JPH04240601A - Optical element creation method - Google Patents

Abstract

PURPOSE:To from the base plate on which a refractive index distributed type lense is to be formed with a liht-absorbing material and to reduce crosstalk between adjacent lenses. CONSTITUTION:This optical element is produced by mixing a monomer Ma for forming a reticular polymer Pa having a refractive index of na, a polymerization initiator, a monomer Mb for forming a polymer having a refractive index of nb into a hollow space 2 of a frame 1 filled with the light absorbing material, forming the inside wall of the space made of a material similar to the polymer Pb, and heating the mixture poured into the frame 1 to polymerize it into the polymer different in refractive index in the radial direction, and thus the refractive index distribution to be formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical element, and more particularly to a method for manufacturing a gradient index lens in which a refractive index distribution exists in the radial direction, and a lens array. For example, the lens array is applied to an image forming element of a facsimile machine, a document reading section of an image scanner, an optical printer head, and the like.

0002

BACKGROUND OF THE INVENTION Known documents describing the prior art related to the present invention include, for example, Y. Koike Y. Takeza
wa and Y. Ohtsuka, “New Inte
rfacial-gel copolymerizat
ion technique for steric
GRIN polymer optical wave
guides and lens arrays” (A
ppl. Opt. 27, 3, P. 486~P. 491
, 1988). This is Inerfacial-gel copoly
The present invention relates to a lens array manufacturing method using a merization technique, that is, an interfacial gel heterogeneous copolymerization method.

[0003] PMMA (polymethyl met
Holes are formed in a transparent plastic plate of MMA (Methyl Methyl
thacrylate) and VPAc (Vinyl ph
enylacetate) to 4/1 (wt./wt.)
Hydroquinone, which is a polymerization initiator, is added to the liquid monomers mixed at a ratio of 1,000,000,000,000 and the mixture is injected into the hollow part and heated. next,
The surface of PMMA is swollen by the liquid monomer to form a gel layer. Next, copolymerization begins within the gel (gel effect)
The reaction proceeds to the center. The refractive index distribution is formed as follows. The refractive index n and reactivity r of the mixed monomers are nm<nv, rm>1 and rv<1 for MMA (nm, rm) and VPAc (nv, rv), and for PMMA
The part near the tube wall (outer circumferential part) has a high MMA composition ratio with high reactivity and low refractive index, and VPA increases toward the center of the cylinder.
The ratio of c becomes higher. Therefore, a refractive index distribution is formed in the radial direction such that the refractive index gradually decreases from the center of the cylinder toward the periphery.

FIGS. 9(a) to 9(d) are procedural diagrams of a radial GRIN waveguide in the interfacial gel heterogeneous copolymerization method, and FIG. 10 is a diagram showing a 2-D radial GRIN lens array. Since the array lens is formed based on a transparent plastic member, crosstalk between adjacent lenses is large (a large amount of light other than the effective imaging light is transmitted to the image plane), as shown in Figure 11. Performance is significantly degraded. Also, the location of the lens and the GR
The length of the IN lens is insufficiently set, and the configuration does not allow image synthesis in space.

[0005]

[Purpose] The present invention has been made in view of the above-mentioned circumstances, and has a structure in which the base plate (frame) forming a gradient index lens is formed of a light absorbing material to reduce crosstalk between adjacent lenses. and to improve imaging performance.
In addition, by coating the inner wall of the hollow part that forms the lens of the base plate (frame) that forms the gradient index lens with the same transparent material as the constituent material of the monomer that forms the lens, as a barrier layer, To reduce transmission loss by preventing the light absorbing member of the frame from diffusing into the diffusion part with the inner wall of the base that occurs when forming a gradient index lens by polymerization, and to reduce transmission loss by adjusting the placement position and length of the GRIN lens. It is an object of the present invention to provide a method for producing an optical element that easily obtains a lens array that covers an arbitrary area by satisfying the relationship that is appropriately determined to obtain an erect, same-magnification image and having a configuration that allows image synthesis between lenses. It was done for a purpose.

[0006]

