GB470653A - Improvements in optical systems for colour photography - Google Patents

Abstract

470,653. Colour kinematography. HARRISON, W. H., and HARRISON, E. C. March 16, 1936, No. 7806. Convention date, March 20, 1935. [Class 97 (i)] A light-dividing system comprises a transparent plate having part of its rear surface semi-reflecting and part of its front face full reflecting so that light transmitted through the part of the front face which is not reflecting will be partially reflected to the full reflecting portion of the front face and thence emerge from the plate ; a system of colour filters may be so arranged with respect to the plate and the film as to prevent the formation of "ghost " images. As shown in Fig. 1, light from the object 21 is partially reflected at the semi-reflecting surface 17 of the plate 16, one beam R passing directly to the film 11 and the other beam U being reflected to a different area of the film by the full-reflecting inclined face 18 of the plate. Colour filters 19, 20 respectively red and green are placed adjacent the plate, and corresponding filters 12R, 13G respectively red and green are placed adjacent the film so that light from the beams R or G which falls on the filters 13G or 12R is absorbed thereby and does not reach the film. For three-colour photography a parallel-sided plate may be used and the beam divided by two internal reflections instead of one, each divided beam being focused on the film by a separate lens through a filter system similar to that shown in Fig. 1. The resultant positive film may be projected by an apparatus similar to that used for taking, the light-dividing system being used to superimpose the images on the screen, the arrangement of filters preventing any colour-fringing. According to the Specification as open to inspection under Sect. 91 the dividing system may comprise two parallel plates 16, 17, Fig. 5 (Cancelled) held apart by suitable means, the upper portion b<1>-c<1> of the plate 16 being full reflecting and the lower portion a-b of plate 17 being semi-reflecting so that separate images of the object 21 are produced on the film 11 by the lenses 26, 27. A green filter 20 placed between the plates 16, 17, and a red filter 19, are provided, corresponding filters 13, 12 being placed adjacent the film. In a modification the dividing means may comprise only the portions a-b and b<1>-c<1> of the plates supported alone. It is also stated that the described arrangement of filters may be employed with any suitable light-dividing system either for photography or for projection. This subjectmatter does not appear in the Specification as accepted.