Automatic beam current control with an envelope detector for a c

Facsimile and static presentation processing – Static presentation processing – Attribute control

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358 43, 358 47, 358219, H04N 907, H04N 904, H04N 9083, H04N 5235

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active

046529101

ABSTRACT:
A feedback control loop for controlling the intensity of a scanning electron beam of an image pickup tube of a color TV camera which is especially useful in a single tube color TV camera with a stripe filter, comprises an envelope detector for detecting the envelope of an output video signal derived from the image pickup tube. An envelope signal from the envelope detector is then compared with a reference threshold by a comparator so that a voltage applied to a control grid of the pickup tube is controlled in accordance with the amplitude of the envelope signal, thereby increasing the intensity of the scanning electron beam applied to a portion of a photoelectric converting layer when the brightness at the portion is high. As a result, an ideal multi-color output video signal is obtained irrespective of the brightness of a subject to be taken even if the intensity of the scanning electron beam is usually set to a relatively low value. In one embodiment, a circuit for amplifying high-frequency components of the output video signal is employed for compensating for a modulation characteristic of typical pickup tubes having a poor high frequency response.

REFERENCES:
patent: 2930929 (1960-03-01), Shelton
patent: 3610823 (1971-10-01), Haenen
patent: 3999011 (1976-12-01), Sato et al.
patent: 4041528 (1977-08-01), Miyoshi et al.
patent: 4365271 (1982-12-01), Blom
patent: 4427927 (1984-01-01), Nakamura
patent: 4593321 (1986-06-01), Blom et al.
Lubszynski, H. G., et al., "Some Aspects of Vision Performance", Journal Brit. I.R.E., May 1960, pp. 331-332.
Jay, Frank, Editor-in-Chief, IEEE Standard Dictionary of Electrical and Electronic Terms, Second Edition, 1977, pp. 21, 46.
National Convention Preprint of The Institute of Television Engineers of Japan, pp. 91 and 92 of 1974 edition.
Institute of Television Engineers of Japan, vol. 11, p. 22, date unknown.

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