Television – Modular image display system
Reexamination Certificate
2000-04-24
2003-05-27
Hsia, Sherrie (Department: 2614)
Television
Modular image display system
C348S744000, C348S778000, C348S785000
Reexamination Certificate
active
06570623
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention.
Basically described, the invention comprises an apparatus and method for optically blending adjacent images on a video wall as produced by a multi-projector system.
2. Description of Prior Art.
Video walls made of multiple projectors are becoming increasingly popular because of their large format and high resolution. A typical video wall is composed of a large screen and an array of projectors. The projectors project images in a tiled fashion onto the screen by either front or rear projection to deliver high resolution results. To make the construction of the video walls easier, the projection components are usually made modular, thus the projection components are also referred to as cubes. Traditional video walls have seams because of the difficulty in alignment and color balance.
Edge blending is a technique to minimize seams produced at overlapping images. The known technique is to overlap the edges of projected, tiled images and blend the overlapped pixels to smooth the luminance and chromaticity transition from one projected tiled image to another. The current state-of-the-art technique is to use specially designed hardware to modulate the video signals that correspond to the overlapped region. See, for example, the discussions in U.S. Pat. No. 4,974,073 entitled “Seamless Video Display” and issued on Nov. 27, 1990 or in U.S. Pat. No. 5,136,390 entitled “Adjustable Multiple Image Display Smoothing Method and Apparatus” issued on August 4, 1992. The modulation is automatically calculated or manually adjusted so that the combined intensity and color balance in the overlapped region on the screen are as uniform as possible. Furthermore, the transition of the luminance and chromaticity from a non-overlapped region to its adjacent overlapped regions should be smooth in order to avoid undesirable effects such as Mach banding. See, for example, the discussion in “Contour and Contrast”, by Ratcliff, F., Scientific American, 226 (6), Q1972, 91-101. Although this approach can modulate the image source, it cannot alter the mapping between image source and luminance of the projector outputs. Consequently, the electrical edge blending approach does not work well with projection devices that leak light energy. For example, this approach does not work well with modern projectors such as Liquid Crystal Display (LCD) or Digital Micro-Mirror Device (DMD) projectors, which leak substantial amounts of light energy when the projected pixels are black. The result is that the effective luminance for a supposedly pitch-black image is not black. This is known as the “non-zero black level” problem. Since projected black images are not completely black on the screen, the overlapped regions are brighter than non-overlapped regions. The electrical edge-blending approach cannot reduce the light energy in the overlapped regions because the video signals are already at the lowest level when projected pixels are black.
Another technique for blending images is to use dichroic filters in an optical lens system such as described in U.S. Pat. No. 4,634,384 entitled “Head and/or Eye Tracked Optically Blended Display System” issued Jan. 6, 1987 to Fernando B. Nevis and Jimmy Paige, and assigned to the General Electric Co. Since this approach operates directly on the light emitted from the projector's light source, it is not affected by the “non-zero black level” problem in modern projectors. In order to use this technique for video wall systems, however, the projector manufacturer must place the filters inside the projector's lens system and provide control mechanisms for adjustment. This approach has proved to be relatively expensive and therefore has limited application.
Other prior art patent references of possible relevance include: U.S. Pat. Nos. 3,833,764; 5,822,002; and 4,356,511.
It was in the context of this prior art that the present invention arose.
SUMMARY OF THE INVENTION
Briefly described, the invention comprises the use of a blending frame to control the degree of intensity reduction in the overlapping region of two images projected by two different projectors in a video wall system. In addition, the invention includes an adaptive technique or algorithm to fine tune the blend result and a camera-based iterative algorithm to fine tune the blend result and to reduce or eliminate the defraction effect. These and other features of the invention will be more fully understood by reference to the following drawings.
REFERENCES:
patent: 3833764 (1974-09-01), Taylor
patent: 4356511 (1982-10-01), Tsujimura
patent: 4634384 (1987-01-01), Neves et al.
patent: 4974073 (1990-11-01), Inova
patent: 5136390 (1992-08-01), Inova et al.
patent: 5822002 (1998-10-01), Tokoro et al.
patent: 6377306 (2002-04-01), Johnson et al.
Chen YuQun
Housel Timothy
Li Kai
Hsia Sherrie
Onka, Esq. Thomas J.
Princeton University
Woodbridge & Associates P.C.
Woodbridge Esq. Richard C.
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