Patent GB-750103-A (GB)
Title: Improvements in transmission of colored motion pictures
IPC: H04N9/11
Filed: 1953-10-05
Abstract: 750,103. Television. TECHNICOLOR MOTION PICTURE CORPORATION. Oct. 5, 1953 [Nov. 22, 1952], No. 27241/53. Class 40 (3). In an arrangement for generating electric signals representative of the different colour aspects (red, green, blue) of a kinematographic colour film, a further film carrying in register the different colour aspects is prepared in coloured media which for at least one colour aspect absorb light of a spectral range different from that of the respective original aspect and may in addition absorb light in a range which is at least part complementary to that of the respective original, this further film being scanned by a "flying-spot" scanner, the light from which contains the spectral ranges absorbed by the different media and the photoelectric cells co-operating with which have a maximum response in these respective ranges. By this means lack of fidelity due to lack of co-ordination between the spectral ranges of the scanning light beam, the spectral ranges absorbed by the different colour aspect dyes (&c.) employed in the film and the spectral ranges of the photo-electric cells and co-operating colour selective beam splitting devices and colour filters, which would occur if a conventional colour film were employed, is avoided. Fig. 1 shows the general arrangement in which the further film P is scanned by light produced by a "flying-spot" cathode-ray tube T, the light transmitted through the film being split up into separate beams of different spectral ranges by means of colour selective devices SRU and SG and directed on to photo-electric cells DRU, DG and DB via filters FRU, FG and FB respectively, the signals developed by cells being amplified at A and employed in conventional manner. In accordance with the invention, one of the colour aspects of the original, in the particular case considered the red aspect, is printed on the multilayer film P in a dye which is light-absorbent in a different spectral range, in this case in the ultra-violet range, and further, in accordance with the invention, the light produced by the tube T is arranged (by the selection of suitable phosphors) to include ultra-violet in addition to the spectral ranges absorbed by the dyes in which the blue and green aspects are printed on film P. This is illustrated in Fig. 1 where t shows the spectral range of the light produced by tube T and p shows the substractive absorption ranges y (yellow), m (magenta) and c (cyan) corresponding to the blue, green and red colour aspects whilst at s and d respectively are shown the spectral responses of the colour selective devices SRU and SG and the photo-electric cells DRU, DG and DB. By this means the difficulties associated with electro-optical devices in the red region of the spectrum are avoided and additionally, since the tube phosphors need not have significant red light emissions, phosphors of very short persistence times may be employed in the " flying-spot " scanning tube. According to a further feature of the invention the film P may be made suitable for conventional motion picture projections by producing the red aspect in a visually satisfactory absorption range such as minus red (cyan) in addition to its production in the ultraviolet range, the latter having no effect on the direct optical projection of the film and the former having no effect when the film is employed for the generation of television signals. In addition to printing the red aspect in a different spectral range the blue and green aspects may also be printed in other (different) spectral ranges independently of the natural colour of the original scene or image and narrow spectral bands can be selected to match the most effective regions common to all elements of the modulation channel. Details of the production of suitable films by conventional photographic processes are described with reference to Figs. 2-6 (not shown).