US 4,542,403 AGranted

Method of confining the signal level range of a television camera

OwnerFriedrich Zimmermann, Herbert Zettl +2inventors

InventorsFriedrich Zimmermann, Herbert Zettl, Hans W. Zappen, Christian Sacher

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Abstract

Before the camera is used to transmit a scene, a key or button (21) is actuated which causes a measurement field generator (23) to define a small portion of the picture field, where the video signal level of the greatest of the three color components will be compared with a reference level in an aperture control circuit (6) for setting the camera lens aperture. If this should result in a lens aperture above an upper limit or below a lower limit, an amplification step control (26) for an amplifier (8) is shifted one step so as to bring the lens aperture between the aforesaid limits. The comparison of the video signal level with the reference level is repeated until the amplification is sufficient to bring the lens aperture into the desired range. The measurement field is shown in the camera finder (14) and likewise any off-limits setting of the lens aperture and whether the manual control (28) is on a setting that permits the automatic amplification control to operate.

Claims5

Dependent claims

Method of signal level setting of a color television camera having an electronic finder, in accordance with scene brightness, by use of a camera equipped with an opto-electronic converter for delivering a video signal, an automatic camera aperture control, a video amplifier of switchable degree of amplification and amplifier control switching means, comprising the steps of:

measuring, in a selected measurement portion of the picture field, the video signal derived from the scene by the opto-electronic converter of the camera;
comparing the measured video signal with a reference value and operating the camera aperture control so as to bring the measured video signal towards said reference value;
comparing the camera aperture setting produced by the camera aperture control with predetermined upper and lower pre-limit values, selected to be somewhat inside the available extreme values of aperture, and operating said amplifier control switching means in response to overstepping of said upper pre-limit or understepping said lower pre-limit value so as to make a corrective change step, in the degree of amplification of said derived video signal;
repeating the above steps if and to the extent necessary to bring the camera aperture setting within the range limited by said pre-limit values, and
indicating in the camera finder the nominal amount of amplification, if any, provided in the video channel by said amplifier.

2 more elements

Dependencies are inferred from the claim text.