Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
1998-10-28
2001-07-24
Metjahic, Safet (Department: 2858)
Optics: image projectors
Composite projected image
Multicolor picture
Reexamination Certificate
active
06264331
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to an image projector that projects an enlarged optical image onto a screen, and more particularly, to a construction of its illuminating optical system.
BACKGROUND OF THE INVENTION
An image projector that forms an optical image (projection optical image) by driving light valves, irradiated by illuminating light, based on image signals, and projects an enlargement of this optical image onto a screen, is conventionally known as a means to display a large image.
Japanese Laid-Open Patent Application Sho 62-180343, for example, discloses a reflective image projector having a spectro-optical system comprising a dichroic mirror, a total reflection mirror, and three liquid crystal light valves that form optical images of R, G and B components behind the projection optical system. Illuminating light is led to the liquid crystal light valves from the projection optical system via the spectro-optical system and the reflection of the illuminating light off of the liquid crystal light valves (optical images) is projected onto a screen in front of the projection optical system via the spectro-optical system and the projection optical system. A plate-like total reflection mirror is located at the aperture position of the projection optical system such that the illuminating light from the light source, irradiated from a direction perpendicular to the optical axis of the projection optical system, will be totally reflected by the total reflection mirror so as to (i) pass through half of the effective light pass-through area of the aperture in a direction parallel to the optical axis of the projection optical system and (ii) irradiate the liquid crystal light valves.
Japanese Laid-Open Patent Application Hei 7-159722 discloses a reflective image projector in which a light path splitting surface is located on the path of the illuminating light from the light source, and the light beams, reflected off of the light valves into the illuminating light path and comprising optical images, are split by the light path splitting surface into light beams that run in a direction perpendicular to the illuminating light and are projected onto the screen via reflection. The light beams from the light source are divided into multiple secondary light sources by means of fly eye lenses and these light beams from the secondary light sources irradiate the panel surfaces of the light valves, in a parallel fashion, through a relay lens, such that the illuminance distribution on the panel surfaces is made uniform.
Japanese Laid-Open Patent Application Hei 8-271854 discloses a reflective image projector having (i) an image forming lens, a deflective beam splitter and a dichroic prism located in the path of the illuminating light from the light source; (ii) a liquid crystal light valve located on each of the three exit surfaces of the dichroic prism; and (iii) a projection optical system located on the side of the exit surface of the polarized beam splitter, which is perpendicular to the light path of the illuminating light, wherein a kaleidoscope is located between the light source and the image forming lens.
The image projector disclosed in the Japanese Laid-Open Patent Application Sho 62-180343 converges the illuminating light from the light source to the aperture position of the projection optical system by means of a relay lens and reflects the secondary light source images toward the liquid crystal light valves by means of a total reflection mirror. Consequently, it is difficult to make the illuminance distribution on the liquid crystal light valve panel surfaces sufficiently uniform and to reduce the unevenness in the brightness of the projected image.
The image projector disclosed in Japanese Laid-Open Patent Application Hei 7-159722 splits the light source into multiple secondary light sources using multiple fly eye lenses in order to make the illuminance distribution on the light valve panel surfaces uniform. However, since it has a construction in which the multiple fly eye lenses are placed in a step configuration, the construction of the fly eye lenses is complex and is disadvantageous in terms of cost as well.
The image projector disclosed in the Japanese Laid-Open Patent Application Hei 8-271854 has a construction wherein the light source and the liquid crystal light valves are arranged linearly, and the illuminating light and the projection light are separated by means of a polarized beam splitter located on the path of the illuminating light from the light source. Consequently, the projection optical system increases in size, making it difficult to make the image projector compact.
The present invention was conceived in view of these problems. It provides an image projector having a compact construction, in which the illuminance distribution on the light valve panel surfaces is made uniform and the unevenness in the brightness of the projected image is reduced.
SUMMARY OF THE INVENTION
The present invention is an image projector having light valves that spatially modulate the illuminating light based on image signals and form optical images for projection; a light source means, which generates the illuminating light; a projection optical system, which is located between the light valves and the screen and projects the optical images onto the screen; and a reflecting member which is located at the projection optical system aperture position and reflects the illuminating light from the light source means such that the light strikes the light valves after passing through half of the effective light pass-through area of the aperture. The image projector has an optical integrator, which is located between the light source means and the reflecting member and splits the light beams from the light source means into multiple secondary light sources, in order to form multiple light source images at the projection optical system aperture position.
Using the construction described above, the illuminating light beams from the light source means are split into multiple secondary light sources, by means of an optical integrator, and strike the reflecting member. The light beams from the multiple secondary light sources are reflected by the reflecting member in a direction along the optical axis of the projection optical system and are formed into images at the aperture position of the projection optical system. The light beams from the multiple secondary light sources, which are formed into images at the aperture position, pass through the projection optical system, parallel to its optical axis, strike the light valves, and illuminate its panel surfaces with uniform illuminance. The illuminating light is spatially modulated by the light valves and optical images for projection (projection images) are formed. The light beams comprising the optical images are reflected from the light valves to the projection optical system. They then pass through the area of the aperture through which the illuminating light does not pass and are projected onto the screen in enlargement.
The present invention is also an image projector as described above, wherein the optical integrator comprises a first lens array and a second lens array, and the optical axes of at least some of the lens cells comprising the first lens array are decentered such that they are closer to the center of the array.
Using the construction described above, the illuminating light beams, emitted from the light source means, are split into multiple secondary light sources by means of the first lens array and are formed into images at the position of the second lens array. Since the optical axes of some of the lens cells of the first lens array are decentered toward the center of the array, the multiple secondary light sources formed by the first lens array become distributed such that they converge on the second lens array around its center. The light beams from the multiple secondary light sources, formed by the second lens array, are reflected by the reflecting member in a direction along the optical axis
Sawai Yasumasa
Takimoto Shunta
LeRoux Etienne
Metjahic Safet
Minolta Co. , Ltd.
Sidley Austin Brown & Wood
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