JPS58202676A - Ghost eliminating device - Google Patents

Abstract

PURPOSE:To improve eliminating characteristics of the high frequency component of the ghost and to eliminate not only the luminance ghost but the color ghost, by using a device containing a transversal filter to use a burst signal as the reference signal. CONSTITUTION:A transversal filter is constituted with delay elements 21-26 connected to a video signal input terminal 1, tap amplifiers 31-36, switches 41- 46 and an adder 5. The delay time of the elements 21-26 is set 3 times as much as the frequency of a burst signal (3.58MHz). The output of the adder 5 is applied to a burst signal detecting circuit 7 to detect the burst part of a vertical flyback time. This burst part is applied to a 3.58MHz continuous wave generating circuit 8 and synchronous wave detecting circuits 11-13. While the signals given from the circuit 8 are converted into signals of different phases by 120 deg. phase shifters 9 and 10 and applied to the circuits 11-13. The outputs of the circuits 11-13 are written to a tap gain memory 18 via a shift register 16. Then each tap of the filter is controlled with the burst signal used as the reference signal. Thus the eliminating characteristics can be improved for the high frequency component of the ghost.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ghost removal device for a television receiver.

Ghosts are a major cause of deterioration of the image quality of television receivers, and various methods have been attempted to eliminate or prevent ghosts.

One of them is a method using a transversal filter for video fireflies.

This method connects a large number of microdelay circuits with a delay time determined by the highest frequency component contained in the video signal in an array.
It attempts to remove ghosts using a ghost compensation signal obtained by adding weights to the outputs of each minute delay circuit using a coefficient circuit, and in many cases, a horizontal synchronization signal or a vertical synchronization signal is used as a reference signal for ghost removal. Accordingly, the coefficients of the coefficient circuit described above are automatically set.

However, in this method, the horizontal synchronization signal and vertical synchronization signal used as reference signals mainly consist of low frequency components and have small high frequency components. The disadvantage is that the ability to remove ghosts from signals is not sufficient, and color ghosts cannot be removed completely.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a ghost removal device using a transversal filter that can remove not only luminance signals but also color signals.

In order to avoid delaying the above-mentioned purpose, in the present invention, the reference signal for ghost removal is not a horizontal or vertical synchronization signal, but rather
It is characterized by removing not only luminance ghosts but also color ghosts by using burst signals.

Specific embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is a video signal input terminal, 21 to 26 are delay elements, 31 to 36 are tap amplifiers 41 to 46 are switches, and 5 is an adder. , 6 is a video signal output terminal, 7 is a burst signal detection circuit, 8 is a 3.58 MH"Zj continuous wave generation circuit, 9.10 is a 120° phase shifter, 11 to 13 are synchronous detection circuits, 141 to 143 are Switches 151 to 153 are differentiating circuits, 16 is a shift register, 17 is a subtracter, 18 is a tap gain memory, and 19 is a D/A converter.

In such a ghost removal device, the delay elements 21 to
26, tap amplifiers 31-66, switches 41-46,
The adder 5 constitutes a transversal filter, and the other parts are involved in automatic gain control IK of the tap amplifiers 31-36. Further, the delay time of the delay element is six times the frequency of 3.58 MH2 constituting the burst signal.

A period of 10.74 MHz, i.e. 93. Selected by ins.

Now, a television signal containing a ghost is input to the video signal input terminal 1. Before the ghost removal operation starts, the 11th gains of the tap amplifiers 31 to 66 are 0, so
The output signal of the input signal can be obtained from the video signal output terminal B.

Since an actual television signal has a portion consisting only of equalization pulses and burst signals during the vertical retrace period, this portion is detected and input to the burst signal detection circuit 7 consisting of a 3.58 MHz bandpass filter. As shown in FIG. 2(a), a signal consisting only of bursts of the desired signal and bursts of the ghost signal is obtained at the output.

Assume now that the burst phase of the ghost signal leads the burst phase of the desired signal by 90°. If this is drawn as a vector diagram, it will look like Figure 3.

