Patent GB-1333067-A (GB)
Title: System for receiving monochrome and colour television signals
IPC: H04N13/00
Filed: 1970-05-07
Abstract: 1333067 Colour television system UNIVERSITATEA DIN BUCURESTI 7 May 1970 [1 Aug 1969] 21972/70 Heading H4F An arrangement for receiving monochrome and colour television signals comprises a monochrome C.R.T. display to which a colour C.R.T. display, including a chromatic raster of parallel phosphor stripes, is connected via a decoder by means of a cable including a selector switch operable to render operative the monochrome or colour display. In the embodiment described the monochrome and colour signals correspond respectively to a stereoscopic pair of images derived by two objectives from an object, and by displaying these signals on the colour display (which has monochrome and colour phosphor stripes) and viewing via a raster of parallel halfcylindrical lens a stereoscopic colour image is produced. A stereoscopic colour system which is employed in the above arrangement comprises at the transmitter an adapter 14, Fig. 1, mounted in front of a camera tube 15, including two objectives 16 and 17 which project a stereoscopic pair of images of an object 1 on to a "stereochrome" filter 18 which includes a half-cylindrical lens raster and a striped filter raster. A light source 21 may be provided and the filter 18 may be placed directly on the tube 15. One of the resulting interlaced images formed on the lens raster passes through the orange-red stripes (R) and the blue-green stripes (BV), while the other image passes through monochrome stripes (N) and transparent stripes (S). The resulting dot sequential type signal from camera 15 (the lens and filter rasters being perpendicular to the camera line scan direction) is switched, 24, in response to pulses corresponding to the transparent stripes so that the orange-red (R), the blue-green (BV) and monochrome (N) pulses are passed to their respective channels. At the receiver the pulses are arranged to sequentially modulate a single scanning electron beam of a display tube 25, the timing of the colour sequence being controlled by index signals derived from a stereochrome filter 26 disposed in front of the tube. Filter 26 comprises two glass plates 27 and 28, the chromatic raster being printed on plate 27 with a transparent stripe between each group of R, BV and N stripes, and plate 28 being formed as a lens raster. In addition parallel leads are embedded in grooves in the plates 27 and 28 behind the transparent stripes, the leads in plate 28 being covered with a photo-emissive layer, electrons being emitted therefrom and attracted to the leads in plate 27 in response to the scanning beam of tube 25. The capacitor 29 is thus sequentially discharged through resistor 30 and the resulting pulses fed via amplifier 31 to control switch 32. Alternatively the index pulses may be derived from photodiodes o<SP>r</SP> phototransistors disposed in alignment with the transparent stripes (5). Instead of only one of the stereoscopic images being in colour, both may be in colour, the stereochrome filter having red, green and blue vertical stripes. Alternatively the filter may have horizontally disposed orange-red and bluegreen stripes, field sequential (stereoscopic) colour signals being transmitted. In this latter case the stereochrome filter at the receiver may have light-amplifying properties, the colour stripes comprising a grid of parallel metal wires coated with electroluminescent phosphor disposed adjacent a photo-conductive layer between two glass plates, and an alternating voltage being applied selectively between the wires being scanned (i.e. the orange-red or blue-green coated wires) and a translucent metal layer on the photoconductive layer. The filter may alternatively comprise a chromatic raster of horizontal or vertical electroluminescent phosphor stripes and a photoconductive layer between translucent metal layers to which an alternating voltage is applied. Luminous markers may be provided on the edge of the filters to enable the receivers filter to be correctly positioned with respect to the transmitters filter. The transmitter may include a monochrome tube for one of the stereoscopic images and two or three tubes for the other stereoscopic image, dichroic filters being employed. The signals may be transmitted in accordance to the NTSC, PAL or SECAM (Trade Mark) system and at the receiver decoded to form suitable signals for display. Instead of using a single beam display tube as described above a three-beam "Trinitron" (Trade Mark) type tube may be employed, and if sequential signals are received they are converted to simultaneous signals by a tapped delay line.