JPH04307452A - Magnetic tape reproducing device - Google Patents

Abstract

PURPOSE:To accurately control a rotary phase without adjusting it from the outside by eliminating a rotary position reference unit for controlling the rotary phase of a cylinder, a rotary pulse generator and a one-shot multivibrator. CONSTITUTION:A synchronizing signal (j) in a data to be reproduced by the speed controlled rotary cylinder 2 is detected by a synchronizing signal detector 17. A rear half part of the synchronizing signal recorded in the front half and the rear half of a track is selected by a synchronizing signal selector 18. When the synchronizing signal recorded in the rear half part of the track is selected, a reproduction phase signal (l) is generated after a prescribed fixed time by a reproduction phase signal generator 19. This prescribed fixed time is from the time of detecting the synchronizing signal in the rear half part of the track to the time the beginning of the next track contacts the head. The rotary phase of the rotating cylinder 2 is controlled by comparing a rotary phase reference signal (g) from a rotary phase reference signal generator 14 with the reproduction phase signal (l) in phase and making their phase difference approach zero.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape playback device that can be used in playback-only digital audio tape recorders (referred to as DATs) and video tape recorders (referred to as VTRs).

0002

2. Description of the Related Art A magnetic tape playback device that uses a rotating head for playback is equipped with a rotational speed detector that detects the rotational speed of a rotating cylinder and a rotational phase detector that detects the rotational phase of the rotating cylinder. The rotation of the rotary cylinder is controlled to match the reference signal, and the data on the magnetic tape is reproduced.

An example of a conventional magnetic tape reproducing device will be described below with reference to the drawings. FIG. 4 is a block diagram showing the configuration of a conventional magnetic tape reproducing apparatus, and FIG. 5 is a signal waveform diagram during reproduction. In FIG. 4, 1 is a magnetic tape, 2 is a rotary cylinder, 3 is an arrow indicating the rotation direction of the rotary cylinder 2, 4A and 4B are heads attached to the rotary cylinder 2, and 5 is an amplification of the output of the heads 4A and 4B. Head amplifier, 6 is playback output terminal, 7 is rotating cylinder 2
signal with a frequency proportional to the rotation speed (hereinafter referred to as FG)
8 is a rotation speed reference signal generator that generates a constant frequency rotation speed reference signal for controlling the rotation speed of the rotary cylinder 2; 9 is a rotation speed reference signal b and an FG signal a; 10 is a rotational position reference device mounted on the same axis of the rotation cylinder 2 forward of the head 4A in the rotational direction; 11 is a rotational position reference device 10 The rotational position signal d is one pulse per rotation of the rotating cylinder 2.
12 is a one-shot multivibrator that delays the rotational position signal d by a predetermined time; 13 is a rotational phase signal (hereinafter referred to as PG signal) e which extracts the falling edge of the one-shot multivibrator 12; 14 is a rotational phase reference signal generator that generates a rotational phase reference signal g of a constant period for controlling the rotational phase of the rotary cylinder 2; 15 is a rotational phase reference signal generator that generates a rotational phase reference signal g and a PG signal f; A phase error detector 16 compares and outputs a rotational phase error h of the rotary cylinder 2, and 16 is a rotation control circuit that adds the rotational speed error c and the rotational phase error h to control the rotational speed and rotational phase of the rotary cylinder 2. .

The operation of the magnetic tape reproducing apparatus constructed as described above will be explained below using the signal waveform diagram shown in FIG.

First, control of the rotational speed of the rotating cylinder will be explained. Section T1 in FIG. 5 shows a case where the rotating cylinder 2 deviates from a predetermined rotational speed. The rotational speed detector 7 outputs the FG signal a, and the speed error detector 9 compares the period T6 of the rotational speed reference signal b with the period T5 of the FG signal a, and generates a speed error voltage c proportional to the difference in period. Output. The rotation control circuit 16 controls the rotation speed of the rotary cylinder 2 so that the speed error voltage c becomes zero. Section T2 in FIG. 5 is a state in which the rotational speed of the rotary cylinder is synchronized with the rotational speed reference signal b, and the speed error voltage c is zero.

