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CONTROL OF ROS OUTPUT POWER BY ROTATION OF LASER PLANE OF POLARIZATION

IP.com Disclosure Number: IPCOM000025321D
Original Publication Date: 1984-Aug-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 65K

Publishing Venue

Xerox Disclosure Journal

Abstract

In most Raster Output Scanner (ROS) designs, it is necessary to match the oDtical power of the writing beam to that required by the photoreceptor. This requires some type of optical power control since it is necessary to account for variations in laser output power and scanner to scanner variations in throwhput or transmit-tance of the optical system. In past systems, this control has been accomolished by placing either fixed or variable neutral density filters in the optical beam path or by an adjustment of the beam modulator drive power.

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XEROX DISCLOSURE JOURNAL

CONTROL OF ROS OUTPUT POWER BY ROTATION OF LASER PLANE OF POLARIZATION
Warren F. Brandkamp

Proposed Classification
U.S. C.1. 358/285 Int. Cl. FrO4n 1/04

In most Raster Output Scanner (ROS) designs, it is necessary to match the oDtical power of the writing beam to that required by the photoreceptor. This requires some type of optical power control since it is necessary to account for variations in laser output power and scanner to scanner variations in throwhput or transmit- tance of the optical system. In past systems, this control has been accomolished by
placing either fixed or variable neutral density filters in the optical beam path or by an adjustment of the beam modulator drive power.

It is proposed here, in cases where a polarized laser is used in conjunction with a strongly polarization sensitive optical element (such as a gallium phosphicfe modulator), that power be controlled by rotation of the plane of polarization of the laser. The rotation of the laser's plane of polarization is achieved by rotatiny the entire laser assembly until the desired ROS output power is obtained. This rotation is easily accomplished since the laser is usually mounted in a cylindrical container or Laser Tube Assembly on the exterior of the sealed ROS. For example, based upon the measured sensitivity of gallium phosphide to the polarization of the incident light, the optical irradiance can be continuously controlled over a power range of approximately...