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IP.com Disclosure Number: IPCOM000024917D
Original Publication Date: 1982-Oct-31
Included in the Prior Art Database: 2004-Apr-04

Publishing Venue

Xerox Disclosure Journal


Figure 1 shows an optical system employed in a copier where a document 19, placed on a platen 12, is illuminated by means of a lamp 14, reflector 16 combination. As the platen is moved in the indicated direction, the document is incrementally scanned with the reflected images projected through a linear gradient index lens 18 onto a photoreceptor 20. In order to enable continuous exposure adjustment of this projected image, there is inserted a thin transparent plate 22 in a suitable location between lens 18 and photoreceptor 20. Exposure adjustment is achieved by rotating plate 22 from the horizontal plane (least attenuation) toward the vertical (greatest attenuation). The attenuation is a result of higher specular reflections at the plate surface as the angle of incidence increases. The total plate transmittance, as calculated from Fresnel reflection equations is: