GB776878A - Improvements in or relating to colour television systems - Google Patents

Abstract

776,878. Television. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Sept. 29, 1954 [Oct. 2, 1953], No. 28092/54. Class 40 (3). In a line sequential colour television system employing three primary colours only two colours are employed during each frame, one of the colours appearing in all frames and the other two colours appearing in alternate frames. Fig. 1 shows a transmitter embodying the invention in which signals representative of the green primary colour are utilized in all frames, these signals being generated by a pick-up tube 2 and an associated colour filter whilst the other two colour signals (Red and Blue) are generated by means of a pick-up tube 4 and an associated rotating (Red and Blue) colour filter 7. The outputs from tubes 2 and 4 are then fed to a circuit 11 which, under the control of line synchronizing signals from 13, alternately supplies the two sets of colour signals to a transmitter 12 to which are also supplied the usual line and frame synchronizing signals from generators 13 and 14, and additional synchronizing signals from generators 15 and 16, the former serving to reverse the colour order periodically (to reduce " colour-crawl ") and the latter serving to effect synchronous operation between the rotating colour filter 7 and a trigger circuit (equivalent to circuit 11) at a co-operating receiver. Fig. 2 shows one embodiment of a suitable receiver in which the picture signals derived from 17 are supplied to a trigger circuit 19 controlled by means of received line synchronizing signals to supply the green signals to gun 21 of a three-gun colour tube 18 and the red and blue signals to a gate circuit 24<SP>1</SP>, the circuit 19 being also controlled in phase by a device 20 to which the signals from generator 16 (Fig. 1) are supplied. The gate circuit 24<SP>1</SP> is then controlled by means of frame synchronizing signals and a trigger circuit 24 (controlled in phase by a device 25 to which the signals from generator 16, Fig. 1, are supplied) to supply the red and blue signals alternately to guns 22 and 23 of tube 18. In a second embodiment of a receiver suitable for co-operating with the transmitter of Fig. 1 a single gun colour picture reproducing tube provided with a colour switching grid is employed (Fig. 3, not shown). Fig. 4 shows a further embodiment of a receiver in which a trigger circuit 19 (similar to 19, Fig. 2) supplies the green signals to a " green " picture reproducing tube 30 and the red and blue signals alternately to a picture tube 31 in front of which a red and blue colour filter 32 is rotated and maintained in synchronism with the rotation of filter 7 (Fig. 1) by means of a synchronous motor 33 controlled by the signals from generator 16 (Fig. 1). The images produced by the two tubes are then combined by optical means to form a composite image.