| 摘要 |
1,223,278. Colour television. R.C.A. CORPORATION. 16 Oct., 1968 [18 Oct., 1967], No. 48980/68. Heading H4F. A colour television system comprising transmitting apparatus in which the green G component of an image is picked-up and transmitted continuously while the red R and blue B components are picked-up in separate tubes 12 and 13 respectively and caused to alternate at line frequency, the two resultant signals containing G and (R + B) information being transmitted as separate channels, and receiving apparatus in which the two channels are separated, the (R + B) channel being delayed for the duration of one line, the delayed and undelayed portions of the signal being combined in a switch such that separate red, blue and green components are obtained. The R and B camera tubes 12, 13 are cut-off on alternate lines by pulses 25 and 26, derived from an oscillator 21, which are applied to the cathodes 18 and 19 thereof in order to produce red and blue outputs 28 and 29 at the input to an adder 31. Here the two signals are combined to produce a wave train as at 32. Marker pulses 41 are also added at 31 from waveform 73 in order that the receiver may distinguish between red and blue information. The order of alternation of R and B is itself alternated in alternate frames by means of an inhibiting pulse applied to a counter 24 by a counter 42 to cause counter 24 to advance or retard by one pulse after each frame. Further, the lines of alternate frames, red then blue, are raised or lowered in such a manner that the lines of each of the two fields in each frame are closer together. This is illustrated in Fig. 5 (not shown). The signal at 32 is modulated on to a sub-carrier at 33 and one sideband is suppressed at 35. The green signal at 27 is then added to the resultant (R + B) signal at 36 and passed to the modulating and other stages of the transmitter such that the green signal occupies a band of approximately 0 to 4 MHz and the (R + B) signal occupies approximately 4 to 8 MHz. The frequency spectrum of the transmitted signal is illustrated in Fig. 2 (not shown). At the receiver, shown in Fig. 3, the two channels are separated by means of filters 45 and 47, the channel containing green information being passed to one gun of a tri-gun cathode-ray tube 67. The signal containing (R + B) information is delayed by one line at 51, the delayed and undelayed signal being combined in an electronic switch 52 so as to form red only and blue only signals at the outputs 64 and 61 of the switch. The switch is actuated by means of pulses from a generator 54 which produces two wavetrains 55 and 56 of oppositely phased pulses to operate each section of the switch separately. Generator 54 is synchronized to the transmitter output by means of the marker pulses 41 which are detected at 53. Fig. 4 (not shown) illustrates an electronic switch suitable for use with this invention. |
