GB432485A - Improvements in and relating to television and the like systems employing cathode ray tubes - Google Patents

Abstract

432,485. Cathode-ray tubes ; television. BLUMLEIN, A. D., 7, Courtfield Gardens, Ealing, London. Dec. 29, 1933, No. 36653. [Classes 39 (i) and 40 (iii)] To allow multiple-spot scanning in a television &c. cathode-ray tube, several electron beams are separately modulated in intensity and are focused on to the screen as spots close together along a straight line parallel to the scanning' lines of the image. When the phase relationships between the modulations are correctly controlled, the images due to the several spots are superposed to form a single, bright image. Fine, parallel wires 11.. 15, Fig. 1, or flattened rods extend across a rectangular aperture in, and are insulated from, a screen 16 in front of a rectilinear cathode 5 perpendicular to the wires. The negative bias on the parts 11 .. 16 is such that no electrons pass until control impulses are applied to one or more of the wires 11 .. 15 when an electron beam emerges past each such wire and is focused on to the screen 4 by positive cylinders 17, 18. The beams from the wires form closely adjacent spots on the screen and the control impulses are applied to the wires through a phase-retarding network, Fig. 2, comprising series inductances L, shunt condensers 24.. 31, 33 and a resistance 32, the cut-off frequency of the network being above the highest frequency in the television receiver. To compensate for the effect of the potential of one control wire on the electron flow past adjacent wires, compensating potentials are superposed on the control potentials on adjacent wires by a delay network or the waveform of the control potentials are modified by delay networks. The spots may be produced by separate electrode systems. In another arrangement, Fig. 3, (not shown), the tube has an elongated equipotential cathode, a cathode-screen, an accelerator, a modulator, a first anode and a wall silvering forming a second anode ; the electrodes are slotted and the modulator contains insulated and screened control electrodes.