JPH0338973A - Method and device for removing ghost, television receiver, tuner and tape recorder equipped with same - Google Patents

Abstract

PURPOSE:To shorten time required for the removal of ghost by memorizing the correction quantity of tap gain, which is calculated in preceding operation, by a preceding correction quantity storing circuit and subtracting only the correction quantity of the tap gain, which is calculated in the preceding operation, from the output signal of an output waveform memory. CONSTITUTION:A preceding correction quantity storing circuit 110 is provided to store the preceding correction quantity of the tap gain, which is calculated by an arithmetic circuit 307, and a second subtracter 120 is provided to execute subtraction between the output signal of an output waveform memory 306 and the output signal of the preceding correction quantity storing circuit 110 and to input a subtracted result to the arithmetic circuit 307. In such a way, the preceding correction quantity of the tap gain is stored by the preceding correction quantity storing circuit 110 and a signal, which is acquired by executing the subtraction between the output signal of the circuit 110 and the output signal of the output waveform memory 306 in the second subtracter 120, is supplied to the arithmetic circuit 307. Accordingly, the over compensation of the tap gain is eliminated. Thus, an waveform is fetched without waiting time after the correction quantity of the tap gain is determined. Then, the time required for removing the ghost is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a ghost removal method and device implemented in a television receiver or the like, a television receiver equipped with the device,
It relates to tuners and video tape recorders.

[Conventional technology]

In a television receiver, when radio waves arriving directly from the transmitting antenna (desired waves) and radio waves reflected from buildings, etc. (reflected waves) are simultaneously received by the receiving antenna, an image due to the desired waves and the reflected waves are generated. A so-called ghost occurs, where the image appears shifted.

Such ghosts are a major factor in deteriorating the image quality of television receivers, and various methods have been attempted to eliminate or prevent ghosts. One of them is a ghost removal device using a transversal filter in the video band.

The basic operation of ghost removal by a transversal filter will be explained using FIG. 2.

In FIG. 2(A), 201 is an input terminal, 202 is a tapped delay line, 203 is a tap amplifier, 204 is an adder, 205 is a subtracter, 206 is an output terminal, and τ is the input terminal of the tapped delay line 202. This is the pump interval (delay time) and is determined by the highest frequency component contained in the video signal.

When a video signal as shown by a in the figure (B), in which a delay line of 3τ and an in-phase ghost of amplitude A is added to the desired signal, is input to the input terminal 201, the delay with knob VA202
Let A be the gain of the tap amplifier 203 connected to the third tap from the input terminal 201 side (hereinafter referred to as tap gain). At this time, the output of the adder 204 contains b
Since the ghost compensation signal shown in is obtained, the subtracter 205
By subtracting the ghost compensation signal from the signal input at , it is possible to obtain a ghost-free signal shown at output terminal 206 at C.

There are various algorithms that automatically determine the tap gain, but from the standpoint of stability, IE Transactions on Consumer Electronics
Volume C.E. 26 August 1980, No. 62
635 from page 9 (IEEE Transaction
on Consumer Electronics
cs.

Vol, CE-26, August, 1980.
The correlation algorithm discussed in 2003, p., 629-p, 635) is commonly used.

FIG. 3 shows a diagram of a configuration example of a conventional ghost removal device using a correlation algorithm.

In the figure, 301 is an input terminal, 302 is an A/D conversion circuit, 303 is a transversal filter, 304 is a differentiation circuit, 305 is a noise reducer, 306 is an output waveform memory, 307 is an arithmetic circuit, 308 is a reference waveform memory,
309 is a subtracter, 31O is a tap gain memory, 311 is a D/A 5-conversion circuit, and 312 is an output terminal.

A video signal input from an input terminal 301 is converted into a digital signal by an A/D conversion circuit 302, ghosts are removed by a transversal filter 303, and then the video signal is converted to a digital signal by an A/D conversion circuit 302.
It is converted into an analog signal by the A conversion circuit 311 and output from the output terminal 312.

The output signal of the 10-lance versal filter 303 is differentiated by a differentiating circuit 304, and then noise is suppressed by a noise reducer 305 and stored in an output waveform memory 306.

The arithmetic circuit 307 calculates the data [Y
Using il and data (Ril) preliminarily stored in the reference waveform memory 308, a correlation calculation shown in the following equation is performed.

Zi −α・Σ Rk+i・Yk
(1) Here, α is a positive constant subtracter 309 that converts the output signal Zi of the arithmetic circuit 307 from the old data Ci stored in the tap gain memory 310.
to obtain a new tap gain C1 (i indicates the i-th tap amplifier).

C4=Ci-Zi...
(2) The new tap gain C4 is supplied to the transversal filter 303. By repeating this operation, the ghost is finally removed.

Next, the transversal filter 30 is
The meaning of differentiating the output signal in step 3 will be explained.

In general, ghost detection involves avoiding signal components that may constantly fluctuate, such as pictures, and picking up signals such as the vertical synchronization signal that always appear at a constant period, and detecting ghosts at the leading edge of this vertical synchronization signal. This is done using the leading edge of the vertical synchronization signal because it is technically easy. (IEE Transactions on Consumer Electronics Volume CEE 24. August 1978, pp. 267-27)
Page 1 (IEE, Transaction
on Con5un+erElectronics,
Vol, CE-24, August, 1978
(p, 267-p, 271)) FIG. 4(a) shows a vertical synchronization signal and a ghost superimposed on it (the leading edge of the vertical synchronization signal and its ghost). Assume that the output is from .

Then, in order to detect the delay time τg and amplitude A of the ghost, the vertical synchronization signal and the ghost are differentiated by a differentiating circuit 304 to obtain the pulse waveform shown in FIG. If we calculate the correlation with a similar pulse waveform (Fig. 4 (C)) that does not have the same value, we can obtain the correlation value shown in Fig. 4 (d). In the process of calculating the correlation value, we can calculate the ghost delay time τg Arithmetic circuit 3
It is found at 07.

Once the delay time τg is found, the transversal filter 3
Since we know which order position in 03 the gain of the tap amplifier should be adjusted, we can slightly modify the gain of that amplifier. This process is repeated for each incoming vertical synchronization signal to gradually reduce the ghost.
Finally make it zero.

A specific example of a ghost removal device is disclosed in Japanese Patent Application Laid-open No. 55
The one described in JP-A-149523 is known.

[Problem to be solved by the invention]

The above conventional technology has the following problems.

In the conventional ghost removal device shown in FIG. 3, the ghost removal is not performed at once, but the amount of correction of the tap gain of the transversal filter 303 is made small (as described above) in order to obtain system stability. α in equation (1) = 0.0
(set to about 1). Therefore, in order to completely remove ghosts, several hundred corrections are usually required.

Therefore, if the correlation calculation shown in equation (1) above is configured in hardware, the scale of the hardware will increase, so C
If this is realized by software using a CPU or the like, the CPU with a slow operating speed will spend a lot of time on correlation calculations, etc., making it impossible to detect ghosts within 1 field, and the time required to completely remove ghosts will increase (( (number of fields required for noise reduction) + (number of fields required for calculation by CPU, etc.)) x (number of corrections), for example, (number of fields required for noise reduction) - 4 fields (number of fields required for calculation by CPU, etc.) If = 2 fields (number of corrections) - 200 times, there is a problem that it takes 1200 fields (approximately 20 seconds) and the ghost removal time becomes too long.

Here, noise reduction is performed by averaging. That is, in the case of 4 fields, if the signals of the 4 fields are averaged, the noise has no correlation between the fields, but the signal components are correlated, so the noise can be reduced by averaging.

An object of the present invention is to provide a ghost removal method and device capable of reducing the time required for ghost removal as much as possible even when the time required for one ghost detection is long, such as over several fields, and a television receiver equipped with the device. , a tuner and a tape recorder.

[Means to solve the problem]

The above purpose is achieved by the ghost removal device shown in FIG.
A previous correction amount storage circuit that stores the correction amount of the previous tap gain calculated in the arithmetic circuit 307 performs subtraction between the output signal of the output waveform memory 306 and the output signal from the previous correction amount storage circuit. This is achieved by providing a second subtracter which inputs the result to the computation circuit 307 instead of the output signal of the output waveform memory 306.

[Effect]

In the conventional ghost removal device shown in FIG. The amount of tap gain correction was determined serially.

