JPH10210375A - Presence of absence deciding method for image synchronization signal and synchronization signal detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve validity and stability for decision of presence or absence of a synchronization signal. SOLUTION: A synchronization signal detection means 113 detects synchronization signals, included in the image signals and outputs a physical value deciding signal in response to the number of synchronizing signals which are detected in a fixed time. A decision means 112 compares a physical value deciding signal, outputted from the means 113 with the decision reference to decide the presence or absence of synchronization signals. A blind sector, having a variable width, is set for the decision reference of the means 112. Then a control means 110 changes the width of the blind sector to zero or the small value for a fixed time, when a signal to which the input of the image signals is switched is inputted. Thus, the stable decision is assured of a normal state by the decision reference having a blind sector. Then the width of the blind sector is reduced in a switching mode of the image signals. As a result, valid decision is assured, even when a non-signal channel is switched to a channel of a weak electric field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the presence or absence of an image synchronization signal for determining the presence or absence of a synchronization signal included in an image signal such as a television signal or a video signal, a synchronization signal detection system using the method, and a synchronization signal detection system. The present invention relates to a used television receiver.

[0002]

2. Description of the Related Art In a general television receiver, various controls are performed by confirming at a television signal input terminal whether or not a television signal selected by a channel or the like has been input. For example, if there is no television signal input, the entire screen is displayed in blue, the tuner is scanned to determine the selected channel, or the like. Control is performed such as skipping the channel having no symbol at the time of the next forward switching operation. In addition, not only the presence / absence of the input of the television signal but also the presence / absence of the input of the image signal such as the video signal, various controls are similarly performed.

[0003] As a method of confirming the presence or absence of input of an image signal such as a television signal, a method of detecting a synchronization signal included in the image signal at an input terminal is often employed. Usually, a horizontal synchronizing signal is used as the signal.

Next, an example of a conventional method for detecting the presence or absence of a synchronization signal will be described. Normally, the noise component of the television signal input from the input terminal is attenuated by the filter circuit, and the synchronization signal included in the television signal is separated by the synchronization signal separation circuit. Since the synchronization signal separated by the synchronization signal separation circuit is not stable due to the strength of radio waves and noise, the signal is shaped by, for example, a circuit called a PLL circuit, and then output from an output terminal to each section of the receiver. This PLL circuit generates a synchronizing signal close to the frequency of the original synchronizing signal by a synchronizing signal generator based on a variable frequency clock output from a voltage-controlled oscillator, and uses the synchronizing signal and a synchronizing signal separating circuit. The phase of the separated synchronization signal is compared, and the control voltage of the oscillator is adjusted so as to reduce the phase difference. As a result, P
The synchronization signal output from the synchronization signal generator of the LL circuit is:
The phase matches the synchronization signal included in the television signal,
In addition, a stable synchronized signal is obtained. When the synchronization signal included in the television signal is input relatively stably and is in the same phase as the synchronization signal generated from the PLL circuit, that is, when the synchronization is locked, the phase comparison of the PLL circuit is performed. The control voltage applied to the oscillator from the oscillator stabilizes at a specific voltage determined by the frequency of the synchronization signal. However, if an image signal such as a television signal is not input to the input terminal, or if the signal is very weak, the synchronization signal is not detected, so that the control voltage having a value corresponding to the time during which the synchronization signal is not detected from the phase comparator is increased. It will be input to the oscillator.

Therefore, conventionally, it has been proposed to determine the presence or absence of a synchronization signal by observing the output of a phase comparator of a PLL circuit. For example, the control voltage output from the phase comparator can be integrated by an integrator, and the presence or absence of a synchronization signal can be determined based on the magnitude of the integrated value. In other words, the presence / absence of a synchronization signal can be determined by comparing the integrated value (eigenvalue) of the control voltage in the state where the synchronization is locked with the actual integrated value of the control voltage as a reference value. For example, the absolute value of a difference between the reference value and the actual integrated value of the control voltage (hereinafter, referred to as a difference value) is obtained, and the presence or absence of the synchronization signal is determined based on whether the difference value exceeds a predetermined determination reference value. Can be determined.

However, when one threshold value is set as a determination reference value, if the integrated value of the control voltage is not stable and the difference value changes in an unstable manner, the determination of the presence or absence of the synchronization signal may not be stable. . This is because, for example, when a television signal of a weak electric field is received, the synchronization signal cannot be correctly separated due to the influence of noise components that cannot be removed by the filter circuit, and the control voltage output from the phase comparator is unstable. It can happen by becoming. In such a state, it is appropriate to determine that there is no synchronization signal.

