JPS6116686A - Correction system for time axis variation of reproduced video signal - Google Patents

Abstract

PURPOSE:To prevent the crooking of a longitudinal line and improve the quality on a screen in a video signal recording and reproducing device like a rewritable optical video file device by using a signal showing the phase of the trailing edge of the horizontal synchronizing signal of a reproduced video signal as a time axis phase signal. CONSTITUTION:A time axis variation corrrection system 20 is constituted by using a variable delay element using a CCD22. An output video signal 21 is inputted to a synchronous separating circuit 23 and a composite synchronizing signal 24 is applied to a sample pulse generating circuit 25 to generate sample pulses by using trailing edge information on the horizontal synchronizing signal, so that the pulses are inputted to a phase comparing means 27 through a gate circuit 26. The output of the phase comparing means 27 is impressed as the control voltage of a voltage-controlled oscillator 31 through a processing circuit 30 to control the frequency of the oscillator. The output of the voltage-controlled oscillator 31 is impressed to the CCD22, whose delay time is controlled. Thus, the trailing edge information on the horizontal synchronizing signal is used to detect time axis variation of the output video signal, and the time axis variation of the output video signal 21 is suppressed with detection information.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a time axis fluctuation correction method for a reproduced video signal in a video signal recording and reproducing apparatus such as a rewritable optical video file apparatus.

[Background of the Invention] The prior art will be explained by taking a rewritable optical video file device as an example.

In recent years, a Te compound film has been applied to the groove side surface of a disc-shaped acrylic substrate provided with a guide groove, and a laser beam is irradiated thereon to locally reduce the reflectance of I on the guide groove. A rewritable video file device has become widely known, which records video information by changing the reflectance and reproduces the recorded information by detecting the change in reflectance using a constant weak laser beam.

In such devices, in order to avoid the effects of nonlinear characteristics (that is, the relationship between the intensity of the laser beam and the amount of change in reflectance is not linear) in the recording and reproducing process, the luminance image information is frequency modulated ( FM) video carrier wave (
It is recorded in the form of FM signal). In other words, video information is expressed by the rising and falling phases of this carrier signal, that is, the change in the zero-crossing phase when it crosses the zero position.5
I have to.

Furthermore, when demodulating a video carrier signal that has been FM modulated in this way, the noise after demodulation will have many noise components in the high frequency range due to the principle of the demodulation operation. Noise can be suppressed by emphasizing the high-frequency components of the signal (pre-emphasis) and then restoring them to their original state using a high-frequency suppression (de-emphasis) circuit that has the opposite characteristics of the pre-emphasis circuit after demodulation. It is being done.

In addition, due to eccentricity of the mounting hole of the aforementioned disc-shaped acrylic base, distortion of the guide groove, etc., time axis fluctuations occur in the reproduced signal from the rotatably driven base, so to compensate for this, time axis fluctuation correction is performed. It is also well known to provide a system.

Now, various things have been explained above, but as mentioned above, video information is recorded in FM modulation format, furthermore, pre-emphasis and de-emphasis techniques are adopted to improve the S/N ratio, and the time axis of the reproduced video signal is In a nine-video signal recording and reproducing apparatus equipped with a variation correction method, vertical line curvature sometimes occurs on the reproduced screen.

Vertical line bending means, for example, that an object image 1a that is originally a straight line (such as a chimney) as seen in Fig. 2(a) has a ``<'' in the middle as shown in 1b shown in Fig. 2Cb'') This refers to the 5 phenomenon of bending in the shape of a letter.

It goes without saying that a screen that causes vertical line curvature is a screen of poor quality.

[Purpose of the invention]

The present invention has been made in order to eliminate the drawbacks of the prior art as described above. Therefore, the purpose of the present invention is to expand the purpose of the present invention, to elucidate the cause of the vertical line bending phenomenon on the playback screen, and to prevent the occurrence of such a phenomenon. (As a result, it was found that the cause of this problem existed in the conventional time axis fluctuation correction method related to pre-emphasis and pre-emphasis techniques.) The objective is to provide a time axis variation correction method).

[Summary of the invention]

The conventional time axis fluctuation correction method for reproduced video signals extracts the front phase of the horizontal synchronization signal in the reproduced video signal as a time axis phase signal, and compares this with a reference phase signal to find the amount of time axis fluctuation. There is.

According to the inventor's study, the above-mentioned bending phenomenon occurs because the waveform distortion of the leading edge of the horizontal synchronizing signal due to emphasis/de-emphasis, etc. changes depending on the waveform of the video signal section preceding the signal. ,found. below,
Let me explain this in a little more detail.

