Browse Prior Art Database

Low-Eccentricity, Elliptical-Cylindrical Illumination System

IP.com Disclosure Number: IPCOM000044359D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

Grant, DE: AUTHOR [+3]

Abstract

The figure shows an illumination system wherein a low eccentricity elliptical-cylindrical reflector 1 with a shallow curvature is used to generate a narrow footprint of light 2 at a document glass 3. The light rays 4, reflecting from an object or a document, are deflected via a mirror 5 positioned at an inclined angle (such as 45Œ) relative to the object and into an objective lens (not shown). The light from the objective lens may then be incident on an image plane containing light-sensitive arrays (not shown). The elliptical-cylindrical reflector uses a section of the ellipse arc 6 around the intersection of the minor axis with the ellipse arc where the source magnification is unity.

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Low-Eccentricity, Elliptical-Cylindrical Illumination System

The figure shows an illumination system wherein a low eccentricity elliptical- cylindrical reflector 1 with a shallow curvature is used to generate a narrow footprint of light 2 at a document glass 3. The light rays 4, reflecting from an object or a document, are deflected via a mirror 5 positioned at an inclined angle (such as 45OE) relative to the object and into an objective lens (not shown). The light from the objective lens may then be incident on an image plane containing light-sensitive arrays (not shown). The elliptical-cylindrical reflector uses a section of the ellipse arc 6 around the intersection of the minor axis with the ellipse arc where the source magnification is unity. As such, small collective wrap angles 8 of the light source 9 can be used, and still obtain high peak irradiance at the footprint center when compared to more eccentric and higher magnification systems. Due to the shallow curvature of the reflector, a cold mirror coating 10 can be placed on the concave side of the sagged glass reflector. A heat-absorbing shield 11 is located at the back side of the reflector and absorbs heat transmitted through the cold mirror coating. A light source having a double- shell lamp housing 12 is positioned to allow incident light rays onto the reflecting surface of the ellipse. By this technique, forced air can be introduced between the housing for cooling the system without blowing it direc...