JPS6348082B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating head type magnetic recording/reproducing device (hereinafter referred to as a VTR, including a device without a recording function), in particular a drive device comprising an electro-mechanical transducer such as a piezoelectric element. This invention relates to a device for adjusting the height of a rotating head attached to a movable part of an element.

One method for performing slow and still playback on a VTR is, for example, by displacing the rotary head in the width direction of the track during playback to correct track deviation due to the difference in tape speed from the time of recording, thereby obtaining special speed playback images without noise bars. There is something to try.

Furthermore, in order to faithfully reproduce a recorded track, an automatic tracking method has been proposed in which the reproduction rotary head is displaced in the width direction of the track so that the reproduction output is always maximized. In all of these, a rotating head is mounted on a drive element such as a piezoelectric element, and an appropriate drive signal is applied to the drive element.
This is accomplished by moving the rotating head across the width of the track.

FIG. 1 shows an example of the construction of a cylinder with a rotary head mounted on a drive element as described above. In the azimuth recording type VTR, numerals 1 and 2 are rotary heads for recording, each having a different azimuth angle. 3,4
are rotary heads exclusively for reproduction, which are respectively attached to the movable ends of drive elements 5 and 6, and have the same azimuth angle, for example, to enable field reproduction. Here, the heights of the recording rotary heads 1 and 2 are adjusted at the time of manufacture so that they are almost the same, and the height difference is only about a few micrometers. Therefore, the pattern recorded on the magnetic tape by the recording rotary heads 1 and 2 has tracks of azimuth angles L and _R as shown in FIG.
R ₁ , L ₂ , R ₂ , L ₃ , R ₃ , etc. are arranged regularly in sequence. The drive elements 5 and 6 are, for example, vibrators in which two piezoelectric elements 11 and 12 having electrodes on both sides are bonded together in a bimorph shape as shown in FIG. , 4 are attached, and by applying a voltage E between the electrodes of the piezoelectric element, the tips of the rotary heads 3 and 4 can be displaced in the direction of the arrow. Therefore, by appropriately controlling the applied voltage E, it is possible to displace the rotary head in the width direction of the track to perform correct scanning along the desired track.

However, it is known that the reference position (the position of the tip of the head when the applied voltage is zero) of the drive element cannot be determined due to changes over time, temperature, or history of use. Therefore, the heights of the rotating heads 3 and 4 in FIG. 1 are often different when the applied voltage is zero.

When two rotary heads have independent automatic tracking systems, a phenomenon of track jump may occur depending on the position of the rotary heads before starting the automatic tracking operation. What is this track jump?
This is a phenomenon in which the rotating head is drawn into a track other than the desired track, and the image on the playback screen appears blurred. This track jumping will be explained using the recording track pattern diagram in FIG. 2.

In the magnetic tape recorded as shown in Figure 2,
Now, consider still reproduction using the rotary heads 3 and 4 for reproduction. It is assumed that the rotary heads 3 and 4 for reproduction have the same azimuth L in order to realize field reproduction. Therefore, the rotating heads 3 and 4 are
L ₁ , L ₂ , L ₃ , ... can be reproduced. first,
Consider the case where there is no difference in the reference heights of the rotating heads 3 and 4. Now, if the center position of the rotary head 3 is at point P in Fig. 2, the rotary head 3 naturally scans the track _L2 , and records as shown by the broken line in the figure due to the difference in tape speed during recording and playback. Although the track pattern and slope are different, this
By applying a gradient wave potential change corresponding to the pitch,
Track _L2 can be scanned completely. When the scanning of the rotary head 3 is completed, the rotary head 4 comes to the point P, so that the track _L2 can be scanned in the same way, and complete field still reproduction can be realized. That is, if the rotating heads 3 and 4 are at approximately the same height, no track jump occurs.

However, if there is a step between the reference heights of the rotary heads 3 and 4, for example, the rotary head 3 will come to point P;
The rotary head 4 will come to point Q, and the rotary head 4 will scan on the track _L3 . That is, although originally the same track _L2 should be reproduced, one rotary head jumps to track _L3 . This is a track jump phenomenon that causes image blur in the reproduced image. In short, if there is a difference in level between the two drive elements, track jumps occur, resulting in an unsightly reproduced screen. In this example, we have explained the case where there is a step difference of 2 track pitches, but if an automatic tracking loop is configured for each of the rotary heads 3 and 4, each of them will be pulled into the nearby track, so even if there is a step difference of 1 track pitch, This causes track jumps.

The present invention provides a rotary head which is designed so that the heights of the rotary heads mounted on the head driving element are aligned in advance in order to avoid track jumping, which is the drawback of the conventional example as described above. The present invention provides a height adjustment device.

Hereinafter, the present invention will be explained with reference to the drawings. First, the principle of the present invention will be explained. now,
With the magnetic tape stopped and only the rotary cylinder rotating, a pilot signal is recorded in a specific section of one field by one rotary head. FIG. 4 is a magnetic tape pattern diagram showing the recording state. In the figure, 13 indicates the magnetic tape, and 14 indicates the locus (track) scanned by the recording rotary head. Since it is in a stopped state, in a VTR where the running direction of the magnetic tape 13 and the rotating direction of the rotary head are the same, the inclination of the track is higher than that recorded at normal speed. Furthermore, a section 15 indicated by diagonal lines in the figure is a section where the pilot signal is recorded. The pilot signal recording portion 15 is within a range defined by the width of the recording head and a predetermined section in one field, and since the magnetic tape is in a stopped state, no data is recorded in other fields (tracks). If a magnetic tape recorded in this way is played back using a rotary head other than the one used for recording without moving the magnetic tape, if the heights of the recording and reproducing rotary heads match, If it is, the pilot signal will be regenerated, but if there is a step difference of one track pitch or more, the pilot signal will not be regenerated. In other words, the horizontal axis represents the relative height of the rotating head for playback with respect to the rotating head for recording (+ is above and - is below).
If the reproduction output level of the pilot signal is plotted on the vertical axis, the characteristics shown in FIG. 5 can be obtained. This fifth
As is clear from the figure, in order to match the height of the recording head to the rotary head, the height of the reproducing head can be adjusted to the point where the pilot signal is at its maximum.

The rotary heads whose height is to be adjusted are the rotary heads 3 and 4 attached to the drive element, and the heights of these can be changed by the voltages applied to the drive elements 5 and 6. By applying a sweep voltage to change the height of the playback head and then holding the voltage at the point where the resulting playback pilot signal output is maximum, the height of the recording head will always remain the same. Become. In order to prevent the aforementioned track jump phenomenon, it is sufficient that the heights of the rotary heads 3 and 4 match. In this case, for example, a pilot signal is recorded and the heights are adjusted using the rotary head 4. This allows the heights of the two rotating heads to be made the same.

It is desirable that the pilot signal recording section be in a location that does not interfere with the original video signal; for example, an overlap portion of the magnetic tape (a portion where the signal is recorded but not displayed on the screen) is preferably used.

FIG. 6 is a configuration diagram showing an embodiment of the present invention. In the figure, a rotary head cylinder 7 is provided with rotary heads 3, 4 mounted on drive elements 5 and 6. Now, an adjustment device for adjusting the height of the rotary head 4 to match the height of the rotary head 3 will be explained based on the timing chart shown in FIG.

First, the operation of recording the pilot signal _f1 on the overlap portion of the magnetic tape will be described. Figure 7a
The head switch signal shown in (hereinafter referred to as HSW)
is 30Hz synchronized with the rotation of the rotating head cylinder 7.
Normally, when it is "H", the signal from the rotary head 4 is reproduced, and when it is "L", the signal from the rotary head 3 is reproduced. Now start switch 2
When 0 is pressed [see Figure 7b], the D input of the D-flip-flop circuit (hereinafter referred to as D-FF) 41 becomes "L", and the Q of the D-FF 41 becomes "L" due to the rise of HSW. "become. This is applied to the differentiating circuit 54, and the RS-flip-flop circuit (hereinafter referred to as RS-FF) 42 is set by the differentiating pulse, outputs the pulse shown in FIG. 7c, and is reset at the falling edge of HSW. This pulse causes
The analog switch 22 consisting of a FET is closed, a signal _f1 is recorded by the rotary head 3, and the count value of the counter 27 is reset. here,
When HSW is "H", recording with the rotary head 3 means recording on the overlapping portion of the magnetic tape. Now, after recording the pilot signal in this way, it must be reproduced by the rotary head 4. For this reason, the head amplifier 3 is designed to always reproduce only the playback signal from the rotary head 4 until the end of this operation so that the overlapping portion of the tape can be reproduced by the rotary head 4.
0 is controlled by the RS-FF 43, and its output is input to the band pass filter 31, allowing only the pilot signal _f1 component to pass and input to sample and hold circuits (S/H) 44 and 45. This is handled by the sample and hold circuits 44 and 45 shown in FIG. 7e.
Depending on the sample pulses from the AND gate circuits 51 and 52, either one performs sample and hold, and their outputs (see FIG. 7f, g) are supplied to the positive and negative input terminals of the comparator 46. As a result, as shown in the 3rd and 4th fields in Figure 7,
If the positive input>negative input, the output of the comparator 46 shows "H" as shown in FIG. 7h, and the next D-
Supply to FF47. In the D-FF 47, the Q output becomes "H" at the rise of a signal obtained by slightly delaying HSW by the delay circuit 55. This is shown in Figure 7i. The change is extracted by the differentiating circuit 48,
During this operation period, the AND gate circuit 50
is input to the latch circuit 33 (see FIG. 7j), and the counter value at this time is latched and held. Next, the counter 27 counts one step at the falling edge of HSW, and the digital-to-analog conversion circuit (D/A) 28 [its output is shown in FIG. 7d]
Then, the voltage applied to the driving element 6 through the amplifier 29 is increased, and the same operation is performed. What is important here is that during the period when the reproduced pilot signal increases (field numbers 1 to 8 in Figure 7), the Q of the D-FF47 is inverted for each sample, but the maximum reproduction output (field numbers 1 to 8 in Figure 7) is “H” or “L” after field number 9)
It is fixed and does not flip. Therefore, no pulse is input to the latch circuit 33, that is, the output value of the counter 27 at field number 9 is latched and held. Now, this operation continues until the counter 27 repeats counting and overflows. When an overflow occurs, the counter value latched at that time is preset in the counter 27. This is RS−FF
This is done by Q of 43. Also, if you leave the pilot signal _f1 in the overlapping area of the magnetic tape, it may malfunction the next time you perform the above operation near that area, so either erase the pilot signal or replace it with a different signal. must be recorded in the same location. Therefore, the overflow detection circuit 53 detects the
By generating a pulse during the "H" period of HSW (see FIG. 7K) and closing the analog switch 24, the rotary head ₃ records a signal _f2 having a frequency different from that of the pilot signal f1. This completes the series of operations.

