JPH01317258A - Magnetic recording/reproducing device - Google Patents

Abstract

PURPOSE:To automatically correct the level difference caused between the tracking error signals by applying the average addition value of the outputs of four memories to the tape feed control as an actual tracking error signal. CONSTITUTION:A tracking error signal detecting circuit 3 detects a tracking error signal based on the reproduction signal received from a magnetic head 1. The tracking error signal is corrected by a level difference correcting circuit 8 in response to an actual tracking error. This corrected error signal is sent to a capstan control circuit 4 and the phase control is applied to the tape feed via a capstan 6. In other words, the circuit 8 contains four memories 21-24 corresponding to the reference pilot signals of four types of frequencies and the means 12 and 13 which calculate the average addition value of the outputs of said four memories. Than the tracking error signal values are written into the memories 21-24 corresponding to the relevant reference signals. The tape feed control is carried out based on the value obtained by the arithmetic for said average addition value. Thus it is possible to automatically eliminate the level fluctuation of the tracking error signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magnetic recording and reproducing devices, particularly rotary head type VTRs.
In a VTR that uses a magnetic head to record and reproduce pilot signals of four frequencies for tracking control along with a video signal, and obtain a tracking error signal for tape feeding from the reproduced signal, the level included in the tracking error signal. The purpose is to eliminate differences.

Conventional VTRs with the ``8 mm video'' standard record a 4-frequency pilot signal for tracking control along with the video signal as a tracking control method, and during playback, the tracks to be played are tracked from both adjacent tracks. The level difference between the crosstalk components of the pilot signals is used as a tracking error signal.

FIG. 3 is a block diagram showing the configuration of the recording/reproducing head and tape feed control system. A reproduction signal containing a tracking pilot signal reproduced by the rotary head 1 attached to the rotary head drum 2 is sent to the tracking error signal detection circuit 3 via the first stage amplifier 9. The tracking error signal detection circuit 3 creates a tracking error signal from the reproduced signal. The obtained tracking error signal is sent to the capstan control circuit 4 to control the feeding phase of the capstan 6. The capstan control circuit 4 obtains a rotation speed detection signal from a rotation speed detector 5 attached to the capstan 6, and controls the speed of the capstan 6 through a drive circuit 7. , which controls the feed phase.

A method for detecting a tracking error signal using a pilot signal will be explained in detail below.

In FIG. 6, A1, B1, A2. B2... are each recording track recorded by the A head and the B head.

The arrow (a) indicates the direction of rotation and scanning. In each recording track, each pilot signal indicated by f1 to f4 is sequentially recorded for each field together with the video signal. The recording order of the pyro-soto signals is f1, f2. f3.
The data is circulated in the order of f4, and fl is recorded next to f4. Further, within each field period, the type of pilot signal is fixed and recorded. The frequency of the pilot signal is set, for example, to the value shown in the table. Note that in Table 1, f
H indicates the frequency of the horizontal synchronization signal in the video signal, and 8
．． 5fH indicates a frequency that is 6.5 times the frequency of the horizontal synchronization signal.

(The following is a blank space) The frequency difference of the pilot signal between each recording track is <, fH or 3fH as shown in FIG. When the head scans the Ai (t=1+2...) track, the frequency difference between the pilot signal of the scanning track and the pilot signal recorded on the adjacent track on the right side on the paper is always fH, and that on the left side is always fH. Always 3fH
It is. When the head scans the Bi (i=1.2*・) track, the relationship is reversed to that described above, and the frequency difference of the pilot signal with the adjacent track on the right is always 3f■, and that on the left is always fH. be.

Since the pilot signal is a relatively low frequency signal around 100 kHz, the pilot signal recorded on the adjacent track can be reproduced as a crosstalk signal without the head scanning over the adjacent track. For example, the pilot signal obtained when the head on-tracks the A2) rack and performs reproduction scanning is f3. f2. It is a composite signal of fl, and its level is highest at f3, followed by f3.
2°f4 is reproduced at the same level.

