JPS6051309B2 - Time axis error correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time axis error correction device, which controls the oscillation output of a voltage-controlled crystal oscillator using a phase error signal obtained from a reproduction synchronization signal to control the rotational phase of a rotational information recording medium. At the same time, by supplying a playback synchronization signal to the jitter servo circuit, it is possible to synchronize with external signals and always perform stable time axis error correction. An object of the present invention is to provide a time axis error correction device that can easily correct the time axis error of a reproduced signal with compatibility even when a video signal of a television system different from the video signal is recorded. .

In a playback device for a disk-shaped rotating information recording medium (hereinafter referred to as a "disc"), the playback signal may have a time difference due to causes such as uneven rotation of the playback device itself, eccentricity of the disk, and press distortion during the disk molding process. An axis error occurs.
This time axis error appears as color unevenness and screen shaking,
Significantly reduces image quality. To this end, the time axis error has conventionally been reduced by forcibly moving the reproducing element in the longitudinal direction of the track using an electro-mechanical converter (actuator). As the above-mentioned conventional time axis error (hereinafter also referred to as "jitter") correction device, heterodyne is performed to electrically correct color unevenness, and the correction signal generated at that time is used as a jitter correction signal and is converted into an electro-mechanical converter. There was something to feed the vessel.

However, in this conventional device, the correction signal (jitter signal) created by the heterodyne to electrically correct color unevenness is not necessarily the optimal signal for driving the electro-mechanical converter. Even if phase compensation is applied to the correction signal, it is often difficult to obtain a sufficiently large degree of jitter improvement. For this reason, in addition to the above-mentioned heterodyne, in order to control jitter using an electro-mechanical converter (jitter servo), there is also a new device that creates and controls a jitter signal suitable for jitter servo using the same method as the heterodyne. Traditionally hot.

On the other hand, as video discs become more widespread in the future, there will be a need to play back video discs by locking them to external signals, such as connection with computers, inset of text on the screen, synchronized operation with television cameras, etc.

In the conventional device described above, it is not possible to lock the playback signal to an external signal as it is, and it is necessary to compare the phases of the playback synchronization signal and the reference signal, respectively, and control the turntable motor using this. No. In order to lock the reproduced signal to an external signal in a time-base error correction device that does not use the heterodyne jitter detection method, a device as shown in the block diagram of FIG. 1 can be considered.

In the figure, the synchronization signal or color burst signal in the reproduced video signal of the disc that has entered input terminal 1 is phase-compared with the reference signal that has entered input terminal 2 in phase comparator 3, and the phase error between the two is Detected. The output phase error signal of the phase comparator 3 is a jitter signal, and this jitter signal is supplied to the electro-mechanical converter 5 via the jitter servo circuit 4, and is used to convert the time axis of the reproduced signal from the disk 7 into the reproducing element 6. Displace it in the direction that corrects the fluctuation. On the other hand, the reference signal input to the input terminal 2 is supplied to the motor servo circuit 9, where the phase is compared with the signal from the rotational phase detector 11.

The rotational phase detector 11 detects the rotational phase of the motor 10 that rotates the turntable 8 using, for example, a magnet and a magnetic head.
Alternatively, it is detected by a well-known configuration using a photoelectric element or the like, and a rotational phase detection signal having a frequency corresponding to the rotational phase is supplied to the motor servo circuit 9. The motor servo circuit 9 determines the rotational phase of the turntable 8 and the motor 10 at the input terminal 2.
The rotational phase of the motor 10 is controlled so as to match the phase of the input reference signal. In this way, according to the apparatus shown in the first figure, the disc 7 not placed on the turntable 8 can be
Therefore, the jitter component in the reproduced signal reproduced by the reproduction element 6 can be reduced.

However, the phase of the two force signals of the phase comparator 3 changes depending on the angle at which the disk 7 is placed with respect to the rotational phase detector 11 of the motor 10, and the reproducing element 6 is connected to the feed mechanism (Fig. (not shown) changes when the disk does not always move on a line passing through the disk rotation axis. However, the motor 10 is rotated at a constant speed regardless of the jitter signal, and the components from the phase comparator 3 to the electrical-to-mechanical converter 5 are DC-coupled, and all these phase changes are transferred to the electrical-to-mechanical converter 5. If an attempt is made to correct this, the movable range of the reproducing element 6 by the electro-mechanical converter 5 will be required to be extremely large. On the other hand, in the case of AC coupling, the phase is out of the detectable range due to a steady phase error, making it impossible to detect a normal jitter signal. Furthermore, the conventional time axis error correction device based on the heterodyne method is based on the vertical shift of the reproduced video signal. Since there is no color burst signal during the ranking period, a jitter signal cannot be obtained, and the error becomes large immediately after this period, causing buzzing noise in the playback sound of the audio signal recorded with the video signal. It was hot.

The present invention eliminates all of the above-mentioned drawbacks, and also makes it possible to easily correct time axis errors in reproduced video signals of different television systems. One example will be explained.

