JPH0612584B2 - Rotating head type magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control circuit of a helical scan type magnetic recording / reproducing apparatus having a rotary head, and particularly to a recording / reproducing apparatus suitable for tracking control during variable speed reproduction. It is about.

[Background of the Invention]

The rotary head type magnetic recording / reproducing apparatus is widely used as a consumer device such as a video tape recorder and an audio PCM recorder. The rotary head type magnetic recording / reproducing apparatus forms and records an oblique track on a magnetic tape as a recording medium. Further, in order to increase the recording density, no guard band is provided between the adjacent tracks, and crosstalk from the adjacent tracks at the time of reproduction has two recording / reproducing heads, and the azimuth angle of the heads is made different between the adjacent tracks. It is reduced by loss.

In such a rotary head type magnetic recording / reproducing apparatus, the reproducing head needs to accurately trace the track recorded on the magnetic tape, and the tracking control for controlling it plays an important role.

Conventionally, tracking control of a video tape recorder is performed by using a dedicated track for recording a control signal for control. This system does not interfere with the image signal, which is the main signal, but it requires a head for tracking control and a dedicated area on the magnetic tape, and is different from the track on which the main signal is actually recorded. However, there is a drawback that it is not suitable for high-density recording / reproducing in terms of mounting accuracy of heads and compatibility.

Therefore, there is a method of performing tracking control by dividing the area of the recording track into an area in which a main signal of an image signal or a PCM signal is recorded and an area in which a tracking control pilot signal is recorded. The signal shape on the magnetic tape recorded by this method is shown in FIG.

In FIG. 1, 1 is a magnetic tape, 2A and 2B are heads, and A ₀ and B
₀ ... A ₂ and B ₂ are tracks formed on the magnetic tape 1,
A ₀ , A ₁ and A ₂ are heads 2A, and B ₀ , B ₁ and B ₂ are tracks with different azimuth angles recorded and reproduced by the head 2B. Also P
The area marked CM is the recording area of the PCM signal which is the main signal, and the area marked ATF is the area in which the tracking control pilot signal is recorded. Tracking control for controlling the head to accurately trace the track of the tape recording pattern shown in FIG. 1 is performed by the following operation. Head 2A is track A ₁
Is traced to the left, the level of the pilot signal in the ATF area of the track B ₁ is detected, and whether the head is traced to the right is determined by the pilot in the ATF area of the track B _0. Tracking control is performed by detecting the signal level and controlling the tape feeding speed in accordance with the detection level.

With such a tracking control method by dividing the track area, even during variable speed reproduction such as double speed or triple speed,
There is a demand for a tracking control circuit that provides a desired head locus and a stable reproduction signal.

[Object of the Invention] An object of the present invention is to obtain a desired head locus during variable speed reproduction such as 2 × speed or 3 × speed in a circuit for performing tracking control by dividing a track area and recording / reproducing a pilot signal. To provide a rotary head type magnetic recording / reproducing apparatus.

[Outline of Invention]

The track area is divided so that the area for recording the pilot signal is divided into two areas, and means for holding the tracking error signals in the two areas is provided, and the tracking result is calculated by adding these values. The desired head locus during variable speed reproduction is obtained by controlling.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows an example of arrangement of pilot signals for tracking control. For recording and reproduction, two heads with different azimuth angles (2
A, 2B) and track
A ₀ , A ₁ , and A ₂ are recorded by the head 2A, and the pilot frequency is ₁ with a small azimuth loss effect. The tracks B ₀ , B ₁ , and B ₂ are recorded by the head 2B and have pilot frequencies ₁ and ₂ ( ₁ ≠ ₂ ).

