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Browse Prior Art Database

COLOR DETECTOR

IP.com Disclosure Number: IPCOM000026872D
Original Publication Date: 1994-Feb-28
Included in the Prior Art Database: 2004-Apr-06
Document File: 4 page(s) / 182K

Publishing Venue

Xerox Disclosure Journal

Abstract

The following disclosure proposes the use of two different colored LED light sources to alternately illuminate original or copy sheets within a reprographic system, and using appropriate electronic circuitry, to automatically identify the approximate color of the paper. Such an approximation may be used to adjust the scanning of such documents, or to alert operators of the presence of colored stock in a paper tray.

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XEROX DISCLOSURE JOURNAL

COLOR DETECTOR Classification Proposed Murray 0. Meetze

U.S. C1.358/75 Int. C1. H04N 9/07

Voltrr

XEROX DISCLOSURE JOURNAL - Vol. 19, No. 1 Januarymebruary 1994 67

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COLOR DETE CTOR(Cont'd)

The following disclosure proposes the use of two different colored LED light sources to alternately illuminate original or copy sheets within a reprographic system, and using appropriate electronic circuitry, to automatically identify the approximate color of the paper. Such an approximation may be used to adjust the scanning of such documents, or to alert operators of the presence of colored stock in a paper tray.

Edwin Land described in a Scientific American article in May of 1959 a two- color theory which defined human color vision to include perceptual processing of information about a background in order to interpret a two-sensor information for a single spot of color in the visual field. The color separation process normally used in color imaging will work as well, if color filters are used on the light source rather than on the camera or detector. A photodetector is exposed to the light from a source which is reflected from a pigment, then the output of the detector will be a combined mathematical function of some wavelength-dependent parameters which are characteristic of these elements. For example, the relevant parameters include the spectral sensitivity of the detector, the spectral reflectivity of the pigment, and the spectral characteristics of the light source. Now, if that same photodetector receives light reflected from the same pigment, but from a different source, the output will relate to the previous output in a way which is unique to the particular pigment. This knowledge predicts that light reflected from a pigment under the illumination of a controlled but varying source of light might be used to identify the pigment itself.

Applying this theory, an object of this disclosure is to improve the operability of copiers or similar reprographic systems by eliminating the requirement for operators to program said copiers with information about the color of originals and/or the color of copy paper. More specifically, the apparatus provides electrical output by illuminating the papers with two alternating sources of light, where the sources differ from each other in relative spectral characteristics. Yet another object of the apparatus disclosed herein is to provide an electrical output by receiving the light reflected from a sheet of paper by means of a single detector.

One preferred embodiment of the invention is generally represented in the figure. There a dual LED 12 provides light of two spectral characters, for example, red and green, alternately to an optical fiber 14 which conducts the light to a segment of the paper sheet 18 whose color is to be evaluated. A second optical fiber 16 conducts the reflected light from the surface of pap...