JPH0341296Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Field of Application> The present invention is a helical scan type segment type digital videotape recorder (hereinafter simply referred to as VTR) equipped with a rotating magnetic head device having a plurality of magnetic heads. ), etc., and particularly relates to a device for detecting the rotational positions of a plurality of magnetic heads provided in a rotary magnetic head device whose rotational speed is freely switchable.

<Background technology and its problems> Generally, in a helical scan VTR,
One rotational phase detection pulse (so-called PG) is generated for each rotation of the drive shaft of the motor that drives the rotating magnetic head device.
pulse) and a large number of speed detection pulses (so-called FG pulses) during one rotation, and by applying a phase servo based on the PG pulse and a speed servo based on the FG pulse to the motor, the rotation can be controlled. Signals are recorded and reproduced by controlling the magnetic head device to a constant rotation.

By the way, in a segment type digital VTR that records and plays digital video signals using a rotating magnetic head device equipped with a plurality of magnetic heads, a digital video signal divided into a plurality of segments is sent to each magnetic head corresponding to each segment. Since recording and reproduction are performed using a magnetic tape, it is necessary to accurately detect the leading position of each segment of a video signal recorded on a magnetic tape in order to perform signal processing during reproduction.

Conventionally, for example, as shown in FIG.
In a segment type digital VTR in which a recording track on a magnetic tape 11 is traced by a rotating magnetic head device having four magnetic heads 1, 2, 3, and 4 at the same time, the rotation of the rotating drum 10 is As shown in FIG. 2, four delay circuits 15, 16, 17, and 18 process the PG pulse for rotational phase servo obtained by the PG head 12, which detects the phase, that is, the rotational phase of the drive shaft of the motor (not shown).
is supplied to a rotational phase detection device consisting of a continuous connection of
A position detection pulse corresponding to the leading position of each segment of the digital video signal was obtained via each delay circuit 15, 16, 17, and 18.

By the way, the luminance signal Y that constitutes the video signal,
In a digital component VTR that digitizes and handles each component signal of each color difference signal B-Y, R-Y, each component signal Y, B-
When digitizing Y, R-Y, the sampling rate is sometimes 4:2:2 or 2:1:1, and there is a need for equipment that can support both systems with each sampling rate. There is. By reducing the tape running speed and drum rotation speed to 1/2 of 4:2:2 for a system with a sampling rate of 2:1:1, each system can be compatible with the same tape format. That's what I do.

In this way, in a VTR that switches the tape running speed and drum rotation speed to achieve both systems, the leading position of each segment of the video signal is detected using the conventional rotational position detection device shown in Figure 2 above. In order to obtain a position detection pulse indicating , the amount of delay of each delay circuit 15, 16, 17, 18 must be changed in accordance with each system.

<Purpose of the invention> In view of the above-mentioned problems with conventional rotational position detection devices, the present invention has been developed to constantly accurately determine the rotational position of each magnetic head of a rotating magnetic head device in a VTR in which the tape running speed and drum rotational speed are switched. The present invention provides a rotational position detection device capable of outputting a signal indicating the leading position of a segment on a recording medium to which each magnetic head corresponds.

<Summary of the invention> In order to achieve the above-mentioned object, the present invention provides a rotating body with a plurality of magnetic heads for recording and/or reproducing a video signal divided into a plurality of segments on a recording medium. Generating one PG signal for each rotation of the rotating body and generating a plurality of FG signals for each rotation of the rotating body, and controlling the rotational phase of the rotating body based on the PG signal, In a rotational position detection device for detecting the rotational position of the rotary body of a rotating magnetic head device in which the rotational speed of the rotary body is controlled based on the FG signal, based on the PG signal and the FG signal. , initialized by the above PG signal,
A counter circuit for counting the FG signals, and a decoder circuit for decoding the count output from the counter circuit and outputting a segment start position signal indicating the start position of the segment corresponding to each of the plurality of magnetic heads. This is what I did.

<Example> Hereinafter, an example of the rotational position detection device according to the present invention will be described in detail with reference to the drawings.

FIG. 3 shows each magnetic head 1, 2, 3,
4 shows an embodiment of the rotational position detection device No. 4.

Here, it is assumed that the rotating magnetic head device in the VTR to which the present invention is applied is subjected to rotational phase control based on PG pulses and rotational speed control based on FG pulses.

