Lens device and imaging device

Abstract

To provide a lens device which is small and has a large base line length and can acquire a three-dimensional image that has a natural three-dimensional feeling with respect to a far object.SOLUTION: A lens device (100) includes two optical systems (101, 102). The two optical systems comprise a first lens group (L1) with the positive refractive power, a second lens group (L2) with the negative refractive power, a first reflection surface (R1), a second reflection surface (R2) and a rear lens group (LR) with the positive refractive power arranged in the order from the object side to the image side. In the variable magnification, at least an interval between the first lens group and the second lens group and an interval between the second lens group and the first reflection surface change. An interval Din between surface apexes of a lens arranged closest to the object side in the two optical systems and an interval Dout between surface apexes of a lens arranged closest to the image side in the two optical systems satisfy a prescribed conditional expression.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a lens device and an imaging device. [Background technology]

[0002] There is a demand for imaging devices that can capture stereoscopic images (video) to capture images used in content that provides a sense of realism, such as virtual reality. Patent Document 1 discloses a lens device that can increase the baseline length despite its compact size by forming an optical image on a single imaging element using the bending of the optical paths of two optical systems. Patent Document 2 discloses an observation optical system that changes magnification by varying the air gap within the objective lens. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-8629 [Patent Document 2] Japanese Patent Application Publication No. 11-258518 Summary of the Invention [Problem to be solved by the invention]

[0004] The lens device disclosed in Patent Document 1 reduces the three-dimensional effect of distant objects during stereoscopic viewing. To capture three-dimensional images (videos) with a natural three-dimensional effect for objects at various object distances, including distant objects, it is necessary to use a more telephoto variable magnification optical system. The observation optical system disclosed in Patent Document 2 is not designed to form two optical images on a single imaging element, making it difficult to miniaturize the system while avoiding physical interference between the optical elements.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a lens device and an imaging device that are small, have a long base line length, and are capable of acquiring stereoscopic images with a natural three-dimensional effect for distant objects. [Means for solving the problem]

[0006] A lens device according to one aspect of the present invention has two optical systems, each of which has, arranged in order from the object side to the image side, a first lens group with positive refractive power, a second lens group with negative refractive power, a first reflecting surface, a second reflecting surface, and a rear lens group with positive refractive power, and during magnification variation, at least the distance between the first lens group and the second lens group and the distance between the second lens group and the first reflecting surface change, and a distance Din between the vertices of the lenses located closest to the object in the two optical systems and a distance Dout between the vertices of the lenses located closest to the image in the two optical systems satisfy a predetermined conditional expression.

[0007] Other objects and features of the present invention are illustrated in the following examples. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a lens device and an imaging device that are small in size, have a large base line length, and are capable of acquiring a stereoscopic image that has a natural three-dimensional effect for a distant object. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a main part of a lens device according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram of an image circle in the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view of an optical system according to the first embodiment. [Figure 4] FIG. 2 is a schematic diagram of a lens barrel according to the first embodiment. [Figure 5] 3A to 3C are aberration diagrams of the optical system in Example 1. [Figure 6] FIG. 10 is a cross-sectional view of an optical system according to a second embodiment. [Figure 7] FIG. 10 is a light path diagram of an optical system in Example 2. [Figure 8] 10A to 10C are aberration diagrams of the optical system in Example 2. [Figure 9]FIG. 10 is a cross-sectional view of an optical system according to a third embodiment. [Figure 10] 10A to 10C are aberration diagrams of the optical system in Example 3. [Figure 11] FIG. 10 is a cross-sectional view of an optical system according to a fourth embodiment. [Figure 12] 10A to 10C are aberration diagrams of the optical system in Example 4. [Figure 13] 1 is a schematic diagram of an imaging device including an optical system according to each embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] First, an imaging optical system (lens apparatus) according to a first embodiment will be described with reference to FIG. 1. FIG. 1 is a cross-sectional view of a main portion of an imaging optical system (lens apparatus) 100 according to this embodiment. The imaging optical system 100 has two optical systems 101 and 102. The optical systems 101 and 102 are held by a housing (not shown). The optical systems 101 and 102 are identical except for the direction of reflection of the reflecting members, which will be described later, and therefore the following description will focus on the optical system 101 as a representative. Hereinafter, when it is said that the optical systems 101 and 102 are identical, it means that the lens configuration and the like are identical except for the direction of reflection of the reflecting members.

[0012] The optical system 101 has an intermediate group LM that bends the optical path. The intermediate group LM has a first reflecting surface R1 and a second reflecting surface R2. However, in this embodiment, the intermediate group LM has no refractive power. In this embodiment, an optical axis AX1 on the object side of the first reflecting surface R1 and an optical axis AX2 on the image side of the second reflecting surface R2 are parallel to each other, but the optical axis AX1 may be slightly inwardly rotated. Furthermore, "parallel" does not necessarily mean strictly parallel, but also includes a state where the axes are deviated from parallel by approximately ±5° (a substantially parallel state).

[0013] In FIG. 1, IP denotes the image plane (paraxial imaging position). An imaging element such as a CCD sensor or a CMOS sensor, or a film, is disposed on the image plane IP. An image (optical image) is formed on the image plane IP by optical systems 101 and 102. That is, two optical images are formed on one imaging element by the two optical systems 101 and 102 in the imaging optical system 100.

[0014] Next, two image circles (areas where an optical image is formed, i.e., effective image circle diameters) IC1 and IC2 formed on the image plane IP in this embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic diagram of the image circles IC1 and IC2. The image circle IC1 is an image circle formed by the optical system 101, and the image circle IC2 is an image circle formed by the optical system 102. In this way, in this embodiment, two images with parallax can be acquired with a single image sensor.

[0015] Next, the optical system 101 in this embodiment will be described in detail with reference to Fig. 3. Fig. 3 is a cross-sectional view of the optical system 101 in this embodiment. However, in Fig. 3, the optical path bent by the first reflecting surface R1 and the second reflecting surface R2 is shown unfolded. The optical system 101 has, arranged in this order from the object side to the image side, a first lens group L1, a second lens group L2, a first reflecting surface R1, a second reflecting surface R2, and a rear lens group LR. When the magnification is changed, at least the distance between the first lens group L1 and the second lens group L2 and the distance between the second lens group L2 and the first reflecting surface R1 change.

[0016] The first lens group L1 has positive refractive power. In this embodiment, the first lens group L1 moves during magnification, but it may be configured not to move as in embodiments described below. The second lens group L2 has negative refractive power and moves during magnification. In this embodiment, the first reflecting surface R1 is located adjacent to the second lens group L2. However, as described below, a lens group with positive refractive power or an aperture stop may be located between the second lens group L2 and the first reflecting surface R1. The rear lens group LR has positive refractive power. The first reflecting surface R1 and the second reflecting surface R2 are located close to each other and are preferably housed inside the same undivided lens barrel (an integrated lens barrel).

