JPS6187493A - Device for improving color television picture quality - Google Patents

Abstract

PURPOSE:To improve a picture quality of a TV receiver, especially, a large-sized projection video tube by constituting a titled device so that both a contour correction and a flare correction are executed. CONSTITUTION:A digital luminance signal Y is supplied to a correcting signal generating circuit 3. On the other hand, as for digital video signals Y, C1 and C2, they are delayed by the time of an about one frame portion, which is required for generating a correcting signal by the circuit 3, by frame delaying circuits 4a-4c and line delaying circuits 5a-5c. The delayed signals Y, C1 and C2 are converted to digital video signals R, G and B of three primary colors by a matrix circuit 6. The signals R, G and B are added to a contour correcting signal and a flare correcting signal outputted from the circuit 3 by adding circuits 7a-7c. By this addition, the signals R, G and B to which the contour correction and the flare correction have been performed are restored to analog signals R, G and B by D/A converting circuits 8a-8c.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of the Invention 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 is by displaying high-definition television images on a large screen.

The aim is to give viewers a sense of impact and realism that cannot be obtained with existing television receivers.

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 following paper entitled "Development of CRT-type Display for High-Definition Television", Lecture No. 5PI-15R at the 1982 National Annual Conference of the Television Society of Japan.

In the above-mentioned CRT projection display device, it has been considered 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 of such contour correction, please refer to the paper by Kaida et al. titled ``Digital Contour Corrector for High-Definition Television Cameras'', Lecture No. 12'-2r, 1983 National Annual Conference of the Television Society.

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 interference, please refer to the Television Society of Japan 1982 National Annual Conference Lecture No. 5P-14r.
Improving the image quality of high-definition television projection displays - 3AW
Please refer to the paper by Kanazawa et al. titled "Removal of Flare Interference by Filter."

Problems to be Solved by the Invention When attempting to improve the image quality of a color television receiver such as a projection display device for high-quality color television, the following problems arise.

[A3 The question of whether to perform both contour correction and flare correction or to correct only one of them.There are image quality improvement devices that correct either contour or flare, but there is no image quality improvement device that corrects both. . Whether such an image quality improvement device that simultaneously corrects both contour and flare can be realized in terms of cost/performance can only be determined through experimental production and performance evaluation.

rP! ] The video signal is 1ft between whether it is realized by an analog circuit or a digital m circuit, and it is supplied as an analog signal, 11
In general, analog circuits are simpler and cheaper than digital circuits.

On the other hand, it is expected to be quite difficult to realize an analog filter having desired frequency characteristics and good phase characteristics necessary for creating a correction signal.

For example, according to the paper by Kanazawa et al. mentioned above, by amplitude modulating a video signal with a high frequency carrier frequency, it is possible to
8,150MH2=20 MH2 is converted into a high frequency/wideband video signal, and 150M of the converted video signal is
A method has been attempted in which horizontal flare correction is performed by demodulating only the upper and lower IM)12 frequency components using a SAW filter by FIP'ing them by about 6 dl'3.

According to the method described in -1-, a reliable effect is achieved in that a simple and inexpensive analog circuit can be used. On the other hand, this method has a problem in that it requires high-frequency signal processing at least north of 1.00 Mtlz. In addition, if this method is applied not only to the horizontal component of flare but also to the vertical component, a large number of one-line delay circuits with extremely high precision similar to that of analog circuits will be required. There is also the problem.

[C] The question of whether or not to realize everything with digital circuits If it is realized with digital circuits, there is a question of whether or not to realize everything with digital circuits, that is, whether or not to make analog parts coexist.

The above-mentioned paper by Kaida et al. discloses a digital contour corrector based on a combined analog method.

That is, of the analog R, G, and B primary color video signals, only the G signal is converted to a digital signal, and a digital contour correction signal is created based on this. The digital m circuit performs digital addition using the digital contour correction signal, and then restores the corrected analog G signal.

On the other hand, the above-mentioned digital ring and correction signal are analog (r'
After being converted to No. 1, the analog signal is added to the original R signal and B signal, which are still analog signals, to obtain corrected analog R and B signals.

What is the combination of analog processing and digital processing mentioned above?

There is also a problem between contour correction and flare correction. That is, 2
There is a problem as to whether both should be processed by digital circuits, one and both should be processed by analog circuits, or one should be processed by digital circuits and the other by analog circuits.

