JPH0530543A - Video signal processor - Google Patents

Abstract

PURPOSE:To monitor the variation of the whole processing system and to attain always effective and stable color reproduction in respect to a video signal processor such as a color television receiver. CONSTITUTION:A superimposing part 11 superimposes a test signal for gain control and DC reproducing control to a video signal during the flyback time of the video signal. A detection part 14 detects the test signal from a signal impressed to a cathode and a signal detection part 15 compares the detected test signal with a reference level and generates a gain control signal and a DC reproducing control signal. A control part 12 suppresses the gain of the video signal and the variation of a DC reproducing value based upon the two control signal. Thereby contrast, drive, brightness, and bias can be simultaneously controlled and white balance in each gradation can be always accurately held.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing circuit in a video signal processing device such as a color television receiver or the like.

[0002]

2. Description of the Related Art As a conventional video signal processing device, there is, for example, a structure shown in FIG. In FIG. 16, 21
Is a contrast / brightness control unit, 22 is a superimposing unit for superimposing a test signal in the blanking period of the video signal, 23 is an output circuit for controlling the amplitude of the video signal and performing DC reproduction, and outputting a CRT drive signal, and 24 is the CRT. A detection unit for detecting the test signal in the blanking period from the drive signal, and a control signal generation unit 25 for generating a signal for controlling the gain and the DC reproduction value of the output circuit 23 from the detected test signal.

The operation of the conventional video signal processing apparatus configured as described above will be described. In the contrast / brightness control unit 21, contrast control as shown in FIG. 11 is performed by amplifying the amplitude of the AC component of the video signal of FIG. 11A as shown in FIG. As shown in FIG. 11C, the control means
This is performed by increasing or decreasing the DC component with respect to the pedestal level of the video signal in (a). These two types of control are G, B, R
The contrast and brightness are controlled by uniformly amplifying the amplitude and increasing / decreasing the direct current component for each video signal. In the superimposing unit 22, for example, as shown in FIG. 17, a black level test signal having an amplitude of 25% of the maximum output amplitude and a white level having an amplitude of 75% of the maximum output amplitude during the blanking period of each of the G, B and R video signals. The test signal is superimposed. The output circuit 23 amplifies the amplitude of the video signal according to the gain control signal from the control signal generator 25, receives the DC reproduction control signal from the control signal generator 25, and clamps the black level test signal. The detector 24 detects the black level test signal and the white level test signal from the blanking period of the CRT drive signal. The control signal generator 25 compares the black level detected by the detector 24 with the bias voltage of the reference level, and outputs the difference voltage to the output circuit 23 as a DC reproduction control signal.
The control signal generator 25 compares the white level detected by the detector 24 with the drive voltage of the reference level, and outputs the output circuit 2
The gain control signal is generated so that the gain of 3 becomes a specified value. That is, when the white level detected by the detection unit 24 is higher than the drive voltage, a signal that lowers the gain of the output circuit 23 is output, and when the white level detected by the detection unit 24 is lower than the drive voltage, the gain of the output circuit 23 is increased. Generating a signal.

As described above, by constructing a feedback loop so that the black level and white level test signals superposed during the blanking period coincide with the reference signal, the fluctuation of the CRT drive signal is suppressed and a stable video signal is obtained. It is a processing circuit.

[0005]

However, in the above configuration, only the output circuit 23 is monitored and stabilized for gain control. Therefore, when the characteristic of the contrast / brightness control unit 21 changes and its gain changes in each of the G, B, and R circuits, the CRT drive signal output from the output circuit 23 also changes in each of the G, B, and R signals. It will be. As a result, there is a problem in that the brightness of the output image changes and the hue changes.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a video signal processing apparatus which monitors the fluctuation of the entire processing system and maintains a good and stable white balance without causing a hue change.

[0007]

In order to achieve the above object, a video signal processing apparatus of the present invention comprises a generating means for generating a test signal for controlling gain and brightness, and a test signal for converting the test signal into a video signal. Superimposing means for superimposing, control means for controlling the gain and brightness of the video signal on which the test signal is superposed by this superimposing means, and a video signal controlled by this control means for amplifying and outputting to the display device. Output means, detection means for detecting a test signal superimposed on an output signal of the output means, and a control signal for controlling the control means by comparing the test signal detected by the detection means with a reference signal The control means controls the gain and brightness of the video signal by the control signal generated by the signal generation means.