[0017] To capture a stereoscopic image using a single image sensor, the image circles IC1 and IC2 of the optical systems 101 and 102 must be separated. To separate the image circles IC1 and IC2 at a desired angle of view, it is preferable to provide a field stop FD1 closer to the object than the first lens group L1. Alternatively, it is preferable to provide a field stop FD2 closer to the image than the rear lens group LR. In other words, it is preferable to place a field stop at least one of the positions closest to the object or closest to the image in the optical system 101.

[0018] Next, the lens barrel of this embodiment will be described with reference to FIGS. 4A and 4B. FIGS. 4A and 4B are schematic diagrams of the lens barrel, with FIG. 4A showing a lens barrel divided between two reflecting surfaces by an aperture unit, and FIG. 4B showing a lens barrel integrated between the two reflecting surfaces. FIG. 4A corresponds to the configuration disclosed in Patent Document 1, and FIG. 4B corresponds to this embodiment. In Patent Document 1, an aperture diaphragm is inserted between the two reflecting surfaces R1 and R2 that bend the optical path, so each reflecting surface must be housed in a separate lens barrel. This is because the aperture diaphragm unit generally has a larger diameter than the housing that holds the lens. Therefore, in the configuration of Patent Document 1, relative optical axis misalignment occurs between the divided lens barrels, resulting in misalignment and rotation of the optical image, which leads to a decrease in image quality.

[0019] On the other hand, this embodiment aims to achieve a telephoto lens greater than the configuration of Patent Document 1, which makes the impact of lens barrel misalignment more pronounced. For this reason, an aperture stop is not provided between the two reflecting surfaces, and the two reflecting surfaces are housed in a single lens barrel. That is, in this embodiment, the first reflecting surface R1 and the second reflecting surface R2 are held by an integrated lens barrel. This configuration reduces the relative positional misalignment between the two reflecting surfaces, thereby improving image quality. Note that in this embodiment, the first reflecting surface R1 and the second reflecting surface R2 are each formed on the inclined surfaces of a rectangular prism. However, as will be described later, they may also be formed on two parallel surfaces of a single integrated optical element, such as a simple plane mirror or a prism.

[0020] It is best to arrange the first reflecting surface R1 and the second reflecting surface R2 between the second lens group L2 and the rear lens group LR, as in this embodiment. The reason for this is that if the reflecting surfaces were arranged closer to the object than the second lens group L2, the diameters of the first lens group L1 and the first reflecting surface R1 would become larger, resulting in an increase in the size of the imaging optical system 100. Furthermore, to arrange the reflecting surfaces closer to the image than the rear lens group LR, it is necessary to ensure an appropriate back focus, and therefore, if the refractive power of the rear lens group LR is reduced, the diameter of the lenses in the rear lens group LR would become larger, resulting in interference between the optical systems 101 and 102.

[0021] The optical system 101 of this embodiment is configured to satisfy the following conditional expression by bending the optical path by the first reflecting surface R1 and the second reflecting surface R2. This also applies to the optical systems of the other embodiments described below.

[0022] 0.05 <Dout / Din<0.50 …(1) Here, Din is the distance between the vertices of the lenses located closest to the object in the two optical systems 101 and 102, and Dout is the distance between the vertices of the lenses located closest to the image in the two optical systems 101 and 102. The distance Din is called the base length and is related to the stereoscopic effect of a stereoscopic image.

[0023] Conditional expression (1) defines the ratio of the distance Din between the object-side lens surfaces of the two optical systems 101 and 102 to the distance Dout between the image-side lens surfaces. Satisfying conditional expression (1) enables the overall device to be compact while ensuring a sufficient base length for stereoscopic viewing. If the lower limit of conditional expression (1) is exceeded, the lenses of the two optical systems 101 and 102 located closer to the image than the second reflecting surface R2 may physically interfere with each other. Alternatively, the base length may become too long, resulting in excessive parallax. This results in a stereoscopic image that is not suitable for human viewing. On the other hand, if the upper limit of conditional expression (1) is exceeded, the base length may become too short, resulting in insufficient parallax. This makes it difficult for humans to obtain a sense of three-dimensionality when viewing the image, making the device unsuitable for capturing stereoscopic images. With the above configuration, this embodiment provides a compact, variable-magnification imaging optical system (lens device) with a long base length and high image quality.

[0024] Preferably, the numerical range of conditional formula (1) is set as shown in the following conditional formula (1a) in order to achieve stereoscopic photography that has a more natural three-dimensional effect for the human visual sense. More preferably, the numerical range of conditional formula (1) is set as shown in the following conditional formula (1b).

[0025] 0.07 <Dout / Din<0.47 …(1a) 0.13 <Dout / Din<0.42 …(1b) Next, a preferred configuration of the imaging optical system 100 of this embodiment will be described. The preferred configuration described below may be satisfied by at least one of the two optical systems 101 and 102. More preferably, the two optical systems 101 and 102 may have the same configuration, so that the preferred configuration described below may be satisfied by both of the two optical systems 101 and 102.

[0026] In this embodiment, an aperture diaphragm SP is disposed between the second lens group L2 and the first reflecting surface R1. If the aperture diaphragm SP is disposed closer to the object than the second lens group L2, the ray height of the off-axial light beam increases in the rear lens group LR, resulting in a larger lens diameter, making it difficult to avoid physical interference between the two optical systems 101 and 102. Furthermore, if the aperture diaphragm SP is disposed closer to the image than the second reflecting surface R2, the lens diameter of the rear lens group LR can be reduced, but it is difficult to avoid physical interference between the aperture units of the two optical systems 101 and 102. Furthermore, as mentioned above, if the aperture diaphragm SP is disposed between the first reflecting surface R1 and the second reflecting surface R2, a relative positional shift of the reflecting surfaces occurs, resulting in a decrease in image quality. For this reason, it is preferable to dispose the aperture diaphragm SP between the second lens group L2 and the first reflecting surface R1.

[0027] The first lens group L1 preferably has one negative meniscus lens having a convex surface facing the object side and two positive lenses. By sharing the positive refractive power of the first lens group L1 among two or more positive lenses, the occurrence of distortion and astigmatism can be suppressed. Furthermore, by having one or more negative lenses, chromatic aberration can be effectively corrected. The second lens group L2 preferably has two negative lenses and one positive lens, and more preferably has three negative lenses. By sharing the negative refractive power among two or more negative lenses, the occurrence of distortion and astigmatism can be suppressed. Furthermore, by having a positive lens, the occurrence of chromatic aberration can be suppressed.

[0028] It is preferable that the rear lens group LR does not move when the magnification is changed. The challenge on the image side of the second reflecting surface R2 is to avoid physical interference between the two optical systems 101 and 102, which are arranged in parallel. If the rear lens group LR is movable, then a lens barrel for moving the rear lens group LR will be provided inside the lens barrel housing the optical system 101. Such a multiplexed lens barrel configuration makes it even more difficult to avoid interference between the two optical systems 101 and 102. For this reason, it is preferable that the rear lens group LR does not move when the magnification is changed.