When the head slightly deviates from track A2 toward track B2 and performs playback scanning, the level of the pyro/soto signal obtained is f3. f4. It becomes smaller in the order of f2. Conversely, when the head shifts to the track B2 side and scans, the obtained pilot signal is f3° f2. It becomes smaller in the order of f4. Therefore, by separating and extracting the difference signals fH and 3fH between the pilot signal on the main scanning track and each pilot signal recorded on both adjacent tracks, and comparing the reproduction levels of both signals, The amount and direction of head displacement can be known.

FIG. 7 is a block diagram of a reproducing circuit for obtaining a tracking error signal. In FIG. 7, a reproduced signal in which a video signal and a pilot signal are combined is inputted from a terminal 101. The circuit 102 is a low-pass filter and extracts only the pilot signal from the combined reproduced signal.

The pilot signal obtained at this time is a composite signal of the main scanning track and the pilot signals recorded on both adjacent tracks. Circuit 103 is a balanced modulator that multiplies the aforementioned composite pilot signal by the reference signal supplied from terminal 104. The reference signal provided at terminal 104 provides a signal at the same frequency as the pilot signal recorded on the main scan track. For example, in FIG. 6, when the head performs reproduction scanning on track A2, the input signal to balanced modulator 103 is f2. f3. Each signal is f4, and the signal input from the terminal 104 is f3. Therefore, the output signal of balanced modulator 103 is f2. f3゜f
Signals having the sum and difference frequencies of each signal of f3 and the signal of f3 are output. The circuit 105 is a tuned amplifier tuned to the fH signal, and the circuit 107 is a tuned amplifier tuned to the 3fH signal. Circuits 106 and 108 are amplitude detectors, and circuit 109 is a level comparator. Therefore, each pilot signal taken out as a crosstalk signal from both adjacent tracks is taken out as a difference signal with the pilot signal recorded on the main scanning track, and then the level comparator 109 determines the level. A signal corresponding to the difference is taken out to terminal 110. As for the signal obtained at the terminal 110, when the reproduction level of fH is higher than the reproduction level of 3fH, a (+) potential corresponding to the level difference is taken out, and in the opposite case, a (-) potential is taken out. Terminal 11
Since the signal taken out at 0 includes information on the amount and direction of the head's track deviation, it can be used as a tracking error signal.

However, a tracking error signal that is actually suitable for practical use requires further processing. This is because, as is clear from FIG. 6, the relationship between the head displacement direction and the multiplication output CfH or 3fl() obtained at that time is opposite to each other for the N A t ) rack and the Bi) rack. It is from. Therefore, the analog inverter 111 and the switch 112 may be used to invert the signal at the terminal 110 in an analog manner when the head scans the Ai) rack and when the head scans the Bi track. In other words, when Ai) rack scanning is performed through the switch 112, the terminal 11 is
0, and when scanning a Bi track, it is connected to the output of the analog inverter 111. This can be handled by switching the pilot signal name depending on whether it is an odd number or an even number. As a result, the output signal at the terminal 114 becomes A
II B i) Regardless of the rack, if the head deviates to the right from the track to be scanned, a (+) potential is always applied; if the head deviates to the left, a (-) potential is always applied. Therefore, by controlling the capstan motor using the signal obtained at the terminal 114, the head can always be scanned on-track on the main scanning track.

The above is an overview of the method for obtaining a tracking error signal using pilot signals of four frequencies. If this tracking error signal is used to control tape advance, the head will always be on-track and scan on the recording track. It is something that can be done.

Problems to be Solved by the Invention The tracking control method described above has the following problems.

In a tracking method using pilot signals of four frequencies, when on-track, the amount of crosstalk pilot signals from both tracks should be equal, but for example, if the recording levels of the pilot signals of four frequencies are slightly If there is a deviation, or if the reproduction circuit including the reproduction head has frequency characteristics, the amounts of crosstalk pilot signals will not necessarily be equal even in an on-track state. Figure 4 shows that the reproduction levels of pilot signals of four frequencies are f1, f2, f4, f.
An example is shown in which the values increase in the order of 3.

