JP3071838B2 - 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 method for producing a gradient index lens in which a refractive index distribution exists in a radial direction, 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 Known documents that describe the prior art according to the present invention include, for example, Y. Koike Y. Takezawa and Y. Ohtsuk.
a, `` NewInterfacial-gel copolymerization technique f
or steric GRIN polymer optical waveguides and lens
arrays "(Appl. Opt. 27, 3, P. 486 to P. 491, 1988).
This is an Inerfacial-gel copolymerizaation techniqu
e, that is, a method for preparing a lens array using an interfacial gel heterogeneous copolymerization method.

A plurality of holes are formed in a transparent plastic plate of PMMA (polymethyl methacrylate) to form a hollow portion, and MMA (methyl methacrylate) and VPac (vinyl) are formed.
phenylacetate) at a ratio of 4/1 (wt./wt.), add hydroquinone as a polymerization initiator to the liquid monomer, and inject into the above-mentioned hollow portion and heat. Next, the surface of the PMMA is swollen by the liquid monomer to form a gel layer. Next, copolymerization starts in the gel (gel effect), and the reaction proceeds to the center. The refractive index distribution is formed as follows. The refractive index n and the reactivity r of the mixed monomer are determined by MMA
(N _m, r _m) and VPAc (n _v, r _v) is in a, n _m <
_{n v, r m> 1,} r v <1 , and the near portion (the outer peripheral portion) in the pipe wall of the PMMA has a high low high refractive index reactive MMA composition ratio, the ratio of VPAc toward the center of the cylinder Get higher. Therefore, the refractive index distribution is formed in the radial direction so that the refractive index gradually decreases from the center of the cylinder toward the periphery.

FIGS. 9A to 9D are procedure 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 the transparent plastic member, as shown in FIG. 11, the crosstalk between adjacent lenses is large (a large amount of light other than the effective imaging light is transmitted to the image plane). The performance is significantly reduced. In addition, the arrangement position of the lens and GR
The length of the IN lens is not sufficiently set, and the image cannot be synthesized in space.

[0005]

The present invention has been made in view of the above situation, and has a structure in which a base plate (frame) forming a gradient index lens is formed of a light absorbing member to reduce crosstalk between adjacent lenses. To improve the imaging performance
In addition, the inner wall of the hollow portion forming the lens of the base plate (frame) forming the gradient index lens is coated with the same transparent material as the constituent material of the monomer forming the lens to form a barrier layer. To prevent the light absorbing member of the frame from being diffused to the diffused portion with the inner wall of the base, which is generated when the refractive index distribution lens is formed by polymerization, to reduce the transmission loss. Further, the arrangement position and the length of the GRIN lens are reduced. An object of the present invention is to provide a method for producing an optical element which satisfies a relationship for obtaining an erect equal-magnification image appropriately and is capable of synthesizing an image between lenses so as to easily obtain a lens array covering an arbitrary area. It was made for the purpose.

[0006]

To achieve the above object, the present invention provides (1)
Reticulated polymer having a refractive index n _a (containing a copolymer) Pa
And a polymerization initiator, and the refractive index n
mixing a monomer Mb of forming a polymer Pb having different refractive index n _b and _a, except the hollow portion is filled formed of a light absorbing member, the inner wall surface of the hollow portion at least the Mb
The mixture is polymerized by heat or light or the like in a hollow cylindrical container coated with a material obtained by polymerizing the material to be formed, thereby forming a refractive index distribution in the radial direction, or (2) having _a refractive index na. a monomer Ma to form a Pa (including copolymer) reticulated polymer, a polymerization initiator, and the refractive index n _a and monomer Mb of forming a polymer Pb having different refractive index n _b is And the other part is filled with a light absorbing member, and the inner wall surface of the hollow part contains at least Mb.
The mixture hollow cylinder that is coated formed by were polymerized material free material in a container which is arranged a plurality densely plate
Polymerizing by heat or light to form a refractive index distribution in the radial direction, or (3) a monomer Ma forming a network polymer (including a copolymer) Pa having _a refractive index n _a
When a polymerization initiator, different refractive index n _b and the refractive index n _a
Is mixed with a monomer Mb to form a polymer Pb having
A plurality of hollow cylinders densely filled with a light-absorbing member other than the hollow portion and having an inner wall surface coated with a material obtained by polymerizing at least the material containing Mb are densely packed. The thickness T of the plate-shaped lens array created by polymerizing the mixture by heat or light in a container arranged in a shape by forming a refractive index distribution in the radial direction is determined by the light meandering cycle of the refractive index distribution lens. The lens array is formed such that P satisfies the relationship of P / 2 ≦ T ≦ P and obtains an erect equal-size image. Hereinafter, a description will be given based on examples of the present invention.

FIG. 1 is a view for explaining an embodiment of a method for producing an optical element according to the present invention, wherein 1 is a frame,
2 is a hollow part. Monomer M that forms a reticulated polymer (including a copolymer) Pa having _a refractive index n _a in the hollow portion 2
a, polymerization initiator, and, said mixture of a monomer Mb of forming a polymer Pb having different refractive index n _b and the refractive index n _a, except the hollow portion 2 is filled formed of a light absorbing member The inner wall surface of the hollow portion 2 contains at least the above Mb.
The material is poured into a hollow cylindrical container formed of a polymerized material , that is, the frame 1, and is heated and polymerized to form a refractive index distribution in the radial direction. The example in FIG. 1 shows a case where the outer shape is rectangular. If one side is sealed with the plate 4 when filling the frame 1 with the monomer liquid, the liquid can be prevented from leaking.

Here, the frame 1 is made of PMMA, PC, PS, ABS, AS in which a light absorber such as carbon is dispersed.
Etc. are created by a method such as injection molding or injection molding. Monomer M
As a, for example, a monomer having two or more types of groups that control polymerization, such as methacrylate-based ethylene dimethacrylate, benzyl methacrylate, and β-methallyl methacrylate, is selected. As the monomer Mb, for example, 2.
A fluorine-containing methacrylic acid-based monomer such as 2.2 trifluoroethyl methacrylate, 1.1.5 trihydroperfluoropentyl methacrylate, or benzyl acrylate or vinyl phenyl acrylate is selected. 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. Before filling the monomers Ma and Mb, the frame 1
A thin layer is formed on the inner wall of the hollow part with 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 polymerized by a method such as heating to form a reaction layer in the next step.

FIG. 2 shows a process of forming a refractive index distribution. In the figure, 3 is a filler of monomer, 4 is a base plate, 5 is a gelled surface, 11 is a thin layer, and other parts that have the same effect as in FIG. 1 are denoted by the same reference numerals. The left side of the figure shows the steps, and the right side shows the refractive index distribution. Fig. (A) shows a state of only the frame 1, Fig. (B) shows a state in which a monomer in which two kinds of Ma and Mb are mixed is filled in a hollow portion of the frame, and Fig. FIG. 4D shows a state in which gelation has started from the boundary with the mixed monomer, and FIG. 4D shows a state in which polymerization has been completed and a refractive index distribution has been formed in the radial direction around the optical axis.

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. The shape of the frame 6 can be selected to an optimum shape depending on the application.

FIG. 4 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 monomer Ma for forming a network polymer (including a copolymer) Pa having _a refractive index na, a polymerization initiator,
And, a mixture of monomers Mb of forming a polymer Pb having different refractive index n _b and the refractive index n _a, hollow cylinder is disposed a plurality densely plate, except the hollow portion Is filled with a light absorbing member, and the inner wall of the hollow portion is a polymer Pb.
A polymer material container formed by coating with the same material as
That is, it is injected into the frame 7 and polymerized by heating to form a refractive index distribution in the radial direction.

FIG. 5 is a diagram showing an image combining state when formed on an array lens. 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.

FIG. 6 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.

