data] m K A4 A6 A8 A10 18) 1.7852 -3.47E-04 -3.83E-06 8.53E-08 -1.80E-09 19) 1.7594 -1.61E-04 -1.61E-06 4.22E-09 5.09E-10 [Overall specifications] Fno 2.05 f 5.10 TL 60.55 Y 4.00 2ω 92.00

[0282] 21 is a diagram showing various aberrations of the first optical system OS1 included in the optical system 1 of Example 5. Each aberration diagram shows values ​​for the d-line and the g-line.

[0283] From each aberration diagram, it can be seen that the first optical system OS1 of this embodiment appropriately corrects various aberrations and has high optical performance for the d-line and g-line.

[0284] FIG. 22 is a cross-sectional view of the second optical system OS2 included in the optical system 1 of the fifth example.

[0285] The second optical system OS2 of this embodiment has, in order from the object side, a meniscus-shaped negative lens L1 with a convex surface facing the object side, a meniscus-shaped negative lens L2 with a convex surface facing the object side, a meniscus-shaped negative lens L3 with a concave surface facing the object side, an optical path branching member OB, a biconvex positive lens L21, an aperture stop ST2, a meniscus-shaped positive lens L22 with a convex surface facing the object side, a meniscus-shaped positive lens L23 with a convex surface facing the object side, and a biconvex positive lens L24.

[0286] An image pickup element made up of a CCD, CMOS or the like is disposed on the image plane I2.

[0287] In the second optical system OS2 of this embodiment, the negative lens L1, the negative lens L2, and the negative lens L3 are included in the front lens group GR1, and the positive lens L21, the aperture stop ST2, the positive lens L22, the positive lens L23, and the positive lens L24 are included in the second rear lens group GR2S.

[0288] Table 5-2 below lists the specifications of the second optical system OS2 of this embodiment.

[0289] (Table 5-2) [Lens specifications] m r d n(d) νd ns 1) 29.39415 1.200 1.700 48.10 1.631 2) 7.87468 3.100 3) 31.19550 1.200 1.487 70.32 1.610 4) 8.16096 4.050 5) -10.84631 4.650 1.744 44.80 1.735 6) -13.43511 7.000 7) ∞ 0.300 1.517 63.88 1.510 (Branch plane BF) 8) ∞ 7.000 9) 56.18678 2.900 1.519 69.89 1.512 10) -76.02105 2.500 11) ∞ 1.000 (Aperture stop ST2) 12) 15.05046 2.000 1.762 40.11 1.747 13) 47.09491 3.640 14) 9.36251 2.750 1.755 27.57 1.735 15) 12.22463 2.475 *16) 11.58211 5.500 1.689 31.16 1.672 *17) -224.86865 3.000 18) ∞ 0.300 1.517 63.88 1.510 (Filter FL2) 19) ∞ 0.455 [Aspherical data] m K A4 A6 A8 A10 16) -6.9904 1.97E-04 -1.78E-05 2.75E-07 -8.03E-10 17) -9.0000 -2.93E-04 6.27E-07 4.02E-07 -2.73E-09 [Overall specifications] Fno 1.27 f 2.82 TL 54.92 Y 2.29 2ω 92.00

[0290] 23 is a diagram showing various aberrations of the second optical system OS2 included in the optical system 1 of Example 5. Each aberration diagram shows values ​​for the s-line.

[0291] From each aberration diagram, it can be seen that the second optical system OS2 of this embodiment appropriately corrects various aberrations and has high optical performance for the s-line.

[0292] According to each of the above embodiments, it is possible to realize an optical system that appropriately forms an image of the light transmitted through the splitting surface and the light reflected by the splitting surface out of the incident light.

[0293] The values ​​corresponding to the conditional expressions in each example are shown below.

[0294] f(L) is the focal length of the first optical system OS1, f(S) is the focal length of the second optical system OS2, TL(L) is the total optical length of the first optical system OS1, and TL(S) is the total optical length of the second optical system OS2.

[0295] f(fL) is the longer of the focal length of the first optical system OS1 and the focal length of the second optical system OS2, and f(fS) is the shorter of the focal length of the first optical system OS1 and the focal length of the second optical system OS2.

[0296] f(gr1) is the composite focal length of the front lens group GR1. f(gr1n) is the composite focal length of the negative lenses in the front lens group GR1 that are arranged consecutively from the negative lens closest to the object toward the image surface. f(gr1p) is the composite focal length of the positive lenses in the front lens group GR1 that are arranged consecutively from the positive lens closest to the object toward the image surface. T(gr1) is the distance on the optical axis from the lens surface in the front lens group GR1 that is closest to the object to the lens surface in the front lens group GR1 that is closest to the image surface.

[0297] T(pL) is the length on the optical axis of the prism in the first optical system OS1, and T(pS) is the length on the optical axis of the prism in the second optical system OS2. T(pfL) is the length on the optical axis of the prism in the optical system having the longer focal length of either the first optical system OS1 or the second optical system OS2, and T(pfS) is the length on the optical axis of the prism in the optical system having the shorter focal length of either the first optical system OS1 or the second optical system OS2.

[0298] f(gr2L) is the composite focal length of the lenses in the first rear lens group GR2L that are closer to the image plane than the aperture stop ST1, and f(gr2S) is the composite focal length of the lenses in the second rear lens group GR2S that are closer to the image plane than the aperture stop ST2.

[0299] f(lL) is the focal length of the lens closest to the image surface in the first rear lens group GR2L, and f(lS) is the focal length of the lens closest to the image surface in the second rear lens group GR2S.

[0300] Nave(s) is the average refractive index for the s-line of the negative lenses included in the front lens group GR1, 2ωL is the total angle of view of the first optical system OS1, and 2ωS is the total angle of view of the second optical system OS2.

[0301] The values ​​described in [Conditional Expression Corresponding Values] are values ​​for the d-line, except for the value of conditional expression (16), which is a value for the s-line.

[0302] [Values ​​corresponding to conditional expressions] Example Conditional Expression 1st 2nd 3rd 4th 5th (1) -f(gr1n) / f(L) 2.771 1.786 2.871 2.855 1.857 (2) T(pL) / T(pS) 2.955 2.708 2.765 1.000 - (3) -f(gr1n) / f(S) 1.562 3.249 1.708 1.608 3.353 (26) TL(L) / TL(S) 1.202 1.188 1.507 1.096 1.103 (5) -f(gr1n) / f(gr1p) 0.109 0.089 0.068 0.019 - (6) f(gr2S) / -f(gr1) 1.368 0.999 1.809 2.415 1.158 (7) f(gr2L) / -f(gr1) 1.496 3.164 1.750 1.620 2.598 (8) f(lS) / -f(gr1n) 3.943 1.764 4.191 2.320 1.705 (9) f(lL) / -f(gr1n) 3.597 2.774 3.864 2.583 2.140 (10) f(gr2S) / f(S) 2.870 3.631 3.565 3.628 3.883 (11) f(gr2L) / f(L) 5.567 6.318 5.798 4.320 4.824 (12) T(pS) / f(S) 2.206 4.338 3.449 2.733 - (13) T(pL) / f(L) 11.559 6.456 16.030 4.851 - (14) T(gr1) / f(S) 3.657 3.958 2.876 3.784 5.031 (15) T(gr1) / f(L) 6.487 2.175 4.835 6.717 2.786 (16) Nave(s) 1.610 1.620 1.553 1.620 1.658 (17) f(lS) / f(lL) 1.096 0.636 1.085 0.898 0.797 (18) T(gr1) / -f(gr1) 1.743 1.089 1.459 2.519 1.500 (19) T(gr1) / -f(gr1n) 2.341 1.218 1.684 2.353 1.500 (20) T(gr1) / f(fL) 3.657 2.175 2.876 3.784 2.786 (21) T(pfL) / f(fL) 2.206 6.456 3.449 2.733 - (22) T(gr1) / f(fS) 6.487 3.958 4.835 6.717 5.031 (23) T(pfS) / f(fS) 11.559 4.338 16.030 4.851 - (24) 2ωL 92.00 92.00 92.00 92.00 92.00 (25) 2ωS 92.00 92.00 92.00 116.00 92.00.

