Browse Prior Art Database

Laser Printhead Beam Power Servo

IP.com Disclosure Number: IPCOM000052994D
Original Publication Date: 1981-Aug-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Froess, RJ: AUTHOR

Abstract

This article describes an apparatus which reduces exposure potential variation in an electrophotographic system caused by changes in laser power, modulator efficiency and photoconductor sensitivity by providing a laser beam power servo system.

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Laser Printhead Beam Power Servo

This article describes an apparatus which reduces exposure potential variation in an electrophotographic system caused by changes in laser power, modulator efficiency and photoconductor sensitivity by providing a laser beam power servo system.

The electrophotographic system includes a laser 10 which is used as a light source to selectively discharge incremental areas of the photoconductor (not shown) in response to the data from control assembly 12. The data is coupled to modulator driver 14 to control modulator 16 to produce an appropriately modulated beam which is scanned across the photoconductor by rotating mirror
18.

A scan start detector 20 is positioned in the beam path to intercept the beam in its sweep caused by rotating mirror 18 when it is about to start across the photoconductor. The output of scan start detector 20 is coupled to an input of control assembly 12 to produce a synchronization signal for the data and also to a laser power detector 22 which relates the output level of the scan start detector to laser power. This level is coupled to compare circuit 24 which compares the level with an input from photoconductor temperature sensor 26.

An appropriate error signal for modulator drive level control is then generated by appropriate sample and hold, analog-to-digital and logic circuits using standard sampled data servo techniques. This error signal is coupled on line 28 to modify the output of modulator driver 14. T...