JPH0576033A - Picture signal processor - Google Patents

Abstract

PURPOSE:To correct the resolution of a deteriorated luminance signal and to improve a picture quality by a precise control at each color phase by adding the high-pass frequency components of the luminance signal outputted from a gain varying means to the main components of the luminance signal. CONSTITUTION:The positive sides of color difference signals R-Y, B-Y, and G-Y are respectively extracted from each positive side extracting circuit 31-33, and the output of a multiplying circuit 35 which multiplies the positive sides of the color difference signals R-Y and B-Y is turned to a signal indicating the amounts of the color in a Magenta direction. And also, the output of a multiplying circuit 36 which multiplies the positive sides of the color difference signals B-Y and G-Y is turned to the signal indicating the amounts of the color in a cyanide direction, and the output of a multiplying circuit 37 which multiples the positive sides of the color difference signals G-Y and R-Y is turned to the signal indicating the amounts of the color in an yellow direction. Then, the output of an adding circuit 38 which synthesizes the outputs of the circuits 35-37 is turned to the signal corresponding to the concentration of each color of the Magenta, cyanide, and yellow. A new gain control signal can be prepared by adding or subtracting the signal to or from a gain control signal outputted from a color difference signal synthesizing circuit 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal processing apparatus for improving the quality of reproduced image of a color television signal by correcting the deterioration of the high frequency component of the luminance signal in the dark pattern portion. ..

[0002]

As is well known, for example, NTSC, PA
It is known that in the current color television systems such as L and SECAM, the resolution is deteriorated in a dark pattern portion and the degree of deterioration is different depending on the hue. This is also described in detail in, for example, the broadcasting technology book "Color Television" (published by the Japan Broadcasting Corporation in 1936).

That is, in a television signal that is gamma-corrected and transmitted on the transmitting side, the correct luminance signal Yi
And the luminance Y of the screen to be reproduced are Yi ≧ Y, and Yi = Y only when the three primary color signals Er, Eg, Eb are Er = Eg = Eb, and otherwise, that is,
In the case of a chromatic color image, the brightness is always deteriorated and the three primary color signals E
The greater the difference between r, Eg and Eb, the greater the deterioration.

FIG. 5 shows the degree of deterioration of luminance in the NTSC system, in which the horizontal axis shows the color saturation and the vertical axis shows the resolution. The parameter is the hue, which is blue (b), red (r), green (g), cyan (cy), magenta (m).
g) and yellow (ye) are shown as parameters. The frequency is the upper limit of the band-limited color difference signal, that is, about 1.5M.
It is set higher than Hz. As is clear from FIG.
The resolution of the NTSC signal changes depending on the color saturation and hue,
Although yellow has almost no deterioration, blue has a large deterioration and has a deterioration of 20 dB at a saturation level of 100%.

As a means for correcting the above-described deterioration of brightness on the receiver side, for example, Japanese Patent Publication No. 62-26234 discloses that a reproduction color difference signal is used for correction. That is, as shown in FIG. 6, the composite signal supplied to the input terminal 11 is supplied to the color demodulation circuit 13 after the color signal is amplified by the color amplifier circuit 12, and the three kinds of color difference signals R are supplied.
Demodulated into -Y, G-Y, and BY. The demodulated color difference signals R-Y, G-Y, and B-Y are output terminals 14,
Saturation detection circuit 1 taken out from
7 and is used for generating a gain control signal according to the saturation of the television signal.

The composite 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 to obtain a luminance signal. Is separated into a high frequency component and a low frequency component. The high frequency component is amplified by a gain variable circuit 21 in which the gain is varied based on a gain control signal output from the saturation detection circuit 17 so as to be emphasized in an image portion with higher saturation, and then added. It is added to the low frequency component at 22 and taken out from the output terminal 23.

With this configuration, it is possible to emphasize the high frequency component of the luminance signal according to the saturation,
It is possible to correct the deterioration of the resolution of the luminance signal in the image portion with high saturation, which is a drawback of the color television signal. The important point in this means is that the saturation detection circuit 1
7 is how to configure. The above-mentioned Japanese Patent Publication No. 62-26234 has a configuration in which the maximum level signal of the three types of color difference signals is taken out as a gain control signal.

