Planar microlens array and method of making same
First Claim
1. A method of manufacturing a planar microlens array having a multitude of refractive-index distribution type microlenses of a polygonal circumferential shape arranged two-dimensionally and periodically on the surface of a planar transparent substrate, characterized in that said method includes the steps of:
- preparing a planar transparent substrate,forming on the surface of said substrate a diffusion-inhibiting mask film having a multitude of periodically arranged mask apertures of a shape enclosed by straight lines that are parallel with and disposed at a predetermined interval inwardly away from sides of said polygonal circumferential shape, andforming microlenses over the almost entire surface of said substrate by diffusing in said substrate a substance contributing to increasing the refractive index of said substrate through said mask apertures.
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Abstract
A microlens array of high converging efficiency is provided, independently of the array and lens filling rate of microlens arrays, with a method of manufacturing microlens arrays using the diffusion process. A multitude of refractive-index distribution type microlenses formed by diffusing in a planar transparent substrate a substance contributing to increasing the refractive index of the substrate are two-dimensionally and regularly arranged on the surface of the substrate. The microlenses are densely arranged on the surface of the substrate, and diffusion fronts of the microlenses form regions where the diffusion fronts are fused with those of the adjoining microlenses. The length of a region where certain two adjoining microlenses are fused together, in the direction of a straight line connecting the centers of the two microlenses is less than 20% of the array pitch of the microlenses in the above-mentioned direction.
25 Citations
18 Claims
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1. A method of manufacturing a planar microlens array having a multitude of refractive-index distribution type microlenses of a polygonal circumferential shape arranged two-dimensionally and periodically on the surface of a planar transparent substrate, characterized in that said method includes the steps of:
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preparing a planar transparent substrate, forming on the surface of said substrate a diffusion-inhibiting mask film having a multitude of periodically arranged mask apertures of a shape enclosed by straight lines that are parallel with and disposed at a predetermined interval inwardly away from sides of said polygonal circumferential shape, and forming microlenses over the almost entire surface of said substrate by diffusing in said substrate a substance contributing to increasing the refractive index of said substrate through said mask apertures. - View Dependent Claims (3, 4, 5, 6)
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2. A method of manufacturing a planar microlens array having a multitude of refractive-index distribution type microlenses of a polygonal circumferential shape arranged two-dimensionally and periodically on the surface of a planar transparent substrate, characterized in that said method includes the steps of:
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preparing a planar transparent substrate, forming on the surface of said substrate a diffusion-inhibiting mask film having a multitude of periodically arranged mask apertures of a shape connecting curves or broken lines passing inside straight lines that are parallel with and disposed at a predetermined interval inwardly away from sides of said polygonal circumferential shape, and forming microlenses over the almost entire surface of said substrate by diffusing in said substrate a material contributing to increasing the refractive index of said substrate through said mask apertures. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13)
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14. A method of manufacturing a planar microlens array having a multitude of refractive-index distribution type microlenses arranged two-dimensionally and periodically on the surface of a planar transparent substrate, characterized in that said method includes the steps of:
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preparing a planar transparent substrate, forming a diffusion-inhibiting mask film having a multitude of two-dimensionally and periodically arranged mask apertures on the surface of said substrate, and forming microlenses on the surface of said substrate by diffusing in said substrate a substance contributing to increasing the refractive index of said substrate through said mask apertures, in such a manner that said microlenses are densely arranged on the surface of said substrate, diffusion fronts of said microlenses form regions where said diffusion fronts are fused with diffusion regions of adjoining microlenses, and the length, in the direction of a straight line connecting centers of adjoining two microlenses, of said regions where said two microlenses are fused together becoming less than 20% of an array pitch of said microlenses in said direction. - View Dependent Claims (16, 17)
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15. A method of manufacturing a planar microlens array having a multitude of refractive-index distribution type microlenses arranged two-dimensionally and periodically on the surface of a planar transparent substrate, characterized in that said method includes the steps of:
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preparing a planar transparent substrate, forming a diffusion-inhibiting mask film having a multitude of two-dimensionally and periodically arranged mask apertures on the surface of said substrate, and forming microlenses on the surface of said substrate by diffusing in said substrate a substance contributing to increasing the refractive index of said substrate through said mask, in such a manner that said microlenses are densely arranged on the surface of said substrate, and diffusion fronts of said microlenses come in contact in a linear form with, but are not fused with, diffusion fronts of adjoining microlenses.
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18. A method of manufacturing a planar microlens array having a multitude of refractive-index distribution type microlenses arranged two-dimensionally and periodically on the surface of a planar transparent substrate, characterized in that said method includes the steps of:
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preparing a planar transparent substrate, forming a diffusion inhibiting mask film having a multitude of two-dimensionally and periodically arranged mask apertures on the surface of said substrate, and forming microlenses of a polygonal circumferential shape over the almost entire surface of said substrate by diffusing in said substrate a substance contributing to increasing the refractive index of said substrate through said mask apertures, and wherein the shape of said mask apertures is set in said diffusion-inhibiting mask film forming step so that diffusion fronts corresponding to the sides of the microlenses being formed become linear.
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Specification