GB1021322A - Improvements relating to colour television - Google Patents

Abstract

1,021,322. Colour television test apparatus. J. A. SHIPWAY. Aug. 24, 1964 [May 31, 1963], No. 21992/63. Heading H4F. A test apparatus for colour television receivers comprises a signal source 1 generating a black and white test picture signal the colour information from which is transmitted to the red, green and blue inputs of a matrix 2 via switches 3, 4 and 5 operated sequentially by a line-by-line switch generator 6, the matrix 2 producing chrominance signals " I " and " Q " and luminance signals " Y " in accordance with the transmitted information, and means for suppressing the chrominance signals during part of the test transmission so as to produce, in a correctly adjusted receiver, a test pattern composed of monochrome areas of equal hue formed respectively by the luminance signals only and the chrominance signals. In the area formed by the chrominance signals the luminance signals may or may not be suppressed. The chrominance signals may be suppressed during the first half of each line by means of half-line switches 8 so that the test pattern produced for example consists of two vertical grey scales positioned side-by-side, one of the scales being transmitted with the sequential chrominance signals suppressed. Synchronizing pulses from a source 7 control the line-by-line switch generator 6 and a half-line generator 9 which in turn controls half-line switches 8. -Instead of suppressing the chrominance signals for half of each line, the whole picture may be produced by the chrominance signals only, so that a colourfree black and white picture is formed when the receiver is correctly adjusted, or chrominance only for one or two colours and chrominance and luminance for the remaining colour or colours. The switches 3, 4 and 5 may be operated by a frame-by-frame generator instead of a line-by-line generator such as 6, or alternatively each line may be divided into separate parts, or groups of lines may be taken together, for example a colour change every three lines, the necessary condition being that each line, group of lines, or part of a line is a different colour on successive scans. The sequential transmission of the colour information gives a black and white picture frequency of one-third of the normal picture frequency or one-half if two primary colours are transmitted on one scan and the third on the following scan.