Optics: measuring and testing – By shade or color – Trichromatic examination
Reexamination Certificate
2001-06-25
2003-05-20
Lee, Michael G. (Department: 2876)
Optics: measuring and testing
By shade or color
Trichromatic examination
C356S402000, C356S404000, C356S319000
Reexamination Certificate
active
06567170
ABSTRACT:
Disclosed in the embodiments herein is an improved, low cost, plural color spectrophotometer for color detection, calibration and/or correction systems, highly suitable to be used for, or incorporated into, the color calibration or control of various color printing systems or other on-line color control or color processing systems.
In particular, the disclosed exemplary spectrophotometer and color measurement system enables more than one test color to be measured at a time, thus increasing the sampling rate and/or reducing the number color test substrates and/or generations of color test patches.
Also disclosed in the embodiment herein is a low cost broad color spectrum spectrophotometer in which different colors may be measured on one or more of the same, low cost, multiple photo-sites, photodetector chips. Disclosed herein is an example of how such multi-pixel (and plural differently color responsive) chips can be used to read plural color test patches simultaneously.
Furthermore, the disclosed embodiment also teaches how the above and other advantageous features may be combined with other advantageous features of a desirably non-contacting spectrophotometer with greatly reduced spatial and angular insensitivity to allowable movements of the color test target area or surface relative to the non-contacting spectrophotometer, as also and further described in the above cross-referenced applications.
The exemplary disclosed spectrophotometer desirably utilizes (incorporates in part) a pre-assembly component or part (hereinafter “chip”) of a low cost commercially available document imaging array or bar, such as heretofore used for imaging colored documents in various scanners, digital copiers, and multifunction products. As is well known in the art, such commercial document imaging bars have multiple photo-sites, and are plural spectra responsive, typically by having three rows of respective red, green and blue filtered photo-sites.
As also disclosed in the spectrophotometer embodiment herein, it may employ only a small limited number of different spectra LED or other illumination sources, yet provide multiple data outputs suitable for broad spectral data reconstruction from such a low cost photosensor having plural different spectral responsive photo-sites, by detecting light reflected by a plural color test target area sequentially illuminated by those illumination sources, and/or white light illuminated, to rapidly provide broad spectrum data from a plural colors test surface.
By way of background, examples of full color document imaging bars include those used in various document scanning systems of various well known Xerox Corporation commercial products (including some being alternatively used for black and white imaging) such as the Document Center 255DC™ products, or the Document Center Color Series 50™ products. Some examples of patents relating to semiconductor color imager bars or segments thereof and their operation or circuitry include Xerox Corporation U.S. Pat. No. 5,808,297, issued Sep. 15, 1998; U.S. Pat. No. 5,543,838, issued Aug. 6, 1996; U.S. Pat. No. 5,550,653, issued Aug. 27, 1996; U.S. Pat. No. 5,604,362, issued Feb. 18, 1997; and U.S. Pat. No. 5,519,514, issued May 21, 1996. Typically, such color imaging bars come already provided with at least three different color filters, such as red, green and blue, overlying three rows of closely spaced light sensor elements (photo-sites), to provide electrical output signals corresponding to the colors of the document image being scanned. Such imaging bars are typically formed by edge butting together a number of individual imaging chips, each having such multiple tiny and closely spaced photo-sites. Typically, there are three rows of such photo-sites on each such chip, as in the assembled imaging bar, with said integral filters for red, green and blue, respectively.
Because of the high volumes in which such commercial color imaging bars are made for such products, it has been discovered that their manufacturers can provide, at low cost, a commercial source of said single chip components thereof. The fact that each such chip can provide electrical signals from multiple light sensor elements (photo-sites) in at least three rows of different spectral responses which are closely enough spaced together so as to be simultaneously illuminated by a relatively small area of illumination, is effectively utilized in the spectrophotometer of the embodiment herein. (It will be understood that the term “chip” as used herein does not exclude the use of two or more such chips, either integrally abutted or separately positioned.)
However, it is not believed that heretofore such plural sensors chips for plural color sensing, which are normally put together in series for imaging bars for document scanning, have ever been used in spectrophotometers. These chips themselves are not normally even sold or used individually. The disclosed embodiment illustrates how that may be done, to provide a compact and lower cost spectrophotometer especially suitable for on-line color control systems for sensing the colors of moving printed sheets or other color materials.
Although not limited thereto, the exemplary spectrophotometer of the embodiment herein is shown and described herein in desirable combination as an integral part of an automatic on-line continuous color table correction system of a color printer, in which this low cost spectrophotometer may be affordably provided in the output path of each color printer for automatic measurement of printed color test patches of printer output, without any manual effort or intervention being required. Such color control systems are further described in the above and below cited co-pending applications and patents. For example, in Xerox Corp. U.S. Pat. No. 6,178,007 B1, issued Jan. 23, 2001, based on U.S. application Ser. No. 08/786,010, filed Jan. 21, 1997 by Steven J. Harrington, Attorney Docket No. D/96644, entitled “Method For Continuous Incremental Color Calibration For Color Document Output Terminals.” The European patent application equivalent thereof was published by the European Patent Office on Jul. 22, 1998 as EPO Publication No. 0 854 638 A2. Also, Xerox Corp. U.S. Pat. No. 6,222,648, issued Apr. 24, 2001, based on U.S. application Ser. No. 08/787,524, also filed Jan. 21, 1997, by Barry Wolf, et al, entitled “On Line Compensation for Slow Drift of Color Fidelity in Document Output Terminals (DOT)”, Attorney Docket No. D/96459. Also noted in this regard are Xerox Corp. U.S. Pat. No. 6,157,469, issued Dec. 5, 2000 and filed May 22, 1998 by Lingappa K. Mestha; Apple Computer, Inc. U.S. Pat. No. 5,881,209, issued 1999; U.S. Pat. No. 5,612,902 issued Mar. 18, 1997 to Michael Stokes, and other patents and applications further noted below.
A low cost, relatively simple, spectrophotometer, as disclosed herein, is thus particularly (but not exclusively) highly desirable for such a “colorimetry” function for such an on-line printer color correction system. Where at least one dedicated spectrophotometer is provided in each printer, its cost and other factors becomes much more significant, as compared to the high cost (and other unsuitability's for on-line use) of typical laboratory spectrophotometers.
An early patent of interest as to using a calorimeter in the printed sheets output of a color printer is Xerox Corp. U.S. Pat. No. 5,748,221, issued May 5, 1998 to Vittorio Castelli, et al, filed Nov. 1, 1995 (D/95398). This patent is also of particular interest here for its Col. 6, lines 18 to 28 description of measuring color:
“. . . by imaging a part of an illuminated color patch on three amorphous silicon detector elements after filtering with red, green and blue materials. The technology is akin to that of color input scanners. The detector outputs can be used as densitometric values to assure color consistency. Calibration of the resulting instrument outputs against measurement by laboratory calorimeters taken over a large sample of patches made by the toners of the printer of interest allows
Mestha Lingappa K.
Tandon Jagdish C.
Hess Daniel A.
Lee Michael G.
Xerox Corporation
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