That is, as shown in FIG. 7, the input terminal 2
4, 25, and 26 supplied to the color difference signals R-Y, G-Y,
BY is diodes D1, D2, and
After current addition via D3, a gain control signal corresponding to the saturation of the image is generated as the terminal voltage of the load resistor R1 and is taken out from the output terminal 27.

The saturation detection circuit 17 configured as described above
Outputs a good gain control signal despite its simple circuit configuration. That is, a high-level gain control signal is output for blue or red that has a large degree of deterioration due to gamma correction, and a low-level gain control signal is output for yellow or cyan that has a small degree of deterioration. Further, the achromatic signal is not emphasized at all.

By the way, the above-mentioned conventional image signal processing means has sufficient characteristics for the purpose of correcting the deteriorated luminance signal, but in consideration of its use for image quality adjustment, it is still a fine control. Therefore, there is a problem in that the optimum correction or enhancement cannot be performed because it cannot be performed.

For example, human visual characteristics have a characteristic that the sensitivity is lower in a brighter image portion, and it is not possible to perform correction including it. In particular, since yellow is generated in a portion having high brightness, it is desirable to emphasize yellow a little strongly according to visual characteristics. In addition, considering the human vision and impression, it is effective to emphasize not only dark red and blue but also emphasize cyan and green and suppress magenta emphasis.

Usually, in the image appearing on the screen, blue and the like often appear as a plain image portion. Looking around the natural world, there is almost no dark blue color. For this reason, even if blue that is severely deteriorated is corrected, a visual impression is not seen enough to match the correction amount.

On the other hand, cyan, green, or yellow-green often appears in fresh image scenes. For example, fresh green vegetation, vast lawn, sea spray, soda water poured into a cup,
Images with a fresh impression on humans, such as the blue sky with clouds, often have such hues, and if this hue is emphasized, it will be perceived as a fresher image because it matches human consciousness, and the visual effect Will grow.

Magenta has a very low probability of appearing in a natural image, and there are almost no magenta images requiring resolution except for some flowers. Magenta is a color in which noise is easily noticeable, and particularly in a reproducing apparatus having a poor basic image quality such as a VTR (video tape recorder), noise and hue shift are very noticeable. As can be seen from FIG. 5, magenta is also a color in which resolution deterioration is relatively large, so that luminance enhancement is strongly performed by correction, so that noise becomes more severe. In other words, considering the quality of the reproduced image as well as other situations, the luminance signal is not reproduced flat regardless of the saturation, and the magenta system is weak.
It is desirable to emphasize greens and cyans strongly.

However, the conventional image signal processing means shown in FIG. 6 cannot perform the above correction. That is, the saturation detection circuit 17 causes each color difference signal R-
Although the maximum levels of Y, G-Y, and B-Y are selected, in the case of magenta, the amount of enhancement is determined by the darkness of blue. That is, when magenta is detected, RY and BY have a positive value, and G-Y has a negative value. If this maximum level is taken, the higher level of RY and BY will be output.

Since magenta has a slightly higher level in BY than in RY, the magenta control amount is determined by the size of BY. In magenta, which is slightly red, the level of RY is higher than that of BY, and in this case, the control amount is determined by the size of RY. That is, magenta is not controlled by the magenta axis, but is controlled by the magnitude of RY or BY at that time.
Therefore, if the R-Y gain is reduced in order to reduce the magenta enhancement, the blue correction amount will decrease. To increase the amount of cyan enhancement,
It is necessary to make BY a little larger, but if this is done, there is the disadvantage that magenta is also emphasized for the reasons described above.

[0017]

As described above, since the conventional image signal processing apparatus does not detect the axes such as magenta, cyan, and yellow, fine control cannot be performed and optimum correction or enhancement can be performed. I have a problem that I can not. Therefore, it is impossible to perform optimum control for each medium such as VTR, television broadcasting, laser disk and the like.

Therefore, the present invention has been made in consideration of the above circumstances, and not only corrects the resolution of the deteriorated luminance signal but also enables fine control for each hue to contribute to the improvement of image quality. It is an object of the present invention to provide an extremely good image signal processing device that can be used.

[0019]

An image signal processing device according to the present invention multiplies the positive side comrades of a plurality of color difference signals and calculates the multiplication output and the combined output of the positive side comrades of the plurality of color difference signals. The saturation detection means for generating a control signal according to the saturation of the chromatic color image, and the gain being changed based on the control signal generated by the saturation detection means by A gain varying means for controlling the amount of the component,
The adding means for adding the high frequency component of the luminance signal output from the gain varying means and the main component of the luminance signal is provided.

