Browse Prior Art Database

Illumination System with Variable Contour Mask

IP.com Disclosure Number: IPCOM000082836D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Conly, DJ: AUTHOR

Abstract

An illumination system for a copier machine employs a variable-contour mask, to compensate for the differing light falloff characteristics of the positionable lens system.

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Illumination System with Variable Contour Mask

An illumination system for a copier machine employs a variable-contour mask, to compensate for the differing light falloff characteristics of the positionable lens system.

The illumination system of the copier machine includes a light source 11, whose light rays are reflected from the paraboloid surface 13 onto a scanning parabolic reflector 15. Light source 11 is located at the focus of the paraboloid surface 13, causing the reflected rays 17 to be parallel to one another. The parallel rays striking the parabolic reflector 15 are reflected to the focus thereof located on the document plane 19. These light rays 21 form a band of light 23 which moves as the parabolic reflector 15 moves. Light reflected from the document plane 19 passes through lens 25 and is focused thereby onto a photoreceptive surface. This optical system is described in U. S. patent 3,758,774.

Mask 27 blocks some of the light rays 17 between paraboloid surface 13 and parabolic reflector 15, thereby causing more light to be reflected from the ends of the parabolic reflector 15 than from the center thereof. The extra intensity at the edges of the line of light 23 compensates for the light falloff characteristics of the lens 25.

The mask 27 has a slidable member 29 positioned thereon. Movement of the slidable member 29 is coordinated with movement of lens 25 in the direction of arrows 31, when effecting a magnification change. The slidable member 29 t...