[0008]

The present invention has the above-mentioned configuration,
Since the brightness adjustment is provided as a test signal in the blanking period by the generating means, the amplitude and DC voltage value at the cathode of this test signal are detected by comparing with the reference signal by the signal generating means to detect the video signal. The contrast, brightness, drive, and bias are controlled simultaneously by monitoring with a feedback loop to the control means for controlling the gain and the brightness, and the entire video signal processing system including the characteristics of the CRT is stabilized to ensure accurate brightness and hue. A reproduced image can be realized.

[0009]

1 is a block diagram of a video signal processing apparatus according to a first embodiment of the present invention. As shown in FIG. 1, as its constituent elements, 11 is a superimposing section as a superimposing means for superimposing a test signal in a blanking period of a video signal, and 13 is an output as an output means for generating a CRT drive signal. Reference numeral 14 is a circuit, and 14 is a detecting section as a detecting means for detecting the test signal from the drive signal of the CRT. 15 is a signal generating means for comparing the detected test signal with a reference voltage to generate a control signal for controlling a video signal. , 12 is a control unit as a control unit for performing gain control and DC reproduction of the video signal by the control signal from the signal generation unit 15, and 16 is a test signal superimposed by the superimposing unit 11 and a test is performed by the detecting unit 14. The generator is a generator that generates a sample timing signal for detecting the signal.

The operation of the video signal processing apparatus of this embodiment constructed as described above will be described below.

In the generator 16, for example, a CT whose amplitude changes with a contrast volume as shown in FIG.
BRP whose amplitude changes with the volume of P and brightness
Of the test signal, the switch control signal for superimposing the test signal on the video signal as shown in FIG. 2B, and the detection unit 14 as shown in FIGS. 2C and 2D. A sample timing signal for detecting this test signal and a pedestal sample timing signal as shown in FIG. 2 (e) are generated. CTP is a reference test signal for monitoring the amplitude gain of the video signal,
BRP is a reference test signal for monitoring DC reproduction of the video signal. After that, these two test signals are respectively C
Notated as TP and BRP.

Next, the operation of the superposing section 11 will be described in detail with reference to FIG. In FIG. 3, 111 is a video signal clamp circuit that clamps the pedestal level of the video signal, 112 is a switch circuit that switches between a test signal and a video signal, 11
Reference numeral 3 is a test signal clamp circuit for clamping the LOW level of the test signal.

The video signal clamp circuit 111 clamps the pedestal level and the test signal clamp circuit 113 clamps the LOW level to fix the pedestal level and the LOW level to the same level. Then, the video signal and the test signal are input to the switch circuit 112. The switch circuit 112 switches between the video signal and the test signal according to the switch control signal shown in FIG. As shown in FIG. 2F, the output of the switch circuit 112 becomes a signal in which the test signal is superimposed during the blanking period of the video signal. The CTP and BRP test signals are G, B,
It is equally superimposed on the blanking period of each R video signal. In the following description, the video signal refers to the output signal of the superposing unit 11.

The video signal that has passed through the control unit 12 and the output circuit 13 is detected by the detection unit 14 as CTP and BRP of the test signal. A configuration example of the detection unit 14 is shown in FIG. In FIG. 4, reference numeral 141 denotes a level shift circuit for setting a large-amplitude video signal applied to the CRT to an amplitude according to the detection of the test signal, 14
Reference numerals 2, 143, and 144 denote sample-hold circuits for detecting the pedestal level of the video signal, the CTP peak value level, and the BRP peak value level, respectively, in accordance with the timings shown in FIGS. It is a subtracter that calculates the output difference of the circuits 142 and 143. The level shift circuit 141 steps down the video signal to a voltage suitable for processing the large-amplitude CRT drive video signal by the sample hold circuits 142, 143, 144, and outputs it. The sample and hold circuit 144 samples and holds the voltage of the peak value level of BRP in order to monitor the DC reproduction value of the video signal, and outputs the value to the signal generator 15.
The sample and hold circuits 142 and 143 sample and hold the pedestal level of the video signal and the voltage of the peak value level of CTP, and output the values to the subtractor 145.
The subtractor 145 calculates the difference between the voltage of the peak value level of CTP and the pedestal level, and outputs the amplitude voltage value of CTP in order to monitor the amplitude gain of the video signal.

