JPH0576034A - Picture signal processor - Google Patents

Abstract

PURPOSE:To provide a picture signal processor with a simple circuit configuration, in which the deterioration of the precise information of the high-pass components of a luminance signal can be appropriately corrected. CONSTITUTION:This device is equipped with a chroma detecting circuit 31 which subtracts the luminance signal from a color demodulated signal obtained by envelope-detecting a chrominance signal, and prepares a control signal corresponding to the chroma of a chromatic color picture, gain varying circuit 32 which controls the amounts of the high-pass frequency components of the luminance signal by changing a gain based on the control signal prepared by the pertinent chroma detecting circuit 31, and adding circuit 33 which adds the high-pass frequency components of the luminance signal outputted from the gain varying circuit 32 to the low-pass frequency components of the pertinent luminance signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention improves the high frequency characteristics of a luminance signal which deteriorates during transmission of a chromatic color image signal,
The present invention relates to an image signal processing device which makes a contour of a luminance signal of a chromatic image stand out.

[0002]

As is well known, for example, NTSC, PA
In the current color television systems such as L and SECAM, since the gamma correction process and the band limitation process of the color difference signal are performed on the transmission side, the information of the details of the image reproduced on the reception side is reduced in principle. It will be. This means that as the color saturation (saturation) increases, that is, as the color becomes darker, the amount of decrease in the luminance detail information increases.

An example of the NTSC system is shown in FIG.
Is shown in. The vertical axis represents the degree of deterioration of the luminance high frequency component (detail information amount), and the horizontal axis represents the color saturation (saturation).
Ye, cy, g, mg, r, b written on the right side of the figure are
It means yellow, cyan, green, magenta, red, and blue, respectively. As is clear from FIG. 6, the high-frequency component of the luminance signal has the property of being deteriorated as the color saturation is higher, and the property that the deterioration level is different depending on the color.

Therefore, in order to improve the above-mentioned problems, conventionally, for example, means as disclosed in Japanese Patent Publication No. 62-26234 has been considered. This is to control the amount of high frequency components of the luminance signal by a control signal according to the saturation of the subject. To improve the image quality.

Specifically, it is constructed as shown in FIG. The luminance signal including the carrier color signal supplied to the input terminal 11 is supplied to the color demodulation circuit 13 after the carrier color signal amplification circuit 12 extracts and amplifies the carrier color signal.
The color difference signals R-Y, G-Y, and B-Y are generated. The generated color difference signals R-Y, G-Y, and B-Y are taken out from the output terminals 14, 15 and 16, respectively, and are also supplied to the saturation detection circuit 17 to be a gain control signal corresponding to the saturation of the image. Is used for the production of.

The luminance signal supplied to the input terminal 11 is delayed by the delay circuit 18 and then supplied to the HPF (high-pass filter) 19 and the LPF (low-pass filter) 20, respectively. It is separated into a component and a low frequency component. The high frequency component has a gain variable circuit 21 in which the gain is variable based on the gain control signal output from the saturation detection circuit 17.
After the gain is controlled by the adder circuit 22, it is added to the low frequency component by the adder circuit 22 and taken out from the output terminal 23.

In a general television receiver, detailed information on luminance is lost and reproduced according to the saturation of the picture as described above. However, the television provided with the image signal processing device shown in FIG. In the receiver, the gain of the gain variable circuit 21 is controlled based on the gain control signal corresponding to the saturation of the image output from the saturation detection circuit 17, and the addition circuit 22 adds the gain to the low frequency component of the luminance signal. The amount of high frequency components of the luminance signal is controlled.

That is, the higher the saturation of the image, the greater the amount of emphasis of the high frequency component of the luminance signal, and the deterioration of the luminance detail information is corrected. For example, the amount of information that represents each petal of a red rose increases, and the contour of the image becomes clear.

The saturation detection circuit 21 is constructed as shown in FIG. The color difference signals R-Y, G-Y, and B-Y supplied to the input terminals 24, 25, and 26 are current-added via the diodes D1, D2, and D3 having the illustrated polarities, respectively, and then the terminals of the load resistor R1. A gain control signal corresponding to the saturation of the image is generated as a voltage and taken out from the output terminal 27.