Therefore, in order to improve such unstable determination, it is general that the criterion is not a single threshold but a threshold having a dead zone. That is,
According to this, while the difference value is included in the dead zone, the previous determination result is held, so that the determination result of the synchronization signal with respect to a small change can be stabilized.

[0008]

However, by setting a dead zone as a criterion for determining the presence or absence of a synchronization signal as in the prior art, a relatively stable determination result can be obtained. There is such a problem.

For example, once the difference value exceeds the upper limit value of the dead band and enters the determination region where there is no synchronization signal, unless the difference value falls below the determination region where the synchronization signal exists below the lower limit value of the dead band, there is no synchronization signal. Will continue. Therefore, even if the difference is smaller than the original determination reference value corresponding to the integral value of the control voltage in the state where the synchronization is locked, the determination of the absence of the synchronization signal is continued. There is a problem that cannot be performed.

In other words, when there is a channel of a weak electric field having a difference value within the width of the dead zone, and when switching from a channel of a normal electric field strength to a channel of a weak electric field, the presence of a synchronization signal continues. There is no problem because the determination can be obtained, but when switching from a channel with no signal to a channel with a weak electric field, the determination is made that there is no synchronization signal, and the determination result of the presence or absence of the synchronization signal differs depending on the channel switching method. There are inconveniences.

When the power is turned on, there is no synchronization signal.
If the channel selected at that time is a weak electric field channel, there is always a disadvantage that determination is made that there is no synchronization signal.

An object of the present invention is to improve the validity or stability of the determination of the presence or absence of a synchronization signal.

[0013]

The object of the present invention is to determine the presence or absence of a synchronization signal based on a determination signal obtained by detecting a synchronization signal included in an image signal, based on a determination criterion having a dead zone. This can be solved by changing the width of the dead zone from zero to a small width for a certain time when the signal input is switched.

That is, by setting a dead zone as a criterion, in a normal state, as in the conventional case, the instability of determining the presence or absence of a synchronization signal due to noise or the like is avoided, and a relatively stable determination result is obtained. be able to. On the other hand, when the input of the image signal is switched, such as when switching channels, when switching between television and video, or when turning on the power, the width of the dead zone of the determination criterion is zero, that is, there is no dead zone. Since it is changed to a judgment criterion or a dead band having a small width, it is possible to correctly determine the presence or absence of a synchronization signal even for a determination signal having a degree within the width of a normal dead band. Can be determined. Then, even after returning to the original determination criterion after a certain period of time, the criterion for the dead zone is applied based on the determination result before the return, so that an appropriate determination can be made.

For example, when there is a channel of a weak electric field in which the determination signal enters a normal dead zone,
When switching from a no-signal channel or a power-off state to a channel with a weak electric field, according to a criterion having a normal dead zone, an erroneous determination of no synchronization signal continues, but according to the present invention, Since the dead zone of the criterion is changed to zero or a small width at the time of such switching, such erroneous determination can be reduced. That is,
The result of the determination is that there is a synchronization signal. Then, even after returning to the normal criterion having a dead zone after a certain period of time, the determination result of the presence of the synchronization signal is retained, so that the validity can be ensured.

In the above solution, a physical quantity signal corresponding to the number of synchronization signals detected within a predetermined time can be used as the synchronization signal determination signal. For example, means for detecting a synchronization signal included in an image signal generates an oscillator that generates a signal having a frequency corresponding to a given control voltage, and generates a synchronization signal having a frequency that corresponds to the frequency of a signal output from the oscillator. A synchronous signal generator, a phase comparator that compares the phases of a synchronous signal output from the synchronous signal generator and a synchronous signal included in the image signal, and controls a control voltage of the oscillator according to a phase difference between them. , A physical quantity obtained by integrating the control voltage input to the oscillator can be used as the determination signal. That is, the physical quantity obtained by integrating the control voltage becomes a signal corresponding to the phase difference between the two synchronization signals. If the synchronization signal included in the image signal cannot be detected, the phase difference is substantially evaluated to be large, and the control voltage is integrated. The obtained physical quantity has a large value.

Alternatively, when a pulse signal is generated by detecting a synchronization signal, the pulse can be used as a determination signal. The criterion in this case is set corresponding to a count value obtained by counting the pulses for a certain period of time.

Further, the number of the same judgment results related to the judgment is counted for a certain period of time after the judgment is made based on the first judgment criterion having one threshold value by one judgment threshold value. The presence or absence of a synchronization signal may be determined based on a second determination criterion having the following. Even in such a case, when the input of the image signal is switched, it is preferable to change the threshold value of the second determination criterion from zero to a small value for a certain period of time.
Alternatively, a dead zone may be provided in the second determination criterion, and when the input of the image signal is switched, the width of the dead zone may be changed from zero to a small width for a certain period of time.

