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12 May 1995 Liquid crystal variable attenuator for high-speed printing
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Proper exposure of the photoconductor in an electrophotographic printing system is essential for high quality printing. Gas lasers such as helium-neon and helium-cadmium lasers do not lend themselves to easy electronic power control. To set proper exposure in an electrophotographic system, it is necessary to deal with a number of time varying factors including laser intensity, acousto-optic modulator efficiency, photoreceptor sensitivity, and toner developability. A nematic liquid crystal based variable laser attenuator was developed as a means of setting exposure accurately in a closed-loop exposure control system. This paper describes some of the design considerations and performance parameters for the variable attenuator. The system is compact, low cost, has high throughput, provides an exposure range > 100:1, and has sufficient speed to reset exposure between consecutive prints. The liquid crystal variable attenuator is used in a variety of Xerox printing products including the DocuTech Production Publisher and the Xerox 4850 Highlight Color Laser Printer.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
John R. Andrews and Jean-Michel Guerin "Liquid crystal variable attenuator for high-speed printing", Proc. SPIE 2383, Micro-Optics/Micromechanics and Laser Scanning and Shaping, (12 May 1995);

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