GB1206865A - System and apparatus for converting colour television signals of the sequential type into signals of the simultaneous type - Google Patents

Abstract

1,206,865. Colour television. COMPAGNIE FRANCAISE THOMSON HOUSTON - HOTCHKISS - BRANDT. 19 April, 1968 [19 April, 1967], No. 18739/68. Heading H4F. Colour television signals of the field or frame sequential type comprising sequential red, blue and green signals forming monochrome fields or frames are converted to signals of the simultaneous type having the same field or frame frequency by storing at least two of the monochrome video signals during their production and then reproducing them in synchronism with the third, which may also be stored or may be produced directly without storage. Apparatus for carrying out this method comprises a magnetic record disc 1 revolving once during every field or frame period and having three concentric tracks 2R, 2B, 2V on to which red, blue and green elementary signals R, B, V from a sequential camera 3 are respectively sequentially recorded by recording devices 5R, 5B, 5V controlled by an electronic switch 4. Each track also has a continuously operating reading head 6R, 6B, 6V and an erasing head 8R, 8B, 8V, a switch 9 causing erasing signals each lasting for one field frame period to be applied successively to the three erasing heads. During each field or frame period one of the tracks 2 receives a signal from the corresponding recording device 5, the previous monochrome signal of the same colour being erased by the corresponding head 8. The remaining two tracks store the other two monochrome signals, and all three signals stored at any given time are simultaneously read out by the heads 6R, 6B, 6V. The switches 4, 9 produce the necessary cycling of recording and erasing across the three tracks. In an alternative arrangement only one recording track is provided, having only a single recording head and erasing head, but with three reading heads accurately sited at 120 degrees to each other. Magnetic tape may also be used for storage. In applying the invention to an interlaced line scanning system each track of the illustrated record disc 1 may be provided with a supplementary recording head or reading head spaced angularly from the first such head 5 or 6 by an amount corresponding to half a line interval. If supplementary recording heads are provided the switch 4 switches successive signals of any particular colour alternately to the main head and to the supplementary head. Alternatively a half-line interval delay line may be switched into the input or output connections in such a sequence as to produce the same effect. In another form the disc 1 may have six tracks, with one set of three tracks being used for even fields and the other set being used for odd fields.