JPH0289244A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain highly accurate tracking control by an inexpensive and simple constitution by deciding the acceleration/deceleration of a magnetic tape and a reproducing RF signal level and controlling the traveling speed of a magnetic tape on the basis of both the decided results. CONSTITUTION:When a reproducing button PB is depressed and a VTR is set up to a reproducing mode, a CPU 21 in a servo control circuit 20 decides whether the magnetic tape is in an accelerating state or not, i.e. whether the tracking control output CXn of a current field in the CPU 21 is positive or not, on the basis of a PG pulse generated from a signal generator 4. Then, whether the reproducing RF signal level of the current field is increased or not as compared to that of the preceding field is decided, i.e. the sizes of the outputs of an envelope detector 12 between the current field and the preceding field are compared with each other. The traveling speed of the magnetic tape is controlled on the basis of these decided results. Consequently, highly accurate tracking control can be attained by the inexpensive and simple constitution without using a specific recording signal for control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a helical scan type magnetic recording and reproducing device suitable for tracking control.

C. Summary of the Invention] The present invention provides a helical scan type magnetic recording and reproducing device that discriminates between acceleration/deceleration of the magnetic tape and increase/decrease in the reproduction RF signal level, and increases/decreases the running speed of the magnetic tape based on the results of both determinations. By doing so, it is possible to perform highly accurate tracking control with a low-cost and simple configuration without using any special recording signals.

[Conventional technology]

As is well known, in an 8 mm video type VTR, tracking control of the TF type is performed using pilot signals of four frequencies.

The pilot frequency is for example f + = 6.5 fu, 102.5 k) Iz
fz=7.5fu=, 119.0kHzfs=10
．． 5 fH” = 165.2kHzfa = 9.5f
H”= 148.7k) Iz, and the fifth
As shown in the figure, recording is repeated in sequence for every four tracks so that the frequency difference between both adjacent tracks becomes if□3f++.

During playback, tracking errors are detected by comparing the levels of the frequency difference component (lfo 3f□) between the crosstalk components from both adjacent trunks and the local pilot signal in the reverse order to that during recording.

In addition, in other conventional helical scan VTRs,
A tracking control signal having a repetition frequency of 3 QHz, a so-called CTL signal, is recorded on a dedicated track provided at the edge of the magnetic tape, and tracking control is performed based on the reproduced CTL signal.

[Problem to be solved by the invention]

The above-mentioned ATF method has a problem in that the circuit configuration becomes complicated due to switching of the pilot frequency for each track, level comparison of frequency difference components, etc., and the cost increases.

Furthermore, the CTL method requires a pulse generator for control signals and a recording/reproducing head, which increases costs. Furthermore, there is a problem in that a dedicated track is required on the magnetic tape, which hinders improvement in recording density.

To solve this problem, various tracking control methods have already been proposed that do not require recording special signals for control.

One of them is a method of changing the reproduced RF signal level. In this method, a reproducing magnetic head is attached to a rotating drum via, for example, a piezoelectric bimorph, and a control signal of several hundred hertz is applied to the bimorph to cause the reproducing magnetic head to vibrate (wobble) in the width direction of the track. By changing the level of the RF signal, the amount and direction of tracking deviation can be determined from both this change and the control signal.

However, in the RF signal level change method, in order to vibrate the reproducing magnetic head, a voltage -
This method requires a mechanical transducer and a drive circuit, resulting in a complicated configuration and increased cost.

In order to reduce costs, it is conceivable to change the rotational speed of the capstan motor vibrationally without using a piezoelectric element, but this would result in the tape running speed not being constant and the time axis of the reproduced video signal fluctuating. The problem arises that the

In view of the above, an object of the present invention is to provide a magnetic recording/reproducing device that is capable of high-precision tracking control with a low-cost, simple configuration without using special recording signals for control.

