JPS6242243B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for optically producing a novel diffuser plate suitable for use as a finder screen in single-lens reflex cameras, 8mm cameras, movie cameras, and the like.

The optical recording method referred to herein includes recording using light other than visible light.

In recent years, darkness and graininess have been pointed out as drawbacks of acrylic matte diffusers commonly used as camera viewfinder screens, and various improvements have been attempted. One of them is a full-scale microprism focus plate that has a structure in which triangular and square pyramids are arranged regularly, unlike the matte surface with random irregularities mentioned above, which has a special bokeh quality that makes distance measurement easy. Also, when the F number is close to the maximum openness, there is no vignetting due to vignetting, and the image has brightness close to that of an aerial image. However, because it has a regular structure, moiré fringes occur between objects that have a synchronous pattern or between the synchronous structure of a Fresnel lens, making it difficult to see the viewfinder. It has the disadvantage of causing shadows.

In contrast, the present applicant has developed the above-mentioned full-scale microprism focusing plate that has a special bokeh quality that makes distance measurement easy and maintains a bright characteristic, and that the brightness of the viewfinder suddenly increases above a certain FNo. when the aperture is stopped down. We have discovered a method to manufacture a new type of full-surface microlens-like reticle that reduces the drawbacks that can occur when using a reticle.
(Japanese Patent Application No. 53-165092 (Japanese Unexamined Patent Publication No. 55-90931)) If this manufacturing method is used, a diameter of 10 to 30 μm, which was not possible before,
A diffuser plate having a surface shape in which convex and/or concave microlens-like curved surfaces are arranged regularly and densely was obtained, and it was confirmed that this diffuser plate had the following advantages. That is, by controlling the arrangement pitch between the microlenses and the power of the microlenses, a limited directivity screen can be obtained, and a bright finder can be obtained.

Due to its regular arrangement, even when using a small-diameter lens (lens with a large FNo.), there is no graininess (fine, black spots) found in conventional diffuser screens; in other words, a clear viewfinder with good visibility. is obtained.

Due to the diffraction development caused by the regular lens arrangement, a special blurred image is obtained, making it easy to focus.

That's what it means. When using such a novel full-surface microlens-shaped diffuser plate as a viewfinder screen for a camera, it is desirable that the diameter of each microlens be on the order of 10μ (10μ to 40μ). However, although this full-surface microlens-shaped diffuser plate also has the above-mentioned characteristics, it basically has a diffraction grating structure (periodic structure), so when used as a finder screen for a single-lens reflex camera, the following problems arose. In other words, if there are many 0th order diffracted lights, the FNo.
When the lens is stopped down or a long focal length lens is used, a bright spot appears in the center of the viewfinder screen due to the shadow of the lens's pupil (diaphragm) being seen directly, and the surrounding area becomes faintly colored. Moiré fringes can also occur when the subject has a periodic structure, or when the pitch of the same circular pattern (usually 30 to 50 μm) of the Fresnel lens on the opposite side of the focal plane and the periodic structure of the diffuser plate are similar. This caused problems such as the viewfinder becoming difficult to see.

In view of the above points, the object of the present invention is to utilize the characteristics of the novel diffuser plate proposed by the applicant as described above, and to create an improved diffuser plate having standard characteristics that reduces problems such as coloring. This invention provides an optical manufacturing method for obtaining a novel diffuser plate.

As a known example of creating a diffuser plate using an optical method, for example, when a diffuser plate is irradiated with coherent light, the so-called speckle pattern that occurs in the emitted light is photographed and recorded on a photographic transfer plate, and marked with a white mark. This is used as a uniform illumination device for objects in holography by keeping the height of the unevenness below a certain level (Japanese Patent Publication No. 17093/1983), and when photographing a diffuser plate, the light is adjusted to a spatial frequency within the photographing light path. However, another diffuser plate with rotationally asymmetrical diffusion characteristics is created and is suitable for use as a projector screen (Japanese Patent Publication No. 49-10265). The diffused light from the diffuser plate is used as object light, and a coherent A holographic diffuser plate is created by overlapping the reference beam and used as a microfilm viewer (USP No.
3708217) etc. are known.

The present invention provides a novel method for producing a diffuser plate having the above-mentioned superior properties compared to the diffuser plate produced by the above-mentioned known methods.

Embodiments of the present invention will be described below with reference to the drawings.
Before describing the embodiments of the present invention, the patent application
A method for manufacturing a novel full-surface microlens-shaped diffuser plate disclosed in No. 53-165092 will be explained with reference to FIG.

