JP2626058B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape wound around a rotating cylinder to which a magnetic head is attached, to make sliding contact between the magnetic head and the magnetic tape, and to provide a predetermined signal such as a video signal. The present invention relates to a magnetic recording and reproducing apparatus such as a video tape recorder which records and reproduces an information signal.

2. Description of the Related Art Conventional technology will be described. In FIG. 2, when the magnetic head 1 is traveling on the track pattern state 1 on the magnetic tape 6 in the on-track state, the control head 2 responds to the head switching pulse output from the head switching pulse detecting head 3. It is assumed that the phase time of the control signal, which is the output of, is t ₁ . When the track pattern on the magnetic tape 6 changes to, for example, state 2 due to the expansion and contraction of the magnetic tape 6 due to the influence of humidity, tape tension, and the like, the magnetic head 1 moves to the track pattern state 2 Mistracking will occur. At this time, the head switching pulse detection head 3
The phase time of the control signal output from the control head 2 with respect to a head switching pulse is output, for example by changing from t ₁ as shown in FIG. 2 to t _2, the magnetic head 1 again the magnetic tape 6 above On the track pattern state 2 in the on-tracking state. The relationship between the time t ₁ and t ₂ when the phase time with the time between t _F and the control signal and a head switching signal required to travel on a track which is shift amount l and head of the track is constant When the pitch distance between adjacent tracks with each other and l _0, is given by _{l / l 0 = (t 2} -t 1) / t F and the relationship.

Hereinafter, description will be made with reference to FIG. In a state where the magnetic head is on-track as in the track [state 1] in FIG. 3, the signal becomes maximum. At this time, the phase difference between the head switching signal and the control signal is t ₁ as shown in FIG. And Next, [State 2] in FIG.
If the control signal is shifted in the direction C in the figure with respect to the head switching signal, it occurs when the on-track [state 3] in FIG. 3 is generated by shifting the control signal in the direction d in the figure. I do. At this time, in the on-tracking [state 2] and the on-track [state 3], the output of the magnetic head is lower than that in the on-tracking [state 1] because the magnetic head mistracks on the track. Therefore, by changing the phase time of the control signal with respect to the head switching signal so that the magnetic head output is maximized even when the track state changes, the third
The track state of the magnetic head changes in the direction a or b in the figure, and the on-tracking state can be maintained.

Hereinafter, a conventional example of an auto-tracking control circuit used to keep the magnetic head in an on-track state will be described with reference to FIG. The head output from the rotating magnetic head 1 is detected by a magnetic head output detection circuit 7 and the signal is input to an auto tracking control circuit 8. The output of the control head 2 is input to a control signal detection circuit 9, and the output of the cylinder head switching pulse detection head 3 is input to a head switching pulse detection circuit 10. The output of the control signal detection circuit 9 and the output of the head switching pulse detection circuit 10 are input to the capstan motor control circuit 11. At this time, in the capstan motor control circuit 11, the auto tracking control circuit 8 changes the phase of the control signal with respect to the head switching pulse so that the output of the magnetic head output detection circuit 7 becomes maximum. 11
Output a control signal to the controller. As described above, the magnetic head 1 can travel on the track pattern on the tape in the on-tracking state.

The problem to be solved by the invention will be described below with reference to FIGS. 3 and 4.

Now, in the track pattern state 1, the magnetic head 1
Is in an on-track state. If the track pattern changes from this state to the track pattern state 2, mistracking by the magnetic head 1 occurs, and the auto-tracking control circuit 8 attempts to shift the magnetic head 1 in the a or b direction. The circuit 8 itself cannot know in advance whether the track has shifted to a or b. For the above reason, when performing auto-tracking, the auto-tracking control circuit 8 moves the magnetic head 1 in the a and b directions, moves the track shift direction from the change in the head output, and changes the track shift direction from the change in the head output. There is a need to identify. At this time, for example, even if the track itself of the tape 6 is shifted in the direction b, the magnetic head 1
May move in the direction a, which is the opposite direction. In this case, problems such as a decrease in head output and deterioration of wow and flutter such as an audio signal occur until auto-tracking is completed.

Means for Solving the Problems In order to solve this problem, a magnetic recording / reproducing apparatus of the present invention includes a rotating cylinder having a magnetic head, a magnetic head output detection circuit, and a FG output from a FG head of a capstan motor. A capstan FG count circuit for counting signals, a control signal detection circuit for detecting a control signal output from the control head, and an output signal of the magnetic head output detection circuit and the capstan FG count circuit as input signals, An auto-tracking control circuit for detecting a tracking shift amount and a tracking shift direction of a magnetic tape with respect to a head to perform tracking control of a magnetic head; a head switching pulse detection circuit for detecting a signal from a cylinder head switching pulse detection head; signal Those equipped with a capstan motor control circuit for an output and an input signal the output of the head switching pulse detection circuit of the filter circuit.