[Means to solve the problem]

The present invention provides a tape acceleration determination method for determining the acceleration/deceleration state of a magnetic tape in a magnetic recording/reproducing apparatus in which a recording trunk formed at an angle on a magnetic tape is scanned by a rotating magnetic head to obtain a reproduction signal. and signal level determining means for determining an increase or decrease in the level of the reproduced high frequency signal output from the rotating magnetic head, and the running speed of the magnetic tape is determined based on the determined outputs of the signal level determining means and the tape acceleration determining means. This is a magnetic recording and reproducing device that increases and decreases.

[Effect]

According to this configuration, high-precision tracking control can be performed at low cost without using a special recording signal.

〔Example〕

Below is the 1st rI! An embodiment in which a magnetic recording/reproducing apparatus according to the present invention is applied to a VTR will be described with reference to FIGS.

First, the basic principle of the present invention will be explained with reference to FIGS. 3 and 4.

In this embodiment, the width 'vVh of the magnetic head is set equal to the track width Wtk, and the relative position between the magnetic head and the track is as shown in FIG. A state in which the track Tkυ is partially scanned, ■ A state in which only tracks with different azimuths on the upstream side of the target track Tko are scanned, ■ A state in which the upstream side of the target track Tko is partially scanned, ■ A state in which the target track is scanned without tracking deviation. A state in which the entirety of the target track Tko is scanned, ■ A state in which the downstream side of the target track Tko is partially scanned, ■ A state in which only the tracks downstream of the target track Tko with a different azimuth are scanned, ■ A state in which the downstream side of the target track Tko and the same azimuth are scanned. This is represented by a state in which the side track Tkl is partially scanned.

The level of the reproduced RF signal from the magnetic head in each state shown in FIG. 3 changes as shown in FIG. 4, with tracking deviation toward the upstream side being taken as a positive direction.

In the RF signal level detection method, the running speed of the magnetic tape is adjusted so that the detection level reaches the maximum state (■).

That is, when the tracking deviates to the upstream side as in the state (2), the running of the magnetic tape is decelerated as shown by the arrow Vt- in FIG. In addition, if the tracking deviates to the downstream side as in the state shown in ■, the arrow Vt in Fig.
As shown by 10, the running of the magnetic tape is accelerated.

The configuration of one embodiment of the present invention is shown in FIG.

In FIG. 1, a pair of magnetic heads (18) and (1B
) is attached to the rotating drum (2), and a directly connected motor (
3). A rotary phase pulse generator (so-called PG) (4) and a frequency signal generator (so-called FG) (5) are attached to this motor (3).

The running speed of the magnetic tape T wound around the rotating drum (2) within a predetermined range is controlled by a capstan (6).

A motor (7) is directly connected to this capstan (6), and an FG (8) is attached thereto.

The reproduced RF signal from the magnetic head (LA), (1B) is sent to the envelope detector (12) via the amplifier (11).
supplied to

(20) is a digital servo control circuit (microcomputer), and its central processing unit (CPU) (21
) is supplied with the detection output EV of the envelope detector (12) via the AD converter (22). Time measurement circuit (
The output of P G (4) and F C (5) attached to the rotating drum (2) is supplied to the timer (23), and the output of the timer (23) is supplied to the CPU (21). The tracking control output CX of the CPU (21) is D-
It is supplied to the capstan motor (7) via the converter (24) and the drive width converter (9).

Note that the output of the capstan FG (8) is supplied to the servo control circuit (20) to perform normal capstan servo control, and the output of the servo control circuit (20) is supplied to the drum motor (3). Then, normal drum servo control is performed.

The operation of the embodiment of FIG. 1 is as follows.

When the playback button PB is operated and the VTR enters the playback mode, the CPU (21) of the servo control circuit (20) operates, for example, once every field, based on the PG pulse from the signal generator (4). As shown in FIG. 2, it is determined whether the magnetic tape is in an accelerated state, that is, whether the tracking control output CXn of the current field of the CPU (21) is positive (step 0).