If an analog part is included, the circuit becomes simpler and cheaper. On the other hand.

Such an analog combination method has the problem that a delay compensation circuit and the like for compensating the processing time must be implemented with an analog circuit such as an LC circuit. In other words, this type of analog circuit has lower adjustment accuracy than digital circuits, and is more susceptible to temperature fluctuations, so unless high-precision stabilization measures are taken for such analog systems, the characteristics may deteriorate. This includes the problem that a difference in delay time may occur between the system and a stable digital system, which may actually deteriorate the quality of an image.

[D] Other Problems In general, television video signals are processed using analog signals, but there are problems that need to be improved, particularly in the analog signal processing after the video stage, as listed below.

First, in terms of performance, there are various problems caused by processing performance on the two-time axis.For example, the performance of separating luminance signals and chromaticity signals that appear on the screen as cross color and dot interference.

There are various types of image quality improvement performance, etc. On the other hand, from a cost and policy perspective, even if the two circuits are integrated into ICs, there is a problem in that there are many external parts and adjustment points.

Therefore, in recent years, consideration has been given to making the signal processing after the video stage all digital, and an important issue is how to achieve flare correction and contour correction simultaneously using all-digital circuits, especially in terms of image quality improvement performance. There is one.

Structure of the Invention Means for Solving the Problems (1) The image quality improving device of the present invention which solves the problems of the prior art includes: A green signal of a digital video signal consisting of a primary color signal or a luminance signal and two color signals. , a correction signal generation circuit for image quality improvement that generates a correction signal for image quality improvement including one contour correction signal and a flare correction signal based on the luminance signal or all of the signals; and a delay compensation circuit that delays each of the digital video signals by a predetermined time. , a digital addition circuit that adds the image quality improvement correction signal to the delayed digital video signal, and a D/8 conversion circuit that converts the added digital video signal into a corresponding analog three primary color signal. has been done.

In a preferred embodiment of the present invention, the nine image quality improvement correction signal generation circuits are configured to generate an edge correction signal and a flare correction signal from the digital luminance signal, and these correction signals are added to the three primary color signals.

In a further preferred embodiment of the present invention, the nine image quality improvement correction signal generation circuits are composed of contour correction signal generation means and flare correction signal generation means, and each signal generation means includes a low-pass filter for low-pass filtering the digital luminance signal. a pass filter circuit; a delay circuit that delays the digital luminance signal by a predetermined amount;
and a digital subtraction circuit for subtracting the low-pass filtered digital luminance signal from the delayed digital luminance signal.

In a preferred embodiment of the invention, separate contour correction signal generation means and flare correction signal generation means are installed in parallel with each other, each correction signal generation means having a.

It is configured to include a low-pass filter circuit for creating a vertical correction signal and a low-pass filter circuit for creating a horizontal correction signal, which are installed in series with each other.

Hereinafter, the operation 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, 1axl-c is A/
2 is an inverse matrix circuit 53 is a correction signal generating means, 4a to 4C are frame delay circuits, 5a to 5C are line delay circuits, 6 is a matrix circuit, 7a to 7C are adder circuits, 8a to 8C are n/ In the A conversion circuit, 9a to 9C are output terminals.

Each of the A/D conversion circuits Pr1a to IC receives a color signal R from 9 color demodulation circuits to high-definition television analog: 15.
, G, and B are supplied. These analog video signals T? ,
After being sampled at a predetermined sampling frequency by the A/D conversion circuit 1a to IC, G and R are sampled at a predetermined sampling frequency.
It is converted into a bit digital signal. The RlG and R signals converted into digital signals are converted into a digital luminance signal Y and two types of color signals CI and C in an inverse matrix circuit 2.
Converted to 2.

These color signals CI and C2 are wideband color signals (Cw), respectively, in the case of a high-definition television signal.

This corresponds to what is called a narrowband color signal (C8).

In addition, in the case of N, TSC signal, one color signal C] is (R-
Y) corresponds to what is called a signal or I signal and is a one-color signal C
2 corresponds to what is called a (B-Y) signal or a 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 of R, G, and H can be restored from these and the luminance signal Y. There may be.

