JPH1049093A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device capable of preventing picture disturbance from occurring during a follow-up time of a synchronizing circuit. SOLUTION: This device is provided with a synchronizing signal separation circuit extracting a horizontal synchronizing signal from a video signal, a horizontal oscillation circuit 9, a synchronizing circuit 10 for controlling the horizontal oscillation circuit 9 so as to match the frequency and phase of the output pulse signal of the horizontal oscillation circuit 9 with those of a horizontal synchronizing signal, a detection circuit 13, and a blanking circuit 19. The detection circuit 13 detects mis-matching between the frequency and phase of the horizontal synchronizing signal and those of the output signal of the horizontal oscillation circuit 9. The blanking circuit 19 halts displaying a picture on a screen while a mis-matching is being detected by the detection circuit 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, and more particularly to a multi-scan display device capable of displaying an image at a plurality of synchronization frequencies.

[0002]

2. Description of the Related Art Conventionally, there is a multi-scan type display device capable of displaying an image at a plurality of horizontal and vertical synchronization frequencies. In this display device, when the synchronization signal frequency of the input video signal is switched or when the phase of the synchronization signal changes, the synchronization circuit
The oscillation frequency and the oscillation timing of the oscillation circuit in the display device are matched with the frequency and phase of the synchronization signal, and the oscillation signal from the oscillation circuit is supplied to the deflection circuit. By doing so, an image can be displayed even when the synchronization signal frequency of the input video signal is switched or when the phase of the synchronization signal is changed.

As shown in FIG. 7, the synchronizing circuit compares the synchronizing signal extracted from the video signal by the synchronizing separation circuit 60 with the oscillating signal of the oscillating circuit 50 by a comparator 51, and compares the comparison result. The integration is performed by the integration circuit 52 and the integration circuit 5
The configuration is such that the oscillation circuit 50 is controlled based on the integration result in Step 2. Therefore, after the frequency of the synchronization signal is switched or the phase of the synchronization signal is changed, the synchronization circuit operates until the oscillation frequency and the oscillation timing of the oscillation circuit 50 match the frequency and the phase of the synchronization signal. , At least a time determined by the time constant of the integrating circuit 52 (hereinafter, referred to as a following time) is required. For this reason, in the above-described multi-scan display device, the display screen is out of synchronization during the follow-up time of the synchronization circuit, and the image is disturbed.

As means for preventing the display screen from being out of synchronization and disturbing the image, the means described in JP-A-4-30782 and the means described in JP-A-2-272977 have been proposed. .

Japanese Unexamined Patent Publication No. Hei 4-30782 discloses a non-standard synchronization signal detecting circuit for detecting whether or not a horizontal synchronization signal of an input video signal is non-standard. In accordance with the detection result of the above, the integration circuit for determining the follow-up time of the horizontal synchronization circuit is switched. Here, the non-standard synchronizing signal means a synchronizing signal in special reproduction such as pause of a video tape recorder or double speed reproduction. By doing so, when the horizontal synchronization signal of the input video signal is non-standard, the tracking time of the horizontal synchronization circuit is shortened, and the disturbance of the image is reduced.

[0006] Further, according to Japanese Unexamined Patent Application Publication No. 2-272977, when an input video signal is asynchronous and contains a lot of noise, it is generated in synchronization with a horizontal and vertical synchronization signal extracted from a regular image signal. Instead of the horizontal and vertical drive signals, only the rasters based on the reference horizontal and vertical drive signals are displayed. Here, the case where the input video signal is asynchronous and contains a lot of noise means that the input video signal has the synchronization pull-in range of the synchronization circuit (the oscillation frequency and the oscillation timing of the oscillation circuit are determined by the synchronization signal of the input video signal). Out of a range that can be matched to the frequency and phase of

[0007]

However, the means described in Japanese Patent Application Laid-Open No. Hei 4-30782 is to prepare two integrator circuits suitable for the standard signal and the non-standard signal in advance, and to input the video signal to the standard signal. When the signal is switched to a non-standard signal, the integration circuit is switched to shorten the tracking time of the horizontal synchronization circuit. Therefore, for example, a standard signal and a non-standard signal are specified in advance, such as a case where the standard signal is an NTSC video signal and the non-standard signal is a video signal for special reproduction such as pause of a video tape recorder or double-speed reproduction. Although it is effective for a television receiver, it is applicable to a display device that displays an image based on a plurality of video signals having different horizontal synchronization signal frequencies and phases, such as a multi-scan display device. There is a problem that can not be.

