JPS601793B2 - Image quality improvement device for color television receivers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for improving the image quality of colored image portions of color television images, and in particular is adapted to satisfactorily reproduce fine images in colored portions. .

FIG. 1 is a block diagram showing a part of a conventional color television receiver.

In the figure, an m signal (intermediate frequency signal) is detected by a video detector 1 and supplied to a luminance signal amplifier 2 and an Obishiro amplifier 3. The Obishiro amplifier 3 takes out the carrier color signal included in the composite color video signal, amplifies it, and supplies it to three color difference signal demodulators 4, 5, and 6. The color difference signal demodulators 4 and 5
, 6 demodulates the carrier color signal to generate three types of color difference signals (R-Y
), (GmY), and (B-Y) and supply them to three adders 7, 8, and 9.

The adders 7, 8, and 9 add the color difference signals supplied to each adder and the luminance signal transmitted from the luminance signal amplifier 2 to create three primary color signals R, G, and B, and add them. The picture tube 10' is supplied. ``In the conventional color television receiver as described above, the bandwidth of the color difference signal (for example, the R-Y output of the color difference signal demodulator 4) is the same as the bandwidth of the luminance signal transmitted from the luminance signal amplifier 2. much narrower than

For example, in a normal NTSC color television receiver, the luminance signal contains frequency components from z to z, while the color difference signal only contains frequency components up to about 50 yen. Therefore, in a colored image part, the image is mainly composed of narrow band color difference signals, resulting in a blurred image with low sharpness. Therefore, in order to eliminate the above-mentioned drawbacks of the conventional method, the present invention improves the resolution of colored image parts by actively mixing high-frequency components of the luminance signal according to the intensity of the color difference signal. The present invention provides a device which is characterized in that the amount of correction can be varied depending on the magnitude of the transient portion of the luminance signal. A detailed explanation will be given below based on the figures.

FIG. 2 is a block diagram representing an embodiment of the invention.

The color difference signal source 11 generates a color difference signal, and the first
It may be any of the color difference signal demodulators 4, 5, and 6 shown in the figure. The luminance signal source 12 generates a luminance signal,
The brightness signal intensifier 2 shown in FIG. 1 may also be used. The non-traditional line transmission circuit 13 is supplied with a color difference signal from the color difference signal source 11, gives the signal a non-linear transmission characteristic, and then outputs it as a gain control signal. The transmission characteristics of this non-linear transmission circuit 13 can be arbitrarily selected depending on what kind of correction signal is to be applied to each level of the color difference signal. In other words, if you want to control the magnitude of the correction signal to be constant when the amplitude of the color difference signal exceeds a certain level, you can use a circuit with limiter characteristics, and only when the amplitude of the color difference signal exceeds a certain level, the correction signal is controlled. When applying a signal, it is sufficient to use a circuit with base clipping characteristics.Furthermore, when trying to apply a larger correction signal when the color difference signal becomes large, a circuit with two-way characteristics can be used. All you have to do is use it. High frequency extraction circuit 14
The filter extracts the high frequency component of the luminance signal supplied from the luminance signal source 12, and is not limited to a simple Takagi pass filter. The brightness level change rate detector 21 detects the magnitude of the change in the brightness signal and creates a control signal for controlling the next stage based on the magnitude of the change in the brightness signal. The modulator 22 modulates the high frequency component of the brightness signal from the high frequency extraction circuit 14 based on the control signal from the brightness level detector 21, and uses a multiplier. The variable gain multiplier 15 is configured such that the increase in gain of the output from the modulator 22 is controlled by a gain control signal output from the nonlinear transmission circuit 13. The high frequency component of the luminance signal whose gain has been controlled is supplied as a correction signal to the adding device 16, where it is added to the color difference signal and the luminance signal to provide video display. This addition device 1
Reference numeral 6 is an addition device in a broad sense in the sense of composing images, and is not limited to a simple electronic circuit, but includes, for example, compositing in an electron gun of a picture tube and compositing at the light emitting stage.
In this embodiment, the brightness level change rate detector 21 and modulator 22 have essential meaning.

A block diagram in which the main circuits 21 and 22 are omitted is shown in FIG. In this figure, the following calculations are generally performed. The correction signal, that is, the output of the variable gain intensifier 15 (
C-Y) If C, then (C-Y).

=YH×(C−Y)N Here, YH is the high frequency component of the luminance signal, and (C−Y)N is the color difference signal passed through the nonlinear transmission circuit 13.

