Patent GB-663176-A (GB)
Title: Improvements in or relating to method and means for photographic color separation
IPC: G03B27/72
Filed: 1948-06-30
Abstract: 663,176. Making photographic colour separation negatives. HUEBNER, W. C. June 30, 1948 [July 18, 1947], No. 17660/48. Classes 98 (i) and 98 (ii). ' A method of producing colour separation negatives from coloured copy wherein the copy is successively photographed while illuminated by a number of separate colours, comprises illuminating the copy by projecting thereon a narrow band of light of the required colour for one of the negatives, the band having a length at least equal to one dimension of the copy and a width a fraction of the other dimension of the copy, causing the light band to illuminate successively the entire area of the copy by effecting relative movement between the copy and the light band in a direction transverse to the light band while simultaneously photographically recording the illuminated area of the copy, and then similarly successively illuminating the copy with light bands of like dimensions and of the colours required for the other negatives while photographically recording the copy upon a different negative for each different colour. The light bands may be interrupted in timed relationship with the relative movement so that narrow areas of the copy are successively illuminated by flashes of coloured light. Illuminating means for carrying out the above method include an elongated source of substantially white light in an enclosure having an elongated opening of adjustable width, an elongated spectrum producing member, supported adjacent to the opening to separate the light therefrom into its component colours, within an enclosure having an elongated aperture which is adjustable in width so that a narrow band of light of preselected colour may pass therethrough on to the surface of the copy, and means to effect relative movement between the copy and the light band so that the copy is scanned by the light band. Two such illuminating means may project light bands on the copy in superposed relationship, the wavelength of the light in the bands increasing in opposite directions. As shown, Fig. 1, the lighting means are suspended from overhead rails 11 from which other carriers for other components of a photographic copying camera also depend, and are independently movable along the rails. A bar 15 is attached by brackets to carriages 12 riding on rails 11, and carriages 14 riding on bar 15 support downwardly-extending frame members 17 connected by a spacing bar 16 at their lower ends. A bar 26 is movable vertically on carriages 25 riding on frame members 17, and supports an assembly comprising two lamp housings 20, 21. An electric motor 24 mounted on this assembly drives, through a worm gear, a shaft 29 journalled in bearings 30 on bar 26 and carrying pinions 31 engaging racks 32 on frame members 17, thereby causing vertical movement of the lamp assembly. Cables 35 attached to the assembly pass over pulleys 37 and are attached to counterweights, not shown. Each lamp housing contains a tubular electric discharge lamp 41, Fig. 3, which produces a light flash when connected to a source of electric potential. The emitted light is limited by adjustable plates 49 and passes through a dispersing prism 47, is again limited by adjustable plates 69, and falls on a narrow strip 19 of the copy 18. Prism 47 is mounted between blocks 55 rotatable by knobs 56 (see also Fig. 1) and mounted on two pairs of plates movable vertically and horizontally. Prism 47 may, therefore, be adjusted so that the strip 19 can be illuminated by a band of light of any desired narrow range of wavelengths. Strip 19 is illuminated by lamps in the two housings 20, 21, light from one having inverse order of wavelength with respect to the other. As the lamp assembly moves across the copy, a commutator 40 on the shaft 29, wiped by a contact 39, completes a circuit at intervals causing both lamps to flash simultaneously or alternately so that the copy is illuminated a strip at a time and is completely scanned as the lamp assembly moves across it. The lightsensitive surface is exposed throughout the movement by the camera lens 75 to record a colour component negative. The Specification as open to inspection under Sect. 91 comprises also a modification wherein each housing prism 47 is omitted, and light from lamp 41 passes through a colour filter before being directed on to the strip 19. This subject-matter does not appear in the Specification as accepted.