JPH0316077B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION Field of Industrial Application The present invention relates to a device for improving the image quality of a color television receiver, particularly a projection display device for high-definition television.

Conventional technology High-definition television displays high-definition television images on a large screen to give viewers a sense of impact and realism that cannot be obtained with existing television receivers. It is something.

A CRT projection display device is being developed as one of such high-definition television display devices. For details of such a CRT projection display device, please refer to the paper by Kubo et al. titled ``Development of CRT type display for high-definition television'', lecture number SP1-15 of the 1982 National Conference of the Television Society.

In the above-mentioned CRT projection display device, it is considered essential to perform contour correction between the camera and the receiver in order to compensate for the decrease in resolution due to the increase in the size of the optical system. For details on such contour correction, please refer to the 1983 National Conference of the Television Society, Lecture No. 12-2.
"Digital contour corrector for high-quality television cameras"
Please refer to the paper by Okada et al.

Further, in the above-mentioned projection display device, large flare interference occurs due to reflected components caused by the projection light passing through the lens multiple times and the finite thickness of the screen. A video signal with large flare is accompanied by an increase in low frequency components. For more information on such flare disturbances, please refer to the Television Society
Please refer to the paper by Kanazawa et al. titled 1982 National Convention Lecture No. SP-14, "Improvement of Image Quality of High-Definition Television Projection Displays - Removal of Flare Interference by SAW Filters."

Problems to be Solved by the Invention An attempt was made to improve the image quality of a color television receiver such as a projection display device for high-definition color television by performing contour correction and flare correction in the horizontal and vertical directions. In this case, it is necessary to extract the following various problems and provide answers to each one, taking into account the relationship with other problems.

[A] The question of whether to implement it with analog circuits or digital circuits Video signals are supplied as analog signals, with some special exceptions, and analog circuits are generally simpler and simpler than digital circuits. It's cheap. Therefore, in terms of circuit scale and cost, it is desirable to implement the above image quality improvement device using an analog circuit.

On the other hand, analog
Considerable difficulty is expected in realizing the filter.

For example, according to the above-mentioned paper by Kanazawa et al., by amplitude modulating a video signal with a high frequency carrier frequency, it is first converted into a high frequency, wideband video signal of about 150 MHz ± 20 MHz, and the converted video signal is A method has been attempted in which horizontal flare correction is performed by attenuating only the frequency components of 1 MHz above and below 150 MHz by about 6 dB using a SAW filter and then demodulating them.

According to the above method, a reliable effect is achieved in that a simple and inexpensive analog circuit can be used. On the other hand, with this method, at least
There is a problem in that high-frequency signal processing of 100MHz or higher is required. In addition, when applying this method not only to the removal of the horizontal component of flare (horizontal flare) but also to the removal of the vertical component (vertical flare), it is necessary to use extremely high-precision one-line delay, which is close to the limit of analog circuits. Another problem is that a large number of circuits are required.

[B] The question of whether to realize everything with a digital circuit If it is realized with a digital circuit, it is related to the question of whether to perform correction for the three primary colors independently, which will be discussed later. There is a question of whether or not the parts should coexist.

The above-mentioned paper by Okada et al. discloses a digital contour corrector based on a combined analog method. That is, of the analog three primary color video signals of R, G, and B, only the G signal is converted into a digital signal, and a digital contour correction signal is created based on this. The digital G signal is digitally added by the digital contour correction signal and then restored to the corrected digital G signal. On the other hand, after the digital contour correction signal is converted into an analog signal,
Analog addition is made to the original R signal and B signal as analog signals, and the corrected analog R signal and B
I get a signal.

In this way, if the analog part coexists,
There is a certain effect that the circuit becomes simpler and cheaper. On the other hand, such a combined analog method has the problem that a delay compensation circuit and the like for compensating the processing time must be implemented using an analog circuit such as an LC circuit.
In other words, this type of analog circuit has lower adjustment accuracy than a digital circuit, and is more susceptible to temperature fluctuations, so unless high-precision stabilization measures are taken for such analog systems, the characteristics will not stabilize. This poses a problem in that there may be a difference in delay time, etc. between the digital system and the digital system, which may even deteriorate the image quality.

