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A METHOD FOR PROVIDING FACET TRACKING IN HIGH RESOLUTION LASER DIODE PRINTERS

IP.com Disclosure Number: IPCOM000025617D
Original Publication Date: 1986-Oct-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 4 page(s) / 138K

Publishing Venue

Xerox Disclosure Journal

Abstract

The next generation of laser printers will have much increased resolution for higher print quality and for pictorial imaging Laser diodes, which are currently being used in low end printers because of very low cost and high reliability, are now available at high power (typically 10 to 20 mw) at very little additional cost Thus, it can be expected that in the future, laser diodes will show substantial cost advantage over helium-neon (HeNe) laser systems in the high resoIution, high speed end of the business as infra-red photoreceptors become more widely used

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XEROX DISCLOSURE JOURNAL

A METHOD FOR PROVIDING FACET TRACKING IN HIGH RESOLUTION LASER DIODE PRINTERS
Joseph J. Daniele
Kwok-leung Yip

Proposed Classification

US. C1.346M6L
Int. C1. Gold 15/10

/6

GENERATOR

START OF

Volume 11 Number 5 SeptembedOctober 1986 223

l7

[This page contains 1 picture or other non-text object]

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A METHOD FOR PROVIDING FACET TRACKING IN HIGH RESOLUTION LASER DIODE PRINTERS (Cont'd)

The next generation of laser printers will have much increased resolution for higher print quality and for pictorial imaging Laser diodes, which are currently being used in low end printers because of very low cost and high reliability, are now available at high power (typically 10 to 20 mw) at very little additional cost Thus, it can be expected that in the future, laser diodes will show substantial cost advantage over helium-neon (HeNe) laser systems in the high resoIution, high speed end of the business as infra-red photoreceptors become more widely used

In a high resolution printer, a primary parameter of interest is the size of the optical beam on the polygon (or holographic) facet and thus the size of the facet needed to attain the desired high resolution at the photoreceptor Virtually all high resolution systems use a technique called facet tracking to keep the optical beam centered on the facet as it moves so that the facet does not truncate the beam and cause spot growth, and loss of intensity and contrast in the aerial image. To achieve facet tracking, the angle of approach to the polygon is shifted slightly as the facet moves so that the beam tracks the facet This angular shifting of the beam is done in the acousto-optic modulator used with HeNe systems and is carried out by chirping the r f modulation signal

In a laser diode system however, the diode laser is modulated directly and so no separate modulator is needed However, for high resolution systems, facet tracking is needed to keep the polygon facet to a reasonable size

Referring to the drawing Figure, there is shown a diode laser scanning system 5 in which an image beam 6 is output by a laser diode 7 in response to a video image signal input Image beam 6 is impinged on an acousto-optic modulator 8 which serves, when actuated, to fac...