JPH053792B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a data reproducing device, and particularly to a data reproducing device that reproduces a data signal recorded together with a synchronizing signal based on the synchronizing signal.

[Prior art]

In this specification, as an apparatus of this type, a conventional still image recording/reproducing apparatus is used in which a rotating magnetic sheet is used to record one field's worth of video signals on a circular track, and this is repeatedly reproduced to obtain a still image. Explain things. FIG. 1 is a diagram showing the recording pattern of circular tracks in this type of device.If the image information recorded on one circular track is field image information, the NTSC system
This means that 262.5H worth of signals will be recorded. Here, H represents one horizontal synchronization period.

In accordance with the recording format described above, a method has been proposed in which digital binary data is written in place of these video signals to store information required by the user.

FIG. 2 shows the format of the recording signal at that time, where A is a horizontal synchronizing signal section, B is a sync data section, and C is an information data section.

The data is reproduced based on the horizontal synchronization signal, but since only 262.5H of one round is recorded, the reproduced horizontal synchronization signal always has a 1/2H skew at the field switching section.
FIG. 3 is a timing chart of this reproduced horizontal synchronizing signal, and is a diagram explaining the above-mentioned 1/2H skew.
In order to eliminate this skew, a 1/2H skew compensation circuit is provided in a normal regenerator.

FIG. 4 is a block diagram of an example of a conventional general data reproducing device. 1 is a drive motor, 2 is a rotating magnetic sheet, 3 is a reproducing head, and the reproducing head 3
The recorded signal reproduced from the magnetic sheet 2 passes through a reproduction amplifier 4, and then is demodulated by a demodulator 5 into the base hand area. Since the demodulated signal is a repetition of one field, the above 1/2
The signal contains H skew, and is led to a skew distortion corrector 8 for correcting this. This skew distortion corrector 8 is connected to the original signal and the 1/2H delayed signal (6 is 1/2H
delay line) are alternately switched by the switch circuit 7 for each field using PG pulses generated from a PG (pulse generator) head 19 via a pulse shaper 20 and synchronized with the rotation of the magnetic sheet 2. . The reproduced signal from which the 1/2H skew has been removed in this way is sent to the horizontal synchronization signal separation circuit 9,
clamp circuit 15. The horizontal synchronization signal separated by the horizontal synchronization signal separation circuit 9 is introduced as one input of a phase detector 10, and the output of this phase detector 10 is passed through an LPF (low pass filter) 11.
The signal passes through the amplifier 12 and becomes a control signal for the voltage controlled oscillator 13. The output of this voltage controlled oscillator 13 (oscillation frequency n _H ) is guided to a 1/n frequency divider 14 and a data sampling circuit 17 . A signal with a frequency _H equal to that of the horizontal synchronizing signal is obtained from the 1/n frequency divider 14, and this becomes the other input of the phase detector 10.

That is, a PLL (phase locked loop) is formed here, and a signal with a frequency n times _H synchronized with the reproduced horizontal synchronizing signal is obtained from the voltage controlled oscillator 13. Then, the sync data signal S and the information data signal D whose DC level has been reproduced by the clamp circuit 15 are
The information data signals D are separated by the data separation circuit 16 and sampled by the output of the voltage controlled oscillator 13. The reproduced data signal obtained in this way is temporarily stored in, for example, the memory circuit 18, and subjected to error correction, detection, etc.
Alternatively, a monitor display or the like is performed based on this data.

However, the rotation drive motor 1 for the magnetic sheet 1 shown in FIG. 4 usually has some degree of rotational unevenness, and during recording, cases such as those shown in FIGS. 5a and 5b may occur. These figures are explanatory diagrams of examples of two recording patterns caused by rotational fluctuations of the drive motor 1. FIG. 5a shows an example where the time for one rotation of the drive motor is shorter than one field, and overwriting is performed in the sheet rotation direction for a certain amount of time from the start of writing. Furthermore, FIG. 5b is an example of the opposite case to a above, that is, the time for one motor revolution is longer than the length of one field, and in this case, overwriting is performed at the start of writing. However, the interval of the reproduced horizontal synchronization signal changes. In particular, this does not occur in case b, but in case a, there is a possibility that the horizontal synchronization signal written immediately after the writing start point disappears due to overwriting, and in this case, as shown in Figure 4. Even if 1/2H skew distortion correction is performed, 1
Since each horizontal synchronizing signal is always missing, a problem arises in that the interval between the horizontal synchronizing signals varies greatly.

