GB518811A - Improved methods of obtaining coloured images - Google Patents

Abstract

518,811. Colour television. HEWSON, B. T., and LOCAN, A. May 30, 1938, No. 3584/40. Divided out of 518,761. [Class 40 (iii)] [Also in Group XX] In colour television, there are arranged both in front of the television camera and between the cathode-ray oscillograph and the viewing screen light polarizing means and a relatively rotatable optical or electrooptical colour filter device, relative rotation being effected between the light polarising means and the colour filter device between successive images, the two devices (including the polarizing means) being accurately located in the same relative relationship and being synchronously operated. As shown, an electrooptical colour filter device comprises a mount 40, polarizing and analysing prisms or lenses 41, lenses 42, a Kerr cell 43, the voltage on which is controllable by means of a rheostat, and a crystal plate 44 cut to pass only polarized light of a certain wavelength. The crystal plate 44 is rotated intermittently or otherwise from image to image by a gear 80. In a modification the polarizer and analyser may also be rotated, but at a different speed to the crystal plate. In another modification the Kerr cell is omitted, and a composite crystal plate formed of a mosaic of differently cut crystals is employed. Specification 518,761 is referred to.