Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1977-06-16
1979-02-27
Tokar, M.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
250560, 250561, 250209, G01N 2130
Patent
active
041421051
ABSTRACT:
A photoelectric detection system which has two sequential photoelectric receivers to determine the precise moment at which the boundary between two contrasting fields passes beneath the detectors irrespective of the relative contrast between the two fields. The signals from the two photoelectric detectors which change as the boundary progressively obscures their respective fields of view are firstly subtracted to produce a difference signal. The difference signal is then passed to a gated maximum value store which is operative during each difference pulse to store the maximum value of the difference occurring during that pulse. A fraction of this maximum value is then taken and compared with the instantaneous value of the difference as this value reduces, when these two values are equal an output pulse is generated and this output pulse always occurs at the same position of the boundary relative to the photoelectric receivers irrespective of the respective levels of contrast on either side of the boundary. In a modification especially useful for detecting the two boundaries of a register mark two sequential pulses are formed indicative of the movement of the two respective boundaries past the photoelectric receivers.
REFERENCES:
patent: 3710128 (1973-01-01), Kubisiak
patent: 3777167 (1973-12-01), Shepherd
patent: 3907439 (1975-09-01), Zanoni
patent: 4025796 (1977-05-01), Erdmann
Erwin Sick Gesellschaft mit beschrankter Haftung Optik-Elektroni
Tokar M.
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