[0029] It is preferable that the optical system 101 of this embodiment satisfies the following conditional expression: This also applies to the optical systems of the other embodiments described below.

[0030] -1.60 <f12w / fw<-0.50 …(2) 0.25 <DRR / Din<0.49 …(3) 0.50 <f1 / fw<5.00 …(4) -2.00 <f2 / fw<-0.10 …(5) 0.50 <fR / fw<5.00 …(6) 1.00 <Dout / Φout<3.00 …(7) Here, f12w is the composite focal length of the first lens group L1 and the second lens group L2 at the wide-angle end for the d-line (wavelength 587.6 nm). Unless otherwise specified, all focal lengths hereinafter are based on the d-line. fw is the focal length of the entire optical system 101 at the wide-angle end. DRR is the distance along the optical axis between the first reflecting surface R1 and the second reflecting surface R2. f1 is the focal length of the first lens group L1. f2 is the focal length of the second lens group L2. fR is the focal length of the rear lens group LR. Φout is the effective diameter of the lens closest to the image side in the optical system 101. The effective diameter Φout is the diameter through which effective light rays that contribute to image formation pass through that lens.

[0031] Conditional expression (2) defines a preferable range for the relationship between the focal lengths of the first lens group L1 and the second lens group L2. Below the lower limit of conditional expression (2), the refractive power of the first lens group L1 becomes too weak, resulting in a large front lens diameter. On the other hand, above the upper limit of conditional expression (2), the refractive power of the first lens group L1 and the second lens group L2 becomes too strong, resulting in large lateral chromatic aberration and astigmatism. To achieve a good balance between the above-mentioned compactness and aberration correction, the numerical range of conditional expression (2) is preferably within the range of the following conditional expression (2a), and more preferably within the range of conditional expression (2b).

[0032] -1.55 <f12w / fw<-0.60 …(2a) -1.51 <f12w / fw<-0.77 …(2b) Conditional expression (3) defines a preferable range for the relationship between the distance between the first reflecting surface R1 and the second reflecting surface R2 and the distance Din between the vertices of the lenses located closest to the object. Below the lower limit of conditional expression (3), the base line length is insufficient, making it impossible to obtain a sufficient three-dimensional effect. On the other hand, above the upper limit of conditional expression (3), the distance DRR between the two reflecting surfaces becomes too large, causing off-axial light beams in the rear lens unit LR to pass through more of the lens's outer periphery. This results in a larger diameter for the lenses in the rear lens unit LR, making it difficult to arrange the two optical systems 101 and 102 side by side.

[0033] Preferably, the numerical range of conditional expression (3) is set as shown in the following conditional expression (3a) in order to achieve a better balance between the above-mentioned compactness and three-dimensional effect. More preferably, the numerical range of conditional expression (3) is set as shown in conditional expression (3b).

[0034] 0.26 <DRR / Din<0.48 …(3a) 0.28 <DRR / Din<0.47 …(3b) Conditional expression (4) defines a preferable range for the focal length of the first lens L1. If the lower limit of conditional expression (4) is not met, the refractive power of the first lens group L1 becomes too strong, resulting in large lateral chromatic aberration and astigmatism. On the other hand, if the upper limit of conditional expression (4) is exceeded, the refractive power of the first lens group L1 becomes too weak, increasing the overall optical length and making it difficult to reduce the size of the optical system. Preferably, the numerical range of conditional expression (4) is set to satisfy conditional expression (4a) below in order to achieve a good balance between the aberration correction and size reduction described above. More preferably, the numerical range of conditional expression (4) is set to satisfy conditional expression (4b) below.

[0035] 0.80 <f1 / fw<4.50 …(4a) 1.22 <f1 / fw<3.57 …(4b) Conditional expression (5) defines a preferable range for the focal length of the second lens group L2. If the lower limit of conditional expression (5) is not met, the refractive power of the second lens group L2 becomes too strong, resulting in large lateral chromatic aberration and astigmatism. On the other hand, if the upper limit of conditional expression (5) is exceeded, the refractive power of the second lens group L2 becomes too weak, increasing the overall optical length and making it difficult to reduce the size of the optical system. Preferably, the numerical range of conditional expression (5) is set to satisfy conditional expression (5a) below in order to achieve a better balance between the aberration correction and size reduction described above. More preferably, the numerical range of conditional expression (5) is set to satisfy conditional expression (5b) below.

[0036] -1.50 <f2 / fw<-0.20 …(5a) -0.95 <f2 / fw<-0.39 …(5b) Conditional expression (6) defines a preferable range for the focal length of the rear lens group LR. If the lower limit of conditional expression (6) is not met, the refractive power of the rear lens group LR becomes too strong, resulting in large chromatic aberration of magnification and astigmatism. Furthermore, it becomes impossible to ensure an appropriate back focus. On the other hand, if the upper limit of conditional expression (6) is exceeded, the refractive power of the rear lens group LR becomes too weak, increasing the overall optical length and making it difficult to reduce the size of the optical system. Preferably, the numerical range of conditional expression (6) is set to satisfy the following conditional expression (6a) in order to achieve a better balance between the aberration correction and size reduction described above. More preferably, the numerical range of conditional expression (6) is set to satisfy the following conditional expression (6b).

[0037] 0.75 <fR / fw<3.50 …(6a) 1.03 <fR / fw<2.23 …(6b) Conditional expression (7) defines a preferable range for the relationship between the distance Dout between the vertices of the lenses located closest to the image and the diameter of the lenses closest to the image. If the lower limit of conditional expression (7) is not met, the lenses in the rear lens groups of the optical systems 101 and 102 will physically interfere with each other. On the other hand, if the upper limit of conditional expression (7) is met, the diameter of the lenses in the rear lens group LR will be too small, reducing the amount of light and making it impossible to obtain high image quality. Preferably, the numerical range of conditional expression (7) is set to satisfy the following conditional expression (7a) in order to strike a balance between the physical interference and maximizing the amount of light. More preferably, the numerical range of conditional expression (7) is set to satisfy the following conditional expression (7b).

[0038] 1.05 <Dout / Φout<2.40 …(7a) 1.10 <Dout / Φout<1.63 …(7b) 5(A) and 5(B) are aberration diagrams of the optical system 101 of this embodiment when focused at infinity, with FIG. 5(A) showing the aberration diagram at the wide-angle end and FIG. 5(B) showing the aberration diagram at the telephoto end. In each aberration diagram, Fno is the F-number, and ω is the half angle of view (°). In the spherical aberration diagram, the solid line represents spherical aberration for the d-line (wavelength 587.6 nm), and the two-dot chain line represents spherical aberration for the g-line (wavelength 435.8 nm). In the astigmatism diagram, the solid line S represents astigmatism for the sagittal image plane at the d-line, and the dashed line M represents astigmatism for the meridional image plane at the d-line. In the distortion diagram, distortion for the d-line is shown. In the chromatic aberration diagram, chromatic aberration of magnification for the g-line is shown. These are the same for the subsequent aberration diagrams.