[C] The question of whether or not to perform correction independently for the three primary colors Create correction signals for each of the three primary colors R, G, and B, and use these correction signals to correct R, G, and B.
If the configuration is such that the G and B original signals are corrected, the best image quality improvement effect will be achieved.

However, it is expected that there is a considerable correlation between the appearance of contours and the occurrence of flare among video signals of the three primary colors. A method of creating a correction signal may also be possible.

Considering this point, a configuration in which correction is performed independently for the three primary colors requires three independent correction signal generation circuits for R, G, and B, which poses a problem in that the scale and cost of the circuit become excessive. In particular, when implementing all of these correction signal generation circuits and delay compensation circuits digitally, there are problems in terms of circuit scale and cost.

[D] The problem of whether to create a correction signal from the G signal or the Y signal If correction is not performed independently for the three primary colors, there is a problem as to whether to create the correction signal from the G signal or the luminance signal Y. Input signal is R, G, B
If the three primary color signals are the three primary color signals, as described in the paper by Okada et al. mentioned above, if a correction signal is generated from the G signal that contributes the most to the luminance signal,
A reliable effect is achieved in that the step of creating the luminance signal Y by the matrix circuit can be omitted.

On the other hand, this method still has the problem that the correction effect decreases as the G signal component decreases.

[E] The question of whether to apply correction only to the luminance signal If a correction signal is created from the luminance signal,
There is a problem as to whether correction using this correction signal should be applied only to the luminance signal.

A method in which a correction signal created from a luminance signal is added to all three primary colors is more effective in improving image quality than a method in which only the luminance signal is corrected.

On the other hand, the former method has a more complex and expensive circuit configuration than the latter method.

[F] The issue of whether contour correction and flake correction should be processed simultaneously by the same circuit Contour correction is performed by extracting a contour signal from the high-frequency components of the image and adding it to the original image. . Flare correction is performed by suppressing low frequency components of the video signal. Therefore, both contour correction and flare correction have a common aspect of emphasizing high-frequency components of a video signal. Therefore, if both correction processes are performed simultaneously by the same circuit, the number of stages of processing circuits can be halved.

On the other hand, in a configuration in which both correction processes are performed in the same circuit, there is a restriction that the same type of filter circuit must be used for contour correction and flare correction, which is related to [J] described later.

[G] The issue of whether to process contour correction and flare correction in the horizontal and vertical directions in parallel.If contour correction and flare correction are not performed simultaneously in the same circuit, contour correction and flare correction in the horizontal direction , vertical contour correction, and flare correction are required.

Assuming digital processing, a configuration in which all of the above four types of processing are performed in parallel has an excessive effect on improving the average image quality of the screen in that no rounding errors occur.

On the other hand, if you perform horizontal and vertical processing in parallel, you will end up with an angular window.
In patterns etc., the four corners are no longer processed,
It is expected that the image quality of that part will be relatively degraded compared to other parts, and that the uniformity of the image quality of the entire screen will be impaired.

Also, since the times required for the four types of processing above are all different, if all of these processes are performed in parallel, the processing will continue until the vertical flare processing (creating the flare correction signal), which takes the longest time, is completed. There is also the problem that the other three types of correction processing that have already been completed must be delayed, and that the scale of the delay compensation circuit within the correction signal generation circuit is large.

[H] The question of whether or not to process contour correction and flare correction in the horizontal and vertical directions all in series If the above four types of correction processing are all performed in series, as soon as one correction process is completed, the next correction process will be performed immediately. Since processing can be started, there is an advantage that a delay compensation circuit in the correction circuit is not required. Further, if horizontal processing and vertical processing are performed in series, and these processing circuits are constituted by low-pass filter circuits, the problem of image quality deterioration at the four corners described above does not occur.

