04011435 is referenced by 69 patents and cites 11 patents.

An optical marking system which utilizes tags that are formed from multiple diffraction gratings, which gratings differ in orientation and number of lines (frequency) in accordance with the coded information desired on the tags. A monochromatic light source illuminates a diffraction grating tag, with reading of the coded information on the tag being accomplished by sensing the reflected light which is projected as images in a Fraunhofer plane. Retroreflective elements are provided in the optic train as a means for stabilizing the direction of reflection from the diffraction gratings such that the reflections are somewhat independent of the tilt angle of the tag with respect to the illuminating light.

Title
Optical indicia marking and detection system
Application Number
5/438886
Publication Number
4011435
Application Date
February 1, 1974
Publication Date
March 8, 1977
Inventor
William R Horst
Dayton
OH, US
Robert A Phelps
Kettering
OH, US
Agent
Elmer Wargo
Albert L Sessler Jr
J T Cavender
Assignee
NCR Corporation
OH, US
IPC
G11C 11/44
G06K 9/04
G06K 7/14
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