JP3346629B2 - Manufacturing method of reticle and reticle forming mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reticle incorporated in a camera or the like. The present invention also relates to a method of manufacturing a mold for molding the reticle.

[0002]

2. Description of the Related Art Generally, in an optical device such as a camera,
When an image formed by the imaging optical system is formed on a focusing screen for observation, the larger the light diffusion angle at the focusing screen, the easier it is to check the defocused state and the easier the focusing, but the light reaches the eyes. There is a disadvantage that the scene is reduced and the brightness of the visual field is lost. Conversely, if the diffusion angle of light at the focusing screen is reduced, the field of view becomes brighter, but focusing becomes difficult. That is, the ease of focusing and the brightness of the image are mutually contradictory conditions, but a reticle that simultaneously satisfies these conditions as much as possible is desired. The focusing plate made of frosted glass, which is best known in the past, has a characteristic that the diffused light intensity is strong at a diffusion angle of 0 °, and sharply decreases as the diffusion angle increases. It is difficult to focus because a faint blur is observed around it. In addition, in a portion where the surface has a steep slope, the light refracted by the slope of the uneven surface does not reach the eyes because the light is refracted so much that the eyes appear as granular black spots and the image quality of the entire screen deteriorates. There is also.

On the other hand, a reticle using a phase grating has also been proposed. This reticle uses a spatial filter having a phase difference of π, and makes the zero-order diffracted light extremely weak and the ± 1st-order diffraction efficiency up to 40%. However, this reticle has a drawback that it is only possible to focus on an object having a specific direction because the directionality of the diffraction grating is specified.

[0004] Along with the design of the reticle as described above, a method of manufacturing the reticle has been studied in parallel.
Japanese Patent Publication No. 90931 reports that three or more coherent light beams are caused to interfere with each other, and the interference pattern is recorded as an uneven shape on a recording material. However, this method has a problem that only a reticle having a uniform pattern over the entire surface can be manufactured. That is, a reticle having a uniform pattern over the entire surface does not have a degree of design freedom and cannot cope with various required characteristics. For example, it is ideal that the entire surface of the reticle is uniformly bright. However, the brightness of the reticle having a uniform pattern over the entire surface may vary depending on differences in the aperture, aperture, pupil diameter of the viewfinder of the camera, and the characteristics of the photographing lens used. When this is viewed from the viewfinder, it changes depending on the distance from the center, and generally becomes darker toward the periphery, and does not have favorable characteristics.

[0005]

As described above, the performance of a reticle is closely related to its diffusion characteristics, and in order to produce a reticle having the desired performance, it is necessary to provide a corresponding diffusion characteristic. There is. The correlation between the performance and diffusion characteristics of this reticle has been studied for many years, and some of them have been clarified, but not all of them have been clarified yet, making it difficult to carry out optimal design. I was

The present invention has been made in view of such circumstances, and has as its object to provide a reticle capable of satisfying various requirements. Another object of the present invention is to provide a method for manufacturing a molding die used for manufacturing the reticle.

[0007]

In order to achieve the above object, a reticle according to the present invention has a myriad of microlenses with a constant pitch formed on the surface of a transparent substrate.
The radius of curvature between the curved surfaces of the microlenses decreases from the center of the transparent substrate toward the periphery, and the height of the microlenses is higher at the periphery than at the center. In the reticle of the present invention, countless microlenses having a constant pitch are formed on the surface of the transparent substrate, and the radius of curvature between the curved surfaces of each of the microlenses increases from the center of the transparent substrate toward the periphery. It is configured to be larger and the height of the microlens is lower on the peripheral side than on the center.