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: light meandering cycle of GRIN lens).

FIGS. 8A and 8B show an example in which a lens array of one or two rows is formed, which is used as a facsimile, a document reading section of an image scanner, or an image forming element such as an optical printer head.

[0016]

As apparent from the above description, the present invention has the following effects. (1) An effect corresponding to claim 1; since the frame forming the gradient index lens is formed by the light absorbing member, unnecessary light from portions other than the lens opening can be blocked, and a lens cell and the like are not required. The structure becomes easy. Also, the frame can be processed to the required shape from the beginning,
Effects such as easy assembly can also be expected. In addition, since the frame body is formed of a light absorbing member and a transparent thin layer is formed on the inner wall surface of the hollow portion forming the lens using Mb monomer, the inner wall is formed when the Mb and Ma monomers are polymerized. Polymerization is started between the formed Mb polymer and the diffusion layer is formed. However, the Mb polymer layer formed on the inner wall serves as a barrier, and can prevent diffusion of the light absorbing member of the frame body to the lens portion. (2) An effect corresponding to the second aspect: Since the base plate forming the gradient index lens is formed of the light absorbing member, crosstalk between adjacent lenses can be reduced, and the imaging performance can be improved. (3) Effect corresponding to claim 3; Arrangement position and length of the GRIN lens are appropriately determined so as to satisfy the relationship of obtaining an erecting equal-magnification image, and an arbitrary composition can be obtained by combining the lenses. A lens array covering the area can be easily obtained.

[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 diagram showing an image combining state when formed on a lens array.

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 a state of forming an erect real image obtained 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.

FIG. 9: Radial GR in the interfacial gel heterogeneous copolymerization method
It is a figure which shows the procedure diagram of an IN waveguide.

FIG. 10 is a diagram showing a 2-D radial GRIN lens array.

FIG. 11 is a diagram illustrating a stroke between adjacent lenses.

[Explanation of symbols]

 1 frame 2 hollow part

Claims (3)

(57) [Claims] Has a 1. A (containing a copolymer) reticulated polymer having a refractive index n _a monomer forming the Pa Ma, a polymerization initiator, a different refractive index n _b and the refractive index n _a mixing a monomer Mb of forming a polymer Pb, except the hollow portion is filled formed of a light absorbing member, small inner wall surface of the hollow portion
Producing an optical element, wherein the mixture is polymerized by heat or light or the like in a hollow cylindrical container coated with a material obtained by polymerizing the material containing at least Mb to form a refractive index distribution in a radial direction. Method. A 2. A (containing a copolymer) reticulated polymer having a refractive index n _a monomer forming the Pa Ma, a polymerization initiator, a different refractive index n _b and the refractive index n _a mixing a monomer Mb of forming a polymer Pb, except the hollow portion is filled formed of a light absorbing member, small inner wall surface of the hollow portion
At least, the mixture is polymerized by heat or light or the like in a container in which a plurality of hollow cylinders formed by coating a material obtained by polymerizing the material containing Mb are densely arranged in a plate shape, and refracted in a radial direction. A method for producing an optical element, comprising forming a rate distribution. A 3. A (containing a copolymer) reticulated polymer having a refractive index n _a monomer forming the Pa Ma, a polymerization initiator, a different refractive index n _b and the refractive index n _a mixing a monomer Mb of forming a polymer Pb, except the hollow portion is filled formed of a light absorbing member, small inner wall surface of the hollow portion
At least, the mixture is polymerized by heat or light or the like in a container in which a plurality of hollow cylinders formed by coating a material obtained by polymerizing the material containing Mb are densely arranged in a plate shape, and refracted in a radial direction. The thickness T of the plate-shaped lens array formed by forming the refractive index distribution is set such that the light meandering period of the refractive index distribution lens is P, and the relationship of P / 2 ≦ T ≦ P is satisfied to obtain an erect equal-size image. A method for producing an optical element, characterized in that a lens array is formed on the optical element.