Browse Prior Art Database

SUCCESSIVE MATRIX FOR COLOR ENHANCEMENT

IP.com Disclosure Number: IPCOM000027825D
Original Publication Date: 2000-Feb-29
Included in the Prior Art Database: 2004-Apr-09
Document File: 8 page(s) / 300K

Publishing Venue

Xerox Disclosure Journal

Abstract

A new method by which color enhancement can be achieved in an electrophotographic copier or printer is disclosed. A successive matrix application enables superior color fidelity and simplified implementation. The method consists of successive application of corrective matrices to scanner Red-Green-Blue (RGB) data that compensates for variations in scan parameters from nominal. The method may be used in response to user selections on a user interface panel.

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XEROX DISCLOSURE JOURNAL

         -b SCANNER RGB MATRIX

SUCCESSIVE MATRIX FOR COLOR ENHANCEMENT
Debra S. Vent (former employee) Joseph P. Taillie

Proposed Classification
U. S. C1.399/039 Int. C1. G03g 15/01

14

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FIG. 7

-b SELECTION 1 f* SELECTION2 ;[

FIG. 2

Xerox Disclosure Journal - Vol. 25, No. 1 JanuaryFebruary 2000 3

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SUCCESSIVE MATRIX FOR COLOR ENHANCEMENT (Cont'd)

A new method by which color enhancement can be achieved in an electrophotographic copier or printer is disclosed. A successive matrix application enables superior color fidelity and simplified implementation. The method consists of successive application of corrective matrices to scanner Red-Green-Blue (RGB) data that compensates for variations in scan parameters from nominal. The method may be used in response to user selections on a user interface panel.

In a color scanner documents are illuminated, imaged, and sensed, yielding "scanner RGB" values. The spectral characteristic of system components is chosen, in part, to yield optimum colorimetric performance from the scanner. The scanner RGB data is processed to obtain approximations of XYZ values for common format input to other devices such as printers or Cathode Ray Tube (CRT) displays.

Current methods from transformation of scanner RGB to approximate XYZ values are calibration, look up tables, and matrices. The disclosed method is an extension of the latter method.

Currently, a "best fit" 3x3 or larger matrix is used to convert the scanner RGB values to XYZ values, that is to say:

The conversion to a standard color space enables input to CRT displays or output devices, but also permits easy evaluation of the scanner performance by comparison of the scanner XYZ values to the measured document XYZ values, or by similar comparison in L*a*b* color space.

The least robust matrix method consists of embedding a single compromise matrix in a machine. This matrix is applied to the RGB data to convert to XYZ, regardless of the scan parameters (document type, user selections, exact scanner component characteristic, etc.). With this method, the best performance will not be obtained with the nominal set of scan parameters, nor will the worst performance be obtained with any alternate set of scan parameters. This is the simplest method, but offers no enhanced machine performance.

4 Xerox Disclosure Journal - Vol. 25, No. 1 JanuaryBebruary 2000

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SUCCESSIVE MATFUX FOR COLOR ENHANCEMENT (Cont'd)

Table 1 illustrates the performance for two systems using a single matrix. The systems differ only in their platens; the first having an uncoated platen glass, the second a coated platen hence different platen spectral characteristics. The matrix applied in both cases is a matrix derived as "best fit" for the system.

Table 1

I

Uncoated platedmatrix derived for this system

Coated platedmatrix derived for un...