GB759063A - Improvements in or relating to optical systems for relating colour component images - Google Patents

Abstract

759,063. Optical systems. TECHNICOLOR MOTION PICTURE CORPORATION. Feb. 8, 1954, No. 3608/54. Class 97 (1). In a beam light dividing or combining system having a surface at which an incident beam is divided into component beams for colour photography or television or component beams are combined, the surface is framed by coating a transparent body with an optical interference coating which reflects some light of one of the colours and transmits the remainder of that light and the remaining colours, the layers being chosen so that the amount so reflected is such as, having regard to the sensitivities of the emulsions, or the intensity of the projecting beams, as to provide a colour balance between the beams. Fig. 4 shows a beam splitting system for' use in photography comprising prisms P5, P6, P7 and P8 cemented together as shown with interference coatings Db and Dr therebetween and photographic emulsions Sb, Sg and Sr respectively arranged for recording the blue, green and red images framed by a lens L. It is supposed that the emulsion Sg is less sensitive than Sr which is itself less sensitive than Sb. To balance these differences of sensitivity the layers Db and Dr are formed by the superposition of layers of alternately high and low refractive index such as zinc sulphide and lead fluoride, are designed to transmit all the incident green light and also so much of the red and blue light as is necessary to ensure that the red and blue light respectively reflected to the emulsions Sr and Sb will produce the same effect thereon as does the green light on the emulsion -Sg. Filters Fb, Fg and Fr are provided to ensure such equalization. In the alternative the blue light may be transmitted and the red and green light reflected by the coatings. The invention may be applied to a prism having only one surface effecting the light division as described in Specification 382,239, one of the beams, either the reflected or transmitted beam, being incident on a single film and the other being incident on a bipack film. Suitable filters being provided to ensure the recording of the three colour components. The invention may also be applied to a beam splitter of the type described in Specification 475,808 and shown in Fig. 11 when the two light-dividing coatings Db and Dg are cemented between triangular prisms for framing, at the desired intensities, the red, green and blue images R, G and B. Alternatively, the prism P12 and coating Dg may be omitted and the coating Db framed for the recording of twocolour images on a film placed at Sbg. The system may also be used for framing three component images for colour television. Specification 716,332 also is referred to.