On the other hand, if a digital circuit is used to implement a system in which all processes are performed in series, rounding errors will accumulate and the accuracy will decrease. As in the case above, there is also the risk that the processing circuit will be difficult to design.

[I] The question of whether or not to use a high-pass filter circuit As mentioned above, contour correction and flare correction both suppress low frequencies and emphasize high frequencies, so a configuration that uses a high-pass filter circuit is straightforward. It is true.

However, in order to prevent the problem that the four corners are not processed as described in [C] above, when performing horizontal processing and vertical processing in series, it is possible to use a high-pass filter circuit. New four-corner problems arise due to different causes. In other words, the level of the four outer corners of the window, whose level has decreased due to horizontal contour correction, increases in level due to the next vertical contour correction, and the image quality improvement effect of only the four corners becomes relatively The problem arises that it worsens and becomes an eyesore.

[J] The question of what kind of filtering circuit to use Especially when performing digital processing, it is necessary to use an acyclic filter (transversal filter) regardless of whether it is a high-pass filtering circuit or not. The problem is whether to use a recursive filter or a recursive filter.

[K] The question of whether to create a correction signal from the original signal that has been γ-corrected The video signal is subjected to γ-correction to compensate for the nonlinearity of the voltage/current characteristics of the CRT cathode. . If a correction signal is created from a video signal that has been subjected to this γ correction, the linearity of the correction signal itself will be lost, causing dark areas (low brightness areas) on the screen.
There is a risk that the S/N ratio in the image will deteriorate and the effectiveness of the correction will decrease.

The main problems encountered in improving image quality by performing contour correction and flare correction in the horizontal and vertical directions have been listed above. According to the inventor's estimate,
Depending on how you answer the various questions above, you will arrive at thousands of different configurations.

Means for Solving the Constituent Problems of the Invention The image quality improving device of the present invention, which solves the problems of the prior art described above, provides an image quality improvement device based on a digital luminance signal of a digital video signal consisting of a luminance signal and two types of color signals. a correction signal generation circuit for image quality improvement that generates a digital image quality improvement signal including a correction signal and a flare correction signal; a delay circuit that delays each of the digital luminance signal and the two types of digital color signals by a predetermined time; A digital addition circuit that adds the digital image quality improvement signal to the digital luminance signal, and converts the delayed image quality improved digital luminance signal and the two delayed digital color signals into red, blue, and green analog video signals. and a means for doing so.

In one embodiment of the present invention, the image quality improvement correction signal creation circuit includes: a low-pass filter circuit that low-pass filters the digital luminance signal; a delay circuit that delays the digital luminance signal for a predetermined time; and a subtraction circuit that subtracts the low-pass filtered digital luminance signal from the delayed digital luminance signal, thereby creating a high-frequency correction signal.

In one embodiment of the present invention, the low-pass filter circuit includes a vertical contour correction low-pass filter circuit and a horizontal contour correction low-pass filter circuit connected in series, and a vertical flare correction low-pass filter circuit connected in series. A low-pass filter circuit and a low-pass filter circuit for horizontal flare correction are provided, and the low-pass filter circuit for vertical contour correction and the low-pass filter circuit for vertical flare correction are connected to a transversal filter that shares a tap. configured.

Hereinafter, the effects of the present invention will be explained in detail by way of examples.

Embodiment FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

In the image quality improvement device of this embodiment, 1a to 1c
are input terminals, 2a to 2c are A/D conversion circuits, 3 is an inverse matrix circuit, 4 is a correction signal generation circuit, 5a
5C is a delay compensation circuit, 6 is a digital adder circuit, 7 is a matrix, and 8a to 8c are D/A conversion circuits 9a to 9c are output terminals.

