Automatic aperture control of a television camera

Details Automatic aperture control of a television camera Automatic aperture control of a television camera

1987-12-11

1989-05-09

Chin, Tommy P.

Facsimile and static presentation processing

Facsimile

Recording apparatus

35821313, 358162, 358 41, H04N 5232, H04N 5235

Patent

active

048293822

ABSTRACT:
R, G and B outputs from the corresponding preamplifiers of a television camera are supplied to a non-additive mixer (NAM) circuit for continuous selection of the greatest of the three outputs and the selected output is continuously supplied to a set of 9 electronic switches each selecting out a subdivision of the picture field (a, b . . . i). The switched outputs for each of the subfields are then provided to respective subfield measurement detectors which each produce an average value output and a peak value output. These are stored into subfield buffer units and then read out through a multiplexer and an analog to digital converter to a microprocessor. The various values are compared with corresponding past values for selecting between various measurement schemes for obtaining a camera diaphragm control signal, namely spot measurement, center-emphasized integral measurement and selective field measurement. Except when a decision for no setting change is made, the selected scheme of measurement is used to obtain a control signal from the average and dynamic range values of the several subfield video signals.

REFERENCES:
patent: 4409620 (1983-10-01), Enomoto
patent: 4532550 (1985-07-01), Bendell
patent: 4542403 (1985-09-01), Zimmermann

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