JPS60170020A - Height control method of magnetic head - Google Patents

Abstract

PURPOSE:To always put the recorded video signals on a standardized recording track and to prevent a tracking shift in a reproduction mode of another type of device, by always controlling the height of a magnetic head at a standard level in a video record mode. CONSTITUTION:Video heads 2A and 2B containing head mobile elements are supported by a rotary cylinder 1, and audio heads 4A and 4B which FM-record the sound signals are set at positions where a 90 deg. phase difference is produced. Thus the control pilot signal can be recorded on a recording track prior to a video head. An audio head is switched electrically to a video head at an overlap part 11 between upper and lower parts of video tracks 6A and 6B which are not used as video signals and at a position corresponding to several frequencies of a horizontal synchronizing signal. The variances of the heads 2A and 2B to the standard recording track are detected by reading the pilot signals recorded on two adjacent recording tracks and using the difference between both signal levels. Then the video head is switched again to a record mode. At the same time, the head mobile element is controlled to correct a tracking shift if detected. Then the video signal is recorded after setting the head on a correct tracing position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for controlling the height position of a magnetic head in a rotary head type magnetic recording/reproducing device, which allows the magnetic head to be correctly positioned on a recording track during recording.

[Background of the invention]

When performing special playback such as slow, still, and high-speed searches with a conventional magnetic recording and reproducing device that has a rotating magnetic head, the magnetic head draws a trajectory at a certain angle with respect to the regular recording track. There was a misalignment between the head and the head.

As a result, the head output decreased and noise was generated on the playback screen. As a countermeasure to this problem, a method has been proposed that mechanically corrects the head position deviation during recording.

For example, there is a rotating magnetic head device that uses an electro-mechanical converter such as a bimorph made of a piezoelectric element. This has made it possible to perform so-called automatic tracking reproduction in which the magnetic head follows a recording track while displacing the magnetic head in the vertical direction.

However, since the characteristics of the bimorph as an electro-mechanical converter change with physical changes, it is difficult to obtain stable operation.

That is, after a voltage is applied to the bimorph, a hysteresis phenomenon occurs in which the bimorph does not return to its original position even when the voltage is removed, or the initial setting position changes over time or due to environmental changes. Therefore, when recording with a magnetic head using a bimorph, the recorded tracks may have irregular widths or may be deviated from the standard track position. If such a magnetic tape is played back by another device, the image quality may deteriorate due to insufficient output. Therefore, in order to obtain high-quality reproduced images with other devices, that is, to maintain compatibility, it is necessary to always place the magnetic head at a predetermined height with respect to the reference of the cylinder, such as the tape guide groove of the cylinder, during recording.

A method of controlling the height of the magnetic head during recording that eliminates the relative height difference (head step) between two magnetic heads based on a pilot signal recorded on a part of the recording track. But, Now yrom P
h1lips (1979-6). However, in the above magnetic head height control method, the head is adjusted at a position that deviates from the reference height, so the distance from the control head to the magnetic head for reproduction is l! 1
l (X value) changes.

The X value is standardized for compatibility with other devices, and even if this value is exceeded, a misalignment will occur between the head and the recording track, making it impossible to obtain sufficient output.

This method of adjusting the relative height of the magnetic head causes the timing of the trace to shift when playing back on another device, so-called tracking shift, so there is a problem in that adjustments must be made constantly. be.

[Purpose of the invention]

In a magnetic recording/reproducing device having a magnetic head supported by a head movable element such as a piezoelectric element, the height position of the magnetic head during recording is always placed at a reference height position, and the height position of the magnetic head during reproduction is An object of the present invention is to provide a method for controlling the height position of a magnetic head that prevents tracking deviation.

[Summary of the invention]

In the height position control method of a magnetic head of the present invention, a fixed magnetic head B is used to record and reproduce images supported by an electro-mechanical transducer such as a piezoelectric element, in advance of a movable magnetic head A. A pilot signal for controlling the height position of the magnetic head A is recorded on a recording track that is not used as a signal,
This pilot signal is read by the magnetic head person, a deviation in the height position is detected based on the output signal of the magnetic head person at that time, the electro-mechanical converter is operated to correct this deviation, and then the magnetic head A is The feature is that the video signal is recorded by switching to the recording mode.

Signals recorded in overlapping portions of tracks that are not used as video signals are on regular tracks. Then, the magnetic head reads out the signal, positions it on the regular recording track based on the result, and then switches to the recording mode to record the video signal, so the video signal is always recorded on the regular recording track. and has excellent compatibility with other machines.

In other words, when playing back on another device, there is less noise caused by output reduction and a high quality image can be obtained.0 [Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be explained based on the drawings. The figure shows the structure of a magnetic head A (hereinafter referred to as a video head) for recording and reproducing video and a rotating magnetic head for recording pilot signals for control.