Analog video signals R, G, and B for high-definition television are supplied to the input terminals 1a to 1c, respectively. These analog video signals R, G, B are
After being sampled at a predetermined sampling frequency by A/D conversion circuits 2a to 2c, it is converted into, for example, an 8-bit digital signal.

The digital video signals R, G, and B are converted into a digital luminance signal Y and two types of digital color signals C1 and C2 in an inverse matrix circuit 3. 2
In the case of a high-definition color television signal, the different color signals C1 and C2 correspond to what is called a wideband color signal (Cw) and a narrowband color signal (C _N ), respectively.
In the case of NTSC color television signals,
The color signal C1 corresponds to what is called a (RY) signal or I signal, and the color signal C2 corresponds to what is called a (B-Y) signal or Q signal. In short, the two types of color signals C1 and C2 may be any suitable signal other than the above-mentioned signals as long as the three primary color signals R, G, and B can be multiplexed from these and the luminance signal Y.

The converted digital luminance signal Y is supplied to the correction signal generation circuit 4. On the other hand, each of the digital luminance signal Y and color signals C1 and C2 is stored in a RAM.
The correction signal generation circuit 4 is delayed by approximately one frame and several lines of time required to generate the complementary signal by the delay compensation circuits 5a to 5c.

The digital correction signal output from the correction signal generation circuit 4 is added to the delayed luminance signal Y in the digital addition circuit 6. The delayed and corrected digital luminance signal Y and the delayed color signals C1 and C2 are converted into three primary color digital video signals R, G, and B in the matrix circuit 7. These digital video signals R, G, B are
In the D/A conversion circuits 8a to 8c, the analog video signals R, G, and B are restored and sent to the output terminals 9a to 9.
It is output to c.

In preparation for receiving an analog luminance signal Y and two types of color signals C1 and C2, the device of this embodiment includes:
A matrix circuit 10 for converting these into corresponding digital video signals, and a switching circuit 11 for selecting one of the output of this matrix circuit 10 and the output of the inverse matrix circuit 3 are provided as necessary.

FIG. 2 is a block diagram showing the configuration of the correction signal generating circuit 4. As shown in FIG.

The correction signal creation circuit 4 includes an inverse γ circuit 21 for canceling γ correction applied to the digital luminance signal Y supplied to the input terminal 4a, a low-pass filtering circuit (LPF) 22 for vertical contour/flare correction, and a horizontal Low-pass filter circuit 23 for contour correction, low-pass filter circuit 24 for horizontal flare correction, digital subtraction circuit 27,
28, 2 of each of these subtraction circuits 27 and 28
Delay compensation circuits 25 and 26 and subtraction circuits 27 and 28 that delay the digital signals by a predetermined time so that the phases of the digital signals supplied to the input terminals match.
Apply γ correction again to the correction signal output from γ
Correction circuits 29, 30, coring circuits 31, 32
and an addition circuit 33.

In the correction signal generation circuit 4 of this embodiment, the vertical contour/flare correction low-pass filter circuit 22 serves as a low-pass filter circuit for vertical contour correction and a low-pass filter circuit for vertical flare correction. . The vertical contour correction section of the low-pass filter circuit 22 and the low-pass filter circuit 23 for horizontal contour correction are connected in series. Similarly, the low pass filter circuit 22
The vertical flare correction section and the horizontal flare correction low-pass filter circuit 24 are connected in series.

Vertical contour/flare correction low-pass filter circuit 22
and the low-pass filter circuit 23 for horizontal contour correction,
Once, the low-frequency component of the luminance signal Y for contour correction is extracted. This extracted low-frequency component for contour correction is subtracted by a subtraction circuit 27 from the original luminance signal Y, which has been rendered in phase by delay compensation circuits 25 and 26, to create a high-frequency contour correction signal.

Similarly, the vertical contour/flare correction low-pass filter circuit 22 and the horizontal flare correction low-pass filter circuit 2
4, the low frequency component for flare correction of the luminance signal Y is once extracted. This extracted low-frequency component for flare correction is subtracted from the original luminance signal Y, which has been made in phase by the delay compensation circuit 25, in a subtraction circuit 28 to create a high-frequency flare correction signal.