In the means described in Japanese Patent Laid-Open No. 2-272977, the horizontal and vertical drive signals generated in synchronization with the horizontal and vertical synchronizing signals extracted from the normal image signal are replaced with the horizontal and vertical reference signals. When switching to the vertical drive signal, the former horizontal and vertical drive signal,
The latter horizontal and vertical drive signals have different frequencies and phases from each other. For this reason, there is a problem that the horizontal and vertical drive circuits, which are the input destinations of the horizontal and vertical drive circuits, cannot immediately respond to the switching of the drive signal, and the image is momentarily disturbed. In addition, Japanese Patent Application Laid-Open
The means described in Japanese Patent No. 272977 is for displaying a raster when the input video signal is out of the preset synchronization pull-in range of the synchronization circuit. When the frequency of the horizontal synchronizing signal of the video signal is switched, or when the phase of the horizontal synchronizing signal changes, the display screen is out of synchronization during the tracking time of the synchronizing circuit, and the image is disturbed. There is a problem.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a display device capable of preventing an image from being disturbed during a follow-up time of a synchronous circuit.

[0010]

In order to solve the above-mentioned problems, the present invention provides a synchronizing signal separating means for extracting a synchronizing signal from an input video signal, an oscillating means for outputting an oscillating signal, and the oscillating means. And a synchronizing means for controlling the oscillating means so that the frequency and phase of the oscillating signal output from the oscillating signal coincide with the frequency and phase of the synchronizing signal extracted by the synchronizing separation means. A display device that scans a screen based on the oscillating signal and displays an image specified by the video signal on the screen, wherein the frequency and / or phase of the synchronization signal extracted by the synchronization signal separating unit is Detecting means for detecting a mismatch with the frequency and / or phase of the oscillation signal output from the oscillating means; and detecting the mismatch on the screen while the detecting means detects the mismatch. Characterized in that it comprises a stop means for stopping the view, the.

Here, the detecting means comprises first waveform shaping means for shaping the synchronization signal extracted by the synchronizing signal separating means into a predetermined waveform, and converting the oscillation signal output from the oscillation means to the predetermined waveform. A second waveform shaping means for shaping the waveform into a waveform, an output signal waveform of the first waveform shaping means, and an output signal waveform of the second waveform shaping means are compared to detect a mismatch between the two. A comparison unit, and a signal output unit that outputs a stop signal for a predetermined time every time the mismatching part is detected by the comparison unit, wherein the stop unit outputs a stop signal from the signal output unit. It is preferable to shut off the video signal supplied to the screen during the operation.

[0012] Further, the predetermined period of time is determined after the frequency and / or phase of the synchronization signal of the input video signal changes.
The frequency and / or phase of the oscillation signal output from the oscillation means may be set to be longer than the time required by the synchronization means until the frequency and / or phase of the oscillation signal coincides with the frequency and / or phase of the synchronization signal. preferable.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram of a multi-scan display device according to an embodiment of the present invention, FIG. 2 is a schematic block diagram of a detection circuit shown in FIG. 1, and FIG. 3 is an input of a waveform shaping circuit shown in FIG. FIG. 3 is a diagram for explaining a waveform and an output waveform.

As shown in FIG. 1, the multi-scan display device of the present embodiment comprises a CRT 1, a deflection coil 2 mounted on the neck of the CRT 1, a high voltage circuit 3 for supplying a high voltage to the CRT 1, and a deflection coil 2. A horizontal output circuit 4 for supplying a current for horizontal scanning to the deflection coil 2, a vertical output circuit 5 for supplying a current for vertical scanning to the deflection coil 2, a horizontal synchronization signal separation circuit 6 for extracting a horizontal synchronization signal from a video signal, A vertical synchronizing signal separating circuit 7 for extracting a vertical synchronizing signal from a video signal, and a vertical oscillation circuit 8 for outputting a pulse signal for driving the vertical output circuit 5 based on the vertical synchronizing signal extracted by the vertical synchronizing signal separating circuit 7 A horizontal oscillation circuit 9 for outputting a pulse signal for driving the horizontal output circuit 4, a horizontal synchronization signal extracted by the horizontal synchronization signal separation circuit 6, and a pulse signal of the horizontal oscillation circuit 9. The comparison result is integrated by the integrating circuit 12 and compared in the comparator 11 the door, a synchronization circuit 10 for controlling the horizontal oscillation circuit 9 based on the results obtained, the detection circuit 13
, A blanking circuit 19, and amplifying the video signal to
And a video signal amplifying circuit 20 for supplying to T1.

Here, the CRT 1, the deflection coil 2, the high voltage circuit 3, the horizontal output circuit 4, the vertical output circuit 5, the horizontal synchronization signal separation circuit 6, the vertical synchronization signal separation circuit 7, the vertical oscillation circuit 8, the horizontal oscillation circuit 9, The synchronization circuit 10 and the video signal amplification circuit 20 are basically the same as those used in the conventional multi-scan display device. For this reason, in this embodiment, these detailed descriptions are omitted,
Only the detection circuit 13 and the blanking circuit 14, which are characteristic parts of the present embodiment, will be described.

As shown in FIG. 2, the detection circuit 13 includes waveform shaping circuits 14 and 15, a matching circuit 16 and an integrating circuit 17
And a blank signal generation circuit 18.

As shown in FIG. 3A, the waveform shaping circuit 14 generates a pulse signal having a predetermined pulse width triggered by the rise of the horizontal synchronizing signal extracted from the video signal by the horizontal synchronizing signal separating circuit 6. . Although the pulse width of the horizontal synchronizing signal varies depending on the type of the video signal (mainly, the horizontal synchronizing frequency), according to the waveform shaping circuit 14, the pulse signal having a constant pulse width regardless of the pulse width of the horizontal synchronizing signal. Is generated.

The waveform shaping circuit 15 generates a pulse signal having a predetermined pulse width triggered by a rise of the pulse signal output from the horizontal oscillation circuit 9, as shown in FIG. Here, the waveform shaping circuit 15 needs to be set so that the pulse width of the pulse signal to be generated is substantially the same as the pulse width of the pulse signal generated by the waveform shaping circuit 14.
Also, if there is no change in the frequency or phase of the horizontal sync signal,
The rise of the generated pulse signal is determined by the waveform shaping circuit 14.
To match the rising edge of the pulse signal generated by
It is necessary to correct the timing. Note that the waveform shaping circuits 14 and 15 can be configured using, for example, a monostable multivibrator.

The matching circuit 16 compares the pulse signal generated by the waveform shaping circuit 14 with the pulse signal generated by the waveform shaping circuit 15 and outputs a signal according to the comparison result. In the present embodiment, a setting is made such that a high-level signal is output when both match, and a low-level signal is output when they do not match. The matching circuit 16 can be configured using, for example, a four-circuit two-input exclusive OR (model name: 74HC86).

The blank signal generation circuit 18 outputs a blank signal for a predetermined time, triggered by the fall of the input signal. In the present embodiment, the output of the blank signal generation circuit 18 is normally set to a high level, and a low-level blank signal is set to be output. Note that the output time of the blank signal is preferably set to be longer than the tracking time of the synchronous circuit 10, that is, at least the time determined by the time constant of the integrating circuit 12. When the frequency change of the horizontal synchronizing signal increases, the follow-up time of the synchronizing circuit 10 also tends to increase, but it is sufficient to set the horizontal synchronizing signal to about 2 seconds. The blank signal generation circuit 18 is, for example, a retriggerable one-shot type that triggers on the falling edge of the input signal.
It can be configured using a multivibrator.

The integrating circuit 17 is for preventing the blank signal generating circuit 18 from malfunctioning due to the noise when the output of the matching circuit 16 contains pulse noise. The integrating circuit 17 is a matching circuit 1
It is necessary to set the time constant so as not to greatly affect the waveform of the signal output from the signal generator 6.

The blanking circuit 14 cuts off the video signal while the blank signal is being output from the blank signal generation circuit 18, and cuts off the video signal.
Cut off the supply to 9.

Next, the operation of this embodiment will be described.

First, the operation when the frequency and phase of the horizontal synchronizing signal of the input video signal are stable will be described with reference to FIG.

FIG. 4 is a diagram for explaining signal waveforms at points a to f shown in FIG. 2 when the frequency and phase of the horizontal synchronizing signal of the input video signal are stable.

When the frequency and phase of the horizontal synchronizing signal of the input video signal are stable, the horizontal synchronizing signal (signal at point a in FIG. 2) input to the synchronizing circuit 10 and the horizontal oscillator 9 The output pulse signal (the signal at point b in FIG. 2) is in a state where the frequency and the phase match. Therefore, the waveform of the signal (signal at point c in FIG. 2) output from the waveform shaping circuit 14 and the waveform of the signal (signal at point d in FIG. 2) output from the waveform shaping circuit 15 are mutually different. Matches. The matching circuit 16 outputs a high-level signal when the pulse signal generated by the waveform shaping circuit 14 and the pulse signal generated by the waveform shaping circuit 15 match, and outputs a low-level signal when they do not match. Is output, the signal at point e in FIG. 2 is always at a high level. In this case, since the blank signal generation circuit 18 does not output a blank signal, the signal at point f in FIG. 2 is always at a high level. Therefore, the video signal is supplied to the video signal amplification circuit 20 without being interrupted by the blanking circuit 19. Therefore, an image specified by the input video signal is displayed on the CRT 1.

Next, the frequency of the horizontal synchronizing signal of the input video signal changes, and the synchronizing circuit performs the following operation (the frequency and phase of the output pulse signal of the horizontal oscillation circuit are matched with the frequency and phase of the horizontal synchronizing signal). The operation when (operation) is performed will be described with reference to FIG.

FIG. 5 is a diagram for explaining signal waveforms at points a to f shown in FIG. 2 when the frequency of the horizontal synchronizing signal of the input video signal changes and the synchronizing circuit performs the following operation. FIG.

When the frequency of the horizontal synchronizing signal changes due to switching of the input video signal, the horizontal synchronizing signal (signal at point a in FIG. 2) input to the synchronizing circuit 10 within the following time of the synchronizing circuit 10 And the pulse signal (the signal at point b in FIG. 2) output from the horizontal oscillation circuit 9 is in a state where the frequencies do not match. Therefore, the waveform of the signal output from the waveform shaping circuit 14 (the signal at the point c in FIG. 2) does not match the waveform of the signal output from the waveform shaping circuit 15 (the signal at the point d in FIG. 2). Parts occur. Match circuit 16
Outputs a high-level signal when the pulse signal generated by the waveform shaping circuit 14 matches the pulse signal generated by the waveform shaping circuit 15, and outputs a low-level signal when the pulse signal does not match. Fig. 2
The signal at the point e becomes a low level at a mismatch portion between the signal waveform at the point c and the signal waveform at the point d. In this case, the blank signal generation circuit 18 is triggered by the fall of the input signal (the signal at point e in FIG. 2) and outputs a low-level blank signal for a predetermined time. During the blank signal output, every time a low-level pulse is input, the trigger is retriggered at the falling edge of the pulse, and the blank signal output is output after a predetermined time has elapsed from the falling edge of the last input low-level pulse. Stops and outputs a high-level signal. Therefore, the signal at point f in FIG. 2 is at a low level during the tracking time of the synchronous circuit 10. Thus, during the follow-up time of the synchronization circuit 10, the video signal is cut off by the blanking circuit 19 and is not supplied to the video signal amplification circuit 20. Therefore, nothing is displayed on the CRT 1 during the tracking time of the synchronous circuit 10.

In FIG. 5, the operation when the frequency of the horizontal synchronizing signal of the input video signal changes and the synchronizing circuit performs the following operation has been described. In the same manner, when the phase of the signal changes and the synchronous circuit is performing the following operation, the synchronous circuit 10
During the following time, image display on the CRT 1 is stopped.

Next, the operation when the horizontal synchronizing signal of the video signal is interrupted (so-called free-run) will be described with reference to FIG.

FIG. 6 is a diagram for explaining signal waveforms at points a to f shown in FIG. 2 when the horizontal synchronizing signal of the video signal is interrupted.

When the horizontal synchronizing signal of the video signal is interrupted, the signal waveform at point a shown in FIG.
The frequency of the signal input to the synchronization circuit 10 and the frequency of the pulse signal (signal at point b in FIG. 2) output from the horizontal oscillation circuit 9 do not match. Therefore, the waveform of the signal output from the waveform shaping circuit 14 (the signal at point c in FIG. 2) and the signal output from the waveform shaping circuit 15 (d in FIG. 2)
And the waveform at the point). The matching circuit 16 outputs a high-level signal when the pulse signal generated by the waveform shaping circuit 14 and the pulse signal generated by the waveform shaping circuit 15 match, and outputs a low-level signal when they do not match. Is output, the signal at the point e in FIG. 2 is at a low level at the mismatch between the signal waveform at the point c and the signal waveform at the point d. In this case, the blank signal generation circuit 18 outputs the input signal (e in FIG. 2).
Triggered by the falling edge of the signal at the point, a low-level blank signal is output for a predetermined time. Then, every time a low-level pulse is input during the blank signal output, the trigger is retriggered at the falling edge of the pulse. Therefore, FIG.
Since the signal at the point f becomes low level, the video signal is cut off by the blanking circuit 19 and is not supplied to the video signal amplifier circuit 20. Therefore, nothing is displayed on CRT1.

In this embodiment, the detection circuit 13 detects a mismatch between the frequency and phase of the horizontal synchronization signal input to the synchronization circuit 10 and the frequency and phase of the pulse signal output from the horizontal oscillation circuit 9. . While the detection circuit 13 detects the mismatch, the video signal is cut off by the blanking circuit 19 and the image display on the CRT 1 is stopped. Therefore, according to the present embodiment, when the frequency of the horizontal synchronization signal of the input video signal is switched or when the phase of the horizontal synchronization signal changes, a disturbed image is prevented from being displayed on the CRT 1. can do. Further, when the input video signal is interrupted, or when the input video signal is in the synchronization pull-in range of the synchronization circuit 10 (the oscillation frequency and the oscillation timing of the horizontal oscillation circuit 9 are matched with the frequency and phase of the horizontal synchronization signal). Can be)
Similarly, even when it is outside, it is possible to prevent a disturbed image from being displayed on the CRT 1.

In this embodiment, the detection circuit 13 includes a waveform shaping circuit 14 for shaping the waveform of the horizontal synchronizing signal.
A waveform shaping circuit 15 for shaping the output pulse signal of the horizontal oscillation circuit 9, and a matching circuit for comparing the output signal waveform of the waveform shaping circuit 14 and the output signal waveform of the waveform shaping circuit 15 to detect a mismatch between the two. 16 and a blank signal generation circuit 18 that outputs a blank signal for a predetermined time every time a mismatch portion is detected by the matching circuit 16. Each of these components can be configured using a general circuit without using a specially complicated circuit. Therefore, according to the present embodiment, the detection circuit can be manufactured relatively inexpensively. Further, according to the present embodiment, by setting the output signal waveform of the waveform shaping circuit 15 to coincide with the output signal waveform of the waveform shaping circuit 14 when there is no change in the frequency or phase of the horizontal synchronization signal, When the frequency or phase of the horizontal synchronization signal of the input video signal changes, it is possible to more accurately prevent a disturbed image from being displayed on the CRT 1.