FIG. 2 shows a block diagram of an embodiment of the time axis error correction device according to the present invention.

In the figure, the same components as those in FIG. The video signal reproduced from the disk 7 is supplied from an input terminal 12 to a synchronization separation circuit 13, where the horizontal synchronization signal is separated. The phase of the horizontal synchronization signal is compared with the reference signal from the input terminal 14 in the phase comparator 15, and the resulting phase error signal, that is, the jitter signal, is sent to the jitter servo circuit 4 and the variable frequency oscillator 1.
6, respectively. Here, the jitter component included in the disk 7 ranges from the frequency component of the rotation period caused by eccentricity to the relatively high frequency component (about several hundred Hz to 1.5 kHz) caused by breath distortion. .

For this reason, correcting these jitters for the servo of the turntable 8 due to its inertia requires extremely large amounts of energy and is not a good method.It is necessary to rotate the turntable 8 evenly or to perform constant phase alignment control. It is appropriate to Therefore, it is appropriate to correct most of the jitter occurring in the re-output signal using jitter servo. Therefore, in order to constantly reduce jitter, in addition to the jitter servo, a turntable servo (motor servo) is also required, and as shown in FIG. 10 constitutes this turntable servo.

The jitter signal extracted from the phase comparator 15 is supplied to a variable frequency oscillator 16 to control its output oscillation frequency. This variable frequency oscillator 16, as shown in FIG.
Low-pass filter 18, voltage-controlled crystal oscillator (hereinafter referred to as Rvx
(denoted as OJ) 19 and a countdown circuit 20.

In the turntable servo, the jitter signal is first passed through the low-pass filter 18 in order to eliminate the steady phase error (DC phase error) between the reproduced horizontal synchronization signal and the reference signal.
After extracting only the low-frequency components through the VXOl 9, the output oscillation frequency is variably controlled. Although the VXO19 outputs oscillation at an extremely stable frequency, its variation range is approximately 0.2% or less even in peak-to-peak values, which is extremely narrow. The output signal of VXOl9 is counted down by the countdown circuit 20, and the output signal of the motor 1 at normal rotation is counted down by the countdown circuit 20.
The frequency is set to match the repetition frequency of the output pulse of the rotational phase detector 11 of 0.

For example, the output oscillation frequency of the XOl 9 is usually on the MHz order because it is cheap and stable, whereas the repetition frequency of the output pulse of the rotational phase detector 11 depends on the number of rotations of the disk 7, for example. 15rps
If the frequency is 750 pulses/Sec, the countdown is made to match this frequency. Actually, the color subcarrier frequency F. Crystal oscillators for horizontal synchronization signals are generally commercially available, so using these integrated circuits that output horizontal synchronization signals using XO with oscillation output of Become. The signal taken out from the countdown circuit 20 shown in FIG.
The signal is supplied to the motor control circuit 17 shown in the figure, where it is compared in phase with the output pulse of the rotational phase detector 11, converted into a signal according to their phase difference, and then applied to the motor 10.

As a result, the rotational phase of the motor 10 is controlled so that the phase error with respect to the reference signal phase from the variable frequency oscillator 16 becomes zero. Therefore, although the output of the variable frequency oscillator 16 is used as a reference signal to control the rotation of the motor 10, the variation range of the rotation of the motor 10 matches the extremely narrow variation range of the output of the VXOl 9. This means that even when the playback video signal does not come to the input terminal 12 because the disc playback device is in a playback pause state, the turntable 8 and motor 10 each substantially match the normal rotation speed. This means that it is rotating stably, and when the pause state is released and the reproduced video signal enters the input terminal 12, the DC phase error with the reference signal from the input terminal 14 becomes zero. The turntable servo will work. Conventionally, in order to match the phase between the reference signal and the reproduced signal (referred to as intersync), the jitter signal from the phase comparator 15 was directly used as a phase error signal for the motor 10, so the reproduced video signal was not input. A variety of complex changes were made in consideration of what would happen if the vehicle became unusable. Further, when the turntable 10 is started up, it is necessary to perform complicated sequence control such as detecting that the turntable 10 is rotating normally, and further detecting a reproduced video signal. On the other hand, according to this embodiment, since the VXOl9 is used, it always rotates at approximately the normal rotation speed, so the above-mentioned multiple rotations occur. Crude switching and complicated sequence control are not required. Furthermore, according to this embodiment, when detecting jitter by phase comparison other than heterodyne type jitter detection, the turntable servo is always applied to correct the above-mentioned phase error using XOl9. A normal jitter signal can be detected, and this normal jitter signal is phase-compensated in the jitter servo circuit 4 to match the characteristics of the electro-mechanical converter 5, and is supplied to the electro-mechanical converter 5, and the regenerating element 7 The jitter can be corrected by moving the child 6 at any time.

