JP3225629B2 - Playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a digital VT
The present invention relates to a reproducing apparatus suitable for use in R.

[0002]

2. Description of the Related Art For example, in a VTR, the recording density has been increased, and as a means therefor, the recording track on a tape has been narrowed. In particular, in digital VTRs for recording and reproducing signals with digital data, the recording is made multi-track, so that the width is further reduced.

[0003] Tracking control of such a narrow recording track is no longer possible, for example, by a conventional method using a CTL track. Therefore, the applicant of the present application has previously proposed a tracking control method for such a narrow recording track (Japanese Patent Application No. Hei.
114802).

FIG. 6 shows a recording pattern used in the prior application. In this pattern, a pilot signal for tracking control (frequency f ₂ ) is recorded every four tracks, and a signal for detection (frequency f ₁ ) is recorded on tracks on both sides thereof. During normal reproduction of this recording pattern, tracking control is performed by detecting crosstalk of a pilot signal (f ₂ ) reproduced by a head reproducing the track A on the entrance side and a head reproducing the track B on the exit side. To be done.

However, when tracking control is performed using such a recording pattern, for example, at the time of startup, if the relationship between the head and the recording track having alternately different azimuth angles is exactly reversed, Therefore, it is not possible to detect the reproduction of the signal for performing the tracking control, and it takes a long time until a correct tracking state is obtained. Therefore, the time required to obtain a reproduced image after a correct tracking state at the time of startup is not uniform, which may cause a problem in terms of commercial value. The present application has been made in view of such a point.

[0006]

The problem to be solved is that the time required for a correct tracking state at the time of startup and a reproduced image to be obtained is not uniform.

[0007]

A first means according to the present invention is based on a pilot signal recorded on a track.
In an AFT type reproducing apparatus that performs tracking by
Speed control is performed so that the tape transfer speed at the time of startup is less than the standard tape transfer speed , and the first zero-cross detection in the tracking error signal (ATF circuit 4) in the reproduction signal at that time is performed. A playback apparatus characterized in that when a predetermined time has elapsed, the tracking control is started by controlling the speed to a standard tape transfer speed.

[0008] A second means according to the present invention is to record data on a track.
Tracking based on recorded pilot signal
In the AFT-type reproducing apparatus, the tape transfer speed at the time of startup is controlled to be lower than the standard tape transfer speed ,
The first maximum value in the envelope (low-pass filter 5) of the reproduction signal at that time is detected, and when a predetermined time has elapsed from the detection, the speed control is performed to the standard tape transfer speed to start the tracking control. A reproducing apparatus characterized in that:

A third means according to the present invention is such that one field is divided into a plurality of tracks for recording, and a recording medium on which a pilot signal is recorded on one track for every four tracks is mounted to reproduce the pilot signal. A tracking device according to claim 1, wherein the tracking control is performed by using the tracking control described in the first means or the second means.

[0010]

According to this, it is possible to equalize the time until the correct tracking state is obtained at the time of activation or the like and a reproduced image is obtained.

[0011]

FIG. 1 shows the structure of a main part. In this figure,
A signal reproduced by the head 2 from the magnetic tape 1 is supplied to an ATF circuit 4 and a low-pass filter 5 through a reproduction amplifier 3. An ATF (tracking) error signal from the ATF circuit 4 is supplied to a microcomputer 7 through an A / D conversion circuit 6. Low-pass filter 5
A signal corresponding to the envelope of the RF (reproduction) signal from the microcomputer 7 is supplied to the microcomputer 7 through the A / D conversion circuit 8.

Reference numeral 9 denotes a capstan for transferring the magnetic tape 1. The FG detection sensor 1 of this capstan 9
The signal from 0 is supplied to the microcomputer 7 through the FG amplifier 11. Then, the control signal calculated by the microcomputer 7 is supplied to the drive circuit 12, and the drive of the capstan 9 is controlled.

FIG. 2 is a functional block diagram for explaining processing in the microcomputer 7. In this figure, the FG signal from the FG amplifier 11 is supplied to an FG interval measuring unit 70, and the measured FG interval is supplied to a capstan speed converting unit 71. The signal from the conversion unit 71 is supplied to the subtraction unit 72, where the speed target value 73 is subtracted, and the speed error signal is calculated. This error signal is sent to the gain adjustment unit 7 through the servo operation unit 74.
5 is supplied.