When the reference pilot signals switch in the order of f1, f2, f3, and f4, the outputs of the fH tuning circuit and the 3fH tuning circuit change to the levels of the crosstalk pilot signals of f2, f1, f4, and f3, and f4, f3,
It changes to correspond to the level of the crosstalk pilot signals of f2 and fl. Therefore, when it corresponds to the level of f3, the output becomes the largest, and when it corresponds to the level of fl, the output becomes the smallest. Therefore, since the level difference between the amplitudes of the output signals of this tuning circuit is used as the tracking error signal, the obtained tracking error signal has the same period as the repeating period of switching the pilot signals of the four frequencies, as shown in Figure 4. It will fluctuate.

FIG. 5 is a waveform diagram showing changes in the tracking error signal when there is a level difference in the characteristics of the tuning circuit. For example, if the sensitivity of the fH tuning circuit is higher than the sensitivity of the 3fH tuning circuit, the output of the fH tuning circuit will always be large, as shown in Figure 5, and the resulting tracking error signal will be Even in the track state, changes occur repeatedly every time the pilot signal is switched.

If a tracking error signal that changes even when the track is on track is detected, not only will the tracking accuracy decrease, but also because this signal is used to control the tape advance phase, the capstan It also causes uneven rotation.

When actually recording and reproducing, it is difficult to reproduce signals of four frequencies with completely the same sensitivity, and
In order to completely match the amplitude characteristics of the system tuning circuits, it is necessary to make fine adjustments using highly accurate circuits.

Therefore, there is a high possibility that such a problem will occur, and some kind of countermeasure is required. To solve this problem, for example, in Japanese Patent Laid-Open No. 59-195384, a means for varying the level of the tracking error signal is provided,
It is suggested that adjustments be made so that the level difference can be corrected manually.

An object of the present invention is to automatically correct the level difference even if a level difference occurs in the tracking error signal due to the above-mentioned factors, so as not to cause uneven rotation of the capstan.
The object of the present invention is to provide a method that does not cause a decrease in tracking accuracy.

Means for Solving the Problems In the present invention, in order to solve the above-mentioned drawbacks, four storage means corresponding to reference pilot signals of four types of frequencies are provided.
It has means for calculating an arithmetic average value of the output values of the four storage means, writes the tracking error signal value into the four storage means corresponding to the reference signal used to obtain the tracking error signal value, and calculates the arithmetic average value. Tape feeding control is performed based on the calculation results of the means.

The tracking error signal obtained from the action reproduction signal is stored in one of the four memories corresponding to the type of current reference pilot signal.

The average value of the output values of the four memories is determined, and the obtained average value is used as an actual tracking error signal for tape feeding control. The contents of the four memories are:
Since it corresponds to a pilot signal, the value of each memory becomes a value corresponding to a level value. By taking the average value of the four memories, it is possible to absorb the level difference in the tracking error signal related to the reference pilot signal, and it is possible to obtain a tracking error value with the level difference removed.

Example An embodiment of the present invention will be described based on the drawings.

FIG. 2 is a block diagram showing the overall configuration of an embodiment of the present invention. That is, as in the conventional example, a tracking error signal is detected by a tracking error signal detection circuit 3 based on a reproduced signal obtained from a magnetic head 1 attached to a rotary head drum 2 via a first stage amplifier 9.

Since this tracking error signal may include a level difference as described in the conventional example, it is corrected by the level difference correction circuit 8 so as to correspond to the actual tracking error. The corrected tracking error signal is
The signal is sent to the capstan control circuit 4, and the phase of tape feeding by the capstan 6 is controlled.

The above is the overall configuration.

Next, the specific configuration of the level difference correction circuit 8 will be explained with reference to FIG. In FIG. 1, the tracking error detection circuit 3
The tracking error signal obtained is sent to the memory a21. through the switching circuit 11. Same b22, same c23. Sent to same d24. The switching circuit 11 switches only one of the memories a21 to d24 to -
It is assumed that it is connected only once and is OFF at all other times. The switching circuit 11 switches the connected memory every time the reference pilot signal is switched.