[0020]

According to the above-mentioned structure, the positive side comrades of a plurality of color difference signals are multiplied, the multiplication output and the positive side compositing output of the plurality of color difference signals are calculated, and the saturation of the chromatic color image is calculated. Is generated, and the amount of high frequency components of the luminance signal is controlled based on this control signal to be added to the main component of the luminance signal. Not only the correction but also the fine control for each hue can be made possible to promote the improvement of the image quality.

[0021]

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, 28, 29, 3
Reference numeral 0 is an input terminal to which the color difference signals R-Y, BY, and G-Y are respectively supplied. These input terminals 28, 29, 3
The color difference signals R-Y, B-Y, and G-Y supplied to 0 are supplied to the color difference signal synthesis circuit 34 via the positive-side extraction circuits 31, 32, and 33, respectively.

The positive side extraction circuits 31, 32 and 33 have a function of extracting the positive side of the color difference signals R-Y, BY and G-Y. For example, the diode D3 from the circuit shown in FIG.
Is deleted to make 2 inputs, and the color difference signal is input to R-
Y, BY, G-Y are supplied, and the color difference signal R is supplied to the other input.
It is realized by giving voltage levels of -Y, BY, and GY when there is no signal.

The color difference signal synthesizing circuit 34 includes a color difference signal R-
It suffices that Y, BY, and GY can be combined at an appropriate ratio, and a simple adder circuit or the configuration of the maximum value circuit shown in FIG. 7, for example, may be used. Various syntheses can be considered. The reason is that, in the case of this embodiment, if magenta or cyan increases when combined, it is possible to reduce it later, and if cyan or magenta is insufficient, it is enhanced later. Because it is possible.

The outputs of the positive side extraction circuits 31 and 32 are multiplied by the multiplication circuit 35, the outputs of the positive side extraction circuits 32 and 33 are multiplied by the multiplication circuit 36, and the outputs of the positive side extraction circuits 33 and 31 are multiplied by the multiplication circuit 37. Is multiplied by each of the multiplication circuits 35, 36, 37
The outputs of are added by the adder circuit 38. Then, the arithmetic circuit 39 subtracts the output of the adder circuit 38 from the output of the color difference signal synthesizing circuit 34, and outputs it as the gain control signal from the output terminal 40.

According to the above configuration, the color difference signals R-Y, R-Y are output from the positive side extraction circuits 31, 32, 33, respectively.
The positive side of BY and G-Y is extracted, and the output of the multiplication circuit 35 that multiplies the positive sides of RY and BY becomes a signal indicating the amount of color in the magenta direction, and BY and G-Y. The output of the multiplication circuit 36 that multiplies the positive side with Y becomes a signal indicating the amount of color in the cyan direction, and the output of the multiplication circuit 37 that multiplies the positive side of G-Y and RY has the color of the yellow direction. It becomes a signal indicating the quantity.

That is, regarding the multiplication circuit 35,
In the case of a color in the green direction, both RY and BY are negative, and the result of multiplying the positive side (that is, both are zero) is zero. In the case of yellow and red, B-
Y becomes negative and the result of multiplication on the positive side (that is, zero) is zero. Furthermore, in the case of cyan or blue, R
-Y becomes negative and the result of multiplying its positive side (that is, zero) is zero. Only in the case of magenta, RY and BY
Since both and become positive, an output is generated in the multiplication circuit 35.

The output of the multiplying circuit 35 becomes maximum when the color is near magenta, and becomes smaller when the color is closer to red or blue. RY axis or B as seen from magenta
The output of the multiplication circuit 35 is zero for colors farther from the -Y axis. In this way, the output of the multiplication circuit 35 is obtained by detecting the amount of color in the magenta direction. Similarly, the multiplication circuit 3
The output of 6 is obtained by detecting the amount of color in the cyan direction, and the output of the multiplication circuit 37 is obtained by detecting the amount of color in the yellow direction.

The output of the adder circuit 38, which is a combination of the outputs of the multiplying circuits 35, 36, and 37, becomes a signal corresponding to the density of magenta, cyan, or yellow color. By adding or subtracting this signal to or from the original gain control signal output from the color difference signal synthesizing circuit 34 to generate a new gain control signal, fine control can be performed unlike the prior art.

