U.S. Philips Corporation

Ronald W Gill

Alan G Knapp

Derek Washington

Daphne L Lamport

Alfred W Woodhead

In order to reduce contrast degradation in an electrostatically scanned flat cathode ray tube having a channel plate electron multiplier, due to back-scattered electrons entering channels remote from their origin, a coating of a material having a low back-scatter coefficient is applied over the input of the electron multiplier between the apertures therein. The surface texture of the material should be microscopically rough. The material can be applied to the first dynode or to an electrode electrically and physically connected to the first dynode. The acceptance angle of the channel plate electron multiplier may also be restricted.

Cathode ray tube with means for preventing backscatter from electron

In order to reduce contrast degradation in an electrostatically scanned flat cathode ray tube having a channel plate electron multiplier due to back-scattered electrons entering channels remote from their origin, steps are taken to restrict the acceptance angle of the channel plate electron multiplier. In one arrangement means are provided on the input surface to restrict the angle of entry to a range normally associated with the addressing electron beam. In another arrangement the ready emission of secondary electrons is restricted to a predetermined arcuate portion of the input of each channel of the electron multiplier. In either arrangement stray electrons are unable to impinge upon the secondary emitting material in the channels and in consequence produce many fewer back-scattered electrons. Optionally a material having a low back-scatter coefficient and a microscopically rough surface texture may be applied to the exposed surfaces, apart from the apertures, of the input side of the electron multiplier to reduce the number of back-scattered electrons.

Growing community of inventors

Crawley, United Kingdom

Ronald W Gill