In other words, each time you advance one track, the memory is changed from 21 to 22.
→ 23 → 24 → 21 → . . . It switches cyclically. Further, the memories 21 to 24 correspond to reference pilot signals fl to f4, respectively. For example, it is assumed that the memory a21 corresponds to the level when the reference pilot signal is fl, and the memory b22 corresponds to the level when the reference pilot signal is f2. (Memory C23, memory d24
Similarly. ) The outputs of the memories 21 to 24 are input to the adder 12, and the addition result is input to the divider 13 to divide the value into 1/4. That is, the values in the memories 21 to 24 are averaged. The averaging result is obtained by averaging tracking error signals including level differences, and the level differences are also averaged.

Therefore, the average result becomes a tracking error signal with the level difference corrected. Therefore, by performing tape feed phase control using this corrected tracking error signal, the effect of the level difference in the tracking error signal described above can be eliminated.

Although the embodiment of the present invention has been described in terms of the flow of signals as shown in FIG. 1, it is also easy to implement this processing using microcomputer software. In this case, the switching circuit 11 can be realized by categorizing the types of reference signals and writing the tracking error signals at that time into the respective memories. In particular, a method for realizing control of a rotating head drum, tape feed phase control, etc. in a magnetic recording/reproducing device using microcomputer software is described in Japanese Patent Application Laid-open No. Sho Ei 2-33358. If implemented using software, no new circuits are required, so the effect is very large.

Further, although the present invention has been described using a pilot signal system for four rounds, it is generally also effective when using n types of pilot signals, and in that case, it can be realized by using n memories.

Effects of the Invention As described above, the present invention can eliminate fluctuations in the level of the tracking error signal due to fluctuations in the recording/reproducing characteristics or fluctuations in the tuning circuit, thereby improving accuracy. It does not require the use of high-performance circuits or fine adjustments, and is highly effective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a tracking error signal level difference correction circuit in a magnetic recording/reproducing device according to an embodiment of the present invention, FIG. 2 is a block diagram showing the overall configuration of the same device, and FIG. 3 is a block diagram of a conventional example. FIG. 4 is a block diagram showing the overall configuration of a magnetic recording and reproducing apparatus, and shows the state of a tracking error signal when the reproduction levels of pilot signals of four frequencies do not match in a magnetic recording and reproducing apparatus according to an embodiment of the present invention. Waveform diagram, Figure 5 is a waveform diagram showing the state of the tracking error signal when the characteristics of the tuning circuit do not match in the same device, Figure 6 is an explanatory diagram showing the recording pattern of the pilot signal in 8 mm video, Figure 7 1 is a block diagram of a tracking error signal detection circuit; FIG. 1...Magnetic head, 2...Rotating head drum, 3.
...Tracking error signal detection circuit, 4.Capstan motor speed control circuit, 8.Level difference correction circuit,
11, 15. 20... switch, 16. 17
．． 18°19...Memory. Name of agent Patent attorney Toshio Nakao and one other person (Gi

Claims (2)

[Claims] (1) N types (N is an integer) of tracking control pilot signals are cyclically switched for each discontinuous trajectory as discontinuous magnetization trajectories on the magnetic tape by a rotating head, and are recorded and reproduced together with the information signal. In an apparatus for controlling a tape feed control means, sometimes using a tracking error signal obtained by signal processing the reproduced pilot signal, N storage means corresponding to the N types of pilot signals; 1. A magnetic recording and reproducing apparatus, comprising a calculation means for calculating an average of the values stored in the storage means, and controlling the tape feed based on the calculation result of the calculation means. (2) As a pilot signal for tracking control, 4
Pilot signal for tracking control of various frequencies (f
1, f2, f3 and f4) for each discontinuous trajectory f1→
It switches cyclically as f2→f3→f4→f1→... and records and reproduces it together with the information signal.During reproduction, crosstalk pilot signals from both adjacent tracks to the track to be reproduced are used. Obtain a tracking error and use the tracking error signal to
The tape feed control means is controlled by the four storage means corresponding to the pilot signals of the four types of frequencies;
2. The magnetic recording and reproducing apparatus according to claim 1, further comprising arithmetic means for calculating an average of the values stored in the two storage means.