JP2018151549A - Diffuser panel and single lens reflex camera using the same at focusing screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diffuser panel with which a subject image (real image) is easier to observe, and a single lens reflex camera using the diffuser panel at a focusing screen.SOLUTION: A diffuser panel is configured to form an image of a real image so as to observe the real image through an eyepiece optical system. The diffuser panel includes: a light scattering surface obtained by planarly filling in at least two regular kinds of microlenses having different outer peripheral shape in planer view as a repeating unit; and an annular face formed on the opposite side of the light diffusion surface. A planarly filling type of the microlenses is non-cyclic filling.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a diffusing plate having a light diffusing surface composed of non-periodically arranged microlenses and a single-lens reflex camera using the diffusing plate for a focusing screen.

  In a single-lens reflex camera, an image is formed by forming an image on an image sensor with a photographing lens. In an optical system of a single-lens reflex camera, a mirror is disposed between a photographic lens and an image sensor, and is formed by a photographic lens on a focusing screen (focus plate) disposed at a position equivalent to the image sensor via the mirror. Framing and focusing are performed by observing the image through the viewfinder optical system. At the time of shooting, the mirror is temporarily retracted from the light path of the imaging optical system, so that an image is formed on the image sensor in the same state as the image formed on the focusing screen, and shooting is performed.

  In order to confirm an image projected on the focusing screen with a finder optical system, a surface (light diffusion surface) having a function of diffusing light is formed on the surface of the focusing screen by an uneven shape called a mat surface. When an image is formed on the focusing screen in focus with the taking lens, a very clear image is observed, but when an image is formed in a defocused state, focusing is performed. A blurred image is observed due to the effect of the matte surface of the screen. By adjusting the focus adjustment mechanism of the photographic lens so that the image can be clearly seen from the blurred state, the photographic lens can be focused (focused). The image blur on the focusing screen is an indicator of the ease of focusing and the degree of blur in the defocused part of the actual image, so the light diffusion characteristics of the matte surface determine the performance of the SLR camera's viewfinder. It is an important factor.

  The uneven surface used for the matte surface of the focus plate is a diffused surface formed by a technique called “sand rub” that rubs the surface with sand-like particles to form unevenness or “sand blast” that blows particles to roughen the surface. Further, a diffusion surface using a microlens array is already known.

  The method of forming a diffused surface by sand blasting or sand blasting (a technique of rubbing the surface with sand-like particles or spraying particles) is a method that has been widely used in the past, and (a) a simple method The diffused surface can be processed. (B) Since the angular distribution of diffused light is continuous (smooth) and Gaussian distribution, the defocusing is natural and the diffusivity is good and focusing is easy. c) Since the processed uneven shape has no periodicity and is random, it has a feature that moire is hardly generated with a Fresnel lens formed on the opposite surface of the diffusion surface (having concentric periodicity).

  However, the diffusion surface formed by sanding or sandblasting has a low degree of freedom in processing, and it is difficult to arbitrarily change the uneven shape and its distribution depending on the processing conditions, and it is difficult to accurately control it. When processed so as to give a high diffusivity, not only a shape with appropriate diffusibility, but also a shape with low diffusivity (a shape with a small uneven slope) or a shape with a large diffusivity (a shape with a steep uneven surface) ) Are mixed. In a portion having a shape with high diffusibility, a phenomenon occurs in which light is bent at a large angle and escapes outside the pupil of the viewfinder, and the portion is locally darkened in an image confirmed by the viewfinder. As a result, a loss occurs in the amount of light obtained through the viewfinder, the viewfinder image becomes dark, and such locally dark portions are randomly present two-dimensionally. And there is a problem that roughness occurs.

  A diffusion surface using a microlens array is the most popular method in recent years. A microlens array is a two-dimensional array of minute lens-shaped irregularities, typically a square array of lenses with a square outer diameter and a plane-filled lens with a hexagonal outer diameter. is there. Diffusion surface using microlens array is easy to design and manufacture because of (a) repeating pattern of unit structure, (b) adjustment of simple parameters (lens arrangement, period, height, radius of curvature, etc.) (C) Light utilization efficiency is high and the viewfinder image is bright. (D) Regular patterns are arranged periodically, so that the lens arrangement interval is regular and random at the lens boundary. The light scattering effect is almost uniform in two dimensions, so that there is little graininess, and (e) the manufacturing method has been established and can be manufactured with high accuracy and good reproducibility. Have.

  However, since the diffusing surface using the microlens array has a two-dimensional periodic structure, it functions as a diffraction grating, and the light diffusing characteristics are discrete. As a result, a phenomenon called multi-line blur occurs in which the image when the image is out of focus appears to be multiplexed, the blur becomes unnatural, and it is difficult to focus. Further, since the angle of diffraction differs depending on the wavelength of light, color unevenness occurs in the image. In general, a Fresnel lens is formed on the opposite surface (back surface) of the matting surface of the focusing screen in order to give the lens function. There is a problem in that moire is generated between the arranged microlens array and the Fresnel lens, and the quality of the finder image is deteriorated.

  In recent years, a diffuser plate of a type in which randomness is imparted to the arrangement and shape of the microlens array has been proposed in order to improve the adverse effects caused by the periodicity of the arrangement of the microlens array. For example, by giving randomness (fluctuation) to the arrangement of the microlens array and the outer peripheral shape, the effect as a light diffraction grating can be reduced, so that the discrete diffusion characteristics are improved and the natural blurring is improved. This is effective in that it is obtained and color unevenness is reduced. Moreover, it is possible to reduce the moire generated between the microlens array and the Fresnel lens by reducing the periodicity of the lens arrangement.

  However, by introducing randomness in the arrangement and shape of the microlens array, the distance between the lenses is not constant, and a portion where the distance is small and a portion where the distance is large are formed. Since the lens tilt angle at the boundary between the lenses becomes small at the position where the lens interval is small, the light scattering effect is reduced. At locations where the distance between the lenses is large, the angle of inclination of the lenses at the boundary between the lenses increases, which increases the scattering effect. Like the diffused surface formed by sand slide or sand blast, the incident light is bent at a large angle and the viewfinder pupil Escape to the outside and the area will become dark locally. As a result, there is a problem that the finder image becomes dark because graininess or roughness is generated in the finder image, or a loss occurs in the amount of light obtained through the finder.