[0303] The above examples are merely illustrative of the present invention, and the present invention is not limited to these.

[0304] Next, an optical device including the optical system 1 of this embodiment will be described with reference to Fig. 24. Fig. 24 is a schematic diagram of an optical device 10 including the optical system 1 of this embodiment.

[0305] The optical device 10 includes the optical system 1 according to the first embodiment, an information processing device 2, a first imaging unit IS1, and a second imaging unit IS2.

[0306] The first and second image capturing units IS1 and IS2 each include an image capturing element configured with a CCD, CMOS, or the like. In the optical device 10, the optical system 1 appropriately forms images of incident light, the light reflected by the splitting surface BF, and the light transmitted through the splitting surface BF, using the first and second optical systems OS1 and OS2, respectively. The first and second image capturing units IS1 and IS2 are disposed on the image plane I1 of the first and second optical systems OS1 and OS2, respectively, and output data corresponding to the incident light. The information processing device 2 performs processing using the data output by the first and second image capturing units IS1 and IS2.

[0307] For example, the optical system 1 included in the optical device 10 has a splitting surface BF that transmits visible light and reflects near-infrared light from light incident on the optical system 1 from an object. The first optical system OS1 included in the optical system 1 forms an image of near-infrared light, and the second optical system OS2 forms an image of visible light. The information processing device 2 included in the optical device 10 detects the distance to the object from the image formed by the first optical system OS1. The information processing device 2 included in the optical device 10 also detects the appearance of the object by generating image data from the image formed by the second optical system OS2.

[0308] In this way, the optical device 10 can appropriately image each of the light that is transmitted by the branching surface BF and the light that is reflected by the branching surface BF out of the incident light, and perform processing using each image.

[0309] The optical device 10 may include an optical system in which the first optical system OS1 forms an image of visible light and the second optical system OS2 forms an image of near-infrared light, as in the optical system 1 of Example 2. In this case, the information processing device 2 detects the appearance of the object by generating image data from the image formed by the first optical system OS1, and detects the distance to the object from the image formed by the second optical system OS2.

[0310] Finally, an outline of a method for manufacturing the optical system 1 of this embodiment will be described with reference to Fig. 25. Fig. 25 is a flow chart showing an outline of the method for manufacturing the optical system 1 of this embodiment.

[0311] The method for manufacturing the optical system 1 of this embodiment shown in FIG. 25 includes the following steps S1, S2, and S3.

[0312] Step S1: Prepare a front lens group GR1, an optical path splitting member OB having a splitting surface BF, a first rear lens group GR2L, and a second rear lens group GR2S.

[0313] Step S2: The total optical length of the first optical system OS1 is set equal to or longer than the total optical length of the second optical system OS2.

[0314] Step S3: The lens groups and the optical path branching member OB are arranged so as to satisfy the following conditional expression (18): 0.50 < T(gr1) / (-f(gr1)) < 4.50, where T(gr1) is the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, and f(gr1) is the composite focal length of the front lens group.

[0315] In a modified example, steps S1A and S3A shown below may be executed instead of steps S1 and S3 in the method for manufacturing the optical system 1 of this embodiment shown in FIG.

[0316] Step S1A: Prepare a front lens group GR1, a prism having a splitting surface BF, a first rear lens group GR2L, and a second rear lens group GR2S.