A circuit for determining the presence or absence of the synchronization signal described above;
Alternatively, a synchronization detection system using the same can be easily formed by using a discrete electronic circuit or a microprocessor, or can be easily formed by combining an electronic circuit and a microprocessor.

As another means for solving the above-mentioned problem, the presence or absence of a synchronization signal is determined based on a determination signal obtained by detecting a synchronization signal included in an image signal by a determination criterion having a dead zone, and When the input is switched,
The determination signal may be generated so as to forcibly determine that the synchronization signal is present for a predetermined time.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a synchronization signal detection system to which an image synchronization signal presence / absence determination method according to the first embodiment of the present invention is applied. As illustrated, an input terminal 101 to which an image signal such as a television signal or a video signal (hereinafter, a television signal will be described as an example) is input, a filter circuit 102, and a synchronization signal separation circuit 103. , Phase comparator 104, synchronization signal generator 105, synchronization signal output terminal 106, oscillator 107, integrator 108, and switching signal input terminal 109.
Control means 110, a synchronization signal presence / absence determination unit 111,
It comprises an output terminal 112 for outputting a determination result of the presence or absence of a synchronization signal. Note that a circuit including the filter circuit 102, the synchronization signal separation circuit 103, the phase comparator 104, the synchronization signal generator 105, the oscillator 107, and the integrator 108 is referred to as a synchronization signal detection circuit 113. I do. The synchronization signal detection circuit detects a synchronization signal from the television signal and outputs a signal for determining the presence or absence of synchronization from the integrator 108. Further, a phase comparator 104, a synchronization signal generator 105, and an oscillator 107
Is a PLL circuit.

Next, the detailed configuration of the synchronization signal detection system of FIG. 1 will be described along with the operation. The television signal input from the input terminal 101 passes through the filter circuit 102, where the noise component included in the television signal is attenuated, and is input to the synchronization signal separation circuit 103. The synchronization signal separation circuit 103 detects a synchronization signal of horizontal synchronization from the television signal and inputs the signal to the phase comparator 104. On the other hand, the synchronizing signal generator 105 generates a synchronizing signal having a frequency corresponding to the clock output from the oscillator 107, inputs the synchronizing signal to the phase comparator 104, and outputs the synchronizing signal from the output terminal 106 to each part of the television receiver. It has become. The phase comparator 104 controls the control voltage of the transmitter 107 so that the two input synchronization signals have the same phase. The oscillator 107 is a voltage-controlled oscillator that can control the oscillation frequency with an external control voltage. Oscillator 107
Is stabilized at a constant voltage when the two synchronization signals input to the phase comparator 104 have the same phase.
The stable voltage is a specific voltage corresponding to a predetermined frequency of the synchronization signal. The control voltage output from the phase comparator 104 is integrated by the integrator 108 and input to the synchronization signal presence / absence determination unit 111 as a synchronization signal presence / absence determination signal.

Here, the detailed configuration of the synchronization signal presence / absence determiner 111 and the control means 110 will be described together with the operation. A reference value corresponding to the output signal of the integrator 108 in a state where the two synchronization signals have the same phase in the synchronization signal detection circuit 113, that is, in a state where the synchronization is locked, is set in the synchronization signal presence / absence determination unit 111. . Then, the synchronization signal presence / absence determiner 111 samples the determination signal output from the integrator 108 (for example, 60 times per second), and calculates the absolute value of the difference between the sampled determination signal and its reference value (this Is referred to as a difference value D). The synchronization signal presence / absence determination unit 111 has two types of determination criteria a and b for determining the presence / absence of a synchronization signal based on the difference value D. These criteria a and b are shown in FIG.
(B). As a criterion a, the difference value D obtained in the current sampling is compared with a threshold value Q, and as shown in FIG. 2A, when D ≧ Q, there is no synchronization signal, and when D <Q, The result of the determination of the presence of the synchronization signal is output. On the other hand, the determination criterion b is obtained by comparing the difference value D obtained in the current sampling with two thresholds P and Q (where P> Q).
As shown in (b), when D ≧ Q, the result of determination that there is no synchronization signal is output, when D <P, the result of determination that there is a synchronization signal is output, and when P ≦ D <Q, Is held in the determination result at the time of the previous sampling. In other words, a so-called dead zone of the PQ width is set as the criterion b. Then, the synchronization signal presence / absence determining unit 111 is set so as to make a determination based on the determination criterion b in a normal state.

