Communications: electrical – Digital comparator systems
Patent
1974-07-17
1976-07-06
Thesz, Joseph M.
Communications: electrical
Digital comparator systems
3401463F, 250233, G06K 913
Patent
active
039684768
ABSTRACT:
An improved incoherent optical processor fingerprint identification apparatus employs a rotatable grating for inspecting the ridge orientations in a plurality of preselected finite sample areas of a fingerprint. A detector array including a plurality of detectors each related to a discrete sampled area is disposed to receive an image of the fingerprint filtered by the rotating grating. An incoherent light source and a lens and retroreflective prism assembly function in cooperation with the grating to produce an image thereof superposed on the grating itself such that minimum light is propagated to the detector array in the absence of an input fingerprint pattern whereas, in the presence of a fingerprint pattern, light is diffracted thereby to be filtered by the grating for supply to the detectors. Maximum light may occur at each detector under a condition of spatial alignment of the grating lines with the ridge lines of the related sampled area whereby the time interval between a reference orientation of the grating and the instant of maximum light at each detector may be converted to equivalent electrical signals uniquely representative of a particular fingerprint pattern. The signal to noise factor of the optical system is significantly improved by the use of a novel grating element having plural reflecting and transmitting stripes, with optically absorbing stripes interposed between them.
REFERENCES:
patent: 3497704 (1970-02-01), Holmes et al.
patent: 3522437 (1970-08-01), Bargh
patent: 3771124 (1973-11-01), McMahon
patent: 3778620 (1973-12-01), Lindemann et al.
Sperry Rand Corporation
Terry Howard P.
Thesz Joseph M.
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