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Optical System for Uniform Light Distribution

IP.com Disclosure Number: IPCOM000085703D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Cunningham, E: AUTHOR [+2]

Abstract

In applications such as a hand-held optical scanner, a small lamp may be placed within the scanner housing to provide illumination for one or more photodetectors. A lamp for this or similar purposes should provide uniform light intensity over an area, such as the interval A'B' about optical axis C' in Fig. 1. Most lamps, however, produce peaked distributions, as shown by curve 10.

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Optical System for Uniform Light Distribution

In applications such as a hand-held optical scanner, a small lamp may be placed within the scanner housing to provide illumination for one or more photodetectors. A lamp for this or similar purposes should provide uniform light intensity over an area, such as the interval A'B' about optical axis C' in Fig. 1. Most lamps, however, produce peaked distributions, as shown by curve 10.

Optical system 20, Fig. 2, gathers light from a source, not shown, in interval AB of a plane 21. Plano-convex lenses 22, 23 have foci at planes 21 and 24, respectively. A circular aperture 25 is placed between lenses 22, 23. Such a system still has a peaked intensity-distribution curve similar to 10, Fig. 1.

A small cylindrical rod 26, however, may be placed between plane 21 and lens 22 to obtain a nearly uniform distribution, shown as curve 11 in Fig. 1. Since rod 26 is not located at the focus of either lens, its image on plane 24 is quite fuzzy, and produces a broad and gradual decrease in intensity, rather than a sharp, shadow-like valley. Rod 26 may be moved along axis CC' and adjusted in size to achieve an optimally flat distribution in plane 24. If a uniform two- dimensional distribution is desired, another rod, not shown, may be placed at right angles to rod 26; i.e., vertically in the plane of Fig. 2.

The shapes and spacing of aperture 25 and rod 26 can be varied to obtain a variety of light distribution patterns, both uniform and n...