Raster scanner with a selectable spot dimension

Details Raster scanner with a selectable spot dimension Raster scanner with a selectable spot dimension

1996-06-17

1999-10-19

Metjahic, Safet

Incremental printing of symbolic information

Electric marking apparatus or processes

Electrostatic

347239, 347255, B41J 2385, B41J 247

Patent

active

059697415

ABSTRACT:
Raster scanner assemblies, and machines which use such raster scanner assemblies, which produce spots having a variable spot dimension. Raster scanner assemblies according to the present invention include an electronic subsystem which produces both image data and a spot size control signal, a laser assembly which produces a polarized laser beam having a beam with a first dimension and which is modulated in accord with the image data, a variable aperture assembly which changes the first dimension of the laser beam, a rotating polygon having a plurality of facets sweeping the laser beam in a sweep plane, and a scan lens for focusing the laser beam onto an image plane. The variable aperture assembly beneficially includes both a liquid crystal cell, which receives the laser beam and the spot size control signal, and a polarizing filter. The liquid crystal cell changes the polarization of part of the laser beam in response to the spot size control signal, while the polarizing filter passes the laser beam as a function of the beam's polarization. Beneficially, the liquid crystal cell is a twisted nematic liquid crystal cell. Preferably, the first dimension is in the cross-scan direction.

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Electro-Optical Devices and System by Mohammad A. Karim, Ph.D., PWS-Kent Publishing Co., pp. 278-303, 1990.

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