As mentioned above, as a typical basic performance required as a focus plate,
1) The viewfinder image is bright,
2) The blur is natural and easy to focus on (less adverse effects (multi-line blur, color unevenness) due to diffraction phenomenon),
3) Less graininess and
4) There are four factors such as the fact that moire is less likely to occur. However, since these elements include those that are in a trade-off relationship with each other, it is difficult to satisfy all of them simultaneously.

  Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-004907) discloses that when microlenses are periodically arranged, the direction of diffracted light is limited to a specific direction, resulting in unnatural blur or when used in combination with a Fresnel lens. In order to eliminate the phenomenon that moire occurs due to interference with the ring zone structure of the Fresnel lens, the basic pattern is the case where the microlenses are regularly arranged, and the apex position of the microlens is the basic pattern A microlens array is disclosed in which microlens arrays are randomized so as to be non-uniformly distributed within a range having a certain radius from the apex position.

  However, since the microlens array described in Patent Document 1 basically has a configuration in which randomness (fluctuation component) is imparted to each regularly arranged microlens, a sufficiently large fluctuation amount is imparted. Otherwise, even if it looks random locally, periodicity remains in the arrangement of microlenses in a macro manner. On the other hand, if the amount of fluctuation is excessively large, the alignment of the adjacent lenses becomes unreasonable, so that a phenomenon such as graininess, roughness, and finder image darkening occurs, and a very large randomness cannot be given. For this reason, although the method described in Patent Document 1 has an effect of reducing the unnaturalness of blurring due to moire and diffraction and the effect of reducing color unevenness to some extent, it is possible to impart randomness enough to eliminate these to the lens arrangement. Can not. Moreover, since the outer peripheral shape of each microlens (the shape of the figure formed by the boundary line with the adjacent microlens) has randomness (not determined), control the optical characteristics of each microlens. Is difficult.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2005-221516) discloses a lens whose outer peripheral shape is a polygon including an odd-numbered polygon for the purpose of reducing the discreteness of the diffusion characteristic caused by the diffraction of light generated by the periodicity of the lens arrangement. Discloses a diffusion plate that is two-dimensionally arranged so as not to overlap each other. Although the diffuser plate described in the cited document 2 has periodicity in the lens arrangement, the periodicity of the lens is complicated by mixing the period and orientation of a plurality of different lens arrangements as a diffraction grating. By multiplexing the period and direction of the light and multiplexing the angle and direction at which the diffracted light is generated, it is possible to reduce the discreteness of the diffusion characteristics, and to prevent the occurrence of multi-line blur and color unevenness. It describes that a natural blur can be realized. In addition, since randomness is not introduced in the shape and period of the lens, the distance and alignment of the boundary between the lenses are constant, and there are places where the lens tilt is locally reduced or increased. Therefore, there is little graininess and it is bright.

  However, since the diffusion plate described in Patent Document 2 is configured by periodically arranging polygonal microlenses including odd-numbered polygons, the pattern obtained by these microlenses remains periodic. In addition, unnatural blur and color unevenness due to moire and diffraction cannot be sufficiently removed.

  Patent Document 3 (Japanese Patent Application Laid-Open No. 2002-243923) discloses a penrose tile pattern composed of two rhombuses as a reflector that does not generate diffracted light when used in a reflective or transflective liquid crystal display panel. A reflecting plate is disclosed in which a concavo-convex structure in which a decagon that appears periodically is formed as a convex portion or a concave portion is aperiodic.

  Patent Document 4 (Japanese Patent Laid-Open No. 2007-41261) discloses an optical element that does not generate moire fringes with a liquid crystal display device by using a Penrose tile pattern having an aperiodic structure in a two-dimensional direction. doing.

  Patent Document 5 (Japanese Patent Laid-Open No. 2015-210615) discloses a light-transmitting conductive material that does not generate moiré even when superimposed on a liquid crystal display, has good visibility, and has high reliability. A combination of Penrose tiles, squares, equilateral triangles, and non-periodic plane-filled figures with three parallelograms with angles of 30 ° and 150 °, “Gilly” patterns used as designs in medieval Islam, etc. The structure using the metal pattern formed by the mesh shape which consists of an aperiodic filling figure is described.

  The configuration using the Penrose tile disclosed in Patent Documents 3 to 5 is a Fresnel lens (concentric circular shape) in that the use is not a light diffusing plate and the target liquid crystal display panel has a lattice-like period. This is different from the structure of a focusing screen having a period. In addition, these prior technologies aim to individually reduce the effects of diffraction and moire when used in liquid crystal display panels. 1) The viewfinder image is bright like the focusing screen of a single-lens reflex camera. , 2) The nature of the blur is easy and the focus is easy (the effect of diffraction phenomenon (multi-line blur, color unevenness) is small), 3) The graininess is small, and 4) Moire is hard to occur It is not considered to solve a plurality of off-state issues simultaneously.

JP 2003-004907 A JP 2005-221516 A JP 2002-243923 A JP 2007-41261 A JP-A-2015-210615

  Accordingly, an object of the present invention is to provide a diffuser plate in which a subject image (real image) is easy to see and a single-lens reflex camera using the diffuser plate as a focusing screen.

  As a result of diligent research in view of the above object, the present inventors have found that the above problems can be solved by a diffusion plate having the following configuration, and have arrived at the present invention.

  That is, the diffusing plate of the present invention is a diffusing plate that forms the real image in order to observe the real image through the eyepiece optical system, and repeats at least two types of regular microlenses having different outer peripheral shapes in plan view. A light scattering surface formed by plane filling as a unit and an annular surface formed on the opposite side of the light diffusion surface are provided, and the plane filling mode of the microlens is aperiodic filling.

  The diffusing plate of the present invention makes it easy to see a subject image (real image), and is particularly suitable for a focusing screen of a single-lens reflex camera.