[0317] Step S3A: Arrange each lens group and prism so as to satisfy the following conditional expressions: (20) 1.10 < T(gr1) / f(fL) < 5.20 (21) 1.00 < T(pfL) / f(fL) < 11.50 where, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, f(fL): the focal length of the first optical system or the focal length of the second optical system, whichever is longer, and T(pfL): the length on the optical axis of the prism in the optical system with the longer focal length of the first optical system or the second optical system.

[0318] In another modified example, step S3B described below may be executed instead of step S3A in the manufacturing method of the modified example described above.

[0319] Step S3B: Arrange each lens group and prism so as to satisfy the following conditional expressions: (22) 2.50 < T(gr1) / f(fS) < 9.50 (23) 3.00 < T(pfS) / f(fS) < 20.00 where, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object to the lens surface of the front lens group closest to the image plane, f(fS): the focal length of the first optical system or the focal length of the second optical system, whichever is shorter, and T(pfS): the length on the optical axis of the prism in the optical system with the shorter focal length of the first optical system or the second optical system.

[0320] According to the manufacturing method of the optical system of this embodiment, it is possible to manufacture an optical system that appropriately forms an image of each of the light transmitted through the splitting surface and the light reflected by the splitting surface out of the incident light.

[0321] In the optical system of this embodiment, the lens surface may be spherical or flat, or may be aspherical. A spherical or flat lens surface is preferred because it facilitates lens processing and assembly adjustment, and prevents degradation of optical performance due to errors in processing and assembly adjustment. Furthermore, a spherical or flat lens surface is preferred because it minimizes degradation of imaging performance when the image plane is misaligned.

[0322] In the case where the lens surface is aspherical, the aspherical surface may be formed by grinding glass or by glass molding using a mold having an aspherical shape, or may be formed on the surface of a resin bonded to the surface of the glass. In addition, in the optical system of this embodiment, the lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0323] Furthermore, an anti-reflection coating having high transmittance over a wide wavelength range may be applied to the lens surfaces of the lenses constituting the optical system of this embodiment, thereby reducing flare and ghosting and achieving high-contrast optical performance.

[0324] In the optical system of this embodiment, instead of providing an independent member as the aperture stop, the role of the lens frame or the like may be substituted.

[0325] It should be understood that those skilled in the art can make various changes, substitutions, and alterations thereto without departing from the spirit and scope of the present disclosure.

[0326] 1 Optical system OS1 First optical system OS2 Second optical system OB Optical path branching member BF Branching surface GR1 Front lens group GR2L First rear lens group GR2S Second rear lens group ST1, ST2 Aperture stop I1, I2 Image surface 10 Optical device

Claims

1. a first optical system including, in order from the object side, a front lens group, a light path branching member having a branching surface that transmits a portion of incident light and reflects at least another portion different from the portion of the incident light, and a first rear lens group into which one of the transmitted light and the reflected light is incident; a second optical system including, in order from an object side, the front lens group, the optical path branching member, and a second rear lens group onto which the other of the transmitted light and the reflected light is incident, An optical system that satisfies the following conditions: 0.50 < T(gr1) / (-f(gr1)) < 4.50 however, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object side to the lens surface of the front lens group closest to the image surface side f(gr1): composite focal length of the front lens group

2. 2. The optical system according to claim 1, which satisfies the following condition: 0.80 < T(gr1) / (-f(gr1n)) < 4.60 however, f(gr1n): a composite focal length of the negative lenses arranged consecutively on the image plane side from the negative lens arranged closest to the object side among the negative lenses included in the front lens group

3. 2. The optical system according to claim 1, which satisfies the following condition: 1.00 < TL(L) / TL(S) < 3.50 TL(L): total optical length of the first optical system TL(S): total optical length of the second optical system

