Television apparatus responsive to a transmitted color reference signal

Abstract

A color reference signal is inserted during the vertical blanking interval of a transmitted television waveform, for utilization by The described apparatus in automatically setting the hue and saturation of the display of an NTSC or PAL receiver. The apparatus responds to the transmitted burst signal to lock the frequency of the sub-carrier oscillator of the Receiver and to the transmitted reference signal to adjust the phase of its oscillations.

What is claimed is: 
     
       1. In a color television receiver adapted to receive a television signal including a luminance component, a chrominance component modulated in both phase and amplitude, periodically recurring color synchronizing bursts occupying prescribed intervals during the horizontal retrace portions of said signal and a color reference signal .Iadd.fully .Iaddend.occupying a prescribed interval during the vertical retrace portion of said signal, apparatus comprising: first means for providing an oscillatory signal to demodulate said chrominance component .[.and produce color difference signals containing information proportional to the hue and saturation of the televised scene.].   .Iadd.second means including at least first and second chrominance signal demodulators responsive to said oscillatory signal, and also responsive to said television signal, for demodulating said chrominance component and producing color difference signal outputs representative of the hue and saturation of the televised scene, said reference signal being in quadrature phase relationship with respect to the demodulation axis associated with said first demodulator.Iaddend.;   .[.second.]. .Iadd.third .Iaddend.means responsive to said television signal for recovering the color synchronizing bursts thereof and for coupling said bursts to said first means to lock at least the frequency of the oscillatory signal provided thereby to the frequency of such bursts; and   .[.third.]. .Iadd.fourth .Iaddend.means, also responsive to said television signal, for recovering said color reference signal and for utilizing said signal to develop a control signal for said first means to adjust the phase of said oscillatory signal as a function of said reference signal.Iadd., said fourth means comprising the combination of (a) a frequency selective amplifier for delivering said chrominance and color reference signal components of said television signal to said demodulators, (b) said first demodulator, and (c) means for sensing the output of said first demodulator during the occurrence of said reference signal and deriving said control signal therefrom.Iaddend.;   whereby the degree of error in the hue of a reproduced color image attributable to such transmission characteristics as multipath, transmission line reflection and the like is correspondingly reduced.[...].   .Iadd.wherein there is additionally included fifth means, responsive to said delivery of said color reference signal to said second demodulator via said amplifier, for controlling the amplitude of said color difference signals and the saturation of the reproduced color image as a function of departures of the amplitude of said delivered reference signal from a reference level responsive to the luminance component level exhibited during said prescribed interval. .Iaddend.   
     
     
       2. .[.The apparatus of claim 1.]. .Iadd.In a color television receiver adapted to receive a television signal including a luminance component, a chrominance component modulated in both phase and amplitude, periodically recurring color synchronizing bursts occupying prescribed intervals during the horizontal retrace portions of said signal and a color reference signal occupying a prescribed interval during the vertical retrace portion of said signal, apparatus comprising: first means for providing an oscillatory signal to demodulate said chrominance component;   second means including at least first and second chrominance signal demodulators responsive to said oscillatory signal, and also responsive to said television signal, for demodulating said chrominance component and producing color difference signal outputs representative of the hue and saturation of the televised scene, said reference signal being in quadrature phase relationship with respect to the demodulation axis associated with said first demodulator;   third means responsive to said television signal for recovering the color synchronizing bursts thereof and for coupling said bursts to said first means to lock at least the frequency of the oscillatory signal provided thereby to the frequency of such bursts; and   fourth means also responsive to said television signal, for recovering said color reference signal and for utilizing said signal to develop a control signal for said first means to adjust the phase of said oscillatory signal as a function of said reference signal, said fourth means comprising the combination of (a) a frequency selective amplifier for delivering said chrominance and color reference signal components of said television signal to said demodulators, (b) said first demodulator, and (c) means for sensing the output of said first demodulator during the occurrence of said reference signal and deriving said control signal therefrom;   whereby the degree of error in the hue of a reproduced color image attributable to such transmission characteristics as multipath, transmission line reflection and the like is correspondingly reduced; and   wherein there is additionally included fifth means, responsive to said delivery of said color reference signal to said second demodulator via said amplifier, for controlling the amplitude of said color difference signals and the saturation of the reproduced color image as a function of departures of the amplitude of said delivered reference signal from a reference level responsive to the luminance component level exhibited during said prescribed interval; and .Iaddend.wherein .[.there is additionally included fourth means for coupling the chrominance component of said television signal for demodulation with said oscillatory signal to produce said color difference signals, and wherein fifth means is also included to respond to corresponding coupling of said color reference signal via said fourth means to control the amplitude of said color difference signals and the saturation of the reproduced color image as a function of the amplitude of said reference signal.]. .Iadd.said fifth means includes means for matrixing the output of said second demodulator with said luminance component, means responsive to the output of said matrixing means during said color reference signal occurrence for developing a gain control voltage, and means for utilizing said gain control voltage to control the gain of said amplifier .Iaddend..   
     