It is a schematic cross section showing an example of a single-lens reflex camera. It is a schematic cross section which shows an example of a focusing screen. It is a schematic diagram which shows the light-diffusion surface which used the micro lens array as a fine unevenness | corrugation. (a) Schematic diagram showing a pattern of a microlens array filled with hexagonal lenses, (b) Schematic diagram showing a pattern of a Fresnel lens, and (c) A state in which the microlens array and the Fresnel lens are overlaid. It is a schematic diagram. (a) A schematic diagram showing a pattern of a microlens array in which randomness is introduced into the lens period, and (b) a schematic diagram showing a state in which the microlens array of (a) and a Fresnel lens are overlaid. It is a schematic diagram which shows the cross section of the micro lens array for demonstrating the relationship between the periodicity of a lens, and a lens inclination angle. (a) The schematic diagram which shows the pattern of the micro lens array of patent document 1, and (b) The schematic diagram which shows the state which piled up the micro lens array and Fresnel lens of (a). (a) the first rhombus (thick rhombus) penrose tile, (b) the second rhombus (thin rhombus) penrose tile, and (c) the first rhombus and the second rhombus aperiodically It is a schematic diagram which shows an example of the Penrose tiling which is arranged in a row. (a) A schematic diagram showing a pattern of a microlens array produced by Penrose tiling in FIG. 8 (c), and (b) a schematic diagram showing a state where the microlens array and the Fresnel lens are overlaid in (a). is there. An example of (a) a dart-shaped quadrilateral penrose tile, (b) a kite-shaped quadrilateral penrose tile, and (c) a dart-shaped quadrilateral and a kite-shaped quadrilateral non-periodically arranged penrose tiling. It is a schematic diagram. (a) Schematic diagram showing the pattern of the microlens array produced by Penrose tiling in FIG. 10 (c), and (b) Schematic diagram showing the state in which the microlens array and the Fresnel lens are overlaid in (a). is there.

[1] Single-lens reflex camera As shown in FIG. 1, a single-lens reflex camera 1 includes a camera body 101, an opening 102 for taking light from a subject into the camera body 101, and a lens barrel connected to the opening 102 103. The lens barrel 103 has a photographic lens 104 disposed therein. The camera body 101 is disposed between an image sensor 105 (or a film) that converts light from a subject into an electrical signal, and between the image sensor 105 and the photographing lens 104, and the light from the subject is placed on the image sensor 105 side and the viewfinder 106. The finder 106 is arranged at a position equivalent to the image sensor 105, and a focusing screen 108 for forming incident light, and an image of the focusing screen 108 as an eyepiece And a pentaprism 110 for guiding to 109.

  The main mirror 107 is arranged to reflect the light from the subject and guide it to the viewfinder 106 side when not photographing, and the photographer 111 observes the image formed by the photographing lens 104 through the viewfinder 106 and performs framing. And focusing. The main mirror 107 is retracted outside the photographing optical path during photographing, forms an image on the image sensor 105 in a state equivalent to the image formed on the focusing screen 108, and immediately after the image sensing element 105 is exposed, the photographing optical path The mechanism returns to the inside and guides the subject light to the viewfinder 106 side.

  In order to confirm the image projected on the focusing screen 108 with the finder 106 optical system, one surface of the focusing screen 108 has a fine surface called a mat surface 112 for diffusing light, as shown in FIG. Concavities and convexities 113 are formed, and light is diffused by a refraction effect, a diffraction effect, and the like by the fine concavities and convexities 113. The light diffusion characteristics are determined by the shape and arrangement of the irregularities. A Fresnel lens 114 is formed on the other surface of the focusing screen 108 in order to give a function of a condenser lens.

  When the image formed by the photographic lens 104 is formed on the focusing screen 108 in a focused state, the image looks very clear, but the image is formed out of focus (defocused). In this case, the image appears to be blurred due to the influence of the matte surface of the focusing screen 108, and the greater the defocus, the greater the blur. By adjusting the focus adjustment mechanism of the photographic lens 104 from a blurred image to a clearly visible state, the photographic lens can be focused (focused).

  At this time, the greater the degree of light diffusion, the more noticeable the blur of the viewfinder image becomes when the photographic lens 104 is out of focus, so it is easier to find the in-focus condition and the result is easier to focus on. . However, if the diffusion angle becomes larger than necessary, the diffused light escapes out of the pupil of the finder 106, so that the amount of light obtained through the finder 106 is lost and the finder image becomes dark. In addition, when there is a portion where the diffusion angle is locally large, a local light amount decrease occurs, so that a bright place and a dark place are generated in the finder image, and as a result, graininess and roughness are generated.

  Since the matting surface of the focusing screen 108 is disposed at a position equivalent to the image sensor 105 via the main mirror 107, the image formed on the focusing screen 108 is substantially equivalent to the image actually captured by the image sensor. Therefore, it is possible to adjust the focus of the image obtained by the image sensor 105 and check the degree of blur according to the state of the image on the focusing screen 108. The image blur on the focusing screen 108 is an index of ease of focusing and the degree of blur in the defocused part of the image that is actually shot, so the light diffusion characteristics of the matte surface are the same as the performance of a single-lens reflex finder. It is an important factor to decide.

  As the mat surface 112 of the focusing screen 108, a technique called “sand rub” or “sand blast” has been used in many cases, but in recent years, a technique using a microlens array has become mainstream. Since the microlens array has an irregular shape having regularity or periodicity to some extent, it is easy to design and control the light diffusion effect (lens effect, diffraction effect, scattering effect) and has high manufacturing suitability. The single-lens reflex camera of this invention is comprised using the diffusing plate of this invention mentioned later for a focusing screen.

[2] Diffuser
(1) Configuration A focusing screen used in a single-lens reflex camera or the like is a diffusion plate having a light diffusion surface called a mat surface on one surface and a Fresnel lens on the other surface. By forming a real image on the diffusion plate, the real image is observed at an equal magnification or enlarged through an eyepiece optical system. The light diffusing surface is conventionally constituted by a concavo-convex structure formed by sanding or sandblasting, a regularly arranged microlens array, or a microlens array in which randomness is introduced into the lens period. The diffusion plate is planarly filled with at least two types of fixed microlenses having different outer peripheral shapes in plan view as the light diffusing surface, and the planar filling form is aperiodic filling. To do. Here, the “peripheral shape” of a microlens is a shape of a figure formed by a boundary line with an adjacent microlens, and “at least two types of regular microlenses” are two or more types. This means a microlens consisting of a certain number of types (the number of types is fixed), and “planar filling” means arranging (filling and arranging) without gaps on a plane. "Is filling aperiodically. In the present application, “period” means a spatial period, that is, synonymous with pitch.

  In the diffuser plate of the present invention, when the outer peripheral shape of the standard microlens is considered as a figure, the number of types of the figure is constant in the region of any position in the light diffusion surface, and the arrangement of the figures It has a diffusing surface composed of a pattern whose shape is aperiodic. Here, an arbitrary area is an area that can be said to include a statistically sufficiently large number of microlenses within the area. When the diffuser plate is used for a focusing screen of a single-lens reflex camera, 1 mm × 1 If an area of about mm or more is defined, it can be said that a sufficiently large number of microlenses are included. If the area is about 1 mm × 1 mm or more, the number of types of figures is constant regardless of whether it is 2 mm × 2 mm or 3 mm × 3 mm. Further, the ratio of the number of each type of microlens is preferably substantially constant.