For example, the color difference signal synthesizing circuit 34 is configured as shown in FIG. 7, and in the addition in the adding circuit 38, the output of the multiplying circuit 36 is added slightly larger and the output of the multiplying circuit 37 is added slightly, and the multiplying circuit 37 is added. If the output of 35 is subtracted and the color difference signals R-Y, BY, and G-Y are selected in the same manner as described above, the magnitude of the gain control signal obtained from the output terminal 40 depends on the characteristics of the conventional circuit. In comparison, yellow has a slightly larger size, magenta has a slightly smaller size, cyan has a larger size, and blue, red, and green have almost the same characteristics.

That is, not only the luminance signal deteriorated by the color television system is simply corrected, but also yellow, which is low in eye sensitivity, is emphasized a little more to suppress magenta which is apt to be conspicuous of noise, thereby enhancing the effect of emphasis. Large cyan is emphasized, and blue, red, and green are corrected as usual, and very convenient image quality correction can be performed.

Further, since noise is more noticeable in a VTR than in a television broadcast, it is possible to suppress the emphasis amount in the VTR in the magenta where the noise is most noticeable in the VTR than in the television. Further, when it is desired to express a more vivid image, it is possible to emphasize only cyan. Also, in the conventional system, it was possible to emphasize red, but when red was emphasized, magenta and yellow were also emphasized by being drawn to it.
In the case of this embodiment, when red is emphasized, magenta and yellow can be suppressed, and as a result, only red can be emphasized.

Although the embodiment shown in FIG. 1 seems to be a complicated circuit including a large number of multiplication circuits, in the case of an analog circuit, the multiplication circuit can be easily constructed by a double balance circuit, so that the IC (integrated circuit) is integrated. Considering circuitization, there is almost no difference in cost compared with the circuit shown in FIG.

FIG. 2 shows a second embodiment of the present invention. The same parts as those in FIG.
Outputs of the positive side extraction circuits 32 and 33 are added by an addition circuit 41, the added output is multiplied by the output of the positive side extraction circuit 31 by a multiplication circuit 42, and the multiplication output is supplied to an arithmetic circuit 39. Is.

That is, the circuit shown in FIG. 1 is simplified a little, and in order to downsize the circuit, the control for one color in FIG. Of course, it is better to be able to control more colors as shown in FIG. 1, but if one color can be compromised, it can be simplified as shown in FIG.

That is, the color difference signals R-Y, B-Y, and G-Y.
In multiplying each of the two, first two color difference signals B
-Y, G-Y are added, and the remaining one color difference signal R
-Y is being multiplied. As a result, it is the same as creating two multiplication signals, but the addition circuit is preferable to the use of two multiplication circuits because the addition circuit has a simpler circuit configuration than the multiplication circuit.

If the color difference signal synthesizing circuit 34 is configured by an adding circuit instead of the configuration of the maximum value circuit shown in FIG. 7,
Since the control amounts for yellow, cyan, and magenta are larger than the control amounts for blue, red, and green, the color-difference signal synthesizing circuit 34 is used as an adding circuit in the configuration shown in FIG. When the output (magenta, cyan) of the circuit 42 is subtracted, a gain control signal for suppressing magenta is obtained at the output terminal 40 by emphasizing yellow and cyan as compared with the characteristics of the conventional circuit. be able to.

FIG. 3 shows a third embodiment of the present invention. The same parts as those in FIG.
The outputs of the positive side extraction circuits 31 and 32 are multiplied by the multiplication circuit 43 and the multiplication output is supplied to the arithmetic circuit 39. The circuit shown in FIG. 2 is further simplified and only the multiplication signal of one color is used. It was done. In this case, although the degree of freedom is increased by one as compared with the conventional circuit, in addition to the correction of the deterioration of the luminance signal, it is possible to add one feature such as enhancing cyan or suppressing magenta. ..

FIG. 4 shows a circuit for correcting the high frequency component of the luminance signal by using the gain control signal obtained by the circuits of the above-mentioned first to third embodiments. That is, the color signal supplied to the input terminal 44 is supplied to the color demodulation circuit 45 and demodulated into three types of color difference signals R-Y, G-Y, and B-Y. Demodulated color difference signals R-Y, G-Y, and B-Y
Are taken out from the output terminals 46, 47 and 48, respectively, and are supplied to the saturation detection circuit 49 having the circuit configuration shown in the first to third embodiments to obtain a gain corresponding to the saturation of the television signal. It is used to generate a control signal.