     
       3. The apparatus of claim 2 wherein .[.sixth.]. .Iadd.seventh .Iaddend.means is also included, coupled to said first, .[.second.]. .Iadd.third .Iaddend.and fourth means, respectively, and responsive to the presence of said provided oscillatory signal and to said recovered color synchronizing bursts to disable said fourth .[.means.]. .Iadd.amplifier .Iaddend.during the monochrome transmission of a televised scene and in the absence of said synchronizing bursts. .[.4. The apparatus of claim 2 wherein said second means couples the recovered color synchronizing bursts to said first means to lock the frequency of said oscillatory signal to the frequency of said synchronizing bursts and wherein said third means couples said control signal to said first means to lock the phase of said 
     
     
        oscillatory signal to the phase of said color reference signal..]. 5. The apparatus of claim 4 wherein said .[.first.]. .Iadd.sixth .Iaddend.means .[.includes a reactance control device responsive to alternating current signals to regulate the frequency of said provided oscillatory signals and to direct current signals to regulate the phase of said oscillatory signals, wherein said second means alternating current couples the recovered color synchronizing burst to said reactance control device and wherein said third means direct current couples said control signal to said reactance device.]. .Iadd.comprises means for modifying one of the signal inputs to said matrixing means, said signal input modifying means including a potentiometer with a tap subject to manual adjustment of its position to control the modification of said one signal input in such manner that the existence, magnitude and sense of said simulated saturation error is dependent upon the position of adjustment of said 
     
     
        tap.Iaddend.. 6. The apparatus of claim 5 for use in a color television receiver providing color difference signals along R-Y and B-Y demodulation axes and operative with a television signal including said color reference signal at --(R-Y) phase, wherein said .[.third means includes.]. .Iadd.sensing .Iaddend.means .[.for monitoring.]. .Iadd.monitors .Iaddend.the amplitude of the color difference signals provided along said B-Y demodulation axis and .[.to develop.]. .Iadd.develops .Iaddend.said control signal for said first means to adjust the phase of said oscillatory signal to reduce the amplitude of said B-Y color difference signal .Iadd.output during said color reference signal occurrence .Iaddend.in a direction to automatically compensate for transmission characteristic changes as would adversely affect the hue of the reproduced 
     
     
        color image. 7. The apparatus of claim 5 for use in a color television receiver providing color difference signals along B-Y and R-Y demodulation axes and operative with a television signal including said color reference signal at --(B-Y) phase, wherein said .[.third means includes.]. .Iadd.sensing .Iaddend.means .[.for monitoring.]. .Iadd.monitors .Iaddend.the amplitude of the color difference signals provided along said R-Y demodulation axis and .[.to develop.]. .Iadd.develops .Iaddend.said control signal for said first means to adjust the phase of said oscillatory signal to reduce the amplitude of said R-Y color difference signal .Iadd.output during said color reference signal occurrence .Iaddend.in a direction to automatically compensate for transmission characteristic changes as would adversely affect the hue of the reproduced 
     
     
        color image. 8. The apparatus of claim 6 wherein said .[.fifth means includes means for monitoring the amplitude of the color difference signal provided.]. .Iadd.second demodulator effects demodulation .Iaddend.along said R-Y demodulation axis .[.and to develop said control signal for said fourth means to adjust the gain thereof to reduce the amplitude of said R-Y color difference signal in a direction to automatically compensate for transmission characteristic changes as would adversely affect the 
     