(2) Light diffusing surface The light diffusing surface formed on the diffusing plate of the present invention is a so-called microlens array formed by plane filling so that lenses having a polygonal outer shape do not overlap, and the form of the plane filling Is aperiodic filling. In the present invention, the fact that the form of planar filling is aperiodic filling means a pattern that cannot be superimposed on itself by parallel movement. The filling by non-periodic deformation of the periodic filling, for example, the one in which randomness or fluctuation is added to the periodic filling is not considered as non-periodic here. Therefore, the non-periodic filling is not due to the introduction of randomness into the arrangement or shape of one or more types of polygons, but a specific figure that does not have periodicity as the outer peripheral shape of the lens, It is obtained by adopting a special arrangement method. With such a non-periodic arrangement, while maintaining the “brightness of the viewfinder image” that is a feature of the microlens array, at the same time, the “blurring is natural and easy to focus” and “graininess” "Small" and "Mire is less likely to occur" at the same time.

  When a diffusing plate configured as a light diffusing surface with a microlens array formed by periodically filling a lens having a polygonal outer shape as a light diffusing surface is used as a focusing screen, the length of one side of each polygon is 5 to 50 μm. Preferably there is. When the length of one side is less than 5μm, the diffraction effect becomes large and the light diffusion characteristics become discrete, so the blurring becomes unnatural, or the color of the image varies depending on the angle of diffraction depending on the wavelength of light. Unevenness may occur. When the length of one side is more than 50 μm, the shape of each lens can be recognized when the matte surface is observed with the finder optical system, so that it is not suitable as a finder.

  The microlens array having such a configuration preferably has a light diffusion angle of ± 5 ° to ± 20 °, and more preferably ± 5 ° to ± 15 °. The diffusion angle of the matte surface required as a focusing screen has a correlation with the release F value of the photographic lens, and the release F value of a general photographic lens for a single lens reflex camera is about F1.4 to F5.6. Therefore, ± 5 ° to ± 20 ° is required as the corresponding diffusion angle. When the diffusion angle is larger than ± 20 °, the finder image becomes dark because a large proportion of diffused light escapes from the viewfinder pupil. If the angle is less than ± 5 °, the scattering effect is small and the blurring is insufficient. Actually, since a lens of F1.4 is not often used, in reality, a diffusion angle of about ± 5 ° to ± 15 ° is often required. A microlens array having a light diffusion angle of ± 5 ° to ± 20 ° can also be defined by an F value. In the present invention, the F value is preferably about F1.4 to F5.6.

  When the diffusing plate is used as a focusing screen, its thickness is preferably 1 to 3 mm. Precise focusing with a focusing screen is premised on the mat surface having flatness. A focusing screen is often manufactured by molding a resin material into a flat plate shape by injection molding. However, if the thickness is thin, warping and distortion are likely to occur, and a certain amount of thickness is required to obtain flatness. . In addition, a certain level of thickness is required to ensure the mechanical strength of the resin flat plate to maintain its flatness. For the above reasons, the thickness of the focusing screen is preferably about 1 mm or more. The focusing screen is arranged at a position equivalent to the image sensor via the main mirror. However, if the thickness is thick, the main mirror may interfere with the arrangement or the arrangement of the main mirror may be limited. Since it is necessary to widen the distance between the main mirror and the main mirror, it becomes an obstacle to downsizing the configuration. For the above reasons, the thickness of the focusing screen is preferably about 3 mm or less.

  As shown in FIG. 3, a conventional light diffusing surface using a microlens array is obtained by two-dimensionally arranging minute lens-like fine irregularities, and the light diffusion effect by the lens and the periodicity of the lens arrangement. The light is scattered by utilizing the diffraction effect of light accompanying the. In order to efficiently arrange the lenses in a two-dimensional manner, the microlens array is an array in which square lenses with a square outer diameter are arranged in a square, and as shown in the figure, hexagonal lenses with a flat surface are filled (honeycomb structure). The sequence to do is common.

  As described above, such a conventional microlens array has features such as easy design, fabrication, and control of diffusion characteristics, a bright finder image, less graininess and roughness, but periodicity and regularity. Due to the diffraction phenomenon caused by the fine structure having the property, the phenomenon that is called multi-line blur when the image is out of focus appears to be multiplexed or color unevenness occurs in the image. It tends to be unnatural and difficult to focus.

(3) Fresnel Lens FIG. 2 shows a conventional focusing screen 108. A Fresnel lens 114 is formed on the surface of the focusing screen 108 opposite to the diffusion surface (mat surface). Since the zones of the Fresnel lens 114 are formed at equal intervals, when the fine irregularities 113 on the mat surface are periodic and the period (pitch) is close to the pitch of the zones of the Fresnel lens 114, an interference fringe called moire Occurs to degrade the viewfinder image. In order to suppress the occurrence of moiré, the pitch of the annular zone of the Fresnel lens is desirably set slightly larger than the period of the fine unevenness 113 when the fine unevenness 113 of the mat surface is periodic, specifically, the fine unevenness 113. About 1.5 to 2.5 times the period is desirable. Therefore, the pitch of the annular zone of the Fresnel lens is preferably 10 to 100 μm. Since the Fresnel lens also has a periodic structure, when the annular zone pitch is 10 μm or less, the light diffraction effect becomes remarkable and color unevenness occurs. Further, when the pitch of the annular zone is 100 μm or more, the annular zone can be visually recognized when the Fresnel lens is observed with the finder optical system, so that it is not suitable as a finder.

  Also in the present invention, a Fresnel lens similar to the Fresnel lens 114 formed on the focusing screen 108 of the conventional example shown in FIG. 2 can be used. It is preferable that the period of the annular zone of the Fresnel lens is 10 to 100 μm. Since the microlenses arranged on the light scattering surface of the diffusion plate of the present invention are non-periodic, basically, at any pitch of the annular zone of the Fresnel lens as compared with the conventional microlens array of periodic arrangement. Even so, it can be said that moire is unlikely to occur. However, the arrangement of the microlenses of the present invention is aperiodic as a whole, but since the fixed lenses having a certain size are filled with a plane, the lenses are regularly arranged locally. There may also be cases. Since the microlens of the present invention is non-periodic, the lens period cannot be defined. However, when the length of one side of the microlens is close to the pitch of the ring zone of the Fresnel lens, moire is likely to occur, and the ring of the Fresnel lens. It has been found that when the band pitch is about 1.5 to 2.5 times the length of one side of the microlens, the moire suppressing effect is high. In addition, if the pitch of the ring zone of the Fresnel lens is 10 μm or less, the light diffraction effect becomes remarkable and color unevenness occurs, and if the pitch of the zone is 100 μm or more, the ring zone of the Fresnel lens can be visually observed with the viewfinder. It becomes unsuitable as a finder because it can be recognized.