Next, the pulse width T of the output pulse e of the one-shot multivibrator 12 is adjusted in advance so that the rotational phase signal f is output when the head 4A reaches the beginning of the track.
Control of the rotational phase will be explained using a magnetic tape playback device in which the PG is adjusted (this adjustment is referred to as PG adjustment). Figure 5
Section T3 indicates a case where the rotating cylinder 2 deviates from a predetermined rotational phase. When the rotational position reference device 10 passes in front of the rotational pulse generator 7, a rotational position signal d is output, and the rotational position signal d is delayed by a certain time (T) by the one-shot multivibrator 12. Differential circuit 13
is the output pulse e of the one-shot multivibrator 12
The falling edge of is differentiated to create a rotational phase signal f. The phase error detector 15 compares a predetermined rotational phase reference signal g input from the device with a rotational phase signal f, and outputs a rotational phase error voltage h proportional to the phase difference θ. The rotation control circuit 16 controls the rotation phase of the rotary cylinder 2 so that the rotation phase error voltage h becomes zero (θ is zero). Section T4 in FIG. 5 shows a state in which the rotational phase of the rotary cylinder 2 is synchronized with the rotational phase reference signal g. At this time, the head 4A is at the rising position of the rotational phase reference signal g, and at the same time, the head 4A is at the rising position of the rotational phase reference signal g.
Since A is at the beginning of the track, normal playback is possible.

As described above, a magnetic tape can be reproduced by detecting the FG signal and rotational position signal output from the rotating cylinder and controlling the rotational speed and rotational phase of the rotating cylinder.

[0008]

However, in the conventional configuration described above, the rotational phase is controlled by the rotational position reference device 10 and the rotational position reference device 10 located in front of the head 4A on the rotating cylinder.
It is necessary to attach the rotating pulse generator 11 with high accuracy so as to face the rotating pulse generator 11, which is difficult due to the construction method.In addition, a one-shot multivibrator is used so that the heads 4A and 4B can be traced from the beginning of the track in synchronization with the rotational phase reference signal g. It is necessary to adjust the output pulse width T of the output pulse width T, which is expensive due to the manufacturing process.Since PG adjustment is performed by playing back the reference tape, if a magnetic tape whose track start position is different from the reference tape is played, the rotation The rising position of the phase reference signal and the playback output signal at the start end of the track may deviate, and normal playback may not be possible.

The present invention solves the above-mentioned conventional problems, and eliminates the rotational position reference device, rotational pulse generator, and one-shot multivibrator, and allows the rotational cylinder to rotate with high precision without adjusting the rotational phase from the outside. An object of the present invention is to provide a magnetic tape playback device that controls the phase.

0010

[Means for Solving the Problems] In order to achieve this object, the magnetic tape reproducing device of the present invention forms tracks diagonally on a magnetic tape, and positions the tracks at a plurality of predetermined positions on each track of the magnetic tape. This device plays back a magnetic tape on which a synchronization signal indicating information is recorded, and includes a rotating cylinder to which a head is attached, a head amplifier that amplifies the playback signal from the head, and a predetermined signal recorded on the magnetic tape. a synchronization signal detection circuit for detecting a synchronization signal; a reproduction phase signal generator that outputs a reproduction phase signal after a certain period of time when the synchronization signal detection circuit detects a predetermined synchronization signal;
a rotational phase reference signal generator that generates a constant period rotational phase reference signal for controlling the rotational phase of the rotating cylinder;
The configuration is such that the phase of the rotary cylinder is controlled so that the reproduction phase signal is synchronized with the rotational phase reference signal.

