KR790001242B1 - Television apparatus respondent to the transmitted color reference signal - Google Patents

Abstract

A device making it possible to use the reference signal applied within the period of vertical blanking of transmitted television waveforms to improve the regenerated color concentration, consisted of a device for generating and demodulating the color difference signal, a locking device of color synchronizing burst frequency and oscillating signal frequency and a device responding to the reference signal and controlling its phase for compensating the color saturation rate.

Description

Television device responsive to transmitted color reference signal

1 is a complete waveform diagram within the vertical blanking period of a transmitted television waveform.

2 is a schematic diagram showing circuitry used to transmit a reference signal with a standard color television broadcast signal.

3 is a schematic diagram showing an apparatus responsive to a reference signal for automatic color and saturation correction in a television receiver to improve the quality and density of the reproduced color image.

FIELD OF THE INVENTION The present invention relates to color television receivers, and more particularly to an apparatus that enables the use of a reference signal embedded within the vertical blanking period of a transmitted television waveform to improve the concentration of reproduced color.

As described below, the device constructed by the present invention is intended to respond to a reference signal inserted within a vertical blanking period for automatic color and saturation correction. For color control, the reference signal is reproduced on the receiver to control the phase of the sub-carrier oscillator, while the transmitted color burst signal is reproduced to lock the oscillator at a frequency. Used. Since the reference signal has a much longer duration than the burst signal, the phase fluctuation caused by a phenomenon such as standing wave or multipath is substantially less. Using a reference signal instead of the burst signal provides more accurate control of the oscillator's phase and improved color demodulation. On the other hand, using a burst that periodically recursively adjusts the oscillation frequency separately, the response speed and signal-to-noise ratio represented by the typical phase and frequency control circuits used to set the oscillator as a reference for the burst signal stage to demodulate. Provide the same response speed and signal-to-band cost.

For saturation control, one embodiment of practicing the principles of the present invention is similar to conventional designs that generate an automatic chromaticity control signal to set the chromatic channel gain. However, instead of following a representative device using the color burst as a reference to maintain a constant chromaticity level, it will be appreciated that the device described above operates on the pedestal of the reproduced reference signal acting as a comparison device. . By comparing this with one of the color matrix amplifiers of the receiver, for example, and selecting this criterion of brightness amplitude, any variation in contrast control fixation will result in an overall adjustment in chromatic gain and corresponding variation in reference amplitude. Thus, automatic tracking between the chromaticity and lightness channels will be automatic. Also, such as focusing on the reference as a reference in maintaining chromatic gain instead of color burst amplitude, reduces the aforementioned disturbances in stabilizing the amplitude of the chromatic signal according to the cumulative tolerance for the burst signal. Let's do it.

The gains and other gains described so far of the present invention will be described with reference to the drawings.

1 shows a selected waveform of a color reference signal embedded in a transmission waveform, for example, at line 20 of each television field vertical blanking period. The line period in FIG. 1 is from T ₁ to T ₂ and has a typical horizontal deflection sync pulse A with 40 IRE units amplitude in the negative direction at the start of the line. The pulse A is followed by a color carrier (3.579547 MHZ) and a synchronous burst B of-(BY) phase. The burst signal B, with the peak-to-peak amplitude of the 40 IRE unit, overlaps with the burst and horizontal sync pulses at the blanking reference C to form part of the conventional color television signal, which need not be described further.

The remaining line periods are followed by a first burst D of several cycles of low frequency (e.g., 0.5 MHz) followed by a second burst E of the same amplitude except for a sub-carrier frequency of a predetermined-(R-Y) phase. The second burst, i.e., the reference signal E, is used in the apparatus for implementing the principles of the present invention. This burst E is superimposed on the peak amplitude of the burst which is about 44 IRE units on the basis of the brightness of the 50 IRE unit amplitude. This second burst amplitude selection is achieved when the gain of the chromaticity channel for a signal in the-(RY) phase is 1.14, and automatic chromaticity adjustment is achieved by this factor with a brightness level of 50 IRE units (after demodulation). After being increased it can be obtained by comparison with the amplitude of the second reference burst E. The peak amplitude for subcarrier burst E of the (-R-Y) phase will generally be 25IRE units because the receiver gain for the subcarrier phase is about 2.03. By inserting a low-frequency burst D (optionally determined), it is easy to use gating of the reference burst E from the synthesized signal, and between the maximum information that can be transmitted in the shortest time and Q needed to separate the reference signal. You are at a compromised frequency.

The color reference signal E of the present invention can be inserted in a vertical period at almost any position between the camera and the receiver during broadcast communication, but in the arrangement of FIG. In FIG. 2, the conventional color television camera 11 simultaneously shows the output terminals of the color image signals of red "R", green "G" and blue "B", which are properly designed color flexors 13 Is applied to the input terminal of. This color flexor unit receives color image signals simultaneously from the synchronization generator 15 with the synchronization and blanking signals, and generates brightness and chroma signals through the operation of a suitable modulation and matrix circuit. Brightness and chromaticity signals supplied by color flexor 13 are applied via transmission line 17 to the transmission facility indicated by block 19. The color reference signal generator, which provides a waveform of the type shown in FIG. 1, is indicated by block 21 in FIG. 2. The output signal of the generator is added to the composite broadcast signal on input wire 17 of the transmitting facility. Reference signal generator 21 receives vertical and horizontal drive pulses from sync generator 15 along with a color sub-carrier wave at its input. The sub-carrier wave is sub-carrier wave to the color flexor device to ensure a locked relationship between the color reference signal burst of the vertical blanking period and the back porch partial color television signal sync burst of the horizontal pulse. It will be driven from the same source that supplies it.

The transmitting facility, indicated by block 19, may use any of the common signaling connection facilities normally used in commercial broadcasting systems. In this system, the receiver 23 reproduces the image broadcast from the synthesized signal applied to the input terminal of the receiver via a transmission facility, and the color and saturation degree are described by the apparatus of the present invention which will be described later in the image display apparatus of the receiver. The corrected image will be played.

The apparatus of FIG. 3 shows an R-Y and B-Y low level demodulation system with 90 ° phase separation between the sub-carrier signals from the reference oscillator 50 of the receiver to the R-Y and B-Y demodulators 52, 54. The output signals from these demodulators are respectively applied to a pair of matrix and amplification circuits 56 (red) and 58 (blue), respectively, for mixing with the brightness, i.e., Y signal, applied as an additional input at the first image stage of the receiver. do. The output signals from the matrix circuits 56, 58 are applied to a suitable electrode of the cathode ray kinescope (not shown) to form a full color reproduced image with the green signal reproduced from the red and blue information. As pointed out, the composite video signal is transmitted to the respective demodulation circuits 52 and 54 via the chromatic amplification system 62 which sets the frequency according to the chromaticity channel at the input terminal 60.

According to the present invention, the synchronous burst portion of the synthesized signal (B in Fig. 1) is used to lock the frequency, not the phase of the reference oscillator 50. In this respect, the apparatus embodying the principles of the present invention is distinguished from the apparatus using a conventional method. For this purpose, the composite video signal applied to the terminal 60 is subjected to the burst amplifier 64 keyed by the deflection of the receiver and the gate pulse supplied from the high voltage circuit to separate the color synchronous burst B from the synthesized waveform. Connected. Separated bursts are applied to the reference oscillator 50 by a relatively large coupling capacitor 66 to lock the frequency of the oscillator at the frequency of the received burst signal. Since this burst is transmitted at a rate of once for every television line, this capacitive coupling acts as a short circuit for that burst and is delivered rapidly to lock the oscillator 50 at a suitable frequency. This periodic recurring burst thus switches between channels a response rate, such as that of known NTSC and PAL receiver systems, whose color synchronous bursts are used to further lock the phase of the reference sub-carrier oscillator. When you give it to the device. As will be explained soon, this alternating coupling of the synchronous bursts to the oscillator 50 has substantially little effect of the steady state phase of the oscillation as controlled by the direct current voltage of the oscillator reactance device. However, according to the invention, this control for the reactance device is affected by the reference signal (E in FIG. 1) transmitted in combination with the direct current of this reactance control.