  Embodiments of a focusing screen using the conventional example and the diffusion plate of the present invention will be described below.

[Conventional example 1]
FIG. 4 (a) shows a pattern of a microlens array in which lenses having a hexagonal outer diameter are plane-filled (the same pattern as the microlens array of FIG. 3). In order to simulate the state of moiré that occurs when a light diffusing surface is formed on a transparent substrate using this microlens array and a Fresnel lens having a concentric ring zone is formed on the opposite surface, The microlens array pattern shown in FIG. 4 (a) and the Fresnel lens pattern shown in FIG. 4 (b) were superimposed. As a result, as shown in FIG. 4 (c), it can be seen that significant moire occurs due to interference between the microlens pattern having periodicity and the Fresnel lens pattern. Moire is a pattern that does not exist originally, so if the finder image has moire, the user feels uncomfortable.

[Conventional example 2]
As disclosed in Patent Document 1, by providing randomness (fluctuation) to the arrangement and shape of the microlens, some drawbacks when the microlens array is used as a light diffusion surface can be improved. When a light diffusing surface is formed using a microlens array that gives randomness (fluctuation) to the arrangement and shape of microlenses, the effect as a light diffraction grating can be reduced, so discrete diffusion The characteristics are improved, natural blurring is obtained, and color unevenness is reduced. Further, by reducing the periodicity of the lens arrangement, it is possible to reduce moire generated between the microlens array and the Fresnel lens as will be described below.

  FIG. 5 (a) shows a lens arrangement in which randomness (fluctuation) is imparted to the period by randomly shifting the center position of each lens of a microlens array in which a hexagonal lens is filled with a flat surface. (See FIG. 1 of Patent Document 1). When the microlens array introduced with randomness thus obtained and the pattern of the Fresnel lens having concentric annular zones shown in FIG. 4 (b) are superimposed, as shown in FIG. 5 (b). In addition, no significant moire is observed. It can be seen that the introduction of randomness reduces the periodicity of the microlens array pattern and reduces the occurrence of moire.

  However, the microlens array introduced with randomness as shown in FIG. 5 (a) is more noticeable in graininess and roughness than the microlens array in which lenses shown in FIG. 4 (a) are periodically arranged. I can see it coming. The cause of the noticeable graininess and roughness is as follows.

  FIG. 6 is a schematic diagram showing a cross section of a microlens array for explaining the relationship between lens periodicity and lens tilt angle. As shown in FIG. 6 (a), in the lenses arranged periodically, since the mutual lens interval is constant, the tilt angle of the lens at the lens boundary is also substantially constant. Therefore, the light diffusion characteristics on the plane are almost two-dimensionally uniform, so that the brightness of the obtained finder image also appears almost uniform in two dimensions. However, as shown in FIG. 6B, when randomness (fluctuation) is introduced into the microlens array, the distance between the lenses is not constant, and a portion having a large distance and a portion having a small distance are generated depending on the location. When the lens interval is large, the tilt angle of the lens becomes large at the boundary of the lens, so that the light is bent at a large angle and escapes outside the pupil of the finder, and the finder image at that portion becomes locally dark. Similar to the diffusing surface caused by sand slicking or sand blasting, relatively bright and dark places appear randomly two-dimensionally, causing graininess and roughness, and loss in the amount of light obtained through the viewfinder. The viewfinder image becomes dark.

  In the method of introducing randomness (fluctuation) into the lens arrangement, the effect of “reducing the adverse effects due to diffraction” and “reducing moire” increases as the amount of randomness is increased. There is a trade-off between increasing the intensity and decreasing the “finder brightness”. Therefore, it is difficult to solve all of these defects simultaneously by introducing randomness (fluctuation).

[Conventional Example 3]
In the case of a microlens array in which a lens with a square outer diameter is squarely arranged, or a microlens array in which a lens with a hexagonal outer diameter is plane-filled, the lens arrangement cycle is constant, and the orientation in which the lenses are periodically arranged Is limited, the angle and direction of diffraction of the diffracted light are limited, and the diffusion distribution is discrete. As a method of improving such a defect of the light diffusion plate of the micro lens array type, the periodicity of the lens arrangement is complicated to multiplex the period and direction of the diffraction grating, thereby reducing the discreteness of the diffusion characteristics. (Refer to Patent Document 2).

  FIG. 7 (a) shows a lens arrangement comprising two types of lenses, a pentagon and a quadrangle (see FIG. 1 of Patent Document 2). Since the microlens array having such a pattern has a complicated lens arrangement periodicity, the period and direction of the diffraction grating are also multiplexed, and the angle and direction at which the diffracted light is generated are superimposed and multiplexed. Therefore, the discreteness of the diffusion characteristic is reduced (Patent Document 2). As a result, it is considered that a multi-line blur and color unevenness can be prevented and a natural blur can be obtained. In addition, since randomness is not introduced in the shape and period of the lens, the distance between the lenses and the alignment of the lens boundary are constant, and there is no occurrence of a portion where the lens inclination becomes large. Less (see Fig. 7 (a)). Furthermore, it is considered that the viewfinder image does not become dark because of high light utilization efficiency.

  However, when the microlens array in which the periodicity of the lens arrangement shown in FIG. 7 (a) is complicated and the Fresnel lens pattern having concentric annular zones shown in FIG. As shown in (b), it can be seen that significant moire occurs. In this way, when a finite type of polygon is filled in a plane, the arrangement usually has a periodic pattern, and thus a strong moire occurs between the concentric Fresnel lenses.

Therefore, the microlens array described in Patent Document 2 is
1) The viewfinder image is bright,
2) The blur is natural and easy to focus on (less adverse effects due to diffraction (multi-line blur, color unevenness)), and
3) Although it has been resolved that there is little graininess,
4) It is not possible to solve the problem that moire is difficult to occur.

