Stereo optical system and imaging device

Abstract

To maximize an image circle formed on one imaging element by two optical systems arranged in parallel.SOLUTION: A stereo optical system forms image circles 103 and 105 on one imaging element IP by two optical systems 101 and 102 arranged in parallel. Each of the optical systems has an angle of view in which other optical system is reflected in first regions 104 and 106 outside in a parallel arrangement direction in the image circles, and a field stop RC so as to lower a light amount of second regions 107 and 108 inside in the image circles. A distance between optical axes of the two optical systems and image circle diameters are set so that a distance between centers of the image circles on the imaging element is shorter than the image circle diameters, third regions 103a and 105a between the first regions and the second regions in the image circles are brought into close contact with each other or adjacent to each other, and the first region is out of the imaging element.SELECTED DRAWING: Figure 17

Description

Technical Field

[0001] The present invention relates to an optical system and an imaging device used for stereo imaging.

Background Art

[0002] When a user acquires left and right parallax images that can be stereoscopically observed with both eyes through an image display device such as a head-mounted display by imaging, an optical system for stereo imaging having two left and right optical systems arranged in parallel is used. Patent Document 1 discloses a stereo optical system that enables imaging of left and right parallax images through two left and right optical systems that are each a fisheye lens. In this stereo optical system, the optical paths of each optical system are bent so that the optical axis interval of the image side portion is narrower than the optical axis interval of the object side portion of the left and right optical systems so that the image circles of the left and right optical systems can be accommodated within one image sensor. By mounting this stereo optical system on a normal lens interchangeable imaging device having one image sensor, stereo imaging becomes possible.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in order to accommodate the image circles of the left and right optical systems within one image sensor as in the stereo optical system of Patent Document 1, the size of the image circle of each optical system needs to be made smaller compared to the case of preparing one image sensor for each optical system. As a result, the number of pixels of the image acquired by imaging decreases, and there is a limit to improving the image quality.

[0005] Furthermore, if both the left and right optical systems are fisheye lenses, stray light generated in one optical system may be reflected in the image circle of the other optical system, potentially degrading image quality.

[0006] The present invention provides a stereo optical system that can improve the image quality of images obtained by imaging by maximizing the image circle formed on a single image sensor by each of two parallel-arranged optical systems. [Means for solving the problem]

[0007] One aspect of the present invention is a stereo optical system having two optical systems arranged in parallel, which form an image circle on a single image sensor. The two optical systems are, When the parallel arrangement direction of the optical axes of the two optical systems is taken as the first direction, one of them Among the image circles , in the first direction, located opposite to the center of the other image circle with respect to the center of one image circle In the first area 、 The other optical system has a field of view that is reflected in it. On the other hand Among the image circles , located in the first direction, on the side of the center of the other image circle relative to the center of the first image circle Second Domain Light incident on It has a field diaphragm to reduce the amount of light. The distance between the optical axes of the two optical systems and the image circle diameter are , set to satisfy the specified conditions , The specified conditions are, On the image sensor, the distance between the centers of the image circles of the two optical systems is shorter than the diameter of the image circle. That thing, The third region between the first and second regions of the image circles of the two optical systems is close to or adjacent to each other. to do , and at least a portion of the first region is outside the image sensor. That is The present invention is characterized by the above. Furthermore, an imaging device equipped with the stereo optical system and image sensor also constitutes another aspect of the present invention. [Effects of the Invention]

[0008] According to the present invention, the image circle (third region) formed on a single image sensor by each of the two parallel-arranged optical systems can be made as large as possible, thereby improving the image quality obtained by imaging. [Brief explanation of the drawing]

[0009] [Figure 1] Cross-sectional view of one of the optical systems in the stereo optical system of Example 1. [Figure 2] Longitudinal aberration diagram of Example 1 (Numerical Example 1). [Figure 3] Diagram showing the peripheral light quantity ratio of Numerical Example 1. [Figure 4] Diagram for explaining the field stop in Example 1. [Figure 5] Cross-sectional view of one of the optical systems in the stereo optical system of Example 2. [Figure 6] Longitudinal aberration diagram of Example 2 (Numerical Example 2). [Figure 7] Diagram showing the peripheral light quantity ratio of Numerical Example 2. [Figure 8] Cross-sectional view of one of the optical systems in the stereo optical system of Example 3. [Figure 9] Longitudinal aberration diagram of Example 3 (Numerical Example 3). [Figure 10] Diagram showing the peripheral light quantity ratio of Numerical Example 3. [Figure 11] Diagram showing the area where stray light from the other optical system is imaged within the image circle of one of the optical systems. [Figure 12] Diagram showing the area of the image circle that is not suitable for viewing. [Figure 13] Diagram showing the field stop [Figure 14] Diagram showing the image circle on the imaging device. [Figure 15] Another diagram showing the image circle on the imaging device. [Figure 16] at Another diagram showing the image circle on the imaging device. [Figure 17] Another diagram showing the image circle on the imaging device. [Figure 18] External view of the imaging device equipped with the stereo optical system of each example.

Modes for Carrying Out the Invention

[0010] The embodiments of the present invention will be described below with reference to the drawings. First, before describing the specific embodiments 1 to 3, we will explain the matters common to each embodiment.

[0011] The stereo optical system of each embodiment is provided on an interchangeable lens that is detachably attached to various imaging devices equipped with image sensors, such as digital cameras, video cameras, broadcast cameras, and surveillance cameras. Alternatively, the stereo optical system of each embodiment may be integrated into the imaging device.

[0012] The stereo optical system of each embodiment has two optical systems (right-eye optical system and left-eye optical system) 101 and 102 arranged in parallel in the Z direction, as shown in Figure 11. In the figure, the left side is the object side (front side), and the right side is the image side (back side). The X direction indicates the optical axis direction in which the optical axis (shown by a dashed line) of each optical system extends. The right side of Figure 11 shows the image plane IP as seen from the object side. One image sensor (imaging surface), shown by a rectangular frame in the figure, is arranged on the image plane IP. The image sensor has a rectangular shape with its longer side extending in the Z direction and its shorter side extending in the Y direction. Image circles 103 and 105 of the two optical systems 101 and 102 are formed on the image sensor. In each embodiment, the image circle is defined as the region from the position (center) where the light intensity is 1 on the optical axis of each optical system to the peripheral edge where the light intensity is 0.

[0013] Each of the two optical systems 101 and 102 has a field of view in which the other (adjacent) optical system is projected into the first outer region 104 and 106 of the image circle 103 and 105 in the Z direction (parallel arrangement direction). Specifically, they have a field of view of 180° or more. This makes it possible to obtain an image of the imaging area that covers the field of view of the observer when viewing it through an image display device such as a head-mounted display, as an image generated from the output of the image sensor, thereby giving the observer a high sense of presence.

[0014] Furthermore, each of the two optical systems 101 and 102 has a field diaphragm RC. The field diaphragm RC is provided to reduce the light intensity of the second region 107 and 108, which are the inner regions in the Z direction of the image circles 103 and 105. The field diaphragm RC only needs to reduce the light intensity of the second region compared to when it is not provided, and it does not necessarily have to reduce the light intensity of the second region to 0. The region between the first region 104 and 106 and the second region 107 and 108 of the image circles 103 and 105 is a third region 103a and 105a suitable for imaging (image viewing).

[0015] In each embodiment, the inter-axis distance Dout and the image circle diameter IH in the image-side portions of the two optical systems 101 and 102 are set to satisfy the following conditions. Firstly, as shown in Figure 16 or Figure 17, the inter-center distance CD of the image circles 103 and 105 of the two optical systems 101 and 102 on the image sensor is set to be shorter than the image circle diameter IH, so that the third regions 103a and 105a are close together or adjacent to each other. Secondly, at least a portion of the first regions 104 and 106 is set to be outside the image sensor.

[0016] Optical systems 101 and 102 each have a first lens group (object-side lens group) L1, a second lens group L2, and a third lens group L3, arranged sequentially from the object side to the image side. A reflective member PR1 is placed between the first lens group L1 and the second lens group L2, and a reflective member PR2 is placed between the second lens group L2 and the third lens group L2c. Reflective member PR1 bends the optical path of optical system 101 in the Z direction, and reflective member PR2 bends the optical path in the X direction. As a result, the distance between the optical axes of the third lens group L3, Dout, is shorter than the distance between the optical axes of the first lens group L1 (baseline length), Din, for the two optical systems 101 and 102. The baseline length is set to approximately the distance between a person's left and right eyes (60-65 cm). This makes it possible to obtain two captured images with parallax that enables stereoscopic viewing from the output of a single image sensor. Prisms, mirrors, etc., can be used as reflective members PR1 and PR2. SP stands for aperture diaphragm.

[0017] Although not shown in the diagram, optical blocks such as optical filters (low-pass filters, infrared cut filters, etc.) or faceplates can be placed between the third lens group L3 and the image plane IP.

[0018] Figure 11 shows light rays from the adjacent optical system 102 reaching the first region 104 in the image circle 103 of the optical system 101. When these light rays reach the first region 104, the optical system 102 is projected into the first region 104. Solid lines represent light rays from the front of the lens closest to the object in the optical system 102, and dashed lines represent light rays from the side of the lens. Similarly, when light rays from the optical system 101 reach the first region 106 in the image circle 105 of the optical system 102, the optical system 101 is projected into the first region 106.

[0019] In this situation, if imaging is performed through each optical system, there will be areas in the resulting image where the adjacent optical system is reflected, and in those areas, the image that was intended to be viewed cannot be seen.

[0020] Furthermore, as shown in Figure 12, a first region 104 containing the left eye optical system 102 exists near the right edge of the image circle 103 of the right eye optical system 101, while the right eye optical system 101 is not captured in the second region 108 near the right edge of the image circle 105 of the left eye optical system 102. Similarly, a first region 106 containing the right eye optical system 101 exists near the left edge of the image circle 105 of the left eye optical system 102, while the left eye optical system 102 is not captured in the second region 107 near the left edge of the image circle 103 of the right eye optical system 101.

[0021] Therefore, the images of the regions near the right and left edges of the right-eye image obtained by imaging through the right-eye optical system 101 and the images of the regions near the right and left edges of the left-eye image obtained by imaging through the left-eye optical system 102 are different from each other. These regions of images that are different from each other are not suitable for viewing with both eyes. Accordingly, the first region (104, 106) of the image circle of each optical system in which the adjacent optical system is reflected, and the second region (107, 108) which is not suitable for viewing the image, are regions that do not need to be imaged in the first place.

[0022] In each embodiment, the stereo optical system reduces the first and second regions of the image circle of each optical system that do not need to be imaged (hereinafter collectively referred to as the "unnecessary image circle region") from the image target, and then enlarges the third region suitable for viewing (hereinafter referred to as the "viewing image circle region") on the image sensor. This increases the number of pixels in the image region corresponding to the viewing image circle region (hereinafter referred to as the "viewing image region") of the captured image, thereby improving image quality.

[0023] Figure 14 shows image circles 103 and 105 when the unnecessary image circle regions are not removed. The top of the figure shows the light intensity distribution of image circles 103 and 105. In this case, since the unnecessary image circle regions 104, 106, 107, and 108 are present on the image sensor, the area of ​​the viewable image circle regions 103a and 105a becomes smaller. As a result, the number of pixels in the viewable image region in the captured image decreases, and the image quality deteriorates.

[0024] On the other hand, Figure 15 shows the case where the second regions 107 and 108 are superimposed, and the arrangement (i.e., the distance between the optical axes of the optical system 101 and 102) and size (diameter) of the image circles 103 and 105 are set so that the first regions 104 and 106 are off the image sensor. The upper part of the figure shows the distribution of light intensity in the image circles 103 and 105. In this case, the area of ​​the viewing image circle regions 103a and 105a becomes larger, and the number of pixels in the viewing image region in the captured image can be increased, thereby improving image quality.

[0025] Furthermore, in each embodiment, while setting the arrangement and size of the image circles 103 and 105 as shown in Figure 15, a field aperture RC is provided between the optical system 101 and 102 and the image sensor to cut off the second regions 107 and 108 from the image circles 103 and 105 on the image sensor. Figure 13(A) shows the effective rays that pass through the optical system and reach the image plane when no field aperture is provided. The rays shown as solid lines in the figure are rays that reach the image height at the edge of the viewing image circle region. The second region is from this image height to the image height reached by the unwanted rays shown as dashed lines.

[0026] Figure 13(B) shows the effective light rays that pass through the optical system and reach the image plane when a field diaphragm RC is provided. The unwanted light rays shown in Figure 13(A) are blocked by the field diaphragm RC, reducing the light intensity in the second region. Hereafter, reducing the light intensity in the second region by the field diaphragm RC will also be referred to as cutting out the second region of the image circle.

[0027] Figure 16 shows image circles 103 and 105 having the arrangement and size shown in Figure 15, with the second regions 107 and 108 further cut off by the field diaphragm RC. The light intensity distribution of image circles 103 and 105 is shown at the top of the figure. The D-cut edges of image circles 103 and 105, in which parts of the second regions 107 and 108 are D-cut, are adjacent to each other. This reduces (eliminates) the overlapping area of ​​image circles 103 and 105.

[0028] Furthermore, as shown in Figure 17, the sizes of image circles 103 and 105 may be enlarged to the extent that the other image circle does not overlap with their respective viewing image circle regions 103a and 105a. In this case as well, the D-cut edges of image circles 103 and 105 overlap with the second region of the other image circle while remaining close to each other. As a result, the inner edges of the viewing image circle regions 103a and 105a are close to each other (preferably adjacent).

[0029] By arranging and sizing image circles 103 and 105 in this way, the area of ​​the viewing image region in the captured image can be increased, and the image quality of the viewing image region can be further improved.

[0030] The stereo optical system in each embodiment is an optical system that enables imaging of two optical images formed by two optical systems 101 and 103 with a single image sensor. The viewing image circle regions 103a and 105a of the two optical systems 101 and 103 are brought as close together as possible while increasing the size of each image circle. For this reason, a field aperture RC is provided to prevent light rays from the other optical system from entering the image circle of each optical system and degrading the image quality obtained by imaging through each optical system.

[0031] Furthermore, because the field of view of each optical system is large, there are many imaging scenes in which stray light from light sources such as the sun enters each optical system. The optical path of such stray light is often different from the optical path of the effective rays. For this reason, even if stray light is limited by a field diaphragm placed within the optical system, the effect of reducing stray light is small. For this reason, in each embodiment, by providing a field diaphragm RC directly in front of the image sensor (between the optical system and the image sensor), stray light can be effectively blocked.

[0032] Furthermore, rays with different image heights overlap at least partially in the lenses behind the aperture diaphragm SP. For example, the rays shown by solid and dashed lines in Figure 11 partially overlap in all the lenses behind the aperture diaphragm SP, and are completely separated on the image side of the optical system beyond the image-side lens. For this reason, when reducing the light intensity in the second region with the field diaphragm RC, it is preferable to place the field diaphragm RC between the optical system where the above rays are separated and the image sensor in order to minimize the reduction in light intensity in the viewing image circle region.

[0033] In each embodiment, the stereo optical system satisfies the following condition (1), where Dout is the distance between the optical axes of the image-side portions (i.e., the third lens group L3) of the two optical systems 101 and 102, and IH is the diameter of the image circle of each optical system. 0.75 ≤ Dout / IH ≤ 0.99 (1) If Dout / IH falls below the lower limit of equation (1), the amount of light in the viewing image circle area decreases too much, which is undesirable. If the reduced amount of light is corrected by image processing, noise increases and image quality deteriorates. Also, if Dout / IH exceeds the upper limit of equation (1), the viewing image circle area cannot be sufficiently enlarged on the image sensor, and a high-quality image cannot be obtained, which is also undesirable.

[0034] It is preferable to set the numerical range of equation (1) as follows. 0.77 ≤ Dout / IH ≤ 0.97 (1a) It is even more preferable to set the numerical range of equation (1) as follows. 0.79 ≤ Dout / IH ≤ 0.94 (1b) By satisfying the conditions of equation (1), the size of the viewing image circle region formed on a single image sensor by each of the two parallel-arranged optical systems 101 and 103 can be made as large as possible, thereby improving the image quality obtained by imaging.

[0035] The stereo optical system of each embodiment should preferably satisfy at least one of the following conditions (2) to (6).

[0036] When the half-angle of view of each optical system is ω, it is desirable that the conditions of equation (2) be satisfied. 160.0°≦2ω≦220.0° (2) If 2ω falls below the lower limit of equation (2), the field of view that can be displayed on the image display device becomes small, making it undesirable as it prevents the provision of an immersive image viewing experience. If 2ω exceeds the upper limit of equation (2), the field of view that can be displayed becomes too wide, resulting in a small number of pixels per unit field of view and a decrease in image quality, which is also undesirable.

[0037] It is preferable to set the numerical range of equation (2) as follows. 170.0°≦2ω≦215.0° (2a) It is even preferable to set the numerical range of equation (2) as follows. 175.0°≦2ω≦210.0° (2b) In each embodiment, the stereo optical system preferably satisfies the following condition (3), where Din is the interaxial distance between the first lens group L1, which is the object-side lens group of the two optical systems 101 and 103, and Dout is the interaxial distance between the third lens group L3, which is the image-side lens group. 0.05 ≤ Dout / Din ≤ 0.50 (3) If Dout / Din falls below the lower limit of equation (3), the baseline length becomes extremely wide compared to the interpupillary distance of a person, which can lead to excessive parallax between the left and right eye images and cause fatigue in the observer, and is therefore undesirable. If Dout / Din exceeds the upper limit of equation (3), there will not be sufficient parallax between the left and right eye images, which is also undesirable as it will not provide the viewer with a sense of depth.

[0038] It is preferable to set the numerical range of equation (3) as follows. 0.10 ≤ Dout / Din ≤ 0.45 (3a) It is preferable to set the numerical range of equation (3) as follows. 0.15 ≤ Dout / Din ≤ 0.40 (3b) In each embodiment, the stereo optical system preferably satisfies the following condition (4), where Fno is the F-number of each optical system. 2.40 ≤ Fno ≤ 6.50 (4) If Fno falls below the lower limit of equation (4), the reflective members PR1 and PR2 and the aperture diaphragm SP become larger, which is undesirable. If Fno exceeds the upper limit of equation (4), noise increases during imaging and image quality deteriorates, which is also undesirable. It is preferable to set the numerical range of equation (4) as follows. 2.55 ≤ Fno ≤ 5.90 (4a) It is even preferable to set the numerical range of equation (4) as follows. 2.70 ≤ Fno ≤ 4.50 (4b) Figure 4 schematically shows the field diaphragm RC provided in each optical system. The field diaphragm RC blocks light rays in order to reduce the amount of light in the second region at the light-shielding area (hatched area) outside the distance RCa from the optical axis of each optical system. The maximum aperture diameter of the portion of the field diaphragm RC that is not provided is RCb (>RCa). In this case, RCa and RCb satisfy the conditions shown in equation (5) below. 0.25 ≤ RCa / RCb ≤ 0.48 (5) If RCa / RCb falls below the lower limit of equation (5), the amount of light in the viewing image circle area becomes too low, which is undesirable. If RCa / RCb exceeds the upper limit of equation (5), the amount of light in the unwanted image circle area cannot be sufficiently reduced, and the viewing image circle area cannot be expanded, thus preventing high image quality, which is also undesirable.

[0039] It is preferable to set the numerical range of equation (5) as follows. 0.28 ≤ RCa / RCb ≤ 0.47 (5a) It is even preferable to set the numerical range of equation (5) as follows.

[0040] 0.30 ≤ RCa / RCb ≤ 0.46 (5b) The field aperture RC may be a straight line passing through the position of RCa from the optical axis, as shown in Figure 4, or it may be a curved shape passing through the position of RCa.

[0041] In each embodiment, the stereo optical system preferably satisfies the following condition (6), where dRC is the distance along the optical axis from the field aperture RC to the image plane IP, and sk is the distance along the optical axis from the image-side surface of the image-side lens (final lens) that has refractive power in each optical system to the image plane IP. 0.20 ≤ dRC / sk < 1.00 (6) In each embodiment, as described above, a field aperture RC is placed between the final lens of the optical system and the image plane IP in order to minimize the reduction in light intensity in the viewing image circle region while reducing the light intensity in the unwanted image circle region. If the lower limit of equation (6) is exceeded, the light intensity in the region suitable for viewing will decrease significantly, which is undesirable. If dRC / sk exceeds the upper limit of equation (6), interference will occur with optical elements such as low-pass filters and infrared cut filters placed on the object side of the image sensor, which is also undesirable.

[0042] It is preferable to set the numerical range of equation (6) as follows. 0.35 ≤ dRC / sk ≤ 0.95 (6a) It is even preferable to set the numerical range of equation (6) as follows. 0.50 ≤ dRC / sk ≤ 0.90 (6b) The stereo optical systems of Examples 1 to 3 will be described below, along with corresponding numerical examples. [Examples]

[0043] The stereo optical system of Example 1 (Numerical Example 1) has two optical systems, as shown in Figure 1, with an image height of 10.00 mm, a focal length of 5.59 mm, and a half-angle of view of 102.50°, and is used in an imaging device equipped with an image sensor measuring 36 mm horizontally × 24 mm vertically. The optical axes of the third lens group L3 of the two optical systems are located at +9 mm and -9 mm in the Z direction from the center of the image sensor, respectively. The distance between the optical axes Dout between the third lens groups L3 is 18.0 mm. The baseline length (Din) of the two optical systems is 63.6 mm.

[0044] The first lens group L1 of each optical system consists of a negative meniscus lens convex to the object side, a negative meniscus lens convex to the object side, and a cemented lens formed from a negative meniscus lens convex to the object side and a positive meniscus lens convex to the object side, arranged in order from the object side to the image side. By making the image-side surface of the second negative meniscus lens from the object side an aspherical surface, field curvature and astigmatism are corrected.

[0045] The second lens group L2 of each optical system consists of a cemented lens of a negative meniscus lens (convex towards the object side) and a biconvex lens, and an aperture diaphragm SP, arranged in order from the object side to the image side.

[0046] The third lens group L3 of each optical system is composed of a cemented lens consisting of a negative meniscus lens and a biconvex lens that are convex to the object side, a biconvex lens, and a cemented lens consisting of a positive meniscus lens that are convex to the image side and a negative meniscus lens that are convex to the image side, arranged in order from the object side to the image side.

[0047] The solid line in Figure 3 shows the peripheral illumination ratio for each image height relative to the light intensity on the optical axis in the direction without the field aperture RC (Y direction) in the optical system of Numerical Example 1. The dashed line in Figure 3 shows the peripheral illumination ratio in the Z direction, which is reduced by the field aperture RC in the optical system of Numerical Example 1. The optical system of Numerical Example 1 has an image height of 10.00 mm, but since a certain amount of light is necessary for image viewing, the light intensity ratio at an image height of 10.00 mm is set to 18.7%. Therefore, even at image heights above 10.00 mm, there is still sufficient light, and the image height at which the light intensity ratio becomes 0% is 10.18 mm.

[0048] Thus, it is necessary to set the image height to be limited by the field aperture RC so that the area with light intensity exceeding the set image height of 10.00 mm does not overlap with the area where the image generated by imaging through the adjacent optical system is viewed.

[0049] In this numerical example, the highest image height in the Z direction of the viewing image circle region is 8.20 mm (10.18 mm in the Y direction), and as shown by the dashed line, a field diaphragm RC is provided so that the light intensity decreases from an image height of 8.20 mm in the Z direction. Specifically, in Figure 4, by providing a field diaphragm RC to reduce the light in the region of RCa 6.60 mm or more in the Z direction of the original effective diameter RCb 15.45 mm, the light intensity ratio is reduced from an image height of 8.20 mm as shown by the dashed line in Figure 3, and the light intensity ratio becomes 0% at an image height of 9.70 mm.

[0050] As mentioned above, the interaxial distance between the third lens groups L3 of the two optical systems is 18.0 mm, the viewing image circle area extends to an image height of 8.20 mm, and the image height at which the peripheral illumination ratio becomes 0% is 9.70 mm. Therefore, the viewing image circle areas of the two optical systems are set so that they do not overlap with the viewing image circle area of ​​the adjacent optical system.

[0051] Furthermore, while the distance from the center to the edge of the image sensor is 9.0 mm in the Z direction, the first region in which the adjacent optical system is captured starts from an image height of 8.20 mm, and the viewing image circle region is contained within the image sensor. Thus, it is important to set the interaxial distance of the third lens group L3, the image circle diameter, and the field aperture RC so that the viewing image circle regions of each of the two optical systems are secured on the central side of the image sensor, and on the peripheral side, only the first region in which the adjacent optical system is captured is outside the image sensor.

[0052] Figure 2 shows the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the optical system in numerical example 1. In the spherical aberration diagram, Fno indicates the F number, the solid line shows the spherical aberration with respect to the d line (wavelength 587.6 nm), and the dashed line shows the spherical aberration with respect to the g line (wavelength 435.8 nm). In the astigmatism diagram, the solid line ΔS shows the sagittal image plane, and the dashed line ΔM shows the meridional image plane. The distortion diagram shows the distortion with respect to the d line. The chromatic aberration diagram shows the lateral chromatic aberration at the g line. ω is the half-angle of view (°). The explanation of these longitudinal aberration diagrams is the same for the other numerical examples described later.

[0053] Furthermore, the numerical values ​​for Numerical Example 1 are shown after Example 3. In the Numerical Example, the surface number i indicates the order of the surfaces when counted from the object side. r is the radius of curvature (mm) of the i-th surface from the object side, d is the lens thickness or air gap (mm) between the i-th and (i+1)-th surfaces, and nd is the refractive index of the optical material at the d-line between the i-th and (i+1)-th surfaces. νd is the Abbe number based on the d-line of the optical material between the i-th and (i+1)-th surfaces. The Abbe number νd is given by Nd, NF, and NC, respectively, when the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) are Nd, NF, and NC. νd = (Nd-1) / (NF-NC) It is represented as follows.

[0054] BF represents the back focus (mm). The back focus is the distance along the optical axis from the final surface of the optical system (the lens surface closest to the image) to the paraxial image plane, expressed in terms of air equivalent length, and corresponds to sk in equation (6). The total lens length (mm) is the distance along the optical axis from the frontmost lens surface (the lens surface closest to the object) to the final surface of the optical system, plus the back focus.

[0055] The asterisk (*) next to the surface number indicates that the surface has an aspherical shape. The aspherical shape is expressed by the following formula, where X is the displacement from the surface vertex in the direction of the optical axis, H is the height from the optical axis in the direction perpendicular to the optical axis, the direction of light propagation is positive, R is the radius of paraxial curvature, K is the cone constant, and A4, A6, A8, A10 are aspherical coefficients. The "eM" of the cone constant and aspherical coefficients is ×10 -M It means...

[0056]

number

[0057] Furthermore, Table 1 summarizes the values ​​corresponding to the aforementioned conditional expressions (1) to (6) in Numerical Example 1. [Examples]

[0058] The stereo optical system of Example 2 (Numerical Example 2) has two optical systems, as shown in Figure 5, with an image height of 9.70 mm, a focal length of 5.74 mm, and a half-angle of view of 96.82°, and is used in an imaging device equipped with an image sensor measuring 36 mm horizontally × 24 mm vertically. The optical axes of the third lens group L3 of the two optical systems are located at +9.25 mm and -9.25 mm in the Z direction from the center of the image sensor, respectively. The distance between the optical axes Dout of the third lens group L3 is 18.5 mm. The baseline length (Din) of the two optical systems is 60.75 mm.

[0059] The first lens group L1 of each optical system consists of a negative meniscus lens convex to the object side, a negative meniscus lens convex to the object side, a negative meniscus lens convex to the object side, and a positive meniscus lens convex to the object side, arranged from the object side to the image side. By making the object-side surface of the third negative meniscus lens from the object side an aspherical surface, field curvature and astigmatism are corrected. The configuration of the second and third lens groups L2 and L3 of each optical system is the same as in Example 1.

[0060] The solid line in Figure 7 shows the peripheral illumination ratio for each image height relative to the light intensity on the optical axis in the Y direction without a field aperture RC in the optical system of numerical example 2. The dashed line in Figure 7 shows the peripheral illumination ratio in the Z direction reduced by the field aperture RC in the optical system of numerical example 2. The second region in this numerical example is the region with an image height of 8.18 mm or more, but the field aperture RC is set so that the light intensity decreases from an image height of 7.59 mm in the Z direction. This setting reduces the light intensity in the viewing image circle region, but the image height at which the light intensity becomes 0 becomes smaller. Therefore, it becomes possible to widen the distance between the viewing image circle regions of the two optical systems, and to further enlarge the image circle. In other words, it is possible to achieve higher image quality in the captured images.

[0061] Furthermore, while it is desirable to reduce the light intensity in the viewing image circle area using the field diaphragm RC to an extent that does not impede the viewing of the captured image, the reduction in light intensity may also be compensated for by image processing of the captured image.

[0062] In this numerical example, by providing a field diaphragm RC to reduce light in the region of RCa 6.60 mm or more in the Z direction within the effective diameter RCb 15.83 mm shown in Figure 4, the light intensity ratio is reduced from an image height of 7.59 mm to 0% at an image height of 9.72 mm, as shown by the dashed line in Figure 7.

[0063] As mentioned above, the interaxial distance between the third lens groups L3 of the two optical systems is 18.5 mm, the viewing image circle area extends to an image height of 8.18 mm, and the image height at which the peripheral illumination ratio becomes 0% is 9.72 mm. Therefore, the viewing image circle areas of the two optical systems are set so that they do not overlap with the viewing image circle area of ​​the adjacent optical system.

[0064] Furthermore, while the distance from the center to the edge of the image sensor in the Z direction is 8.75 mm, the first region where the adjacent optical system is captured starts from an image height of 8.18 mm, and the viewing image circle region is contained within the image sensor.

[0065] Figure 6 shows the longitudinal aberration of the optical system in numerical example 2. Table 1 summarizes the values ​​corresponding to the aforementioned conditional equations (1) to (6) in numerical example 2. [Examples]

[0066] The stereo optical system of Example 3 (Numerical Example 3) has two optical systems, as shown in Figure 8, with an image height of 7.00 mm, a focal length of 3.85 mm, and a half-angle of view of 104.18°, and is used in an imaging device equipped with an image sensor measuring 22.5 mm horizontally × 15 mm vertically. The optical axes of the third lens group L3 of the two optical systems are located at +5.70 mm and -5.70 mm in the Z direction from the center of the image sensor, respectively. The distance between the optical axes Dout between the third lens groups L3 is 11.4 mm. The baseline length (Din) of the two optical systems is 55.0 mm.

[0067] The configurations of the first, second, and third lens groups L1, L2, and L3 of each optical system are the same as in Example 1.

[0068] The solid line in Figure 10 shows the peripheral illumination ratio for each image height relative to the light intensity on the optical axis in the Y direction without a field diaphragm RC in the optical system of numerical example 3. The image height at which the light intensity ratio becomes 0% is 7.06 mm. The dashed line in Figure 10 shows the peripheral illumination ratio in the Z direction reduced by the field diaphragm RC in the optical system of numerical example 3. The second region in this numerical example is the region with an image height of 5.40 mm or more, but the field diaphragm RC is set so that the light intensity decreases from an image height of 4.00 mm in the Z direction.

[0069] In this embodiment as well, it is desirable that the reduction in light intensity in the viewing image circle area due to the field aperture RC be kept to a level that does not hinder the viewing of the captured image, but the reduction in light intensity may also be compensated for by image processing of the captured image.

[0070] In this numerical example, by providing a field diaphragm RC to reduce light in the region of RCa 3.71 mm or more in the Z direction within the effective diameter RCb 10.86 mm shown in Figure 4, the light intensity ratio is reduced from an image height of 4.00 mm to 0% at an image height of 5.95 mm, as shown by the dashed line in Figure 10.

[0071] As mentioned above, the interaxial distance between the third lens groups L3 of the two optical systems is 11.4 mm, the viewing image circle area extends to an image height of 5.40 mm, and the image height at which the peripheral illumination ratio becomes 0% is 5.95 mm. Therefore, the viewing image circle areas of the two optical systems are set so that they do not overlap with the viewing image circle area of ​​the adjacent optical system.

[0072] Furthermore, while the distance from the center to the edge of the image sensor in the Z direction is 5.55 mm, the first region where the adjacent optical system is captured starts from an image height of 5.40 mm, and the viewing image circle region is contained within the image sensor.

[0073] Figure 9 shows the longitudinal aberration of the optical system in numerical example 3. Table 1 summarizes the values ​​corresponding to the aforementioned conditional equations (1) to (6) in numerical example 3.

[0074] According to the embodiments described above, the image circle formed by each of the two parallel-arranged optical systems on a single image sensor can be made as large as possible, thereby improving the image quality obtained by imaging.

[0075] In the above embodiments, the case where the projection method of the optical system is equiangled projection was described. However, optical systems with other projection methods, such as equisolid angle projection or stereoscopic projection, may also be used.

[0076] Furthermore, the image sensor sizes listed in the above embodiments are merely examples, and other image sensor sizes may be used. [Numerical Example 1] Unit: mm Surface data Face number rd nd νd Effective diameter 1 40.212 2.00 1.91082 35.3 48.01 2 12.305 9.23 24.54 3 23.956 1.09 1.85400 40.4 22.96 4* 12.069 3.85 19.19 5 32.411 1.09 1.90043 37.4 18.31 6 9.048 4.18 1.85478 24.8 15.10 7 14.719 7.49 13.66 8 ∞ 13.00 1.51633 64.1 10.15 9 ∞ 2.00 6.56 10 14.807 0.80 2.00100 29.1 7.15 11 9.141 4.00 1.62004 36.3 7.01 12 -32.731 1.00 7.11 13 (aperture) ∞ 2.00 7.01 14 ∞ 13.00 1.51633 64.1 6.85 15 ∞ 1.97 9.52 16 50.909 0.97 2.00100 29.1 11.20 17 19.691 3.01 1.49700 81.5 11.56 18 -30.051 0.00 12.38 19 12.552 6.53 1.43875 94.7 14.12 20 -16.148 0.30 13.99 21 -17.940 3.21 1.59522 67.7 13.70 22 -11.478 0.86 2.00100 29.1 13.69 23 -80.041 2.05 14.50 24 ∞ 11.46 15.45 Image plane ∞ Aspherical data Side 4 K =-9.46957e-002 A 4=-2.00280e-005 A 6= 1.39815e-007 A 8=-2.65465e-009 Various data Focal length 5.59 F-number 4.10 Half-angle (°): 102.50 Image height 10.00 Lens length: 95.08 BF 11.46 Entrance pupil position 12.15 Exit pupil position -24.35 Front principal point position 16.86 Back principal point position 5.87 RCA 6.60 Rcb 15.45 Single lens data Lens starting plane, focal length 1 1 -20.15 2 3 -29.73 3 5 -14.25 4 6 20.51 5 8 0.00 6 10 -25.68 7 11 11.96 8 14 0.00 9 16 -32.59 10 17 24.43 11 19 17:30 12 21 45.17 13 22 -13.47 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd Effective diameter 1 32.477 1.94 1.95375 32.3 45.69 2 13.390 10.10 26.47 3 36.545 1.05 1.83481 42.7 24.20 4 20.546 3.00 21.22 5* 61.673 1.05 1.85400 40.4 19.54 6 9.845 2.09 15.42 7 11.893 3.50 1.85478 24.8 15.29 8 14.071 6.90 13.43 9 ∞ 13.25 1.51633 64.1 10.71 10 ∞ 1.00 9.22 11 18.144 0.75 1.91082 35.3 9.78 12 10.520 4.25 1.59270 35.3 9.65 13 -33.345 1.00 9.89 14 (aperture) ∞ 1.00 9.84 15 ∞ 13.00 1.51633 64.1 9.80 16 ∞ 1.72 10.39 17 44.257 0.94 1.95375 32.3 11.88 18 18.233 3.15 1.49700 81.5 12.20 19 -35.627 0.00 12.97 20 14.043 6.91 1.43875 94.7 14.50 21 -17.502 0.30 14.46 22 -37.189 4.08 1.49700 81.5 13.93 23 -10.631 0.83 2.00100 29.1 13.56 24 -54.546 4.27 14.36 25 ∞ 11.46 15.83 Image plane ∞ Aspherical data 5th page K = 0.00000e+000 A 4= 9.42786e-006 A 6=-1.81797e-007 A 8= 2.60380e-009 A10 = -9.79910e-012 Various data Focal length 5.74 F-number 2.91 Half-angle (°): 96.82 Image height 9.70 Lens length: 97.55 BF 11.46 Entrance pupil position 13.53 Exit pupil position -28.20 Front principal point position 18.44 Back principal point position 5.72 RCa 6.60 RCb 15.83 Single lens data Lens starting plane, focal length 1 1 -25.14 2 3 -57.96 3 5 -13.85 4 7 51.64 5 9 0.00 6 11 -28.84 7 12 14.00 8 15 0.00 9 17 -33.10 10 18 24.75 11 20 19.03 12 22 28.50 13 23 -13.32 [Numerical Example 3] Unit: mm Surface data Face number rd nd νd Effective diameter 1 26.681 1.40 2.00100 29.1 42.54 2 12.236 11.23 24.42 3 54.814 0.76 1.85400 40.4 20.83 4* 9.538 4.71 15.28 5 91.244 0.76 1.88300 40.8 14.48 6 8.241 5.63 1.85478 24.8 12.87 7 36.217 7.12 11.59 8 ∞ 14.41 1.51633 64.1 8.15 9 ∞ 1.90 5.60 10 28.260 0.78 1.91082 35.3 5.99 11 11.944 2.80 1.59270 35.3 5.98 12 -26.153 0.70 6.20 13 (aperture) ∞ 1.21 6.22 14 ∞ 14.41 1.95375 32.3 6.24 15 ∞ 1.51 6.37 16 16.501 0.68 1.90043 37.4 7.29 17 12.163 2.20 1.43875 94.7 7.35 18 -58.748 1.76 7.80 19 21.262 3.26 1.43875 94.7 8.68 20 -14.448 0.30 8.95 21 -50.926 3.13 1.49700 81.5 8.87 22 -10.135 0.60 1.95375 32.3 8.85 23 -59.880 6.03 9.16 24 ∞ 11.46 10.86 Image plane ∞ Aspherical data Side 4 K = 7.88130e-002 A 4=-3.19820e-005 A 6= 6.69832e-007 A 8=-4.82627e-009 Focal length 3.85 F-number 4.10 Half-angle (°): 104.18 Image height 7.00 Lens length: 98.74 BF 11.46 Entrance pupil position 12.17 Exit pupil position -29.90 Front principal point position 15.66 Back principal point position 7.61 RCA 3.71 Rcb 10.86 Single lens data Lens starting plane, focal length 1 1 -23.73 2 3 -13.63 3 5 -10.30 4 6 11.42 5 8 0.00 6 10 -23.24 7 11 14.22 8 14 0.00 9 16 -55.50 10 17 23.19 11 19 20 17 12 21 24.83 13 22 -12.87

[0077] [Table 1]

[0078] Figure 18 shows a digital still camera as an imaging device using the stereo optical system of each of the above embodiments as the imaging optical system. 20 is the camera body, and 21 is the imaging optical system composed of one of the stereo optical systems of Embodiments 1 to 3. 22 is an image sensor such as a CCD sensor or CMOS sensor built into the camera body 20 that captures the optical image (subject image) formed by the imaging optical system 21. 23 is a recording unit that records image data generated by processing the imaging signal from the image sensor 22, and 24 is a rear display that displays the image data.

[0079] By using the stereo optical system of each embodiment in this camera, high-quality images that enable stereoscopic viewing can be obtained.

[0080] The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention. [Explanation of symbols]

[0081] 101 Right eye optical system 102 Left eye optical system Image Circles 103 and 105 103a, 105a Third area 104, 106 First Domain 107, 108 Second Domain RC field aperture IP image plane (image sensor)

Claims

1. A stereo optical system having two parallel-arranged optical systems, which form an image circle of the two optical systems on a single image sensor, The two optical systems described above are, When the parallel arrangement direction of the optical axes of the two optical systems is defined as the first direction, One of the image circles has a field of view in which the other optical system is projected into a first region located in the first direction opposite to the center of the other image circle relative to the center of the first image circle, One of the image circles has a field aperture for reducing the amount of light incident on a second region located on the side of the center of the other image circle relative to the center of the first image circle in the first direction, The distance between the optical axes of the two optical systems and the diameter of the image circle are set to satisfy predetermined conditions. The stereo optical system is characterized in that the predetermined conditions are that the distance between the centers of the image circles of the two optical systems on the image sensor is shorter than the diameter of the image circle, the third regions between the first region and the second region of the image circles of the two optical systems are close together or adjacent, and at least a part of the first region is outside the image sensor.

2. When the distance between optical axes is Dout and the diameter of the image circle is IH, 0.75 ≤ Dout / IH ≤ 0.99 The stereo optical system according to claim 1, characterized in that it satisfies the following conditions.

3. When the half-angle of view of each of the two optical systems is ω, 160.0° ≤ 2ω ≤ 220.0° A stereo optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

4. Each of the two optical systems has an object-side lens group and an image-side lens group. Due to the bending of the optical path between the object-side lens and the image-side lens group, the distance between the optical axes of the image-side lens group in the two optical systems becomes shorter than the distance between the optical axes of the object-side lens group. The stereo optical system according to any one of claims 1 to 3, characterized in that the distance between the optical axes of the two optical systems is the distance between the optical axes of the image-side lens group.

5. When the distance between the optical axes of the object-side lens group is Din and the distance between the optical axes of the image-side lens group is Dout, 0.05 ≤ Dout / Din ≤ 0.50 The stereo optical system according to claim 4, characterized in that it satisfies the following conditions.

6. When the F-number of each of the two optical systems is denoted as Fno, 1.40 ≤ Fno ≤ 6.50 A stereo optical system according to any one of claims 1 to 5, characterized in that it satisfies the following conditions.

7. In each of the two optical systems, when RCa is the distance from the optical axis of the optical system to the light-shielding portion in the field diaphragm that reduces the amount of light, and RCb is the maximum aperture diameter of the portion in the field diaphragm where the light-shielding portion is not provided, 0.25 ≤ RCa / RCb ≤ 0.48 A stereo optical system according to any one of claims 1 to 6, characterized in that it satisfies the following conditions.

8. In each of the two optical systems described above, when dRC is the distance along the optical axis from the field diaphragm to the image plane, and sk is the distance along the optical axis from the image-side surface of the lens closest to the image among the refractive lenses in the optical system to the image plane, 0.20≦dRC / sk<1.00 A stereo optical system according to any one of claims 1 to 7, characterized in that it satisfies the following conditions.

9. A stereo optical system according to any one of claims 1 to 8, An imaging device characterized by having the aforementioned image sensor.

Images