MARK IX CAMERA VIDEO PROCESSING SYSTEM.

The video processing system of an automatic color camera is described. Continuosly variable cable correction is provided to enable the camera to function correctly up to 900 m from the CCU using standard multi-core camera cable. A signal from the balance printed circuit board (manual or automatic) controls the amount of lift applied to the signals to offset dark currents in the pick-up tubes. Black and white shading correction (both linear and parabolic) is provided in horizontal and vertical directions to compensate for deficiencies in the lens/optic/tube combination. Voltage controlled variable gain amplifiers provide plus or minus 6 db gain for color balance (set-up) purposes; a further plus or minus 6 db gain for color traimming (limited to plus or minus 1 db on green) and 0-12 db master gain for use in low light conditions. An aperture corrector is included in the processing chain to provide the horizontal and vertical correction signals necessary for a sharp picture. A comb filter is included in the horizontal path to reduce cross-color and noise. The gamma correction is continuously variable from a law of 0. 4 to 0. 55 with a linear law available for set-up purposes. The signal is black and white clipped and then blanked before being available for use outside the board. The blanking rise and fall times are adjutable to suit differing national standards.