[0039] Next, optical systems 101a, 101b, and 101c in Examples 2 to 4 will be described with reference to FIGS. 6 to 12. FIG. 6 is a cross-sectional view of the optical system 101a in Example 2. In this Example, similar to Example 1, both the first reflecting surface R1 and the second reflecting surface R2 are formed by prisms. However, unlike Example 1, in this Example, the first reflecting surface R1 and the second reflecting surface R2 are formed on a single prism. That is, in this Example, the first reflecting surface R1 and the second reflecting surface R2 are reflective surfaces of an integrally molded optical element (integral prism). This configuration makes it easier to improve the parallelism between the first reflecting surface R1 and the second reflecting surface R2 compared to when the two reflecting surface elements are separated, thereby reducing manufacturing errors and improving image quality. The integral prism may have a parallelepiped shape, such as a parallelogram formed by joining two rectangular prisms and extruding it in a direction perpendicular to the plane of the paper in the cross-sectional view shown in FIG. 6. Alternatively, it may have a polyhedral shape, which is made smaller by cutting off portions unnecessary for bending the optical path.

[0040] Furthermore, this embodiment differs from Example 1, in that the angle of incidence α of the axial chief ray at the first reflecting surface R1 and the second reflecting surface R2 is 35°, which is 45°. Here, the angle of incidence α is the angle between the incident ray and a line perpendicular to the reflecting surface, as shown in FIG. 4 . Preferably, in each embodiment, the angle of incidence α (°) is set in the range of 20<α<50. More preferably, the angle of incidence α is set in the range of 20<α<46. By reflecting the ray at a sharper angle from the reflecting surface, it is possible to reduce the apparent curvature difference between the meridional cross section and the sagittal cross section, even when the reflecting surface has a curvature due to manufacturing errors, and thereby reduce the astigmatic difference, resulting in an effective configuration for improving image quality.

[0041] In this embodiment, a third lens group L3 having positive refractive power is disposed between the second lens group L2 and the first reflecting surface R1. Therefore, the optical system 101a includes, in order from the object side, a first lens group L1 having positive refractive power, a second lens group L2 having negative refractive power, a third lens group L3 having positive refractive power, and a rear lens group LR having positive refractive power. By using the lens groups L1, L2, and L3 to form an afocal optical system that only changes magnification, the axial light beam can be guided as parallel light to the first reflecting surface R1 and beyond, making it easy to reduce the effective diameter after bending the optical path. This makes it easy to avoid interference between the two optical systems 101 and 102, which is preferable. Furthermore, in this case, there is less aberration fluctuation on the object side of the first reflecting surface R1 during magnification change, which makes it easy to correct aberrations using the rear lens group LR, which is preferable.

[0042] The rear lens group LR includes a rear A lens group LRA, a rear B lens group LRB, and a rear C lens group LRC. The rear B lens group LRB may be configured to be movable in a direction perpendicular to the optical axis for image stabilization. The rear A lens group LRA is a lens group closer to the object side than the rear B lens group LRB. The rear C lens group LRC is a lens group closer to the image side than the rear B lens group LRB.

[0043] 7 is a ray diagram for the lens groups L1, L2, and L3 in the optical system 101a. The ray diagram in FIG. 7 shows the on-axis angle of view and the most off-axis angle of view. Note that afocal here does not only refer to a case where the marginal ray of the on-axis light beam is completely parallel to the optical axis, but may also refer to an angle of about ±10°.

[0044] In this embodiment, the third lens group L3 moves during zooming, but the rear lens group LR may compensate for the image plane position so that the third lens group L3 does not move during zooming. Alternatively, a second lens group L2N having negative refractive power may be disposed between the second lens group L2 and the third lens group L3, and this may be used as the group that compensates for the image plane position during zooming. The third lens group L3 preferably includes one positive lens and one negative lens to effectively correct chromatic aberration.

[0045] This embodiment has a four-group configuration consisting of a positive first lens group L1, a negative second lens group L2, a positive third lens group L3, a first reflecting surface R1, a second reflecting surface R2, and a positive rear lens group L1. This configuration minimizes the number of groups, making it possible to configure a variable magnification optical system that provides high image quality while minimizing the size of the imaging optical system 100.

[0046] In this embodiment, the first lens unit L1 does not move during zooming, which eliminates misalignment of the optical axis of the first lens unit L1 during zooming, providing a configuration that is favorable for achieving high image quality.

[0047] Preferably, the optical system 101a satisfies at least one of the following conditional expressions (8) to (11): This also applies to the optical systems 101b and 101c of Examples 3 and 4, which will be described later.

[0048] 1.00<|fRA / fRB|<2.00 …(8) 0.20 <f3 / ft<1.00 …(9) 0.20 <f3 / min(D3R)<1.40 …(10) 0.20 <min(D3R) / Max(Dtotal)<0.80 …(11) 0.60 <f3 / fw<3.00 …(12) Here, fRA and fRB are the focal lengths of the rear A lens group LRA and the rear B lens group LRB, respectively, when the rear lens group LR has a vibration-reduction function (image stabilization function). f3 is the focal length of the third lens group L3. ft is the focal length of the entire optical system 101 at the telephoto end. D3R is the distance along the optical axis between the third lens group L3 and the rear lens group LR. That is, the distance D3R is the sum (D1 + DRR + D2) of the distance along the optical axis D1 between the optical surface of the third lens group L3 closest to the image and the first reflecting surface R1, the distance DRR, and the distance along the optical axis D2 between the optical surface of the rear lens group LR closest to the object. min(D3R) is the minimum value of the distance D3R during zooming. Dtotal is the distance along the optical axis between the optical surface closest to the object and the optical surface closest to the image in the optical system 101, and Max(Dtotal) is the maximum value of the distance Dtotal during zooming. In this example, the optical surface refers to the boundary surface through which light rays pass when in use, and the surface extending from that boundary surface with the same radius of curvature. In particular, a reflecting surface is also defined as an optical surface. In each example, distance refers to the actual length.

[0049] Conditional expression (8) defines a preferable range for the relationship between the refractive powers of the movable and non-movable groups in the rear lens group LR when image stabilization (shake correction) is performed by the rear lens group LR. In this embodiment, the rear B lens group LRB of the rear lens group LR is movable for image stabilization by a movement amount having a component perpendicular to the optical axis. This enables image stabilization, resulting in a configuration preferable for achieving high image quality. Note that for image stabilization, it is sufficient to provide at least one of the rear A lens group LRA or the rear C lens group LRC. However, since the movement amount of the rear B lens group LRB required for image stabilization is not too large, it is preferable to provide both the rear A lens group LRA and the rear C lens group LRC in order to improve the image stabilization sensitivity of the rear B lens group LRB to a certain extent while effectively correcting aberrations. Note that image stabilization sensitivity refers to the ratio |Δ2 / Δ1| of the movement amount Δ2 of the image point on the image plane to the movement amount Δ1 of the image stabilization lens group in the direction perpendicular to the optical axis.

