JP2941968B2 - Optical element making method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an optical element, and more particularly, to a refractive index distribution having a refractive index distribution in which the refractive index gradually changes in a radial direction around a point on a plane of a lens surface. The present invention relates to a mold lens (GRIN lens) and a method for producing a lens array. For example, the lens array is applied to an imaging element such as a facsimile, a document reading unit of an image scanner, and an optical printer head.

[0002]

2. Description of the Related Art Cylindrical gradient index lenses are known. In this lens, the refractive index changes approximately in the square approximation from the center axis of the transparent cylinder made of synthetic resin or glass toward the radial direction. Therefore, a light beam that is perpendicularly incident on one surface of the transparent cylinder is converged or diverged in the transparent cylinder, and is emitted to the outside from the other surface. If it decreases in the direction, it is focused in a spot at the focal point.

[0003] In addition to a columnar gradient index lens, a gradient index lens using a transparent flat plate is also known. In such a flat-plate refractive index distribution type lens, for example, the refractive index changes by a square approximation from the center in the thickness direction of the flat transparent substrate made of synthetic resin or glass toward both surfaces. I have. Accordingly, light rays incident parallel to the two side surfaces from one side edge existing between the two side surfaces of the transparent substrate are focused or diverged in the thickness direction of the substrate in the transparent substrate, and similarly, It is emitted to the outside from the other side edge existing between the two side surfaces.For example, when the refractive index decreases from the center plane in the thickness direction to the two side surfaces in a nearly square approximation, a bright line shape Focused on.

[0004] However, in the case of a conventionally-known refractive index distribution type lens, the refractive index distribution is two-dimensional. For example, in the case of the above-mentioned cylindrical refractive index distribution type lens, the refractive index gradually changes in the imaginary plane perpendicular to the central axis in the radial direction from the central axis. Has not changed in the direction along. Further, in the case of the above-described flat-plate shaped gradient index lens,
In the virtual plane orthogonal to the surface, the refractive index gradually changes from the center plane in the thickness direction to both surfaces,
There is no change in the traveling direction of the light beam, that is, in the virtual plane parallel to the surface. In the case of these lenses,
Since the manufacturing process is complicated, there is a problem that it is not suitable for mass production.

[0005] To solve this problem, for example, Japanese Patent Application Laid-Open No. 2-50102 has been proposed. This publication relates to a method for producing a gradient index lens having a refractive index distribution in which the gradient index gradually changes in the radial direction with one point on the plane of the lens surface as a center. That is, a first monomer is semi-polymerized by a method of manufacturing a lens body in which a substance that changes the refractive index is diffused into a transparent substrate to form a gradient index lens portion in a common transparent substrate. After the second monomer copolymerized with the first monomer is selectively diffused into the transparent substrate, the polymerization of the entire transparent substrate is completed. A plurality of lens portions are formed.

FIGS. 8 and 9 show a conventional lens body, in which 21 is a transparent substrate, 21a is a front surface, 21b is a back surface, 22 is a mask, 22a is a circular window (hole), and 23 is a refraction. Rate distribution type lens part, 24 is a light ray, 25 is a focal position, 2
6 is a unit lens. On the transparent substrate 21, a mask 22 having a circular window or hole 22a at the center thereof is formed. The material of the mask 22 can be appropriately determined according to the diffusion material containing the diffusion source diffused through the holes 22a. That is, first, a mask coating layer is formed on the entire surface of the substrate 21, and then the mask coating layer is coated with a photoresist film. Next, a portion of the photoresist film corresponding to the hole 22a is exposed to light, and the photoresist film in the exposed portion is removed. Next, the mask coating layer in the removed portion is further removed, and then the remaining photoresist film is removed. Thus, a transparent substrate 21 having a mask 22 is obtained.

