Browse Prior Art Database

Illumination System

IP.com Disclosure Number: IPCOM000076698D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Dattilo, AJ: AUTHOR

Abstract

A document is illuminated by two 17 inch linear xenon flashtubes operated in serves. The tubes are mounted in reflectors made from sections of flat rear surface mirror. Fig. 1 is a view showing the configuration with lamps 1 and 2, end reflectors 3 and 4, and side reflectors 5 and 6. Fig. 2 is a sketch of one lamp and side reflector and one end reflector. Fig. 3 is a section through lamp 1 and side reflector 5, showing relative positions with respect to the document plane 9.

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Illumination System

A document is illuminated by two 17 inch linear xenon flashtubes operated in serves. The tubes are mounted in reflectors made from sections of flat rear surface mirror. Fig. 1 is a view showing the configuration with lamps 1 and 2, end reflectors 3 and 4, and side reflectors 5 and 6. Fig. 2 is a sketch of one lamp and side reflector and one end reflector. Fig. 3 is a section through lamp 1 and side reflector 5, showing relative positions with respect to the document plane 9.

The lamp positions, reflectors and light shields are chosen to give an illumination distribution on the document plane 9 that compensates for the relative illumination characteristic of lens in the system, not shown. The desired illumination pattern is achieved to a great extent by masking the center of the flashtubes and/or the reflectors, as shown at 7 and 8. The result is a flat illumination over the image plane for a document of constant reflectivity. The document plane distribution may be defined on a polar coordinate system centered on the optical axis of the lens as follows: I = Io / cos/4/ (tan/-1/ r/2f)

Io is intensity for r = 0

f is the focal length of the lens.

The reflector design and lamp positions are also chosen so that no light source is directed onto the image plane, by way of reflections from the under side of the document plane glass. This is achieved by keeping all light sources and their images outside the critical plane, Fig. 3. The lamps are cooled b...