Browse Prior Art Database

SELF FOCUSING ROS

IP.com Disclosure Number: IPCOM000026685D
Original Publication Date: 1993-Apr-30
Included in the Prior Art Database: 2004-Apr-06
Document File: 2 page(s) / 91K

Publishing Venue

Xerox Disclosure Journal

Abstract

When exposing a photoreceptor using a laser Raster Output Scanner (ROS), the spot size is usually of the order of several thousandths of an inch. The consequential large depth of focus means that relatively crude means can be applied to focus the beam onto the photoreceptor. However, in the case of high resolution imaging, as on microfilm, where the spot size may be as small as one micron, the depth of focus could be below that possible with normal mechanical tolerancing. One method to alleviate this problem is to use a technique developed for optical disk, a technique employing dynamic focusing. As practiced, this technique cannot be applied to flying spot scanners, but disclosed herein is an extension that can be used.

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XEROX DISCLOSURE JOURNAL

SELF FOCUSING ROS

Proposed Thomas Robson Classification

US. C1.355/210 Int. C1. G03g 15/00

XEROX DISCLOSURE JOURNAL - Vol. 18, No. 2 MarcldAprill993 151

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SELF FOCUSING ROS(Cont'd)

When exposing a photoreceptor using a laser Raster Output Scanner (ROS),

the spot size is usually of the order of several thousandths of an inch. The consequential large depth of focus means that relatively crude means can be applied to focus the beam onto the photoreceptor. However, in the case of high resolution imaging, as on microfilm, where the spot size may be as small as one micron, the depth of focus could be below that possible with normal mechanical tolerancing. One method to alleviate this problem is to use a technique developed for optical disk, a technique employing dynamic focusing. As practiced, this technique cannot be applied to flying spot scanners, but disclosed herein is an extension that can be used.

As illustrated in the Figure, light from the laser 20 passes through a beam splitter 22 undeviated and on through to a beam expander 30 comprising elements 26 and 28. The first element 26 of the beam expander 30 is movable by a motor 24. The beam then is reflected off a scanning mirror 32 which may be a polygon facet or a mirror mounted on a galvanometer. The beam is focused by the telecentric flat field lens 34, which may also be f theta type, on to recording medium 36. Some of...