This phase locking of the oscillator 50 to achieve the color control of the present invention is obtained by sampling the output of the B-Y demodulator 54 during the vertical blanking period in which the color reference signal is inserted. Since the color reference signal is inserted above-(R-Y), the output of demodulator 54 should be nominally zero when the reference signal phase and oscillator phase are equal. If there is any difference between these two phases, the correction voltage will develop to adjust the oscillator phase until the detected B-Y component becomes zero, with the oscillator phase lying along the R-Y axis.

This automatic phase control operation is accomplished by the use of a gate and clamp circuit 68 connected to receive the output of the B-Y demodulator 54 after amplification of the amplifying unit 70 first within the apparatus of FIG. The control of the gate 68 is in turn controlled by the second operating circuits associated with the phase control: amplitude detector 72, delay circuit 74 and coincidence gate 76. In particular, these units 72-76 couple the amplitude detector 72 to receive the advanced signal output of the chromatic amplitude system 62, and are also suitable in response to the applied vertical sync non-pulse in accordance with the timed pulse to match the blanking position. It works together to provide a clamp pulse during the vertical blanking period in which the color reference signal is inserted by applying its own output to coincident gate 76 which appears to be line period. The output of gate circuit 68 will be a direct current coupled to the reactance device of oscillator 50, and control the oscillator phase for the color reference signals E to reduce the detected B-Y component to zero. This control is independent of the phase of the color synchronous burst B as described.

This use of the color reference signal to produce the color of the reproduced color image provides a significant improvement in the known NTSC design, since the reference signal lasts much longer than the color synchronous burst, resulting in much less phase shift error. to be. Thus, when the reference signal occupies about 24 μsec, the periodic and multipath states will have a 2.5 μsec delay, and only 0.1 radian phase shift will attempt to be represented by a wide range of chromaticity information. Such displays have the same delay and are substantially affected if the 2.5 microsecond burst itself is used to provide phase control.

However, if such a burst signal is used to individually lock the frequency of the receiver's sub-carrier oscillator, it not only maintains a speed consistent with the operating response speed, but also exceeds the signal-to-noise ratio caused when the reference signal is used only for color correction. It is beneficial because it improves. This is because the synchronous burst periodically recurs every television line compared to the color reference signal, which exists one at every television feed. This single use of the reference signal to correct the color of the reproduced image is described in Wilhelmy's U.S. Patent No. 3456068, which demonstrates the inconvenience of late response and the bad signal-to-noise ratio by the simultaneous use of the color synchronous bursts described herein. Improve.

The apparatus of FIG. 3 further refines the structure presented by the aforementioned patent for a facility that additionally uses the same color reference signal to control the saturation of the reproduced color display. For this purpose there is included a second gate and clamp unit 78 having a first input coupled to sense the output of the red matrix amplifier 56 and a second input controlled by a clamp pulse generated by the combined operation of units 72-76. do. Since there is a B-Y demodulator 54 for phase control, the output of matrix 56 would ideally be zero during the blanking period embedded in the reference signal. The reason for this is that the reference signal in the (RY) phase and the reference burst are superimposed on the reference point with the same amplitude as the brightness signal so that the output of the RY demodulator 52 has the same polarity and opposite polarity as that of the brightness component of the composite video signal. Because it has. As shown, with such components applied from the demodulator 52 to the matrix amplifier 56, the gate and clamp unit 78 provides an automatic chromaticity control signal such that any output from the non-zero matrix amplifier 56 is applied to the chroma amplifier 62 to determine the chroma channel gain. Will convert to.