FIG. 3 (ao) is a waveform explanatory diagram of an example of a video signal mainly consisting of a horizontal synchronization signal. Since this waveform is already a well-known waveform, there is no need to explain it again. In addition,
F indicates the leading edge (or also referred to as the leading edge) of the horizontal synchronizing signal, and the phase at this point has conventionally been used as the time axis phase signal.

When the waveform shown in FIG. 3(ao) is emphasized, it becomes a waveform as shown in FIG. 3(ax)K.

FIG. 3 (bo) is a waveform explanatory diagram of another example of a video signal mainly consisting of a horizontal synchronizing signal. (510) and (bo)
When compared, it will be seen that in (bo), the level of the video signal portion is lower overall.

If we emphasize the waveform shown in Figure 3 (bo), we get
The waveform becomes as shown in FIG. 3 (bl). (al) and (
Comparing bl), we see that the influence of K on the waveform difference (in this case, mainly the level difference) in the video signal section preceding the horizontal synchronization signal appears, and the leading edge F at (al)K becomes ( It will be recognized that the length ΔF extends toward the black level side from that F in bl). Therefore, the waveform shown in (al) is smaller than the waveform shown in (bl).
This means that clip distortion is more likely to occur.

Note that clipping distortion occurs when the FM-modulated video signal waveform after pre-emphasis is passed through a clip circuit to limit the amplitude in order to limit the frequency deviation width of the video signal depending on the transmission band. This refers to the signal distortion that occurs.

For the above reasons, the leading edge of the horizontal synchronization signal after de-emphasis for the video signal of FIG. 3(aO) is distorted more than that for the video signal of FIG. 3(bo). According to one actual measurement example, this distortion difference is approximately 10% when expressed as a time axis change.
Although it is generally a small amount of 0 ns or less, it becomes a problem when used for detecting the amount of variation in a time axis variation correction method.

As explained above, from the study results by the present inventors, it is possible to first reduce the amount of emphasis/de-emphasis as a countermeasure against the warping phenomenon, but this measure does not improve the S/N ratio. It cannot be adopted because it will be disadvantageous.

Second, it is conceivable to use the color burst signal included in the composite video signal instead of the horizontal synchronization signal to detect time axis fluctuations5, but this not only complicates the detection process but also The problem is that it cannot be used in the case of black and white signals without a signal.

Therefore, in the present invention, the horizontal synchronization signal is used at five points, which is the same as before, but instead of using the leading edge of the horizontal synchronization signal as in the past, the rear synchronization signal is used as shown in FIG. We decided to use IB.

Unlike the leading edge F, the trailing edge #B is preceded by a horizontal synchronizing signal and not a video signal portion, so it is hardly affected by that, and the extension of the trailing edge B after emphasis is (
It is understood that this signal is suitable for use as a time axis phase signal for two reasons: as shown in al), it is above (that is, on the white level side) and is therefore less susceptible to clipping distortion. There will be.

[Embodiments of the invention]

The present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, 1 is a disk, 2 is a motor, 3 is a frequency generator, 4 is a frequency discriminator, 5 is a processing circuit, 6 is an addition stage, 7 is a driver stage, 8 is a mark detector, 9 is a sample pulse generator 10 is a phase comparison stage, 11 is a processing circuit, 1
2 is a reference signal generator, 13 is a countdown circuit, 14
15 is a frame frequency reference signal, 15 is a trapezoidal wave generation circuit,
16 is an information detection optical head, 17 is a detected video FM signal,
18 is an FM demodulation system, 19 is a reproduced video signal, 20 is a time axis fluctuation correction system, 21 is an output video signal, 22 is a COD variable delay element, 23 is a synchronization separation circuit, 24 is a composite synchronization signal, 2
5 is a sample pulse generation circuit, 26 is a gate circuit, 27
is a phase comparison stage, 28 is a reference signal, 29 is a trapezoidal wave generation circuit, 30 is a processing circuit, 31 is a voltage controlled oscillator (VCO),
32 is a driver stage, 33 is a vertical synchronization detection stage, and 34 is a gate pulse generation circuit.

In FIG. 1, what is directly related to the present invention is the time axis variation system 200 circuit configuration and circuit operation shown surrounded by a broken line, but other parts are also necessary for a better understanding of the present invention. Therefore, the circuit operation of the other parts will be explained below.

First, the disk 1 is stably rotated by the motor 2 at the frame' frequency. The rotational speed of the motor 2 is detected by a frequency generator 3 that is linked to the motor, and a frequency discriminator 4 obtains a valve and separate output.
The motor 2 passes through the processing circuit 5, addition stage 6, and driver stage 7.
is frequency controlled.