In Fig. 1, 1 is a laser beam, 2 and 3 are beam expander systems, and 4 is three lenses 5 ₁ -
Lens holder that holds 5 ₃ , 6 ₁ to 6 ₃ are 3
It is a real point light source generated by three convex lenses, and in some cases, it has a small aperture slightly larger than the size of the point light source in order to remove noise caused by dust etc. attached to the lens. A filter 7 may also be provided. Reference numeral 8 denotes a pattern recording member, and interference fringes of three light beams are generated on the surface of the pattern recording member at a portion 10 where spreads of light beams 9 ₁ to 9 ₃ from each point light source overlap. When the three point light sources 6 ₁ to 6 ₃ are located at the vertices of a substantially equilateral triangle, this interference pattern has two-dimensional periodicity. By recording and developing this interference pattern on a photoresist, or recording it on a dry plate and processing it by various bleaching methods known in the field of holography, a concavo-convex pattern corresponding to the interference pattern can be obtained.

FIG. 2 is a photomicrograph taken using a microscope of a concavo-convex pattern obtained by recording the interference fringes of the three beams on a dry plate and further processing by a bleaching method.

In addition to the method described above, it is also possible to optically create a full-surface microlens-like diffuser plate having different arrangements using various two-dimensional arrangements of point light sources.

The manufacturing method of the embodiment of the present invention includes a means for further optically imparting speckled diffusivity to the surface of the full-surface microlens-like diffuser plate obtained by the above-mentioned optical method. The diffuser plate that can be
Compared to the diffuser plate obtained by the first manufacturing method, the problem of colored spots and moiré is reduced.

In this embodiment, as a means for imparting diffusivity, a technique for creating a speckle diffuser plate, which has already been proposed by the present applicant, is applied. That is, the present applicant has already attempted to control and make the speckle shape uniform in the space where speckles are recorded by overlaying a mask having an appropriately shaped aperture on a diffuser plate to which light with good coherence is to be irradiated. Obtaining another diffuser plate with preferable light distribution characteristics
51755) and that the diffuser plate obtained by these methods can be effectively used as a matte surface of a focusing plate provided in the viewfinder optical system of a camera (Japanese Patent Application Laid-open No. 42726/1983).

A first embodiment of the present invention will be described with reference to FIG. 3, in which a speckle pattern is superimposed on a surface structure in which microlens-shaped curved surfaces are arranged periodically to create a diffusive plate.

In Figure 3, 1 is a laser beam, 2 and 3 are beam expander systems, and 4 is three lenses _5.
A lens holder that holds ~ ₅₃ , ₆₁ ~ ₆₃ are three focused light sources generated by three convex lenses, and in some cases, remove noise caused by dust etc. attached to the lens at that position. For this purpose, a filter 7 having a small aperture slightly larger than the size of the point light source may be provided. 11 is a diffusion surface for obtaining a speckle pattern, 8 is a pattern recording member, on which the light beams from each point light source spread, and 9 ₁ to 9 ₃ overlap each other at angles 20. , interference fringes are generated by combining these three light beams and the diffused light 12 from the diffused object.

FIG. 4 shows a concavo-convex pattern obtained by recording on a recording member 8 an image in which a speckle pattern by the diffused light 12 is superimposed on the interference fringes of the three beams 9 ₁ , 9 ₂ , 9 ₃ , and then processing it by a bleaching method. This photo was taken using a microscope.

The interference pattern has a two-dimensional periodicity in which the microlens-shaped curved surfaces are arranged as shown in FIG.
An irregular speckle pattern of concave and convex portions is superimposed on each microlens-shaped curved surface.

It is preferable that there be at least two or more speckle patterns for each microlens arranged in a two-dimensional periodic manner, and five or more speckle patterns for a camera finder screen.

When such an interference pattern was recorded on a silver salt dry plate and the light intensity distribution was converted into the unevenness distribution of the gelatin layer by a known bleaching process, the surface of the microlens was formed as shown in the microscopic photograph in Figure 4a. A full-surface microlens-like diffuser plate on which irregularly arranged unevenness in a Tsukuru pattern was superimposed was obtained. A partially enlarged bird's eye view is shown in Fig. 4b. Such a microlens uneven structure can be mass-produced using various known copying methods. As the recording member 8, photopolymer, thermoplastic, dichromated gelatin, chalcogen glass, etc. are used depending on the wavelength of the light source. Furthermore, depending on the processing method of these members, the minute periodic structure can be made into a relief (unevenness) structure or an internal refractive index distribution.

In the interference pattern generating device shown in FIG. 3, the lenses ₅₁ to ₅₃ may be concave lenses, and the light beam that generates the interference fringes is not limited to a diverging light beam, but may also be a convergent light beam, a parallel light beam, or other irregular light beams in the interference pattern. The aberration may be such that it does not form a period.