Operation With this configuration, the auto-tracking control circuit receives the output signals of the magnetic head output detection circuit and the capstan FG count circuit as input signals, detects the tracking shift amount and the tracking shift direction of the magnetic tape with respect to the magnetic head, and detects the magnetic head. Acts to perform tracking control.

Next, examples of the present invention will be described. Hereinafter, the first
An embodiment of an auto-tracking control circuit used to keep the magnetic head in an on-track state will be described with reference to the drawings.

When the magnetic tape does not expand or contract, the magnetic head can run on the track pattern on the tape in an on-tracking state. This state is represented by track pattern state 1 in FIG. Length from the time control head to the track center is L _1, when the control signal pitch at this time was that the X ₁ of FIG. 2, the output f ₁ of the first view of the capstan FG counter circuit 12 Is stored in the auto tracking control circuit 8. Further, the phase time of the control signal output from the control head 2 with respect to the head switching pulse which is output from the head switching pulse detection head 3 and t _1. The L ₁ and x ₁ is a design value of the magnetic recording and reproducing apparatus.

Thereafter, tape length by effect magnetic tape, such as humidity and the tape tension is reduced to L _2, tracks and displaced in the direction of the track pattern state 2 of FIG. 2. At this time, the control signal pitch is reduced to x _2. If the output of this time a capstan FG count circuit 12 and f _2, the following equation holds.

_{L 2 / L 1 = x 2} / x 1 = f 2 / f 1 (1) The relationship between the phase time t ₁ and t ₂ of the control signal for the head switching pulse of the second figure, (L ₁ -L ₂ ) Sin θ = (t ₂ −t ₁ ) * l ₀ / t _F (2) From the equations (1) and (2), t ₂ −t ₁ = L ₁ (1−f ₂ / f ₁ ) sin θ * t _F / l ₀ (3) From the above three relations, when the track pattern changes from the track pattern state 1 to the track pattern state 2 as shown in FIG. 2, the auto tracking control circuit 8 in FIG. know track deviation amount and track deviation direction from an output f ₂ of the FG counter circuit 12 of the output f ₁ and the track pattern state 2 of circuit 12, controlled to change the phase time t ₁ of the control signal for the head switching pulses to t ₂ The signal is output to the capstan control circuit 11. As a result, the magnetic head 1 can travel on the track pattern state 2 on the tape 6 in FIG. 2 in the on-tracking state.

At this time, for example, when the track itself of the tape 6 is shifted in the direction b, the magnetic head 1 does not move in the direction a which is the opposite direction. As a result, a decrease in head output and the generation of wow and flutter such as an audio signal can be suppressed to a minimum until the auto tracking is completed.

As described above, according to the present invention, a capstan FG count circuit for counting the FG signal output from the FG head 4 of the capstan motor is newly provided, and the magnetic head output detection circuit and the capstan Using the output signal of the FG count circuit as an input signal, the amount of tracking deviation of the magnetic tape with respect to the magnetic head and the direction of the tracking deviation are detected, and tracking control of the magnetic head is performed. And the generation of wow and flutter such as audio signals can be minimized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an automatic tracking control circuit of a magnetic recording / reproducing apparatus according to an embodiment of the present invention. FIGS. 2 and 3 show states when a magnetic head is running on a track pattern on a magnetic tape. FIG. 4 is a block diagram showing an automatic tracking control circuit of a conventional magnetic recording and reproducing apparatus. 1 ... rotating magnetic head, 2 ... control head, 3
...... Head switching pulse detection head, 4 ... Capstan motor FG head, 7 ... Rotary magnetic head detection circuit, 8 ... Auto tracking control circuit, 9 ... Control signal detection circuit, 10 ... Head switching pulse detection circuit , 11 ... Capstan motor control circuit, 12 ... Capstan FG count circuit.

Claims (1)

(57) [Claims] 1. A rotary cylinder having a magnetic head, a magnetic head output detection circuit, and a capstan for counting an FG signal output from an FG head of a capstan motor.
An FG count circuit, a control signal detection circuit for detecting a control signal output from the control head, and an output signal of the magnetic head output detection circuit and the capstan FG count circuit as input signals to track a magnetic tape with respect to a magnetic head. An auto-tracking control circuit for detecting a deviation amount and a tracking deviation direction to perform tracking control of the magnetic head; a head switching pulse detection circuit for detecting a signal from a cylinder head switching pulse detection head; an output of the control signal detection circuit; A magnetic recording / reproducing apparatus comprising: a capstan motor control circuit that receives an output of the head switching pulse detection circuit and an output of the auto tracking control circuit as input signals.