Computer graphics processing and selective visual display system – Display peripheral interface input device
Reexamination Certificate
2000-06-23
2001-07-10
Chang, Kent (Department: 2673)
Computer graphics processing and selective visual display system
Display peripheral interface input device
C353S031000, C353S034000
Reexamination Certificate
active
06259430
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a color display and to a method for displaying color. In particular, this invention relates to device for the production and communication of color in which improved color specification is achieved by providing independent control of the radiation intensity within at least four bands across the visible spectrum.
BACKGROUND OF THE INVENTION
A wide gamut of colors can be generated and displayed by intermixing red, green, and blue primary light sources in different ratios. In general, a color that matches any particular color sample can be produced on a display using the three primary colors.
However, the ratios of the red, green, and blue primaries that produce a color that matches any particular sample depend on the ambient light used to illuminate the color sample. Moreover, when only the three primary colors are used, it is possible to produce a color that some people see as a match to a sample, but that other people see as a mismatch. Colors that look alike in some ambient illuminations look different in other illuminations, and colors that look alike to some people look different to others. These phenomena are referred to as “metamerism”.
Appearance of the color under given illumination depends on both the reflectance spectrum and the illuminance spectrum. Consequently, reproduction of the appearance of a color sample requires knowledge of both the complete reflectance spectrum and the complete illuminance spectrum. When these are known, the color can be reproduced by generating the spectrum that is the convolution of these two.
Perfect reproduction of a color requires control over the intensity level of each wavelength of the visible spectrum. In practice, the spectrum can be divided into a plurality of bands, and the average intensity within each band can be specified. Using four or five such bands results in significantly reduced metamerism, compared with the commonly used three primary colors. Using seven bands reduces the metameric effects by an order of magnitude. Therefore, a need exists for a system for specifying, measuring, displaying, and communicating colors with reduced metameric confusion.
SUMMARY OF THE INVENTION
The invention is a method for displaying color. The displayed color has reduced metameric confusion as compared to colors obtained by mixing radiation from the three primary colors. The improved color specification is achieved by providing independent control of the intensity of radiation within at least four bands across the spectrum. In general, the metameric improvement is greater with a larger number of bands. Preferably, at least seven bands of radiation are used. The method comprises the steps of:
a) providing a radiation spectrum of the color;
b) dividing the radiation spectrum into at least four wavelength bands;
c) selecting a wavelength in each of the wavelength bands;
d) determining an intensity for each selected wavelength;
e) transmitting the intensities to a radiation source;
f) generating a multiplicity of beams of radiation, each beam of radiation essentially corresponding in wavelength and intensity to the wavelength and intensity of one of the selected wavelengths; and
g) combining the beams of radiation and displaying the color.
In another embodiment, the invention is a color display. The color display comprises:
a radiation source capable of producing at least four beams of radiation, each beam having a respectively different wavelength;
means for controlling the intensity of each of the beams of radiation; and
a display device.
In a preferred embodiment, the color display also comprises a feedback control means that samples the intensity and/or wavelength of each of the beams of radiation and provides feedback control of the displayed color.
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International Search Report for PCT/US00/17438, filed Jun. 26, 2000. “Liquid Crystal Display Three Panel Projector Using Three Primary Colors Light Emitting Diode Light Sources” IBM Technical Disclosure Bulletin, US, IBM Corp. New York, vol. 40, No. 4, Apr. 1, 1997, pp. 201-205, XP000728313 ISSN.: 0018-8689, the whole document.
Burstyn Herschel Clement
Riddle George Herbert Needham
Burke William J.
Chang Kent
Sarnoff Corporation
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