Recorders – Printing – dotting – or punching marker – Ink transfer support or moving means
Patent
1989-05-10
1990-04-24
Evans, Arthur G.
Recorders
Printing, dotting, or punching marker
Ink transfer support or moving means
346108, G01D 1500
Patent
active
049203649
ABSTRACT:
A variable attenuator for controlling scanning beam intensity having a twisted nematic liquid crystal for rotating the beam, a polarization analyzer for detecting the degree of alteration in the polarization of the beam by the crystal comprising a polarizing beam splitting plate separating the beam into primary and secondary beams, a photocell providing a signal reflecting the intensity of the secondary beam, a control for adjusting power to the crystal in response to the signal, a glass plate at an angle of incidence equal to but opposite from that of the beam splitting plate for correcting aberrations to the primary beam, and an anti-reflective coating on the optical surfaces of the crystal.
In a second embodiment, the plates are replaced by a polarizing cube. In a third embodiment, to obviate fluctuations in the attenuator output, the glass plate instead serves as the source of the beam component to the photocell.
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"Wide Dynamic Range CCD Camera"; Younse et al., SPIE 501, 55 (1984).
"Optical Rotatory Power of 90.degree. Twisted Nematic Liquid Crystals", Wu et al., Appl. Phys. Lett., vol. 44, pp. 842-844 (1984).
"Liquid Crystal Device for Optical Radiation Control", Azarov et al., Instrum and Exp. Tech. (U.S.A.), 24, 487 (1981).
"The Optical Properties of Twisted Nematic Liquid Crystal Structures with a Twist Angle.ltoreq.90.degree.", Gooch et al., J. Phys., vol. 8, pp. 1757-1584, (1975).
"CVI Produces a Polarizer for Every Purpose", CVI Laser Corporation.
Andrews John R.
Guerin Jean-Michel
Haas Werner E.
Evans Arthur G.
McMullen Frederick E.
Xerox Corporation
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