JPS62272671A - Ghost detecting circuit - Google Patents

Abstract

PURPOSE:To obtain a ghost detecting circuit with high performance by detecting a ghost by using a GCR signal when a ghost cancelling reference signal (GCR signal) is fed in a signal fed from a broadcasting station and detecting the ghost by using the front edge of a vertical synchronizing signal when the GCR signal is not fed. CONSTITUTION:There are provided a video signal input terminal 201, a ghost cancelling reference signal fed from the broadcasting station sampling circuit 202, a front edge sampling circuit 203 of the vertical synchronizing signal, a switch 204, and a ghost detecting circuit 205. Thereby, when said GCR signal is present in the video signal inputted to the input terminal 201, the switch 204 is closed to an (a) side by a control signal 206 and when the GCR signal is not present, the switch 204 is closed to a (b) side. Thereby, a signal inputted to the ghost detecting circuit 205 can be selected.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a ghost detection circuit of a ghost removal device in a television receiver.

[Conventional technology]

In a television receiver, when a radio wave (desired wave) that comes directly from the transmit antenna and a radio wave that is reflected from a building etc. are simultaneously received by the receiving antenna, an image due to the desired wave and an image due to the reflected wave are generated. disappears and appears,
A so-called ghost occurs.

Ghosts that appear on television receivers are a major cause of deterioration of image quality, and various methods have been used in the past to try to eliminate or prevent ghosts. One of them is a ghost removal device using a transversal filter in a video band. This method connects a large number of delay elements in series, each with a minute delay time determined by the highest frequency component included in the video signal, and adds the output of each delay element with a weighted coefficient of 13 times to output the ghost. The purpose is to obtain a ghost compensation signal that removes the .

In the conventional ghost removal device using such a transversal filter, as described in "Broadcasting Technology", September issue, 1978, pages 87 to 91, the ghost detection circuit used therein is based on vertical synchronization. The structure is such that the leading edge of the signal is used as the reference signal, and no consideration is given to cases where other signals are used as the reference signal.

[Problem that the invention seeks to solve]

Therefore, a reference signal for ghost removal as described in "Television Television Society 1981 National Conference Journal", pages 363 to 364, is transmitted from a certain broadcasting station to any location during the vertical blanking period. However, there is a problem in that it is not possible to perform ghost removal using this reference signal.

An object of the present invention is to detect a ghost based on the reference signal for ghost removal when the reference signal for ghost removal is sent to a certain location during the vertical blanking period, and to detect a ghost based on this signal when the reference signal is not sent. The present invention provides a ghost detection circuit capable of detecting ghosts based on the leading edge of a vertical synchronization signal.

[Means for solving problems]

The above purpose is to detect whether or not a ghost removal reference signal exists at a certain location during the vertical blanking period, and based on the detection result, decide whether to use the ghost removal reference signal as a reference signal for detecting a ghost. This is achieved by switching between using the leading edge of the vertical synchronization signal.

[Effect]

FIG. 2 is a diagram illustrating the present invention in detail.

In the figure, 201 is a video signal input terminal, 202 is a reference signal for ghost removal sent from the broadcasting station (
203 is a vertical synchronizing signal leading edge sampling circuit, 204 is a switch, 205 is a ghost detection circuit, 206 is a control signal for the switch circuit 204, and 207 is a signal detected by the ghost detection circuit 205. This is a ghost signal.

The video signal input to the input terminal 201 is
When the CR signal exists, the control signal flag closes the switch 204 to the α side, and when the OCR signal does not exist, the switch 204 is closed to the b side. With that, ghost detection times jii! The purpose of the present invention can be achieved because the signal to be input to 1 205 can be selected.

〔Example〕

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

In FIG. 1, the OCR signal is output as shown in FIG. 3 during an arbitrary horizontal period of the vertical blanking period.

This is an example in which a bar signal is sent.

In the figure, blocks with the same numbers as in Figure 2 indicate the same functional blocks. 101 is a synchronous separation circuit, 102
103 is an equalization pulse sampling circuit, 103 is a field discrimination circuit, ]04 is a preset value setting circuit, 1o5 is a counter, 106 is a pulse (divine) generation circuit, 107 is a pulse (M
10B is a pass Jl/pass (St) generation circuit, 109 is a counter, 110 is a pulse (St') generation circuit, 111 is a pulse (MASK') generation circuit, 112 is a pulse (St') ) generation circuit 113 is a midpoint detection circuit of the leading edge of the vertical synchronizing signal or the falling part of the OCR signal shown in FIG.

