GB732238A - Improvements in colour television voltage control system - Google Patents

Abstract

732,238. Colour television tubes. CHROMATIC TELEVISION LABORATORIES, Inc. May 26, 1952 [May 24, 1951], No. 13311/52. Drawings to Specification. Class 39 (1). [Also in Group XL (b)] In a colour television cathode-ray tube comprising a screen bearing one colour phosphor and a grating in front of the screen made up of electrically separate elements bearing further colour phosphors, a set of equal and opposite voltage pulses are applied simultaneously to the elements of the grating, voltages on adjacent elements being of opposite polarity, and then a corresponding second set of voltage pulses of opposite polarities to those of the first set are applied to the elements of the grating. The electron beam is thus selectively deflected to elements of the grating while at the same time preventing stray electrons from falling on other elements of the grating and so avoiding colour contamination. Simultaneously to prevent stray electrons falling on the screen, the accelerating voltage of the tube may be reduced. When the electron beam is to excite the screen a negative voltage pulse is applied to the grating and a positive voltage pulse to the screen. Suitable circuits for feeding the voltage pulses to the tube are described (see Group XL (b)). Specification 721,199 is referred to.