The digital luminance signal Y is supplied to the input terminal 3b of the supplementary signal generation circuit 3. On the other hand, digital video signals Y, C
1 and C2, frame delay circuits 4a to 4C and line delay circuits 5a to 5C each consisting of a RAM, etc.
The correction signal generation circuit 3 is delayed by approximately one frame's worth of time required to generate the correction signal. At this time, the luminance signal Y delayed by approximately one frame in the frame delay circuit 4a is supplied to the input terminal 3a of the correction signal generation circuit 3.

The delayed video signals Y, CI, C2 are converted into three primary color digital video signals R, G, B in the matrix circuit 6.
is converted to Each of the digital video signals R, G, and H is added to the contour correction signal and the flare complementary IF signal supplied from the output terminal 3C of the complementary 1-2 signal generating circuit 3 in addition circuits 73 to 7C. This addition results in digital video signals R, G that have been subjected to 1 contour correction and flare correction.
,P.

are restored to analog video signals R, G, and H in the D/Δ conversion circuits 8a to 8C, and outputted to the output terminals 9a to 9C.

FIG. 2 is a block diagram showing an example of the configuration of the correction signal generation circuit 3. As shown in FIG.

The correction signal generation circuit 3 includes a contour correction signal generation circuit 20, a flare correction signal generation circuit 30, and a digital addition circuit 40, which are connected in parallel.

The contour correction signal creation circuit 20 includes an inverted T circuit 21 for canceling the γ correction applied to the digital video signal R, and a series-connected low-pass filter circuit for vertical contour correction vrN, P.
F) Low-pass filter circuit 23 for 22 and horizontal contour complement 1 mode
and a digital subtraction circuit 26.

A delay compensation circuit 41 that delays the phase of the digital video signal R so that the phases of the two inputs of the digital subtraction circuit 26 match, and a coring circuit 27 that also has a γ correction function.
It is composed of.

Similarly, the flare correction signal generation circuit 30 also has an inverted T-time 1-3
1, a vertical flare correction low-pass filter circuit 32 and a horizontal flare correction low-pass filter circuit 33 connected in series,
and a digital subtraction circuit 36.

The coring circuit 37 also includes a gamma correction function.

The correction signal generation circuit 3 of this embodiment uses low-pass filter circuits 22 and 23 for contour correction in the vertical and horizontal directions, and low-pass filter circuits 32 and 33 for flare correction, respectively.
El - Extract the low frequency component of the luminance signal Y.

It is configured to create two contour correction signals and a flare correction signal by subtracting this extracted low-frequency component from the original luminance signal Y delayed by a predetermined time.

In this way, the low-frequency component is extracted and subtracted from the original signal using a high-pass filter circuit to extract the luminance signal Y.
This is to prevent image quality deterioration at the four corners that occurs when extracting each correction signal from the four corners.

The digital luminance signal Y supplied to the input terminal 3a is delayed by approximately one frame compared to the digital luminance signal Y supplied to the input terminal 3b. This is one wheel 91S
This is because the delay time occurring in the correction low-pass filter circuit 20 is shorter than the delay time occurring between the flare correction low-pass filter circuits 30.

Each luminance signal Y supplied to input terminals 3a and 3b has C
γ correction is applied to compensate for the non-white line property of RT's cathode voltage and current. When a correction signal is created from the luminance signal Y with this γ correction + E applied, the correction signal S/N in dark areas of the screen due to loss of linearity
may deteriorate, reducing the effectiveness of the correction.

Therefore, as shown in FIG. 2, the luminance signal Y, which has been subjected to γ correction and has an angle of 11°, has its one-per-day correction canceled by the inverse γ addition correction circuits 21 and 31 consisting of ROM, and the amount of light received by the imaging device is adjusted accordingly. After being restored to values having a linear relationship, they are supplied to contour correction low-pass filter circuits 22 and 23 and flare correction low-pass filter circuits 32 and 33, respectively. The outputs of the low-pass filtering circuit 23 for horizontal contour correction and the low-pass filtering circuit 33 for horizontal flare correction are sent to subtraction circuits 26 and 3, respectively.
6, it is subtracted from the luminance signal Y that has passed through the intermediate tap 22a of the vertical contour correction low-pass filter circuit 22 and the delay compensation circuit 4J. The delay compensation circuit 41 includes subtraction circuits 26 and 3.
The luminance signal Y taken out from the intermediate tap 22a of the vertical contour compensation low-pass filter circuit 22 is delayed so that the two inputs are in phase in each of the vertical contour compensation low-pass filter circuits 22.