FIG. 3 shows a circuit of an embodiment of the tracking control of the present invention in the pilot signal arrangement of FIG. 3 in Figure 3
Is an input terminal to which a signal corresponding to the cylinder rotation frequency of the rotary head is applied. When the level is "1", the head 2A contacts the tape, and when the level is "0", the head 2B contacts.
Reference numeral 4 is an input terminal for a reproduction signal from the head, 5 is a reproduction amplifier, 6 is a low-pass filter (referred to as LPF) that passes the frequencies ₁ and ₂ , and 7 is an oscillation frequency controlled by a signal applied to the terminal 3. that an oscillator, the level of the terminal 3 is oscillated _a time when _2, "0" level of "1". A frequency conversion circuit 8 multiplies the output signal of the oscillator 7 and the signal of the LPF 6 and outputs the difference frequency. 10 the difference frequency from the frequency converting circuit 8 ₍₁ - ₂₎ (referred to as BPF) band-pass filter for detecting a component of, 11 difference frequency (
₁ - ₂₎ packaging Raku line detection circuit for detecting the hull pleasure line component,
12,13,16,17 are sample and hold circuits that sample and hold data, 15 and 18 are adder circuits, and 19 is a switch.
The 9A side is selected during normal tracking, and the 19B side is selected during variable speed playback. Reference numeral 20 is a tracking error signal output terminal, and 9 is a reference timing detection circuit for detecting a timing reference signal, which detects the first rising edge of the reproduction signal. Reference numeral 14 is a timing circuit which gives sampling and holding circuits 12, 13, 16 and 17 timing sampling and holding. Third
In the figure, the operation during normal tracking will be described with reference to the timing chart of FIG. The reference numeral attached to the left side of FIG. 4 corresponds to the reference numeral attached to FIG.
The signal of each code is shown. The reproduction signal is applied to the terminal 4, and the signal shown in FIG. 4 is obtained via the reproduction amplifier 5 and the LPF 6. FIG. 4 shows the tape pattern of FIG. 2, which is a signal obtained when the head 2A traces the track A1 and then the head 2B traces the track B1. Head 2A, the width of 2B is assumed to be wide and 1.5 times the track pitch, first from the track B _1
1 signal appears, then ₁ signal of own track A ₁ ,
Then ₁ signal from the track B ₀ are detected, ₁ signal from the track B _1, together with the _first signal from the track B ₂ appears, from the track A ₁ of its ₂ signal appears as shown in FIG. 4 6. When the head 2A traces the track A ₁ and reproduces the pilot signals ₁ and ₂ for tracking control, the head 2B having a different azimuth angle then traces the track B ₁ and is shown in FIG. 4 similarly to the head 2A. A signal like this appears. On the other hand, the signal shown in FIG. 4 corresponding to the cylinder speed is applied to the terminal 3. Therefore,
The oscillation frequency of the oscillator 7 is, as shown in FIG.
₁ and ₂ are switched alternately. In the frequency converting circuit 8 multiplies the signal of the fourth 6 and 7, the difference frequency ₁ - generating a _2. In BPF 10, the difference frequency ₁ - ₂ component alone is taken out and added to packaging Raku line detection circuit 11. Therefore, the output of the envelope detection circuit 11 has the waveform shown in FIG. Further, the output signal of the LPF 6 is added to the reference timing detection circuit, and the first rising edge of the reproduction signal is used as the reference pulse. In addition to the timing circuit 14, the sample hold circuits 12 and 13 are connected to the sample hold circuits shown in FIGS. Add a pulse. Therefore, if the pilot signal level from the adjacent track on the left side is held in the sample hold circuit 12 and the head 2A shifts to the left side and traces (tracking error in the plus direction), the level becomes high. Further, the sample and hold circuit 13 holds the pilot signal level from the adjacent track on the right side, and if the head 2A shifts to the right side and traces (tracking error in the minus direction), the level becomes high. Such an operation is similar for heads 2B having different azimuth angles. If the adder circuit 15 adds the sample-hold circuits 12 and 13 with the polarities shown in FIG. 3, the tracking error shown in FIG. Signal characteristics are obtained. Therefore, during normal tracking control operation, by connecting the switch 19 to the 19A side, an error signal appears at the output terminal 20 and tracking control can be performed.