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the invention. For example, in the above-described embodiment, an example has been described in which, when the frequency or phase of the horizontal synchronization signal of the video signal is switched, the video signal is cut off to prevent a disturbed image from being displayed on the CRT 1. However, the present invention is not limited to this. Even when the frequency and phase of the vertical synchronizing signal of the video signal are switched, the video signal may be cut off to prevent a disturbed image from being displayed on the CRT 1 as in the case of the horizontal synchronizing signal. . This is provided with a detection circuit for detecting a mismatch between the frequency and the phase of the vertical synchronization signal input to the vertical oscillation circuit 8 and the frequency and the phase of the pulse signal output from the vertical oscillation circuit 8. This can be realized by cutting off the video signal by the blanking circuit 19 during the detection.

In the above embodiment, the display device using the CRT has been described, but the present invention can be similarly applied to a display device using a liquid crystal panel, for example. Further, the present invention is not limited to a multi-scan display device, but can be applied to, for example, a television receiver.

[0039]

As described above, according to the present invention,
When the frequency or phase of the synchronization signal of the input video signal changes, when the input video signal is interrupted, or when the input video signal is out of the synchronization pull-in range of the synchronization means, disturbance occurs. The displayed image can be prevented from being displayed.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a multi-scan display device according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram of a detection circuit shown in FIG.

FIG. 3 is a diagram for explaining an input waveform and an output waveform of the waveform shaping circuit shown in FIG. 2;

4 shows points a to f shown in FIG. 2 when the frequency and phase of the horizontal synchronization signal of the input video signal are stable.
FIG. 4 is a diagram for explaining a signal waveform at a point.

FIG. 5 is a diagram for explaining signal waveforms at points a to f shown in FIG. 2 when the frequency of a horizontal synchronization signal of an input video signal changes and the synchronization circuit performs a following operation; It is.

6 is a diagram for explaining signal waveforms at points a to f shown in FIG. 2 when the horizontal synchronizing signal of the video signal is interrupted.

FIG. 7 is a schematic block diagram of a synchronization circuit used in a conventional multi-scan display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CRT 2 Deflection coil 3 High voltage circuit 4 Horizontal output circuit 5 Vertical output circuit 6 Horizontal synchronization signal separation circuit 7 Vertical synchronization signal separation circuit 8 Vertical oscillation circuit 9 Horizontal oscillation circuit 10 Synchronization circuit 11 Comparator 12, 17 Integration circuit 13 Detection circuit 14, 15 Waveform shaping circuit 16 Matching circuit 18 Blank signal generating circuit 19 Blanking circuit 20 Video signal amplifying circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication // H04N 3/27 H04N 3/27

Claims (3)

[Claims] 1. A synchronizing signal separating means for extracting a synchronizing signal from an input video signal, an oscillating means for outputting an oscillating signal, and a frequency and a phase of the oscillating signal output from the oscillating means, A synchronizing means for controlling the oscillating means so as to match the frequency and phase of the synchronizing signal extracted in the above, and scans a screen based on the oscillating signal output from the oscillating means, A display device for displaying an image specified by the video signal, wherein a frequency and / or a phase of the synchronization signal extracted by the synchronization signal separation unit and a frequency and / or a frequency of an oscillation signal output from the oscillation unit Or detecting means for detecting a mismatch with the phase, and stopping means for stopping display of an image on a screen while the mismatch is detected by the detecting means. Display device that. 2. The apparatus according to claim 1, wherein said detecting means comprises: first waveform shaping means for shaping the synchronous signal extracted by said synchronous signal separating means into a predetermined waveform; and an oscillating signal output from said oscillating means. A second waveform shaping unit for shaping the waveform into the predetermined waveform, and comparing an output signal waveform of the first waveform shaping unit with an output signal waveform of the second waveform shaping unit, and disagreement between the two. Comparing means for detecting a portion, and signal output means for outputting a stop signal for a predetermined time every time the mismatching part is detected by the comparing means, wherein the stop means outputs a stop signal from the signal output means. A display device for shutting off a video signal supplied to a screen while the image is being output. 3. The method according to claim 2, wherein the frequency and / or phase of the synchronization signal of the input video signal is changed, and then the frequency and / or phase of the oscillation signal output from the oscillating means is changed. Frequency and / or
Alternatively, the predetermined time is set so as to be longer than the time required by the synchronization means until the phase coincides with the phase.