The burst signal detected in this way is 3.58MHz
The signal is input to continuous wave generation circuit 8 and synchronous detection circuits 11 to 13. The 3.58 MHz continuous wave generating circuit 8 generates a signal having substantially the same phase as the burst of the desired signal. This signal is input to a 120° phase shifter 9 and further to 10. As a result, 0°, 120°, 24° relative to the burst phase of the desired signal
Three 3.58MH2 continuous waves at 0° are obtained.

The six 3.58 MHz continuous waves ■, o, and ◎ in the order shown in the vector diagram of Figure 3 are respectively sent to the synchronous detection circuits 11, 12, and 13, and are sent to the synchronous detection circuits 11, 12, and 13, respectively, as shown in the vector diagram in Figure 3. The output of the detection circuit 7 is synchronously detected.

As shown in Figure 3, the output of each detection circuit is to output bursts of the desired signal and ghost signal to each detection axis.
It becomes the component projected to ◎.

That is, if the size of the burst of the desired signal is 1, then the components of the ■, ■, and 0 valley axes are respectively 1. -1 becomes 1. The ghost signal 2' 2 is also obtained in the same manner.

Therefore, the outputs of the synchronous detection circuits H12 and H13 are as shown in FIG. 2(d).

The outputs of the synchronous detection circuits 11, 12, and 13 are sent to differentiating circuits 151 and 15, respectively, in order to detect the ghost delay time.
2. Φ minutes at 15!1. This is shown in Figure 3)', (
0'.

Shown in (d)′. This differential output is shaped into a +
After being slightly encoded, it is sent to shift register B. The transfer lock of shift register B is 10.74M)JZ, and in the first case, the switch 142 closes and the output of the differentiating circuit 152 is output, and in the second case, the switch 143 closes the output of the differentiating circuit 153. , and thirdly, the switch 141 is closed and the output of the differentiating circuit 151 is input to the shift register 6.

From the fourth onwards, the above process is repeated, and data for one cycle of the burst signal is transferred in six clocks.

However, since the differential pulse generated at the position where the burst of the desired signal exists is not due to a ghost signal, it is assumed that there is no differential pulse, that is, 0. This is because the generation timing and end timing of the burst signal are determined in advance. It can be easily identified.

When the error signal due to the ghost is transferred to the limit register 16, correction of the tap gain stored in the tap gain memory 18 starts.

The data in the tap gain memory 18 is sequentially read out from the first address and sent to the subtracter 17.

Since the data initially convolved in the shift register 16 is also sent to the subtracter 17, the tap gain data is modified.

The modified tap gain data is stored in tap gain memory 1 again.
8, it becomes new tap gain data.

The above process is repeated for all addresses in tap gain memory 18.

Next, the tap gain memory 18 opens the tap amplifiers 31 to 36 to 1゛□! New data is read out from the initial address of the tumble gain memory 18 again.

D/A converter 19 converts the value into an analog voltage, which is applied to tap amplifier 31 when switch 41 closes. A small capacitor is added to the tap amplifier 61, and the output of the D/A converter 19 is stored in the capacitor. After the first address is read, the tap gain memory 1
On the day, the second address is read and the data is transferred to the D/A
converted.

Switch 42 is now closed, again holding the voltage on the capacitor of tap amplifier 52.

After that, this process is repeated, and when -th data is read out, the data is read out again from the first data, and the capacitor is charged.

As described above, ghost detection, rewriting of the tap gain memory on a daily basis, and control of the tap amplifiers 31 to 36 are performed in one day because ghost detection is performed using burst signals.
This is performed once in a horizontal period or one vertical period, and is repeated until a ghost is detected and Qi<'h.

Now, how ghosts are removed by the method described above will be explained below. As already mentioned, 8.

The delay time of delay elements 21 to 26 is 93. It's ins,
1/3 of the period of the burst signal. Therefore, for a burst of the desired signal, the delay element 21.
The output from 22.23 has a phase difference of 120°24060° (
660°) ~.

In addition, the shift register 16 has 120°, 240°
As already mentioned, a digital value indicating the delay time of a ghost signal detected at a phase of 0° or more is input. Therefore, the phase information of the ghost signal input to the shift register 16 and the phase information of each delay element output have a one-to-one correspondence.

