Browse Prior Art Database

COLOR SEPARATION WITH ELECTRONICALLY CHARGED FILTERS

IP.com Disclosure Number: IPCOM000027577D
Original Publication Date: 1997-Dec-31
Included in the Prior Art Database: 2004-Apr-08
Document File: 2 page(s) / 65K

Publishing Venue

Xerox Disclosure Journal

Abstract

A liquid crystal cell is used as an electronically programmable filter for rapid color separation in an electrophotographic printing machine. The liquid crystal filter may be located at several places in the optical path. For example: on the platen cover (for transparent documents), at the platen, in the iJlumination system, on one of several mirrors, in front of a lens, or even as one of the lens elements. The color of the filter may be controlled on a line-by-line, scan-by-scan, or even on a pixel-by-pixel basis depending on the filter speed capabilities and system requirements. Since the filter is changeable while light collects at a sensor, the filter spectral response may be integrated to simulate a custom fiter. Cost considerations detennine size and placement of the filter. Since the number of filters used is not limited by mechanical space or image sensor cost, more than the three traditional fdters may be used to obtain an extended color gamut, and thus reduce troublesome metamerism.

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XEROX DISCLOSURE JOURNAL

COLOR SEPARATION WITH Proposed Classification ELECTRONICALLY CHARGED FILTERS
Richard H. Tuhro
Wayne A. Buchar

U. S. C1.399/004 Int. C1. G03g 15/01

A liquid crystal cell is used as an electronically programmable filter for rapid color separation in an electrophotographic printing machine. The liquid crystal filter may be located at several places in the optical path. For example: on the platen cover (for transparent documents), at the platen, in the iJlumination system, on one of several mirrors, in front of a lens, or even as one of the lens elements. The color of the filter may be controlled on a line-by-line, scan-by-scan, or even on a pixel-by-pixel basis depending on the filter speed capabilities and system requirements. Since the filter is changeable while light collects at a sensor, the filter spectral response may be integrated to simulate a custom fiter. Cost considerations detennine size and placement of the filter. Since the number of filters used is not limited by mechanical space or image sensor cost, more than the three traditional fdters may be used to obtain an extended color gamut, and thus reduce troublesome metamerism.

REFERENCE

Armitage, D. "Liquid Crystal Voltage Controlled . Retardation Display." APPLIED OPTICS 19 (July 1980): 2235-2239.

U.S. Patent No. 4,582,396 issued April 15, 1986 to Boa et aL discloses a field sequential color display using optical retardation. A liquid crystal cell that operates between two stat...