In the embodiment shown in FIG. 3, the first signal input terminal 21 is supplied with a PG pulse for controlling the rotational phase of the rotary magnetic head device. This PG pulse is generated by a PG pulse generator for each rotation of the rotating magnetic head device, and is generated by the PG pulse generator.
The signal is supplied from the signal input terminal 21 to the counter circuit 25 as a reset pulse.

Further, the second signal input terminal 22 is supplied with an FG pulse for controlling the rotational speed of the rotating magnetic head device. These FG pulses are generated by a predetermined number of FG pulses per one rotation of the rotating magnetic head device by an FG pulse generator (not shown).
The signal is supplied from the signal input terminal 22 to the counter circuit 25 as a clock pulse.

The counter circuit 25 is reset and initialized by the PG pulse, and counts the FG pulse. The count output from the counter circuit 25 indicates the position information obtained by dividing one rotation, that is, 360°, of the rotating magnetic head device into n by the number n of FG pulses per one rotation of the rotating magnetic head device. The count output of the counter circuit 25 is:
The signal is supplied to a decoder circuit 30.

The decoder circuit 30 decodes the counting output so that each magnetic head 1, 2, 3, 4
A rotational position detection signal indicating the rotational position of is outputted from the first to fourth signal output terminals 31, 32, 33, and 34. That is, each magnetic head 1, which is provided on the rotating drum 10 of the rotating magnetic head device as described above,
Since the relative positional relationship between 2, 3, 4 and the PG head 12, that is, the PG pulse generator, is fixed, the decoder circuit 30 outputs the count output of the counter circuit 25 that is set as desired by the PG pulse. Each magnetic head 1, 2,
3 and 4 rotational positions can be detected.

Here, each reproduction output signal from each magnetic head 1, 2, 3, 4 in the rotary head device shown in FIG. 1 above and each signal output terminal 31, 32, 33 in the embodiment shown in FIG. , 34 are shown in the time chart of FIG.

Generally, FG pulse generators include a phase error in the generated FG pulses depending on the method of use and processing precision. When used to detect the beginning position of each segment, as shown in the time chart of FIG.
By specifying the section where 2, 3, and 4 are correct with the above FG pulse, initial address setting for time axis correction processing in the VTR playback system, etc. can be performed using a position detection signal based on the above pulse. Therefore, it is possible to obtain sufficient accuracy for practical use.

In the embodiment configured as described above, when the rotational speed of the rotating magnetic head device is switched, the generation timing of the PG pulse and the FG pulse changes according to the rotational speed, so that the timing of generating the PG pulse and the FG pulse is always changed regardless of the change in the rotational speed. Each magnetic head 1, 2, 3, 4
A digital component that can accurately detect the rotational position of the magnetic head and output a signal indicating the beginning position of the segment on the recording medium to which each magnetic head corresponds. A rotational position detection device suitable for VTRs can be realized.

<Effects of the invention> As is clear from the description of the embodiments described above, the rotational phase detection device according to the invention uses a PG pulse for controlling the rotation of a rotating magnetic head device in a VTR.
By effectively utilizing the FG pulse, the leading position of the corresponding segment of each magnetic head can always be accurately detected regardless of the rotation speed, and the intended purpose can be fully achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the general configuration of a rotating magnetic head device in a segment type digital VTR to which the present invention is applied. FIG. 2 is a block diagram showing a conventional example of a rotational position detecting device for detecting the rotational position of each magnetic head provided in the rotating magnetic head device shown in FIG. 1.
FIG. 3 is a block diagram showing an embodiment of the rotational position detection device according to the present invention. FIG. 4 is a time chart showing the operation of the above embodiment. 1, 2, 3, 4...magnetic head, 10...rotating drum, 11...magnetic tape, 12...PG head, 25...counter circuit, 30...decoder circuit.

Claims (1)

[Claims for Utility Model Registration] A plurality of magnetic heads for recording and/or reproducing video signals divided into a plurality of segments onto a recording medium are provided on a rotating body, one of the rotating bodies is
generating one first pulse signal for each rotation, and generating a plurality of second pulse signals for each rotation of the rotating body, and controlling the rotational phase of the rotating body based on the first pulse signal; The rotational position of the rotating body of the rotating magnetic head device is controlled based on the first pulse signal and the second pulse signal. In a rotational position detection device that detects based on a pulse signal, the rotational position is initialized by the first pulse signal, and
a counter circuit that counts the second pulse signal; a decoder circuit that decodes the count output from the counter circuit and outputs a segment start position signal indicating the start position of the segment to which each of the plurality of magnetic heads corresponds; A rotational position detection device comprising: