JPH03104410A - Waveform equalizer, picture device provided with the waveform equalizer and transversal filter for the waveform equalizer - Google Patents

Abstract

PURPOSE:To attain other picture quality correction processing of waveform equalizing processing and to obtain desired Picture quality by providing a picture quality correction tap coefficient control circuit to a waveform equalizer so as to control a tap coefficient of a transversal filter forming the waveform equalizer. CONSTITUTION:A conventional waveform equalizer is provided with a picture quality tap coefficient control circuit 101 controlling a tap coefficient of a transversal filter 403 for the purpose of picture quality correction and a switch circuit 102. At first the switch circuit 102 is used to supply an output signal of an arithmetic circuit 405 to a subtraction circuit 406 to apply waveform equalization and a frequency characteristic of the output signal of the transversal filter 405 is made coincident with the frequency characteristic of a reference waveform memory 404 to apply waveform equalization. Then a correction output signal is selected from the picture quality correction tap coefficient control circuit 101 by the switch circuit 102 and the coefficient of a tap required for picture quality among tap coefficients of the transversal filter 403 stored in the tap coefficient memory 407 is revised by the subtraction circuit 406. Thus, the picture quality is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waveform equalization device used in image equipment such as a television receiver.

[Conventional technology]

In a television receiver, the receiving antenna may receive radio waves directly from the transmitting antenna (desired wave) and radio waves reflected from buildings etc. (reflected waves) at the same time. (a) Desired wave When the time difference between the desired wave and the reflected wave is large, the image of the desired wave and the image of the reflected wave appear shifted on the screen, causing so-called ghost interference. Waveform distortion occurs in the signal, resulting in an image that is entirely blurred or whose contours are too emphasized.

FIG. 2 is a block diagram showing a conventional waveform equalization device for removing waveform distortion occurring in a desired wave signal as described above.

Note that Japanese Patent Application Laid-Open No. 149573/1983 can be cited as a document describing a conventional waveform equalization device.

In FIG. 2, 401 is a video signal input terminal, 402
is an A/D conversion circuit, 403 is a transversal filter, 404 is a reference waveform memory, 405 is an arithmetic circuit, 406
is a subtraction circuit, 407 is a tap coefficient memory, and 408 is a D/
A conversion circuit 409 is a video signal output terminal.

A video signal with waveform distortion input from a video signal input terminal 401 is converted into a digital value by an A/D conversion circuit 402, and the waveform distortion is removed by a transversal filter 403 (hereinafter referred to as waveform equalization). After, D/A
The signal is converted into an analog signal by the conversion circuit 40B and output from the video signal output terminal 409.

There are various algorithms for automatically determining the tap coefficients of the transversal filter 403, but from the standpoint of stability, the
Consumer Electronics Volume C.
E26. August 1980, pp. 629-635 (IEEE, Transaction on Co.
nsumer Electronics, Vol. C
E-2 6. August, 1980.
p. 6 2 9-p. The correlation algorithm discussed in 635) is commonly used.

That is, in the arithmetic circuit 405, the data (Yt) of the output signal of the transversal filter 403 and the data (Ri
Using l, the correlation calculation shown in the following equation is performed.

Zi = α・Σ Rk+i・(Yk−Rk)
(1) Here, α is a positive constant subtracter 406 that converts the output signal Zi of the arithmetic circuit 405 from the old data Ci stored in the tap coefficient memory 407.
is subtracted to obtain a new tap coefficient Ci (i indicates the i-th tap amplifier).

Ci = Ci Zi...
(2) The new tap coefficient Ci is supplied to the transversal filter 403.

By repeating this operation and finally making the data (Yi) of the output signal of the transversal filter 403 the same waveform as the data {Ri} stored in advance in the reference waveform memory 404 without waveform distortion, the input Removes waveform distortion that occurred in the video signal.

[Problem to be solved by the invention]

However, in the above conventional technology, the image quality of the video signal output from the video output terminal 409 is limited to the reference waveform memory 404.
It is uniquely determined by the frequency characteristics of data (Ri) stored in advance.

Therefore, in order to provide image quality that matches the preferences of TV viewers (for example, image quality that emphasizes the Nakagusuku component), (a) As shown in FIG.
01 to 505 are prepared, and after selecting a reference waveform memory that stores a reference waveform with a frequency characteristic close to the image quality according to the taste of the TV viewer, for example 504 with the switch 500, the waveform (b) It is necessary to perform an equalization operation or to prepare an image quality correction device after the waveform equalization device.

An object of the present invention is to provide a waveform equalization device having an image quality correction function using only one reference waveform memory and without preparing an image quality correction device after the waveform equalization device, and such a waveform equalization device. An object of the present invention is to provide an image device equipped with an equalization device and a transversal filter for the waveform equalization device.

[Means to solve the problem]

The purpose of providing a waveform equalization device as described above is to
The conventional waveform equalization device as shown in the figure includes an image quality correction tap coefficient control circuit that controls the tap coefficients of a transversal filter 403 for the purpose of image quality correction, and an arithmetic circuit 4.
This can be achieved by providing a sinch circuit that selects the corrected output from either 05 or the image quality correction tap coefficient control circuit and outputs it to the subtraction circuit 406.

Other objectives will be achieved incidentally. [Operation] First, the switch circuit supplies the output signal of the arithmetic circuit 405 to the subtraction circuit 406 to perform the waveform equalization operation as described with reference to FIG. The frequency characteristics of the reference waveform memory 4
Waveform equalization is performed by matching the frequency characteristics of 04.

Next, in order to perform image quality correction, the switch circuit selects a modified output signal from the image quality correction tap coefficient control circuit, and selects one of the tap coefficients of the transversal filter 4o3 stored in the tap coefficient memory 407. , a subtraction circuit 406 changes tap coefficients necessary for image quality correction. Image quality correction is thereby performed.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG.

FIG. 1 is a block diagram showing an embodiment of a waveform equalization device 100 according to the present invention.

In the figure, blocks with the same numbers as in Figure 2 are:
Shows identical functional blocks. 101 is an image quality correction tap coefficient control circuit, 102 is a switch circuit, 103 is an input terminal for an image quality correction amount control signal, and 104 is a time measurement circuit.

At the start of operation, the output of the time measurement circuit 104 closes the switch circuit 102 to the side a, causing it to perform the same operation as the waveform equalization circuit shown in FIG. Waveform equalization is performed by comparing the frequency characteristics of the reference waveform memory 404 with the frequency characteristics of the reference waveform memory 404.

Next, after a predetermined period of time has elapsed, the switch circuit 102 is closed to the b side by the action of the time measurement circuit 104, and the necessary tap coefficients of the transversal filter 403 are adjusted using the output signal of the tap coefficient control circuit 101 for image quality correction. By changing this, a video signal whose image quality has been corrected is obtained at the output of the transversal filter 403.

Here, a method of changing tap coefficients of the transversal filter 403 for correcting image quality will be explained using FIGS. 4 and 5.

FIG. 4 is a block diagram showing an example of the structure of the transversal fitter 403.

In the figure, blocks with the same numbers as in Figure 1 are:
Shows identical functional blocks. 701 is the A/D conversion circuit 40
The first delay circuit has a delay time that is n times the sampling period τ of 2 (n is an integer), and the number of taps of the transversal filter is determined by the sampling period τ of the A/D converter circuit 402 as the delay time. 703 and 7o4 are adder circuits, and 705 is a multiplier circuit.

Assuming that a rectangular wave with waveform distortion is input to the transversal filter 403 and performing waveform equalization,
The output of the transversal filter 403 is as shown in FIG.
A rectangular wave without waveform distortion shown in b) can be obtained. The tap coefficients of each multiplier circuit 705 at this time are a. Then, i is given as follows.

i--(n-1),-(n-2), ......,
(1,1,2,..., (n-2), (
n-1) Note that the output signal of the multiplication circuit 705 whose tap coefficient is 30 here has a delay time that matches the output signal of the first delay circuit 701.

Here, in order to perform image quality correction, tap coefficients a4 and a
The tap coefficient of the multiplication circuit 705 of 2 is a-z ″ a
-, + (-b) a0 → a0 + (2b) a2 → a, + (-b) As shown in Figure 5 (b), the rising and falling edges of the rectangular wave have a width of 2τ and an amplitude. Shoot b occurs, 3. 5 8 M&(f sc) frequency components can be emphasized.

Further, the tap coefficients of the multiplier circuit 705 with tap coefficients a-4 and a4 are expressed as a-= → a-. +(-b) ao -+ ao +(2b) a4 → a4 + (b) When changing from a4 to a4 + (b), as shown in Figure 5 (c), a shoot with width 4τ and amplitude b is created at the rise and fall of the rectangular wave. is generated, and the frequency component of 1.79 MHz (fsc/2) can be emphasized.

Therefore, after waveform equalization, image quality correction can be performed by changing the tap coefficients of any multiplier circuit 705 of transversal filter 403.

FIG. 6 is a block diagram showing an embodiment of a ghost removal device incorporating a waveform equalization device according to the present invention.

In the figure, blocks with the same numbers as in Figure 4 are:
Shows identical functional blocks. 801 is a transversal filter for ghost removal, 8o2 is a tap coefficient memory that stores tap coefficients of the transversal filter 801, and 803 is a subtraction circuit.

In this ghost removal device, at the start of operation, the switch circuit 102 is closed to the a side, and the video input terminal 401 is closed.
At the same time, a transversal filter 403 removes waveform distortion added to an input signal inputted from the transversal filter 403, and at the same time, a ghost removal transversal filter 801 removes ghosts. Here, a description of the fact that waveform equalization and ghost removal can be achieved by performing the same signal processing in the arithmetic circuit 405 is given in the literature related to the algorithm shown in the conventional example section, and will therefore be omitted.

Thereafter, the switch circuit 102 is closed to the b side, and image quality correction is performed in the same manner as the waveform equalizer 100 according to the present invention shown in FIG.

FIG. 7 shows an embodiment of a television receiver as an image device equipped with a waveform equalization device 100 according to the present invention.

In the figure, 2001 is an RF input terminal, 2002 is a tuner, 2003 is an {F detection circuit, 2004 is a luminance signal and color signal separation circuit (hereinafter referred to as Y/C separation), 20
05 is a color demodulation circuit, 2006 is a color synchronization circuit, 2007 is a matrix circuit, and 200B is a display device.

The RF signal inputted from the RF input terminal 2001 is tuned and detected by the chainer 2002 and the IF detection circuit 2003, and then the waveform distortion is corrected by the waveform equalization device 100.

The output signal of the waveform equalization device 100 is transmitted to the Y/C separation circuit 20.
04, converted into RGB signals by color demodulation circuit 2005, color synchronization circuit 2006, and matrix circuit 2007,
It is supplied to the display device 2008.

In FIG. 7, an example of application as a television receiver is shown.
, the IF detection circuit 2003 and the waveform equalization device 100 can be used as a television tuner as an image device.

FIG. 8 shows another embodiment of a television receiver equipped with a waveform equalizer 100 according to the present invention.

FIG. 7 shows an example in which the waveform equalization device 100 is applied to a composite color television signal, but in this embodiment, the waveform equalization device 100 is applied to a luminance signal Y obtained by separating Y/C from a composite color television signal. be.

Deterioration in image quality due to waveform distortion also occurs for color signals, but it is much more noticeable in luminance signals, so even if waveform equalization is performed only on luminance signal Y, a great effect can be obtained.
Furthermore, since contour correction has conventionally been performed only on the luminance signal Y, it is compatible with contour correction. FIG. 9 shows an embodiment of a video tape recorder (VTR) as an image device equipped with a waveform equalization device 100 according to the present invention. In this figure, blocks with the same numbers as in FIG. 7 indicate the same functional blocks. 2011 is a video signal recording circuit, 2012 is a video head, 2013 is a video signal reproducing circuit, and 2014 is a video output terminal.

The RF signal input from the RF input terminal 2001 is sent to a tuner 2002, an IF detection circuit 2003, and a waveform equalizer 9.
At step 100, the video signal is converted into a video signal from which ghosts have been removed. This video signal is stored in the video signal storage circuit 2011. The video head 2012 records on a magnetic tape (not shown).

The video signal reproducing circuit 2013 is connected to the video head 2012.
The signal read from the magnetic tape is converted into a video signal and supplied to the video output terminal 2014.

In the embodiment of FIG. 9, the input signal is at the RF input terminal 2001.
The waveform equalizer 1 converts a signal that has been converted into a video signal by an external television tuner, etc.
A similar effect can be obtained by directly inputting 00.