Next, the circuit operation of FIG. 3 during variable speed reproduction will be described. FIG. 6 shows an ideal head locus during double speed reproduction. 2A and 2B are tracks traced by the centers of the heads 2A and 2B. During variable speed reproduction, the cylinder rotation speed is not changed and the tape feeding speed is doubled, so that the track of the head does not coincide with the track direction. When the area in which the PCM signal of the main signal is recorded at the tape winding angle of the cylinder is 60 °, the tracking shift amounts in FIG. 6 are θ ₁ = 60 ° and θ ₂ = 120 °. According to the locus of FIG. 6, the head 2A moves toward the track A.
_{With 0} , the head 2B can reproduce the PCM signal of the track B ₁ .

The circuit operation of FIG. 3 for obtaining the head locus of FIG.
This will be described with reference to the timing chart in the figure. The circuit of FIG.
Since the same operation as in normal tracking is performed during variable speed reproduction, as shown in FIG. 7, by the sample pulses 12p and 13p applied to the sample hold circuits 12 and 13,
An error signal corresponding to the tracking error shown in FIG. 6 appears at the output of the adder circuit 15. When the head 2A passes through the area (first area) on the left side of FIG. 6, a voltage corresponding to the tracking error θ ₁ appears in the adding circuit 15. On the other hand, head 2B
6 passes through the area (second area) on the right side of FIG. 6, a voltage corresponding to the tracking error −θ ₁ appears in the adding circuit 15.
The sample-and-hold circuits 16 and 17 hold the tracking error signals at the above-mentioned two points, and sample-and-hold is performed by the pulses shown in FIGS.

At the time of the head locus shown in FIG. 6, the voltages held in the sample and hold circuits 16 and 17 are voltages of the same level with their polarities reversed. Therefore, the voltage of 0 level is output to the output of the adder circuit 18 as an error signal. Also, if the head locus deviates above the line shown in FIG. 6, the head 2A
, The tracking error θ ′
_A voltage corresponding to _A (θ ′ _A > θ ₁ ) appears in the adder circuit 15,
When the head 2B passes through the second region, the tracking error _{θ 'B (θ'B>} -θ 1) voltage corresponding to the addition circuit 15
Appear in. Therefore, the output of the adder circuit 18 in which the values of the sample hold circuits 16 and 17 holding these are added becomes a negative voltage level, and the level fluctuates according to the tracking error. On the other hand, conversely to the above, when the head locus deviates below the line shown in FIG. 6, the output of the adder circuit 18 becomes a positive voltage level according to the tracking error. FIG. 8 shows the error signal characteristic of the adder circuit 18 when the area in which the PCM signal of the main signal is recorded at the tape winding angle of the cylinder is 60 °. In the figure, 16 indicates the output of the sample and hold circuit 16, and 17 indicates the output of the sample and hold circuit 17, and the sum of these is the output of the adder circuit 18.
Here, the stable point of tracking control of this characteristic is at the time of tracking of 0 ° and ± 180 °. 0 °
Is the head locus shown in FIG. 6 and stably reproduces the PCM signal. Further, ± 180 ° is intended that the place shifted one track from the trajectory of Figure 6 head traces, if shifted by one track upwards, the head 2A is a track A _1, the head 2B is the track B ₁ PCM signal Can be stably reproduced. Therefore, by performing tracking control with the output of the adder circuit 18, it is possible to obtain a stable PCM reproduction signal during double speed reproduction.

The above-described embodiment of the present invention was performed with the recording pattern of the pilot signal shown in FIG. 2. However, also in other recording patterns, the error signal during normal tracking should be sampled and held at the timing of FIG. 7 and added. Thus, an error signal at the time of variable speed reproduction is obtained.