The structure of creating a high-frequency correction signal by extracting low-frequency components and subtracting them from the original signal was created by connecting high-pass filter circuits for vertical correction and horizontal correction in series. This is to prevent image quality deterioration at the four corners that would occur when a high-frequency correction signal is directly created using a high-frequency correction signal.

The luminance signal Y supplied to the input terminal 4a includes:
Gamma correction is applied to compensate for the nonlinearity of the voltage/current characteristics of the CRT cathode. If a correction signal is created from the luminance signal Y that has been subjected to this γ correction, the effect of the correction may be reduced due to the above-mentioned nonlinearity.

Therefore, as shown in FIG. 2, the γ-corrected luminance signal Y is temporarily de-corrected by an inverse γ-correction circuit 21 consisting of a ROM, etc., and has a linear relationship with the amount of light received by the imaging device. is restored to a value with .
A contour correction signal and a flare correction signal are created from the luminance signal Y from which the γ correction has been canceled, and these correction signals are sent to the γ correction circuits 29 and 30, respectively.
After being corrected, they are supplied to coring circuits 31 and 32, respectively.

The coring circuits 31 and 32 reduce high-frequency noise mixed into the correction signal by setting their respective outputs to zero when each of the created contour correction signal and flare correction signal is below a predetermined level. This prevents S/N deterioration in dark areas of the screen. An example of the predetermined levels is levels 2 to 6 with respect to the maximum level 256 expressed in 8 bits.

The cored contour correction signal and flare correction signal are digitally added in an adder circuit 33 and supplied to an output terminal 4b.

FIG. 3 is a block diagram showing an example of the configuration of the vertical contour/flare correction low-pass filter circuit 22 of FIG. 2. In FIG. The vertical contour/flare correction low-pass filter circuit 22 is composed of a transversal filter in which the contour correction section and the flare correction section share a tap.

The digital luminance signal Y supplied to the input terminal 40 is supplied to a delay circuit group 41. The delay circuit group 41 includes delay circuits 41a, 41b, and 41c in which one-line delay elements (Z ^-1 ) that provide one-line delay to the digital luminance signal Y are connected in series.
and an n-line delay element (Z ^-n ) that provides a delay of n (integer) lines to the digital luminance signal Y.
It is composed of 41d and 41e. Delay circuit 4
A luminance signal whose delay amount is shifted by one line is supplied to the vertical contour correction coefficient circuit group 42 from a tap provided between each one-line delay element 1b.

The outputs of the vertical contour correction coefficient circuit group 42 are added in a vertical contour correction adder group 43 according to a predetermined algorithm, and a low frequency component for vertical contour correction is extracted. The extracted low-frequency components are sent to the output terminal 44.
is supplied to a low-pass filter circuit 23 for horizontal contour correction.

On the other hand, the luminance signals taken out from the respective taps of the delay circuits 41a, 41b, and 41c pass through the vertical flare correction coefficient circuit group 45, and are added in accordance with a predetermined algorithm in the vertical flare correction adder group 46. Low frequency components for flare correction are extracted. The extracted low-frequency components are supplied from the output terminal 47 to the horizontal flare correction low-pass filter circuit 24. Further, the output of the output terminal 46 is supplied to the delay compensation circuit 25 shown in FIG.

As shown in FIG. 3, signal processing between several adjacent lines is sufficient for contour correction, but the influence of flare generally extends to a large number of adjacent lines. Therefore, the flare correction section requires a delay circuit group with a larger number of stages and a larger number of coefficient circuits and adders than the contour correction section, and the scale of the filter becomes larger.
Therefore, in order to reduce the size of the filter by omitting the intermediate tap even if it sacrifices some characteristics, n-line delay elements 41d and 41e are included in the delay circuit group 41.
is used.

