Browse Prior Art Database

FAST SCAN JITTER MEASURING SYSTEM FOR RASTER SCANNERS

IP.com Disclosure Number: IPCOM000025528D
Original Publication Date: 1985-Dec-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 6 page(s) / 178K

Publishing Venue

Xerox Disclosure Journal

Abstract

Pixel registration errors in raster output scanners or ROS's as they are sometimes called, require detection and quantification during manufacturing of the scanner and later when the scanner is in service. Such errors when in the fast scan direction are usually indicative of an underlying fault or marginal failure in the scanner with the result that copy quality degrades. The usual scanner failures which are evidenced by fast scan jitter are velocity variations in the scanner scanning element, scratched or dirty optical elements, misalignment of optical components, scan detection failures, and pixel clock circuit failures. If fast scan jitter could be readily detected and quantified, such scanner failures could be more readily detected, identified, and corrected; both while the scanner is being manufactured and later in the field when the scanner is in service.

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Page 1 of 6

XEROX DISCLOSURE JOURNAL

DlFFE R ENTl AL 1NTEGRAR)R

FAST SCAN JITTER MEASURING SYSTEM FOR RASTER SCANNERS James C. Traino
Douglas L. Keene

Proposed Classification
U.S. Cl. 358/285 Int. CI. H04n 1/04

FIG I

f2

/~- sos

                                       5 PIXEL EOS c CLOCK RASTER Cl RCU I T OUTPUT
SCANNER TEST PIXELS DATA

CLOCK 0

E PAsSlV - - PEAK TO PEAK

FILTER DETECTOR

 SYNC 9

Volume 10 Number 6 November/December 1985 357

I 1.

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12 I 1 f f4

VOLTMETER '5n

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

Page 2 of 6

FAST SCAN JITTER MEASURING SYSTEM FOR RASTER SCANNERS (Cont' d)

358

FIG 2

SCANNING DIRECTION

     XEROX DISCLOSURE JOURNAL Volume 10 Number 6 November/December 1985

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

Page 3 of 6

FAST SCAN JITTER MEASURING SYSTEM FOR RASTER SCANNERS (Cont'd)

CURRENT -

1

CURRENT 17

CURRENT I8

A I

TIME

TIME

f/6 30

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CURRENT 10 /I7

4

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     XEROX DISCLOSURE JOURNAL Volume 10 Number 6 November/December 1985 359

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

Page 4 of 6

FAST SCAN JITTER MEASURING SYSTEM FOR RASTER SCANNERS (Cont'd)

t TIME

NG 4c

XEROX 360 DISCLOSURE JOURNAL

Volume 10 Number 6 November/December 1985

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

Page 5 of 6

FAST SCAN JITTER MEASURING SYSTEM FOR RASTER SCANNERS (Cont'd)

Pixel registration errors in raster output scanners or ROS's as they are sometimes called, require detection and quantification during manufacturing of the scanner and later when the scanner is in service. Such errors when in the fast scan direction are usually indicative of an underlying fault or marginal failure in the scanner with the result that copy quality degrades. The usual scanner failures which are evidenced by fast scan jitter are velocity variations in the scanner scanning element, scratched or dirty optical elements, misalignment of optical components, scan detection failures, and pixel clock circuit failures. If fast scan jitter could be readily detected and quantified, such scanner failures could be more readily detected, identified, and corrected; both while the scanner is being manufactured and later in the field when the scanner is in service.

Referring to the drawing Figures, to detect and measure fast scan jitter in a raster output scanner 2, a dual detector photodiode 3 composed of side by side sensors 4, 5 is positioned in the path of a scanning beam 6 so that where there is no jitter, equal amounts of light energy from beam 6 fall on each sensor 4, 5. Preferably, photodiode 3 is itself combined in side by side relation with the pair of sensor elements 7 that comprise the End Of Scan (EOS) detector 8 on a common chip. A pattern generator 9 provides a 4 bit packet of test pixels 10 for checking for jitter. The dual signal pulse output of photodiode 3 is fed to a differential integrator 11 such as a current mode operational amplifier used as a differential current controlled voltage source. The output of differential integrator I1 is passed to an...