FIG. 9 shows an embodiment of the present invention which solves the problem that the embodiment shown in FIG. 3 has a stable point during 180 ° tracking during variable speed reproduction. Reference numerals 30 and 31 are comparison circuits for comparing the outputs of the sample and hold circuits 16 and 17 with the 0 level voltage as a reference, and output "1" when the voltage is higher than the 0 level and "0" when the voltage is lower than the 0 level. Reference numeral 32 is an inverter, 33 is an AND circuit, and 34 is a switch, which are controlled by the AND circuit 33, and are connected to the 34A side when the AND circuit 33 is "0" and to the 34B side when it is "1". Also, 35
_Has a voltage of V _{TR at} a voltage source, and other symbols are the same as those in FIG. 3 and perform the same operation. The stable point at the time of 180 ° tracking in the embodiment of FIG. 3 is that the sample and hold circuit 16 has a positive level and
It is when the output level of 17 is negative. If this is detected and the error signal is switched to a certain voltage, the stable point at 180 ° tracking is eliminated. In Figure 7, the sample and hold circuit is used to detect 180 ° tracking.
The outputs of 16 and 17 are added to the comparison circuits 30 and 31, respectively, and are performed by the inverter 32 and the AND circuit 33. That is,
The AND circuit 33 outputs the "1" level only when the sample and hold circuit 16 has a positive voltage and the sample and hold circuit 17 has a negative voltage. This AND circuit 33
Thus, by controlling the switch 34, when the AND circuit 33 is “0”, that is, when the 180 ° tracking is not performed,
Similarly to FIG. 3, the output of the adder circuit 18 is supplied to the output terminal 20, and when the AND circuit 33 is "1", the voltage V _{TR of the} voltage source 35 is supplied.
Are supplied to the output terminal 20. Therefore, the error signal characteristic of FIG. 9 becomes as shown by 34 of FIG. 10, and the stable point at the time of 180 ° tracking can be eliminated.

〔The invention's effect〕

According to the present invention, in a rotary head type magnetic recording / reproducing circuit in which a track is divided into regions and pilot signals for tracking control are recorded at two places, optimum reproducing control is performed during variable speed reproduction, and a stable reproduction signal can be obtained. There is an effect.

[Brief description of drawings]

1 and 2 are views showing a tape recording pattern of a rotary head system in which a track area is divided, FIG. 3 is a circuit diagram showing an embodiment of the present invention, and FIG. 4 is the timing of the operation of FIG. FIG. 5 is a diagram showing the output level of FIG. 3, FIG. 6 is a diagram showing a desired head locus during variable speed reproduction, FIG. 7 is a diagram showing operation timing, and FIG. FIG. 9 is a diagram showing an output level in variable speed reproduction, FIG. 9 is a circuit diagram showing another embodiment of the present invention, and FIG. 10 is a diagram showing an output level in variable speed reproduction in FIG. . 1 ... Magnetic tape 12,13,16,17 ... Sample hold circuit 14 ... Timing circuit 11 ... Wrapping line detection circuit, 30,31 ... Comparison circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Furihata 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Home Appliances Research Institute, Hitachi, Ltd. (72) Inventor Fujio Okamura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa (56) References JP-A-60-22761 (JP, A) JP-A-60-143469 (JP, A)

Claims (1)

[Claims] 1. A rotary magnetic head having at least two azimuth angles different from each other, wherein tracks are alternately formed on the magnetic recording medium by the rotary magnetic head to perform recording and reproduction, and the area of the track is a main signal. , A first pilot signal area arranged on one side of the main signal area for performing tracking control, and a first pilot signal area arranged on the other side of the main signal area for performing tracking control. And a second pilot signal region for the purpose of providing a tracking control means for performing tracking control at the time of reproduction by the first and second pilot signal regions. The control means is arranged such that, during the normal reproduction in which the reproduction is performed at the normal tape feeding speed, each of the rotary magnetic heads has the first and second pilots. Each time the signal area is traced, a means for generating a tracking error signal from the signal reproduced at that time, and a variable speed reproduction for reproducing at a tape speed N times the normal tape feeding speed (where N is an integer) A signal reproduced when one of the rotary magnetic heads traces the first or second pilot signal area, and a signal reproduced when the other of the rotary magnetic head traces the second or first pilot signal area And a means for generating a tracking error signal from the signal reproduced by the rotary head type magnetic recording and reproducing apparatus.