Next, a predetermined refractive index distribution is formed in the substrate 21 by diffusing the diffusion source 14 into the substrate 21 through the hole 22a. As a method for diffusing the diffusion source 14 in the substrate 21 to obtain a predetermined refractive index distribution, a transparent substrate 21 made of a synthetic resin made of a transparent polymer may be used.
A method is used in which a monomer that changes the refractive index by copolymerization with this polymer is diffused and moved, and then the above-described copolymerization is performed.

FIGS. 10A and 10B show an example of a refractive index distribution in a lens body. FIG.
9A shows the refractive index distribution in the axial direction (z-axis direction) of the gradient index lens portion 23 of the lens body shown in FIG. 9, and the refractive index is, for example, squared from the front surface 21a of the substrate 21 to the back surface 21b. It gradually decreases by approximation and changes in an arc as a whole. FIG. 10B shows a refractive index distribution (ie, z) in a direction orthogonal to the axial direction.
Refractive index distribution at an arbitrary point z ₀ in the axial direction in the x-axis direction and the y-axis direction), and as the distance from the center line increases, the refractive index gradually decreases, for example, by a square approximation, to form a mountain-shaped distribution as a whole. I have.

That is, in the conventional example shown in FIGS. 8 to 10, since the array lens is formed in the transparent plastic member, crosstalk between adjacent lenses is large as shown in FIG. (A large amount of light other than the effective imaging light is transmitted to the image plane.) The imaging performance is significantly reduced. In addition, the position of the lens and the length of the gradient index lens (GRIN lens) are not sufficiently set, so that the image cannot be synthesized in space. FIG. 11 shows an example in which a configuration in which an erect real image is formed is provided to explain the state of occurrence of crosstalk. When made of a polymer material, there is a drawback that shrinkage due to polymerization is large and dimensional stability is lacking.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has an image forming structure in which a base plate forming a gradient index lens is formed of a light absorbing member to reduce crosstalk between adjacent lenses. Improving performance and GRI
An optical system in which the arrangement position and length of the N lenses are appropriately determined so as to satisfy a relationship for obtaining an erect real image, and a lens array covering an arbitrary area can be easily obtained by adopting a configuration capable of combining images between lenses. The purpose of the present invention is to provide an element manufacturing method.

[0011]

To achieve the above object, the present invention provides (1)
A monomer Ma solution forming a polymer Pa having _a refractive index n _{a in} which a plurality of hollow cylindrical containers each having a closed end are densely arranged in a plate-like shape, in which a polymerization initiator is dissolved, is provided. injected, is polymerized by heat or light, etc., polymers having a different refractive index n _b of whether the polymerization is stopped at gel state, or a cylindrical vessel completed the step of polymerization is 100% complete the refractive index n _a Immersed in a monomer Mb solution forming Pb, or held under a vapor atmosphere of the monomer Mb,
Diffusing the monomer Mb from the surface of the polymer Pa toward the other end,
Copolymerization to form a refractive index distribution in which the refractive index changes continuously spherically from the opening end, or (2) a plurality of hollow cylindrical containers having one end closed are densely formed into a plate shape. A monomer Ma solution forming a polymer Pa having _a refractive index n _{a in} which a polymerization initiator is dissolved is poured into a container provided and a portion other than the hollow portion filled with a light absorbing member, and heat or light is applied thereto. It is polymerized by, or to stop the polymerization in the gel state, or monomers to form a polymer Pb having different refractive index n _b and the cylindrical container was terminated the step of polymerizing is completed 100% the refractive index n _a The polymer M is immersed in a solution of Mb, or kept under a vapor atmosphere of monomer Mb, and the monomer Mb is diffused and copolymerized from the surface of the polymer Pa toward the other end to have a refractive index from the opening end. Forming a continuously changing refractive index distribution in a spherical shape, or , The containers are arranged in a plate shape densely plurality is cylindrical container of hollow which is closed (3) at one end,
A monomer Ma solution for forming a polymer Pa having _a refractive index na in which a polymerization initiator is dissolved is injected, and a hollow cylindrical container having one end closed has a refractive index n _{a in} which the polymerization initiator is dissolved. A monomer Ma solution for forming the polymer Pa is injected, polymerized by heat or light or the like, and the polymerization is stopped in a gel state or the step of completing the polymerization 100% is completed, and the closing member of the cylindrical container is closed. After removing, by soaking the cylindrical vessel the monomer Mb solution to form a polymer Pb having different refractive index n _b and the refractive index n _a, or held under monomer Mb vapor atmosphere And diffusing and copolymerizing the monomer Mb from the surface of the polymer Pa to the other end to form a refractive index distribution in which the refractive index continuously changes spherically from the opening end, or (4) ) Multiple hollow cylindrical containers with one end closed Are arranged in a plate shape, the vessel portion other than the hollow is filled with a light absorbing member, a monomer Ma solution to form a polymer Pa injected having a refractive index n _a dissolved a polymerization initiator, A polymer P having _a refractive index n _a obtained by dissolving a polymerization initiator in a hollow cylindrical container having one end closed.
After injecting a monomer Ma solution for forming a and polymerizing it by heat or light or the like, terminating the polymerization in a gel state or terminating the step of completing the polymerization 100%, and removing the cylindrical container closing member, was immersed in the monomer Mb solution to form a polymer Pb having different refractive index n _b and a cylindrical container wherein the refractive index n _a, or monomer Mb maintained under steam atmosphere, said heavy Monomer M toward the other end from the surface of the united Pa
b is diffused and copolymerized to form a refractive index distribution in which the refractive index continuously changes spherically from the opening end. Hereinafter, a description will be given based on examples of the present invention.

