GB1478970A - Beam indexing television display apparatus - Google Patents

Abstract

1478970 Television NATIONAL - RESEARCH DEVELOPMENT CORP 19 July 1974 [1 Aug 1973] 36493/73 Heading H4F The electrically conductive index strips of a beam indexing cathode-ray tube 68 form a plurality of sets, the index strips of each set being connected together and the sets having their index strips interleaved with one another, the sets of strips being connected to means (such as the primary of a transformer 36) to form a tuned circuit, the output from which is used to generate a synchronizing signal to control the application of signals to the cathode-ray tube. Two sets of index strips may be used. A stereoscopic picture may be produced by cathode-ray tube 68 in response to signals from two laterally spaced television cameras, a series of vertical cylindrical lenses being placed in front of the screen of the cathode-ray tube 68. Alternatively, as specifically described, a colour picture may be reproduced using vertical (for horizontal line scanning) coloured phosphor strips separated by guard bands (18, Fig. 1, not shown), or a white phosphor and coloured filters. In the embodiment shown in Fig. 5 for a colour display using two sets of index strips and red, green, blue phosphor strips the width of each index strip equals the width of four phosphor strips. The output signal of the tuned circuit at frequency fi is passed via a band-pass filter 74 and Schmitt trigger 75 to a balanced modulator 78 directly and via a frequency divide-by-three circuit 80, the output of balanced modulator 78 at frequency 4/3 fi being separated by a band-pass filter 82. The output of band-pass filter 82 is connected to both inputs of a balanced modulator 84 to derive a signal at frequency 8/3 fi which is the desired synchronizing signal which is fed to balanced modulator 86 and via a phase shifter 88 to a balanced modulator 90 which receive R-Y and B-Y signals respectively and supply output signals to an adder 92 the output of which is fed via a luminance adder 94 to the cathode-ray tube 68. To control the phase of operation of the frequency divide-by-three circuit 80 at the start of each line scan four additional index strips each three times as wide as each ordinary index strip are provided at the start of each line scan, which generate a signal at a frequency fi/3 which is separated by a band-pass filter 76 and via Schmitt trigger 77 and gate 130 controls the phase of operation of circuit 80.