[0050] If the upper limit of conditional expression (8) is exceeded, the negative refractive power becomes stronger and image stabilization performance improves, but the diameter of the lenses in the rear lens group LR becomes larger, making it difficult to avoid physical interference between the optical systems 101 and 102. On the other hand, if the lower limit of conditional expression (8) is not reached, the negative refractive power becomes too weak and sufficient image stabilization performance cannot be obtained. Preferably, the numerical range of conditional expression (8) is set as shown in the following conditional expression (8a) in order to maximize image stabilization performance while avoiding the above-mentioned physical interference. More preferably, conditional expression (8) is set as shown in conditional expression (8b).

[0051] 1.10<|fRA / fRB|<1.90 …(8a) 1.29<|fRA / fRB|<1.70 …(8b) Conditional expression (9) defines a preferable range for the focal length of the third lens group L3. Below the lower limit of conditional expression (9), the off-axial light beam is angled too much in the third lens group L3, resulting in a large diameter of the lens in the rear lens group LR. On the other hand, above the upper limit of conditional expression (9), the refractive power of the third lens group L3 becomes too weak, the distance between the second lens group L2 and the third lens group L3 becomes large, and the diameter of the front lens becomes large. Furthermore, the overall optical length becomes large, which is unsuitable for compactness. Preferably, the numerical range of conditional expression (9) is set as shown in the following conditional expression (9a) to achieve compactness of the entire optical system. More preferably, the numerical range of conditional expression (9) is set as shown in the following conditional expression (9b).

[0052] 0.30 <f3 / ft<0.80 …(9a) 0.45 <f3 / ft<0.60 …(9b) Conditional expression (10) defines a preferable range for the focal length of the third lens group L3 and the distance between the third lens group L3 and the rear lens group LR for inserting a reflecting member. Below the lower limit of conditional expression (10), the refractive power of the third lens group L3 becomes too strong, making it difficult to correct coma and astigmatism. Above the upper limit of conditional expression (10), the total optical length increases, making it unsuitable for compactness. Preferably, the numerical range of conditional expression (10) is set to satisfy conditional expression (10a) below, in order to achieve a good balance between the aberration correction and the compactness of the optical system. More preferably, the numerical range of conditional expression (10) is set to satisfy conditional expression (10b) below.

[0053] 0.30 <f3 / min(D3R)<1.35 …(10a) 0.54 <f3 / min(D3R)<1.30 …(10b) Conditional expression (11) defines a preferable range that should be satisfied throughout the entire zoom range for the distance D3R between the third lens group L3 and the rear lens group LR and the distance Dtotal along the optical axis from the optical surface closest to the object to the optical surface closest to the image in the optical system 101. Below the lower limit of conditional expression (11), the distance between the third lens group L3 and the rear lens group LR becomes too narrow, making it impossible to obtain the base length necessary for natural stereoscopic vision. On the other hand, above the upper limit of conditional expression (11), the optical path bending section becomes too long relative to the overall length of the optical system 101, making it difficult to achieve a compact optical system. Preferably, the numerical range of conditional expression (11) is set to satisfy the following conditional expression (11a) in order to achieve a good balance between the three-dimensional effect and the compactness of the optical system. More preferably, the numerical range of conditional expression (11) is set to satisfy the following conditional expression (11b).

[0054] 0.25 <min(D3R) / Max(Dtotal)<0.70 …(11a) 0.31 <min(D3R) / Max(Dtotal)<0.57 …(11b) Conditional expression (12) defines a preferable range for the focal length of the third lens group L3. Below the lower limit of conditional expression (12), the off-axial light beam is angled too much in the third lens group L3, resulting in a large diameter of the lens in the rear lens group LR. On the other hand, above the upper limit of conditional expression (12), the refractive power of the third lens group L3 becomes too weak, the distance between the second lens group L2 and the third lens group L3 becomes large, and the diameter of the front lens becomes large. Furthermore, the overall optical length becomes large, which is unsuitable for compactness. Preferably, the numerical range of conditional expression (12) is set to satisfy the following conditional expression (12a) in order to compact the entire optical system. More preferably, the numerical range of conditional expression (12) is set to satisfy the following conditional expression (12b).

[0055] 0.80 <f3 / fw<2.50 …(12a) 1.25 <f3 / fw<1.67 …(12b) 8A and 8B are aberration diagrams of the optical system 101a in this embodiment when focused at infinity, with FIG. 8A showing the aberration diagram at the wide-angle end and FIG. 8B showing the aberration diagram at the telephoto end.

[0056] Next, an optical system 101b according to Example 3 will be described with reference to FIGS. 9 and 10. FIG. 9 is a cross-sectional view of the optical system 101b according to this example. This example differs from the previous examples in that the value of Dout / Din in conditional expression (1) is small, at 0.14, enabling the acquisition of a stereoscopic image with enhanced three-dimensionality. When increasing the distance between the first reflecting surface R1 and the second reflecting surface R2, it is preferable to use prisms rather than plane mirrors for the reflecting surfaces, as this facilitates aberration correction. FIGS. 10A and 10B are aberration diagrams of the optical system 101b according to this example when focused at infinity. FIG. 10A shows the aberration diagram at the wide-angle end, and FIG. 10B shows the aberration diagram at the telephoto end.

[0057] Next, an optical system 101c according to a fourth embodiment will be described with reference to Fig. 11 and Fig. 12. Fig. 11 is a cross-sectional view of the optical system 101c according to the fourth embodiment. This embodiment differs from the previous embodiments in that the reflecting surface is formed of a plane mirror.

[0058] 12A and 12B are aberration diagrams of the optical system 101c in this embodiment when focused at infinity, with FIG. 12A showing the aberration diagram at the wide-angle end and FIG. 12B showing the aberration diagram at the telephoto end.

[0059] Numerical Examples 1 to 4 corresponding to Examples 1 to 4, respectively, are shown below. In each numerical example, the surface number indicates the order of the optical surfaces when counted from the object side. r is the radius of curvature of the ith optical surface (i-th surface) counted from the object side (i is a natural number), and d is the distance between the ith surface and the (i+1)th surface. nd and vd are the refractive index and Abbe number of the lens with respect to the d-line. The Abbe number vd of a certain material is given by Nd, NF, and NC, respectively, when the refractive indexes at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines are Nd, NF, and NC, respectively. νd=(Nd-1) / (NF-NC) It is expressed as:

[0060] In each numerical example, d, focal length f (mm), F-number Fno, and half angle of view (degrees) are all values ​​when the optical system of each example is focused on an object at infinity. BF (back focus) is the distance on the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image plane, expressed as an air-equivalent length. The total lens length is the distance on the optical axis from the forefront lens surface (the lens surface closest to the object) to the final lens surface plus the back focus BF. The lens group is not limited to cases where it is composed of multiple lenses, but may also be composed of a single lens.