The signal generator 15 compares the signal detected by the detector 14 with a reference voltage and generates a control signal for the controller 12. The configuration of the signal generator 15 is shown in FIG. In FIG. 5, 151 and 152 are comparators. The comparator 151 detects the CTP amplitude detection value V1 detected by the detector 14 and the reference voltage VD.
To generate a gain control signal. As the control signal, for example, a signal for decreasing the gain is generated if V1> VD, and a signal for increasing the gain is generated if V1 <VD, and the control unit 12 is controlled so that V1 = VD eventually holds. The comparator 152 compares the voltage V2 of the peak value level of BRP detected by the detector 14 with the reference voltage VB and outputs the differential voltage for clamping as a DC reproduction control signal. The controller 12, the output circuit 13, Detection unit 14,
The comparator 152 constitutes a so-called feedback clamp circuit.

The control unit 12 is constructed as shown in FIG. Figure 6
In the figure, 121 is a gain control circuit for amplifying the output signal from the superimposing section 11, and 122 is a direct current reproduction control circuit for performing direct current reproduction of the video signal. The DC regeneration control circuit 122 receives the DC regeneration control signal from the comparator 152 and clamps the peak level of BRP to a prescribed value. Gain control circuit 121
Controls the CTP of the test signal to a specified amplitude according to the gain control signal from the comparator 151. Since the control covers the entire video signal, the signal in the effective scanning period is also controlled to have the specified gain as a result. At this time, the other test signal, BRP, is also modulated with the specified gain.

Next, the method of adjusting the drive and bias will be described. The characteristics of a CRT are generally not uniform among G, B, and R, and the relationship between the input signal and the brightness of the output screen is different as shown in FIG. 7. Therefore, even if the same signal is input, the brightness of the image is G , B, and R are different. Therefore, in order to make the brightness of the output image uniform, it is necessary to adjust the gain and DC reproduction value of the video signal system to be different for G, B, and R as shown in FIG. This adjustment is drive and bias adjustment.

Next, a drive adjusting method will be described first. The gain G of the control unit 12 and the output circuit 13 is CT
When the amplitude of P is VC and the reference voltage is VD, the following equation (Equation 1) is obtained.

[0019]

[Equation 1]

That is, to change the amplitude of the video signal, V
Either change C or VD. Drive adjustment is G,
The amplitude of each of the B and R video signals must be set individually. If VC is used for drive adjustment, the generator 16 must prepare three types of test signals CTP for superimposition for G, B, and R, and the circuit scale becomes large and complicated. In comparison, VD is simply a DC voltage, and it is easy to prepare three types for G, B, and R. Therefore, VD may be used as the drive adjustment voltage. The same applies to bias adjustment. Bias adjustment must be clamped to different DC regeneration values for G, B, and R, but BRP
It is possible to simplify the circuit by preparing three types of reference voltage VB as the bias voltage, rather than making the peak value (amplitude) of G, B, and R different values.

Next, the principle of adjusting contrast and brightness will be described. First, the principle of contrast adjustment will be described. Contrast needs to similarly change the amplitude of each of the G, B, and R video signals. The amplitude of the video signal that drives the CRT is controlled by the gain G of (Equation 1), but even if the drive voltage VD is different for G, B, and R, G, B, and R
, The rate of change of gain due to a uniform change of VC is G,
It is obvious from (Equation 1) that B and R are the same. Therefore, the CTP that is equally superimposed on the G, B, and R video signals
The amplitude of each of the G, B, and R video signals can be changed in the same manner by changing the amplitude VC of the above, and the contrast can be adjusted.

Next, the adjustment of brightness will be described.
As shown in FIG. 9, the brightness of the image is proportional to the voltage V _CRT from the cutoff level of the CRT drive signal. Since the wave height levels of the BRPs of G, B, and R match the cutoff level by the bias adjustment, if the amplitude of the BRP is changed as shown in FIG. 10, the voltage with the cutoff level is relatively changed and the brightness is increased. Change. G before increasing the brightness in FIG. 10A and after increasing the brightness in FIG. 10B,
The voltages from the cut-off levels of the B and R CRT drive signals are respectively VbG, VbB, VbR and VbG ', VbB', Vb.
If R ′, BRP is superimposed on G, B, and R with the same amplitude, so that VbG′−VbG = VbB′−VbB = VbR′−VbR, and the change in brightness is uniform for G, B, and R. Can be adjusted. Here, the brightness / bias adjustment reference is not the pedestal level or the like but the voltage of the peak value of the BRP. The reason is that if the change information is not transmitted to the brightness / bias adjustment reference when the contrast amount changes, the hue depends on the gradation. Is changed.
The description will be described in detail with reference to FIGS.

