Optics: image projectors – Composite projected image
Reexamination Certificate
2001-11-02
2003-10-28
Adams, Russell (Department: 2851)
Optics: image projectors
Composite projected image
C353S031000, C353S029000, C353S094000, C353S122000, C348S744000, C348S745000, C348S759000, C348S798000
Reexamination Certificate
active
06637887
ABSTRACT:
This application claims benefit of Japanese Application No. 2000-339477 filed in Japan on Nov. 7, 2000, the contents of which are incorporated by this reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-display device, or more particularly, to a multi-display device that combines partial images projected from a plurality of projectors so as to construct one image.
2. Description of the Related Art
In the past, various proposals have been made concerning a multi-display device that combines partial images projected from a plurality of projectors so as to construct one image.
As for such a multi-display device, for example, Japanese Patent Unexamined Publication No. 9-211386 has disclosed a projection system that projects a synthetic image by overlapping a first image and a second image in a superposed-portion area on a screen. The projector system has a first light bulb projector and a second light bulb projector. Each projector includes a light source, a light bulb, a condenser, and a projection lens. The light bulb reflects or transmits image light. The condenser directs light emanating from the light source to the light bulb. The projection system further includes a uniting means that is located on a light path linking the light bulb and the projection lens, the light source and the condenser, or the photography lens and the screen. The uniting means smoothes a difference between light levels attained in the superposed-portion area when the light bulb is on and when it is off without lowering a contrast ratio offered by the first or the second light bulb projector. Thus, a seam in an image can be nullified but the contrast ratio will not be lowered.
Moreover, Japanese Patent Unexamined Publication No. 3-53288 describes a multi-video projector composed of a plurality of video projectors each of which includes at least an image projection unit and a screen. The multi-video projector has a partition panel interposed between the image projection unit and the screen. The partition panel has the ability to intercept the whole or part of the image projection light, which is not included in prisms defined by an effective image field on the screen and an intersection between an exit pupil of the projection lens and the ray axis of the emitted light.
Moreover, Japanese Patent Unexamined Publication No. 3-53288 describes a multi-video projector composed of a plurality of video projectors each of which includes at least an image projection unit and a screen. The multi-video projector has a partition panel interposed between the image projection unit and the screen. The partition panel has the ability to intercept the whole or part of the image projection light, which is not included in prisms defined by an effective image field on the screen and an intersection between an exit pupil of the projection lens and the ray axis of the emitted light.
Furthermore, Japanese Patent Unexamined Publication No. 6-169444 describes a video multi-image projection system that simultaneously projects a plurality of images on a screen. When adjoining images are projected to overlap each other, the superposed portion of the overlapping images is transmitted through either of a half mirror, a translucent white member, or a translucent black member. The transmittance rate of the overlapping images ranges from 35% to 45%.
Patent Cooperation Treaty Publication No. WO95/25292 describes an image projecting apparatus in which each projector has a lamp, a condensing optical system, a liquid crystal display panel, a projecting optical system, and one or more comb-like members having substantially triangular teeth. The condensing optical system condenses and radiates the light emanating from the lamp. The liquid crystal display panel receives light radiated from the lamp through the converging optical system and displays an image. The projecting optical system projects an optical image displayed on the liquid crystal display panel. The image projecting apparatus is positioned so that the teeth of the mask member will intercept the marginal part of the light propagated from the liquid crystal display panel to the projecting optical system. Owing to the teeth of the mask member, a light level attenuates towards the margin of the superposed portion of projected overlapping images. Thus, partial images are synthesized smoothly. According to the disclosed technology, the comb-like mask member is intended to control a light attenuation curve, which indicates a change in light level due to attenuation occurring in the superposed portion of partial images.
A known technology for improving the homogeneity of a projected screen images that is implemented in a light source included in a multi-display device having a plurality of projectors like the ones mentioned above will be described with reference to
FIG. 3A
to FIG.
3
F.
A dot-like light source shown in
FIG. 3D
is adopted as a light source to be included in a projector. An illumination device
11
having such a dot-like light source may be used to illuminate a display device
16
. In this case, the display device is, as shown in
FIG. 3E
, illuminated with a dot-like light source image alone. At this time, as shown in
FIG. 3F
, the luminance in the center of a radiated surface tends to get higher than the one in the surrounding portion thereof.
As far as a multi-display device including a plurality of projectors is concerned, partial images projected by the projectors are joined in order to construct one image. It is therefore especially important that the luminance in each partial image is uniform.
As shown in
FIG. 3A
, light emanating from the illumination device
11
is passed through a first lattice-like (dot-matrix-like) lens array
12
and a second lattice-like (dot-matrix-like) lens array
13
. Thus, a plurality of secondary light source images arrayed on a planar basis (or more particularly, in the form of a lattice-like matrix) is produced as shown in FIG.
3
B.
Consequently, as shown in
FIG. 3C
, the display screen of the display device
16
is illuminated nearly uniformly so that uniform brightness will be observed all over the display screen.
On the other hand, in the aforesaid multi-display device having a plurality of projectors, partial images are projected so that adjoining partial images will overlap to have their margins superposed on each other. A sheet interceptor is used therefore to intercept luminous flux that is projected at an area of superposed portion on the screen and that represents partial images. This is intended to prevent the luminance in superposed portion of adjoining images from getting higher. Consequently, when a portion of the partial image is superposed on a portion of an adjoining partial image, the superposed portion exhibits the same luminance as the other portions of the partial images that are not superposed on each other.
In the foregoing configuration, when a plurality of light sources like the aforesaid one (or a plurality of secondary light source images) are used to illuminate a display device, one sheet interceptor provides a plurality of shadows. Consequently, a stepwise distribution of luminance values occurs in the margin of a partial image projected on the screen by each projector.
FIG. 28
shows a stepwise distribution of luminance values on the screen which occurs when a sheet interceptor is used to intercept light radiated as a plurality of secondary light source images.
As shown in
FIG. 28
, when light radiated as a plurality of secondary light source images
18
a
is partly intercepted by a sheet interceptor
95
, a border between an intercepted area on the screen
3
and a non-intercepted area thereon varies depending on the position of each secondary light image
18
a
. This results in a belt-shaped distribution of luminance values
96
that is a stepwise difference in luminance.
Furthermore, when a double-plate projector that divides the path of illumination light into portions associated with colors and that illuminates display devices associated
Adams Russell
Koval Melissa J
Olympus Optical
Ostrolenk Faber Gerb & Soffen, LLP
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