[0061] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 61.533 1.00 1.85478 24.8 36.92 2 41.300 0.30 36.00 3 43.262 2.96 1.69680 55.5 36.00 4 91.486 0.10 35.74 5 66.448 3.23 1.59522 67.7 35.52 6 -18590.409 (variable) 35.21 7 17.356 1.00 1.80400 46.5 16.73 8 14.610 2.32 15.61 9 708.342 1.00 1.80400 46.5 15.53 10 13.667 1.96 1.80810 22.8 14.24 11 33.241 3.45 13.93 12 -20.964 0.84 1.88300 40.8 13.20 13 -32.689 0.00 13.31 14 67.508 1.13 1.90525 35.0 13.10 15 108.263 (variable) 12.90 16 (Aperture) ∞ 1.32 7.65 17 ∞ 10.00 1.51633 64.1 20.00 18 ∞ 10.00 1.51633 64.1 28.00 19 ∞ 1.00 20.00 20 ∞ 10.00 1.51633 64.1 20.00 21 ∞ 10.00 1.51633 64.1 28.00 22 ∞ (variable) 20.00 23 32.482 2.44 1.53775 74.7 14.62 24 -33.960 0.10 14.71 25 16.125 3.15 1.43875 94.9 14.52 26 -40.802 1.03 1.85478 24.8 14.25 27 97.774 5.37 13.90 28 26.279 2.95 1.72047 34.7 12.61 29 -14.430 0.82 1.69680 55.5 12.34 30 11.440 2.59 11.06 31 -14.957 0.78 1.88300 40.8 11.07 32 -19.637 1.40 11.51 33 53.143 0.78 1.91650 31.6 12.32 34 17.979 2.05 1.68893 31.1 12.38 35 -79.431 (variable) 12.49 Image plane ∞ Various data Zoom ratio 2.78 Wide-angle Mid-range Telephoto Focal length 28.80 41.71 79.99 F-number 5.60 5.60 5.59 Half angle of view 16.90 11.85 6.24 Image height 8.75 8.75 8.75 Lens total length 140.00 153.36 158.68 BF 33.27 33.27 33.27 d 6 1.00 19.07 38.36 d15 19.68 14.97 1.00 d22 1.00 1.00 1.00 d35 33.27 33.27 33.27 Entrance pupil position 29.98 67.68 116.41 Exit pupil position -69.27 -69.27 -69.27 Front principal point position 50.69 92.42 134.00 Back principal point position 4.47 -8.45 -46.73 Zoom lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position L1 1 93.38 7.59 0.66 -4.07 L2 7 -24.77 11.69 5.17 -3.90 LM 16 ∞ 0.32 14.35 -14.35 LR 23 32.82 23.46 -10.57 -23.42 Single lens data Lens starting surface focal length 1 1 -150.36 2 3 114.89 3 5 111.25 4 7 -137.15 5 9 -17.34 6 10 27.49 7 12 -68.49 8 14 195.53 9 17 0.00 10 18 0.00 11 20 0.00 12 21 0.00 13 23 31.17 14 25 26.79 15 26 -33.56 16 28 13.33 17 29 -9.04 18 31 -77.08 19 33 -29.97 20 34 21.46 [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 55.290 1.00 1.80810 22.8 32.98 2 36.349 0.37 32.10 3 38.952 5.05 1.59522 67.7 32.10 4 -161.885 0.10 31.86 5 25.530 4.57 1.43875 94.7 28.60 6 159.630 (variable) 27.94 7 164.950 1.00 1.85026 32.3 15.72 8 13.433 3.11 13.77 9 -21.804 1.00 1.51633 64.1 13.73 10 17.581 2.41 1.80810 22.8 13.75 11 -75.114 0.85 13.65 12 -22.345 0.84 1.72916 54.7 13.62 13 -70.712 (variable) 13.70 14 54.947 2.74 1.73400 51.5 12.90 15 -13.889 1.01 1.89190 37.1 12.79 16 -35.761 (variable) 12.73 17 (Aperture) ∞ 1.32 12.07 18 ∞ 12.00 1.51633 64.1 23.00 19 ∞ 20.00 1.51633 64.1 25.00 20 ∞ 12.00 1.51633 64.1 25.00 21 ∞ (variable) 23.00 22 26.982 2.42 1.53775 74.7 14.03 23 -35.836 0.10 14.06 24 27.834 2.65 1.43875 94.7 13.80 25 -23.912 1.03 1.85478 24.8 13.58 26 3121.471 (variable) 13.45 27 41.313 2.59 1.74000 28.3 13.33 28 -17.992 0.82 1.70154 41.2 13.16 29 14.792 2.34 12.36 30 -22.095 0.78 1.69680 55.5 12.39 31 -83.146 (variable) 12.93 32 40.512 0.78 1.91650 31.6 14.27 33 26.938 2.04 1.79360 37.1 14.38 34 -71.942 (variable) 14.49 Image plane ∞ Various data Zoom ratio 2.78 Wide-angle Mid-range Telephoto Focal length 28.80 41.08 80.00 F-number 3.98 3.98 4.00 Half angle of view 16.90 12.02 6.24 Image height 8.75 8.75 8.75 Lens total length 135.00 135.00 134.99 BF 27.91 28.23 28.90 d 6 0.93 6.56 13.43 d13 14.46 10.45 1.00 d16 3.45 1.81 4.37 d21 0.30 0.30 0.50 d26 0.97 1.32 0.47 d31 2.06 1.39 1.39 d34 27.91 28.23 28.90 Entrance pupil position 28.49 45.47 81.51 Exit pupil position -84.09 -76.87 -77.86 Front principal point position 49.89 70.50 101.56 Back principal point position -0.89 -12.85 -51.10 Zoom lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position L1 1 39.12 11.09 2.72 -4.69 L2 7 -12.32 9.20 1.59 -5.06 L3 14 37.57 3.75 1.32 -0.84 LM 17 ∞ 5.32 15.17 -15.17 LRA 22 29.20 6.21 -0.31 -4.25 LRB 27 -20.32 6.53 3.86 -1.03 LRC 32 34.72 2.83 0.53 -1.04 Single lens data Lens starting surface focal length 1 1 -134.48 2 3 53.25 3 5 68.55 4 7 -17.25 5 9 -18.69 6 10 17.84 7 12 -45.13 8 14 15.36 9 15 -26.03 10 18 0.00 11 19 0.00 12 20 0.00 13 22 29.02 14 24 29.78 15 25 -27.76 16 27 17.26 17 28 -11.45 18 30 -43.41 19 32 -90.21 20 33 24.92 [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 ∞ 1.00 34.20 2 50.774 1.00 1.80810 22.8 33.36 3 35.103 3.13 32.44 4 50.401 4.04 1.59522 67.7 32.52 5 -238.185 0.10 32.34 6 28.709 5.40 1.43875 