Planar microlens array and method of making same

Details Planar microlens array and method of making same Planar microlens array and method of making same

1996-12-13

1999-02-02

Epps, Georgia Y.

Optical: systems and elements

Single channel simultaneously to or from plural channels

By surface composed of lenticular elements

359620, 359900, G02B 2710

Patent

active

058673210

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates generally to a planar microlens array and a method of making the same, and more particularly to a planar microlens array that is useful as a converging lens to converge light for illuminating a transmissive image display panel, such as a liquid crystal display panel having a plurality of pixels, onto pixel apertures to make the liquid crystal display panel brighter, and a method of making the same.


BACKGROUND ART

This type of planar microlens array was disclosed by Hamanaka, et al. in Japanese Patent Publication No. 3-136004 (Refer to FIG. 1). The planar microlens array disclosed in the Publication is manufactured using the ion diffusion process. In the ion diffusion process, a glass substrate is used as a transparent substrate 1 on the surface of which a diffusion-inhibiting mask film comprising Ti, Al, Ni or Cr, etc. is formed using the sputtering and other thin-film forming processes, and then a desired array of circular mask apertures is formed on the diffusion-inhibiting mask film. After that, the transparent substrate is immersed for a predetermined period of time in a molten-salt bath containing ions contributing to increasing the refractive index of the substrate. As ions in the molten-salt bath are diffused through the mask apertures in the transparent substrate, a planar microlens array 82 having a plurality of microlenses of a refractive-index distribution type with decreasing refractive index from the vicinity of the center of each mask aperture toward the circumference thereof is formed. In a liquid crystal display panel having a delta (six-lobe) pixel array, this planar microlens array has microlenses of a hexagonal circumferential shape that are arranged two-dimensionally, regularly and densely on the surface of the transparent substrate, as shown in FIG. 1. In this case, the lens array is a six-lobe array.
The circumferential shape of each microlens can be made into a desired hexagonal shape by providing a region 6 where the diffusion fronts 5 that are leading edges of the microlens ion diffused areas of the adjoining microlenses 4 are fused together, as shown in FIG. 2. In this case, lens filling rate, the ratio of the area occupied by microlenses to the total area of the transparent substrate on which lenses are formed, is almost 100%.
Oikawa et al., on the other hand, disclosed a planar microlens array for use in liquid crystal display panels in Japanese Patent Publication No. 5-45642 (Refer to FIG. 3). A planar microlens array 82 is formed with the ion diffusion process using a diffusion-inhibiting mask film having formed oblong mask apertures. This planar microlens array 82 has microlenses 4 of an oblong circumferential shape, as shown in FIG. 4, by terminating ion diffusion in the state where diffusion fronts of the adjoining microlenses come in contact with each other. With this, the lens filling rate is short of 100% because of the existence of a lens unformed region where no lenses are formed, but a planar microlens array 82 having a relatively high lens filling rate is formed since the lens array is of a six-lobe type.
These planar microlens arrays are suitable for condenser lenses to illuminate display images by converging light to illuminate a transmissive display panel, such as a liquid crystal display panel having a plurality of pixels, onto pixel apertures. A typical projection-type image display device having such a planar microlens array is shown in FIG. 5.
In FIG. 5, the light emitted by a light source 86 is converged by a reflecting mirror 87 and a condenser lens 85 so as to direct toward a projection lens 89. The light flux passing through the condenser lens 85 is converged by a planar microlens array 82 onto a pixel aperture area (pixel aperture) 81b of a liquid crystal element formed between two substrates 81a of a liquid crystal panel 81, and projected onto a screen 88 by the projection lens 89.
By using a planar microlens array as described above, the light flux that would otherwise been shielded by the pixel shieldin

REFERENCES:
patent: 4332438 (1982-06-01), Green
patent: 4695719 (1987-09-01), Wilwerding
patent: 5337186 (1994-08-01), Oikawa et al.
patent: 5359440 (1994-10-01), Hamada et al.
patent: 5381187 (1995-01-01), Takamatsu et al.
patent: 5519539 (1996-05-01), Hoopman et al.
patent: 5581379 (1996-12-01), Aoyama et al.
patent: 5715022 (1998-02-01), Takamatsu et al.
European Patent Office Search Report, Apr. 7, 1997.

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