Next, it is determined whether the reproduced RF signal level of the current field has increased compared to that of the previous field, that is, the output E of the envelope detector (12) of the current field and the previous field.
The magnitudes of Vn and E Vn- are compared (step C
and 9).

In this embodiment, the tracking state is classified into the following four types according to the determination results of steps ◎ to ◎ described above, and a tracking control command is given according to each state.

When the tape is accelerating and the RF signal level is increasing, the head is in the tracking state as shown in Figure 3 (■) and is being controlled in a stable direction, so it will continue to be controlled in the same direction. A tracking control command of positive polarity CXn+>0 for acceleration is issued so that the acceleration is achieved (step 2).

If the tape is accelerating and the RF signal level is decreasing, the head is in the tracking jaw as shown in Figure 3 above, and is controlled in the opposite direction to the stable direction. A tracking control command of negative polarity CXn++ < 0 for deceleration is issued so as to be controlled as follows (step 0).

If the tape is decelerating and the RF signal level is increasing, the head is in the tracking state as shown in Figure 3 (■) and is being controlled in a stable direction, so it will continue to be controlled in the same direction. A tracking control command of negative polarity CXn+1 < Q for deceleration is issued (step [phase]).

If the tape is decelerating and the RF signal level is decreasing, the head is in the tracking state as shown in Figure 3 (■) above, and is being controlled in the opposite direction to the stable direction. In order to control the acceleration, a positive tracking control command CXn+, > 0 for acceleration is issued (step ■).

An error signal is output in response to each of the control commands in steps ① to ① (step @).

In this manner, in this embodiment, tracking control can be performed using the reproduced RF signal detection method with a low-cost and simple configuration without wobbling of the magnetic head.

In the above embodiment, only the polarity of the control command Cx was explained, but the maximum value of the reproduced RF signal stored in advance is used as a reference, and according to the difference between this reference value and the current RF signal level,
The amplitude of the control command may be determined, or
For example, +〇, IV.

The polarity may be made to differ with a constant amplitude, such as -0 and IV.

Further, in the above embodiment, a magnetic head with a width equal to the track width was used, but when using a magnetic head wider than the track width, a known tracking control method (for example, Japanese Patent Application Laid-Open No. Showa 62-22
No. 2459) may be used in combination.

Although the present invention has been described above for a case where it is applied to a VRT, it can be similarly applied to a helical scan type digital audio tape recorder.

〔Effect of the invention〕

As described in detail above, according to the present invention, acceleration/deceleration of the magnetic tape and increase/decrease in the reproduced RF signal level are determined respectively, and the running speed of the magnetic tape is increased/decreased based on the results of both determinations. A helical skimmer type magnetic recording/reproducing device capable of highly accurate tracking control can be obtained with a low cost and simple configuration without using a special recording signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of a magnetic recording/reproducing apparatus according to the present invention, FIG. 2 is a flow chart for explaining the operation of an embodiment of the present invention, and FIGS. A diagram for explaining the basic principle of the invention, and FIG. 5 is a diagram for explaining the conventional tracking method. (IA) and (IB) are magnetic heads, (4) is a rotary phase signal generator (PG), (7) is a capstan motor, (12) is an envelope detector, and (20) is a digital servo control circuit ( microcomputer), (21) is the CPU
, (23) is a time measurement circuit. Iso 1 Shihe・Nohito Tsui・Nori no Tenmoku Taoi Tate 1 [@3 Figure 5 Moetaka tk Figure 4

Claims (1)

[Scope of Claims] A magnetic recording/reproducing device that obtains a reproduction signal by scanning a recording track formed at an angle on a magnetic tape with a rotating magnetic head, wherein the acceleration/deceleration state of the magnetic tape is determined. tape acceleration determining means; and signal level determining means for determining an increase or decrease in the level of the reproduced high-frequency signal output from the rotary magnetic head; A magnetic recording and reproducing device characterized in that the running speed of a magnetic tape is increased or decreased.