Looking at this, the correction signal includes high frequency components of the luminance signal corresponding to the color difference signal, but since the polarities of the rate of change of the color difference signal and the luminance signal do not necessarily match, the transient part of the color difference signal This has the potential to result in a correction signal that blunts the

This is contrary to the main purpose of the present invention, which is to improve the resolution of the colored image portion. Therefore, the present invention suppresses the above-mentioned drawback by detecting the rate of change in the brightness level and reducing the correction signal when the change in the brightness level is large. Next, FIG. 4 shows a detailed block diagram of the brightness level change rate detector 21, which is the main part of the present invention. Blocks designated with the same numbers as in FIG. 2 are similar. The luminance signal from the luminance signal source 92 is input to the differentiating circuit a, where it is differentiated. The differentiation referred to here may be a differentiation circuit using a resistor and a capacitor, or a difference circuit using a delay element and a difference device. Absolute value circuit of b The output of the differentiating circuit of a is input and its absolute value is taken. The appropriate inversion circuit c inverts the polarity of the input signal from b, and the DC level shift circuit d receives the output from C and shifts the DC level. An example of the waveform of each part is shown in FIG. Here, B is a luminance signal, and C is a high frequency component of the luminance signal, which corresponds to the above-mentioned YH. D is the output of the differentiation circuit of a, and E is the output of the absolute value circuit of b. Looking at this waveform E, it can be said that the rate of change in the brightness level is large where the vibration is large. F is the output of the DC level shift circuit of d, and by shifting to a certain DC level, the waveform of E is subtracted. Where the rate of change in brightness level is large, its value is close to 0, and where it is small, it is large. It will take on a value. This waveform F is input to the modulator 22. G is the output of the modulator 22 and can be considered as the product of C and F. This is because modulator 22 is usually a multiplier. In this way, a high frequency component of the luminance signal is obtained which is considered to be inversely proportional to the magnitude of the rate of change in the luminance level. In FIG. 5, A is a color difference signal, and the rising and falling directions of the luminance signal 8 do not necessarily match.

The part A is the case where the polarities match, and the part A is the case where the polarities do not match. In either case, as described above, the high-frequency signal of the luminance signal appears only in a portion where the rate of change of the luminance signal is relatively small, as shown in G. The day is G
is a signal whose gain is controlled by A, and T is a sum signal of day and A, which can be said to be a corrected color difference signal. This signal is then added to the luminance signal B to display an image in the same manner as in a normal color television receiver. Note that in this device, the color difference signal is corrected only when the rate of change in the level of the luminance signal is small, but in this case, the polarities of the rate of change of the color difference signal and the brightness signal may not match.

Even in such a case, since the magnitude of the correction signal applied to the color difference signal is not so large, there is not much negative effect on the color.In fact, coloring is caused by applying the harmonic components of the luminance signal to the color difference signal. By adding a fine outline or the like to a portion, a large visual effect can be obtained in that the resolution appears to be significantly improved. As described above, according to the present invention, high frequency components of a luminance signal are extracted,
By actively adding the color difference signal to the original signal according to the strength of the color difference signal, it is possible to improve the resolution deterioration of the colored image portion.

Further, in this case, by limiting the above-mentioned operation in a portion where the rate of change of the luminance signal is large, it is possible to reduce malfunctions due to magnetic mismatch between the rate of change of the color difference signal and the luminance signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional color television receiver, FIG. 2 is a block diagram showing an image quality improvement device for a color television receiver according to an embodiment of the present invention, and FIG. FIG. 4 is a detailed circuit diagram of the main parts of the device shown in FIG. 2, and FIG. 5 is a waveform diagram showing signal processing waveforms of the same device. 1...Video detector, 2...Brightness signal intensifier, 3...Obijo intensifier, 4, 5, 6...
Color difference signal demodulator, 7, 8, 9... Adder, 10
... Picture tube, 11 ... Color difference signal source, 1
2... Luminance signal source, 13... Non-linear transmission circuit, 14... High frequency extraction circuit, 15...
...Variable gain multiplier, 16... Addition device, 2
1... Brightness level detector, 22... Modulator. Figure 3 Figure 1 Figure 2 Figure 4 Figure 5

Claims (1)

[Claims] 1. A nonlinear transmission circuit that is connected to a color difference signal source and creates a gain control signal by providing a nonlinear transmission characteristic with respect to the level of the color difference signal so as to apply a correction signal with desired characteristics to each level of the color difference signal. , a high-frequency extraction circuit connected to the luminance signal source to extract high-frequency components of the luminance signal, and a luminance circuit connected to the luminance signal source to detect the rate of change and create a modulation signal that acts suppressively in areas where the rate of change is large. A level detector is connected to the output terminal of the high frequency extraction circuit and the output of the brightness level detector, and is connected to the high frequency component of the brightness signal and the modulation signal so as to reduce the modulation output in a portion where the rate of change of the brightness signal is large. a modulator that modulates the high frequency component of the luminance signal by the modulation signal, and a modulator that is connected to the nonlinear transmission circuit and the output terminal of the modulator to increase the gain when the gain control signal is large a variable gain amplifier that controls the gain for the high frequency component of the modulated luminance signal to create a correction signal, and is connected to the variable gain amplifier, the color difference signal source, and the luminance signal source, and the correction signal 1. An image quality improving device for a color television receiver, comprising an adding device that substantially adds a color difference signal and a luminance signal to provide video display.