Illumination – Photographic lighting – Light responsive
Patent
1990-05-22
1991-04-30
Hart, Douglas
Illumination
Photographic lighting
Light responsive
315151, 315158, 315208, 315224, 315291, 315307, G03B 1502, H05B 3904, G05F 100
Patent
active
050123920
ABSTRACT:
An automatic battery powered video light (10) is supplied power by a d.c. battery (16). A light (20) is connected between a first terminal of the battery (16) and a MOSFET switch (46), which is connected to a second terminal of the battery (16). A control circuit (24) controls the opening and closing of the MOSFET (46) to supply power to the light (20) and disconnect power from the light (20). The control circuit (24) includes a light sensor (36) for sensing ambient light and reflected radiant light from a scene (14) and a pulse modulator (40) for controlling the MOSFET switch (46). The modulator (40) adjusts pulse frequency and therefore closing time of the switch (46) when the sensor (36) senses time low light levels, and vice versa. Also provided is a dual filament light (20') wherein each filament (52, 54) is independently controlled to enhance color balance.
REFERENCES:
patent: 4238709 (1980-12-01), Wallace
patent: 4358717 (1982-11-01), Elliott
patent: 4368406 (1983-01-01), Kruzich
patent: 4412154 (1983-10-01), Klein
patent: 4464606 (1984-08-01), Kane
patent: 4673884 (1987-06-01), Geus
patent: 4682084 (1987-07-01), Kuhnel
patent: 4918357 (1990-04-01), Waterbury
patent: 4949016 (1990-08-01), De Bijl
patent: 4949020 (1990-08-01), Warren
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