FIG. 1 is a block diagram for explaining an embodiment of a method for producing an optical element according to the present invention. In FIG. 1, reference numeral 1 denotes a frame, and 2 denotes a hollow portion. A cylindrical container filled with a light absorbing member except for the hollow portion, that is, a monomer Ma which forms Pa having _a refractive index n _a in the hollow portion 2 of the frame 1.
A (g) and a polymerization initiator b (g). The polymerization proceeds by heating. The polymerization is stopped in a gel state by setting the conditions of the polymerization temperature T and the time t, or the polymerization is completed 100%. Next, Mb heated to e (° C.)
The block prepared as described above is placed in the monomer f (g), held for h hours, and the Mb monomer is diffused and polymerized in the Ma polymer. Thereafter, the block after diffusion is separated from the Mb monomer, and finally heated at i (° C.) for j hours to complete the polymerization. In this way, the refractive index distribution gradually changes in the radial direction about one point on the plane of the lens surface.

FIG. 1 shows an example in which the outer shape is rectangular. If one side is sealed with the plate 8 when filling the frame 1 with the monomer liquid, the liquid can be prevented from leaking. Here, the frame 1 can be made of plastic, glass, metal, or the like in which a light absorber such as carbon is dispersed. As Ma, for example, a methacrylic acid-based monomer containing fluorine such as 2.2.2 trifluoroethyl methacrylate, 1.1.5 trihydroperfluoropentyl methacrylate, or a monomer represented by the following formula: You can choose.

[0014]

[Table 1]

As the monomer Mb, for example, in the case of methacrylates, it is selected from benzyl acrylate, vinyl phenyl acrylate, ethylene dimethacrylate, benzyl methacrylate, β methallyl methacrylate, and a monomer having two or more of the following groups (the same group may be used). You can also.

[0016]

[Table 2]

If the refractive index of the polymer polymer Pa of the monomer Ma is n _a and the refractive index of the polymer polymer Pb of the monomer Mb is n _b , then n _a <n _b . Further, any polymerization initiator such as hydroquinone and benzyl peroxide can be used. FIG. 2 is a view showing a process of forming a refractive index distribution. In the drawing, reference numeral 3 denotes a filler, 4 denotes a portion where the refractive index distribution is formed, 5 denotes a polymer, and 6 denotes a frame. Portions are given the same reference numerals. Fig. (A) shows a state of only the frame, and Fig. (B) shows a state in which a hollow portion of the frame is filled with a Ma monomer, polymerization is started by heating and keeping the temperature, and gelation is performed. Is polymerized after diffusing the Mb monomer, and the refractive index distribution becomes 1 on the plane of the lens surface.
This shows a state in which a refractive index distribution that gradually changes in the radial direction with respect to a point is formed. The diffusion may be performed simultaneously from both sides as shown on the right side of FIG. The refractive index distribution (GRI
N) It is possible to control the light quantity distribution of the single lens.