     
        saturation of the reproduced color image.].. 9. The apparatus of claim .[.6.]. .Iadd.7 .Iaddend.wherein said .[.fifth means includes means for monitoring the amplitude of the color difference signal provided.]. .Iadd.second demodulator effects demodulation .Iaddend.along said B-Y demodulation axis .[.and to develop said control signal for said fourth means to adjust the gain thereof to reduce the amplitude of said B-Y color difference signal in a direction to automatically compensate for transmission characteristic changes as would adversely affect the saturation of the reproduced color image.].. .Iadd.10. The apparatus of claim 2 also including sixth means for selectively causing said matrixing means to provide an output during said prescribed interval which is inclusive of a component simulating a saturation error of controllable magnitude and sense so as to effect a desired modification of the saturation of a color reproduction of said televised scene effected in response to said color difference signals and said luminance component. .Iaddend. .Iadd.11. In a color television receiver adapted to receive a television signal including a luminance component, a chrominance component comprising a color subcarrier modulated in both phase and amplitude, periodically recurring color synchronizing bursts occupying prescribed intervals during the horizontal retrace portions of said signal and a color reference signal, of color subcarrier frequency and of a reference phase and amplitude, occupying prescribed interval during the vertical retrace portion of said signal, apparatus comprising: first means for providing an oscillatory signal to demodulate said chrominance component and produce color difference signals containing information proportional to the hue and saturation of the televised scene;   second means responsive to said television signal for recovering the color synchronizing bursts therefrom and for coupling said bursts to said first means to lock at least the frequency of the oscillatory signal provided thereby to the frequency of such bursts;   third means, also responsive to said television signal, for recovering said color reference signal and for utilizing said signal to develop a control signal for said first means; said third means comprising (a) an amplifier for said chrominance and color reference signal components of said television signal, (b) a first chrominance component demodulator responsive to respective outputs of said first means and said amplifier and effecting demodulation of said modulated color subcarrier along a demodulation axis in quadrature relationship to said reference phase to develop a first color difference signal, and (c) means for sensing the output of said first demodulator during said prescribed vertical retrace interval for developing said control signal for said first means to adjust the phase of said oscillatory signal as a function of the phase of said reference signal; and   fourth means responsive to respective outputs of said first means and said amplifier for controlling the amplitude of said color difference signals and the saturation of the reproduced color image via adjustment of the gain of said amplifier as a function of the amplitude, with respect to a reference level, of said amplified reference signal; said fourth means comprising a second chrominance component demodulator responsive to outputs of said first means and said amplifier and effecting demodulation of said modulated color subcarrier along a second demodulation axis in quadrature relationship to said first demodulation axis to develop a second color difference signal, means for matrixing the output of said second demodulator with said luminance component, means responsive to the output of said matrixing means during said prescribed vertical retrace interval for developing a gain control voltage, and means for utilizing said gain control voltage to control the gain of said amplifier; said reference level being responsive to the level of said luminance component supplied to said matrixing means during said prescribed vertical retrace interval; and   wherein the color-difference signals developed by said first and second demodulators in response to said chrominance component are utilized in development of a color reproduction of said televised scene. .Iaddend. .Iadd.12. Apparatus in accordance with claim 11 also including fifth means for selectively causing said matrixing means to provide an output during said prescribed vertical retrace interval which is inclusive of a component simulating a saturation error of controllable magnitude and sense so as to effect a desired modification of the saturation of said   
     
     
        color reproduction of said televised scene. .Iaddend. .Iadd.13.  Apparatus in accordance with claim 12 wherein said fifth means comprises means for modifying one of the signal inputs to said matrixing means, said signal input modifying means including a potentiometer with a tap subject to manual adjustment of its position to control the modification of said one signal input in such manner that the existence, magnitude and sense of said simulated saturation error is dependent upon the position of adjustment of said tap. .Iaddend. .Iadd.14. In a color television receiver adapted to receive a television signal including a luminance component having a given level representative of black, a chrominance component comprising a color subcarrier modulated in both phase and amplitude, periodically recurring color synchronizing bursts occupying prescribed intervals during the horizontal retrace portions of said signal and a color reference signal, of color subcarrier frequency and of a reference phase and amplitude, occupying a prescribed interval during the vertical retrace portion of said signal and superimposed upon a pedestal shifted in the white direction from said black representative level, apparatus comprising: first means for providing an oscillatory signal to demodulate said chrominance component and produce color difference signals containing information proportional to the hue and saturation of the televised scene;   second means responsive to said television signal for recovering the color synchronizing bursts therefrom and for coupling said bursts to said first means to lock at least the frequency of the oscillatory signal provided thereby to the frequency of such bursts;   third means, also responsive to said television signal, for recovering said color reference signal and for utilizing said signal to develop a control signal for said first means; said third means comprising the combination of (a) a frequency selective amplifier for amplifying the chrominance and color reference signal components of said television signal, (b) a first chrominance component demodulator responsive to respective outputs of said first means and said amplifier and effecting demodulation of said modulated color subcarrier along a demodulation axis in quadrature relationship to said reference phase to develop a first color difference signal, and (c) means for sensing the output of said first demodulator during said prescribed vertical retrace interval for developing said control signal for said first means to adjust the phase of said oscillatory signal as a function of the phase of said reference signal;   a second chrominance component demodulator responsive to respective outputs of said first means and said amplifier and effecting demodulation of said modulated color subcarrier along a second demodulation axis in quadrature relationship to said first demodulation axis to develop a second color-difference signal;   means for matrixing the output of said second demodulator with a signal which is representative of said pedestal during said prescribed vertical retrace interval;   means responsive to the output of said matrixing means during said prescribed vertical retrace interval for developing a gain control voltage; and   means for utilizing said gain control voltage to control the gain of said amplifier;   wherein the color-difference signals developed by said first and second demodulators in response to said chrominance component are utilized in development of a color reproduction of said televised scene. .Iaddend.