〔Effect of the invention〕

According to the present invention, an image quality correction tap coefficient control circuit can be provided in a waveform equalization device in an image equipment such as a television receiver, and the tap coefficients of a transversal filter that constitutes the waveform equalization device can be controlled. Therefore, in addition to waveform equalization processing, image quality correction processing can also be performed, and in this image quality correction, the emphasis frequency (peak frequency) and the amount of emphasis can be freely varied, and there is an advantage that desired image quality can be obtained.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a waveform equalization device as an embodiment of the present invention, Fig. 2 is a block diagram showing a conventional waveform equalization device, and Fig. 3 is a block diagram showing a conventional waveform equalization device with an image quality correction function. A block diagram showing the device, Fig. 4 is a configuration diagram of a transversal filter, Fig. 5 is a waveform diagram showing the principle of image quality correction, and Fig. 6 is a waveform diagram showing the principle of image quality correction.
The figure is a block diagram showing an embodiment of a ghost removal device incorporating a waveform equalization device according to the present invention, and FIGS. 7 and 8 are
FIG. 9 is a block diagram showing an embodiment of a television receiver equipped with a waveform equalization device according to the present invention, and FIG. 9 is a block diagram showing an embodiment of a video table recorder equipped with a waveform equalization device according to the present invention. It is. Description of symbols 100...Waveform equalization device, 101...Tap coefficient control circuit for image quality correction, 102...Switch circuit, 104
... Time measurement circuit, 402 ... A/D conversion circuit, 4
03... Transversal filter, 404... Reference waveform memory, 405... Arithmetic circuit, 406... Subtraction circuit, 407... Tap coefficient memory, 408...
D/A conversion circuit

Claims (1)

[Claims] 1. A transversal filter that corrects waveform distortion for an input signal and outputs the result, a first storage means that stores tap coefficients of the transversal filter, and a reference waveform free from waveform distortion. a second storage means for storing; a calculation means for calculating a modification amount of a tap coefficient of the transversal filter based on a reference waveform read from the second storage means and an output signal of the transversal filter;
and a tap coefficient correction means for correcting the tap coefficients read from the storage means according to the correction amount obtained by the calculation means and writing the same into the first storage means again, the waveform equalization device comprising: an image quality correction tap coefficient control means capable of outputting a tap coefficient correction amount for contour correction of a display image based on an input signal; a correction amount from the calculation means and a correction amount from the image quality correction tap coefficient control means; 1. A waveform equalization device comprising: a switch means for switching between and supplying the same to the tap coefficient correction means. 2. In the waveform equalization device according to claim 1, the correction amount from the calculation means is initially supplied to the tap coefficient correction means, and after a predetermined time has elapsed, the correction amount from the image quality correction tap coefficient control means is supplied. 2. A waveform equalization device, further comprising time measuring means for controlling said switch means according to the passage of time so as to supply the tap coefficient correction means to the tap coefficient correction means. 3. A first transversal filter that corrects waveform distortion with respect to an input signal and outputs it; and an output signal of the first transversal filter that is input, removes ghost components contained therein, and outputs it. a second transversal filter; a first storage means for storing the tap coefficients of the first transversal filter; a second storage means for storing the tap coefficients of the second transversal filter; a third storage means for storing a reference waveform that does not include ghost components; and a third storage means for storing a reference waveform that does not include ghost components; a calculation means for calculating a modification amount of a tap coefficient of the transversal filter; and a calculation means for modifying the tap coefficient read from the first storage means by the tap coefficient modification amount for the first transversal filter determined by the calculation means. a first tap coefficient correcting means for applying and rewriting it to the first storage means, and a second transversal filter calculated by the calculation means for the tap coefficient read from the second storage means; A second step in which the tap coefficient is corrected by the tap coefficient correction amount and written into the second storage means again.
A waveform equalization device comprising: tap coefficient correction means for image quality correction capable of outputting a tap coefficient correction amount for contour correction of a display image based on the input signal; The amount of modification of the tap coefficients of the first transversal filter and the amount of modification from the image quality correction tap coefficient control means are switched.
A waveform equalization device comprising: switch means for supplying the signal to the tap coefficient correction means. 4. The waveform equalization device according to claim 1, 2 or 3, wherein the input signal is a composite video signal or a luminance signal separated from the video signal by luminance signal/chrominance signal separation. Equalizer. 5. An imaging device comprising the waveform equalization device according to claim 4. 6. A transversal filter for a waveform equalizer according to claim 1, 2, 3, or 4, wherein the number of taps constituting the filter is m, and the tap interval is τ in terms of delay time.
A transversal filter comprising a delay line having a delay time substantially close to a value of (mτ)/2.