JPH0583982B2 - - 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, which reproduces a recording medium on which an information signal including a horizontal synchronization signal, a vertical synchronization signal, and a data signal is recorded. The present invention relates to a data reproducing device for obtaining a data signal from an information signal reproduced from a medium.

[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. I will explain what I did. FIG. 1 is a diagram showing a recording pattern of a circular track in this type of device.If the image information recorded on one circular track is field image information, the NTSC system is
This means that 262.5H worth of signals will be recorded. Here, H represents one horizontal synchronization period.

In accordance with the above recording format, 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
The delay line) is alternately switched by the switch circuit 7 for each field using PG pulses generated from the PG (pulse generator) head 19 via the 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 (oscillation frequency nfH) of this voltage controlled oscillator 13 is guided to a 1/n frequency divider 14 and a data sampling circuit 17. A signal with a frequency fH equal to the horizontal synchronizing signal is obtained from the 1/n frequency divider 14. , which becomes the other input of the phase detector 10.

That is, a PLL (phase locked loop) is formed here, and a signal having a frequency n times fH 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 separated by the sync data separation circuit 16, and the information data signal D is sampled by the output of the voltage controlled oscillator 13. Ru. The reproduced data signal thus obtained is temporarily stored in, for example, the memory circuit 18, and subjected to error correction, detection, etc., or is displayed on a monitor based on this data.

However, the rotation drive motor 1 for the magnetic sheet 1 shown in FIG. 4 usually has some degree of uneven rotation, and cases such as those shown in 5a and 5b may occur during recording.

These figures are explanatory diagrams of two examples of recording patterns caused by rotational fluctuations of the drive rotor 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. In addition, FIG. 5b shows the above-mentioned a
This is an example of the opposite case, that is, when the motor rotation time is longer than the length of one field.
Although overwriting is not performed at the start of writing, the interval of the reproduction horizontal synchronization signal changes. In particular, although this does not occur in case b, in case a, the horizontal synchronization signal written immediately after the start of writing may disappear due to overwriting.
At this time, even if 1/2H skew distortion correction is performed as shown in Figure 4, one horizontal synchronization signal will always be missing, so the problem is that the interval between the reproduced horizontal synchronization signals will change greatly. arise.

FIG. 6 shows an operational waveform diagram of each signal. In FIG. 6, A is the output of the 1/n frequency divider 14 in FIG. 4, which is the frequency fH, and B is the reproduced horizontal synchronizing 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 synchronization signal immediately after the start point in FIG. 5a,
This causes a malfunction in the output C of the phase comparator 10, and the oscillation frequency of the voltage controlled oscillator 13 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 bit. , a sampling error occurs and the data cannot be read correctly.

More precisely, if recording is ideally possible as shown in FIG. 1, and if 1/2H skew compensation 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 problems, and eliminates the unstable operation of the voltage controlled oscillator near the time of switching to the 1/2H skew correction circuit, which is a drawback of the conventional example described above. An object of the present invention is to provide a data reproducing device that can stably sample data.

〔Example〕

The present invention will be explained below based on the drawings. 8th
The figure is a block diagram of one embodiment of the main circuit configuration of the 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, the frequency divider that outputs a frequency-divided signal of the output of the voltage controlled oscillator to be compared with the reproduced horizontal synchronizing signal is reset only once by the reproduced vertical synchronizing signal (VD).

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 mono multi-circuit, which outputs a pulse of a certain length by the reproduction VD, and by this pulse, the period is 1/n.
4 is reset, and it is most desirable to set the timing of this reset immediately after reproducing the joint of the recorded signal of the circular track. Therefore, even if one of the horizontal synchronizing signals is missing during recording, the voltage controlled oscillator 13 will not malfunction, and there is no need for a 1/2H skew compensation circuit, simplifying the circuit configuration and simplifying the data. Sampling can be performed reliably.

〔effect〕

As explained above, according to the present invention, the frequency divider that divides the output of the voltage controlled oscillator is reset by the regenerated vertical synchronization signal, so the unstable operation of the voltage controlled oscillator is eliminated and data sampling is improved. This has the effect of being able to perform the process reliably and at the same time simplifying the circuit configuration.

[Brief explanation of drawings]

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 skew 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 reproducing a recording medium on which an information signal including a horizontal synchronization signal, a vertical synchronization signal, and a data signal is recorded, and for obtaining a data signal from the information signal reproduced from the recording medium, wherein the recording medium a sampling signal generator that generates a sampling signal for sampling the information signal reproduced from the recording medium in phase synchronization with a horizontal synchronization signal detected from the information signal reproduced from the recording medium; and a sampling signal generator generated by the sampling signal generator. a frequency divider for frequency-dividing and outputting a sampling signal to be output, and a phase comparison between a horizontal synchronization signal detected from an information signal reproduced from the recording medium and a signal output from the frequency divider, control means for controlling the sampling signal generator according to the result of the phase comparison, and for resetting the operation of the frequency divider according to the vertical synchronization signal detected from the information signal reproduced from the recording medium. A data reproducing device characterized by: