Optical system and imaging device

Abstract

To provide an optical system capable of reducing ring blur when a catoptric system is used.SOLUTION: An optical system provided herein comprises a catoptric system (601B, 601C) and an optical adjustment layer (401) including a transmittance distribution layer or reflectance distribution layer that is rotationally symmetric about an optical axis (OA), where the optical adjustment layer (401) has the maximum transmittance or reflectance (Tmax or Rmax) at a position different from the optical axis (OA).SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Patent Document 1 discloses an optical system that is compact and has a long focal length, and is capable of capturing images at a high magnification, by internally reflecting light using a reflecting member (reflection mirror). Patent Document 2 discloses an apodization filter that has a maximum transmittance at the center of the optical axis and decreases the transmittance toward the periphery, smoothing the shape of the blur. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-85725 A [Patent Document 2] JP 2000-47085 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the optical system disclosed in Patent Document 1, since there is no light passing through the center of the optical axis, ring blur occurs, where the blur is ring-shaped. Ring blur reduces the image quality of a captured image, so reducing ring blur is a challenge in an imaging optical system using a reflective optical system. Such ring blur cannot be reduced by the apodization filter disclosed in Patent Document 2.

[0005] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide an optical system and an imaging device that are capable of reducing ring blur when a reflective optical system is used. [Means for solving the problem]

[0006] The optical system according to one aspect of the present invention includes a reflecting optical system and a transmittance distribution that is rotationally symmetric about an optical axis. Layer An optical adjustment layer including , a light-shielding portion and and the optical adjustment layer transmits light at a position different from the optical axis. Rate With maximum value The maximum value of the transmittance is higher than the light transmittance at a second position corresponding to an end of the light blocking portion in the transmission region of the transmittance distribution layer. .

[0007] Other objects and features of the present invention will be described in the following embodiments. Effect of the Invention

[0008] According to the present invention, it is possible to provide an optical system and an imaging device capable of reducing ring blur when a reflective optical system is used. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an imaging device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating the configuration of a reflective optical system according to the present embodiment. [Diagram 3] 11A and 11B are diagrams for comparing general blur and ring blur of the present embodiment. [Figure 4] 3 is an example of an optical adjustment layer in the present embodiment. [Diagram 5] 4 is an example of a transmittance distribution of the optical adjustment layer in the present embodiment. [Figure 6] 4 is an example of a reflectance distribution of the optical adjustment layer in the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0011] First, an imaging device 10 according to the present embodiment and an imaging device 20 as a comparative example will be described with reference to Figs. 1(a) and 1(b). Fig. 1(a) is a configuration diagram of the imaging device 10 according to the present embodiment, and the imaging device 10 is equipped with a lens device (interchangeable lens) 600 having a reflective optical system. Fig. 1(b) is a configuration diagram of an imaging device 20 as a comparative example, and the imaging device 20 is equipped with a normal lens device (interchangeable lens) 500 (not having a reflective optical system). The imaging devices 10 and 20 each include a camera body (lens-interchangeable digital camera body) 100 and a lens device 600 or lens device 500 that is detachable from the camera body 100. Note that this embodiment can also be applied to an imaging device in which the camera body 100 and the lens device are integrally configured.

[0012] A light beam transmitted through each lens group (imaging optical system) in the lens device 600 (or lens device 500) is guided to an image sensor 101 that receives an image of a subject. The image sensor 101 is composed of pixels arranged in a matrix that convert the image of the subject into an electric signal. The pixel information converted into an electric signal is output to a camera CPU 104. The camera CPU 104 performs various correction processes for obtaining an image signal or a focus detection signal, and processes for converting the obtained image signal into a live view image, a recorded image, or an EVF image. Note that in this embodiment, these processes are performed by the camera CPU 104, but are not limited to this and may be performed by a dedicated circuit.

[0013] The operation members 105 are various members for setting the shooting mode and shooting conditions (F-number, ISO, exposure time, etc.) of the camera body 100. The storage medium 106 is a flash memory, and is a medium for recording captured still images and videos. The in-finder display 107 has a display 108 as a small, high-definition display means such as an organic EL display or a liquid crystal display, and an eyepiece 109. The external display 110 uses an organic EL display or a liquid crystal display with a screen size suitable for naked eye viewing. Various information such as the setting state of the camera body 100, live view images, and captured images is displayed on the in-finder display 107 and the external display 110.

[0014] The focal plane shutter 111 is disposed in front of the image sensor 101. The shutter driver 112 is, for example, a motor, and controls the exposure time when capturing a still image by controlling the driving of the shutter blades. The camera-side communication terminal 113 is provided in a camera mount for mounting the lens device 600 (or the lens device 500). The camera-side communication terminal 113, together with a lens-side communication terminal 508 provided in the lens mount, transmits and receives information exchanged between the camera CPU 104 and a lens CPU 507 (described later).

[0015] In this embodiment, the lens apparatus 600 (or the lens apparatus 500) is detachable from the camera body 100. The lens apparatus 500 has a reflective optical system. The lens apparatus 600 is a zoom lens with a variable focal length. However, any type of lens may be used.

[0016] A light beam from a subject passes through the first lens group 601 (or the first lens group 501), the second lens group 502 (only FIG. 1(b)), and the third lens group 503, and forms a subject image on the imaging plane of the image sensor 101 in the camera body 100. The first lens group 601 has a reflective optical system. The detailed configuration will be described later. The second lens group 502 is a variator that moves back and forth along the optical axis OA (optical axis direction) to change the magnification. The third lens group 503 is a focus lens that moves back and forth in the optical axis direction to adjust the focus. The third lens group 503 is driven by a focus drive unit 504 that uses a stepping motor or the like.

[0017] As shown in FIG. 1B, the aperture 505 provided only in the lens device 500 is configured with a plurality of aperture blades for adjusting the amount of light incident on the lens device 500. The aperture drive unit 506 drives the aperture blades to narrow the aperture until a predetermined shooting F-number is reached. In the reflection optical system of FIG. 1A, the aperture 505 and the aperture drive unit 506 are not provided because it is difficult to install them. The lens CPU 507 communicates with the camera CPU 104 via the lens side communication terminal 508 and the camera side communication terminal 113, transmits and receives various information, and drives and controls the focus drive unit 504 and the aperture drive unit 506 based on commands from the camera CPU 104.

[0018] The zoom range and maximum aperture F-number of the lens device 500 are designed according to the intended shooting purpose, but the lens device 600 having a reflective optical system is configured so that the maximum aperture F-number is a constant value regardless of the zoom state or focus state. Meanwhile, in the lens device 600, the distance between the exit pupil and the imaging surface, the so-called exit pupil distance, changes according to the focus state.

[0019] Next, the first lens group 601 shown in FIG. 1(a), that is, a lens having a reflective optical system, will be described with reference to FIG. 2. FIG. 2 is a schematic diagram of a reflective optical system. In FIG. 2, a solid line 604 on the left is an object, and a dotted line indicates a light ray emitted from one point of the object 604. The light emitted from the object 604 passes through lens 601A and is collected, and is reflected by lens 601B. Furthermore, the light reflected and refracted by lens 601C passes through lens 601B, passes through lens 601E, passes through third lens group (focus lens) 503, and is then imaged on the imaging surface of image sensor 101. Lens 601A is a first lens through which light passes before being reflected by the reflective optical system, and lens 601E is a second lens through which light passes after being reflected by the reflective optical system.

[0020] Lenses 601B and 601C are reflective lenses that reverse and reflect the optical path in Fig. 2, and constitute a reflective optical system. Lens 601B is a first reflective lens, and lens 601C is a second reflective lens. Lens 601C has a light shielding portion 601D attached to the surface opposite the optical path (on the subject surface side). In this way, by folding back the optical path inside first lens group 601, it is possible to obtain an image with a long focal length on the imaging surface, despite its small size.

[0021] Next, ring blur will be described with reference to Figs. 3(a) and (b). Figs. 3(a) and (b) are comparative diagrams between general blur (normal blur) and ring blur, with Fig. 3(a) showing general blur and Fig. 3(b) showing ring blur. In an optical system including a reflective optical system, a light shielding portion 601D is disposed in the light receiving area of ​​the light beam, so that the blur shape when the subject is not imaged on the image sensor 101 becomes ring-shaped (ring blur). As shown in Figs. 3(a) and (b), while normal blur is a uniform point image, ring blur has a light-shielded center and is not of good quality. In particular, the reason why the quality of ring blur is not good is that a sharp difference in image quality occurs inside the ring.

[0022] One of the purposes of this embodiment is to reduce ring blur in an optical system (imaging optical system) including a reflective optical system. For this reason, this embodiment uses an optical adjustment layer having a transmittance distribution layer or a reflectance distribution layer that is rotationally symmetric around the optical axis OA. The optical adjustment layer has a maximum value of transmittance or reflectance at a position away from the optical axis OA, thereby reducing a sudden image quality difference inside the ring blur.