In addition, a mark previously provided on the disk at 10 rotational phases of the disk is detected by a mark detector 8, inputted to a sample pulse generation stage 9, a sample pulse is obtained, and the sample pulse is compared at a phase comparison stage 10 including a sample hoard stage. Then, a comparison output is obtained, which is passed through a processing circuit 11, an addition stage 6, and a driver stage 7 to control the phase of the motor 2.

In addition, the output of the reference signal generator 12 is output to the countdown circuit 1.
3 to obtain a frame frequency reference signal 14, which is input to a trapezoidal wave generating circuit 15 to obtain a trapezoidal wave to be applied to the phase comparison stage 10.

FIG. 4 is an explanatory diagram showing signal waveforms at the input/output section of the phase comparator stage 10 in FIG. 1.

In the figure, a trapezoidal wave a is a signal waveform that is repeatedly output from the trapezoidal wave generating circuit 15 at a constant period To. on the other hand,
The timing of the sample pulse t generated from the sample pulse generation stage 9 is initially t1 (reference timing),
In the next cycle, if t2Vc deviates, phase comparison stage 1o
Then, an output amount ΔV corresponding to the deviation is generated, and this is used to control the phase of the disk 10.

As described above, the disk 1 is rotated stably by using both frequency control and phase control.

Reference numeral 16 denotes an optical head for information detection, which detects a video FM signal recorded on the disk using a well-known focus and tracking servo system (not shown). Note that the recording system is not directly related to the present invention, so a description thereof is omitted.

The detected video FM signal 17 which is the output of the optical head 16 is
The signal is inputted to a demodulation system 18 to obtain a reproduced video signal 19, and inputted to a time axis variation correction system 2o according to the present invention to obtain an output video signal 21 as its output.

Next, the time axis variation correction system 2o according to the present invention will be explained in detail.

The time axis variation correction system 2o is configured using a variable transparent element formed by a CCD 22.゛・The output video signal 21 is manually inputted to the synchronization separation circuit 23, and its output is the secret synchronization signal 24.
A sample pulse generation circuit 25 (in addition, a sample pulse is generated using the trailing edge information of the horizontal synchronization signal, and the sample pulse is passed through a gate circuit 26 to a phase comparison stage 27 including a sample hold stage.
Enter.

The other input of the phase comparator stage 27 is a horizontal synchronization frequency reference signal 2, which is one of the outputs of the countdown circuit 130.
8 is manually input to the trapezoidal wave generation circuit 29, and the trapezoidal wave obtained as the output is obtained. The signal waveform of the input/output section of the phase comparison stage 270 is qualitatively the same as that described above for the phase comparison stage 10, so please refer to FIG. 4. .

The output of the phase comparison stage 270 is applied as a control voltage to the voltage controlled oscillator 310 via the processing circuit 30j to control the frequency of the oscillator. The output of the voltage controlled oscillator 31 is applied to the CC'D 22 via a driver stage 32 to control its conduction time.

Note that a vertical synchronization signal is detected from the composite synchronization signal 24 by a vertical synchronization detection stage 33, and then a gate pulse generation circuit 3
4, a gate pulse used for the gate circuit 26 is obtained.

This vertical synchronizing signal is used to prevent the gate pulse generation circuit 34 from generating a gate pulse during the vertical retrace period. In other words, during the vertical retrace period, the gate circuit 26
Since no gate pulse is available from circuit 34, it remains closed and therefore no sample pulse is sent to phase comparator stage 27 (the reason for this will be discussed shortly).

With the above configuration, the trailing edge information of the horizontal synchronization signal is used to detect time axis fluctuations in the output video signal, and the detection information is used to control the conduction time of the CCD 22 to control the output video signal 21.
This suppresses time axis fluctuations.

In this case, since the trailing edge of the horizontal synchronizing signal is used, as described above, it is less susceptible to distortion caused by the emphasis/de-emphasis process, etc., and the phenomenon of curving of the reproduced screen is prevented.

Note that when the gate circuit 2°6 uses the trailing edge information of the horizontal synchronization signal as described above, the vertical synchronization signal and the partial power of the equalization pulse in the composite video signal are likely to generate false signals. If a valid sample pulse is not obtained, and if this is used, a large phase error signal will be generated from the phase comparison stage 27, and the reproduced video signal will be disturbed by the transient response.
This is provided in order to prevent fins, that is, to close the circuit during the vertical retrace period and prevent the sample pulse from the circuit 25 from passing through, as mentioned above.