FIG. 3 is a view showing another embodiment of the method for producing an optical element according to the present invention. In the figure, reference numeral 6 denotes a frame having a cylindrical outer shape, and the frame 6 can select an optimum shape depending on the application. .

FIG. 3 is a view showing still another embodiment of the method for producing an optical element according to the present invention. In the figure, reference numeral 7 denotes a rectangular parallelepiped frame. A plurality of hollow cylinders are densely arranged in a plate shape, and the other than the hollow portion is filled with a light absorbing member.
_a (g) is poured into a monomer Ma which forms Pa having _a, and a polymerization initiator b (g) is poured. The polymerization proceeds by heating. The polymerization is stopped in a gel state by setting the conditions of the polymerization temperature T and the time t, or the polymerization is completed 100%. Next, the Mb monomer f heated to e (° C.)
The block prepared above is placed in (g), held for h hours, and the Mb monomer is diffused and polymerized in the Ma polymer. Thereafter, the block after diffusion is separated from the Mb monomer, and finally heated at i (° C.) for j hours to complete the polymerization, and the refractive index distribution is directed radially around one point on the plane of the lens surface. It forms a gradually changing refractive index distribution.

FIG. 5 is a view showing still another embodiment of the method for producing an optical element according to the present invention. The lenses are arranged in a staggered arrangement in order to further reduce the non-uniformity (light amount unevenness) of the combined light amount distribution between the two-dimensionally arranged lenses. By doing so, it is possible to reduce the light amount unevenness that occurs according to the arrangement cycle of the lenses.

FIGS. 6A and 6B are diagrams showing still another embodiment of the method for producing an optical element according to the present invention. An example in which one or two rows of lens arrays are formed, which is used as a facsimile, a document reading unit of an image scanner, or an image forming element such as an optical printer head.

FIG. 7 is a view showing the state of image synthesis when formed on an array lens. In the figure, 11 to 14 and 11 'to 1
4 'is an image. The specifications are determined so that each lens covers an area larger than the diameter of each lens, and an image formed by each lens can be synthesized. Further, since the light shielding layer is formed at the boundary between the lenses, no crosstalk occurs between adjacent lenses.

[0023]

As apparent from the above description, the present invention has the following effects. (1) Effects corresponding to claims 1 and 3; since the base plate forming the refractive index-divided lens is formed of a member different from the lens, the dimensional stability is high, and the frame is required to have the necessary shape from the beginning. It can be expected that effects such as easy assembling can be obtained. (2) Effects corresponding to the second and fourth aspects: since the base plate forming the refractive index dividing lens is formed of a light absorbing member, crosstalk between adjacent lenses can be reduced, and the imaging performance can be improved. Improve. Further, the arrangement and length of the GRIN lens are appropriately determined so as to satisfy the relationship of obtaining an erect real image, and a lens array covering an arbitrary area can be easily obtained by adopting a configuration capable of combining images between lenses. it can.

[Brief description of the drawings]

FIG. 1 is a view for explaining an embodiment of a method for producing an optical element according to the present invention.

FIG. 2 is a diagram illustrating a process of forming a refractive index distribution.

FIG. 3 is a view showing another embodiment of the method for producing an optical element according to the present invention.

FIG. 4 is a view showing still another embodiment of the optical element producing method according to the present invention.

FIG. 5 is a view showing still another embodiment of the optical element producing method according to the present invention.

FIG. 6 is a view showing still another embodiment of the optical element producing method according to the present invention.