[Invention Example 1]
In the diffusion plate of the present invention, a special arrangement method called Penrose tiling is used as an example of realizing a light diffusing surface obtained by plane filling with at least two types of regular microlenses having different outer peripheral shapes in plan view as repeating units. Is mentioned. Penrose tiling is a plane filling method designed by the British physicist Roger Penrose, and the plane is overlapped according to the arrangement method of Penrose tiling using a figure made of polygons called Penrose tiles. In addition, it is known that a periodic pattern does not occur in the arrangement (the pattern becomes non-periodic) if it is filled without any gap.

  In the diffuser plate of the present invention, the outer peripheral shape of the microlens is a Penrose tile shape, and the lenses are arranged according to the Penrose tiling rules, so that the lens arrangement that would have been periodic in the past can be randomized. It was possible to make a non-periodic arrangement without introducing it.

  The figure used for the Penrose tiling is called the Penrose tile. In particular, (a) the first Penrose tiling configured with two types of rhombuses as Penrose tiles, and (b) the dart-shaped square The second Penrose tiling, which is composed of a kite-shaped square and a Penrose tile, is representative.

(a) First Penrose tiling Two types of rhombuses are configured as Penrose tiles. The first rhombus is shown in Fig. 8 (a) and the second rhombus is shown in Fig. 8 (b). . The first rhombus has an acute angle of 72 ° and an obtuse angle of 108 °, and the second rhombus has an acute angle of 36 ° and an obtuse angle of 144 °. The length of one side of the first rhombus is the same as the length of one side of the second rhombus. That is, the length of one side of the two rhombuses is the same length. The first rhombus is called “fat rhombus” and the second rhombus is called “thin rhombus”.

  A first Penrose tiling as shown in FIG. 8 (c) is obtained by planarly filling the first rhombus and the second rhombus. However, if these two types of rhombuses are used for arrangement, the arrangement is not necessarily aperiodic, and there are many cases where the arrangement is periodic. Such a periodic arrangement is not called Penrose tiling. That is, by using two types of rhombuses as Penrose tiles and arranging them according to a rule called a matching rule that avoids the appearance of simple repetition (forcing an aperiodic arrangement), Penrose tiling A non-periodic arrangement called is possible. As can be seen from FIG. 8 (c), the arrangement is aperiodic with no periodic pattern, although it is arranged with only two types of squares (diamonds).

  In this application, in the microlens array, the outer peripheral shape of the lens is two types of penrose tiles, “fat rhombus (fat)” and “skinned rhombus (thin)”, and they are arranged according to a rule called penrose tiling. As a result, an aperiodic array of microlens arrays was realized.

  FIG. 9 (a) shows a lens arrangement form in which a microlens is formed with a first rhombus and a second rhombus as outer peripheral shapes and is filled in a plane. Although there is a two-dimensional distribution of brightness due to the lens arrangement pattern, the lenses are ordered and filled with no gaps and no gaps, so there is a certain order in the spacing and alignment of each lens, and random elements are Therefore, there is no local increase in the lens spacing, or the location where the lens tilt is locally large. As a result, there are no local dark spots, which can cause graininess and roughness. Can be prevented.

  The first Penrose tiling is composed of lenses with only two types of square (rhombic) outer periphery, and is easy to design and manufacture, with simple parameters (period, height, radius of curvature, etc.) It is possible to easily control the diffusion characteristics by adjusting. By optimizing the desired diffusion characteristics, unnecessary diffused light can be reduced and the light utilization efficiency is increased, so that the viewfinder image can be brightened.

  FIG. 9 (a) shows a microlens array comprising the first Penrose tiling. FIG. 9B shows the state of moire generated when this microlens array is formed on the diffusing surface and the Fresnel lens having the concentric annular zone shown in FIG. 4B is formed on the opposite surface. Since the first Penrose tiling is formed by filling a polygon (two types of diamonds), the arrangement pattern includes azimuthal symmetry, and there is a slight moire probably due to it. As can be seen, since the lenses themselves are two-dimensionally arranged aperiodically, the occurrence of moiré is very well suppressed compared to a typical periodic microlens array. In FIG. 9 (b), it is assumed that one side of the rhombus of the two types of Penrose tiles is about 20 μm and the pitch of the Fresnel lenses is about 30 μm.

  Penrose tiling does not provide a continuous (smooth) angular distribution of diffused light as obtained from a completely random pattern because the lens arrangement is not a random arrangement, but the lens arrangement is not Since it is two-dimensionally non-periodic, generation of light diffraction can be efficiently reduced. In addition, due to the non-periodicity and potential azimuth symmetry resulting from filling two types of squares (diamonds), multiple non-uniformly (aperiodically) superimposed multiple azimuths Since a diffracted light distribution can be obtained, it is possible to improve a simple and discrete diffusion distribution with a limited azimuth and period as in a general microlens array in which ordinary polygons are periodically arranged. As a result, adverse effects such as multi-line blur and color unevenness due to discrete diffusion characteristics can be greatly reduced, so that the viewfinder image is naturally blurred and easy to focus.

Therefore, the microlens array consisting of the first Penrose tiling has the following four basic characteristics required for the focus plate:
1) The viewfinder image is bright,
2) The blur is natural and easy to focus on (less adverse effects due to diffraction phenomenon (multi-line blur, uneven color)),
3) Less graininess and
4) It is possible to satisfy at the same time that moiré is unlikely to occur.

(b) Second Penrose tiling Penrose tiling composed of two types of quadrature, a Dart-shaped quadrangle and a Kite-shaped quadrangle. As shown in FIG. 10, the four interior angles are 36 °, 72 °, 36 °, and 216 ° in order, and the kite-shaped square has four interior angles of 72 °, 72 °, 72, as shown in FIG. And the length of two sides (the shorter of the four sides) sandwiching the inner angle 216 ° of the dirt-shaped square is two sides (shorter of the four sides) sandwiching the inner angle 114 ° of the kite-shaped square Is equal to the length of The length of the two sides (the longer of the four sides) sandwiching the 72 ° inner angle of the dart-shaped quadrangle is the two sides (the longer of the four sides) sandwiching the 72 ° inner angle of the 114 ° inner angle of the kite-shaped quadrangle. ) Is equal to the length.

  Like the first Penrose tiling described above, these two squares are flat and free of overlap and gaps (to force a non-periodic arrangement) so as to avoid the appearance of simple repetition according to a rule called matching rules. 10C, a non-periodic arrangement called Penrose tiling is possible, as shown in Fig. 10 (c) .In the present invention, in the microlens array, the outer peripheral shape of the lens is divided into two types of Penrose tiles. The “dirt-shaped quadrangle” and the “kite-shaped quadrilateral” are arranged according to a rule called Penrose tiling, thereby realizing an aperiodic arrangement without a periodic pattern.

