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Browse Prior Art Database

EXPOSURE LAMP CONTROL

IP.com Disclosure Number: IPCOM000024817D
Original Publication Date: 1982-Apr-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 64K

Publishing Venue

Xerox Disclosure Journal

Abstract

This disclosure relates to a document imaging system and describes a method of controlling exposure variations caused by operating temperature variations of the document illuminating light source. A typical light source in a document copier such as a fluorescent lamp, has a light output that varies as a function of operating temperature. For example, over a temperature span of 80°F to 120°F, the light output within a single run can vary as much as +/- 20%, respectively.

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XEROX DISCLOSURE JOURNAL

EXPOSURE LAMP CONTROL Proposed Alvin Eng Classification

U.S. C1. 355/8 Int. C1. G03g 15/28

This disclosure relates to a document imaging system and describes a method of controlling exposure variations caused by operating temperature variations of the document illuminating light source. A typical light source in a document copier such as a fluorescent lamp, has a light output that varies as a function of operating temperature. For example, over a temperature span of 80°F to 120°F, the light output within a single run can vary as much as +/- 20%, respectively.

The figure illustrates a portion of an illumination system wherein a document lying on a glass platen 10 is to be illuminated by fluorescent lamp 12. Light from the lamp is directed through aperture 14 onto the underside of the platen. One end of thermostatic metallic strip 16 is attached to the lamp with the other end mounted to a point in the light housing. Because of the heat expansion characteristics of a thermostatic metal, strip 16 will expand and contract in a fixed relation to the increase and decrease in lamp temperature. By matching the coefficient of expansion of strip 16 and careful positioning of the strip above the central axis of lamp 12, the lamp will be caused to rotate counterclockwise with increasing lamp temperature (as strip 16 expands) and clockwise (with strip 16 contraction). Light from aperture 14 is thus varied to reduce or increase the light incident at the...