4. a first optical system including, in order from the object side, a front lens group, a prism having a splitting surface that transmits a portion of incident light and reflects at least another portion different from the portion of the incident light, and a first rear lens group into which one of the transmitted light and the reflected light is incident; a second optical system including, in order from the object side, the front lens group, the prism, and a second rear lens group onto which the other of the transmitted light and the reflected light is incident, the total optical length of the first optical system is longer than the total optical length of the second optical system, An optical system that satisfies both of the following conditions: 1.10 < T(gr1) / f(fL) < 5.20 1.00 < T(pfL) / f(fL) < 11.50 however, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object side to the lens surface of the front lens group closest to the image surface side f(fL): the longer of the focal length of the first optical system and the focal length of the second optical system T(pfL): the length on the optical axis of the prism in the optical system having the longer focal length out of the first optical system and the second optical system

5. a first optical system including, in order from the object side, a front lens group, a prism having a splitting surface that transmits a portion of incident light and reflects at least another portion different from the portion of the incident light, and a first rear lens group into which one of the transmitted light and the reflected light is incident; a second optical system including, in order from the object side, the front lens group, the prism, and a second rear lens group onto which the other of the transmitted light and the reflected light is incident, the total optical length of the first optical system is longer than the total optical length of the second optical system, An optical system that satisfies both of the following conditions: 2.50 < T(gr1) / f(fS) < 9.50 3.00 < T(pfS) / f(fS) < 20.00 however, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object side to the lens surface of the front lens group closest to the image surface side f(fS): the shorter of the focal length of the first optical system and the focal length of the second optical system T(pfS): the length on the optical axis of the prism in the optical system having the shorter focal length out of the first optical system and the second optical system

6. 6. The optical system according to claim 4, wherein the following condition is satisfied: 1.10 < T(pL) / T(pS) < 5.50 however, T(pL): Length of the prism on the optical axis in the first optical system T(pS): Length of the prism on the optical axis in the second optical system

7. 6. The optical system according to claim 4, wherein the following condition is satisfied: 1.20 < T(pS) / f(S) < 6.40 however, T(pS): Length of the prism on the optical axis in the second optical system f(S): focal length of the second optical system

8. 6. The optical system according to claim 4, wherein the following condition is satisfied: 2.40 < T(pL) / f(L) < 20.50 T(pL): Length of the prism on the optical axis in the first optical system f(L): focal length of the first optical system

9. 6. The optical system according to claim 3, wherein the following condition is satisfied: 1.40 < T(gr1) / f(S) < 6.90 however, f(S): focal length of the second optical system

10. 6. The optical system according to claim 3, wherein the following condition is satisfied: 1.00 < T(gr1) / f(L) < 9.80 however, f(L): focal length of the first optical system

11. 6. The optical system according to claim 3, wherein the following condition is satisfied: 0.80 < -f(gr1n) / f(L) < 4.30 f(gr1n): a composite focal length of the negative lenses arranged consecutively on the image plane side from the negative lens arranged closest to the object side among the negative lenses included in the front lens group f(L): focal length of the first optical system

12. 6. The optical system according to claim 3, wherein the following condition is satisfied: 0.50 < -f(gr1n) / f(S) < 4.40 however, f(gr1n): a composite focal length of the negative lenses arranged consecutively on the image plane side from the negative lens arranged closest to the object side among the negative lenses included in the front lens group f(S): focal length of the second optical system

13. 6. The optical system according to claim 3, wherein the second rear lens group has an aperture stop, and the following condition is satisfied: 0.50 < f(gr2S) / (-f(gr1)) < 3.40 however, f(gr2S): composite focal length of the lens in the second rear lens group located closer to the image plane than the aperture stop f(gr1): composite focal length of the front lens group

14. 6. The optical system according to claim 3, wherein the first rear lens group has an aperture stop and satisfies the following condition: 0.40 < f(gr2L) / (-f(gr1)) < 4.20 however, f(gr2L): composite focal length of the lens in the first rear lens group located closer to the image plane than the aperture stop f(gr1): composite focal length of the front lens group