That is, in Fig. 3, the fourth part shows only the ghost signal.
Delay elements 21 to 21 corresponding to detection axes ■, ◎, and ■ in the figure
26 as n, n+1, and n+2, the component of the detection axis ■ is positive, so the gain of tap n → is self, and the component of the detection axis O is negative, so the tap A positive gain is given to n+1.

Since the component of the weak detection axis (■) is 0, the gain of tap n12 remains 0. Since the burst of the desired signal is delayed by the delay time to these delay elements and the gain is controlled as described above, a compensation signal as shown in Figure 4 is generated.1 This compensation signal is a ghost signal. is in reverse phase with
Since the ghost signal is mixed with the ghost signal in the emulator 5, the level of the ghost signal is reduced.

By repeating this process every time a ghost is detected, a ghost-free signal can be obtained at the video signal output terminal B.

In the example above, the delay time of the ghost was long enough that it did not overlap with the burst of the desired signal, but even if the car crashed, the differential pulse in Figure 2 would still be between the differential pulses caused by the burst of the desired signal. There is no change in the above behavior.

Further, in the embodiment, the number of ghosts is one, but even if there are a plurality of ghosts, the number of differential pulses will only increase, and the above-described operation will not change.

Furthermore, in the embodiment, there are three synchronous detection circuits,
The delay time of each delay element was selected to be 1/3 of the burst signal period, but as long as the sampling theorem is satisfied, the delay time was selected to be 1/N of the burst signal period, where N is an integer, and N synchronous detection circuits were used. It may be provided. Of course, this occasion is 36
An o/N degree phase shifter will be used.

As described above, according to this embodiment, color ghosts can be removed by detecting and removing burst ghosts.

Needless to say, by removing the burst ghost, the luminance ghost can also be removed.

As described above, according to the present invention, by using a burst signal as a reference signal in a ghost removal device using a transversal filter, ghosts can be reduced more easily than in the case where conventional horizontal and vertical synchronization signals are used. The removal characteristics of high frequency components are improved. -Thus, it is also possible to remove color ghosts, greatly improving performance.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a ghost removal device according to the present invention, and FIG.
The figures are (a) to (d), (ra) to (d') are signal waveform diagrams,
3 and 4 are signal vector diagrams. 21 to 26...Delay elements 51 to 36...Tass Chi 1 chanter 5...
Adder 7...Burst signal detection circuit 8...3.58MHz continuous wave generation circuit 910.
...120° phase shifter 11 to 16 ... Synchronous detection circuit 151 to 156 ... Differentiation (b) approximately 16 ...
...Shift register 17...Reducer 18...Tap gain memory 19...D/A transformer 12. Fang 1 Figure 2 Figure 'f3 layer =; 4th figure procedural amendment (method) Indication of the case 1982 Patent Application No. 84707 Name of the invention Ghost removal device Name of the person making the correction ++j, <510) Manufactured by Kaishin Hitachi Co., Ltd.
Author Name: 3 1) Shigeyo Katsu
Subject of personal amendment: In the column of the brief description of the drawings in the specification and Figures 2 (b') to (d''), ``'' should be corrected to ``Figure 2 (α) to 0)''. 2. Figure 2 of the drawing is corrected as shown in the attached sheet. That's all for men 2 chants (α) (b). (O). +d>. (e) (9)

Claims (1)

[Claims] 1. A transversal filter having a plurality of taps, the gain of each tap being variable, means for detecting a burst signal included in a television signal, and detecting the phase from the output of the means. means for generating N different continuous waves;
A ghost characterized by comprising: N detection circuits for detecting the burst signal using the outputs of the means; and means for controlling the outputs of the N detection circuits and the gain of each tap of the transversal filter. removal device. 2. The means for controlling the tap gain includes means for converting the outputs of the N detection circuits into digital signals, a shift register for sequentially and periodically inputting the outputs of the detection circuits that have become digital signals, and It consists of a digital memory for storing data, a means for subtracting the data in the digital memory and the data in the shift register, and a D/A converter for converting the output of the digital memory into an analog voltage.
2. The ghost removal device according to claim 1, wherein the ghost removal device performs the ghost removal by applying the output of the A converter to each tap. 6. The N continuous waves have phases different from each other by 360/N degrees, and the tap interval of the transversal fill is X of the burst signal period. Or the ghost removal device according to item 2.