[Structure] In order to achieve the above objects, the present invention provides (1)
Reticular polymer (including copolymer) Pa with refractive index na
, a polymerization initiator, and the refractive index n
A is mixed with a monomer Mb forming a polymer Pb having a refractive index nb different from that of a, the part other than the hollow part is filled with a light absorbing member, and the inner wall surface of the hollow part is made of a material almost the same as that of the Pb. (2) Injecting the mixture into a hollow cylindrical container coated with Na and polymerizing the mixture with heat or light to form a refractive index distribution in the radial direction; Mixing a monomer Ma forming a combined (including a copolymer) Pa, a polymerization initiator, and a monomer Mb forming a polymer Pb having a refractive index nb different from the refractive index na, The above is placed in a container in which a plurality of hollow cylinders are densely arranged in a plate shape, the part other than the hollow part being filled with a light absorbing member, and the inner wall surface of the hollow part being covered with a material substantially the same as the Pb. Injecting a mixture and polymerizing the mixture with heat or light, etc. to form a refractive index distribution in the radial direction, or (3) forming a reticular polymer (including copolymer) Pa having a refractive index na a monomer Ma,
A polymerization initiator and a monomer Mb forming a polymer Pb having a refractive index nb different from the refractive index na are mixed, and a portion other than the hollow portion is filled with a light absorbing member, and an inner wall surface of the hollow portion is formed. The mixture is injected into a container in which a plurality of hollow cylinders each covered with a material substantially the same as the Pb are arranged in a plate shape, the mixture is polymerized by heat or light, and the mixture is polymerized in the radial direction. The thickness T of the plate-shaped lens array created by forming a refractive index distribution is P, and the ray meandering period of the refractive index distribution lens is P, satisfying the relationship P/2≦T≦P to obtain an erect, same-magnification image. It is characterized by forming a lens array so as to obtain the desired results. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a diagram for explaining an embodiment of the optical element manufacturing method according to the present invention, in which 1 indicates a frame;
2 is a hollow part. Monomer M forming a network polymer (including copolymer) Pa having a refractive index na in the hollow portion 2
a, a polymerization initiator, and a monomer Mb forming a polymer Pb having a refractive index nb different from the refractive index na, and the hollow part 2 except the hollow part 2 is filled with a light absorbing member, and the The polymer Pb is injected into a hollow cylindrical container, ie, the frame 1, in which the inner wall surface of the hollow portion 2 is made of substantially the same material as the polymer Pb, and polymerized by heating to form a refractive index distribution in the radial direction. The example in FIG. 1 shows a rectangular outer shape. When filling the inside of the frame 1 with monomer liquid, sealing one side with the plate 4 can prevent the liquid from leaking.

[0008] Here, the frame 1 is made of PMMA, PC, PS, ABS, or AS in which a light absorbing agent such as carbon is dispersed.
etc. are made by injection molding, pouring molding, etc. Monomer M
As a, for example, a monomer having two or more types of groups responsible for polymerization is selected, such as methacrylate-based ethylene dimethacrylate, benzyl methacrylate, and β-methallyl methacrylate. As monomer Mb, for example, 2.2
．． A fluorine-containing methacrylic acid monomer such as 2-trifluoroethyl methacrylate, 1.1.5-trihydroperfluoropentyl methacrylate, benzyl acrylate, vinyl phenyl acrylate, etc. is selected. The refractive index of the polymer Pa of the monomer Ma is na,
When the refractive index of the polymer Pb of the monomer Mb is nb, na>nb. Further, any polymerization initiator such as hydroquinone or benzyl peroxide can be used. Before filling the monomers Ma and Mb, a thin layer is formed on the inner wall of the hollow part of the frame 1 using the same material monomer as the material used as the monomer Mb (formed by a method such as a spraying method or a dipping method), and then a thin layer is formed by a method such as a heating method. Polymerize to form a reaction layer for the next step.

FIG. 2 shows a process for forming a refractive index distribution. In the figure, 3 is a monomer filler, 4 is a base plate, 5 is a gelled surface, 11 is a thin layer, and other parts having the same functions as in FIG. 1 are given the same reference numerals. The left side of the figure shows the process, and the right side shows the refractive index distribution. Figure (a) shows a state in which only the frame 1 is used, Figure (b) shows a state in which the hollow part of the frame is filled with a monomer mixture of two types of Ma and Mb, and Figure (c) shows a state in which the frame is assembled after heating has started. Figure (d) shows a state in which gelation starts from the boundary with the mixed monomer, and a state in which polymerization is completed and a refractive index distribution is formed in the radial direction around the optical axis.

FIG. 3 is a diagram showing another embodiment of the method for producing an optical element according to the present invention. In the figure, 6 is a frame having a cylindrical outer shape. The shape of this frame 6 can be selected to be an optimal shape depending on the purpose.

FIG. 4 is a diagram showing still another embodiment of the optical element manufacturing method according to the present invention. In the figure, 7 is a frame having a rectangular parallelepiped outer shape. A monomer Ma forming a network polymer (including copolymers) Pa having a refractive index na, a polymerization initiator,
Then, a monomer Mb forming a polymer Pb having a refractive index nb different from the refractive index na is mixed, and a plurality of hollow cylinders are densely arranged in a plate shape, and the parts other than the hollow part are exposed to light. The hollow part is filled with an absorbent material, and the inner wall of the hollow part is made of polymer P.
It is injected into a container made of a polymeric material, that is, the frame 7, which is coated with the same material as in b, and polymerized by heating to form a refractive index distribution in the radial direction.