When the pedestal level is used as the bias adjustment reference without superimposing BRP, the contrast and brightness are adjusted as shown in FIG. That is, in order to increase the contrast, FIG.
When the video signal is changed to (b) and the brightness is increased, it is changed from FIG. 11 (a) to FIG. 11 (c). Figure 1
In No. 2, when the contrast is changed as shown in FIGS. 12A to 12B by the method of FIG. 11, when the pedestal level is set to the reference potential, the hue changes at the final gradation of the staircase wave. It shows the situation. The hue is determined by the brightness ratio of GBR, and the brightness ratio is proportional to the voltage ratio from the reference potential. In FIG. 12A, the voltage ratio from the clamp level, which is the reference potential, to the final stage of the staircase wave is, for example, VBG: VBB: VBR = 33: 23: 13, whereas in FIG. Is, for example, VBG ': VBB':
VBR '= 18: 13: 8 and the hue changes.

FIG. 13 shows a case where the BRP pulse is superimposed and the amplitude of the BRP pulse also changes as the contrast amount changes. Unlike FIG. 12, in FIG. 13, even if the contrast changes from FIG. 13A to FIG.
The voltage ratio between the reference potential of each R and the final stage of the staircase wave is, for example, VBG: VBB: VBR = VBG ': VBB': VBR '= 13:
It did not change to 8: 3, and therefore no change in hue occurred.

As described above, according to this embodiment, the CT
The two pulses of P and BRP are equally superimposed on the blanking period of each video signal of G, B and R, and the pulse is detected from the video signal applied to the cathode to detect the drive voltage and bias of each of G, B and R. Contrast is controlled by voltage,
Brightness, drive, bias control,
Good white balance can be obtained without being affected by the gradation of the image.

Further, since the feedback loop is formed by including the output circuit 13 for driving the CRT from the control section 12 for controlling the contrast and brightness, it is possible to suppress the temporal change of the video signal processing system.

FIG. 14 is a detailed block diagram of the detection unit 14 in the second embodiment of the present invention. In FIG. 14, 146
Is a current detection circuit for detecting the current flowing through the cathode, 14
Reference numeral 7 is a current-voltage conversion circuit that converts current into voltage. In FIG. 14, the same operations as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The current detection circuit 146 is applied to the cathode.
The current flowing to the cathode by the CRT drive video signal
It is detected and output to the current-voltage conversion circuit 147. Current
The pressure conversion circuit 147 performs conversion from current to voltage and
Output to the hold circuit 144. Sample hole
The drive circuit 144 follows the sample timing of FIG.
The BRP test signal is sampled and held. CRT
Driving video signal voltage V _CRTAnd the brightness L of the output image
Is L ≒ K1 ・ V_CRT ³(K1: proportional coefficient)
And cathode current I_KAnd the brightness L of the output image is L
= K2 · I_K(K2: proportional coefficient). for that reason
To adjust the brightness L of the output image V_CRTWith the voltage value
I than control_KIt is more accurate to control with the current value
I can. With the configuration according to the second embodiment, the BRP test
Hold the sampled cathode current
The bias adjustment is performed by the circuit 144 as compared with the first embodiment.
It can be adjusted more accurately. BRP level to cathode current
Although it can be adjusted with high accuracy by detecting with,
The TP level cannot be detected by the cathode current. The reason for this
Will be described with reference to FIG. BRP is a tone of brightness
The amplitude changes depending on the adjustment.
The peak value level of BRP is always fixed to the bias value VB.
Be done. The peak value level of BRP in FIG. 15 was explained in FIG.
The reason for fixing the bias value VB instead of the cutoff level
The reason is that a current due to BRP is passed through the cathode.

Therefore, by setting the bias value VB to an appropriate value, the cathode current with respect to BRP always flows in the same manner and detection is possible. However, as shown in FIG. 15, the pedestal level and the CTP peak value level fluctuate due to the brightness adjustment. As a result, as shown in FIG. 15, the pedestal level and the peak value of CTP exceed the cutoff level, and there is a possibility that the cathode current does not flow and detection becomes impossible. Therefore, CTP must rely on voltage level detection.

As described above, according to this embodiment, the CTP is detected by the C
The detection by the voltage of the RT drive video signal and the detection of BRP are B
By detecting the cathode current flowing by RP,
The black level of the output image can be controlled with higher accuracy.

In the present embodiment, both CTP and BRP are superimposed on the horizontal blanking period, but it goes without saying that one may be superimposed on the vertical blanking period or one on the horizontal and the other on the vertical blanking period. Yes.

Needless to say, the order in which CTP and BRP are superposed is not limited.

Further, in the present embodiment, the operation of the superimposing section 11 has been described by the superimposing method by switching the video signal and the test signal by using the switch circuit 112. However, for example, a method of adding the test signal to the video signal, or other method It goes without saying that the test signal may be superimposed on the video signal by the method.