Furthermore, since intersync has become possible stably without complicated switching, the horizontal synchronization signal in the reproduced video signal can be used to detect jitter, which allows jitter to be detected even during periods where no color burst signal is present, such as during vertical blanking periods. Can be detected.

Therefore, it is possible to prevent the occurrence of bumpy noise in the reproduced audio that was conventionally caused by applying the jitter servo, and also to eliminate the worry that the color at the top of the screen may fluctuate in some cases. I can do it. Compared to the reproduced color burst signal, the reproduced horizontal synchronization signal is S/
Although it is inferior in terms of N, it is easily possible without any problem if the improvement degree of jitter servo is about 50 dB at the basic rotation frequency (However, in the case of so-called direct color reproduction, an improvement degree of 50 dB poses a problem, but the so-called In the case of heterodyne color reproduction, it is fully satisfied and there is no problem with jitter.

). In addition, in conventional devices that obtain jitter signals using color burst signals, color burst signals differ not only in frequency but also in the presence or absence of inversion for each horizontal scanning period depending on the difference in the television system. While it is difficult to switch to obtain a jitter signal, in this embodiment, the jitter signal is obtained using a reproduced horizontal synchronization signal whose only frequency differs depending on the television system, so compatible reproduction is possible. Switching to obtain a jitter signal is extremely easy.

Note that the horizontal synchronization signal of the NTSC system and PAL system is 0.
Since there is only a 7% frequency difference, the PAL system (or NTS
C format) video signal recording disc in the NTSC format (or P
By rotating 0.7% faster (or slower) than the normal rotation speed so as to obtain the horizontal scanning frequency of the NTSC method (or PAL method) video signal recording disk reproducing device. Since the circuit operates regardless of the program contents, compatible playback is possible. As described above, the time axis error correction device according to the present invention uses the horizontal synchronization signal and the reference signal of the reproduced video signal. A time axis error signal is generated by comparing the respective phases, the oscillation output frequency of the variable frequency oscillator is controlled by the generated time axis error signal, and the rotation phase of the motor for rotating the rotating information recording medium is detected using the oscillation output frequency. Since the rotation of the motor is controlled using the j error signal obtained by comparing the phase with the output of the detector, intersync is easy and stable.Also, since a regenerative synchronization signal is used, vertical block It is possible to correct time axis errors even during the ranking period, thereby preventing bumpy noises and color fluctuations at the top of the screen from occurring in the reproduced audio, and compatible playback with N'ISC and PAL systems. It is extremely easy to switch to obtain a time axis error signal during the process, and since the variable frequency oscillator uses a voltage-controlled crystal oscillator, the motor always rotates at approximately the normal rotation speed, so the reproduced video signal cannot be changed. This eliminates the need for complex switching in consideration of the situation when the voltage stops coming in, and complex sequence control from motor startup to the normal rotation speed. Since a filter circuit is provided that selects the frequency of the low frequency component of the input time axis error signal, the motor can be controlled to rotate so that its steady rotational phase error matches the reference signal, and thus the heterodyne time axis It has many features such as being able to always obtain a regular time axis error signal when detecting time axis errors by phase comparison other than error detection, and being able to always accurately correct time axis errors. .

[Brief explanation of the drawing]

Fig. 1 is a block system diagram showing an easily possible example of locking the reproduced signal to an external signal in a device that does not use the heterodyne jitter detection method, and Fig. 2 is a block diagram showing an embodiment of the device of the present invention. System Diagram, FIG. 3 is a block system diagram showing an embodiment of the essential parts of the second illustrated device. 1...Reproduction horizontal synchronization signal or color burst signal input terminal, 2, 14...Reference signal input terminal, 5
...Electrical-mechanical converter, 7...Rotating information recording medium (disc), 8...Turntable,
10... Motor, 11... Rotation phase detector, 12... Playback video signal input terminal, 16...
...Variable frequency oscillator, 17...Motor control circuit, 18...Low pass filter, 19...
...Voltage controlled crystal oscillator (VXO), 20... Countdown circuit.

Claims (1)

[Scope of Claims] 1. A device for correcting a time axis error included in a reproduced video signal of a rotating information recording medium by driving an electro-mechanical converter using a detected time axis error signal to shift a reproduction element. , generate the time axis error signal by comparing the phases of the horizontal synchronization signal of the reproduced video signal and the reference signal, control the oscillation output frequency of the variable frequency oscillator with the generated time axis error signal, and control the oscillation output frequency of the variable frequency oscillator. A time axis error correction device characterized in that the frequency is phase-compared with the output of a detector for detecting the rotational phase of the rotational motor of the rotational information recording medium, and the rotation of the motor is controlled by an error signal obtained. 2. The time axis error correction device according to claim 1, wherein the variable frequency oscillator is a voltage controlled crystal oscillator. 3. The time-base error correction device according to claim 2, further comprising a filter circuit for frequency-selecting a low-frequency component of the input time-base error signal before the voltage-controlled crystal oscillator. .