Optics: image projectors – Reflector
Reexamination Certificate
2000-04-25
2002-10-29
Dowling, William (Department: 2851)
Optics: image projectors
Reflector
C353S031000, C353S094000
Reexamination Certificate
active
06471358
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a compact, small-sized lighting device including at least two lamp units and having a high utilization efficiency of light. The present invention also pertains to a projector-type display apparatus with such a lighting device for producing bright projected images which are uniform in brightness.
2. Discussion of the Background
A lighting device incorporated in projector-type display apparatus generally has a lamp unit, which includes a light source lamp, such as a halogen lamp or a metal halide lamp, and a reflector for reflecting an incident ray emitted from the light source lamp and outputting the reflected ray as a parallel beam or a converging beam in a predetermined direction. Available reflectors have the reflecting surfaces in the shape of paraboloid or ellipsoid.
It is preferable that the lighting device used in the projector-type display apparatus has a large output quantity of light, in order to produce uniform and bright projected images. Further a compact, small-sized lighting device is desirable when being incorporated in portable projector-type display apparatus.
The lighting device may include a plurality of lamp units, for example, two lamp units, in order to increase the output quantity of light. A simple array of the two lamp units in parallel, however, doubles the width of the lighting device and makes the lighting device undesirably bulky. This arrangement also doubles the width of the flux of output light and requires an extended width of the optical path in the lighting device. This further doubles the required width of the optical path formed in the projector-type display apparatus with such a lighting device incorporated therein. This arrangement is thus not suitable for the requirement of the compact, small-sized structure.
A typical example of the lighting device incorporated in the projector-type display apparatus is a lamp unit including a light source lamp having a short arc length and a reflector of a paraboloidal shape having a short focal distance. The distribution of the quantity of light emitted from the lamp unit of this structure is shown as a characteristic curve that has a sharp peak on and in the vicinity of a lamp optical axis and abruptly decreases with a distance from the lamp optical axis. The use of only the light fluxes in a central portion including the lamp optical axis for illumination does not significantly lower the quantity of light.
SUMMARY OF THE INVENTION
The object of the present invention is thus to provide a technique for providing a lighting device with a plurality of lamp units and a projector-type display apparatus with such a lighting device incorporated therein, which can produce projection images that are bright, uniform in brightness, and even in color.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
(First Lighting Device and Projector-type Display Apparatus therewith)
At least part of the above and the other related objects is attained by a first lighting device of the present invention, which includes a lamp unit having a light source lamp and a reflector for reflecting light emitted from the light source lamp, the lighting device further including a plurality of the lamp units arrayed in a direction perpendicular to an optical axis of the light source lamp, wherein the reflector of each the lamp unit has a shape obtained through cutting a concave surface of revolution, which is obtained by rotating a curve about the optical axis of the light source lamp, on at least one end adjoining to another lamp unit by a plane substantially perpendicular to a direction of the array of the lamp units.
The plurality of lamp units may be arrayed in one direction substantially perpendicular to the optical axis of the light source lamp, or in two directions each substantially perpendicular to the optical axis of the light source lamp.
In a lamp unit with a reflector, the quantity of output light is extremely large in a central portion including an optical axis of a light source lamp and decreases with a distance from the optical axis of the light source lamp. In the first lighting device of the present invention, the reflector of each lamp unit is cut to have a narrow width. This reduces the total width of the lighting device. This structure with narrow reflectors effectively utilizes the output light in the central portion including the lamp optical axis and thereby ensures a sufficient amount of output light. The lighting device of the present invention ensures a greater quantity of output light, while having substantially the same size as that of the conventional lighting device with only one lamp unit. The lighting device of the present invention is preferably used as a light source of a projector-type display apparatus that displays bright projection images.
In accordance with one preferable application, the reflector has a shape obtained through both ends of the concave surface of revolution by the plane substantially perpendicular to the direction of the array of the lamp units, and a distance between both of cut faces is approximately half a diameter of an opening of the concave surface of revolution. Especially two lamp units arrayed in one direction have the quantity of output light as much as about 1.5 times the conventional lighting device with a single lamp unit, while making the width of the lighting device substantially the same. This arrangement enables the projector-type display apparatus to utilize an optical system designed for a lamp unit having a reflector with no side cuts.
In accordance with another preferable application, the reflectors included in the plurality of lamp units are optically integrated with one another. This facilitates the manufacture of the lighting device. The term ‘optically integrated’ means that the respective optical elements are in close contact with one another. The plurality of optical elements may be optically integrated by bonding them with an adhesive or by integrally forming them.
One preferable structure enables one of the light source lamps included in the plurality of lamp units to be selectively turned on. This structure enables the brightness of light to be adjusted in multiple steps if required, thereby attaining the required brightness and efficient power consumption.
In accordance with another preferable structure, the light source lamps included in the plurality of lamp units emit respective light of different wavelength distribution characteristics. This structure enables the tint of light for illumination to be set to a predetermined value, thereby improving the color reproducibility of a color projector-type display apparatus.
The lighting device preferably has an integrator optical system, in order to reduce the unevenness of illuminance of light output from the lighting device. Namely the lighting device further includes an integrator optical system having a first lens plate including a plurality of lenses and a second lens plate including a plurality of lenses, wherein the first lens plate spatially divides the light emitted from the light source lamp by the plurality of lenses included therein to produce a plurality of intermediate light fluxes, which are focused as secondary light source images in the vicinity of entrance planes of the plurality of lenses included in the second lens plate, output via the plurality of lenses included in the second lens plate, and superposed on a predetermined illumination area. Even when there is a significant variation of the intensity of light within a cross section of the light flux emitted from the lamp unit, the above structure enables the output light to be uniform in brightness and even in color.
In one preferable application of this structure, the lighting device further includes polarizing means for converting light fluxes output from the second lens plate to light fluxes of a single polarization type having identical polarizing directions and outputting the light fluxes of the single polarization type. The polarizing means has polarizat
Hashizume Toshiaki
Itoh Yoshitaka
Dowling William
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Seiko Epson Corporation
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