GB1256862A - - Google Patents

Abstract

1,256,862. Television. BRITISH BROADCASTING CORP. 3 Feb., 1969 [3 Nov., 1967], No. 50169/67. Heading H4F. To test and equalize two video signals e.g. the signals from two cameras televising a scene or the primary colour signals from a colour television camera, the signals are applied alternately by means of a selector switch to a televison image reproducer, and the amplitude of at least one of the signals is adjusted to render identical the brightness of the two recurring images. As shown a grey scale test card 14 is televised by a colour camera 10 and the green- and either the red or blue signals (via manually operable switch 18) are applied to the two inputs of electronic selector switch 15. Switch 15 is controlled by a switching signal from a pulse counter 19 which divides by four line drive pulses from a terminal 21 or mixed synchronizing pulses from terminal 22 so that four lines of each signal are reproduced by a monochrome monitor 23 alternately as a slowly moving (unlocked) or stationary (locked) pattern. For colour balance the outputs at 11, 12 and 13 should be equal for each vertical band of the grey scale chart. In operation the green and red signals are displayed and the amplitude of the red signal is adjusted until the horizontal (four line) bands of different brightness are not visible, and then the same is done for the green and blue signals. Auxiliary inputs 24 and 25 on switch 18 may receive a green signal from another camera to match the outputs of two colour cameras, and a locally generated gammacorrected sawtooth to which the green signal at 11 may be equalized.