  FIG. 11 (a) shows a microlens array comprising the second Penrose tiling. FIG. 11B shows the state of moire generated when this microlens array is formed on the diffusion surface and the Fresnel lens having the concentric ring zone shown in FIG. 4B is formed on the opposite surface. As with the first Penrose tiling, the second Penrose tiling has two-dimensional non-periodic arrangement of lenses, so moiré is generated compared to a typical periodic microlens array. It can be seen that is suppressed very well. In FIG. 11 (b), it is assumed that the two Penrose tiles have a long side of about 20 μm, a short side of about 12 μm, and a Fresnel lens pitch of about 30 μm.

Therefore, the microlens array consisting of the second Penrose tiling has the following four basic characteristics required for the focus plate:
1) The viewfinder image is bright,
2) The blur is natural and easy to focus on (less adverse effects due to diffraction phenomenon (multi-line blur, uneven color)),
3) Less graininess and
4) It is possible to satisfy at the same time that moiré is unlikely to occur.

[2] Manufacturing Method of Focusing Screen A focusing screen made of the diffusion plate of the present invention can be obtained by forming a microlens array using a photolithography technique. Among these, the method called gray scale lithography is preferable. Grayscale lithography is a method of exposing a resist using a grayscale photomask that can change the degree of transmission / blocking of light (transmittance) and changing the depth at which the photoresist is developed depending on the location. This is a method for obtaining a three-dimensional resist shape. The details will be described below.

(1) Preparation of resist pattern
(a) Method using a grayscale photomask
(i) Production of photomask First, a grayscale photomask reflecting the arrangement of the microlens array and the shape of each lens is produced. The correlation between the exposure amount to the photoresist and the shape finally obtained after exposure / development is examined in advance, and the exposure amount verified in advance in consideration of the arrangement of the microlens array and the lens shape to be actually formed. A photomask having a pattern and density determined so as to obtain an exposure amount so that a desired shape is formed after exposure and development is used.

(ii) Photoresist exposure / development A photoresist is uniformly formed on a flat substrate made of silicon, glass, quartz or the like by using a spin coater so as to have a desired film thickness. Thereafter, pre-baking is performed to remove the solvent of the resist. A photomask created in advance that reflects the arrangement and shape of the microlens array is placed on a substrate coated with a resist, and then exposed using a light exposure machine under conditions that achieve the desired exposure. I do. After exposure, the resist is developed using a developer, and unnecessary resist is rinsed and removed to obtain a resist pattern having a desired three-dimensional shape.

(b) Other methods As a method for obtaining a resist pattern, the photoresist is exposed and developed in a desired arrangement pattern using a general photomask formed from a transmission part / blocking part, not a gray scale photomask. A method for obtaining a lens shape using the fluidity of a photoresist softened by heating after performing a heat treatment is well known. In recent years, “direct exposure equipment” or “maskless exposure” can be used to form a three-dimensional resist pattern by performing resist exposure by modulating the exposure amount depending on the location using electronic data, even without a photomask. There is also a device called “device”. A desired resist pattern may be formed by using these methods and apparatuses.

(2) Fabrication of focusing screen The formed resist pattern has the same shape as the desired light diffusing plate, but it is not used as it is as a diffusing plate (mat surface). Used as a master for the matte surface. For example, after producing a member made of metallic Ni having a reversed pattern of a three-dimensional shape by performing electroforming using the obtained resist pattern having a three-dimensional shape as a master, this member is processed into a desired dimension, etc. Thus, a core (transfer mold) for injection molding is produced. After assembling the core into a focusing screen mold, injection molding is performed using an injection molding device, and the three-dimensional shape of the core surface is transferred to the surface of the resin that has been injected and cured into the mold. A matte surface having a lens array pattern is produced on a focusing screen. Note that a core having a shape obtained by inverting the shape of the Fresnel lens is assembled on the opposite surface of the mat surface, and a Fresnel lens is formed on the opposite surface of the focusing screen.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Examples 1 and 2 and Comparative Examples 1 to 3
(1) Production of Focusing Screen A gray scale photomask reflecting the shape and arrangement of each lens was produced so that a microlens array as shown in Table 1 was obtained. A desired shape was formed after exposure / development by examining the correlation between the exposure amount to the photoresist and the shape obtained after exposure / development in advance.

  A photoresist (Tokyo Ohka Kogyo Co., Ltd .: PMER_P-HA1300PM) was uniformly formed on a silicon wafer substrate with a film thickness of 15 μm using a spin coater, and the resist solvent was removed by pre-baking (110 ° C., 6 minutes). The prepared photomask was placed on a substrate coated with a resist, and after exposure with a desired exposure amount, the resist was developed. An unnecessary resist was rinsed and removed to obtain a resist pattern having a three-dimensional shape of a microlens array.

  Using the resulting resist pattern as a master, electroforming is performed to produce a metallic Ni member with a three-dimensional reversal pattern, which is then processed into the desired dimensions to produce a core for injection molding (transfer mold) did. By assembling this core (core for microlens array) on one surface of a focusing screen-shaped mold, a core for Fresnel lens is assembled on the opposite surface, and then performing injection molding using an injection molding device, A focusing screen (18 mm × 26 mm × 1.35 mm) having a Fresnel lens (annular pitch: 30 μm) on the opposite surface of the microlens array pattern as a light diffusion surface (mat surface) was produced. An acrylic resin (Mitsubishi Rayon methacrylic resin molding material acrypet) was used as the resin for injection molding.

  In the microlenses in the focusing screens of the example and the comparative example, their periods cannot be uniquely defined. However, in order to make the conditions for generating moire and light diffraction uniform, the lens size and the arrangement interval are approximately equal. The length of one side is specified so that it is the same level, and when the pitch of the ring zone of the Fresnel lens on the opposite side is constant (30 μm), the size and arrangement interval of the lens and the zone pitch Designed to have the same ratio. In addition, in order to align the light diffusion performance of each sample, the curvature and height of the microlens array were designed so that the diffusion angle was about ± 10 ° (the F value of the microlens corresponds to F2.8).

(2) Evaluation of focusing screen The obtained focusing screens of Examples 1 and 2 and Comparative Examples 1 to 3 were incorporated into a single-lens reflex digital camera, and the performance was evaluated and compared by actually observing the viewfinder.

