Browse Prior Art Database

Elliptical Light Collector

IP.com Disclosure Number: IPCOM000074310D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Cecchi, DR: AUTHOR [+2]

Abstract

Scanner 10 presents an efficient system for collecting diffuse reflections of a light beam from a document for optical character readers, mark readers and similar apparatus.

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At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 97% of the total text.

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Elliptical Light Collector

Scanner 10 presents an efficient system for collecting diffuse reflections of a light beam from a document for optical character readers, mark readers and similar apparatus.

Optical beam deflector 11 produces a scanned light ray 12 which impinges upon document plane 13 at point 14. Reflective surface 15 formed in the body of scan head 16 receives diffuse rays 17 reflected from point 14 and redirects them to reflective surface 18, which may be mounted upon transparent dust cover 19. Surface 18 reflects rays 17 onto the sensitive surface of small-area photodetector
20. Reflector 15 has an elliptical cross section with foci at points 14 and 21. Elliptical reflectors have the well-known property that all light rays originating at one focus also pass through the other focus. But, since it would be impractical to place a photodetector in the document plane at point 21, reflector 18 is so placed that an image of focus 21 appears on the surface of detector 20. Equivalently, it may be said that an image of detector 20 is placed at focus 21. Thus, substantially all of the rays 17 which are reflected at various angles from point 14 will be collected by detector 20.

Reflector 15 may have the shape of an elliptical cylinder, an ellipsoid of revolution, or similar configuration. Reflector 18 may be a plane mirror, or a curved surface to obtain a focusing effect for light which is reflected from points in the neighborhood of focus 14.

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