[0023] Next, referring to Fig. 4 and Fig. 5(a) and (b), a case where a transmittance distribution layer is used as the optical adjustment layer will be described. Fig. 4 shows an example of an optical adjustment layer. As shown in Fig. 4, the optical adjustment layer is a transmittance distribution layer 401 that is rotationally symmetric about the optical axis OA. The inner edge 402 is a region corresponding to the light shielding portion 601D, and no light beam passes through the region inside the inner edge 402. The outer edge 403 corresponds to the maximum diameter of the light beam, and the entire light beam is included inside the outer edge 403.

[0024] FIG. 5(a) is an example of the transmittance distribution of the optical adjustment layer. In FIG. 5(a), the dashed line indicates the transmittance distribution when there is no optical adjustment layer, and the solid line indicates the transmittance distribution when there is an optical adjustment layer. In FIG. 5(a), the horizontal axis indicates the distance r from the optical axis OA (center of the optical axis) normalized over the entire light beam, and the vertical axis indicates the transmittance. As shown in FIG. 5(a), the transmittance of the optical adjustment layer in this embodiment has a maximum value Tmax at a position r1 away from the optical axis OA (i.e., a position different from the optical axis OA) (the transmittance is maximum at the position r1). The inner edge 402 is at a position of r=0.2, and the transmittance maximum value Tmax is shown between the inner edge 402 and the outer edge 403. Here, the change in transmittance before and after the inner edge 402 is related to the image quality inside the ring blur, so it is desirable that the change be gradual.

[0025] FIG. 5(b) is an example of the transmittance distribution in the entire optical system, where the transmittance at the inner edge where there is no light is set to 0. In FIG. 5(b), the dashed line indicates the transmittance distribution when there is no optical adjustment layer, and the solid line indicates the transmittance distribution when there is an optical adjustment layer. In FIG. 5(b), the horizontal axis indicates the distance r from the optical axis OA (center of the optical axis) normalized over the entire light beam, and the vertical axis indicates the transmittance. When there is no optical adjustment layer, the transmittance is constant, so the change in transmittance before and after the inner edge becomes steep. On the other hand, when an optical adjustment layer is provided, the change in transmittance before and after the inner edge becomes gradual. From the viewpoint of securing the amount of light, it is preferable that the maximum value of the transmittance and the transmittance at the outer edge are higher than the transmittance at the inner edge.

[0026] When using a transmittance distribution layer as the optical adjustment layer, it is preferable to provide it in a lens group whose light passing region is as independent as possible of the image height of the image sensor 101. For example, it is preferable to provide the transmittance distribution layer in lens 601A, which is the first incident lens to the optical system (first lens group 601) in FIG. 2, or in lens 601E after all reflections are completed.

[0027] Next, referring to FIG. 6, a case where a reflectance distribution layer that is rotationally symmetric about the optical axis OA is used as the optical adjustment layer will be described. The reflectance distribution layer is preferably provided in the reflecting portion of the reflection optical system. FIG. 6 shows an example of a reflectance distribution when a reflectance distribution layer is used as the optical adjustment layer. In FIG. 6, the horizontal axis indicates the distance r from the optical axis OA (optical axis center) normalized over the entire light beam, and the vertical axis indicates the reflectance. As shown in FIG. 6, the reflectance distribution layer of this embodiment has a maximum value Rmax at a position r2 away from the optical axis OA (i.e., a position different from the optical axis OA) (the reflectance is maximum at the position r2). The inner edge 402 is at a position of r=0.2, and has a maximum value of reflectance between the inner edge 402 and the outer edge 403. Here, since the change in reflectance before and after the inner edge 402 is related to the image quality inside the ring blur, it is preferable that the change in reflectance is gradual. From the viewpoint of ensuring the amount of light, it is preferable that the maximum value of the reflectance and the reflectance at the outer edge 403 are higher than the reflectance at the inner edge 402 .

[0028] When a reflectance distribution layer is used as the optical adjustment layer, it is preferable to provide it in the reflecting portion of the reflective optical system. For example, the reflectance distribution layer is preferably provided in the lens 601B or the lens 601C in FIG.

