GB882866A - Improvements in or relating to cathode-ray devices - Google Patents

Abstract

882,866. Colour television tubes. MULLARD Ltd. Nov. 7, 1958 [Nov. 27, 1957], No. 36993/57. Class 39(1) [Also in Group XL(b)] A cathode ray tube has an elongated luminescent screen comprising a multi-colour oneline pattern Tb, Tg, Tr, Fig. 1, and a white strip W substantially parallel thereto. In operation a line time base circuit TB is provided for moving the point of impact of an electron beam along the length of the screen to effect line scanning, and means are also provided for effecting displacements of the point of impact in a direction transverse to the length of the screen, these displacements including cyclical displacements for selecting the colours in a sequential manner and also a continuous displacement of the beam from the colour pattern to the white strip. Thus in conjunction with a mechanical frame scan system e.g. as described in Specifications 827,851, 846,544 and 865,665 the tube may be used for "black-and-white" or colour television displays. Preferably two transverse deflection systems are provided, one system Dt1 for causing high frequency spotwobble across the multi-colour pattern to effect dot-sequential scanning and the other Dt2 for deflecting the beam on to the white strip and, if desired, for applying to the spot a uniform drift at frame frequency during monochrome display to reduce the loading of the white phosphor. When this circuit is used in a television receiver adapted to receive signals in accordance with a colour transmission system of the kind employing a sub-carrier to convey the colour information, it may include means for controlling automatically the mode of operation of the transverse displacement means in response to the presence or absence of the sub-carrier. The tube may be of conventional shape or may be of the kind described in Specifications 865,663, 865,666, 880,477 and 881,152. In the latter case the phosphor strips Tb, Tg, Tr, W, Fig. 3, may be slightly tapered and set at a small angle to one another. The colour spot-wobble and switching from colour to white may be applied near the target by means such as tensioned deflection wires or strips extending along the full length of the target. A spare target system may be provided on the screen.