FIG. 6 shows an operational waveform diagram of each signal. In FIG. 6, A is the 1/n frequency divider 14 in FIG.
The output is the frequency of _H , and B is the reproduction horizontal synchronization signal output. C is the output of the phase detection circuit 10, which generates an output pulse for a period corresponding to the phase difference between A and B. D uses this as LPF
11, which controls the voltage controlled oscillator 13. In this case, B-2
The absence of the second pulse corresponds to the disappearance of the horizontal synchronizing signal immediately after the start point in FIG. The oscillation frequency fluctuates greatly in response to this, and as a result, the sampling pulse in the data sampling circuit 17 cannot be synchronized with the data bits, a sampling error occurs, and data cannot be read correctly.

More precisely, if recording is ideally possible as shown in FIG. 1, and if 1/2H skew correction is switched accurately at the start of writing, the reproduced horizontal synchronization signal obtained from the horizontal synchronization signal separation circuit 9 will be:
The operating waveform diagram C in Figure 7 shows the switching point.
A horizontal synchronization signal will also appear immediately after t ₀ . Here, A is from the original signal, and B is from 1/
This is a horizontal synchronization signal separated from the 2H delay signal.
In this case as well, a problem arises in that the phase detector 10 malfunctions at the time of switching.

〔the purpose〕

The present invention has been made in view of the above-mentioned problems, and eliminates the unstable operation of the voltage controlled oscillator near the switching point, which is a drawback of the conventional example described above, and provides stable data data with a simple circuit configuration. The purpose of the present invention is to provide a playback device capable of sampling.

〔Example〕

The present invention will be explained below based on the drawings. 8th
This figure is a block diagram of one embodiment of the main circuit configuration of a reproducing apparatus according to the present invention, and the same or similar components as in the conventional example shown in FIG. 4 are designated by the same reference numerals.

In this embodiment, a frequency divider that outputs a divided voltage controlled oscillator output that is compared to a regenerative horizontal sync signal is attempted to be reset with the regenerative horizontal sync signal immediately following the timing pulse associated with the rotation of the rotating magnetic sheet. It is something.

In FIG. 8, 14 is a 1/n frequency divider, which divides the output of the voltage control generator 13 into the same period as the reproduced horizontal synchronizing signal. On the other hand, 21 is a flip-flop circuit, and this circuit is reset by the reproduced horizontal synchronizing signal that comes immediately after being set by the PG pulse, and the 1/n frequency divider 14 is reset by this pulse. Therefore, even if one of the horizontal synchronizing signals is missing during recording, the voltage controlled oscillator 13 will not malfunction, and 1/2
No H skew compensation circuit is required, the circuit configuration is simplified, and data sampling can be performed reliably.

〔effect〕

As explained above, according to the present invention, the frequency divider that divides the output of the controlled oscillator is reset by the reproduced horizontal synchronizing signal immediately after the timing pulse obtained in relation to the rotation of the recording medium. The unstable operation of the controlled oscillator is eliminated, data sampling can be performed reliably, and the circuit configuration can be simplified.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a circular recording track pattern, Fig. 2 is a recording signal format diagram, Fig. 3 is a timing chart showing a reproduction horizontal synchronization signal, and Fig. 4 is an example of a conventional data reproducing device. block diagram,
FIGS. 5a and 5b are explanatory diagrams of two cases due to rotational fluctuations of a conventional drive motor, and FIGS. 6 and 7 are
FIG. 8, which is a conventional operational waveform diagram of each signal, is a block diagram of an embodiment of the main circuit configuration of the data reproducing apparatus according to the present invention. 1... Drive motor, 2... Rotating magnetic sheet, 3
... Reproduction head, 4 ... Reproduction amplifier, 5 ... Demodulator, 8 ... Skew distortion corrector (1/2H ski compensation circuit), 10 ... Phase detector, 11 ... Low pass filter (LPF), 12 ...Amplifier, 13...Voltage controlled oscillator, 14...1/n frequency divider, 16...
Sink/data separation circuit, 17...Data sampling circuit, 18...Memory circuit, 19...PG
Head, 20...Pulse shaping circuit, 21...Flip-flop circuit.

Claims (1)

[Claims] 1 A device for obtaining a reproduced data signal from a circular track on a recording medium on which an information signal including a horizontal synchronizing signal and a data signal is recorded, and which is generated by the output of a controlled oscillator whose phase is synchronized with the reproduced horizontal synchronizing signal. sampling the reproduction information signal to reproduce a data signal, comparing the phases of the reproduction horizontal synchronization signal and a signal obtained by dividing the output of the control oscillator by a frequency divider, and controlling the control oscillator according to the phase difference; A data reproducing apparatus characterized in that the frequency divider is configured to be reset by a reproduction horizontal synchronization signal immediately after a timing pulse obtained in connection with rotation of the medium.