On the other hand, the control means 110 has an input terminal 10
A switching signal indicating that the input of the television signal has been switched from 9 is input. That is, this switching signal
This indicates that the television signal input from the input terminal 101 has been switched, and is, for example, a channel switching signal, a television / video switching signal, a power-on signal, or the like. When the switching signal is input, control means 110 determines that the television signal has been switched, and outputs a command to change the determination criterion of synchronization signal presence / absence determination section 111 to synchronization signal presence / absence determination section 111. That is,
When the switching signal is input, the synchronization signal presence / absence determination unit 1
11, a command to change the criterion b to the criterion a is output, and the output of the command is stopped after a predetermined time has elapsed.

In response to such a command from the control means 110, the synchronization signal presence / absence determination unit 111 immediately switches the determination criterion from b to a, and determines the presence / absence of the synchronization signal presence / absence for the sampled difference value D using the determination criterion a. Make a decision. Then, in response to the stop of the switching command after a certain period of time, the criterion is returned to the original criterion b.

Thus, when the television signal is switched, the state of the determination result of the synchronization signal presence / absence determiner 111 is updated to the determination result based on the determination criterion a having no dead zone at the time of switching. be able to. Thereafter, the determination result based on the determination criterion a is used as the determination result at the previous sampling, and the determination of the presence or absence of the synchronization signal is performed using the determination criterion b.
Is switched to a television signal of a weak electric field such as D = X that falls within the width PQ of the dead zone, without being affected by the determination result of D = Y (for example, no signal) at the previous sampling, It is possible to obtain a correct determination result indicating that there is a synchronization signal and obtain a stable determination result.

In the synchronization signal detection system of FIG. 1, an example in which a physical quantity signal obtained by integrating the control voltage value of the oscillator 107 of the synchronization signal detection circuit 113 is used as a determination signal, and the presence or absence of the synchronization signal is determined based on this signal. Was shown,
The present invention is not limited to this, and the present invention can be applied to any synchronous signal detection circuit configured to output a signal indicating the presence or absence of a synchronous signal, for example, a physical quantity signal according to the number of synchronous signals detected within a certain time. For example, since the frequency of the horizontal synchronization signal is set to 15.75 Hz according to the standard, the synchronization signal may be detected and counted using a clock of that frequency, and the count value may be used. In this case, the criterion can be determined based on whether or not the count value within a certain period of time is equal to or more than a predetermined value, and it is also possible to provide a dead zone in the criterion. In addition, for example, when the number of scanning lines per frame is set to 525, it is possible to detect the presence or absence of a synchronization signal by counting the number of scanning lines.

FIG. 3 shows a block diagram of a synchronization signal detection system to which the method for determining the presence or absence of an image synchronization signal according to the second embodiment of the present invention is applied. As shown in the figure, the system according to the present embodiment includes a television signal input terminal 101, a synchronization signal detection circuit 113, a synchronization signal presence / absence determination unit 201, a control unit 202, and a synchronization presence / absence determination result. An output terminal 112 and a synchronization signal output terminal 106 are provided. The present embodiment is an example in which the criterion of the synchronization signal presence / absence determiner 201 is fixed to the criterion a and cannot be changed.

Next, the detailed configuration of this embodiment will be described together with the operation. 3, components equivalent to those in the embodiment of FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. The signal for determining the presence or absence of a synchronization signal output from the synchronization signal detection circuit 113 is input to the synchronization signal presence / absence determiner 201. The synchronization signal presence / absence determination unit 201 cannot change the determination criterion, and determines the presence or absence of the synchronization signal only based on the determination criterion a shown in FIG. 2A. Input to the means 202. The control means 202 re-determines the presence / absence of a synchronization signal based on the signal of the input determination result in order to stabilize the determination result input from the synchronization signal presence / absence determining unit 201. The criterion for determining the presence or absence of the synchronization signal in the control means 202 can be changed by a command given from the outside. That is, there are provided the determination criteria corresponding to the two determination criteria a and b shown in FIG. And
The judgment result output from the control means 201 is output terminal 1
12 to each part of the television receiver.

In particular, the determination of the presence / absence of the synchronization signal by the control means 202 is performed by sampling the determination result from the synchronization signal presence / absence determiner 201 and determining the number of identical determination results within an arbitrarily determined time (the presence of the synchronization signal or the synchronization The number of times of the determination result of the absence of a signal) is counted, and the number is compared with the threshold values of the determination criteria a and b to make the determination. By controlling this determination criterion with an external switching signal as described in the first embodiment, the same effect can be obtained.

FIG. 4 shows a block diagram of a synchronization signal detection system to which the method for determining the presence or absence of an image synchronization signal according to the third embodiment of the present invention is applied. As shown in the figure, the system according to the present embodiment includes a television signal input terminal 10.
1, a signal switching circuit 301, and a synchronization signal detection circuit 302
Synchronization signal presence / absence determiner 303, control means 304,
It comprises an output terminal 112 for the result of determination of the presence / absence of a synchronization signal and a synchronization signal output terminal 106. In this embodiment,
This is an example in which the criterion of the synchronization signal presence / absence determiner 302 is fixed to the criterion b of FIG. 2 and cannot be changed.

The detailed configuration of the synchronization signal detection system having the above-described configuration shown in FIG. The television signal input from the input terminal 101 is input to the signal switching circuit 301. The synchronization signal output from the synchronization signal detection circuit 302 is input to the signal switching circuit 301. The signal switching circuit 301 includes the synchronization signal detection circuit 30
A signal selected by the control unit 304 from the synchronization signal output from the input terminal 2 and the television signal input from the input terminal 101 is output to the synchronization signal detection circuit 302. The synchronization signal detection circuit 302 has a function of shutting off the control voltage of the oscillator in response to a control command given from the external control means 304, in addition to the function of the synchronization signal detection circuit 113 shown in FIG. Thus, a free-run synchronization signal can be output.
The synchronization signal output from the synchronization signal detection circuit 302 is input to the synchronization signal presence / absence determination unit 303. The determination result determined by the synchronization signal presence / absence determiner 303 is output terminal 1
12 is output. The synchronization signal presence / absence determination unit 303 does not control the determination criterion from the outside, and performs the synchronization presence / absence determination only based on the determination criterion b. Control means 304
Controls the signal switching circuit 301 and the synchronization signal detection circuit 302 based on the switching signal input from the input terminal 109.

Here, the detailed operation of the control means 304 will be described. Normally, the control means 304 controls the synchronization signal detection circuit 30 to output the television signal input from the input terminal 101.
2 to be input. Then, a switching signal indicating that the television signal has been switched is transmitted to the control unit 304.
, First, the synchronization signal detection circuit 302 controls so as to output a free-run synchronization signal. further,
The signal switching circuit 301 is controlled so that the free-run synchronization signal is input to the synchronization signal detection circuit 302. At this time, since the same synchronization signal as that output by itself is input to the synchronization signal detection circuit 302, the synchronization signal detection circuit 302 outputs a determination signal corresponding to the presence of the synchronization signal. This determination signal is output from the integrator 108 in FIG.
Is the same as the output of Therefore, the synchronization signal presence / absence determination unit 303 outputs a determination result indicating that there is a synchronization signal. After elapse of an arbitrarily set time, the control means 302 outputs a command to stop the free-run to the synchronization signal detection circuit 302 and causes the television signal from the input terminal 101 to be input to the synchronization signal detection circuit 302. To control the signal switching circuit 301. By this control, at the time when the television signal is switched, the synchronization signal presence / absence determining unit 303 is forcibly set to the state with synchronization.
As described in the example of the related art, it is possible to correctly determine the presence or absence of a synchronization signal even when switching from a no-signal to a television signal of a weak electric field.

FIG. 5 is a block diagram according to a fourth embodiment in which the method for determining the presence or absence of an image synchronization signal according to the present invention is applied to a wide-screen television receiver. As shown,
The wide television receiver has an RF signal input terminal 401
, Tuner 402, signal switching circuit 403, Y / C
Separation circuit 404, color demodulation circuit 405, time axis compression circuit 406, RGB signal processing circuit 407, deflection control circuit 408, CPT 409, video signal input terminal 41
0 and an external control signal input terminal 411 such as a remote controller
, A system control means 412 for controlling the entire wide television receiver, a screen display control circuit 413, a synchronization signal detection circuit 302, and a synchronization signal presence / absence determination circuit 111. The blocks denoted by the same reference numerals as those of the other embodiments have the same functional configuration.

Next, the operation of the wide television receiver shown in FIG. 5 will be described. The RF signal input from the RF signal input terminal 401 is converted into a television signal by the tuner 402 and input to the signal switching circuit 403. The television signal (video signal) input from the video signal input terminal 410 is input to the signal switching circuit 403.
Is input to The signal switching circuit 403 converts the television signal whose display is selected by the system control unit 412 into a Y / C separation circuit 404 and a synchronization signal detection circuit 302.
To enter. The television signal input to the Y / C separation circuit 404 is supplied to a color demodulation circuit 405 and a time axis compression circuit 40.
6. The signal is input to the CPT 409 via the RGB signal processing circuit 407 and the deflection control circuit 408, and is displayed as an image.

On the other hand, the synchronization signal detection circuit 302 detects a synchronization signal from the input television signal, and
In addition to the input to the GB signal processing circuit 407, a signal for determining the presence or absence of a synchronization signal (the output signal of the integrator 108 in FIG. 1) is input to the synchronization signal presence / absence determination circuit 111. The synchronization signal presence / absence determination circuit 111 uses the same determination criteria a,
b, the presence / absence of a synchronization signal is determined based on the determination signal sampled in step b.
Input to 12. The system control unit 412 performs channel switching and input switching according to an external control signal (switching signal) such as a remote controller input from the input terminal 411. Since the television signal input to the synchronization signal detection circuit 302 is switched in accordance with this switching, the criterion of the synchronization signal presence / absence determination circuit 111 is controlled in the same manner as in the embodiment of FIG.

This embodiment is an embodiment in which the functional operation of the control means 110 in the embodiment of FIG. 1 is incorporated in a system control means 412 for controlling the entire wide-screen television. Further, even when the synchronization signal presence / absence determination circuit 201 of the second embodiment shown in FIG. 3 is applied as the synchronization signal presence / absence determination circuit 111, the present invention is implemented by performing the functional operation of the control unit 202 by the system control unit 412. can do.

FIG. 6 is a block diagram according to a fifth embodiment in which the present invention is applied to a wide-screen television receiver. This embodiment is different from the embodiment shown in FIG.
1, the synchronization signal presence / absence determination circuit 111 and the system control means 412 are respectively connected to the synchronization signal presence / absence determination circuit 30
3. It is replaced with system control means 502.
As described in the third embodiment of FIG. 4, the synchronization signal presence / absence determination circuit 303 does not control the determination criterion from outside, and determines the presence / absence of the synchronization signal with the determination criterion b fixed. At this time, the system control means 502
The present invention can be implemented by controlling the signal switching circuit 501 and the synchronization signal detection circuit 302 as in the case of the fourth embodiment.

[0039]

As described above, according to the present invention,
The validity and stability of the determination of the presence / absence of the synchronization signal can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a synchronization signal detection system to which an image synchronization signal presence / absence determination method according to a first embodiment of the present invention is applied.

FIG. 2 is a diagram illustrating a criterion of an image synchronization signal presence / absence determination method according to the present invention.

FIG. 3 is a block diagram of a synchronization signal detection system to which an image synchronization signal presence / absence determination method according to a second embodiment of the present invention is applied.

FIG. 4 is a block diagram of a synchronization signal detection system to which an image synchronization signal presence / absence determination method according to a third embodiment of the present invention is applied.

FIG. 5 is a block diagram of a wide television receiver to which the method for determining the presence or absence of an image synchronization signal according to the first embodiment of the present invention is applied.

FIG. 6 is a block diagram of a wide television receiver to which a method for determining the presence or absence of an image synchronization signal according to a third embodiment of the present invention is applied.

[Explanation of symbols]

 Reference Signs List 102 filter circuit 103 synchronization signal separation circuit 104 phase comparator 105 synchronization signal generator 107 oscillator 108 integrator 110 control means 111 synchronization signal presence / absence determination device 113 synchronization signal detection circuit 201 synchronization signal presence / absence determination device 202 control means 301 signal switching circuit 302 Synchronous signal detection circuit 303 Synchronous signal presence / absence determination circuit 304 Control means 401 RF signal input terminal 402 Tuner 403 Signal switching circuit 404 Y / C separation circuit 405 Color demodulation circuit 406 Time axis compression circuit 407 RGB signal processing circuit 408 Deflection control circuit 409 CRT 410 Video input terminal 411 Control signal input terminal 412 System control means 413 Screen display control circuit 501 Signal switching circuit 502 System control means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takaaki Matino 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Visual Information Media Division of Hitachi, Ltd. (72) Inventor Takahiro Mizuguchi Yoshida, Totsuka-ku, Yokohama-shi, Kanagawa (292) Inventor Yoshiji Okada 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. Hitachi Image Information Systems, Inc.

Claims (17)

