Computer graphics processing and selective visual display system – Display peripheral interface input device
Reexamination Certificate
1998-11-23
2001-09-04
Cuchlinski, Jr., William A. (Department: 3661)
Computer graphics processing and selective visual display system
Display peripheral interface input device
C348S223100
Reexamination Certificate
active
06285350
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a color correction for a (CRT) display device with a variable light transmission panel or coating.
2. Description of the Related Art
As described in U.S. Pat. No. 5,060,075, the perceived contrast of an image produced by a CRT display can be improved by using a variable light transmissivity panel adjacent to the CRT faceplate or by applying a variable transmissivity coating on the tube faceplate. The transmission of the panel or coating can be changed as function of the ambient lighting. Generally, the transmissivity of the panel decreases in response to an increasing ambient light intensity. For lower ambient light conditions, this will result in CRT tube with a higher transmissivity, resulting in a lower electron beam current which then result in a sharper picture and a lower energy consumption. Also, the gun characteristics can be changed. Normally the gun is optimised for larger currents. However, when the transmissivity of the panel is high and thus the electron beam current is low, the characteristics of the gun can be changed is such a way that the gun is optimal for lower beam currents. This can be done by changing the grid voltages. The transmissivity of a variable light transmission panel is controlled by applying a voltage to the panel.
As acknowledged in U.S. Pat. No. 5,847,858, corresponding to International Application No. WO-A-97/22906 and International Application No. WO-A-97/34192, corresponding to U.S. Pat. No. 5,859,735, some types of transmission panels are not an ideal neutral (grey) filter, but have a transmission T(&lgr;) which is not constant for the visible wavelength &lgr;. Also, the shape of transmission curve T(&lgr;) changes as a function of the applied voltage. In other words, the color of the panel is not grey, and changes as a function of the perceived transmissivity. If such a panel, for example, an electrochromic panel, is applied, the appearance of the colors produced by the tube-panel combination will change. The used electrochromic sample resulted in a bluish picture, because the transmissivity of red and green decreases faster than the transmissivity of blue, when the perceived transmissivity is decreased. To solve these problems, WO-A-97/22906 and WO-A-97/34192 propose to use adapted electrochromic elements for the transmission panel/coating.
SUMMARY OF THE INVENTION
It is, inter alia, an object of the invention to provide a solution in which it is not necessary to use special coatings. To this end, a first aspect of the invention provides a display apparatus having variable light transmission means in which color deviations are compensated. An advantageous embodiment of the display apparatus includes means for linearizing the applied color signals, matrix means for compensating the color deviations, and gamma correction means for furnishing color signals to control terminals of the display device.
In a display apparatus in accordance with a primary aspect of the invention that comprises a display device, a variable light transmission panel or coating at a front side of the display device, amplifiers for furnishing color signals to control terminals of the display device, and a control unit for controlling the variable light transmission panel or coating and the amplifiers, the amplifiers are controlled in such a manner that a color deviation of the variable light transmission panel or coating is compensated for.
Attention is drawn to the fact that while U.S. Pat. No. 5,060,075 also shows a drive amplifier
13
which is controlled by the panel control circuitry, the purpose of this known amplifier control is limited to improve image contrast by varying the beam current with variations in ambient light. That U.S. Pat. No. 5,060,075 does not relate to color deviations is also apparent from the fact that its CRT has only a single cathode to which the single drive amplifier
13
is connected.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
REFERENCES:
patent: 4386345 (1983-05-01), Narveson et al.
patent: 5060075 (1991-10-01), Skinner
patent: 5847858 (1998-12-01), Krings et al.
patent: 5859735 (1999-01-01), De Vries
patent: WO9534088 (1995-12-01), None
patent: WO9722906 (1997-06-01), None
patent: WO9734192 (1997-09-01), None
Van Nostrand's Scientific Encyclopedia, Eighth Edition, 1995, p. 2660.
Doyle Terence
Ijntema Dominicus J.
Van Den Eeden Adrianus L. G.
Cuchlinski Jr. William A.
Goodman Edward W.
Nguyen Thu
U.S. Philips Corporation
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