FIGS. 1A, 1B and 1C show a transparent substrate 3.
2 shows a cross section in which a microlens 1 having a constant pitch is provided on the surface of the microlens 1, the radius of curvature between the curved surfaces of the microlens 1 increases in the order of (a) → (b) → (c), and the height of the microlens ( The height between the top of the curved surface of the microlens 1 itself and the top between the curved surfaces of the microlens 1)
Are lower in the order of (a) → (b) → (c). When these shapes are used as the focusing screen, as the radius of curvature between the curved surfaces of the microlenses 1 is smaller and the height of the microlenses 1 is higher, light is diffused at a wider angle, and the radius of curvature is larger and the height is lower. The more light diffuses into a narrower angle. In the present invention, such a micro lens having a wide diffusion angle and a micro lens having a narrow diffusion angle are disposed from the center of the transparent substrate 3 toward the periphery. As a result, the diffusion characteristic changes from the center to the periphery of the reticle, and the brightness becomes uniform over the entire surface of the reticle when viewed from the viewfinder. In this case, the magnitude of the radius of curvature of the microlens from the center to the periphery of the transparent substrate 3 can be appropriately changed according to the viewfinder, the photographing lens, and the like.

FIG. 2 shows the production of a molding die used in the production of the reticle described above. A photosensitive material 5 such as a photoresist applied to a flat plate 4 is arranged at an imaging plane position 11 of a coherent imaging system, and a filter 9 is arranged on a Fourier spectrum plane 8 of an object 7 having an infinite number of minute openings 6. Each image 10 generated corresponding to the type of the filter 9 is exposed to a different portion of the photosensitive material 5 and developed to convert the light and dark of the image into an uneven pattern of the photosensitive material.
Then, this is used as a mother of the reticle, and is electroformed and inverted to form a molding die.

FIG. 2 shows an equal-magnification coherent imaging system. The left side of the object 7 is illuminated with parallel light from a laser or parallel light composed of a combination of a mercury lamp and a collimating lens. Object 7 and filter 9
And a first lens 12 and a second lens 13 having the same focal length f are provided between the filter 9 and the photosensitive material 5. The first lens 12 is arranged at a position f away from the object 7, the second lens 13 is arranged at a position 2 f away from the first lens 12, and the position at a distance f from the second lens 13 is defined as an image plane. Position 11 is obtained.
Further, the position of f from the first lens 12 in the light ray direction becomes the Fourier spectrum plane 8. In such a configuration, the Fourier spectrum of the object 7 located on the object-side focal plane of the first lens 12 is changed by the first lens 12 to the Fourier spectrum plane 8.
The Fourier spectrum is recombined by the second lens 13, and the image 10 is formed on the image-side focal plane of the second lens 13.

In the above configuration, by irradiating coherent light to an object 7 having an infinite number of apertures 6, a Fourier spectrum diffused (diffracted) by the apertures of the object 7 is generated on the Fourier spectrum plane 8. The filter 9 cuts the high-order spectrum and passes the low-order spectrum, so that the image on the imaging plane 11 changes according to the type of the filter. Specifically, as the higher-order spectrum is cut, even if the object 7 has a clear pattern, an image having a gradual change in brightness is formed. Therefore, the order of cut by the filter 9 is changed, and the light and dark of the image formed at this time can be converted into a concavo-convex shape by exposing and developing a different portion of the photosensitive material 5 and developing. By inverting the concavo-convex pattern of the photosensitive material by electroforming to form a mold, a mold for mass-producing the reticle of the present invention can be obtained.

[0012]

FIG. 3 shows a reticle 20 according to a first embodiment of the present invention.
4 and 5 show cross sections of the microlenses formed on the focusing screen 20. FIG. 4mm radius from center of reticle 20
The micro lens in the first region 20a up to FIG.
As shown in the figure, the height is 1.8 μm and the radius of curvature between the microlenses is 8 μm. The second region outside the first region 20a has a radius of 4 mm to a radius of 12 mm, and the height of the microlens in the second region 20b is 1.9 as shown in FIG.
μm, and the radius of curvature between the microlenses is 5 μm. Further, the third region 20c outside the radius of 12 mm
In FIG. 6, the height of the microlenses is 2.0 μm and the radius of curvature between the microlenses is 3 μm, as shown in FIG.

FIG. 7 shows a case where the reticle 20 of this embodiment is observed through the viewfinder 21. Finder 21
When the opening is small, the central portion is dispersed at a narrow angle, while it is dispersed at a wide angle toward the outer peripheral portion, so that the diffused light is efficiently collected in the finder 21 and the entire surface becomes bright.