Although CTP and BRP are pulse waves separated from each other, for example, CTP and BRP are continuously connected to each other.
The same effect can be obtained with a waveform like a stepped wave.

In the description of the operation of the detector 14, the CTP
Although the method of detecting the amplitude of the CTP using two sample-hold circuits and one subtractor has been described, it goes without saying that the CTP amplitude may be detected using another method.

In this embodiment, the control unit 14 controls the gain of the video signal and the direct current reproduction, and the control unit 14 and the output circuit 15
However, the same effect can be obtained by a cathode clamp in which the control unit 14 only controls the gain of the video signal and the direct current reproduction is performed by the output circuit 15. At this time, the DC reproduction control signal from the signal generator 15 is output from the output circuit 1.
Then, the video signal is fed back to the control circuit 14, and after the gain control, the video signal is optimally clamped and output as the input of the output circuit 15.

Further, the present embodiment is an example of a television receiver and does not limit the equipment in which the present apparatus is incorporated.

[0038]

As described above, the video signal processing apparatus of the present invention automatically superimposes two test signals for gain and DC reproduction during the blanking period of the video signal and compares them with the reference signal. In addition, the contrast, drive, brightness, and bias are controlled to stabilize the video signal processing system, and the white balance for each gradation can always be correct.

Further, in the present invention, since the video signal applied to the cathode is detected, it is possible to detect the characteristic change on the CRT side and suppress the variation.

Further, according to the present invention, the contrast relating to the gain of the video signal and the control of the drive are simultaneously performed to simplify the circuit structure, so that the practical effect thereof is great.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of a video signal processing device according to a first embodiment of the present invention.

FIG. 2 is a waveform timing chart showing the operation of the embodiment.

FIG. 3 is a block diagram showing a detailed configuration of a superimposing unit of the embodiment.

FIG. 4 is a block diagram showing a detailed configuration of a detection unit of the embodiment.

FIG. 5 is a block diagram showing a detailed configuration of a signal generator of the embodiment.

FIG. 6 is a block diagram showing a detailed configuration of a control unit of the embodiment.

FIG. 7 is an explanatory diagram showing the relationship between the input signal and the brightness of the output screen for explaining the operation of the embodiment.

FIG. 8 is an explanatory diagram showing a relationship between an input signal and brightness for explaining the operation of the embodiment.

FIG. 9 is a waveform diagram of a video signal for explaining the operation of the embodiment.

FIG. 10A is a waveform diagram of each GBR of the CRT drive signal of the same embodiment, and FIG. 10B is a diagram showing the C when the brightness is increased from the state of FIG.
Waveform diagram of GBR of RT drive signal

11A is a waveform diagram of a video signal, and FIG. 11B is a waveform diagram when the contrast of the video signal is increased from the state of FIG. Waveform diagram when raised

12A is a waveform diagram of a video signal based on a pedestal level, and FIG. 12B is a waveform diagram when the contrast is lower than that in the state of FIG.

13A is a waveform diagram of a video signal with a clamp level as a reference, and FIG. 13B is a waveform diagram when the contrast is lower than that in the state of FIG.

FIG. 14 is a block diagram showing a detailed configuration of a detection unit according to the second embodiment of the present invention.

FIG. 15 is a waveform chart showing the relationship between BRP, CTP, pedestal level and cutoff level in the same Example.

FIG. 16 is a block diagram showing a configuration of a conventional video signal processing device.

FIG. 17 is a waveform diagram showing a video signal after the test signal is superimposed in the conventional example.

[Explanation of symbols]

11 Superposition section (superposition means) 12 Control unit (control means) 13 Output circuit (output means) 14 Detection unit (detection means) 15 Signal generator (signal generator) 16 Generator (Generator)

Claims (2)

[Claims] 1. A generating means for generating a test signal for controlling gain and luminance by superimposing in a blanking period of a video signal, and a superimposing means for superimposing the test signal on the video signal.
Control means for controlling the gain and brightness of the video signal output from the superimposing means, output means for amplifying the output of the control means and outputting to the display device, and the output signal from the output means. Detection means for detecting the test signal,
It is provided with a signal generation means for comparing the detected test signal with a reference signal and generating a control signal for controlling the control means, and the control signal from the signal generation means is fed back to the control means. Video signal processing device. 2. The detecting means detects the test signal for gain control by detecting the voltage of the test signal, and detects the test signal for luminance by detecting the cathode current flowing by the test signal. The video signal processing device according to claim 1.