In particular, in the method shown in _{FIG .}
If you want to obtain a distortion-free pattern over a wide area, it is desirable to use interference between three plane waves and diffused light. Although there is a possibility that some aberration will be introduced, the method of the following embodiment can be used to easily obtain three plane waves and diffused light.

Another embodiment of the present invention will be described using FIG. 5.

In FIG. 5, reference numeral 13 is a lens that has been polished only in the center, with the periphery left in a rough state. Since the plane 7 determined by the point light sources ₆₁ to ₆₃ is aligned with the focal plane of the lens 13, a plane wave 15 is generated from the center of the lens 13, and a diffused wave 18 generated by three light beams is generated from the peripheral area. ₁ to ₁₈₃ are emitted and incident on the optical recording material 8. By adjusting the distance between the lenses 2 and 3, the light beams from the point light sources ₆₁ to ₆₃ can be made into plane waves and superimposed on the surface of the sensitive material as the irradiation area 16.

FIG. 6 shows a third embodiment, in which a roughened inner surface of a cylinder 18 is used as a diffusion surface for forming a speckle pattern. Therefore, part of the light beams from the point light sources 6 ₁ , 6 ₂ , 6 ₃ becomes scattered light 20 ₁ , 20 ₂ , 20 ₃ on the inner surface of the cylinder, forming a speckle pattern.

Up until now, we have only described a method for simultaneously recording interference fringes to form an array of periodic microlens-like curved surfaces and an irregular uneven speckle pattern. You can also go to That is, by the method shown in Fig. 1, interference fringes in the form of a microlens array are first recorded,
Thereafter, the speckle pattern may be recorded using another optical system. A part of the optical system for forming only the speckle pattern is shown in FIGS. 7, 8, 9, and 10.

FIG. 7 shows an embodiment in which circular diffusers 24 ₁ to 24 ₃ are placed at each node of an equilateral triangle. 23 is a diffuser holding jig.

FIG. 8 shows an embodiment in which circular diffusers 26 ₁ to 26 ₄ are placed at each point of a square. 25 is a diffuser holding jig. Figure 9 shows a rectangular diffuser 28.
₁ , 28 _{, and 2} are arranged with a finite gap between them. 27 is a diffuser holding jig.

FIG. 10 shows an example in which the diffuser 29 and the diffuser holder 30 are arranged with an interval between them.

As shown above, the shape of the diffuser may be any shape as long as it is formed by a plurality of closed curves.

In the above description, the number of light beams for forming the microlens array is three, but a plurality may be used. In addition to the speckle pattern described above, the optical speckled pattern for forming the irregular irregularities may be formed by various other optical methods.

As described above, if the method for optically producing a diffuser of the present invention is used, a surface structure in which periodic microlens-shaped curved surfaces are arranged and an irregular uneven structure is formed on the microlens curved surfaces can be obtained. It has unprecedented excellent diffusion properties, making it bright and bright when used as a camera viewfinder screen.
It is possible to create a diffuser plate that is almost an ideal screen with clear ranging accuracy and is extremely useful.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a method for producing a diffuser that has already been applied for by the applicant, FIG. 2 is a micrograph of the surface of a diffuser plate obtained by the method shown in FIG. Figure 3 is a diagram showing the manufacturing method of the first embodiment of the present invention, Figure 4a is a microscopic photograph of the surface of the diffuser plate obtained by the method of the first embodiment, and Figure 4b is an enlarged bird's-eye view thereof. , 5 and 6 are diagrams showing the method of creating the second and third embodiments, and Figures 7, 8, 9, and 10 are diagrams showing a part of the optical system for creating the speckle pattern. be. In the figure, 1... Laser light, 2, 3... Expander section, 5 ₁ , 5 ₂ , 5 ₃ ... Lens, 6 ₁ ,
6 ₂ , 6 ₃ ... Point light source, 11 ... Diffusion surface, 8 ...
Recording materials.

Claims (1)

[Claims] 1. In a method for optically creating a diffuser plate on a photosensitive material, a periodic interference pattern is formed on the photosensitive material by superimposing a plurality of mutually coherent light beams at angles to each other. What is claimed is: 1. A method for optically producing a diffuser plate, comprising the steps of: forming an optical spot pattern; and guiding a light flux forming an optical spot pattern onto the photosensitive material. 2. The optical diffusion plate according to claim 1, wherein the light beam forming the optical spot pattern is a diffused light beam from an annular diffusion surface illuminated by a coherent light beam. Creation method. 3. Diffusion according to claim 1, wherein the light beam forming the optical spot pattern is a diffused light beam from two or more mutually independent diffusion surfaces illuminated by coherent light beams. Optical preparation method for plates.