Optical: systems and elements – Stereoscopic
Reexamination Certificate
1999-09-15
2001-01-09
Chang, Audrey (Department: 2872)
Optical: systems and elements
Stereoscopic
C359S464000, C359S466000, C348S051000, C348S054000
Reexamination Certificate
active
06172807
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a stereoscopic image display device which displays an image from a plurality of points of view with a stereoscopic vision, and more particularly to a stereoscopic image display device which converges spatially modulated light of left and right images having binocular parallax on the vicinities of the corresponding left and right eyes of a viewer to make the viewer recognize a stereoscopic image.
Recently, stereoscopic image display devices which use images having binocular parallax to make a viewer recognize them as a stereoscopic image are reported. Among them, attention has been paid to stereoscopic image display systems which do not require special spectacles since viewers can easily enjoy stereoscopic images.
Jpn. Pat. Appln. KOKAI Pub. No. 6-225344 discloses such a stereoscopic image display system which displays images while following the motion of a viewer, without requiring special spectacles. In this system, back-light for left and right sides is emitted through a large-sized convex lens to the position, or thereabouts, of the viewer's face or the viewer's left or right eyes. Therefore, since the position of light sources of back-light change as the viewer moves, a good tracking is achieved.
However, in this conventional art, as the viewer moves leftwards or rightwards from the front position, an angle &phgr; formed between the light axis of incident light passing through the spatial modulation element and the surface of a liquid crystal board used as the spatial modulation element increases, and the amount of an orthogonal-projection component of incident light reduces. Further, in this conventional art, a black-and-white television wherein a phosphor-coated surface is used as a luminous member is used. The luminescent section of this light source can be regarded as a perfect diffusion light source whose luminance is uniform even if it is viewed from any angle. When the luminous intensity in the vertical direction is Io, the luminous intensity in the oblique direction is Io cos &phgr;. Therefore, the luminous intensity has such characteristics that the luminous intensity reduces according to the degree of obliqueness of the direction in which the light source is viewed. Further, the liquid crystal board used as the spatial modulation element has such general characteristics that its transmissivity lowers when the light incident direction shifts from the vertical axis.
As explained above, in the conventional stereoscopic image display device, there were the problems that the image to be viewed becomes dim as the viewer moves leftwards or rightwards from the central position, and that the stereoscopically viewable region is narrow. Further, even when the viewer does not move, a peripheral portion of an image to be viewed is dimmer than a central portion.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to provide a stereoscopic image display device, wherein an image to be viewed does not become dim even when the viewer moves leftwards and rightwards from the front position. The stereoscopically viewable possible region is widened, and a peripheral portion of an image to be viewed is not dimmer than a central portion even when the viewer does not move.
According to the present invention, there is provided a stereoscopic image display device for providing a stereoscopic image by displaying images with a parallax on a viewer's left and right eyes, comprising:
a light source with variable light-emitting regions for emitting light;
an optical element for condensing light emitted from the light source to each of the viewer's left and right eyes;
spatial modulation means, disposed on an optical path from the light source to the viewer, for spatially modulating the light emitted from the light source; and
control means for controlling a luminous intensity of the light source to such a value that a viewing illuminance of the light viewed by the viewer becomes uniform.
By the above means, since the luminous intensity of the light source is controlled to such a value that the viewing illuminance at which the viewer views an image becomes uniform, an image with a uniform brightness can be provided.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5132839 (1992-07-01), Travis
patent: 6-225344 (1994-08-01), None
“Beam Shaping Diffusion” Optical Alliance, Jun., 1998, pp. 5-8.
Chang Audrey
Kabushiki Kaisha Toshiba
Pillsbury Madison & Sutro LLP
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