Browse Prior Art Database

DYNAMIC BELT TRACKING USING SPECKLE METROLOGY

IP.com Disclosure Number: IPCOM000026949D
Original Publication Date: 1994-Aug-31
Included in the Prior Art Database: 2004-Apr-07
Document File: 2 page(s) / 83K

Publishing Venue

Xerox Disclosure Journal

Abstract

Multicolor printing in an electrostatic printing machine necessitates that a photoconductive belt be accurately tracked in both the circumferential and lateral directions. The present process of tracking the photoconductive belt with timing marks and lateral low friction rolls impedes tracking ability when image on image transfer technology is desired. At least 40 percent of all image registration problems are related to the edge of the photoconductive belt. The edge profile is typically smooth at 400-500 microns, of which approximately 150 microns are desired for lateral tracking. Motion control, in the process direction requires a positional accuracy of 25 microns or less, creating a need to directly encode the photoconductive belt for servomechanism control. Specifically, the use of a laser and a matrix array detector is proposed to create and measure the speckle pattern (power intensity pattern) produced by the laser as the coherent laser light is reflected off an organic photoconductive belt surface. The detected speckle pattern is then used as a "fingerprint" of the belt position.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 62% of the total text.

Page 1 of 2

XEROX DISCLOSURE JOURNAL

DYNAMIC BELT TRACKING USING SPECKLE METROLOGY US. C1.355/212 Douglas P. Kancler

Proposed Classification

Int. CI. G03g 05/00

Multicolor printing in an electrostatic printing machine necessitates that a photoconductive belt be accurately tracked in both the circumferential and lateral directions. The present process of tracking the photoconductive belt with timing marks and lateral low friction rolls impedes tracking ability when image on image transfer technology is desired. At least 40 percent of all image registration problems are related to the edge of the photoconductive belt. The edge profile is typically smooth at 400-500 microns, of which approximately 150 microns are desired for lateral tracking. Motion control, in the process direction requires a positional accuracy of 25 microns or less, creating a need to directly encode the photoconductive belt for servomechanism control. Specifically, the use of a laser and a matrix array detector is proposed to create and measure the speckle pattern (power intensity pattern) produced by the laser as the coherent laser light is reflected off an organic photoconductive belt surface. The detected speckle pattern is then used as a "fingerprint" of the belt position.

Since an organic photoconductive belt is a thin film device, it is possible to expose the belt with a laser which emits a suitable wavelength that reflects a speckle pattern. The pattern is then reflected or imaged onto a matrix array...