(a) Evaluation of natural bokeh and ease of focusing A geometric chart in which bright areas (white) and dark areas (black) are arranged in stripes through the camera's viewfinder with a built-in focusing screen. Was observed as a test pattern, and the appearance of stripes in a state where the lens was not in focus (defocused) was confirmed. In addition, while confirming the degree of blur of the test pattern, we investigated the change in blur and the ease of focusing when adjusting the lens focus. The results are shown in Table 2.

  In a state where the photographing lens is out of focus (defocused), when the blurring of the striped test pattern is observed, in Comparative Example 1 in which the hexagonal lens is filled, the fringes are not uniformly blurred but are multiplexed. It became so-called “multi-line blur”. The blur was very unnatural and uncomfortable. In addition, because it is not a homogeneous blur, the change in the blur from the out-of-focus state to the in-focus state is also very unnatural, and it is difficult to determine the state that matches the out-of-focus state. was there. The multi-line blur is considered to be due to the remarkable diffraction of light due to the periodic arrangement of lenses.

  On the other hand, in Comparative Example 2 in which randomness was given to the arrangement, the remarkable “multi-line blur” seen in Comparative Example 1 was not observed, and the stripe blur was almost uniform and very natural blur was obtained. It was. In addition, because it is a homogeneous blur, the change in the blur from the out-of-focus state to the in-focus state is continuous and natural, making it easy to grasp the in-focus state and easy to determine the focus. there were. It is presumed that light diffraction is suppressed by the introduction of randomness.

  In Example 1, Example 2 and Comparative Example 3, although some “multi-line blur” characteristics can be seen when confirmed in detail, the separation width in which the stripes are separated into multi-lines and the angular width of the orientation to be separated Is very small and is more homogeneous and continuous in terms of macro, and there is no noticeable discomfort like the “multi-line blur” in Comparative Example 1, and an almost natural blur is obtained. . In terms of ease of focusing, as in Comparative Example 2, it was easy to grasp the in-focus state, and it was easy to determine the focus. Multiple effects of the diffraction angle and azimuth due to the arrangement of the lens arrangement are assumed.In particular, in Example 1 and Example 2, the effect of reducing the diffraction phenomenon by adding a non-periodic lens arrangement is added, and the discreteness of diffused light is reduced. It is considered that a uniform and isotropic natural light diffusivity is obtained.

(b) Evaluation of brightness, graininess, and moire Through the camera's viewfinder incorporating the produced focusing screen, the viewfinder image when observing a surface light source with two-dimensionally uniform brightness is observed. We confirmed and compared the appearance of graininess and moire. The results are shown in Table 2.

  As a result of confirming the brightness of the finder image, Comparative Example 1 filled with a hexagonal lens was the brightest result. It was confirmed that Example 1, Example 2 and Comparative Example 3 employing Penrose tiling obtained a bright image substantially equivalent to Comparative Example 1. Compared with Example 1, Example 2, Comparative Example 1, and Comparative Example 3, Comparative Example 2 in which randomness was given to the arrangement clearly resulted in a dark finder.

  For the granular feeling, Example 1, Example 2, Comparative Example 1 and Comparative Example 3 can confirm the two-dimensional distribution of brightness due to the lens arrangement pattern, but the regular lenses are orderly without duplication or gaps. Since it is flat-filled, the finder image has a uniform brightness as a whole, and no noticeable graininess or roughness can be confirmed. On the other hand, in Comparative Example 2, a bright place and a dark place in the viewfinder image are randomly changed due to the change in the lens interval due to the randomness of the lens arrangement and the change in the lens tilt angle at the lens boundary portion. Due to the formation, noticeable graininess and roughness were generated.

  As for the occurrence of moiré, in Comparative Example 1 and Comparative Example 3, remarkable moiré occurred as shown in FIGS. 4 (c) and 7 (b), respectively. On the other hand, in Comparative Example 2, since the periodicity of the microlens array pattern was reduced by introducing randomness, no significant moire was observed. In Example 1 and Example 2, the occurrence of moiré was suppressed very well as compared with the periodic microlens array of Comparative Example 1 by introducing a two-dimensional non-periodic array pattern.

  As described above, the focusing screen using the diffusing plate of the present invention has the characteristics of the focusing screen using the microlens array, and the blur is reduced without reducing the brightness of the finder image and the little graininess. It was natural and easy to focus (small adverse effects due to diffraction phenomenon (multi-line blur and color unevenness)), and moire was difficult to occur.

1 ... SLR camera
101 ... Camera body
102 ... Opening
103 ・ ・ ・ Tube
104 ... Lens
105 ... Image sensor
106 ・ ・ ・ Finder
107 ... Main mirror
108 ・ ・ ・ Focusing screen
109 ... eyepiece
110 ・ ・ ・ Pental prism
111 ... Photographer
112 ・ ・ ・ Matte surface
113 ・ ・ ・ Fine unevenness
114 ・ ・ ・ Fresnel lens

Claims (7)

In order to observe a real image through an eyepiece optical system, a diffusion plate that forms the real image,
A light scattering surface obtained by filling a plane with at least two types of fixed microlenses having different outer peripheral shapes in plan view, and an annular surface formed on the opposite side of the light diffusion surface;
A diffusion plate, wherein the planar filling of the microlenses is non-periodic filling.   2. The diffusion plate according to claim 1, wherein the figure defining the outer peripheral shape of the microlens is two types of Penrose tiles, and the form of the plane filling is Penrose tiling. The diffusion plate according to claim 2, wherein the two types of Penrose tiles are composed of a first rhombus and a second rhombus having the same length on one side,
The first rhombus has an acute angle of 72 ° and an obtuse angle of 108 °,
The second rhomboid has an acute angle of 36 ° and an obtuse angle of 144 °. The diffuser plate according to claim 2, wherein the two types of Penrose tiles are composed of a dart-shaped square and a kite-shaped square,
The dart-shaped square has four interior angles of 36 °, 72 °, 36 ° and 216 ° in order,
The kite-shaped square has four interior angles of 72 °, 72 °, 72 ° and 144 °,
The diffusion plate according to claim 1, wherein a length of two sides sandwiching an inner angle of 216 ° of the dirt-shaped square is equal to a length of two sides sandwiching an inner angle of 114 ° of the kite-shaped square.   5. The diffusion plate according to claim 1, wherein a length of one side of the microlens is 5 to 50 μm.   6. The diffuser plate according to claim 1, wherein a pitch of the annular zone formed on the annular zone surface is 10 to 100 [mu] m.   A single-lens reflex camera using the diffuser plate according to claim 1 as a focusing screen.