Optical system and imaging apparatus

Abstract

To provide a compact optical system that can perform stereoscopic imaging more properly.SOLUTION: An optical system includes a first optical system (OS1) that forms an optical image of a subject in a first imaging area (IC1), and a second optical system (OS2) that is disposed in parallel with the first optical system and forms an optical image of the subject in a second imaging area (IC2). Each of the first optical system and the second optical system includes an aperture diaphragm (SP) fixed in an optical axis direction relative to a position of an image surface (IP), and a lens group (LM) that is disposed closer to the image surface than the aperture diaphragm and movable in the optical axis direction. When a diameter of the aperture diaphragm for determining an on-axis luminous flux of each of the first optical system and the second optical system is Φs and a distance between the first optical system and the second optical system is DL, the following inequality is satisfied: 0.25<Φs / DL<0.90.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to an optical system and an imaging device. [Background technology]

[0002] Patent Document 1 discloses a stereoscopic imaging optical system that uses two optical systems arranged in parallel to each other to form two optical images side by side on a single imaging element in order to capture realistic images such as virtual reality images. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-3022 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the stereoscopic imaging optical system disclosed in Patent Document 1, the two optical systems arranged in parallel to each other are fixed in focus during focusing, and therefore the aperture value (F-number) is large, making it difficult to obtain a blurred image, and the optical system is not suitable for stereoscopic video shooting.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a compact optical system capable of more appropriately performing stereoscopic photography. [Means for solving the problem]

[0006] An optical system according to one aspect of the present invention includes a first optical system that forms an optical image of an object in a first imaging region, and a second optical system that is arranged in parallel with the first optical system and forms an optical image of the object in a second imaging region, the first optical system and the second optical system each having an aperture stop that is fixed in an optical axis direction with respect to a position of an image plane, and a lens group that is arranged closer to the image plane than the aperture stop and is movable in the optical axis direction, wherein Φs is a diameter of the aperture stop that determines an axial light beam of each of the first optical system and the second optical system, and DL is a distance between the first optical system and the second optical system, 0.25<Φs / DL<0.90 The following condition is satisfied.

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

[0008] According to the present invention, it is possible to provide a small-sized optical system capable of performing stereoscopic photography more appropriately. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a cross-sectional view of an optical system in the first embodiment. [Diagram 2] 4A to 4C are aberration diagrams of the optical system in Example 1. [Diagram 3] FIG. 11 is a cross-sectional view of an optical system in Example 2. [Figure 4] 11A to 11C are aberration diagrams of the optical system in Example 2. [Diagram 5] FIG. 11 is a cross-sectional view of an optical system according to a third embodiment. [Figure 6] 11A to 11C are aberration diagrams of the optical system in Example 3. [Figure 7] FIG. 11 is a cross-sectional view of an optical system in Example 4. [Figure 8] 11A to 11C are aberration diagrams of the optical system in Example 4. [Figure 9] FIG. 2 is a cross-sectional view of a lens device including two optical systems in each embodiment. [Figure 10]3A and 3B are schematic diagrams of an image circle on an image sensor in each embodiment. [Figure 11] FIG. 2 is a schematic diagram of an imaging device in each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0011] The optical system of each embodiment is a stereoscopic imaging optical system in which two optical systems are arranged in parallel with one imaging element to obtain a stereoscopically visible image. FIG. 9 is a cross-sectional view of a lens device (optical system) LA including an optical system (first optical system) OS1 and an optical system (second optical system) OS2 in each embodiment. As shown in FIG. 9, the lens device LA of each embodiment has two optical systems OS1 and OS2, which are arranged in parallel with respect to the imaging surface (image surface IP) of the imaging element. The optical systems OA1 and OA2 are arranged apart by a distance (baseline length) DL between the optical axis OA1 of the optical system OS1 and the optical axis OA2 of the optical system OS2. The two optical systems OS1 and OS2 are held by a housing not shown.

[0012] FIG. 10 is a schematic diagram of an image circle formed on an image sensor 12, and shows a state in which light rays incident on two optical systems OS1 and OS2 are imaged into image circles IC1 and IC2 of the two optical systems OS1 and OS2 within one image sensor 12. As shown in FIG. 10, an image circle (first imaging region) IC1 corresponding to the optical system OS1 and an image circle (second imaging region) IC2 corresponding to the optical system OS2 are arranged in parallel on the imaging surface of one image sensor 12. An image (optical image) is formed on an image surface IP of the image sensor 12 by the optical systems OS1 and OS2. That is, in the lens device LA of each embodiment, two optical images by the two optical systems OS1 and OS2 are formed on one image sensor 12.

[0013] Next, the optical system of each embodiment will be described. Fig. 1, Fig. 3, Fig. 5, and Fig. 7 are cross-sectional views of the optical system (one of the first optical system or the second optical system) of each embodiment 1 to 4. In each cross-sectional view, the left side is the object side (front) and the right side is the image side (rear). The optical system of each embodiment is configured with a plurality of lens groups. The lens group may be configured with one lens or may be configured with a plurality of lenses. The lens group may also include an aperture stop.

[0014] In each cross-sectional view, SP is an aperture stop. FP is a flare cut stop, which cuts out unnecessary light. IP is an image plane. When the optical system of each embodiment is used as an imaging optical system for a digital still camera or digital video camera, the imaging surface of a photoelectric conversion element such as a CCD sensor or a CMOS sensor is disposed on the image plane IP. When the optical system of each embodiment is used as an imaging optical system for a silver halide film camera, a photosensitive surface equivalent to a film surface is disposed on the image plane IP. In the optical system of each embodiment, an optical block (not shown) equivalent to an optical filter, a face plate, a low-pass filter, an infrared cut filter, or the like may be disposed on the object side of the image plane IP.

[0015] 2, 4, 6, and 8 are aberration diagrams of the optical systems of Examples 1 to 4 when focused at infinity. In the spherical aberration diagrams, Fno is the F-number, and shows the amount of spherical aberration for the d-line (wavelength 587.6 nm) and the g-line (wavelength 435.8 nm). In the astigmatism diagrams, ΔS shows the amount of astigmatism in the sagittal image plane, and ΔM shows the amount of astigmatism in the meridional image plane. In the distortion diagrams, the amount of distortion for the d-line is shown. In the chromatic aberration diagrams, the amount of chromatic aberration for the g-line is shown. ω is the half image angle (°).

[0016] The optical system of each embodiment is an example of a case where an imaging element having a base length of 11.7 mm, a short side length of 15 mm, and a long side length of 22.4 mm is used. The image circle diameter of each optical system is set to 9.7 mm, and a 2 mm interval is set between the image circles of the two optical systems (the first optical system and the second optical system). In this case, the surface vertex interval of the lens surfaces of the two optical systems is 11.7 mm. The image circle of each optical system is 0.5 mm away from the short side of the imaging element 12. This makes it possible for the lens device 11 of each embodiment to accommodate the image circle within one imaging element 12. Note that the optical system of each embodiment assumes an imaging element 12 having a short side length of 15 mm and a long side length of 22.4 mm, which is generally used in interchangeable lens cameras, but is not limited to this and can be applied to cameras with imaging elements of various sizes. The interval between the two image circles can also be set arbitrarily. Further, the optical system in each embodiment employs a central projection system, but various projection systems may be employed, such as a conformal projection system, a conformal solid angle projection system, or a stereoscopic projection system.

[0017] Next, the characteristic configuration of the optical system of each embodiment will be described. The optical system of each embodiment has, arranged in order from the object side to the image side, a first lens group (front group) with negative refractive power, an aperture stop SP, and a second lens group (rear group) with positive refractive power. Overall, the optical system is a so-called retrofocus type refractive power arrangement consisting of a front group with negative refractive power and a rear group with positive refractive power, which realizes a small size and a wide angle of view.

[0018] In order to experience a realistic stereoscopic image, the optical system of each embodiment is provided with a large-diameter lens that is expected to have an effect on the stereoscopic image by visual blur. In general, when a large-diameter lens is used, the optical system tends to become larger. In addition, when a large-diameter lens is used, the focal depth becomes narrow, so focus accuracy according to the shooting distance of the subject is required. For this reason, the optical system of each embodiment has a lens group (intermediate lens group) LM that moves to the image plane IP side of the aperture stop SP so as to align the two image plane positions. This makes it possible to align the left and right image plane position deviations caused by manufacturing variations, and also makes it possible to correct the difference in vision between the left and right eyes for each individual.

[0019] Furthermore, the aperture stop SP in the optical system of each embodiment is not incorporated into the intermediate lens group, but is arranged at a fixed position in the direction along the optical axis OA (optical axis direction) with respect to the image plane IP. This makes it possible to separately arrange the driver for the variable aperture stop SP and the driver for the intermediate lens group that moves on the optical axis OA, even with a large diameter lens, thereby realizing a small and lightweight imaging device.

[0020] In addition, the optical system of each embodiment is an overall focus type in which the entire optical system is moved in the optical axis direction when focusing from infinity to a close distance, or an inner focus type in which some lenses of the optical system are moved in the optical axis direction. In the optical system of each embodiment, the lens group LM can be used as a focus group that moves in the optical axis direction when focusing from infinity to a close distance, rather than as an intermediate lens group. By using the intermediate lens group and the focus group together, it is possible to realize a small and lightweight imaging device.

[0021] When the diameter of the aperture stop SP that determines the axial light beam of each of the first optical system (optical system OA1) and the second optical system (optical system OA2) is Φs and the distance (baseline length) between the optical axis OA1 of the first optical system and the optical axis OA2 of the second optical system is DL, the following conditional formula (1) is satisfied.

[0022] 0.25<Φs / DL<0.90 (1) Conditional formula (1) specifies the ratio between the diameter of the aperture stop SP that determines the axial light beam of each of the first and second optical systems and the distance (baseline length) between the first and second optical systems. If the lower limit of conditional formula (1) is exceeded, the diameter Φs of the aperture stop SP of each of the first and second optical systems becomes small, the F-number becomes too large, and it becomes difficult to obtain a blurred image. As a result, the visual blur effect of the image obtained by the two optical systems becomes small, and a three-dimensional effect cannot be obtained. On the other hand, if the upper limit of conditional formula (1) is exceeded, the diameter Φs of the aperture stop SP of each of the first and second optical systems becomes too large, the optical systems of each embodiment become large, and there is a possibility that interference between adjacent lenses occurs.

[0023] Preferably, the numerical range of conditional expression (1) is set as shown in the following conditional expression (1a).

[0024] 0.30<Φs / DL<0.80 (1a) More preferably, the numerical range of conditional expression (1) is set as shown in the following conditional expression (1b).

[0025] 0.35<Φs / DL<0.60 (1b) With the above configuration, it is possible to provide a small, lightweight, high-performance optical system capable of stereoscopic imaging, which uses one image sensor to perform imaging using two optical systems.

[0026] Next, the conditions and configurations that are preferably satisfied by the optical system of each embodiment will be described. The following preferred conditions and configurations may be satisfied by at least one of the two optical systems. More preferably, the two optical systems are configured identically, so that the following preferred conditions and configurations are satisfied by both of the two optical systems.

[0027] Also, the distance on the optical axis from the aperture stop SP to the image plane IP is defined as Ls, and the distance on the optical axis from the front surface (the surface closest to the object) of the lens group LM (the intermediate lens group or the focus group) when focusing at infinity to the image plane IP is defined as Lm. In this case, it is preferable that the optical system of each embodiment satisfies the following conditional expression (2).

[0028] 0.40 <Lm / Ls<0.90 ···(2) Conditional formula (2) is a conditional formula regarding the arrangement of the aperture stop SP and the lens group LM. If the lower limit of conditional formula (2) is not satisfied, the distance between the aperture stop SP and the lens group LM increases, so that the lens group LM becomes large. On the other hand, if the upper limit of conditional formula (2) is exceeded, the distance between the aperture stop SP and the lens group LM decreases, so that there is a possibility that the driving devices that mechanically operate each of them may interfere with each other.

[0029] More preferably, the numerical range of conditional expression (2) is set as shown in the following conditional expression (2a).

[0030] 0.50 <Lm / Ls<0.80 ···(2a) More preferably, the numerical range of conditional expression (2) is set as in the following conditional expression (2b).

[0031] 0.60 <Lm / Ls<0.75 ···(2b) In the optical system of each embodiment, it is preferable that the following conditional expression (3) be satisfied, where fm is the focal length of the lens group LM and f is the focal length of the optical system (entire system).

[0032] 1.2<|fm| / f<6.0 (3) Conditional formula (3) specifies the ratio between the focal length of the lens group LM and the focal length of the optical system. If the lower limit of conditional formula (3) is exceeded, the refractive power of the lens group becomes strong, so that the position sensitivity of the lens group LM (the ratio between the amount of movement of the lens group LM and the amount of change in the back focus associated with the movement) becomes large, making it difficult to align the left and right image plane position shifts. On the other hand, if the upper limit of conditional formula (3) is exceeded, the refractive power of the lens group LM becomes weak, so that the position sensitivity of the lens group LM (the ratio between the amount of movement of the lens group LM and the amount of change in the back focus associated with the movement) becomes small, and the amount of movement of the lens group LM increases. As a result, the optical system becomes large, which is undesirable.

[0033] More preferably, the numerical range of conditional expression (3) is set as in the following conditional expression (3a).

[0034] 1.6<|fm| / f<5.0 (3a) More preferably, the numerical range of conditional expression (3) is set as in the following conditional expression (3b).

[0035] 2.0<|fm| / f<4.5 (3b) In the optical system of each embodiment, it is preferable that the lens group LM has a negative refractive power. This allows the lens group LM to have a small diameter and a small overall length, and thus to be lightweight. As a result, the drive device that moves the lens group LM during focusing can be simplified, and miniaturization can be facilitated. In addition, by appropriately setting the refractive power of the lens group LM as a focus group, it is possible to achieve a balance between suppression of aberration fluctuations accompanying changes in object distance and appropriate focus sensitivity.

[0036] In the optical system of each embodiment, it is preferable that the lens group LM has a negative meniscus lens with a convex surface facing the object side, which can reduce aberration fluctuations (especially spherical aberration) when the lens group LM moves along the optical axis.

[0037] In the optical system of each embodiment, it is preferable that the lens group LM is composed of one lens. This allows the lens group LM to be further lightened, simplifying the drive device that moves the lens group during focusing, and making it easier to make the lens group more compact. In addition, by appropriately setting the curvature of the lens surface of the lens group LM as a focus group, the image surface characteristics at close range can be improved.

[0038] In the optical system of each embodiment, when the distance on the optical axis from the aperture stop SP to the image plane IP is Ls and the distance on the optical axis from the lens surface closest to the object to the image plane IP is LT, it is preferable that the following conditional expression (4) is satisfied:

[0039] 0.50 <Ls / LT<0.80 ···(4) Conditional formula (6) specifies the ratio of the distance on the optical axis from the aperture stop SP to the image plane IP to the total length of the optical system. As shown in FIG. 10, in order to form the image circles IC1 and IC2 of the two optical systems on one image sensor 12, the lenses arranged in parallel need to be arranged close to each other. If the lower limit of conditional formula (4) is not satisfied, the aperture stop SP is arranged too close to the image side, so that the lens diameter on the object side increases, which may increase the weight and cause interference with adjacent lenses. On the other hand, if the upper limit of conditional formula (4) is exceeded, the aperture stop SP is arranged too close to the object side, so that the lens diameter on the image side increases, which may cause interference with adjacent lenses.

[0040] More preferably, the numerical range of conditional expression (4) is set as in the following conditional expression (4a).

[0041] 0.55 <Ls / LT<0.75 ···(4a) More preferably, the numerical range of conditional expression (4) is set as in the following conditional expression (4b).

[0042] 0.60 <Ls / LT<0.70 ···(4b) It is preferable that the optical system of each embodiment satisfies the following conditional expression (5), where LT is the distance on the optical axis from the lens surface closest to the object to the image plane IP and f is the focal length of the optical system (entire system).

[0043] 4.0 <LT / f<10.0 ···(5) Conditional formula (5) defines the ratio between the total optical length and the focal length of the optical system. If the lower limit of conditional formula (5) is exceeded, the total optical length becomes short, and the distance between the aperture stop SP and the lens group LM becomes short, which may cause interference between the drive devices that mechanically operate each of them. On the other hand, if the upper limit of conditional formula (5) is exceeded, the total optical length becomes large, which is undesirable because it increases the size of the optical system.

[0044] More preferably, the numerical range of conditional expression (5) is set as in the following conditional expression (5a).

[0045] 5.0 <LT / f<8.0 ···(5a) More preferably, the numerical range of conditional expression (5) is set as in the following conditional expression (5b).

[0046] 6.0 <LT / f<7.0 ···(5b) In the optical system of each embodiment, it is preferable to satisfy the following conditional expression (6), where fn is the focal length of the front group located on the object side of the aperture stop SP, and f is the focal length of the optical system (entire system).

[0047] 1.2<|fn| / f<15.0 (6) Conditional formula (6) defines the ratio between the focal length of the front group, which is located closer to the object side than the aperture stop SP, and the focal length of the optical system. If the lower limit of conditional formula (6) is not met, the refractive power of the front group will be too strong, making it difficult to satisfactorily correct various aberrations such as field curvature and astigmatism. On the other hand, if the upper limit of conditional formula (6) is exceeded, the refractive power of the front group will be too weak, increasing the overall optical length and the size of the optical system, which is undesirable.

[0048] More preferably, the numerical range of conditional expression (6) is set as in the following conditional expression (6a).

[0049] 2.0<|fn| / f<10.0 (6a) More preferably, the numerical range of conditional expression (6) is set as in the following conditional expression (6b).

[0050] 2.5<|fn| / f<8.0 (6b) In the optical system of each embodiment, it is preferable that the following conditional expression (7) is satisfied, where Φf is the effective diameter of the lens arranged closest to the object side, and Φr is the effective diameter of the lens arranged closest to the image plane side. Note that the effective diameter (effective area) is the diameter (area) through which effective light rays that contribute to image formation pass on the optical surface.

[0051] 0.80<Φf / Φr<1.20 (7) Conditional formula (7) defines the ratio between the effective diameter of the lens closest to the object and the effective diameter of the lens closest to the image. If the lower limit of conditional formula (7) is exceeded, the lens diameter on the object side increases, which may result in an increase in weight or interference with adjacent lenses. On the other hand, if the upper limit of conditional formula (7) is exceeded, the lens diameter on the image side increases, which may result in interference with adjacent lenses.

[0052] More preferably, the numerical range of conditional expression (7) is set as in the following conditional expression (7a).

[0053] 0.90<Φf / Φr<1.10 (7a) More preferably, the numerical range of conditional expression (7) is set as in the following conditional expression (7b).

[0054] 0.95<Φf / Φr<1.05 (7b) It is preferable that the optical system in each embodiment does not include a reflective optical element that has the function of bending the optical path, since incorporating a reflective optical element increases the weight, and therefore the optical system can be made small and lightweight.

[0055] In the optical system of each embodiment, the lens group LM that functions as the intermediate lens group may be provided in only one of the two optical systems. The left and right image plane position shift is possible by moving only one of the optical systems along the optical axis, and unnecessary driving mechanisms can be omitted, making the optical system compact and lightweight. EXAMPLES

[0056] The optical system of the first embodiment includes a first lens group (front group) L1 having a negative refractive power, an aperture stop SP, and a second lens group (rear group) L2 having a positive refractive power, which are arranged in this order from the object side to the image side. A flare cut stop FP for cutting unnecessary light is arranged between the aperture stop SP and the second lens group L2. The first lens group L1 is composed of, in order from the object side to the image side, a negative meniscus lens G1 with a convex surface facing the object side, a cemented lens of a biconcave lens G2 and a biconvex lens G3, a negative meniscus lens G4 with a convex surface facing the object side, and a biconvex lens G5. The second lens group L2 is composed of, in order from the object side to the image side, a positive meniscus lens G6 with a convex surface facing the image side, and a cemented lens of a biconvex lens G7 and a negative meniscus lens G8 with a convex surface facing the image side. In this embodiment, the positive meniscus lens G6 is a lens group LM that moves in the optical axis direction as an intermediate lens group or a focus group. EXAMPLES

[0057] The optical system of the second embodiment includes a first lens group (front group) L1 having a negative refractive power, an aperture stop SP, and a second lens group (rear group) L2 having a positive refractive power, which are arranged in this order from the object side to the image side. A flare cut stop FP for cutting unnecessary light is arranged between the aperture stop SP and the second lens group L2. The first lens group L1 includes, in order from the object side to the image side, a negative meniscus lens G1 with a convex surface facing the object side, a cemented lens of a biconcave lens G2 and a biconvex lens G3, a negative meniscus lens G4 with a convex surface facing the object side, and a positive meniscus lens G5 with a convex surface facing the image side. The second lens group L2 includes, in order from the object side, a biconvex lens G6, a negative meniscus lens G7 with a convex surface facing the object side, and a cemented lens of a biconvex lens G8 and a negative meniscus lens G9 with a convex surface facing the image side. In this embodiment, the negative meniscus lens G7 is a lens group LM that moves in the optical axis direction as an intermediate lens group or a focus group. EXAMPLES

[0058] The optical system of the third embodiment has a first lens group (front group) L1 having a negative refractive power, an aperture stop SP, and a second lens group (rear group) L2 having a positive refractive power, which are arranged in this order from the object side to the image side. A flare cut stop FP for cutting unnecessary light is arranged between the aperture stop SP and the second lens group L2. The first lens group L1 is composed of, in order from the object side, a negative meniscus lens G1 with a convex surface facing the object side, a cemented lens of a biconcave lens G2 and a biconvex lens G3, a negative meniscus lens G4 with a convex surface facing the object side, and a biconvex lens G5. The second lens group L2 is composed of, in order from the object side, a positive meniscus lens G6 with a convex surface facing the image side, and a cemented lens of a biconvex lens G7 and a negative meniscus lens G8 with a convex surface facing the image side. In this embodiment, the positive meniscus lens G6 is a lens group LM that moves in the optical axis direction as an intermediate lens group or a focus group. EXAMPLES

[0059] The optical system of the fourth embodiment has a first lens group (front group) L1 having a negative refractive power, an aperture stop SP, and a second lens group (rear group) L2 having a positive refractive power, which are arranged in this order from the object side to the image side. A flare cut stop FP for cutting unnecessary light is arranged between the aperture stop SP and the second lens group L2. The first lens group L1 is composed of, in order from the object side, a negative meniscus lens G1 with a convex surface facing the object side, a cemented lens of a biconcave lens G2 and a biconvex lens G3, a negative meniscus lens G4 with a convex surface facing the object side, and a positive meniscus lens G5 with a convex surface facing the image side. The second lens group L2 is composed of, in order from the object side, a biconvex lens G6, a negative meniscus lens G7 with a convex surface facing the object side, and a cemented lens of a biconvex lens G8 and a negative meniscus lens G9 with a convex surface facing the image side. In this embodiment, the negative meniscus lens G6 is a lens group LM that moves in the optical axis direction as an intermediate lens group or a focus group.

[0060] Numerical Examples 1 to 4 corresponding to Examples 1 to 4, respectively, are shown below. In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial distance (distance on the optical axis) between the mth surface and the (m+1)th surface. Here, m is the surface number counted from the light incidence side. In addition, nd represents the refractive index of each optical member with respect to the d-line, and νd represents the Abbe number of the optical member. Note that the Abbe number νd of a certain material is given by Nd, NF, and NC, respectively, when the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines are Nd, NF, and NC, respectively, νd=(Nd-1) / (NF-NC) It is expressed as:

[0061] In each numerical example, d, focal length (mm), F-number, and half angle of view (°) are all values ​​when the optical system of each example is focused on an object at infinity. "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 surface expressed as an air-equivalent length. "Total lens length" is the distance on the optical axis from the foreground (the lens surface closest to the object) of the optical system to the final surface plus the back focus. "Lens group" is not limited to cases where it is composed of multiple lenses, but also includes cases where it is composed of a single lens.

[0062] Numerical Examples 1 to 4 are either a total focus method in which the entire optical system is moved along the optical axis when focusing from infinity to a close distance, or an inner focus method in which some lenses of the optical system are driven along the optical axis.

[0063] If the optical surface is aspheric, a * symbol is added to the right of the surface number. The aspheric shape is expressed as follows, where X is the displacement from the apex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, and A10 are the aspheric coefficients of each order: x=(h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 ]+A4×h 4 +A6×h 6 +A8×h8 +A10×h 10 In addition, "e±XX" in each aspheric coefficient means "×10±XX."

[0064] (Numerical Example 1) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 28.037 0.60 2.00069 25.5 8.00 2 5.787 1.93 6.93 3 -19.572 0.60 1.49700 81.7 6.89 4 7.267 3.51 1.91082 35.2 7.03 5 -16.549 1.50 6.63 6 166.655 0.65 1.95375 32.3 5.16 7 8.072 1.73 4.76 8 41.661 3.02 1.57501 41.5 4.48 9 -8.820 3.98 4.12 10 (Aperture) ∞ 5.26 4.30 11∞ 3.80 4.57 12 -15241.459 3.37 1.48749 70.2 6.70 13 -8.757 1.00 7.62 14 21.636 4.06 1.49700 81.7 7.83 15 -7.441 0.65 2.00100 29.1 7.67 16 -21.631 14.01 8.00 Image plane ∞ Various data Focal length 7.85 F-number 4.00 Half angle of view 31.70 Image height 4.85 Lens length 49.69 BF 14.01 group focal length 1 -59.88 2 16.35 (Numerical Example 2) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 20.138 0.60 2.00100 29.1 8.00 2 5.616 1.95 6.90 3 -19.992 0.60 1.49700 81.5 6.83 4 5.919 3.92 1.63930 44.9 6.87 5 -10.172 1.50 6.63 6 31.880 0.65 1.85150 40.8 5.15 7 9.585 1.64 4.79 8 -94.113 2.84 1.59551 39.2 4.30 9 -13.790 3.98 4.08 10 (Aperture) ∞ 5.26 4.52 11∞3.13 5.07 12 22.574 3.88 1.59282 68.6 6.52 13 -13.815 1.00 7.24 14 25.300 0.80 1.48749 70.2 7.33 15 9.663 1.76 7.25 16 12.218 4.42 1.49700 81.5 7.77 17 -7.057 0.65 1.78880 28.4 7.71 18 -29.882 14.13 8.00 Image plane ∞ Various data Focal length 7.90 F-number 4.00 Half angle of view: 31.54 Image height 4.85 Lens length 52.72 BF 14.13 group focal length 1 -20.88 2 15.72 (Numerical Example 3) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 13.855 0.60 1.95375 32.3 8.46 2 5.030 2.25 7.12 3 -21.266 0.60 1.49700 81.7 7.06 4 5.046 4.32 1.60311 60.6 7.11 5 -10.266 1.50 6.86 6 13.881 0.65 1.72916 54.7 5.29 7 6.070 1.79 4.80 8 230.213 2.99 1.85400 40.4 5.16 9* -17.387 3.98 5.77 10 (Aperture) ∞ 5.26 6.14 11∞ 3.29 6.60 12 98.564 3.37 1.58913 61.1 7.55 13 -11.342 0.99 8.37 14 19.942 4.10 1.49700 81.7 8.52 15 -8.945 0.65 2.00069 25.5 8.25 16 -30.904 14.01 8.50 Image plane ∞ Aspheric Data 9th page K = 0.00000e+00 A 4=-2.04444e-04 A 6=-6.25786e-06 A 8= 1.41069e-07 Various data Focal length 7.87 F-number: 2.83 Half angle of view: 31.65 Image height 4.85 Lens length 50.36 BF 14.01 group focal length 1 -42.20 2 15.86 (Numerical Example 4) Unit: mm Surface Data Surface number rd nd νd Effective diameter 1 16.651 0.60 2.00100 29.1 8.51 2 5.479 2.16 7.27 3 -21.209 0.60 1.49700 81.5 7.21 4 5.714 4.11 1.64850 53.0 7.29 5 -12.045 1.50 7.03 6 50.739 0.65 1.72916 54.7 5.67 7 9.755 1.79 5.28 8 -29.566 3.18 1.59270 35.3 5.14 9 -10.320 3.98 6.01 10 (Aperture) ∞ 5.26 6.61 11∞2.79 7.32 12* 13.453 4.06 1.59522 67.7 7.77 13 -21.615 1.00 7.56 14 15.251 0.80 1.80400 46.6 7.51 15 7.680 1.85 7.21 16 14.574 4.41 1.49700 81.5 7.88 17 -7.343 0.65 1.77830 23.9 8.14 18 -16.364 14.01 8.51 Image plane ∞ Aspheric Data Side 12 K = 0.00000e+00 A 4=-8.14887e-06 A 6=-7.31987e-10 A 8=-1.40629e-08 Various data Focal length 7.91 F-number: 2.83 Half angle of view: 31.53 Image height 4.85 Lens length 53.40 BF 14.01 group focal length 1 -25.79 2 16.66 Various values ​​in each numerical example are summarized in the following Table 1. Note that in all examples, the d-line is used as the reference wavelength, and the values ​​in Table 1 are for the reference wavelength.