15. 6. The optical system according to claim 3, wherein the following condition is satisfied: 0.70 < f(lS) / (-f(gr1n)) < 5.90 however, f(ls): focal length of the lens in the second rear lens group closest to the image surface f(gr1n): a composite focal length of the negative lenses arranged consecutively on the image plane side from the negative lens arranged closest to the object side among the negative lenses included in the front lens group

16. 6. The optical system according to claim 3, wherein the following condition is satisfied: 1.50 < f(lL) / (-f(gr1n)) < 7.70 however, f(IL): focal length of the lens in the first rear lens group closest to the image surface f(gr1n): a composite focal length of the negative lenses arranged consecutively on the image plane side from the negative lens arranged closest to the object side among the negative lenses included in the front lens group

17. 6. The optical system according to claim 3, wherein the second rear lens group has an aperture stop, and the following condition is satisfied: 1.60 < f(gr2S) / f(S) < 5.60 however, f(gr2S): composite focal length of the lens in the second rear lens group located closer to the image plane than the aperture stop f(S): focal length of the second optical system

18. 6. The optical system according to claim 3, wherein the first rear lens group has an aperture stop, and the following condition is satisfied: 2.30 < f(gr2L) / f(L) < 8.80 however, f(gr2L): composite focal length of the lens in the first rear lens group located closer to the image plane than the aperture stop f(L): focal length of the first optical system

19. 6. The optical system according to claim 3, wherein the following condition is satisfied: 0.23 < f(lS) / f(lL) < 1.50 however, f(lS): focal length of the lens in the second rear lens group closest to the image surface f(IL): focal length of the lens in the first rear lens group closest to the image surface

20. 6. The optical system according to claim 1, wherein the following condition is satisfied: 0.01 < -f(gr1n) / f(gr1p) < 0.21 however, f(gr1n): a composite focal length of the negative lenses arranged consecutively on the image plane side from the negative lens arranged closest to the object side among the negative lenses included in the front lens group f(gr1p): composite focal length of the positive lenses arranged consecutively on the image plane side from the positive lens arranged closest to the object side among the positive lenses included in the front lens group

21. 6. The optical system according to claim 1, wherein the following condition is satisfied: 1.50 < Nave(s) < 1.90 however, Nave(s): average refractive index for the s-line of the negative lenses included in the front lens group

22. The optical system of claim 1 , 4 , or 5 , wherein the front lens group has negative refractive power.

23. 6. The optical system according to claim 1, wherein the front lens group includes at least one positive lens and at least one negative lens.

24. The optical system according to claim 1 , wherein the first optical system and the second optical system each have a positive lens closest to an image plane.

25. 6. The optical system according to claim 1, wherein the following conditional expressions are all satisfied: 80.0° < 2ωL 80.0° < 2ωS however, 2ωL: full angle of view of the first optical system 2ωS: full angle of view of the second optical system

26. 6. The optical system according to claim 1, wherein one of the transmitted light and the reflected light is visible light and the other is near-infrared light, and wherein, of the first optical system and the second optical system, an optical system using the visible light on an image plane side from the splitting surface has a cemented lens, and an optical system using the near-infrared light on an image plane side from the splitting surface is made of only a single lens.

27. An optical instrument comprising an optical system according to any one of claims 1, 4 and 5.

28. a first optical system including, in order from the object side, a front lens group, a light path branching member having a branching surface that transmits a portion of incident light and reflects at least another portion different from the portion of the incident light, and a first rear lens group into which one of the transmitted light and the reflected light is incident; a second optical system including, in order from an object side, the front lens group, the optical path splitter, and a second rear lens group onto which the other of the transmitted light and the reflected light is incident; a total optical length of the first optical system is equal to or longer than a total optical length of the second optical system, A manufacturing method for an optical system in which each lens group and each optical path branching member are arranged so as to satisfy the following conditional expression: 0.50 < T(gr1) / (-f(gr1)) < 4.50 however, T(gr1): the distance on the optical axis from the lens surface of the front lens group closest to the object side to the lens surface of the front lens group closest to the image surface side f(gr1): composite focal length of the front lens group