[Claims] 1. The method according to claim 1, wherein the presence or absence of the synchronization signal is determined based on a determination signal obtained by detecting a synchronization signal included in the image signal, based on a determination criterion having a dead zone, and when the input of the image signal is switched. A method for determining the presence or absence of an image synchronization signal for changing the width of the dead zone from zero to a small width for a predetermined time. 2. The method according to claim 1, wherein the determination signal is a physical quantity corresponding to the number of the synchronization signals detected within a predetermined time. A method for determining the presence or absence of a synchronization signal. 3. The method according to claim 1, wherein the determination signal is a pulse signal generated when the synchronization signal is detected, and the determination criterion is the pulse signal. A method for determining the presence or absence of an image synchronization signal, wherein the method is set in accordance with a count value obtained by counting a signal for a predetermined time. 4. A method according to claim 1, wherein a presence / absence of the synchronization signal is determined based on a determination signal obtained by detecting a synchronization signal included in the image signal, based on a first determination criterion having one threshold value.
The number of the same judgment result related to the judgment is counted for a certain period of time, and 1
The presence / absence of the synchronization signal is determined by a second determination criterion having two threshold values, and when the input of the image signal is switched, the threshold value of the second determination criterion is reduced to zero to a small value for a predetermined time. A method for determining the presence or absence of an image synchronization signal to be changed. 5. A method according to claim 1, wherein a presence / absence of the synchronization signal is determined based on a determination signal obtained by detecting a synchronization signal included in the image signal, based on a first determination criterion having one threshold value.
When the number of the same determination result related to the determination is counted for a certain period of time and the presence or absence of the synchronization signal is determined based on a second determination criterion having a dead zone, when the input of the image signal is switched,
A method for determining the presence or absence of an image synchronization signal for changing the width of the dead zone to zero to a small width for a predetermined time. 6. The method according to claim 4, wherein the determination signal is a physical quantity corresponding to the number of the synchronization signals detected within a predetermined time. Method for determining the presence or absence of an image synchronization signal to be performed. 7. A synchronizing signal included in the image signal is detected,
A synchronization signal detection unit that outputs a determination signal of a physical quantity according to the number of synchronization signals detected within a predetermined time, and a determination unit that determines the presence or absence of the synchronization signal by comparing the determination signal with a determination reference. In the synchronization signal detection system, the criterion of the determination means is a variable width dead zone set, and the width of the dead zone is fixed when a signal to which the input of the image signal is switched is input. A synchronization signal detection system, comprising a control means for changing the time from zero to a small width. 8. The synchronization signal detection system according to claim 7, wherein the synchronization signal detection means includes an oscillator for generating a signal having a frequency corresponding to a given control voltage, and a frequency of a signal output from the oscillator. A synchronization signal generator that generates a synchronization signal having a frequency corresponding to the synchronization signal, and a phase of a synchronization signal included in the image signal and a synchronization signal output from the synchronization signal generator are compared.
Synchronous signal detection, comprising: a phase comparator for controlling a control voltage of the oscillator in accordance with the phase difference; and integrating means for integrating the control voltage and outputting the determination signal. system. 9. The synchronization signal detection system according to claim 7, wherein the synchronization signal detection unit detects whether or not a synchronization signal included in the image signal is input in accordance with a predetermined cycle of the synchronization signal. And outputting a pulse signal as the determination signal every time the synchronization signal is detected. 10. A synchronizing signal detecting means for detecting a synchronizing signal included in an image signal and outputting a signal for judging a physical quantity according to the number of synchronizing signals detected within a predetermined time, and fetching the judging signal. A determination means for determining the presence or absence of the synchronization signal by comparing the determination signal with a determination criterion, wherein the determination means determines whether the determination signal output from the synchronization signal detection means is one. A determination is made based on a first determination criterion having a threshold value, the number of the same determination results related to the determination is counted for a certain period of time, and the presence or absence of the synchronization signal is determined based on a second determination criterion having one threshold value And a control means for changing a threshold value of the second determination criterion from zero to a small value for a certain period of time when the input of the image signal is switched. Shi Temu. 11. A synchronizing signal detecting means for detecting a synchronizing signal included in an image signal and outputting a signal for judging a physical quantity according to the number of synchronizing signals detected within a predetermined time, and fetching the judging signal. A determination means for determining the presence or absence of the synchronization signal by comparing the determination signal with a determination criterion, wherein the determination means determines whether the determination signal output from the synchronization signal detection means is one. Judgment is made by a first judgment criterion having a threshold value, the number of the same judgment results related to the judgment is counted for a certain period of time, and by a second judgment criterion having a dead zone,
Determining whether or not the synchronization signal is present, wherein the synchronization signal is provided with control means for changing the width of the dead zone from zero to a small width for a predetermined time when the input of the image signal is switched. Detection system. 12. The synchronization signal detection system according to claim 10, wherein said synchronization signal detection means includes an oscillator for generating a signal having a frequency corresponding to a control voltage supplied thereto, and a signal output from said oscillator. A synchronization signal generator that generates a synchronization signal having a frequency corresponding to the frequency, and a phase of the synchronization signal included in the image signal and a synchronization signal output from the synchronization signal generator are compared.