FIG. 8 shows a method of manufacturing a molding die used for molding the reticle of the present embodiment, and the same elements as those in FIG. 2 are assigned the same reference numerals. The object 23 is a coherent optical system and has a pattern shown in FIG.
FIG. 10 shows the amplitude transmittance of the pattern of the object along the line AA. In this case, the pattern pitch is 17 μm, and the magnification of the optical system in the illustrated example is 1.0 μm.
It is.

On the image plane 11 of this optical system, a positive photoresist 26 applied to a glass plate 25 with a thickness of about 3 μm is set. A filter 27 is provided on the Fourier spectrum plane 8 while a positive photoresist 26 is provided.
The mask 28 is set in close contact with the front side of. FIG.
Numeral 1 denotes a filter 27, which is designed to transmit the spectrum of the first order and below. FIG. 12 shows the mask 28, which has a punched pattern with a radius of 4 mm. The positive photoresist 26 is exposed in such a state.

Next, on the Fourier spectrum plane 8, a filter 2 that transmits a spectrum of third order or lower as shown in FIG.
As shown in FIG. 14, a mask 28 having a pattern with a ring-shaped region with a radius of 4 to 12 mm removed from the positive photoresist 26 is brought into close contact with the positive photoresist 26 and exposed. Thereafter, a filter 27 that transmits the fifth or lower order spectrum as shown in FIG. 15 is set on the Fourier spectrum plane 8, and before the positive photoresist 26, a pattern having an outer region with a radius of 12 mm shown in FIG. Exposure is performed by bringing the mask 28 into close contact. After these exposures, the photoresist 26 is developed and heated at about 120 ° C. Then, the photoresist pattern is used as a mother to perform electroforming reversal, and a molding die for a reticle of this embodiment is manufactured.

FIG. 17 shows a light-dark pattern of development when a filter that passes a spectrum other than the first order is set in the above-described method, and FIG. 18 shows an image of an image when a filter that passes a third-order or lower spectrum is set. FIG. 19 shows the light and dark patterns of the image when a filter which passes the fifth and lower order spectra is set. By exposing and developing such a light / dark pattern on the photo lens 26, the light / dark pattern is recorded as a concave / convex pattern of the photoresist 26 by the action of solubilization progressing in a portion where light is more strongly irradiated. FIG.
17 shows the concavo-convex pattern corresponding to FIG. 17, FIG. 21 shows the concavo-convex pattern corresponding to FIG. 18, and FIG. 22 shows the concavo-convex pattern corresponding to FIG. be able to.

[0018]

Second Embodiment FIGS. 23, 24 and 25 show a second embodiment of the present invention. In the present embodiment, the first region 20a shown in FIG.
23 has a height of 1.7 as shown in FIG.
In FIG. 24, the height of the microlenses in the second region 20b is 1.6 μm, the radius of curvature between the microlenses is 5 μm, and the radius of curvature between the microlenses is 3 μm. The microlens in the area 20c is shown in FIG.
As shown in FIG. 5, the height is 1.5 μm, and the radius of curvature between the microlenses is 8 μm.

In the reticle 20 of this embodiment having such a configuration, light is diffused at a wide angle at the center portion, and is diffused at a narrow angle at the outer peripheral portion. FIG. 27 shows the reticle 20 of this embodiment as viewed from the finder 21. Since the central portion diffuses at a wide angle, the amount of light incident on the finder 21 decreases, and the peripheral portion diffuses at a narrow angle. The amount of light incident on the finder 21 decreases. For this reason, the overall brightness of the reticle decreases, but the overall brightness becomes uniform from the center to the outer periphery, and the reticle does not become darker toward the outer periphery.

