Browse Prior Art Database

POLYGON MOTOR ANTIHUNTING CONTROL TECHNIQUE

IP.com Disclosure Number: IPCOM000024424D
Original Publication Date: 1980-Aug-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 1 page(s) / 66K

Publishing Venue

Xerox Disclosure Journal

Abstract

Raster output scanning systems have a problem with pixel misregistration due to variations in the scanning velocity of the laser beam. A portion of the laser beam velocity variation is due to hunting of the polygon drive motor. Attempts to compensate for laser beam velocity variations including polygon motor hunting have employed the technique of controlling the rate at which digital data is transmitted to the optical modulator. In these systems, laser beam velocity variations are optically sensed by start-of-scan and end-of -scan photodetectors and compensated for by increasing or decreasing the data rate.

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LEROX DISCLOSURE JOURNAL

SINE 41

'I

I1 I

POLYGON MOTOR ANTIHUNTING CONTROL TECHNIQUE
James C. Traino
Sidney Marshall

Proposed Classification
U.S. C1. 318/307 Int. C1. G05b 5/00

Raster output scanning systems have a problem with pixel misregistration due to variations in the scanning velocity of the laser beam. A portion of the laser beam velocity variation is due to hunting of the polygon drive motor. Attempts to compensate for laser beam velocity variations including polygon motor hunting have employed the technique of controlling the rate at which digital data is transmitted to the optical modulator. In these systems, laser beam velocity variations are optically sensed by start-of-scan and end-of -scan photodetectors and compensated for by increasing or decreasing the data rate.

An antihunting control system for the polygon drive motor is proposed instead. This is accomplished by monitoring back EMF of the motor and controlled by adjusting motor drive signal phasing. Referring to the figure, an amplitude- modulator (AM) detector 6 is utilized with a two-pole polygon drive motor 5 to separate out back EMF from the fundamental drive signal. The resulting signal, identified as the polygon motor hunting signal, is next multiplied by the sine wave of a quadrature oscillator 7 by multiplier 8 and the product input to adder 9 where the product is added to the quadrature oscillator's cosine wave. This shifts the cosine wave phase relative to that of the oscillator's si...