Patent GB-552367-A (GB)
Title: Improvements in electro-optical systems for the transmission and reproduction of multi-coloured originals such as coloured photographs
IPC: H04N1/60
Filed: 1941-06-26
Abstract: 552,367. Copying in colour by scanning ; modulating light. KODAK, Ltd. (Eastman Kodak Co.). June 26, 1941, No. 8034. Addition to 538,012. [Class 40 (iii)] Relates to electro-optical systems for the reproduction and transmission of a coloured original image comprising a plurality of photoelectric devices 11B, 11G, Fig. 1, adapted to receive light signals obtained by scanning the original in a plurality of colours each device receiving the light signal corresponding to one component colour and converting it into an electric signal in an electric channel for controlling a corresponding light modulation device. Systems of this kind are described in the parent Specification and Specifications 488,835* and 538,013. According to the invention, the system comprises in combination, an exponential amplifier in at least one of the electric channels and at least one combined light modulator for modulating one and the same light beam in dependence on the electric signals of at least two of the channels. The applications and effects of this combination are described at length in the Specification. As shown in Fig. 1, a green signal is transmitted from photo-electric device 11G through channel 12G (linear-amplifier), 40G (band-pass filter), 13G (exponential-amplifier), 14G (linear-amplifier), 41G (linear-rectifier), 42G (lowpass filter)) to a green light-modulator 43G. A blue signal is transmitted by a similar channel to a blue light-modulator 43B. In addition, in accordance with the invention, another channel 44G (exponential amplifier), 45G (linear-rectifier), 46G (low-pass filter), 47G (amplifier) transmits the green signal from amplier 12G to a light-modulator 48G for the same light beam controlled by the blue light-modulator 43B. This third channel may in addition be connected as indicated by the dotted lines 50 to the blue channel for adding its effect in the control of the light-modulator 43B as described in the parent Specification. As shown in Fig. 1, the light-modulator 43B is a light valve controlled by the blue signal and the light-modulator 48G is a glow lamp controlled by the green signal, but these controls may be reversed, the glow-lamp being controlled by the blue signal and the valve by the green signal. Also both light-modulators may be light-valves. For example, as shown in Fig. 2, two ribbon light-valves 63, 67 are provided at right-angles to each other. Light from a lamp 60 is focused at 64 on the first light-valve, the spot 64 is focused at 68 on the second light-valve 67, and the spot 68 is focused on the scanning drum 70. In a modification the ribbon light-valves are both at a single focal point. In another modification, Fig. 3, the two ribbon light-valves 63, 67 are parallel to each other, the light from lamp 60 is focused at 64 on the first-light valve 63, the second light-valve is placed close to the lens 72 which focuses the spot 64 on the lens 73 which focuses the spot 68 of the second light-valve 67 on the drum 70. In this arrangement, a third light-valve 78 may be added at right-angles to the other and situated close to the lens 73.