Patent GB-1360697-A (GB)
IPC: H04N9/093
Filed: 1972-09-06
Abstract: 1360697 Colour television ROBERT BOSCH FERNSEHANLAGEN GmbH 6 Sept 1972 [7 Sept 1971] 41357/72 Heading H4F Registration errors in a colour television camera are reduced by producing correction signals for the red (R) pick-up tube and then the blue (B) pick-up tube to bring them into registration with a third pick-up tube which generates a higher resolution video signal, e.g. a white (W) or green (G) signal. Pulses bare produced from the white signal and the red (or blue) signal when their amplitude lies within a given range (e.g. u to o, Fig. 2a). Pulses c are produced from pulses b in converters 6 and 7 having a duration equal to a picture element for horizontal correction, or a duration equal to a line period for vertical correction (H/V switch 16 selects which correction is being effected). Pulses d and e are produced from pulses c by means of monostable circuits 8, 9, 11 and 12, the pulses d which are derived from the white signal being twice the duration of the pulses e derived from the red (or blue) signal. Pulses f and g (or g<SP>1</SP> when registration is incorrect) are produced respectively in response to the trailing edges of pulses d and e by means of monostable circuits 13, 14, 17 and 18, these pulses having a duration equal to pulses d. The g or g<SP>1</SP> pulses are then subtracted from the f and d in difference amplifiers 21 and 19 respectively and the positive components of the resulting k or k<SP>1</SP> pulses are added 22 to the negative components of the resulting h or h<SP>1</SP> pulses to produce pulses I when there is no registration error and pulses m when registration error is present. These pulses I or m are integrated in low pass circuit 23 and the resulting control voltage (zero for pulses l) is stored in a correction store 24. This store 24 is controlled by the programme transmitter 4 to ensure that the control voltage is fed to the appropriate part of the store in dependence upon whether the red or blue signal is being evaluated, and upon whether vertical or horizontal information from 9, 17 and 13 or from 11, 14 and 18 is being evaluated. The store 24 controls various adjustable correction devices to adjust different parameters of the geometries of the red and blue pick-up tubes to achieve registration. Analyser 2 which enables a switch 3 determines whether the signal b derived from the input video a is sharp (e.g. has a steep flank) and predominantly neutral and not indistinct and predominantly coloured which could cause faulty adjustment. For either the red or blue signals adjustment of the position of the frame in the horizontal direction is effected by evaluating the central vertical one third of the frame, adjustment of the size of the frame in the horizontal direction is effected by evaluating the right hand vertical one third of the frame, and adjustment of the linearity of the frame in the horizontal direction is effected (after further adjustment of the position has been effected by evaluating the left hand vertical one third of the frame) by evaluating the central vertical one third of the frame. Similar adjustments in the vertical direction are effected during vertical deflection of a pulse which sweeps respectively over the central, lower and upper thirds of the frame.