Here, to each input terminal 24, 25, 26,
Consider a case where a color difference signal shown in FIG. 9B corresponding to the color bar shown in FIG. 9A is input. In addition,
FIG. 9B shows color difference signals R-Y, G-Y, and B from the top in the figure.
Each of the -Y signal waveforms is shown.

For example, in the case of red, the color difference signal R-Y has the highest voltage level, and the voltage levels of the other color difference signals G-Y and BY are lower than the voltage level of the color difference signal R-Y. , Only diode D1 conducts and other diodes D2,
Since D3 is non-conducting, the output terminal 27 is connected to FIG.
As shown in (c), the same voltage level as the color difference signal RY appears as the gain control signal. In addition, each diode D
The forward offset voltages of 1, D2 and D3 are ignored for simplicity of explanation.

In the case of yellow, for example, the color difference signal R
-Y and G-Y have substantially the same voltage level, and the color difference signal B-
Since the voltage level of Y is lower than the voltage levels of the color difference signals R-Y and G-Y, the diodes D1 and D2 are conducting and the other diode D3 is non-conducting.
As shown in FIG. 9C, the same voltage level as the color difference signals R-Y and G-Y appears as a gain control signal.

Similarly, for any other color, the output terminal 27 is supplied with a voltage level equal to the color difference signals R-Y, G-Y, and B-Y having the highest voltage level for each color. It appears as a control signal, so in the end,
In the case of the color bar shown in FIG. 9A, the gain control signal as shown in FIG. 9C is obtained.

That is, the color difference signals R-Y, G-Y, B-
Since the amplitude of Y changes according to the color density, the voltage level of the gain control signal also changes accordingly. Then, since the gain of the variable gain circuit 21 is controlled based on this gain control signal, the enhancement amount of the high frequency component of the luminance signal of the dark-colored picture portion is increased, and the deterioration of the luminance detail information is corrected, The image is sharp.

In other words, when the waveform of the gain control signal shown in FIG. 9C is compared with the characteristic showing the deterioration degree of the high frequency component of the luminance shown in FIG. 6, they are complementary to each other. It turns out that there is a relationship. That is, the voltage level of the gain control signal is high in dark (low luminance level) colors such as red and blue in which the detailed luminance information is large, and the gain control signal based on the gain control signal thus obtained is used. Since the amount of emphasis of the high frequency component of the luminance signal is controlled by the above, appropriate deterioration correction of detailed luminance information is performed.

However, in the conventional image signal processing apparatus as described above, in order to generate the gain control signal according to the color saturation, the carrier color signal is color demodulated and the color difference signal R-
Y, G-Y, B-Y are generated, and then each color difference signal R-
Since the maximum voltage levels of Y, G-Y, and B-Y are selected, the color demodulation circuit 13 is required, which causes a problem that the circuit scale increases.

In particular, in the case of the NTSC system, the color difference signals R-Y, G-Y, and B-Y can be obtained by carrying out color demodulation of the carrier color signal with subcarriers having different phases by 90 °, so that the circuit scale is small. However, in the PAL system, since the phase of the color subcarrier of the color difference signal R-Y is inverted by 180 ° for each scanning line, the color demodulation circuit requires a 1H delay line, and thus the above problem occurs. It has become more serious.

[0018]

As described above, in the conventional image signal processing device, since it is necessary to generate the color difference signal in order to generate the gain control signal according to the color saturation, the color demodulation circuit. Therefore, there is a problem that the circuit scale is increased due to the need for

Therefore, the present invention has been made in consideration of the above circumstances, and is a very good image signal processing capable of appropriately correcting the deterioration of the detailed information of the high frequency component of the luminance signal with a simple circuit configuration. The purpose is to provide a device.

[0020]

An image signal processing apparatus according to the present invention controls a luminance signal by subtracting a luminance signal from a color demodulation signal obtained by envelope detection of a color signal, and performing control according to the saturation of a chromatic color image. Saturation detecting means for generating a signal; gain varying means for controlling the amount of high frequency components of the luminance signal by changing the gain based on the control signal generated by the saturation detecting means; It is provided with an adding means for adding the high frequency component of the luminance signal output from the gain varying means and the low frequency component of the luminance signal.

