Optics: image projectors – Reflector
Reexamination Certificate
2000-02-04
2003-04-15
Mathews, Alan A. (Department: 2851)
Optics: image projectors
Reflector
C353S031000, C353S037000, C353S038000, C353S094000, C349S005000, C349S007000, C345S039000, C345S046000, C345S082000, C345S083000
Reexamination Certificate
active
06547400
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection-type liquid-crystal display device such as a light source device used in a projector, and particularly to a compact light source device suitable for use in a compact projector.
2. Description of the Related Art
In conventional practice, projectors in which images on liquid-crystal display elements are magnified, projected, and displayed are configured such that a single liquid-crystal display element is illuminated by a metal halide lamp from behind, and the image displayed by the liquid-crystal display element is magnified and projected by a projection lens.
For example, Japanese Unexamined Patent Applications (Kokai) 62-237485, 3-75737, and 8-111107 describe inventive structures in which a metal halide lamp or a halogen lamp are used as the light source, and light emitted by this light source is transmitted through a hollow light-guide structure and directed toward a liquid-crystal display element.
The above-described prior art, however, involves using a lamp as the light source, and is limited in the degree to which the size of the light source as such can be reduced. It is thus difficult to reduce the size of the projector as a whole. Portable communication terminal devices have appeared in recent years, dispensing with the need to project images to dimensions in excess of 60 inches with such projectors. It is proposed, for example, that the size of a projected image be reduced to about 10 or 20 inches. At this size of a projected image, a light-emitting element (light-emitting diode, semiconductor laser, etc.) or the like can be used as the light source, making it possible to design very small projectors.
Light-emitting elements and other miniature light-emitting devices are substantially point light sources, and it is therefore difficult to uniformly illuminate a liquid-crystal display element having a given surface area. An attempt to line up a plurality of light-emitting diodes and to illuminate a wide surface area ultimately yields an assembly of point light sources, resulting in a nonuniform distribution of light intensity in a two-dimensional plane.
Japanese Unexamined Patent Application 10-123512 discloses projector technology in which the light source is made up of a two-dimensional array of light-emitting diodes. Light from the light-emitting diodes is converted to planar light by microlens array (an array of lens elements formed in conformity with the light-emitting diodes) in order to allow light radiated by the light-emitting diodes (point light sources) to be directed toward liquid-crystal display elements in an efficient manner.
Such microlens arrays are disadvantageous, however, in that the lens action along the border between adjacent lens elements becomes weak as a result of manufacturing errors or the like, making it difficult to create uniform illumination light.
According to another arrangement, which is disclosed in Japanese Unexamined Patent Application 9-73807, the optical axis can be curved 90° to guide the light, but a technique has yet to be found that would allow the optical axis of a point light source to advance in a straight line, yielding planar light.
SUMMARY OF THE INVENTION
An object of the present invention, which was perfected in view of the above-described situation, is to provide a light source structure in which a plurality of point light sources are arranged in a planar configuration and which is suitable for miniaturization. Another object of the present invention is to provide a compact light source capable of displaying projected images having uniform light intensity by designing a structure capable of emitting uniform light through the use of a plurality of light-emitting diodes or other point light sources for illumination purposes.
The present invention resides in a light source device comprising light guide means that is provided with mutually opposite end faces and that has a light guide function whereby light entering through one end face is guided to and emitted from the other end face, and a point light source array that is a separate entity from the light guide means and that is obtained by arranging a plurality of point light sources in a planar configuration along one of the end faces of the light guide means.
The present invention also resides in a light source device comprising the following separate entities: a point light source array obtained by arranging a plurality of point light sources in a planar configuration, and light guide means in which light from the point light source array is admitted through at least one end, mixed, guided to the other end face, and emitted.
As a result of thoroughgoing research aimed at miniaturizing light sources and concerned with the relation between light guide means and planar point light source arrays, the inventor discovered that the stated object can be attained by providing a rectilinear or serial arrangement for the surface through which light is admitted into the light guide means and the surface through which the light admitted into the light guide means is allowed to escape in relation to the point light sources, and by the uniform dispersion of light received from the point light sources throughout the light guide body.
Based on the above discovery, the present invention has the following distinctive features.
The present invention is characterized in that the aforementioned point light sources are light-emitting elements that emit monochromatic light. Such light-emitting elements include light-emitting diodes (hereinafter “LEDs”), semiconductor lasers (LDs), and other point light sources, and are not limited in terms of emitted color. In other words, monochromatic elements (for example, white LEDs or light-emitting diodes that emit B (blue) light) may also be used.
When B (blue) light or other monochromatic light is used, wavelength conversion elements for converting this light to white light should preferably be disposed in the optical path.
The present invention is also characterized in that the aforementioned point light sources are light-emitting elements that differ in color, and the aforementioned point light source array is a combination of such light-emitting elements.
Such a combination of light-emitting elements may be a combination of three colors (RGB), a combination that includes colors other than these three colors (for example, orange and yellow green), or a combination of two, four, or more colors.
The present invention is further characterized in that the aforementioned light guide means is a hollow or solid light guide body, preferably composed of a transparent material. A first aspect of this light guide body is a hollow light guide block, which may be polygonal prismatic or cylindrical in shape. Reflecting metal surfaces may also be provided to the lateral surfaces (inner wall surfaces and inner peripheral surfaces) of the hollow light guide block.
A second aspect of the light guide body is a solid (rather than hollow) light guide block. Total reflection surfaces or reflecting metal surfaces may also be provided to the lateral surfaces of the solid light guide block. The light guide body may also be configured as a so-called Selfoc lens, which is obtained by forming a bundle from a plurality of optical fibers having a cladding and a core.
Another aspect of the present invention is an optical device comprising the aforementioned light source device and a member located opposite the end face for emitting the light of the light guide means and designed to modulate the light from the light guide means. Yet another aspect of the present invention is a liquid-crystal display device characterized in that this member is a liquid-crystal display element. According to this embodiment of the liquid-crystal display device, a magnifying lens is disposed in the optical path of the emitted light optically modulated by the aforementioned liquid-crystal display element. It is also possible to provide a screen configured such that the image of the liquid-crystal disp
Koval Melissa
Mathews Alan A.
Seiko Epson Corporation
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