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Browse Prior Art Database

SINGLE CROSSOVER DETECTOR

IP.com Disclosure Number: IPCOM000024800D
Original Publication Date: 1982-Apr-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 71K

Publishing Venue

Xerox Disclosure Journal

Abstract

Current raster scanners use two separate crossover detector circuits for sensing the start and end of a scan line. Two separate pulses are produced, a start-of-scan (SOS) and an end-of-scan (EOS), one from each detector circuit, and are used to time the transfer of a scan line of data to the laser modulator.

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EROX DISCLOSURE JOURNAL

SINGLE CROSSOVER DETECTOR Ron Freeman

Proposed Classification
U.S. C1. 250/578 Int. C1. HOlj 40/14

R& C FOR THE ONE-SHOT SHOULO BE PICKED TO PROVIDE A PULSE THAT IS z TWO Em-SOS PERIOOS IN LENGTH

DETECTOR Q SOS

0 EOS

P

MOTOR DRIVEN

\ Y.

MIRROR "A"

DETECTOR OUTPUT

' POLYGON MIRROR

EOS SOS EOS SOS

n n ;; n n

I I\ RESTARTS

HERE +-J---L

I&

PHASING ONE- SHOT AND GATE OUTPUT (SOS) AND GATE OUTPUT (EOS)

n :: n

FIG 2

Volume 7 Number 2 March/April 1982 65

LINE SYNC

\L

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

Page 2 of 2

SINGLE CROSSOVER DETECTOR (Cont'd)

Current raster scanners use two separate crossover detector circuits for sensing the start and end of a scan line. Two separate pulses are produced, a start-of-scan (SOS) and an end-of-scan (EOS), one from each detector circuit, and are used to time the transfer of a scan line of data to the laser modulator.

These detector circuits are relatively expensive to have to use in duplicate so a method has been devised which uses two mirrors in such a manner that the laser beam is made to sweep across a single detector circuit twice for each scan line.

The two pulses generated by the crossover detector are then separated by a simple digital logic one-shot and gates to produce the needed timing signals. The attached sketch shows the physical configuration and the electrical signals produced utilizing this technique.

As the motor driven polygon facets rotate, the laser beam is swept across mi...