FIG. 7 is a diagram illustrating an image combining state when formed on an array lens.

FIG. 8 is a view showing a conventional lens body (single body).

FIG. 9 is a view showing a conventional lens body (a plurality of bodies).

FIG. 10 is a diagram showing an example of a refractive index light distribution in a lens body.

FIG. 11 is a diagram showing floss talk between adjacent lenses.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Frame (rectangular body) 2 Hollow part 3 Filler 4 Forming part of refractive index distribution 5 Polymer 6 Frame (cylindrical body) 7 Frame (cuboid) 8 Plate

Claims (4)

(57) [Claims] 1. A method for forming a polymer Pa having _a refractive index n _{a in} which a polymerization initiator is dissolved in a container in which a plurality of hollow cylindrical containers each having a closed end are densely arranged in a plate shape. Polymer solution is injected and polymerized by heat or light, and the polymerization is stopped in a gel state, or the polymerization is performed by 100%
It was immersed the finished cylindrical vessel the step of completing the monomer Mb solution to form a polymer Pb having different refractive index n _b and the refractive index n _a, or the under monomer Mb vapor atmosphere Holding and diffusing and copolymerizing the monomer Mb from the surface of the polymer Pa toward the other end to form a refractive index distribution in which the refractive index continuously changes spherically from the opening end to the spherical surface. How to make an optical element. 2. A refractive index obtained by dissolving a polymerization initiator in a container in which a plurality of hollow cylindrical containers each having a closed end are densely arranged in a plate shape and a portion other than the hollow portion is filled with a light absorbing member. Inject a monomer Ma solution to form a polymer Pa having _a na and polymerize by heat or light, etc., and terminate the polymerization in a gel state. The polymer Pb having a refractive index n _b different from the refractive index n _a is immersed in a monomer Mb solution for forming a polymer Pb, or is kept under a monomer Mb vapor atmosphere, and is separated from the surface of the polymer Pa by another. A method for producing an optical element, comprising diffusing and copolymerizing a monomer Mb toward an end to form a refractive index distribution in which a refractive index continuously changes spherically from an opening end. 3. A method for forming a polymer Pa having _a refractive index n _{a in} which a polymerization initiator is dissolved, in a container in which a plurality of hollow cylindrical containers each having a closed end are densely arranged in a plate shape. Polymer solution having a refractive index n _{a in} which a polymerization initiator is dissolved in a hollow cylindrical container having one end closed.
A monomer Ma solution for forming a is injected, polymerized by heat or light, and the polymerization is stopped in a gel state or the step of completing the polymerization 100% is completed, and the closing member of the cylindrical container is removed. After the, then immersed the cylindrical vessel the monomer Mb solution to form a polymer Pb having different refractive index n _b and the refractive index n _a, or maintained under monomer Mb vapor atmosphere, Forming an optical element by diffusing and copolymerizing the monomer Mb from the surface of the polymer Pa toward the other end to form a refractive index distribution in which the refractive index continuously changes spherically from the opening end; Method. 4. A refraction in which a polymerization initiator is dissolved in a container in which a plurality of hollow cylindrical containers each having a closed end are densely arranged in a plate shape, and a portion other than the hollow portion is filled with a light absorbing member. single the rate n _a polymer Pa injecting a monomer Ma forming solutions having, in a hollow cylindrical container with one end closed to form a polymer Pa having a refractive index n _a dissolved a polymerization initiator material Polymer solution is injected and polymerized by heat or light, and the polymerization is stopped in a gel state.
Exit 00% STEP to complete, the after removing the closure member of the cylindrical container, the monomer M to form a polymer Pb having different refractive index n _b and a cylindrical container wherein the refractive index n _a
b. Dipped in the solution, or kept in a vapor atmosphere of monomer Mb, and diffused and copolymerized monomer Mb from the surface of the polymer Pa toward the other end, so that the refractive index was spherical from the open end. A method of forming an optical element, wherein a refractive index distribution that changes continuously is formed.