Browse Prior Art Database

SENSING POLYGON SPEED WITH CAPACITIVELY COUPLED TACHOMETER

IP.com Disclosure Number: IPCOM000026662D
Original Publication Date: 1993-Feb-28
Included in the Prior Art Database: 2004-Apr-06
Document File: 2 page(s) / 99K

Publishing Venue

Xerox Disclosure Journal

Abstract

It is commonly known to use a rotating polygon for raster scanning in order to expose a photoresponsive surface. For example US. Patent No. 4,349,847 to Traino (Issued Sept. 14, 1982) discloses such a raster output scanner (ROS). The motors used to rotate the polygons in ROS systems require accurate and stable speed control to achieve the desired image quality. Typically, motor control is achieved using a speed or position sensor in a feedback control loop to phase-lock the polygon drive motor to an oscillating signal. The present disclosure, however, is directed toward the use of a capacitively coupled tachometer to sense the polygon rotation. The use of a capacitive tachometer to sense rotation is well-known and is described in U.S. Patent No. 4,779,094 to Lee et al. (Issued Oct. 18,19881, and in U.S. Patents 4,563,683 and 4,477,810 to Tanaka et al. (Issued Jan. 7,1986 and Oct. 16,1984, respectively).

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XEROX DISCLOSURE JOURNAL

Proposed Classification

4

+ 4 VOLTS

SENSING POLYGON SPEED WITH CAPACITIVELY COUPLED U.S. C1.359/196 TACHOMETER Int. C1. G02b 26/10 Louis D. Mailloux

XEROX DISCLOSURE JOURNAL - Vol. 18, No. 1 Januarymebruary 1993 85

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SENSING POLYGON SPEED WITH CAPACITIVELY COUPLED TACHOMETE R(Cont'd)

It is commonly known to use a rotating polygon for raster scanning in order to expose a photoresponsive surface. For example US. Patent No. 4,349,847 to Traino (Issued Sept. 14, 1982) discloses such a raster output scanner (ROS).
The motors used to rotate the polygons in ROS systems require accurate and stable speed control to achieve the desired image quality. Typically, motor control is achieved using a speed or position sensor in a feedback control loop to phase-lock the polygon drive motor to an oscillating signal. The present disclosure, however, is directed toward the use of a capacitively coupled tachometer to sense the polygon rotation. The use of a capacitive tachometer to sense rotation is well-known and is described in U.S. Patent No. 4,779,094 to Lee et al. (Issued Oct. 18,19881, and in U.S. Patents 4,563,683 and 4,477,810 to Tanaka et al. (Issued Jan. 7,1986 and Oct. 16,1984, respectively).

The present sensing apparatus utilizes plated segments lying along the periphery of the polygon to generate a precise electrical signal that is used by the polygon motor control loop. As illustr...