Photoelectric apparatus for detecting altered markings

Details Photoelectric apparatus for detecting altered markings Photoelectric apparatus for detecting altered markings

1979-01-31

1981-02-10

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

356 71, G06K 710

Patent

active

042503930

ABSTRACT:
An optical reading apparatus is described for reading documents which contain information in the form of optical markings which deflect a reading beam coming from a light source in at least one given direction of deflection. A first light sensor detects a deflected partial beam. A second light sensor, the optical axis of which lies in a given direction of deflection, is only receptive to those light rays deflected at the document which lie outside a first cone and inside a second cone which is coaxial with the second light sensor. A comparator compares the electrical signals of both light sensors. Altered markings, which cause additional dispersion of the reading beam, can be reliably distinguished from the unaltered markings.

REFERENCES:
patent: 3809478 (1974-05-01), Talbot
patent: 3879131 (1975-04-01), Cuthbert et al.
patent: 4030835 (1977-06-01), Firester et al.

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