INFRARED FILTER FOR AN ELLIPTICAL REFLECTOR
Original Publication Date: 1984-Feb-29
Included in the Prior Art Database: 2004-Apr-04
Xerox Disclosure Journal
For certain document imaging system, a highly concentrated band of energy must be directed at the document support platen to ensure a proper exposure level at the image plane. This type of illumination system typically generates a considerable amount of heat which must be reduced to levels that can be tolerated by platen and other optical components. The figure shows an illumination system 10 adapted to provide a narrow, intense beam of light to a document 12 placed on platen 14. The illumination consists of a linear segmented tungsten halogen lamp 16 whose radiant energy output is concentrated and focused to form a peaked profile at scan strip 18 by associated elliptical reflectors 20, 22, and opposing reflector 23. To reduce the heat at the platen, an infrared filter 24 is attached to reflector 22 as shown. Filter 24 can be a "hottr mirror with a cutoff at 700 nm. The filter, whose exact position can be adjusted as shown, would transmit visible radiation from 400 nm to 700 nm, without disturbing the color balance or the peak profile. The infrared radiation, however, is reflected back into the cavity formed by reflectors 20, 22. Air can then be circulated through the cavity to dissipate the heat buildup.