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Browse Prior Art Database

Laser Diode Controller

IP.com Disclosure Number: IPCOM000047167D
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Jorgenson, GW: AUTHOR

Abstract

This article describes an analog circuit for use in controlling the current in a laser diode used in an electrophotographic printing system. Fig. 1 shows a laser diode 10 which produces a beam of light striking the mirrored surface of rotating fly wheel 11. Fly wheel 11 redirects the beam of light in a scanning manner across the surface of electrophotographic drum 12. As each facet of the mirror on fly wheel 11 catches the beam of light produced by a laser diode 10, the beam of light is directed to a start of scan mirror 13 from which it is reflected to photodetector 14. The rotating mirror on fly wheel 11 then causes the beam of light to scan across the drum surface to the end of scan mirror 15 from which the light beam is again redirected to photodetector 14.

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Laser Diode Controller

This article describes an analog circuit for use in controlling the current in a laser diode used in an electrophotographic printing system. Fig. 1 shows a laser diode 10 which produces a beam of light striking the mirrored surface of rotating fly wheel 11. Fly wheel 11 redirects the beam of light in a scanning manner across the surface of electrophotographic drum 12. As each facet of the mirror on fly wheel 11 catches the beam of light produced by a laser diode 10, the beam of light is directed to a start of scan mirror 13 from which it is reflected to photodetector 14. The rotating mirror on fly wheel 11 then causes the beam of light to scan across the drum surface to the end of scan mirror 15 from which the light beam is again redirected to photodetector 14. As a result of the scanning system, photodetector 14 is caused to contain intensity information of the light beam produced by laser diode 10, and this information is updated once every scan line. The value of the light beam intensity is converted to current by photodetector 14 and then to voltage by amplifier 16 to provide output voltage VF . Fig. 2 shows the voltage pulses of VF produced from amplifier 16 in response to the detected laser beam. Note that these pulses signify the end and start of scan. Time TS represents the time between the start of one scan and the start of the next succeeding scan. Sample and hold circuit 17 samples voltage VF every TS time to produce a continuous...