FIG. 4 shows an example of the configuration of the midpoint detection circuit 113 shown in FIG. 1.

In the figure, 401 to 403 are switches, 4o4 is a buffer circuit, 405 and 406 are switches, and 407 and 406 are switches.
08 is a capacitor, 409 is an average value generating circuit, 411 is a comparator, and 412 is an AND circuit.

The operations in the m1 diagram and FIG. 4 will be explained below with reference to the waveform diagram in FIG. 5.

First, the case where a ghost is detected using the leading edge of the vertical synchronization signal will be described with reference to FIG. 5(α).

A synchronization separation circuit 101 extracts a synchronization signal from a video signal input from an input terminal 201. An equalization pulse extraction circuit 102 extracts only the equalization pulse from this synchronization signal,
A counter 105 counts the number of equalization pulses, and a pulse generating circuit 106 generates an S1 pulse shown in FIG. 5 before the leading edge of the vertical synchronizing signal. As is well known, in television signals, the number of equalization pulses differs between odd and even fields, so the field discrimination port j! 2!103 determines whether the field is odd or even, and the preset value setting circuit 104 sets the preset value of the counter 105 so that it is O for an odd field and 1 for an even field. The pulse generating circuit 107 generates the MASK pulse shown in FIG. 5 from the falling edge of the S pulse, and the pulse generating circuit 810B generates the S pulse from the falling edge of the MASK pulse.

Switches 401 to 403 in the midpoint detection circuit 113 are closed to the b side by a control signal input from the terminal 206, and S is executed.

By closing switch 405 and Halste switch 406 with a pulse, the voltage values before and after the front line of the vertical synchronizing signal of the video signal that has passed through buffer circuit 404 are taken into capacitors 407 and 408.

The average value circuit 409 calculates the average of the voltage values taken into the capacitors 407 and 408, and the comparator 411 compares the average value M 409 with the video signal.
By performing an AND operation with the MASK pulse in step 12, a pulse that rises in synchronization with the fall of the Sl pulse and falls in synchronization with the midpoint of the leading edge of the vertical synchronization signal is obtained. Therefore, the ghost detection circuit 2 uses the falling edge of this pulse as a reference time.
05, it is possible to detect the ghost delay time, etc.

Next, using FIG.
A case will be described in which a ghost is detected using a bar signal (as shown in FIG. 3).

Generally, when inserting an arbitrary signal in the vertical blanking period, it is inserted after the trailing edge of the vertical synchronization signal, so for example, when an OCR signal is inserted at 18H (280H in an even field), explain.

The synchronization signal taken out to the output of the synchronization separation circuit 101 is
When counting by the counter 109 that is reset by the S pulse generated at the pulse generation time W8106, the S1 pulse occurs before the leading edge of the vertical synchronization signal, so if you count by 21, you can find the position where the OCR signal is inserted. I can find it. Therefore, from this signal, the pulse generation circuits 110 to 112 generate S, , M A shown in FIG. 5(A).
S f', S, generates a pulse and connects it to terminal 206
If the switches 401 to 403 are closed to the b side by the control signal input to It is possible to obtain a pulse that falls in synchronization with. Therefore, the ghost detection circuit 205 can detect the ghost delay time and the like using the fall of this pulse signal as a time reference.

The switches 401 to 403 in FIG. 4 may be switched manually, but the switches 401 to 403 in FIG.

Switches 401 to 403 automatically determine whether the OCR signal shown in FIG. It has the advantage of being easier to use.

FIG. 6 is a configuration example of an automatic switching circuit of switches 401 to 403.

In this figure, blocks with the same numbers as in FIG. 4 indicate the same functional blocks. 601 is a counter, 602 is a detection circuit in which the output of the counter 601 is 1, 603 is a latch circuit, and 604 is a latch pulse generation circuit of the latch circuit.

At the start of ghost detection, switches 401 to 401 in FIG.
403 to the α side, if the OCR signal shown in FIG.
Only one pulse occurs as shown in A). Therefore, the counter 601 is reset with the 5 pulse shown in FIG. , the output signal is sent to the latch circuit 603
Latch with. At this time, if the latch pulse of the latch circuit 603 is generated by the latch pulse generation circuit 604 after an arbitrary time from the start of ghost detection, the operation of the midpoint detection circuit 113 is sufficiently stable. 602
can latch the output signal. Therefore, the latch circuit 603
If the polarity of the output signal is set so that when the value of the counter 601 is 1, the switches 401 to 403 are closed to the b side, and in other cases, the switches 401 to 403 are closed to the α side, the latch The output signal of circuit 603 is transferred to switch 4
By using the signals as control signals for the switches 01 to 403, automatic switching of the switches 401 to 403 can be realized.

FIG. 7 shows another configuration example in which the switches 4-401 to 403 are automatically switched.

In the figure, 701 is a comparison circuit, and 702 is a waveform memory.

The OCR signal shown in FIG. 3 is stored in the waveform memory 702, and the comparison circuit 701 compares the signal at the position where the OCR signal is inserted into the video signal with the signal stored in the waveform memory 702. If the switches 401 to 403 are controlled according to the results, automatic switching becomes possible.

Further, the configuration example shown in FIG. 7 can also handle a pulse signal as shown in FIG. 8 or an OCR signal having any other arbitrary waveform as the OCR signal.

〔Effect of the invention〕

As described above, according to the present invention, a reference signal for ghost removal (OCR signal) is added to a signal sent from a broadcasting station.
If a signal is sent, the ghost can be detected using the OCR signal, and if it is not sent, the leading edge of the vertical synchronization signal can be used to detect the ghost, resulting in higher performance ghost detection. The circuit can be provided.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an embodiment of the present invention, Figure 2 is a block diagram explaining the invention in detail, Figure 3 is a waveform diagram showing an example of an OCR signal, and Figure w44 is a diagram of the midpoint detection circuit. 5.11 is a block diagram showing an example of the configuration, FIG. 5.11 is a waveform diagram explaining the operation of FIG. 4, FIG. FIG. 8 is a block diagram showing another example of the configuration of the automatic switching circuit of the switches 401 to 403, and a waveform diagram showing another example of the OCR signal. 101...Synchronization separation circuit 102...Equalizing pulse extraction circuit 103...Field discrimination circuit 104...Preset value setting circuit 105.109...Counter 10-108, 11 112...Pulse Generation circuit 1
13... Midpoint detection circuit 205... Coast detection circuit 401 to 403, 405, 406... Switch 407
, 408... Capacitor 409... Average value circuit 411... Comparator 412... AND times f
f. 601...Counter 602...1 detection circuit 603...Latch circuit 604...Latch pulse generation circuit 701...Comparison circuit 702...Waveform memory agent Patent attorney Katsuo Ogawa, 12° L + +-J 7, Figure 4 Figure 6 琐7 Figure 7θl Figure 8

Claims (1)

[Scope of Claims] 1. A leading edge extraction circuit that extracts the leading edge of a vertical synchronizing signal; a signal extraction circuit that extracts a signal inserted into a video signal portion of an arbitrary horizontal period of the vertical blanking period; A switch circuit that selects either the output signal of the signal extraction circuit or the output signal of the leading edge extraction circuit, and a ghost detection circuit that detects a ghost based on the output signal of the switch circuit, in which an arbitrary waveform is stored. comprising a waveform memory and a comparison circuit that compares an output signal of the waveform memory and an output signal of the signal sampling circuit, and in the comparison circuit, when the output signals of the waveform memory and the signal sampling circuit match, A ghost detection circuit characterized in that the switch circuit selects the output signal of the signal extraction circuit, and in other cases selects the output signal of the leading edge extraction circuit. 2. In the ghost detection circuit according to claim 1, the signal extraction circuit includes a midpoint detection circuit that detects the midpoint of the falling edge of the waveform, and a detection circuit that detects whether the midpoint detection circuit operates normally. If the midpoint detection circuit operates normally in the discrimination circuit,
A ghost detection circuit characterized in that the switch circuit selects the output signal of the signal extraction circuit, and in other cases selects the output signal of the leading edge extraction circuit.