[0029] As described above, the optical system of this embodiment includes a reflective optical system (lenses 601B and 601C) and an optical adjustment layer including a transmittance distribution layer or a reflectance distribution layer that is rotationally symmetric about the optical axis OA. The optical adjustment layer has a maximum value (Tmax, Rmax) of the transmittance or reflectance at a first position (a position at a distance r1 or r2 from the optical axis) different from the optical axis.

[0030] Preferably, the optical adjustment layer includes a transmittance distribution layer, and the maximum value (Tmax) of the transmittance is higher than the transmittance at a second position (inner edge 402) corresponding to the end of the light shielding portion 601D in the transmission region of the transmittance distribution layer. Also preferably, the transmittance at the second position in the transmission region of the transmittance distribution layer is lower than the transmittance at a third position (outer edge 403) corresponding to the maximum diameter of the light beam. Also preferably, the position at which the rate of change of the transmittance (slope of the transmittance distribution) is maximum is between the first position and the second position.

[0031] Preferably, the optical adjustment layer includes a reflectance distribution layer, and the maximum value of the reflectance (Rmax) is greater than the reflectance at a second position corresponding to the end of the light-shielding portion in the reflection region. Also preferably, the reflectance at the second position in the reflection region of the reflectance distribution layer is lower than the reflectance at a third position corresponding to the maximum diameter of the light beam. Also preferably, the position at which the rate of change of the reflectance (slope of the reflectance distribution) is maximum is between the first position and the second position.

[0032] According to the present embodiment, it is possible to provide an optical system and an imaging device capable of reducing ring blur when a reflective optical system is used.

[0033] 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.

[0034] For example, the configuration of this embodiment may be adopted in combination with an imaging device in which the performance is affected by a point image shape such as an imaging surface phase difference element or a light field. In addition, the present invention is effective for an optical system including a reflective optical system, and may be either an interchangeable lens or an optical system integral with a camera body. [Explanation of symbols]

[0035] 401 Optical adjustment layer 601B, 601C Lens (Reflection Optical System)

Claims

1. A reflective optical system; an optical adjustment layer including a transmittance distribution layer that is rotationally symmetric about an optical axis; A light-shielding portion, the optical adjustment layer has a maximum value of transmittance at a first position different from the optical axis, The optical system according to claim 1, wherein the maximum value of the transmittance is higher than the transmittance of light at a second position corresponding to an end of the light blocking portion in the transmissive region of the transmittance distribution layer.

2. a first lens through which light passes before being reflected by the reflective optical system; a second lens through which the light reflected by the reflection optical system passes, The optical system according to claim 1 , wherein the optical adjustment layer is provided on the first lens or the second lens.

3. the reflective optical system includes a first reflective lens and a second reflective lens; the first reflecting lens reflects light that has passed through the first lens, the second reflecting lens reflects the light reflected by the first reflecting lens and passing through the first lens, The optical system according to claim 2 , wherein the light blocking portion is provided on the second reflecting lens.

4. 4. The optical system according to claim 1, wherein the transmittance at the second position in the transmission region of the transmittance distribution layer is lower than the transmittance at a third position corresponding to a maximum diameter of the light beam.

5. 5. The optical system according to claim 1, wherein the position at which the rate of change of the transmittance is maximum is between the first position and the second position.

6. A reflective optical system; an optical adjustment layer including a reflectance distribution layer that is rotationally symmetric about an optical axis; A light-shielding portion, the optical adjustment layer has a maximum value of reflectance at a first position different from the optical axis, The optical system according to claim 1, wherein the maximum value of the reflectance is greater than the reflectance of light at a second position in a reflective area that corresponds to an end of the light-shielding portion.

7. The optical system according to claim 6 , wherein the optical adjustment layer is disposed in the reflective optical system.

8. the reflective optical system includes a first reflective lens and a second reflective lens; The optical system according to claim 7 , wherein the optical adjustment layer is provided on the first reflecting lens or the second reflecting lens.

9. The optical system according to claim 8 , wherein the light blocking portion is provided on the second reflecting lens.

10. 10. The optical system according to claim 6, wherein the reflectance at the second position in the reflective region of the reflectance distribution layer is lower than the reflectance at a third position corresponding to a maximum diameter of a light beam.

11. 11. The optical system according to claim 6, wherein the position at which the rate of change of the reflectance is maximum is between the first position and the second position.

12. 12. The optical system according to claim 1, wherein the optical system is detachable from a camera body.

13. An imaging element; An imaging device comprising the optical system according to claim 1 .

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