The ATF error signal from the A / D conversion circuit 6 is supplied to a subtraction unit 76, and an ATF error target value 77
Is subtracted, and a tracking error signal is calculated. This error signal is supplied to the gain adjustment unit 79 through the servo operation unit 78. Then, these gain adjustment units 75,
The speed error signal from 79 and the tracking error signal are added by the adder 80 to form a control output signal.

Further, the control output signal is supplied to the PWM circuit 8
1. Motor driver 83 through low-pass filter 82
To control the capstan motor (not shown). The PWM circuit 81, the low-pass filter 8
2. A part of the circuit such as the motor driver 83 can be provided in a chip as a peripheral circuit of the microcomputer 7.

In this apparatus, the processing in the microcomputer 7 is performed as shown in the flowchart of FIG. In this figure, this flowchart is executed in the FG interrupt processing in a state where the capstan is activated.

That is, it is determined in step [1] whether or not there is an ATF servo command. If there is no command such as when starting, the speed reference (target value) is set to, for example, 0.8 times speed in step [2]. Next, speed servo processing is performed in step [3]. Further, at step [4], it is determined whether or not the speed error is within the range.

If the value is within the range in step [4], it is determined in step [5] whether or not ATF error sampling has been performed. Further, when sampling is performed in step [5], 0 is described later in step [6].
It is determined whether the cross detection flag is “1”. And 0
When the cross detection flag is "0", 1 is set in step [7].
A comparison with the data before the sample is performed.

If the value has changed to a positive value in step [7], the absolute value is compared in step [8]. If the absolute value comparison is positive,

In [9], the counter is incremented, and in step [1]
0], the 0 cross detection flag is set to “1”. In step [11], it is determined whether the count value of the counter is "2".

If the count value is "2" in step [11], the value two samples before is subtracted from the current sample value in step [12], and the gain calculation described later is performed in step [13]. In step [14], a reference is calculated at the time of a track shift described later. In step [15], it is determined whether or not the count value of the counter is an arbitrary value "A". If it is "A", an ATF servo command is issued in step [16] and the operation is terminated.

If the value is out of the range in step [4], if the value has changed to minus in step [7], and if the comparison of the absolute value is minus in step [8], step [17] Then, the count value of the above-mentioned counter is set to "0" and the operation is completed. Step [5]
If the sampling is not performed in the step (1), the operation is terminated.

Further, if the 0 cross detection flag is "1" in step [6], step

Proceed to [9]. If the count value is not "2" in step [11], the process directly proceeds to step [15]. If the count value of the counter is not "A" in step [15], the operation is terminated as it is.

On the other hand, when the ATF servo command is issued in step [16], A is executed in step [1].
It is determined that there is a TF servo command. At this time, the speed reference (target value) is set to 1 × speed in step [18]. Next, speed servo processing is performed in step [19]. Further, in step [20], the speed servo gain is adjusted.

In step [21], it is determined whether ATF error sampling has been performed. When sampling is performed in step [21], ATF servo processing is performed in step [22]. In step [23], the ATF servo gain is adjusted.

In step [24], the speed servo and A
The value of the TF servo is added, and at step [25] PWM
Is converted. This PWM-converted signal corresponds to step [2]
6], and the operation is terminated. Step [2
If sampling is not performed in [1], the previous value is directly subjected to PWM conversion in step [25].

Therefore, in this apparatus, the tape transfer speed at the time of start-up is, for example, as shown in FIG.
Doubled speed. At this time, the envelope of the RF signal is as shown in B of the same figure, and the ATF error signal is as shown in C of the same figure. Here, if the tape transfer speed is kept at 0.8 times the speed, the change in tracking is, for example, D in FIG.
As shown in the figure, the change is repeated every 10 tracks of reproduction, and the envelope of the RF signal and the AT
The F error signal is as shown by a broken line in the figure.

On the other hand, when the speed servo is stabilized at 0.8 times speed at time t ₁ in the figure, the next ATF error signal becomes 0.
Time t ₂ of cross detection flag is detected. From here, the counter starts incrementing, and the count value becomes “A”.
Target value of the velocity servo is in the normal speed at the time t ₃ when the. Then, the time t ₄ of the 0 cross of the next ATF error signal
The speed servo and tracking servo at 1 × speed are executed.