94.7 30.13 7 -335.318 (variable) 29.59 8 891.959 1.00 1.85026 32.3 16.60 9 15.061 3.45 14.78 10 -19.903 1.00 1.51633 64.1 14.75 11 20.707 2.50 1.80810 22.8 15.19 12 -80.461 0.78 15.17 13 -28.235 0.84 1.72916 54.7 15.15 14 -46.634 (variable) 15.29 15 71.305 2.88 1.73400 51.5 14.39 16 -15.739 1.00 1.89190 37.1 14.30 17 -39.124 (variable) 14.27 18 (Aperture) ∞ 1.32 13.45 19 ∞ 7.00 1.51633 64.1 13.27 20 ∞ -55.00 18.76 21∞7.00 19.10 22 ∞ (variable) 16.49 23 27.814 3.10 1.53775 74.7 17.08 24 -38.441 0.10 17.07 25 29.313 3.26 1.43875 94.7 16.44 26 -25.951 1.03 1.85478 24.8 16.14 27 1712.494 (variable) 15.84 28 40.391 2.97 1.74000 28.3 15.36 29 -20.626 0.82 1.70154 41.2 15.12 30 14.724 3.01 13.83 31 -21.090 0.78 1.69680 55.5 13.85 32 -86.303 (variable) 14.48 33 39.734 0.78 1.91650 31.6 16.61 34 40.004 1.95 1.79360 37.1 16.65 35 -92.532 1.00 16.72 36 ∞ (variable) 16.76 Image plane ∞ Various data Zoom ratio 2.78 Wide-angle Mid-range Telephoto Focal length 28.80 35.08 80.00 F-number 3.99 3.95 4.00 Half angle of view 16.90 14.01 6.24 Image height 8.75 8.75 8.75 Lens length 165.90 165.91 165.89 BF 24.33 25.30 26.09 d 7 0.13 3.68 14.21 d14 18.18 14.44 1.10 d17 1.52 1.72 4.45 d22 0.46 0.30 0.30 d27 1.33 1.82 1.11 d32 2.70 1.39 1.39 d36 24.33 25.30 26.09 Entrance pupil position 29.32 37.47 77.59 Exit pupil position -248.12 -183.77 -180.41 Front principal point position 55.08 66.67 126.59 Back principal point position -4.47 -9.78 -53.91 Zoom lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position L1 1 41.63 14.67 7.45 -3.60 L2 8 -14.55 9.57 1.00 -6.26 L3 15 43.79 3.88 1.47 -0.76 LM 18 ∞ -39.68 23.41 -23.41 LRA 23 30.25 7.50 -0.32 -5.07 LRB 28 -19.53 7.58 4.57 -1.24 LRC 33 35.30 3.74 0.41 -2.10 Single lens data Lens starting surface focal length 1 1 -144.87 2 4 70.25 3 6 60.55 4 8 -18.03 5 10 -19.49 6 11 20.61 7 13 -100.07 8 15 17.82 9 16 -30.13 10 19 0.00 11 20 0.00 12 21 0.00 13 23 30.51 14 25 31.95 15 26 -29.90 16 28 18.84 17 29 -12.13 18 31 -40.25 19 33 2689.60 20 34 35.42 [Numerical Example 4] Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 ∞ 0.10 34.00 2 50.402 1.92 1.80810 22.8 33.35 3 35.017 4.14 32.08 4 61.018 3.60 1.59522 67.7 32.15 5 -198.013 0.10 32.00 6 27.196 5.68 1.43875 94.7 29.92 7 -272.077 (variable) 29.40 8 -355.440 1.00 1.85026 32.3 16.42 9 15.895 3.19 14.72 10 -22.643 1.00 1.51633 64.1 14.69 11 20.214 2.59 1.80810 22.8 15.01 12 -80.071 0.76 14.97 13 -29.267 0.84 1.72916 54.7 14.93 14 -57.323 (variable) 15.03 15 60.994 3.23 1.73400 51.5 13.88 16 -15.526 0.97 1.89190 37.1 13.72 17 -41.517 (variable) 13.64 18 (Aperture) ∞ 11.32 13.36 19 ∞ 15.00 12.96 20 ∞ (variable) 12.42 21 27.859 2.49 1.53775 74.7 13.96 22 -38.892 0.10 13.98 23 25.863 2.81 1.43875 94.7 13.70 24 -27.911 1.03 1.85478 24.8 13.41 25 771.990 (variable) 13.21 26 38.655 2.80 1.74000 28.3 12.90 27 -19.882 0.82 1.70154 41.2 12.60 28 13.777 3.68 11.76 29 -20.635 0.78 1.69680 55.5 12.06 30 -69.361 (variable) 12.57 31 40.925 0.78 1.91650 31.6 13.71 32 38.915 1.54 1.79360 37.1 13.78 33 -134.889 (variable) 13.87 Image plane ∞ Various data Zoom ratio 2.78 Wide-angle Mid-range Telephoto Focal length 28.80 41.37 80.00 F-number 3.97 3.94 4.00 Half angle of view 16.90 11.94 6.24 Image height 8.75 8.75 8.75 Lens total length 129.86 129.86 129.85 BF 26.18 25.45 27.41 d 7 0.20 6.54 14.11 d14 18.94 12.70 1.27 d17 2.12 2.02 5.87 d20 7.59 7.34 6.24 d25 1.09 2.14 1.28 d30 1.47 1.39 1.39 d33 26.18 25.45 27.41 Entrance pupil position 30.50 46.85 80.47 Exit pupil position -66.14 -64.92 -61.63 Front principal point position 50.31 69.29 88.59 Back principal point position -2.62 -15.92 -52.59 Zoom lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position L1 1 41.89 15.55 8.06 -3.59 L2 8 -14.75 9.37 0.96 -6.02 L3 15 43.35 4.20 1.40 -1.02 LM 18 ∞ 26.32 13.16 -13.16 LRA 21 28.43 6.42 -0.18 -4.27 LRB 26 -18.97 8.08 4.62 -1.72 LRC 31 40.00 2.33 0.25 -1.03 Single lens data Lens starting surface focal length 1 1 -150.36 2 4 78.77 3 6 56.68 4 8 -17.87 5 10 -20.52 6 11 20.21 7 13 -83.05 8 15 17.17 9 16 -28.30 10 21 30.58 11 23 31.09 12 24 -31.49 13 26 18.11 14 27 -11.48 15 29 -42.43 16 31 -1062.67 17 32 38.21 Table 1 shows the upper and lower limits of conditional expressions (1) to (12) and the numerical values ​​for each embodiment. However, since embodiment 1 does not have the third lens unit L3, the rear A lens unit LRA, and the rear B lens unit LRB, hyphens (-) are used for conditional expressions (8) to (12).

[0062] [Table 1]

[0063] Next, with reference to FIG. 13 , an imaging device (digital still camera) 200 using the optical system 101 (101a, 101b, 101c) of each embodiment as an imaging optical system 220 will be described. FIG. 13 is a schematic diagram of the imaging device 200 equipped with the optical system of each embodiment. The imaging device 200 includes a camera body 250 having an image sensor 260 and a lens apparatus 210 equipped with an imaging optical system 220 corresponding to any of the optical systems of Embodiments 1 to 4. The lens apparatus 210 and the camera body 250 may be configured integrally or detachably. Note that FIG. 13 shows only one optical system because two optical systems are arranged side by side in the depth direction. Since the imaging device 200 includes the lens apparatus 210 as a variable magnification telephoto lens, it is compact yet has a large baseline length and is capable of stereoscopic imaging. Note that the optical systems of each embodiment are not limited to the digital still camera shown in FIG. 13 , but can also be applied to various imaging devices such as broadcast cameras, silver halide film cameras, and surveillance cameras.

[0064] According to each embodiment, it is possible to provide a lens device and an imaging device that are small, have a long base line length, and are capable of acquiring a stereoscopic image with a natural three-dimensional effect for a distant object. Furthermore, according to each embodiment, it is possible to reduce the relative displacement between the two reflecting surfaces that bend the optical path, thereby enabling high image quality.

[0065] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0066] 100 Imaging optical system (lens device) 101, 102 Optical system L1 First lens group L2 Second lens group R1 1st reflective surface R2 2nd reflective surface

Claims

1. It has two optical systems, Each of the two optical systems has, arranged in order from the object side to the image side, a first lens group having positive refractive power, a second lens group having negative refractive power, a first reflecting surface, a second reflecting surface, and a rear lens group having positive refractive power; During magnification, at least the distance between the first lens group and the second lens group and the distance between the second lens group and the first reflecting surface are changed, When the distance between the vertices of the lenses located closest to the object side in the two optical systems is Din and the distance between the vertices of the lenses located closest to the image side in the two optical systems is Dout, 0.05<Dout / Din<0.50 A lens device characterized by satisfying the following conditional expressions:

2. 2. The lens device according to claim 1, wherein the first reflecting surface and the second reflecting surface are held by an integral lens barrel.

3. 3. The lens apparatus according to claim 1, further comprising an aperture stop between the second lens group and the first reflecting surface.

4. 4. The lens device according to claim 1, further comprising a third lens group having a positive refractive power between the second lens group and the first reflecting surface.

5. When the focal length of the third lens group is f3 and the focal length of the optical system at the telephoto end is ft, 0.20<f3 / ft<1.00 5. The lens device according to claim 4, wherein the following condition is satisfied:

6. When the focal length of the third lens group is f3, the distance along the optical axis between the third lens group and the rear lens group is D3R, and the minimum value of D3R during zooming is min(D3R), 0.20<f3 / min(D3R)<1.40 6. The lens device according to claim 4, wherein the following condition is satisfied:

7. Let D3R be the distance along the optical axis between the third lens group and the rear lens group, min(D3R) be the minimum value of D3R during zooming, Dtotal be the distance along the optical axis from the optical surface of the lens device closest to the object to the optical surface closest to the image, and Max(Dtotal) be the maximum value of Dtotal during zooming. 0.20<min(D3R) / Max(Dtotal)<0.80 7. The lens device according to claim 4, wherein the following condition is satisfied:

8. When the focal length of the third lens group is f3 and the focal length of the optical system at the wide-angle end is fw, 0.60<f3 / fw<3.00 8. The lens device according to claim 4, wherein the following condition is satisfied:

9. 9. The lens device according to claim 4, wherein the third lens group includes one lens with positive refractive power and one lens with negative refractive power.

10. 10. The lens device according to claim 1, wherein the first reflecting surface and the second reflecting surface are reflecting surfaces of an optical member that is integrally molded.

11. When a composite focal length of the first lens group and the second lens group at the wide-angle end is f12w and a focal length of the optical system at the wide-angle end is fw, -1.60<f12w / fw<-0.50 11. The lens device according to claim 1, wherein the following condition is satisfied:

12. When the distance along the optical axis from the first reflecting surface to the second reflecting surface is defined as DRR, 0.25<DRR / Din<0.49 10. The lens device according to claim 1, wherein the following condition is satisfied:

13. When the focal length of the first lens group is f1 and the focal length of the optical system at the wide-angle end is fw, 0.50<f1 / fw<5.00 13. The lens device according to claim 1, wherein the following condition is satisfied:

14. When the focal length of the second lens group is f2 and the focal length of the optical system at the wide-angle end is fw, -2.00<f2 / fw<-0.10 14. The lens device according to claim 1, wherein the following condition is satisfied:

15. When the focal length of the rear lens group is fR and the focal length of the optical system at the wide-angle end is fw, 0.50<fR / fw<5.00 15. The lens device according to claim 1, wherein the following condition is satisfied:

16. When the effective diameter of the lens arranged closest to the image side in the optical system is Φout, 1.00<Dout / Φout<3.00 16. The lens device according to claim 1, wherein the following condition is satisfied:

17. 17. The lens device according to claim 1, wherein the rear lens group does not move during zooming.

18. 18. The lens device according to claim 1, wherein the first lens group includes one meniscus lens having a negative refractive power and a convex surface facing the object side, and two lenses having a positive refractive power.

19. 19. The lens device according to claim 1, wherein the second lens group has two lenses with negative refractive power and one lens with positive refractive power.

20. The rear lens group is a rear B lens group movable in a direction perpendicular to the optical axis for image stabilization; 20. The lens device according to claim 1, wherein a lens in the rear lens group that is closer to the object than the rear B lens group is a rear A lens group, and a lens in the rear lens group that is closer to the image than the rear B lens group is a rear C lens group, the lens device having at least one of the rear A lens group or the rear C lens group.

21. When the focal length of the rear A lens group is fRA and the focal length of the rear B lens group is fRB, 1.00<|fRA / fRB|<2.00 21. The lens device according to claim 20, wherein the following condition is satisfied:

22. When the angle of incidence of an axial chief ray on the first reflecting surface and the second reflecting surface is α (°), ２０＜α＜５０ 22. The lens device according to claim 1, wherein the following condition is satisfied:

23. 23. The lens apparatus according to claim 1, further comprising a field stop at least one of the first lens group on the object side and the rear lens group on the image side.

24. 24. An imaging device comprising: a lens device according to claim 1; and an imaging element that captures an optical image formed by the lens device.

Images