Automatic aperture control of a television camera
US4829382A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 11, 1987 |
| Grant date | May 9, 1989 |
| Priority date | — |
| Expiry date | Dec 11, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N23/71
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.