Ning Chang

US Patent:

55154522, May 7, 1996

Filed:

Dec 31, 1992

Appl. No.:

7/999294

Inventors:

John A. Penkethman - Gilroy CA
Robert A. Harrison - Morgan Hill CA
Xiaoming Wang - San Jose CA
Ning S. Chang - Sunnyvale CA
Arye Green - San Jose CA

Assignee:

Electroglas, Inc. - Santa Clara CA

International Classification:

G06K 900

US Classification:

382141

Abstract:

An improved illumination method and apparatus for optical character recognition. A first light source is positioned such that light emitted from it strikes the surface at an angle of incidence. A detector is placed at the angle of reflection, such that specularly reflected light strikes the detector, providing bright field illumination. Additional light sources positioned at angles different from the first light source are disclosed to provide for high and low angle dark field illumination. Novel light guides which allow for a compact and economic system design are also disclosed. The disclosed system utilizes light sources and filters which greatly reduce the effect of environmental lighting on the optical character recognition process. A novel method to select the optimum light source and intensity is also disclosed.