A piezoelectric bimorph 3A as a head movable element (electro-mechanical converter) with a 180° phase difference in the rotating cylinder 1,
One end of the video head 5B is fixed, and video heads 2A and 2B having different azimuth angles are supported on the other end. Magnetic heads B (hereinafter referred to as audio heads) 4A and 4B for recording 7M audio signals are arranged at positions having a phase difference of 90 degrees with respect to the video head. The audio heads 4A and 4B have an azimuth angle different from that of the video heads 2A and 2B, and have a head step between them and the video head so that a control pilot signal can be recorded on the recording track in advance of the video head. is provided.

FIG. 2 is a recording pattern diagram seen from the base surface of a magnetic tape standardized in current magnetic recording and reproducing apparatuses.

6A and 6B are video tracks, and FM is on this track.
Tracks o7A and 7B on which audio signals are also recorded are tracks for AM recording of audio signals. 10. 11 is a video track 6A (the overlapped portion of the upper and lower parts which are not used as a video signal in SB); 13 is a track for recording control pulses for tape speed control; Guard punt 8.9
．． 12 are provided.

In the overlap section 11, the audio head is electrically switched to the video head at a position corresponding to several cycles of the horizontal synchronizing signal, for example, seven cycles (7H). A pilot signal for controlling the height position of the video heads 2A, 2B is recorded by the audio head 4A4B in a certain section of the overlap part 11 in front of the video head switching position P. For example, from video head switching position P to pzaf 4
H minutes (254μ8 if 1H is 66.5μS) is recorded in the overlap area 11''.This recorded frequency can be read by the audio heads 4A and 4B and the video heads 2A and 2B having different azimuth angles. Taking this into account, a low frequency of 100 to 200 KH2 is used.The deviation of the video heads 2A and 2B from the regular recording track is detected by taking the pilot signal recorded on the adjacent recording track and adjusting the signal level of both. Detection is based on the difference.Therefore, four different frequencies (fl-f4) within the above frequency band are used as pilot signals.To audio 7) "4A and 4B are used after recording 4H worth of control pilot signals. , record a normal audio signal onto a recording track.

The video head detects the rotation of the motor that drives the rotary cylinder, and is switched at point P (shown in FIG. 2(B)) by a head switching signal generated based on the detection signal.

Next, the video heads 2A and 2B are placed in a temporary playback mode, and the fixed audio head reads out the pilot signal recorded on the regular recording track. In other words, in order to read out the pilot signals recorded on the adjacent tracks on both sides at the same time, only the section 2H (see Figure 85) is set to temporary playback mode.
Read the pilot signal and add more cores. For example, as shown in Figure 3, assuming that two video heads are tracing the track where the f4 pilot signal is recorded, @
The pilot signals of matching f and f are also regenerated. Since this uses a low frequency pilot signal, it is possible to sufficiently detect heads with different azimuth angles. In this way, if one head detects a signal including the pilot signals of both legs, the difference frequency (f4'
By comparing the signal levels of Isf4-fI), the amount of deviation of the video head 2A from the normal recording track can be determined. Then, the video head switches to recording mode again, and at the same time, when there is a difference in the signal level of the difference frequency, that is, there is a so-called track deviation, the head driving element is controlled to correct the deviation, and the head is correctly traced. 3 is a basic circuit block diagram for performing the above operation. Four types of frequencies f1 to f4 generated by the pilot signal generation circuit 14 are sequentially inputted to the gate switch circuit 16 by switches S, to S4. switch B,
The synchronizing signals φ1 to φ4 for operating the -w 84 regulate the timing at which the audio heads 4A and 4B start recording pilot signals, and are generated by the pulse generation circuit 17 based on the head switching signal. FIG. 4 shows the timing of the head switching signal and synchronizing signal at this time and the relationship between the video head and the audio head. In this figure, when the video head switching signal is at H level, two video heads are recording and one is at I level.
When the level is Jo, the video head 2B is recording.

Since the audio head is disposed at a position shifted by 90 degrees on the cylinder with respect to the video head, the recording timing is shifted.

Therefore, when the synchronizing signal φ1 is H level, the gate circuit 1
The pilot signal input to 6 is fl, hereinafter φ8
, φ8, φ, pilot signals fI, fS, '4 are sequentially input to the gate circuit 16.

The gate circuit 16 transfers the video head switching signal to the delay circuit 1.
The gate 16 is opened by 4B from 7B before the video head switching point P by the delayed signal obtained through the video head switching point P. At this time, the pilot signal is connected to the audio head recording amplifier 19, and its output is transmitted to the audio head 4A,
4B and recorded on the recording track. continue,
The gate circuit 16 is switched to the F'M audio signal generating circuit 20, and the recording signal from said circuit is recorded on the recording track.

On the other hand, according to the video head switching signals 2A and 2Bl-1, the video head switching position
Only section B is switched to the reproduction mode, and the pilot signal of the section is read out. This reproduced pilot signal is sent to a preamplifier 25 through a gate circuit 22 which is closed by a delayed signal obtained by passing a video head switching signal through a delay circuit 22. From the output of the preamplifier, only the pilot signal f, % f4 is extracted by a bandpass filter 24 and sent to an error detection circuit 25. The circuit configuration shown in FIG. 5 is an error detection circuit 25 for driving one video head. In this error detection circuit, the amount of deviation of the video head is detected from the signal level of the pilot signal obtained by the bandpass filter 24. Assuming that the video head is currently tracing the recording track on which the pilot signal f is recorded, the pilot signal from the bandpass filter 24 becomes a signal of a certain level having frequency components. Both signals are then input to an adder 30 to produce an output cuff (t) shown by equation (1).

7(t)""Igln 2πfl t + Pg m
2πf, t ・・−・−・・(11 Next, multiplier 3
y(t) = P, m 2π
A signal y is obtained by multiplying f, t by the signal 7 (t) of the above-mentioned equation 0), which is expressed by equation (2). Obtain (1).

yn(t) =÷P Akanetm 2π('! 's, )
t+÷P1P3cos2π(fs −ft)t, (tuft 2
π(ft +'t) to ovary 2π(fs+fz)t)
・・・・・・・River・・Song・・＋21Here, fh=f
, -f, ,3f), = f3-f, components are extracted by pad/dopass filters 52A, 32B, and detectors 53A, 3
5B performs envelope detection. After that, differential amplifier 3
4, the output cuff e (t) shown by equation (3) is created.

ye(t)=7Pt(P+-Ps) -・-song-(31
The output of the differential amplifier, that is, the output of the error detection circuit 25 is sent to the bimorph 3 via drive amplifiers 26A and 26B.
A and 5B are input to cause mechanical displacement.

〔Effect of the invention〕

As described above, according to the present invention, during recording of a magnetic recording/reproducing apparatus having a magnetic head supported by a head movable element such as a piezoelectric bimorph, which has physically unstable characteristics such as changes in initial setting position, Since the height position of the magnetic head can be controlled so that it is always placed at the standard position, the recorded video signal is always on the standardized recording track, and tracking deviation does not occur when playing back on other models. This has the advantage that sufficient head output can be obtained to obtain high-quality images.

[Brief explanation of the drawing]

Figure 1 is a diagram of the arrangement of the magnetic head on the rotating cylinder, Figure 2 (A) is a diagram of the track pattern on the magnetic tape, and (B) is a diagram of the track pattern on the magnetic tape.
3 is an enlarged view of the same main part (marked with ○), FIG. 3 is a basic circuit diagram for performing the operation according to the present invention, No. 411: Overlapping portion of recording tracks, f1 to f4: Height of the head pilot signal for position control; 14... pilot signal generation circuit; 17... synchronization signal generation circuit; 25... error detection circuit. Agent Tatsuyuki Unuma 1 Figure 4 Δ Figure 2 (A) (8) Figure 3 Figure 4 f, 'S Figure 5 Procedural Amendment May 1, 1980 To the Commissioner of the Japan Patent Office -も'') ■, Indication of the case 1982 Patent Application No. 24029 2, Name of the invention, Method for controlling the height position of a magnetic head 3, Person making the correction Relationship to the case Name of patent applicant (510) Hitachi, Ltd. 4, Agent Person 7. Detailed description of the invention in the specification to be amended. 8. Contents of the amendment (1) Change "record" to "reproduction" in line 11 of page 2 of the specification. (2) “Height and” on page 3, line 15 of the specification is “height”
Changed to (3) Change "22" to "21" on page 11, line 19 of the specification.

Claims (1)

[Claims] A pair of magnetic heads A for recording and reproducing video signals is supported on a head movable element whose one end is fixed to a rotating cylinder, and a pair of magnetic heads A for recording and reproducing audio and control signals on the rotating cylinder between the magnetic heads A. When recording with a rotary head type magnetic recording/reproducing device having a fixed head B, a pilot signal for controlling the height position is recorded by the magnetic head B on a part of the recording track of the video signal prior to the magnetic head A. ,
This pilot signal is reproduced by the magnetic head A, the head movable element is controlled based on the head output signal, and after correcting the deviation in the height position of the magnetic head A, the recording mode is switched to record the Eirin signal. A method for controlling the height position of a magnetic head.