Coring circuits 27 and 37 each have a T correction function, and when each of the contour correction signal and flare correction signal created in 1 is below a predetermined level, the respective outputs are set to zero. This suppresses high-frequency noise mixed into the image and prevents deterioration of S/N in dark areas of one screen. An example of the predetermined levels is levels 2 to 60 with respect to the maximum level 256 expressed in 8 bits.

The adder circuit 40 adds and synthesizes the contour correction signal and the flare correction signal that have passed through the coring circuits 27 and 37.

The vertical contour correction low-pass filter circuit 22 and the horizontal contour correction low-pass filter circuit 23 are constructed by two transversal filters, for example, as shown in FIG. This transversal filter includes delay circuits 51a to 51d connected in series to delay the digital luminance signal Y supplied to the input terminal 50 by a predetermined amount, and delay circuits 51a to 51d that delay each digital luminance signal Y by a predetermined amount. It is composed of coefficient circuits 52a to 52e that multiply the value by a predetermined value, and an adder group 53 that adds the outputs of each coefficient circuit according to a predetermined algorithm. Output to.

In the vertical contour correction low-pass filter circuit 224, the delay circuits 5ta to 51d are constituted by line memories that delay the digital digital signal Y by one line. On the other hand, in the horizontal contour correction low-pass filter circuit 23, the delay circuits 51a to 51d are composed of dot memories that delay the digital luminance signal Y by one sampling period.

The vertical flare correction low-pass filter circuit 32 and the horizontal flare correction low-pass filter circuit 33 are two cursive filters 61.6 with the same configuration, as shown in FIG.
It is composed of two time axis inversion circuits 62 and 64 having the same configuration as that of No. 3.

In the above-mentioned contour correction, it is sufficient to perform signal processing between several adjacent sampling points, but the influence of flare generally extends to a very large number of adjacent sampling points. Therefore, if flare processing were to be performed using a transversal filter, an extremely large number of delay circuits, coefficient circuits, and adder circuits would be required, and the scale of the filter would be extremely large. Therefore, a recursive filter is used for flare correction.

In the vertical flare correction low-pass filter circuit 32, the 1-time axis inverting circuits 62 and 64 write the digital luminance signal Y for field (1) and then read it out in the reverse order of the writing. Consists of inverted memory.

On the other hand, in the horizontal contour correction low-pass filter circuit 33, the 1-time axis inversion circuits 62 and 64 write the digital luminance signal Y for one line, and then output the digital luminance signal Y in the reverse order of the above-mentioned writing. It consists of a line inversion memory that is read out. The time axis of the digital luminance signal Y passed through the recursive filter 61 is reversed, and the digital luminance signal Y is passed through the recursive filter 6 again.
3, a linear phase is realized and the phase characteristics are improved.

The recursive filters 6I and 62, as exemplified by the recursive filter 61,
~70c, delay circuits 712~7]C, and coefficient circuit 72
It is composed of 3 to 72C. Delay circuits 71a-71
c is a cursive filter for vertical flare correction,
It consists of a line memory that gives a delay of one line to the digital luminance signal Y, while the cursive filter for horizontal flare correction consists of a dot memory that gives a delay of one sampling period to the digital luminance signal Y.

FIG. 5 shows an example of the contour correction signal outputted from the subtraction circuit 26 in terms of spatial frequency characteristics (MTF). The level of the contour correction signal is zero up to 100 TV lines, and can increase linearly at a rate of approximately 12 dB/200 lines as the spatial frequency increases from 100 TV lines to 300 TV lines, and above 300 TV lines, the level of the original luminance signal than 1
It can increase up to 2 dB greater level.

FIG. 6 shows an example of the flare correction signal output from the subtraction circuit 36 in terms of spatial frequency characteristics.1. It's ours. The level of the flare correction signal is zero up to 15 TV trees and 12
TV lines to 30 TV lines can increase linearly with increasing spatial frequency at a rate of approximately 6 dB/15 TV lines, and 3
Above 0 TV lines, the level can increase to 6 dB higher than the cool luminance signal.

Figure 7 shows the transversal filter in Figure 3 and the transversal filter in Figure 4.
FIG. 2 is a block diagram showing an example of the configuration of a coefficient circuit used in the cursive filter.