FIG. 5 is a diagram showing the state of image synthesis when formed on an array lens. By setting specifications so that each lens covers an area larger than the diameter of each lens, images formed by each lens can be combined.

FIG. 6 is a diagram showing still another embodiment of the optical element manufacturing method according to the present invention. The lenses are arranged in a staggered manner in order to further reduce the non-uniformity of the combined light amount distribution (light amount unevenness) between the two-dimensionally arranged lenses. By doing so, it is possible to reduce unevenness in the amount of light that occurs depending on the arrangement period of the lenses.

FIG. 7 is a diagram showing a state in which an erect real image is formed by appropriately determining the thickness T of the GRIN lens array. In this example, the lens thickness is (3/4)P(P
:The beam meandering period of the GRIN lens).

FIGS. 8A and 8B show examples in which one or two rows of lens arrays are formed, and are used as image forming elements in facsimile machines, document reading sections of image scanners, optical printer heads, and the like.

[0016]

[Effects] As is clear from the above description, the present invention has the following effects. (1) Effect corresponding to claim 1: Since the frame that forms the gradient index lens is formed of a light-absorbing material, unnecessary light from other than the lens aperture can be blocked, eliminating the need for lens cells, etc. The structure becomes easier. In addition, the frame can be processed into the desired shape from the beginning,
Effects such as easier assembly can also be expected. In addition, the frame body is made of a light-absorbing material, and the inner wall surface of the hollow part that forms the lens is coated with a transparent thin layer using Mb monomer, so when the Mb and Ma monomers polymerize, the inner wall Polymerization is initiated between the formed Mb polymer and a diffusion layer is formed, but the Mb polymer layer formed on the inner wall acts as a barrier and can prevent the light absorption member of the frame body from diffusing into the lens portion. (2) Effect corresponding to claim 2: Since the base plate forming the gradient index lens is formed of a light absorbing member, crosstalk between adjacent lenses can be reduced and imaging performance can be improved. (3) Effect corresponding to claim 3: By appropriately determining the arrangement position and length of the GRIN lens to satisfy the relationship of obtaining an erect equal-magnification image, and by configuring the configuration to enable image synthesis between the lenses, any desired effect can be obtained. Lens arrays covering the area can be easily obtained.

[Brief explanation of the drawing]

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

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

FIG. 3 is a diagram showing another embodiment of the optical element manufacturing method according to the present invention.

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

FIG. 5 is a diagram showing a state of image synthesis when formed in a lens array.

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

FIG. 7 is a diagram showing how an erect real image is formed by appropriately determining the thickness of the GRIN lens array.

FIG. 8 is a diagram showing an example in which one or two rows of lens arrays are formed.

[Figure 9] Radial GR in interfacial gel heterogeneous copolymerization method
It is a figure which shows the procedure diagram of IN waveguide.

FIG. 10 shows a 2-D radial GRIN lens array.

FIG. 11 is a diagram showing strokes between adjacent lenses.

[Explanation of symbols]

1 Frame 2 Hollow part

Claims (3)

[Claims] 1. A monomer Ma forming a network polymer (including copolymer) Pa having a refractive index na, a polymerization initiator, and a polymer Pb having a refractive index nb different from the refractive index na. The mixture is placed in a hollow cylindrical container in which the part other than the hollow part is filled with a light-absorbing member and the inner wall surface of the hollow part is covered with a material substantially the same as the Pb. 1. A method for producing an optical element, which comprises injecting the mixture and polymerizing the mixture using heat or light to form a refractive index distribution in the radial direction. 2. A monomer Ma forming a network polymer (including copolymer) Pa having a refractive index na, a polymerization initiator, and a polymer Pb having a refractive index nb different from the refractive index na. A plurality of hollow cylinders are formed by mixing the monomer Mb forming the above-mentioned Pb, filling the part other than the hollow part with a light absorbing member, and the inner wall surface of the hollow part is covered with a material substantially the same as the Pb. A method for producing an optical element, characterized in that the mixture is injected into containers arranged closely in a plate shape, and the mixture is polymerized by heat or light to form a refractive index distribution in the radial direction. 3. A monomer Ma forming a network polymer (including a copolymer) Pa having a refractive index na, a polymerization initiator, and a polymer Pb having a refractive index nb different from the refractive index na. A plurality of hollow cylinders are formed by mixing the monomer Mb forming the above-mentioned Pb, filling the part other than the hollow part with a light absorbing member, and the inner wall surface of the hollow part is covered with a material substantially the same as the Pb. The thickness T of a plate-shaped lens array created by injecting the mixture into a container arranged densely in a plate shape, polymerizing the mixture with heat or light, etc., and forming a refractive index distribution in the radial direction. A method for producing an optical element, characterized in that the lens array is formed so as to satisfy the relationship of P/2≦T≦P and obtain an erect equal-magnification image, where P is the meandering period of the light rays of the gradient index lens.