Synchronous signal detection, comprising: a phase comparator for controlling a control voltage of the oscillator in accordance with the phase difference; and integrating means for integrating the control voltage and outputting the determination signal. system. 13. When the input of the image signal is switched, the presence or absence of the synchronization signal is determined based on a determination signal obtained by detecting a synchronization signal included in the image signal, based on a determination criterion having a dead zone. And a method for determining the presence or absence of an image synchronization signal for forcibly determining that the synchronization signal exists. 14. An oscillator comprising a signal switching unit, a synchronization signal detection unit, a synchronization signal presence / absence determination unit, and a control unit, wherein the synchronization signal detection unit generates a signal having a frequency corresponding to a given control voltage. And a synchronization signal generator for generating a synchronization signal having a frequency corresponding to the frequency of the signal output from the oscillator, and comparing the phase of the synchronization signal output from the synchronization signal generator with the phase of the synchronization signal included in the image signal. And
A phase comparator that controls a control voltage of the oscillator according to the phase difference, an integrating unit that integrates the control voltage and outputs a determination signal, and a unit that cuts off a control voltage input to the oscillator. And outputting a synchronizing signal output from the synchronizing signal generator to each section of the television receiver. The signal switching means outputs the synchronizing signal input together with the image signal and the synchronizing signal detecting means. The synchronization signal is switched and output in accordance with a given command, and the determination unit compares the determination signal output from the synchronization signal detection unit with a determination criterion having a certain dead zone to determine the synchronization signal. The control means outputs a control voltage cutoff command to the synchronization signal detection means when the input of the image signal is switched. Both the synchronization signal detection system, characterized in that said at the outputs a switching command for outputting the synchronizing signal output from the synchronization signal detecting means to the switching means. 15. A tuner for converting an input RF signal into a television signal, a signal switching circuit for switching between an input video signal and a television signal output from the tuner and outputting one image signal. A Y / C separation circuit for processing an image signal output from the signal switching circuit, a color demodulation circuit, an RGB signal processing circuit, and a CRT according to the image signal output from the RGB signal processing circuit. A deflection control circuit for displaying an image on a CRT, a synchronization signal included in the image signal output from the signal switching circuit, and a determination signal of a physical quantity corresponding to the number of synchronization signals detected within a predetermined time; A synchronizing signal detection circuit for outputting, and a judging circuit for judging the presence or absence of the synchronizing signal by comparing the judging signal with a judging reference. In a television receiver that performs image display control, a criterion of the determination circuit is set to a variable width dead zone, and input switching of an image signal including a television signal selection instruction and a video signal selection instruction is performed. A television receiver provided with control means for changing the width of the dead zone to zero or a small width for a predetermined time when a signal is input. 16. A tuner for converting an input RF signal into a television signal, a signal switching circuit for switching between an input video signal and a television signal output from the tuner and outputting one image signal. A Y / C separation circuit for processing an image signal output from the signal switching circuit, a color demodulation circuit, an RGB signal processing circuit, and a CRT according to the image signal output from the RGB signal processing circuit. A deflection control circuit for displaying an image on a CRT, a synchronization signal included in the image signal output from the signal switching circuit, and a determination signal of a physical quantity corresponding to the number of synchronization signals detected within a predetermined time; A synchronizing signal detection circuit for outputting, and a judging circuit for judging the presence or absence of the synchronizing signal by comparing the judging signal with a judging reference. In a television receiver that performs image display control, the determination circuit determines the determination signal output from the synchronization signal detection circuit based on a first determination criterion having one threshold. The presence / absence of the synchronization signal is determined based on a second determination criterion having one threshold value by counting the number of the same determination results for a certain period of time. The channel selection command of the television signal and the video signal And a control circuit for changing a threshold value of the second determination criterion from zero to a small value for a predetermined time when an input switching signal of an image signal including the selection command is input. Receiver. 17. A tuner for converting an input RF signal into a television signal, a signal switching circuit for switching between an input video signal and a television signal output from the tuner and outputting one image signal. A Y / C separation circuit for processing an image signal output from the signal switching circuit, a color demodulation circuit, an RGB signal processing circuit, and a CRT according to the image signal output from the RGB signal processing circuit. A deflection control circuit for displaying an image on a CRT, a synchronization signal included in the image signal output from the signal switching circuit, and a determination signal of a physical quantity corresponding to the number of synchronization signals detected within a predetermined time; A synchronizing signal detection circuit for outputting, and a judging circuit for judging the presence or absence of the synchronizing signal by comparing the judging signal with a judging reference. In a television receiver that performs image display control, the determination circuit determines the determination signal output from the synchronization signal detection circuit based on a first determination criterion having one threshold. The number of the same judgment result is counted for a certain period of time, and according to the second judgment criterion having a dead zone,
The presence or absence of the synchronization signal is determined, and when an input switching signal of an image signal including a selection command of the television signal and a selection command of the video signal is input, the width of the dead zone is set to zero to a small width. A television receiver, further comprising a control circuit for changing a predetermined period of time.