FIG. 26 shows a method of manufacturing a molding die used for molding the reticle of the present embodiment, and the same elements as those in FIG. 8 are assigned the same reference numerals. Also in this embodiment, the object 23 has the pattern shown in FIG. In this embodiment, a negative photoresist 31 having a thickness of about 3 μm is applied to the glass plate 30 and the glass plate 30 is set so as to be positioned on the light source side. In this state, a filter 27 that passes the first-order and lower-order spectra as shown in FIG. 11 is set on the Fourier spectrum plane 8, and before the glass plate 30 coated with the negative photoresist 31, FIG.
A mask 2 with a punching pattern outside the radius of 12 mm indicated by.
8 is exposed to light. Subsequently, a filter 27 that transmits the third or lower order spectrum shown in FIG. 13 is set on the Fourier spectrum plane 8 and a mask of a ring-shaped punching pattern having a radius of 4 mm to 12 mm shown in FIG. Then, the substrate is exposed to light while being in close contact.
Subsequently, a filter 27 that transmits the fifth or lower order spectrum shown in FIG. 15 is set on the Fourier spectrum plane 8 and a radius of 4 mm shown in FIG.
Exposure is performed by closely contacting a mask 28 of a blanking pattern. Next, the photoresist 31 is developed and heated. The photoresist pattern is used as a mother to perform electroforming reversal to form a molding die.

In this embodiment, the light and dark pattern of the image when the filter is changed is the same as that of the first embodiment. However, in this embodiment, since the negative type photoresist is exposed, the portion which is more strongly exposed to light is hardened. Figure 2
8, as shown in FIG. 29 and FIG. 30, it is formed as a concavo-convex pattern in which a bright portion of light becomes convex. As a result, a motherboard of a reticle having a light diffusion property that is larger in the central portion than in the outer peripheral portion can be created.

In any of the above embodiments, it is sufficient that the photosensitive material has a property of converting a light and dark pattern of light into a concavo-convex pattern, such as photopolymer, thermoplastic, dichromated gelatin, chalcogen glass and the like. It can be arbitrarily selected according to the wavelength of the light source. Also, the magnification of the optical system can be arbitrarily selected, such as enlargement, reduction, and equal magnification.

[0023]

Embodiment 3 In the reticle according to Embodiment 3 of the present invention, the microlenses in the first region 20a shown in FIG. 3 have a height of 1.5 μm and a radius of curvature between the lenses of 8 μm as shown in FIG. As shown in FIG. 24, the micro lenses in the second region 20b have a height of 1.6 μm and a radius of curvature between the lenses of 5 μm.
m, and the microlenses in the third region 20c are shown in FIG.
The height is 1.7 μm and the radius of curvature between the lenses is 3 μm as shown in FIG. When the reticle of this embodiment is viewed from the viewfinder 21, the central portion is diffused at a narrow angle and the outer peripheral portion is diffused at a wide angle. Therefore, as in FIG. 7, the diffusion efficiency is good and the entire surface is bright. There are visible benefits.

The mold for molding the reticle of this embodiment can be manufactured by reversing the insertion order of the filter 27 in the system using the negative photoresist of the second embodiment. That is, by inserting the filter 27 in the order of the filter of FIG. 15 → the filter of FIG. 13 → the filter of FIG. 11, the filter order is such that the lower order spectrum is cut from the higher order spectrum.
Hereinafter, a molding die can be manufactured in the same procedure as in Example 2.

[0025]

Fourth Embodiment In a reticle according to a fourth embodiment of the present invention, the microlenses in the first region 20a shown in FIG. 3 have a height of 2.0 μm and a radius of curvature between the lenses of 3 μm as shown in FIG. ,
As shown in FIG. 5, the microlenses in the second region 20b have a height of 1.9 μm, the radius of curvature between the lenses is 5 μm, and the microlenses in the third region 20c have a height as shown in FIG. Is 1.8 μm and the radius of curvature between lenses is 8 μm
It has become. When the reticle of this embodiment is viewed from the finder 21, as shown in FIG. 27, light is diffused at a wide angle at the center and light is diffused at a narrow angle at the outer periphery. The amount of light to be emitted is reduced.
For this reason, the overall brightness decreases, but the brightness of the entire surface becomes uniform from the center to the outer periphery.

