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LAMP HAVING BLEACHABLE COATING TO PROVIDE VARIABLE ATTENUATION

IP.com Disclosure Number: IPCOM000027725D
Original Publication Date: 1999-Feb-28
Included in the Prior Art Database: 2004-Apr-09
Document File: 2 page(s) / 86K

Publishing Venue

Xerox Disclosure Journal

Abstract

Disclosed is the addition of a bleachable dye coating to the surface of a fluorescent lamp in order to compensate for normal reduction in light output over lamp life. Aperture fluorescent lamp output is known to decay over time. The principal mechanisms for this decay are discoloration of the reflector coating that forms the aperture, consumption of the mercury that is the excitation mechanism, reduction in phosphor efficiency, and deposits of material evaporated off the electrodes. In document illumination systems, this reduction in output leads to a decrease in exposure, as a significant problem in analog copying machines. In digital copying machines (scanners), there is often a capability of electronically correcting for the decrease in illumination, however, there is a corresponding reduction in the signal-to-noise ratio. In addition, the correction means often has limited dynamic range so it is advantageous to restrict the amount of variation due to the lamp. The proposed addition of a dyed coating on the surface of the lamp will bleach out over time, compensating for the reduction in output.

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XEROX DISCLOSURE JOURNAL

LAMP HAVING BLEACHABLE COATING TO PROVIDE VARIABLE ATTENUATION Joseph P. Taillie
Jack K Fullerton

Proposed Classifcation
U. S. C1. 399/032 Int. CL G03g 15/04

Disclosed is the addition of a bleachable dye coating to the surface of a fluorescent lamp in order to compensate for normal reduction in light output over lamp life.

Aperture fluorescent lamp output is known to decay over time. The principal mechanisms for this decay are discoloration of the reflector coating that forms the aperture, consumption of the mercury that is the excitation mechanism, reduction in phosphor efficiency, and deposits of material evaporated off the electrodes. In document illumination systems, this reduction in output leads to a decrease in exposure, as a significant problem in analog copying machines. In digital copying machines (scanners), there is often a capability of electronically correcting for the decrease in illumination, however, there is a corresponding reduction in the signal-to-noise ratio. In addition, the correction means often has limited dynamic range so it is advantageous to restrict the amount of variation due to the lamp. The proposed addition of a dyed coating on the surface of the lamp will bleach out over time, compensating for the reduction in output.

Many organic color dyes have the characteristic that they fade upon prolonged exposure to radiation. In fact, this is a well-known problem with house paint and fabric auto finishes. Higher energy (i-e-, shorter wavelen...