In other words, the transversal filter 303 in the arithmetic circuit 307
After determining the tap gain correction amount, the next time the waveform used for ghost detection is loaded into the output waveform memory 306, the contents of the tap gain memory 310 are corrected by the tap gain correction amount determined by the arithmetic circuit 307. Wait until the transversal filter 303 actually performs the ghost removal operation, and then use the output signal of the transversal filter 303 operating in this manner as the output waveform as the waveform used to detect ghosts. It was imported into the memory 306. This waiting time has created a problem in that the time required to remove ghosts is long.

Therefore, without such waiting time, in other words, the arithmetic circuit 30
After determining the tap gain modification amount of the transversal filter 303 in step 7, the next time the waveform used for ghost detection is loaded into the output waveform memory 306, the tap gain is adjusted by the tap gain modification amount determined by the arithmetic circuit 307. Instead of waiting for the contents of the memory 310 to be modified so that the transversal filter 303 actually performs the ghost removal operation, it is conceivable to do it immediately.

However, in this method, the amount of correction of the tap gain from the second time onward is determined because the waveform is captured before the new corrected tap gain is given to the transversal filter 303. The next tap gain correction amount is determined using the waveform (the same waveform that was captured last time) in which the ghost has disappeared by the amount of tap gain correction, resulting in overcompensation of the tap gain. .

Here, as is already clear, the cause of overcompensation of the tap gain is that a ghost component of a size equivalent to the amount of correction of the previous tap gain remains in the output signal of the output waveform memory 306. Therefore, the previous correction amount storage circuit stores the previous correction amount of the tamping gain, and the second subtracter combines the output signal of the output waveform memory 306 with the previous correction amount storage circuit. By supplying a signal obtained by performing subtraction with the output signal of , to the arithmetic circuit 307, overcompensation of the tap gain can be eliminated.

Therefore, the waveform can be captured without waiting time after determining the tap gain correction amount, and the time required to remove ghosts can be shortened.

(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 ghost removal device according to the present invention. In this figure, blocks with the same numbers as those in FIG. 3 indicate the same functional blocks. 100 is a ghost/removal device; 110 is a previous correction amount storage circuit that stores the tap gain correction amount before the operation; 1
A second subtracter 20 subtracts the output signal of the output waveform memory 306 and the output signal of the previous correction amount storage circuit 110.

The basic operation of the present ghost removal device 100 is the same as that of the ghost removal device shown in FIG.

Hereinafter, the features of the present ghost removal apparatus 100 will be explained using FIG. 5.

In the ghost removal device shown in Fig. 3, as shown in Fig. 5(a), the waveform (
For example, since the ghost detection and tap gain correction processing is performed after capturing the waveform for 4 fields, the time required to complete one tap gain correction is the same as the field required for both processing. It becomes the sum of the numbers. In other words, if 2 fields are required for processing, 6 fields are required including the 4 fields required for waveform acquisition.

Therefore, in the present invention, in order to shorten the time required to complete one correction of the tap gain, as shown in FIG. Don't wait for the correction process to finish, but do it in parallel with it.

However, in this case, as shown in FIG. 5(b), after the first tap gain correction is performed and before the new operation of the transversal filter begins, the second tap gain correction is performed. Since the waveform for determining the amount is taken in, a ghost component that is larger by one correction amount than the ghost component attached to the output signal of the transversal filter 303 that has actually entered the new operation described above is attached. , a second waveform is captured, and a second tap gain correction is performed thereby, so as a result, ghost removal is always performed in an overcompensated state. Therefore, there is a possibility that control becomes unstable.

Therefore, in the ghost removal device 100 according to the present invention, two
Noting that the remaining ghost added to the signal taken into the output waveform memory 306 from the previous time is larger by the amount of correction of the tap gain obtained in the previous time, After remembering the amount of tap gain correction found in the previous round, and subtracting the amount of tap gain correction found in the previous round from the output signal of the output waveform memory 306 using the second subtracter 120, Arithmetic circuit 307
Enter. As a result, the unstable control caused by overcompensation described above can be solved.

Furthermore, in the ghost removal device 100 according to the present invention, the fifth
As shown in figure (b), it takes a little time for the first 1.2 fields, but assuming several hundred corrections, the time required for ghost removal will be approximately 100% (the number of fields required for noise reduction). × (number of corrections), so
As in the above example, if (number of fields required for noise reduction) = 4 fields (number of corrections) - 200 times, then the number of fields will be 800 (approximately 13 seconds), which can significantly shorten the removal time.

FIG. 6 is a block diagram showing another embodiment of the ghost removal device 100 according to the present invention. In this figure, blocks with the same numbers as those in FIG. 1 indicate the same functional blocks.

In the figure, 610 is a vertical synchronization signal input terminal, 620
is a counter, and 630 is a switch.

The basic operation of the present ghost removal apparatus 100 is the same as that of the ghost removal apparatus shown in FIG.

However, as long as the ghosts are removed to an unnoticeable level within the specified time, even if it takes a little longer to remove the remaining ghosts, there is no problem as long as you are watching TV, so you can continue to operate as usual. Focusing on the fact that there is no ghost removal, after a predetermined time has elapsed from the start of ghost removal, the same operation as the conventional ghost removal apparatus shown in FIG. 3 is performed, but this point is different.

At the start of ghost removal, the spin filter 30 is closed to the contact a side and operates in the same manner as the ghost removal apparatus according to the present invention shown in FIG. 1, thereby shortening the tap gain correction time.

After that, the counter 620 inputs the vertical synchronizing signal input terminal 61
After counting the vertical synchronization signal inputted from 0 to 1 to 1 a predetermined number of times (after a predetermined period of time has elapsed), the switch 630
is closed to the contact side, and the same operation as that of the conventional ghost removal device shown in FIG. 3 is performed (waveform acquisition and tap gain correction are carried out serially with a waiting time).

FIG. 7 is a block diagram showing still another embodiment of the ghost removal device 100 according to the present invention. In this figure, blocks with the same numbers as those in FIG. 6 indicate the same functional blocks. 710 is a switch.

The basic operation of the present ghost removal apparatus 100 is the same as that of the ghost removal apparatus shown in FIG.

However, in the ghost removal device shown in FIG. 6, a video signal in the process of ghost removal is output from the output terminal 312, but in the ghost removal device shown in FIG. Until the predetermined time has elapsed, the input video signal is output as is, and after the predetermined time elapses,
It is designed to output a signal with ghosts removed,
This point is different.

That is, until a predetermined period of time has elapsed from the start of ghost removal (the counter 620 counts the vertical synchronization signal a predetermined number of times), the switch 630 and the switch 710 are closed to the contact a side, and the ghost is removed as quickly as possible. allows the input video signal to be displayed on the TV as is.

After a predetermined period of time has elapsed, the switch 630 and the switch 710 are closed to the contact side to output a video signal from which ghosts have been removed, and the ghost detection method is carried out as before.

In the ghost removal apparatus 100 shown in FIG. 7, the timings of switching the switches 630 and 710 are not necessarily simultaneous, and there is no problem even if a time difference is provided.

Further, although the switch 630 is provided in the ghost removal device 100 shown in FIG. 7, this may be removed and the a contact side may be directly connected to the arithmetic circuit 307 to speed up the ghost removal time. .

FIG. 8 shows an embodiment of a television receiver equipped with a ghost removal device 100 according to the present invention.

In the figure, 2001 is an RF input terminal, 2002 is a tuner, 2003 is an IF detection circuit, 2004 is a luminance signal and color signal separation circuit (hereinafter abbreviated as Y/C separation circuit),
2005 is a color demodulation circuit, 2006 is a color synchronization circuit, 200
7 is a matrix circuit, and 2008 is a display device.

After the RF multiplied signal input from the RF input terminal 2001 is tuned and detected by the tuner 2002 and the IP detection circuit 2003, the ghost is removed by the ghost removal device 1OO. The output signal of the ghost removal device 100 is Y/C
Separation circuit 2004, color demodulation circuit 2005, color synchronization circuit 2
006, RG B f by the matrix circuit 2007
It is converted into No. A and supplied to the display device 2008.

In FIG. 8, an example of application as a television receiver is shown.
, the IF detection circuit 2003 and the ghost removal device 100 can also be applied to a television tuner.

FIG. 9 shows an embodiment of a video tape recorder (VTR) equipped with a ghost removal device 100 according to the present invention.

In the figure, blocks with the same numbers as those in FIG. 8 indicate the same functional blocks. 2011 is the video signal recording circuit, 2012 is the video head, 2013
2014 is a video signal reproducing circuit, and 2014 is a video output terminal.

The RF multiplied signal inputted from the RF input terminal 2001 is converted by the tuner 2002, the IF detection circuit 2003, and the ghost removal device 100 into a video signal from which ghosts have been removed. This video signal is transmitted to the bidet No. 13 recording circuit 201.
1. Recorded on magnetic tape by Nodo 2012 to video. The video signal reproducing circuit 2013 converts the signal read from the magnetic tape by the video head 2012 into a video signal, and supplies the video signal to the video output terminal 2014.

In the embodiment of FIG. 9, the input signal is at the RF input terminal 2001.
However, it goes without saying that the same effect can be obtained by directly inputting a signal that has been converted into a video signal from an external television tuner or the like directly to the ghost removal apparatus 100.

〔Effect of the invention〕

As described above, according to the present invention, the operation of capturing a waveform for detecting a ghost can be performed without waiting for the completion of the previous operation of detecting a ghost and calculating the correction amount of the tap gain. A ghost removal method and device that can significantly reduce the time required to remove ghosts even when using a CPU in which the calculation time required to determine the amount of correction of tap gain spans the entire field, and a television receiver equipped with the device, Tuners and video tape recorders can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a ghost removal device according to the present invention, FIG. 2 is an explanatory diagram for explaining the basic operation of a transversal filter, and FIG. 3 is a conventional ghost removal device using a transversal filter. A block diagram showing an example, FIG. 4 is an explanatory diagram illustrating a ghost detection method using a vertical synchronization signal, and FIG. 5 is an explanatory diagram illustrating the operating principle of the ghost removal device according to the present invention in comparison with a conventional one. , FIG. 6, and FIG. 7 are block diagrams showing other embodiments of the ghost removal device according to the present invention, and FIG. 8 is a block diagram showing an embodiment of a television receiver equipped with the ghost removal device according to the present invention. 9 are block diagrams showing an embodiment of a video tape recorder equipped with a ghost removal device according to the present invention. Explanation of symbols

Claims (1)

[Claims] 1. The first storage means (1) captures a signal waveform for detecting a ghost component from the output signal of a transversal filter (303) for removing a ghost component added to an input video signal; 306), and from the reference waveform read from the second storage means (308) for storing the reference waveform and the signal waveform read from the first storage means (306), the calculation means (307) calculates the a step of calculating a modification amount of the tap gain of the transversal filter; and a step of reading the tap gain stored in the third storage means (310) for storing the tap gain of the transversal filter, and using the calculation means. The obtained correction amount is subtracted and the third storage means (
310), the step of storing the tap gain previously determined by the calculation means (307) in the fourth storage means (110);
further comprising the step of subtracting the previously determined tap gain read out from the fourth storage means (110) from the signal waveform read out from the storage means (306), and then inputting the result to the calculation means (307). A ghost removal method featuring: 2. A transversal filter (303) that removes a ghost component added to an input video signal and outputs the result, and a first filter that captures and stores a signal waveform for ghost component detection from the output signal of the transversal filter. A storage means (306), a second storage means (308) for storing a reference waveform, and a signal waveform stored in the first storage means (306) and a reference stored in the second storage means (308). a third storage means (310) for storing the tap gain of the transversal filter;
a first subtraction means (309) that reads the tap gain stored therein from the storage means (310), subtracts the correction amount obtained by the calculation means, and writes the result to the third storage means (310); A ghost removal device comprising: fourth storage means (110) for storing the tap gain previously determined by the calculation means (307); Ghost removal characterized by comprising: a second subtraction means (120) that subtracts the previously obtained tap gain read from the fourth storage means (110) and then inputs the result to the calculation means (307). Device. 3. In the ghost removal device according to claim 2, after the start of the ghost removal operation, until the number of times the calculation means calculates the tap gain correction amount reaches a predetermined number of times, the second subtraction means (120) After reaching a predetermined number of times, the signal waveform read out from the first storage means (306) is directly selected and the signal waveform read out from the first storage means (306) is selected.
7) A ghost removal device characterized by comprising a first selection means (630) for outputting an output. 4. The ghost removal device according to claim 2 or 3, wherein at the start of the ghost removal operation, the input video signal to be input to the transversal filter is directly selected and outputted;
A ghost removal device characterized by comprising second selection means (710) that selects and outputs the output signal of the transversal filter after a predetermined period of time has elapsed. 5. A television receiver comprising the ghost removal device according to claim 2, 3 or 4. 6. A television tuner comprising the ghost removal device according to claim 2, 3 or 4. 7. A tape recorder comprising the ghost removing device according to claim 2, 3 or 4.