On the other hand, the luminance signal supplied to the input terminal 50 is supplied to a BPF (band pass filter) 51 and a delay circuit 52 as an all pass filter. BP
The output of F51 is a variable gain circuit 53 whose gain is variable based on the gain control signal output from the saturation detection circuit 49.
As a result, the image portion with higher saturation is amplified so as to be emphasized, and then added to the output of the delay circuit 52 in the adder circuit 54 and taken out from the output terminal 55.

The difference from the conventional circuit shown in FIG. 6 lies in the filter portion. In the conventional circuit, the brightness signal is HPF1.
9 is separated from the LPF 20, and the output of the HPF 19 is controlled and then added to the output of the LPF 20. However, in the example of FIG.
F19 is BPF51. The point is that the amount of high-frequency components of the luminance signal is variable according to the saturation, so either method of dividing the luminance signal into bands may be used, but if an LPF is interposed in the luminance signal path, the phase can be changed. Is changed, the addition circuit 54 cannot perform accurate addition, and as a result, the output characteristic of the luminance signal obtained from the output terminal 55 becomes undesired.

In the case of the conventional circuit shown in FIG. 6, it is extremely difficult to make the group delay characteristic of the luminance signal flat, and it has extra preshoot and overshoot. H
The same applies to the case where the phase rotation occurs in the PF 19, and here too, there are extra preshoots and overshoots.

In the configuration shown in FIG. 4, if the main signal of the luminance signal is passed through the delay circuit 52 as an all-pass filter, there is almost no adverse effect on the main signal and extra preshoot and overshoot are added. There is no end. Further, the reason why the BPF 51 is used instead of the HPF 19 is to avoid extra preshoot and overshoot. The BPF 51 can be realized by a transversal filter using a delay circuit. The transversal filter has a flat group delay characteristic and does not have extra preshoot or overshoot.

If the delay circuit for the transversal filter used in the BPF 51 and the delay circuit 52 have the same characteristics, the time difference between the two input signals input to the adder circuit 54 becomes almost completely the same. The addition circuit 54 can perform ideal addition, and the image quality can be improved in a very desirable manner. In particular, in a digital system, the delay circuit can be realized with extremely high precision and easily, which is effective in terms of both characteristics and ease of realization. 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.

[0044]

As described in detail above, according to the present invention,
In addition to correcting the resolution of the deteriorated luminance signal,
It is possible to provide a very good image signal processing device that enables fine control for each hue and contributes to image quality improvement.

[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 diagram showing a second embodiment of the present invention.

FIG. 3 is a block configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a block diagram showing an application example of the present invention.

FIG. 5 is a block configuration diagram showing a conventional image signal processing device.

FIG. 6 is a circuit configuration diagram showing a conventional saturation detection circuit.

FIG. 7 is a characteristic diagram showing the degree of deterioration of a luminance signal with respect to saturation.

[Explanation of symbols]

11 ... Input terminal, 12 ... Color amplification circuit, 13 ... Color demodulation circuit, 14-16 ... Output terminal, 17 ... Saturation detection circuit, 18
... Delay circuit, 19 ... HPF, 20 ... LPF, 21 ... Gain variable circuit, 22 ... Adder circuit, 23 ... Output terminal, 24-2
6 ... Input terminal, 27 ... Output terminal, 28-30 ... Input terminal, 31-33 ... Positive side extraction circuit, 34 ... Color difference signal composition circuit, 35-37 ... Multiplication circuit, 38 ... Addition circuit, 39 ... Arithmetic circuit, 40 ... Output terminal, 41 ... Addition circuit, 42, 43
... multiplication circuit, 44 ... input terminal, 45 ... color demodulation circuit, 46
˜48 ... Output terminal, 49 ... Saturation detection circuit, 50 ... Input terminal, 51 ... BPF, 52 ... Delay circuit, 53 ... Gain variable circuit, 54 ... Addition circuit, 55 ... Output terminal.

Claims (1)

[Claims] 1. A control signal according to the saturation of a chromatic color image by multiplying the positive side of a plurality of color difference signals by multiplication and calculating the multiplication output and the combined output of the positive side of the plurality of color difference signals. , A 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, and this gain. An image signal processing apparatus comprising: an addition unit that adds a high frequency component of a luminance signal output from a variable unit and a main component of the luminance signal.