Browse Prior Art Database

DIGITAL CONTROL SYSTEM FOR COPIER SCAN SERVO

IP.com Disclosure Number: IPCOM000024816D
Original Publication Date: 1982-Apr-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 4 page(s) / 148K

Publishing Venue

Xerox Disclosure Journal

Abstract

In the drawing, there is shown a proposed system for implementing digital control over a copier scan servo. Referring thereto, an apertured timing disc 5 is attached to and rotatable with the copier photoreceptor (PR). The clock signals generated by a detector 6 on rotation of disc 5 are fed to a suitable frequency multiplier 7 which steps up the signal frequency, i.e., to 100 KHz. This permits control on a high resolution basis.

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Page 1 of 4

KEROX DISCLOSURE JOURNAL

DIGITAL CONTROL SYSTEM FOR COPIER SCAN SERVO U.S. C1. 355/8 Morton Silverberg

Proposed Classification

Int. C1. G03g 15/28

M ULT I PLIER'

Volume 7 Number 2 March/April 1982 99

P/ R

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

Page 2 of 4

DIGITAL CONTROL SYSTEM FOR COPIER SCAN SERVO (Cont'd)

In the drawing, there is shown a proposed system for implementing digital control over a copier scan servo. Referring thereto, an apertured timing disc 5 is attached to and rotatable with the copier photoreceptor (PR). The clock signals generated by a detector 6 on rotation of disc 5 are fed to a suitable frequency multiplier 7 which steps up the signal frequency, i.e., to 100 KHz. This permits control on a high resolution basis.

A set of counters 9, 10, 11 are used to compare the measured time between suc- cessive clock pulses with the desired time for a given point in the desired scan acceleration or deceleration profile. To that end, the clock signals generated by frequency multiplier 7 are input to pulse interval counter 9 where the count is compared with the desired interval count on counter 10 by difference counter 11. The signal output by difference counter 11 is converted to analog by digital to analog (D/A) converter 12 and fed via a suitable conventional analog servo phase compensation network 13 to one input of summing circuit 15. The output of sum- ming circuit 15 is fed via control switch 16 to servo power driver 17 for scan drive motor 18. Control switch 16 is set in the solid line position shown during system operation and moved to the dotted line position on stopping of the system.

Another set of counters 29, 20, 21 are provided to compare the desired movement of the scan servo versus movement of the copier photoreceptor. For this, the clock signals generated by frequency multiplier 7 are input to accumulated difference counter 19 which is used to measure how far the photoreceptor advances between each successive clock pulse. The count on counter 19 is compared with a desired increment count on counter 20 by difference counter 21. The output of counter 21, which represents the comparison of desired increment with actual increment plus (or minus) previous errors, is fed to D/A 22 where the signal is converted to analog. From D/A 22, the signal is fed through servo phase compensation network 23 to a second input of summing circuit 15.

The desired interval count and increment count to which counters 10, 20 are set may be derived from any suitable computer program or extracted from a look-up table.

One shot multi-vibrator 25 and flip flop 26 are provided to permit comparison to take place just after a photoreceptor clock pulse and before the next clock pulse. For...