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Document Illuminator using Elliptic and Dichroic Reflectors

IP.com Disclosure Number: IPCOM000076648D
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

Baxter, DW: AUTHOR [+3]

Abstract

Illuminator 10 produces a narrow strip 11 of intense illumination on a document such as mail piece 12, which is transported in the direction of arrow 13, Fig. 1. Light reflected from document 12 is transmitted through lens system 14 to a linear array of photodetectors 15.

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Document Illuminator using Elliptic and Dichroic Reflectors

Illuminator 10 produces a narrow strip 11 of intense illumination on a document such as mail piece 12, which is transported in the direction of arrow 13, Fig. 1. Light reflected from document 12 is transmitted through lens system 14 to a linear array of photodetectors 15.

The illumination originates in two cylindrical tungsten halogen lamps 16, each of which has a loosely coiled filament, as shown at 17. Elliptic-cylinder mirrors 18 have one focal line at the center of lamps 16, and the other focal line along the strip 11 in the plane of document 12. Thus, in accordance with the well-known properties of elliptic reflectors, mirrors 18 focus all incident light from lamps 16 onto strip 11. To increase the efficiency of mirrors 18, circular cylinder mirrors 19 centered about lamps 16 return light back through filaments 17 and onto mirrors 18, which nearly doubles the output of illuminator 10.

A major portion of the output of high-intensity tungsten-halogren lamps is in the infrared (lR) portion of the spectrum. In many applications only visible radiation is useful in the scanning of documents 12. If detectors 15 are silicon photodiodes, much of the desired signal is washed out, since such detectors are highly sensitive to near IR radiation. Also, both near and far IR radiation must be removed to protect document 12 from excessive heat in the small area of strip
11.

Fig. 2 shows two methods for removing unde...