FIG. 5 shows a first specific example of a sample pulse generation circuit 25 that generates sample pulses using trailing edge information of a horizontal synchronization signal, and FIGS. 6(a) and (b).

(c) shows the waveforms at points a, b, and c in Fig. 5.

In Figure 11g5, 251 and 252 are monostable multivibrators, respectively.

The circuit operation will be explained with reference to FIGS. 5 and 6.

The horizontal synchronization signal as the output 24 of the synchronization separation circuit 23 is a negative polarity pulse as shown in FIG. 6(,a).

251 and 252 in FIG. 5 are respectively the rising R of the input signal.
It is a monostable multivibrator triggered by the fifth
As can be seen from Fig. 6, monostable multivibrator 2
Trailing edge information R of the desired horizontal synchronization signal (3rd
(corresponding to B in the figure), a sample pulse (C) is obtained.

The monostable multivibrator 251 is provided to suppress the generation of undesirable spurious sample pulses. In other words, even if pulse noises such as those shown at 241 and 242 in FIG. 6 are mixed in due to dropout or the like, the monostable multivibrator 251 does not respond to these noises while its Q output is at a high level (i.e., Since the monostable multivibrator 251 is non-retriggerable, it suppresses the influence of noise.

FIG. 7 shows a specific example of #I2 of the sample pulse generation circuit 25, and FIGS. ), (4), (c).

The waveforms of points (d) and (e) are shown.

Note that points 251, 252, and c in FIG. 7 are the same as those in FIG. 5. That twist is that 253 is a clip circuit, 254 is an integration circuit, 255 is a slice circuit, 2
56 is an AND circuit.

The circuit operation will be explained with reference to FIGS. 7 and 8.

The clip circuit 253 clips the input signal shown in the fss diagram (A) at the level shown by IC81 in the figure, removes the portion below level S1, and obtains the output shown in FIG. 8 (E=). .

In FIG. 8(a), 241, 242, and 243 are mixed pulse noises, and by clipping as described above, noises such as 243 are removed. The output of the integrating circuit 254 is as shown in FIG. 8(c). The slicing circuit 255 slices the signal shown in FIG. 8(c) at level S2, sets the portion below level 82 to high level, and sets the other part to low level, and converts the signal shown in FIG. 8(d) into slices.
It outputs a signal as shown in K.

Furthermore, the AND circuit 256 is a circuit that performs the AND operation of FIG. 8(b) and (d) and outputs the result, and the output is as shown in FIG. 8(e).

With the above configuration, the rising edge of the output (E) is extremely less likely to be affected by pulse noise, and the reliability of operation is improved accordingly.

The monostable multivibrator 251 mentioned above is further
This is used to reduce the frequency of this occurrence.

Another embodiment of the time axis fluctuation correction system according to the present invention is shown in FIG. In this figure, parts given the same numbers as in FIG. 1 have the same functions as in FIG. 1, and therefore their explanation will be omitted.

In FIG. 9, in addition to the sample pulse generation circuit 25 that generates sample pulses using the trailing edge information of the horizontal synchronizing signal as shown, the leading edge of the horizontal synchronizing signal (note that it meets the trailing edge) is used. A sample pulse generation circuit 25a that generates sample pulses and a switching pulse generation circuit 34a for the switch circuit 26a1 are provided.

As explained earlier, in the vertical blanking period of a composite video signal, if the trailing edge of the horizontal synchronizing signal is used to generate a sample pulse, a false signal will be generated. During the retrace period, as before, the leading edge of the horizontal synchronizing signal is used to generate a sample pulse corresponding to the trailing edge, and this is used.

That is, the vertical retrace period is detected by the vertical synchronization detection stage 33,
During this time, a switching pulse is generated from the switching pulse generation circuit 34a to switch the switch circuit 261 to the circuit 25a side, and send the sampling pulse created using the front information to the phase comparison stage 27.

FIG. 10 shows a specific example of the sample pulse generation circuit 25a using the leading edge information in FIG. 9, and its a, i, j,
In FIG. 11, the waveforms of the respective parts indicated by (a), (quantity), (j), and (k) Vc are shown.

As can be seen from these figures, the circuit 2551 has the function of generating a sample pulse shifted to a position corresponding to the trailing edge information using the leading edge information of the horizontal synchronization signal.

251a and 252a in Fig. 10 are respectively 251 in Fig. 5.
252 is a non-retriggerable monostable multivibrator, and 253 is a non-retriggerable monostable multivibrator provided for the above shift.

In FIG. 9, 34a is for generating a switching pulse m from the vertical synchronizing signal.