Low-pass filter circuit 23 for horizontal contour correction in Fig. 2
is constituted by a transversal filter in which the 1-line delay element in the vertical contour correction section of the transversal filter shown in FIG. 3 is replaced with a 1-sampling time delay element.

Similarly, the horizontal flare correction low-pass filter circuit 24 in FIG.
It can be constructed with a transversal filter replaced by a sampling time delay element. Alternatively, the low-pass filter circuit 24 for horizontal flare correction
may be constituted by a recursive filter as illustrated in FIG.

In FIG. 4, the horizontal flare correction low-pass filter circuit 24 is composed of two recursive filters 61 and 63 with the same configuration and two time axis inversion circuits 62 and 64 with the same configuration. .

The time axis inverting circuits 62 and 64 are constituted by line inverting memories in which one line of digital luminance signal Y is written and then read out in the reverse order of the writing. The phase characteristics are improved by inverting the time axis of the digital luminance signal Y passed through the recursive filter 61 and passing it through the recursive filter 63 again to achieve a linear phase.

The recursive filters 61 and 63 include adder circuits 70a to 70c and delay circuits 71a to 71, as exemplified by the recursive filter 61.
c, and coefficient circuits 72a to 72c. The delay circuits 71a to 71c are composed of dot memories that provide a delay of one sampling period to the digital luminance signal Y.

FIG. 5 shows an example of the contour correction signal output from the subtraction circuit 27 in FIG. 2 as a spatial frequency characteristic (MTF).
This is what is shown. The level of the contour correction signal is
It is zero up to 100 TV books, and from 100 TV books
Up to 300 TV lines, as the spatial frequency increases,
Can increase linearly at a rate of 12dB/200 lines, 300TV
The signal can increase to a level 12 dB higher than the original luminance signal.

FIG. 6 shows an example of the flare correction signal output from the subtraction circuit 28 of FIG. 2 in terms of spatial frequency characteristics. Flare correction signal level is 15TV
From 12 TV lines to 30 TV lines, it can increase linearly at a rate of approximately 6 dB/15 TV lines as the spatial frequency increases, and above 30 TV lines it can increase to a level 6 dB greater than the original luminance signal. .

FIG. 7 is a block diagram showing an example of the configuration of a coefficient circuit used in the transversal filter of FIG. 3 and the recursive filter of FIG. 4.

This coefficient circuit is composed of a selector 81 and a RAM 82.

For example, the CPU selects the selector 81 during the vertical blanking period when the screen is not displayed.
A CPU that commands the selection of a CPU address and multiplies the CPU address whose value increases gradually by a predetermined coefficient to be set to this CPU address.
Output DATA repeatedly. This CPU DATA
is supplied to the data write terminal Din of the RAM 82 and written into 256 areas specified by the CPU address. When the CPU finishes writing the coefficients, it instructs the selector 81 to select DATA (luminance signal Y). After this, when the RAM 82 is addressed by the luminance signal Y, its data output terminal
From Dout, the luminance signal Y multiplied by the coefficient is
Output as DATA out.

In this way, by configuring the coefficient circuit with RAM, calculation speed is improved compared to configuring it with ROM or multipliers, etc., and correction can be made by changing the coefficient value at the adjustment stage during manufacturing or during use. Characteristics can be adjusted.

Instead of configuring the coefficient circuit with RAM as described above, it may be configured with a combination of ROM, multiplier, bit shifter, and adder.

Furthermore, instead of adding the inverse γ correction circuit and the γ correction circuit, a nonlinear correction circuit may be added that nonlinearly corrects the level of the correction signal according to the level of the luminance signal to be corrected.

Furthermore, in FIG. 2, the A/D conversion circuit 2a
2c and the inverse matrix circuit 3 may be interchanged, and similarly the matrix circuit 7 and the D/A conversion circuits 8a to 8c may be interchanged.

In addition, although we have illustrated a configuration in which image quality is improved by converting an analog video signal into a digital video signal using an A/D conversion circuit, if the video signal whose image quality should be improved has already been digitized, Of course, a /D conversion circuit is not required.

Effects of the Invention As explained in detail above, the image quality improvement device of the present invention is configured to create an edge correction signal and a flare correction signal from the luminance signal Y, so the above correction is performed from each of the three primary color signals R, G, and B. The effect is that the circuit scale can be reduced to approximately one-third compared to the case where signals are created.

Furthermore, since the image quality improvement device of the present invention is configured to create an edge correction signal and a flare correction signal based on the luminance signal Y, the level of the G signal is reduced as in the case where each correction signal is created from the G signal. This is advantageous in that the problem that the effect of improving image quality deteriorates as the image quality increases increases.

Since the image quality improvement device of the present invention is configured to process all three systems of the luminance signal Y and two types of color signals C1 and C2 using digital circuits, part of the frame delay circuit and line delay circuit is configured using analog circuits. It is possible to solve the problem of the effect of image quality improvement being diminished or the image quality even deteriorating due to the difference in delay time between the analog system and the digital system, as in the analog combined system.

Since the image quality improvement device of the present invention is configured to correct only the luminance signal Y using the correction signal created from the luminance signal Y, the circuit is simpler than when also correcting the color signals C1 and C2. The effect of becoming.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing an example of the configuration of the correction signal generation circuit 4 in FIG. 1, and FIG. FIG. 4 is a block diagram showing an example of the configuration of the low-pass filter circuit 22 for correcting flare, FIG. 4 is a block diagram showing an example of the configuration of the low-pass filter circuit 24 for horizontal flare correction shown in FIG. 2, and FIG. FIG. 6 is a characteristic diagram showing an example of a correction signal, FIG. 6 is a characteristic diagram showing an example of a flare correction signal, and FIG. 7 is a block diagram showing an example of the configuration of a coefficient circuit in a filter circuit. 1a to 1c...input terminal, 2a to 2c...A/D conversion circuit, 3...inverse matrix circuit, 4...correction signal generation circuit, 5a to 5c...delay compensation circuit, 6...digital addition circuit, 7...matrix circuit, 8a-8
c...D/A conversion circuit, 9a-9c...output terminal, 2
2...Low-pass filter circuit for vertical contour/flare correction,
23...Low-pass filter circuit for horizontal contour correction, 24...
Low-pass filter circuit for horizontal flare correction, 27, 28
...Subtraction circuit.

Claims (1)

[Scope of Claims] 1. An image quality improvement correction signal generation circuit that generates a digital image quality improvement correction signal based on a digital luminance signal of a digital video signal consisting of a luminance signal and two types of color signals, which are connected in series. a low-pass filter circuit for vertical contour correction, a low-pass filter circuit for horizontal contour correction, and a low-pass filter circuit for vertical flare correction and a low-pass filter circuit for horizontal flare correction connected in series; a delay circuit that matches the phase of the filtered digital luminance signal with the phase of the digital luminance signal before low-pass filtering; a subtraction circuit for subtracting from a signal; a delay circuit for delaying the digital luminance signal and two types of digital color signals by a predetermined time; and a digital circuit for adding the digital image quality improvement signal to the delayed digital luminance signal. The present invention further comprises: an adding circuit; and means for converting the digital luminance signal to which the delayed digital image quality improvement signal is added and the delayed two types of digital color signals into analog video signals of red, green, and blue. A color television image quality improvement device with special features. 2. The low-pass filter circuit for vertical contour correction and the low-pass filter circuit for vertical flare correction have multiple stages of one-line delay element groups connected in series, and a signal extracted from between the stages of these one-line delay element groups. It is characterized by comprising a group of coefficient units for multiplying by coefficients and a group of adders for adding the outputs of these groups of coefficient units, and a part of the one-line delay element group is composed of a transversal filter shared between the two. A color television image quality improvement device according to claim 1.