[0065] [Table 1]

[0066] Next, an imaging device 10 including the optical system of each embodiment will be described with reference to FIG. 11. FIG. 11 is a schematic diagram of an imaging device (digital still camera) 10. The imaging device 10 includes a camera body 13 having an imaging element 12, and a lens device 11 including any of the optical systems of the first to fourth embodiments. The lens device 11 and the camera body 13 may be integrally configured, or may be detachably configured. The camera body 13 may be a so-called single-lens reflex camera having a quick-turn mirror, or may be a so-called mirrorless camera having no quick-turn mirror. The imaging element 12 is a photoelectric conversion element such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor that photoelectrically converts an optical image formed by the optical system.

[0067] The imaging device 10 of each embodiment has a lens device 11, and thus can perform stereoscopic imaging using two optical systems OS1 and OS2 with a single small imaging element 12. Note that the optical system of each embodiment is not limited to the digital still camera shown in Fig. 11, but can also be applied to various imaging devices such as broadcast cameras, cameras for silver halide film, and surveillance cameras.

[0068] According to each embodiment, it is possible to provide a small-sized optical system and an imaging device capable of performing stereoscopic imaging more appropriately.

[0069] The disclosure of each embodiment includes the following configuration. (Configuration 1) a first optical system that forms an optical image of a subject in a first imaging area; a second optical system arranged in parallel with the first optical system and configured to form an optical image of the subject in a second imaging area; each of the first optical system and the second optical system includes an aperture stop fixed in an optical axis direction with respect to a position of an image plane, and a lens group disposed closer to the image plane than the aperture stop and movable in the optical axis direction; When the diameter of the aperture stop which determines the axial light beam of each of the first optical system and the second optical system is Φs and the distance between the first optical system and the second optical system is DL, 0.25<Φs / DL<0.90 An optical system characterized in that the following condition is satisfied: (Configuration 2) The optical system described in configuration 1, characterized in that the lens group is an intermediate lens group that adjusts the difference between a first image plane position of the optical image formed in the first imaging region by the first optical system and a second image plane position of the optical image formed in the second imaging region by the second optical system. (Configuration 3) 2. The optical system according to configuration 1, wherein the lens group is a focus group that moves during focusing from infinity to a close distance. (Configuration 4) Let Ls be the distance on the optical axis from the aperture stop to the image plane, and Lm be the distance on the optical axis from the surface of the lens group closest to the object to the image plane when focusing at infinity. 0.40 <Lm / Ls<0.90 3. The optical system according to configuration 1 or 2, wherein the following condition is satisfied: (Configuration 5) Let fm be the focal length of the lens group and f be the focal length of the optical system. 1.2<|fm| / f<6.0 4. The optical system according to any one of configurations 1 to 3, wherein the following condition is satisfied: (Configuration 6) 6. The optical system according to any one of configurations 1 to 5, wherein the lens group has negative refractive power. (Configuration 7) 7. The optical system according to any one of configurations 1 to 6, wherein the lens group has a negative meniscus lens with a convex surface facing the object side. (Configuration 8) The optical system according to any one of configurations 1 to 7, wherein the lens group is composed of one lens. (Configuration 9) Let Ls be the distance on the optical axis from the aperture stop to the image plane, and LT be the distance on the optical axis from the lens surface closest to the object in the optical system to the image plane. 0.50 <Ls / LT<0.80 9. The optical system according to any one of configurations 1 to 8, wherein the following condition is satisfied: (Configuration 10) Let LT be the distance on the optical axis from the lens surface closest to the object in the optical system to the image plane, and f be the focal length of the optical system. 4.0 <LT / f<10.0 10. The optical system according to any one of configurations 1 to 9, wherein the following condition is satisfied: (Configuration 11) Let fn be the focal length of the front group disposed closer to the object side than the aperture stop, and f be the focal length of the optical system. 1.2<|fn| / f<15.0 11. The optical system according to any one of configurations 1 to 10, wherein the following condition is satisfied: (Configuration 12) In the optical system, the effective diameter of the lens arranged closest to the object side is Φf, and the effective diameter of the lens arranged closest to the image side is Φr. 0.80<Φf / Φr<1.20 12. The optical system according to any one of configurations 1 to 11, wherein the following condition is satisfied: (Configuration 13) 13. The optical system according to any one of configurations 1 to 12, wherein the optical system does not include a reflective optical element having a function of bending an optical path. (Configuration 14) 14. An imaging device comprising the optical system according to any one of configurations 1 to 13 and an imaging element. (Configuration 15) 15. The imaging device according to configuration 14, wherein the first imaging region and the second imaging region are imaging regions in one of the imaging elements.