The waveforms of portions a, c, t, and m shown in FIG. 9 are shown in FIG. 12 (signal waveforms that also match ap'pjpk in FIG. 10). As shown in FIG. 12, the output C of the sample pulse generation circuit 25 using trailing edge information does not become a sample pulse with the correct phase near the vertical synchronization signal.

Therefore, during the period when the switching pulse m is at a high level, the switch circuit 26a is connected to the negative side to obtain an appropriate sample pulse t.

〔Effect of the invention〕

According to the present invention, it is possible to always appropriately detect time axis fluctuations, and there is an advantage that it is possible to provide a time axis fluctuation correction method that does not cause image distortion.

[Brief explanation of the drawing]

FIG. 1 is a professional diagram showing an embodiment of the present invention, FIG. 2(a) is an explanatory diagram of a normal screen, and FIG. 2(b) is an explanatory diagram of a screen with vertical line bending. FIG. 3(aO) is a waveform explanatory diagram of an example of a video signal mainly consisting of a horizontal synchronization signal, FIG. 3(al) is a waveform explanatory diagram of the same waveform after emphasis, and FIG.
Figure (bo) is a waveform explanatory diagram showing another example of a video signal mainly consisting of a horizontal synchronization signal, Figure 3 (bl) is a waveform explanatory diagram of the same waveform after emphasis, and Figure 4 is a phase diagram of the same waveform in Figure 1. An explanatory diagram showing signal waveforms of the input/output section of the comparison stage 10, FIG. 5 is a circuit diagram showing a specific example of the sample pulse generation circuit 25 in FIG. 1, and FIG. 6 shows waveforms of signals at each part in the circuit of FIG. 7 is a circuit diagram showing another specific example of the sample pulse generation circuit 25, FIG. 8 is a waveform diagram of various signals in the circuit of FIG. 7, and FIG. 9 is a time axis fluctuation correction according to the present invention. A block diagram showing another embodiment of the system, FIG. 10 is a sample pulse generation circuit 2 using leading edge information in FIG.
5A is a circuit diagram showing a specific example of tD, FIG. 11 is a waveform diagram of each part signal in FIG. 10, and FIG. 12 is a chart showing the timing of each part signal in the circuit of FIG. 9. Code explanation 1...disc, 2...motor, 3.
... Frequency generator, 4 ... Frequency discriminator, 5 ... Processing circuit, 6 ... Addition stage, 7
・・・・・・Driver 1 stage, 8・・・Mark detector, 9・・・Sample pulse generation stage, 10...
. . . Phase comparison stage, 11 . . . Processing circuit, 12.
...Reference signal generator, 13 ... Countdown circuit, 14 ... Frame frequency reference signal, 15 ... Trapezoidal wave generation circuit, 16 ...・
・Optical head for information detection, 17...Detection video FM
Signal, 18...FM demodulation system, 19...
Reproduction video signal, 20... Time axis fluctuation correction system, 2
1... Output video signal, 22... CCD
Variable delay element, 23... Synchronization separation circuit, 24.
... Composite synchronization signal, 25 ... Sample pulse generation circuit using trailing edge information, 25a ... Sample pulse generation circuit using leading edge information, 26 ...
...Gate circuit, 27... Phase comparison stage, 28.
...Reference signal, 29...Trapezoidal wave generation circuit, 30...Processing circuit, 31...Voltage controlled oscillator (VCO), 32...・Driver stage, 3
3... Vertical synchronization detection stage, 34... Gate pulse generation circuit, 21F (to) (b) gX3 Figure 5 ■ Figure 9 Figure 10 Figure ■

Claims (1)

[Claims] 1) A first means for detecting a time axis phase signal from a reproduced video signal reproduced from a recording medium, a second means for generating a reference phase signal, and a detected time axis phase. It consists of a third means for determining the amount of time axis variation by comparing the signal with the reference phase signal, and a fourth means for controlling the time axis phase of the reproduced video signal so that the amount of variation becomes zero. A time axis variation correction method for a reproduced video signal, characterized in that a signal indicating a phase of a trailing edge of a horizontal synchronization signal in the reproduced video signal is used as the time axis phase signal. 2) The time axis fluctuation correction method according to claim 1, characterized in that the detection of the time axis phase signal by the first means is stopped during a vertical retrace period in the video signal. Time axis variation correction method. 3) In the time axis fluctuation correction method according to claim 2, during the pause period, a signal indicating the phase of the trailing edge of the horizontal synchronization signal is created from a signal indicating the phase of the leading edge. A time axis variation correction method characterized by the following.