[0021]

According to the above construction, the luminance signal is subtracted from the color demodulation signal obtained by envelope detection of the color signal to generate the control signal according to the saturation of the chromatic color image, and this control is performed. Since the amount of the high frequency component of the luminance signal is controlled based on the signal and added to the low frequency component of the luminance signal, the deterioration of the detailed information of the high frequency component of the luminance signal can be appropriately performed with a simple circuit configuration. You will be able to correct it.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, the luminance signal supplied to the input terminal 28 is supplied to the LPF 29 and the HPF 30, respectively, and separated into a low frequency component and a high frequency component. The high frequency component is subjected to gain control by a gain variable circuit 32 whose gain is varied based on a gain control signal output from a saturation detection circuit 31 described later, and then added to a low frequency component by an adder circuit 33 and output. It is taken out from the terminal 34.

The saturation detection circuit 31 outputs a composite image signal, which is a combination of a luminance signal and a color signal, which is input via the input terminal 35, by a Y / C (luminance / color) -separated color signal. , Based on the luminance signal supplied to the input terminal 28,
A gain control signal according to the saturation of the image is generated and output to the gain variable circuit 32. For this reason, the gain of the gain variable circuit 32 changes according to the saturation, so that the amount of emphasis of the high frequency component of the luminance signal can be changed, and the deterioration of the detailed information on the luminance is corrected and the image becomes clear.

FIG. 2 shows a specific example of the saturation detection circuit 31. That is, the color signal supplied to the input terminal 35 is half-wave or full-wave rectified by the rectifying circuit 36 and the LPF 3 is rectified.
The envelope is detected at 7, and the arithmetic circuit 38 inputs the input terminal 2
After the luminance signal supplied from 8 is subtracted, the gain control signal is generated by passing through the clamp circuit 39 and is taken out from the output terminal 40.

Specifically, the input terminals 35 and 28 are
Consider a case where a color signal and a luminance signal corresponding to the color bar shown in FIG. Note that FIG.
(G) shows the signal waveforms at points (b) to (g) in FIG. 2, respectively. That is, supplied to the input terminal 35,
The color signal including the carrier color signal as shown in FIG. 3B is half-wave or full-wave rectified by the rectifier circuit 36 as shown in FIG. 3C, and the LPF 37 as shown in FIG. The envelope is detected.

The output signal of the LPF 37 is subtracted by the arithmetic circuit 38 from the luminance signal supplied to the input terminal 28 as shown in FIG. 3 (e) to become a signal shown in FIG. 3 (f).
After that, the clamp circuit 39 clamps the reference potential Vref to generate the gain control signal shown in FIG.

By the way, as described above, the gain control signal output from the saturation detection circuit 31 needs to be complementary to the luminance signal level. That is, in the case of a luminance signal of a dark color, if a gain control signal with a high voltage level is generated, it is possible to perform correction according to the deterioration of detailed luminance information.

Now, comparing the gain control signal of this embodiment shown in FIG. 3 (g) with the conventional gain control signal shown in FIG. 9 (c), the difference between the two signals is yellow. It is at the blue voltage level. In FIG. 3 (g), the yellow gain control signal level is zero. This is because the reference potential Vref of the clamp circuit 39 is set to the position shown in FIG.

The fact that the yellow gain control signal level is zero is not a big problem. This is because, as shown in FIG. 6, yellow itself has a small degree of deterioration. Furthermore, in general, saturation 1
This is because the signal of 00% is extremely rare, and in the case of normal saturation (about 40%), the degree of deterioration is even smaller.

Next, the gain control signal level for blue is lower than the voltage level for red in FIG. 3 (g). That is, the correction amount of the detailed luminance information in the blue portion is slightly lower than the correction amount of red. However, although the blue correction amount is slightly smaller, the configuration of this embodiment is much simpler than the conventional configuration and the circuit scale can be reduced, which is economically advantageous.

Therefore, according to the configuration of the above embodiment, the deterioration of the image quality caused by the principle of the current color television system, that is, the detailed information of the luminance is lost in the dark pattern portion of the chromatic color image. Therefore, the problem that the conventional image signal processing device has, that is, the drawback that the circuit is complicated and large in scale, is eliminated, and the circuit is very simple and the image quality improving effect equivalent to that of the conventional device can be obtained. it can.

As an example, considering the case of supporting the NTSC system and the PAL system, conventionally, a demodulation circuit for carrier color signals corresponding to each system is naturally required, and in particular, a demodulation circuit for carrier color signals of the PAL system is required. Has a much more complicated circuit structure than that of the NTSC system. On the other hand, this embodiment has a simple circuit configuration in which the luminance signal is subtracted from the signal in which the carrier chrominance signal is envelope-detected by utilizing the property of the amplitude modulation wave.
There is an advantage that the system can be handled by one circuit.

FIG. 4 shows another example of the saturation detection circuit 31. That is, when the same parts as those in FIG. 2 are designated by the same reference numerals, the limiter circuit 4 is provided at the subsequent stage of the clamp circuit 39.
1 is provided. If the limit voltage level of the limiter circuit 41 is set to be the same as the voltage level of the blue portion of the gain control signal shown in FIG.
The gain control signal obtained from 0 has a waveform as shown in FIG.

That is, comparing with the waveform of the gain control signal shown in FIG. 3 (g), since the voltage levels are the same in red and blue, the difference in the correction amount between red and blue is improved. It will be.

FIG. 5 shows still another example of the saturation detection circuit 31. That is, when the same parts as those in FIG. 4 are designated by the same reference numerals, the luminance signal supplied to the input terminal 28 is supplied to the arithmetic circuit 38 via the slice circuit 42. When the luminance signal shown in FIG. 3 (e) is sliced at the magenta level by the slicing circuit 42, the luminance signals subtracted from the envelope detection signal of the color signal by the arithmetic circuit 38 are white, yellow, cyan, and
It becomes green, and the degree of freedom of the voltage level extraction range in the gain control signal can be increased. The present invention is not limited to the above-described embodiments, but can be variously modified and implemented without departing from the scope of the invention.

[0036]

As described in detail above, according to the present invention,
It is possible to provide an extremely good image signal processing device having a simple circuit configuration and capable of appropriately correcting the deterioration of the detailed information of the high frequency component of the luminance signal.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an embodiment of an image signal processing device according to the present invention.

FIG. 2 is a block configuration diagram showing a specific example of a main part of the embodiment.

FIG. 3 is a diagram shown for explaining the operation of the main part.

FIG. 4 is a block diagram showing another example of the main part.

FIG. 5 is a block configuration diagram showing still another example of the main part.

FIG. 6 is a characteristic diagram showing the degree of deterioration of a luminance signal with respect to saturation.

FIG. 7 is a block configuration diagram showing a conventional image signal processing device.

FIG. 8 is a circuit configuration diagram showing a specific example of a saturation detection circuit of the conventional device.

FIG. 9 is a diagram shown for explaining the operation of the same saturation detection circuit.

[Explanation of symbols]

11 ... Input terminal, 12 ... Carrier color signal amplification circuit, 13 ... Color demodulation circuit, 14-16 ... Output terminal, 17 ... Saturation detection circuit, 18 ... Delay circuit, 19 ... HPF, 20 ... LPF, 2
1 ... Gain variable circuit, 22 ... Adder circuit, 23 ... Output terminal,
24 to 26 ... Input terminal, 27 ... Output terminal, 28 ... Input terminal, 29 ... LPF, 30 ... HPF, 31 ... Saturation detection circuit, 32 ... Gain variable circuit, 33 ... Addition circuit, 34 ... Output terminal, 35 ... Input terminal, 36 ... Rectifier circuit, 37 ... LP
F, 38 ... Arithmetic circuit, 39 ... Clamp circuit, 40 ... Output terminal, 41 ... Limiter circuit, 42 ... Slice circuit.

Claims (1)

[Claims] 1. A saturation detection unit for subtracting a luminance signal from a color demodulation signal obtained by envelope detection of a color signal to generate a control signal corresponding to the saturation of a chromatic color image, and the saturation detection unit. Gain varying means for controlling the amount of the high frequency component of the luminance signal by changing the gain based on the control signal generated by the means, and the high frequency of the luminance signal output from the gain varying means. An image signal processing apparatus comprising: an addition unit that adds a component and a low frequency component of the luminance signal.