[0011]

[Operation] With the above-described configuration, when the synchronization signal detection circuit detects a synchronization signal recorded at a predetermined location on a track of a magnetically recorded magnetic tape, the head position at that time can be known. The rotational phase of the head is created by generating a pulse when the cylinder reaches the start or end position of a track, and by synchronizing the rotational phase signal with the rotational phase reference signal, the phase of the rotating cylinder can be controlled. Normal playback becomes possible.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic tape reproducing apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a magnetic tape reproducing apparatus according to an embodiment of the present invention, FIG. 2 is an example of a magnetic tape on which a synchronizing signal is recorded, and FIG. 3 is a signal waveform diagram of FIG. 1. It is something. 1 and 2, those having the same symbols as those in FIG. 4 are the same as those in the conventional example, and therefore the description thereof will be omitted.

In FIG. 2, 21A is a positive azimuth track (hereinafter referred to as A track) that can be reproduced by head 4A, and 21B is a negative azimuth track (hereinafter referred to as B track) that can be reproduced by head 4B. 21B are recorded alternately as shown. 22AI is a synchronization signal recorded in the first half of the A track 21A, 22AO is a synchronization signal recorded in the second half of the A track 21A, and 22AI, 22AO
are both recorded at frequency f1. 22BI is the synchronization signal recorded in the first half of the B track 21B, 2
2BO is a synchronization signal recorded in the latter half of the B track 21B, and 22BI and 22BO are both recorded at frequency f2. The synchronization signal is detected when the head travels on a track at a predetermined speed while reproducing a magnetic tape, and is a signal that takes timing for detecting the amplitude values of tracking signals of both adjacent tracks where the head is located. The head can trace the center of the track by running the magnetic tape so that the difference in amplitude values of the tracking signals of both adjacent tracks approaches zero. Further, this synchronization signal is recorded at a predetermined constant position on the track. 3 is an arrow indicating the direction of movement of the head;
T7 is on the B track 21B and the head receives the synchronization signal 22BI.
T8 is the time it takes for the head to reach the end of the track from the synchronization signal 22BO on the negative azimuth track 21B, and 23 is an arrow indicating the direction of movement of the magnetic tape.

FIG. 1 shows a magnetic tape playback device in which the tape is wound around a cylinder rotating 180 degrees.
7 is a synchronization signal detector 18 for detecting synchronization signals 22BI and 22BO recorded in the tracking signal on the tape;
19 is a synchronizing signal selector that selects the synchronizing signal 22BO recorded in the latter half of the track, and a reproduction phase signal generator 19 generates a pulse after a certain period of time when the synchronizing signal 22BO is detected.

The operation of the magnetic tape reproducing apparatus constructed as described above will be explained below with reference to FIGS. 1, 2, and 3.

When the rotating cylinder 2 starts rotating, the speed error detector 9 compares the period of the FG signal a outputted from the rotational speed detector 7, which is proportional to the rotational speed of the rotating cylinder, with the period of the rotational speed reference signal b. and outputs a rotational speed error voltage c proportional to the period difference. The rotation control circuit 16 controls the rotation cylinder 2 to a predetermined rotation speed so that the rotation speed error voltage c becomes zero. When the rotary cylinder 2 rotates at a predetermined speed, a reproduction output signal i is output from the reproduction output terminal 6. When the synchronization signal detector 17 detects the synchronization signals 23BI and 23BO from the head output signal of the B track, it outputs a detection output j. When the synchronization signal j is detected, the synchronization signal selector 18 checks the detection of the synchronization signal after a certain period of time (T7). If a synchronizing signal is detected after a certain period of time (T7), it is determined that the signal is a synchronizing signal for the latter half of the track, and a synchronizing signal selection output k is output. When the output k of the synchronization signal selector 18 is input, the reproduction phase signal generator 19 generates the reproduction phase signal l after a certain period of time (T8). Here, T8 is predetermined so that the reproduction phase signal is output when the position of the head 4A reaches the starting position of the A track. The phase error detector 15 compares a predetermined rotational phase reference signal g and the reproduced phase signal l, and outputs a rotational phase error voltage h proportional to the phase difference θ. The rotation control circuit 16 controls the rotation phase of the rotary cylinder 2 so that the rotation phase error voltage h becomes zero. When the rotational phase error voltage h becomes zero, the output pulse of the reproduction phase signal l and the rising edge of the rotational phase reference signal g coincide, and at this point the head 4A is
The heads 4A and 4B are positioned at the starting ends of the tracks and trace from the starting ends of tracks A and B, respectively, in synchronization with the rotational phase reference signal g, thereby enabling stable reproduction of the magnetic tape.