The molding die for molding the reticle of this embodiment can be manufactured by reversing the insertion order of the filter 27 in the system using the positive photoresist of the first embodiment. That is, by inserting the filter 27 in the order of the filter of FIG. 15 → the filter of FIG. 13 → the filter of FIG. 11, the filter order is such that the lower order spectrum is cut from the higher order spectrum.
Hereinafter, a molding die can be manufactured in the same procedure as in Example 1.

[0027]

As described above, according to the reticle of the present invention,
In a myriad of microlenses provided at a constant pitch on the surface of the transparent substrate, the radius of curvature between the curved surfaces of the microlenses is smaller and the height of the microlenses is higher, the light is diffused at a wider angle, and the radius of curvature is larger. Further, as the height of the microlens is lower, the light is diffused at a narrower angle, so that the light diffusion characteristic can be changed from the center of the reticle to the periphery, and therefore, from the center to the outer periphery. Thus, a reticle having a uniform brightness can be obtained. Further, in the present invention, a molding die for molding the reticle can be easily formed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a microlens.

FIG. 2 is an optical path diagram for forming a molding die.

FIG. 3 is a plan view of a focusing screen.

FIG. 4 is a cross-sectional view of the microlens according to the first embodiment.

FIG. 5 is a cross-sectional view of the microlens according to the first embodiment.

FIG. 6 is a cross-sectional view of the micro lens according to the first embodiment.

FIG. 7 is a side view showing the operation of the reticle.

FIG. 8 is an optical path diagram for manufacturing the molding die of Example 1.

FIG. 9 is a plan view of the object according to the first embodiment.

FIG. 10 is a diagram showing an amplitude transmittance characteristic of the object according to the first embodiment.

FIG. 11 is a front view of a filter.

FIG. 12 is a front view of a mask.

FIG. 13 is a front view of another filter.

FIG. 14 is a front view of another mask.

FIG. 15 is a front view of still another filter.

FIG. 16 is a front view of still another mask.

FIG. 17 is an explanatory diagram showing a light-dark pattern of an image.

FIG. 18 is an explanatory diagram showing a light-dark pattern of an image.

FIG. 19 is an explanatory diagram showing a light-dark pattern of an image.

FIG. 20 is a sectional view showing an uneven pattern of the photosensitive material.

FIG. 21 is a sectional view showing an uneven pattern of a photosensitive material.

FIG. 22 is a sectional view showing an uneven pattern of a photosensitive material.

FIG. 23 is a cross-sectional view of a microlens.

FIG. 24 is a cross-sectional view of a microlens.

FIG. 25 is a cross-sectional view of a microlens.

FIG. 26 is an optical path diagram showing the manufacture of the second embodiment.

FIG. 27 is a side view showing the operation of the reticle.

FIG. 28 is a cross-sectional view of another microlens.

FIG. 29 is a cross-sectional view of another microlens.

FIG. 30 is a sectional view of another microlens.

[Explanation of symbols]

 1 Micro lens 3 Transparent substrate

──────────────────────────────────────────────────続 き Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03B 13/24 G02B 3/00

Claims (3)

(57) [Claims] An infinite number of microlenses having a constant pitch are formed on the surface of a transparent substrate, and the radius of curvature between the curved surfaces of the microlenses decreases from the center to the periphery of the transparent substrate. Wherein the height of the microlens is higher on the peripheral side than on the center. 2. An infinite number of microlenses having a constant pitch are formed on the surface of a transparent substrate, and the radius of curvature between the curved surfaces of the microlenses increases from the center to the periphery of the transparent substrate. Wherein the height of the microlens is lower on the peripheral side than on the center. 3. A photosensitive material applied to a flat plate is arranged at an image plane position of a coherent imaging system, and a filter is arranged on a Fourier spectrum surface of an object having an infinite number of minute apertures, corresponding to the type of the filter. After each image generated by exposing to a different portion of the photosensitive material, developing the photosensitive material to convert the brightness of the image into irregularities of the photosensitive material,
A method for manufacturing a reticle forming die, comprising: performing electroforming reversal using this as a mother.