That is, in this device, the tracking is correctly performed at the time t ₄ of the 0 cross of the ATF error signal, and the tracking servo without malfunction is performed by starting the speed servo and the tracking servo at the time t _4. be able to. The above-mentioned count value “A” is arbitrarily determined according to the time difference between the time points t ₃ and t ₄ of the target device.

Thus, according to the above-described apparatus, it is possible to equalize the time until the correct tracking state is obtained at the time of activation or the like and a reproduced image is obtained.

In the above-described apparatus, the tape transfer speed at the time of startup is not limited to 0.8 times speed. Here, the waveform of the ATF error signal and the like becomes more accurate as the double speed ratio is closer to the normal speed. For example, when the double speed ratio is 0.9.times., The above-described change in tracking is repeated every 20 tracks during reproduction. As a result, the time required to detect the zero cross is doubled. On the other hand, by analyzing the waveform of the ATF error signal and the like by the microcomputer 7, there is a possibility that the waveform can be detected even at about 0.6 times speed.

Further, in the above-described apparatus, the detection of the time point t ₂ at which the tracking is correctly performed is performed by detecting the time point at which the envelope of the RF signal reaches the maximum value, regardless of the detection of the zero cross of the ATF error signal. You may make it.

Further, by subtracting the value two samples before from the current sample value in step [12] of the above-described flowchart, for example, as shown on the left side of FIG.
The value of E 'is obtained. On the other hand, assuming that the inclination of ΔE as shown on the right side of the figure is ideal, K = kΔE / ΔE ′ (k is a fixed gain constant) is calculated in the above step [13], and this value is calculated. For example, by adjusting the gain of the gain adjusting unit 79 using the above, it is possible to absorb variations in the gain of the servo loop.

For example, when the tape is transported at 0.8 times speed, the tracking is shifted by (1-8 / 10 = 0.2) tracks between two samples of the ATF error signal. Since the change in error at that time is ΔE ′, the error voltage when X% track shift is performed is ΔE ′ × (1 track / 0.2 track) × (X% / 1
00%). This value is calculated in the above step [14], and using this value, tracking servo can be performed in an arbitrary track-shifted state.

[0034]

According to the present invention, it is possible to equalize the time required for obtaining a reproduced image by obtaining a correct tracking state at the time of activation or the like.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an example of a main part of a playback device according to the present invention.

FIG. 2 is a diagram for explaining this.

FIG. 3 is a flowchart for the explanation.

FIG. 4 is a time chart for the explanation.

FIG. 5 is a diagram for the explanation.

FIG. 6 is a diagram for explaining a tracking control method for a narrow recording track previously proposed by the present applicant.

[Explanation of symbols]

 Reference Signs List 1 magnetic tape 2 head 3 reproducing amplifier 4 ATF circuit 5 low-pass filter 6, 8 A / D conversion circuit 7 microcomputer 9 capstan for transferring magnetic tape 1 10 FG detection sensor 11 FG amplifier 12 drive circuit

Claims (3)

(57) [Claims] 1. A pilot signal recorded on a track.
AFT playback device that performs tracking based on a signal
In the start , the speed control is performed so that the tape transfer speed at the start is less than the standard tape transfer speed, the first zero-cross detection in the tracking error signal in the reproduction signal at that time is performed, and a predetermined time from the detection point is detected. A playback device wherein the tracking control is started by performing speed control to a standard tape transfer speed at a point in time when elapses. 2. A pilot signal recorded on a track.
AFT playback device that performs tracking based on a signal
, The speed control is performed so that the tape transfer speed at startup is less than the standard tape transfer speed, the first maximum value in the envelope of the reproduction signal at that time is detected, and a predetermined time has elapsed since the detection. A reproducing apparatus characterized in that the speed control is performed to a standard tape transfer speed and tracking control is started at the point of time. 3. A recording medium in which one field is divided into a plurality of tracks for recording and a pilot signal is recorded on one track for every four tracks, and the pilot signal is reproduced to perform tracking control. 3. A reproducing apparatus according to claim 1, wherein the tracking control according to claim 1 or 2 is performed.