[0070] 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]

[0071] LA Lens device (optical system) OS1 1st optical system OS2 2nd optical system LM lens group (middle lens group, focus group) IC1 Image circle (first imaging area) IC2 Image circle (second imaging area) SP Maximum aperture IP image plane

Claims

1. a first optical system that forms an optical image of a subject in a first imaging area; a second optical system arranged in parallel with the first optical system and configured to form an optical image of the subject in a second imaging area; each of the first optical system and the second optical system includes an aperture stop fixed in an optical axis direction with respect to a position of an image plane, and a lens group disposed closer to the image plane than the aperture stop and movable in the optical axis direction; When a diameter of the aperture stop which determines an axial light beam of each of the first optical system and the second optical system is Φs and a distance between the first optical system and the second optical system is DL, 0.25<Φs / DL<0.90 An optical system characterized in that the following condition is satisfied:

2. The optical system according to claim 1, characterized in that the lens group is an intermediate lens group that adjusts the difference between a first image plane position of the optical image formed in the first imaging region by the first optical system and a second image plane position of the optical image formed in the second imaging region by the second optical system.

3. 2. The optical system according to claim 1, wherein the lens group is a focus group that moves during focusing from infinity to a close distance.

4. Let Ls be the distance on the optical axis from the aperture stop to the image plane, and Lm be the distance on the optical axis from the surface of the lens group closest to the object to the image plane when focusing at infinity. 0.40<Lm / Ls<0.90 4. The optical system according to claim 1, wherein the following condition is satisfied:

5. When the focal length of the lens group is fm and the focal length of the optical system is f, 1.2<|fm| / f<6.0 4. The optical system according to claim 1, wherein the following condition is satisfied:

6. 4. The optical system according to claim 1, wherein the lens group has a negative refractive power.

7. 4. The optical system according to claim 1, wherein the lens group includes a negative meniscus lens having a convex surface facing the object side.

8. 4. The optical system according to claim 1, wherein the lens group is composed of one lens.

9. Let Ls be the distance on the optical axis from the aperture stop to the image plane, and LT be the distance on the optical axis from the lens surface of the optical system closest to the object to the image plane. 0.50<Ls / LT<0.80 4. The optical system according to claim 1, wherein the following condition is satisfied:

10. Let LT be the distance on the optical axis from the lens surface closest to the object side in the optical system to the image plane, and f be the focal length of the optical system. 4.0<LT / f<10.0 4. The optical system according to claim 1, wherein the following condition is satisfied:

11. Let fn be the focal length of the front group disposed closer to the object side than the aperture stop, and f be the focal length of the optical system. 1.2<|fn| / f<15.0 4. The optical system according to claim 1, wherein the following condition is satisfied:

12. In the optical system, the effective diameter of the lens arranged closest to the object side is Φf, and the effective diameter of the lens arranged closest to the image side is Φr. 0.80<Φf / Φr<1.20 4. The optical system according to claim 1, wherein the following condition is satisfied:

13. 4. The optical system according to claim 1, wherein the optical system does not include a reflective optical element having a function of bending an optical path.

14. An imaging device comprising: the optical system according to claim 1; and an imaging element.

15. 15. The imaging device according to claim 14, wherein the first imaging region and the second imaging region are imaging regions in one of the imaging elements.

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