04831275 is referenced by 53 patents and cites 40 patents.

A scanning device and method for reading bar-code or other contrasting marks from a surface at variable distance from the scanning device operates by modulating the focal point of the optical system to yield pulse responses on detected code bars while in focus, and average background response levels from the bar-code surface while out of focus. Modulation of focal point of the optical system is achieved in selected ways such as by positioning optical elements using piezoelectric or electromagnetic drivers or liquid-crystal elements, or by staggering the positions along an optical axis of arrays of optical sensors, or of optical fibers coupled to the sensors.

Title
Method and means for self-referencing and self-focusing a bar-code reader
Application Number
6/930328
Publication Number
4831275
Application Date
November 12, 1986
Publication Date
May 16, 1989
Inventor
Steven H Drucker
Oakland
CA, US
Agent
A C Smith
Assignee
Quential
CA, US
IPC
G06K 7/14
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