GB752871A - Improvements in and relating to optical apparatus - Google Patents

Abstract

752,871. Television. BERWICK DEVELOPMENTS, Ltd. Feb. 6, 1953 [Feb. 12, 1952; April 21, 1952], Nos. 3688/52 and 9974/52. Class 40 (3). [Also in Group XX] A filter for use in conjunction with a monochrome image, such as a television image on the screen of a cathode-ray tube, in order to render the image more attractive by the addition of colour, comprises a transparent body providing a colour pattern composed of minute, discrete, differently coloured areas the integrated optical effect of which is a much larger pattern distributed irregularly over the filter area. In one construction, Fig. 1, the filter is composed of an assembly of three transparent sheets 10, 11 and 12 coloured respectively blue, yellow and red and each perforated with a pattern of holes as shown in Fig. 3. The filter is completed by a transparent base 14 and cover 16. The coloured sheets are assembled with the rows of holes inclined at small angles whereby the filter presents a. mosaic of differently coloured areas the integrated optical effect of which is a much larger pattern but one which is irregular due to departures from regularity in the perforations. In an alternative construction, Fig. 5 (not shown), the filter is combined with a uniformly coloured base formed of a thin cell containing a dyed liquid. Once a filter has been produced as described it may be reproduced by means of a colour photographic process to give a colour transparency. The filter may be suspended in front of the cathoderay tube screen, for which purpose straps 18 carrying hooks are provided. Alternatively, light coloured by the filter may be thrown on to the front or rear of the screen by a projector.