Columnar focusing indicator for a manually focused video camera

Details Columnar focusing indicator for a manually focused video camera Columnar focusing indicator for a manually focused video camera

1987-12-28

1988-12-27

Chin, Tommy P.

Facsimile and static presentation processing

Facsimile

Recording apparatus

358224, 354409, H04N 5232, H04N 530

Patent

active

047944595

ABSTRACT:
A focusing aid for a manually-focused video camera provides an indication of optimum focus by switching the d.c. level of the video signal between two values according to its high frequency content. The switched d.c. levels generate a brightness transition that is confined to a columnar region occupying one side of the display in an electronic viewfinder. A high frequency component is separated from the video signal and converted into a d.c. control signal having an amplitude that varies with frequency content. By accumulating the d.c. control signal for each video field and switching a voltage divider in response to the amplitude of the accumulated control signal, a transition between d.c. levels is generated that is time-wise dependent upon high frequency content. The switched d.c. level is injected into the video signal during the scanning of the column. The resulting transition between video levels is seen as an abrupt brightness shift that moves up or down in the column in relation to high frequency content. Optimum focus is obtained by adjusting the focus and bringing the transition to its lowermost position in the column.

REFERENCES:
patent: 3435136 (1969-03-01), Bachmann
patent: 4282548 (1981-08-01), Plummer
patent: 4317135 (1982-02-01), Pitruzzello
patent: 4392726 (1983-07-01), Kimura
patent: 4463384 (1984-07-01), Fujikawa
patent: 4481540 (1984-11-01), Bergen
patent: 4484225 (1984-11-01), Bishop
patent: 4583123 (1986-04-01), Baier
patent: 4586090 (1986-04-01), Wilman
patent: 4599653 (1986-07-01), Kimura

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