Note that in FIG. 3, the synchronization signal is detected on the B track and the phase of the rotating cylinder is controlled, but the synchronization signal is detected on the A track and the reproduced phase signal i is output at the beginning of the B track. However, the rotation cylinder two-phase control may be performed by comparing the phase with the falling edge of the rotation phase reference signal g. Furthermore, in a device in which the tape is wound around a 90 degree rotating cylinder, control equivalent to the above operation can be achieved by changing the detection frequencies T7 and T8 of the synchronizing signal detector 17.

As described above, according to this embodiment, a synchronization signal recorded at a predetermined location on a track is detected, a phase signal of a rotating cylinder is generated based on the synchronization signal, and a rotation phase reference signal is generated. The magnetic tape can be reproduced by controlling the rotational phase of the rotary cylinder by comparing the phases.

[0020]

[Effects of the Invention] As described above, according to the present invention, based on the synchronization signal in the data reproduced from the magnetic tape by the head, the rotary position reference device conventionally attached to the rotary cylinder is detected. The rotational phase of the rotating cylinder can be controlled by generating a phase signal equivalent to the rotational phase signal and comparing the phase with the rotational phase reference signal, so the rotational position reference device, rotational pulse generator, and one-shot multivibrator can be omitted. This makes it possible to provide an inexpensive device that does not require phase adjustment.Also, even when playing a magnetic tape whose track start position is shifted, the position where the synchronization signal is recorded and the position of the start end of the track are constant. Therefore, the reproduction phase signal is always output at the beginning of the track, making stable reproduction possible and having a great effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a magnetic tape playback device in an embodiment of the present invention.

[Figure 2] Schematic diagram of a magnetic tape to explain the operation of the same embodiment

[Figure 3] Signal waveform diagram for explaining the operation of the same embodiment

[
Figure 4: Block diagram showing the configuration of a conventional magnetic tape playback device

[Figure 5] Signal waveform diagram for explaining the operation of the conventional example

[Explanation of symbols]

1 Magnetic tape 2 Rotating cylinder 4A, 4B head 5 Head amplifier 7 Rotation speed detector 9 Speed error detector 15 Phase error detector 16 Rotation control circuit 17 Synchronization signal detector 18 Synchronization signal selector 19 Reproduction phase signal generator

Claims (2)

[Claims] Claim 1: Forming diagonal tracks on a magnetic tape,
A device for reproducing a magnetic tape in which synchronization signals indicating position information are recorded at a plurality of predetermined locations on each track of the magnetic tape, the device includes a rotating cylinder to which a head is attached, and amplifying the reproduction signal from the head. a head amplifier for detecting a predetermined synchronization signal recorded on the magnetic tape; a synchronization signal detection circuit for detecting a predetermined synchronization signal recorded on the magnetic tape; and when the synchronization signal detection circuit detects a predetermined synchronization signal, outputting a reproduction phase signal after a certain period of time. a regenerative phase signal generator; a rotary phase reference signal generator that generates a rotational phase reference signal with a constant period for controlling the rotational phase of the rotary cylinder; A magnetic tape playback device equipped with a rotation control circuit that controls the phase of a cylinder. 2. The synchronization signal is recorded at one location each in the first half and the second half of the track on the magnetic tape, and when the synchronization signal detecting circuit detects the same synchronization signal at two consecutive locations within a predetermined period of time, 2. The magnetic tape reproducing apparatus according to claim 1, wherein the second detected synchronization signal is enabled.