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

CP IJ is 1. For example, during the vertical blanking period when the screen is not displayed, the selector 81 is commanded to select a CPIJ address, and the CPU address whose value gradually increases is set to this CP IJ address. CPIIDATA multiplied by a predetermined coefficient is repeatedly output. This CP tJ n A T8 is RAM82
The data is supplied to the data write terminal Din of the CP11 address and written to 256 areas specified by the CP11 address. CPt
When J finishes writing the above-mentioned coefficients, r
) ATA (Commands the selection of brightness (A No. Y). After this, when the RAM 82 is addressed by the brightness signal Y,
The luminance signal Y multiplied by the coefficient is output as r') A T A out from the data output terminal Dout.

Above, we have illustrated the configuration for creating the contour correction signal and flare correction signal from the luminance signal Y. However, correction signals for the luminance signal and two types of color signals or the three primary color signals R, G, and R are created independently and added. It is also possible to close the configuration. Further, instead of the luminance signal, each correction signal may be created from the G signal that contributes most to the luminance signal.

In addition, although we have illustrated a configuration in which an analog video signal is converted into a digital video signal using a Δ/D conversion circuit, if the video signal whose image quality is to be improved has already been digitized, Of course, the D conversion circuit can be omitted.

Furthermore, although we have illustrated a configuration in which the luminance signal and two color signals are corrected using a correction signal created based on the digital luminance signal, it is also possible to simplify the configuration by correcting only the N degree signal. .

In addition, in a configuration that creates a correction signal based on the green signal,
All three primary color signals may be corrected using this correction signal, or the configuration may be simplified by correcting only the green signal.

Effects of the Invention Since the image quality improving device of the present invention is configured to perform both two-contour correction and flare correction, it has the effect of significantly improving the image quality of the television receiver 3, especially a large projection picture tube.

In addition, the image quality improvement device of the present invention performs contour correction and flare correction using three signals: a brightness signal and two color signals or three primary color signals.
Since the entire system is configured to be processed by digital circuits,
As with the analog combination method where a part of the frame delay circuit or line delay circuit is configured with analog circuits, the effect of improving one image quality may be diminished or the quality of one image may deteriorate due to the difference in delay time between the analog system and the digital system. This has the effect of solving the problem of

[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 3 shown in FIG. 1, and FIG. 3 is a vertical contour correction shown in FIG. 2. FIG. 4 is a block diagram showing an example of the configuration of the low-pass filter circuit 22 for vertical flare correction and the low-pass filter circuit 23 for horizontal contour correction shown in FIG. 2. A block diagram showing an example of the configuration of the low-pass filter circuit 33, FIG. 5 is a characteristic diagram showing an example of the contour correction signal, and FIG. 6 is a block diagram showing an example of the flare correction signal. FIG. 2 is a block diagram showing an example of the configuration of a coefficient circuit in a filter circuit. 1a to IC...A/D conversion circuit, 2...inverse matrix circuit, 3...correction signal creation circuit, 4a to 4C...frame delay circuit, 5a to 5C...line delay circuit, 6...matrix circuit, ? a~7c... Addition circuit, 8a~8C...
・D/A conversion circuit. 93-9c... Output terminal, 20... Contour correction signal creation circuit, 30... Flare correction signal creation circuit, 21.31...
Inverse γ correction circuit, 22...Low pass filter circuit for vertical contour correction, 32...Low pass filter circuit for vertical flare correction, 23
・・Low pass filter circuit for horizontal contour correction, 33・・Low pass filter circuit for horizontal flare correction, 26. 36・・Subtraction circuit, 27° 37・・Coring circuit with T correction function,
40...Addition circuit, 41...Delay compensation circuit. Patent applicant: NEC Home Electronics Co., Ltd.

Claims (1)

[Scope of Claims] Image quality in which a digital image quality improvement correction signal including a contour correction signal and a flare correction signal is created from a green signal, a luminance signal, or all of a digital video signal consisting of three primary color signals or a luminance signal and two types of color signals. an improvement correction signal creation circuit; a delay circuit that delays each of the digital video signals for a predetermined time; a digital addition circuit that digitally adds the digital image quality improvement correction signal to the delayed digital video signal; and after the addition. 1. A color television image quality improvement device, comprising: a digital-to-analog conversion circuit that converts a digital video signal into an analog three-color signal.