Instead of focusing the energy components of the color synchronous bursts as a method of generating these control signals, if the reference of the color reference signal is used as a measurement, the cumulative error related to the burst amplitude adversely affects the automatic gain control of the chromatic amplifier. Many of the difficulties that arise in conventional designs are eliminated. The second benefit of using the color reference signal of the type described in providing saturation control is achieved by realizing the adjustment of the contrast control of the receiver, and the correction voltage of the matching polarity will be achieved by adjusting the chromatic gain in the same way. Thus, automatic tracking is performed without the need for any common coupling operation between the controls used and the brightness and chromaticity of the receiver.

Passive saturation control is included in the apparatus of FIG. 3 using phase divider 80 coupled to the output of coincident gate 76. The variable output tap 81 is adjusted to generate positive or negative pulses in a timely manner in synchronizing with and driving from the color reference signal. These pulses can infer an error signal of the type described in connection with the matrix amplifier 56, and can also change the chromatic gain in a suitable way in the automatic chromatic adjustment circuit when the pulse is coupled to the amplification system 62 by lead 82. .

Burst amplifier 64 and reference oscillator 50 are additionally connected to phase detector 84 to generate a control voltage as shown, and when the control voltage is applied to chroma amplifier 62 via color killer amplifier 86, the chroma channel is stopped. In the black and white water phase, the color "noise" of the screen will be removed from the cathode kinescope. Each unit shown in FIG. 3 is an easily available device or ones which can be easily assembled by those skilled in the art.

So far, one embodiment of the present invention has been described and it will be readily understood that various modifications may be made without departing from the spirit and scope of the invention. In other words, although the color reference signal has been described as the-(R-Y) phase, it will be appreciated that the-(B-Y) phase may also be used by applying the gist of the present invention. It will be appreciated that in this variant, an automatic phase control (APC) signal for color correction is generated in response to the output of the R-Y demodulator 52 instead of the B-Y demodulator 54. It should also be noted that an auto color control (ACC) signal for saturation correction is generated in response to the output of blue matrix 58 instead of red matrix 56.

This use of the vertical reference signal in order to improve the density and quality of the color reproduction reproduced on the receiver is more recent than recently announced by the Broadcast Television Systems Committee of the Electronic Industries Association. It is a step forward. There, although the color reference guarantee signal is inserted within the vertical blanking period to reduce the error of reproduced hue and saturation, this signal is used to adjust the phase and amplitude of the transmitted chroma signal among the signals combined with the other signals. To be used, a signal must be transmitted that matches the signal originating in the imaging system where the corrected amplitude and phase of the composite signal are established. As can be readily seen, this phenomenon in multiple paths causes transmission line reflection and differential phase error to cause confusion in the receiver in this relationship of transmission. Although this use of the vertical period reference signal (VIR) can greatly reduce these characteristics of the television studio and circuit operation that adversely affects color and body diagram, the device implementing the principles of the present invention provides such assurance. It is a step forward in that these reference signals are useful in offsetting many disturbances in transmission that reduce the advantages in other ways.

Claims (1)

Receiving a television signal comprising a brightness component, a chromatic component modulated in both phase and amplitude, a color synchronous burst that occupies the horizontal retrace period, and a component that periodically recurses the color reference signal occupied during the vertical retrace period A color television receiver suitable for a first type comprising: a first device for generating a color difference signal containing information proportional to the color and saturation of a transmitted image and for providing a signal for demodulating the chromaticity component, and the frequency of the color synchronizer burst; A second device responsive to color synchronous bursts by coupling the bust to the first device to lock at least the frequency of the oscillation signal at and adjusting the phase of the oscillation signal as a function of the phase of the reference signal. Generating a control signal to the first device to respond to the color reference signal. A television device that constitutes a third device to answer.

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