In short, a sweep voltage generated by the counter 27 and the DA converter 28 is applied to the driving element 6, and by focusing on the pilot signal that the rotary head 4 reproduces using the sweep voltage, this signal is transferred to the two sample and hold circuits. In addition to signals 44 and 45, their outputs are supplied to both input terminals of a comparator 46, and if the output of the comparator 46 changes, this indicates that the pilot signal is increasing.
The FF 47 and AND gate circuits 51 and 52 form control pulses so that the sample and hold circuits 44 and 45 perform sampling alternately. At the same time, the output of the comparator 46 is D-FF47, the differentiating circuit 48,
49 generates a pulse when there is a change, so the final pulse simply indicates the maximum output point of the pilot signal. Therefore, the value latched by the latch circuit 33 with this final pulse is preset in the counter 27, and this value is held thereafter. As a result, the rotary head 4 is held at the same height as the rotary head 3.

As detailed above, according to the present invention, the reference height of the rotary head attached to the drive element can be adjusted to be the same height as other reference heads, thereby eliminating the occurrence of track jump. , it is possible to easily track a desired track on a magnetic tape. Furthermore, since the height adjustment is carried out when the magnetic tape is stopped, the magnetic tape may have a non-recorded portion or a recorded portion.
Moreover, it has effective features such as not causing any interference to the reproduced image of the recorded signal, so it is extremely useful for VTRs with a special speed reproduction function and VTRs with an automatic tracking function.

[Brief explanation of the drawing]

FIG. 1 is a top view of essential parts showing an example of the configuration of a rotary head cylinder, FIG. 2 is a recording pattern diagram of azimuth recording, and FIG. 3 is a diagram showing an example of the configuration of a head drive element.
FIG. 4 is a diagram showing an example of a track pattern recorded by the present invention, FIG. 5 is a characteristic diagram used to explain the principle of the present invention, and FIG. 6 is a main part configuration showing an embodiment of the present invention. 7a to 7k are timing charts in FIG. 6. 3, 4... Rotating head, 5, 6... Drive element,
7... Rotating head cylinder, 13... Magnetic tape, 21, 23... Oscillator, 22, 24... Switch, 26... Start switch, 27... Counter, 28... DA converter, 29... Drive amplifier, 30...Head amplifier, 31...Band pass filter, 32...Maximum value determination circuit, 33...
latch circuit, 41...D-flip-flop circuit, 42, 43...RS-flip-flop circuit,
44, 45...sample hold circuit, 46...
Comparator, 47...D-flip-flop circuit, 48, 49, 54... Differential circuit, 50, 5
1, 52...AND gate circuit, 53...Overflow detection circuit, 55...Delay circuit.

Claims (1)

[Scope of Claims] 1. In an apparatus in which a pilot signal is recorded by a first rotary head when the tape is stopped and is reproduced by a second rotary head attached to a drive element, the drive element includes a counter and a pilot signal. applying a sweep voltage generated by a digital-to-analog converter and applying the regenerated pilot signal to two sample-and-hold circuits, and applying the outputs of the two sample-and-hold circuits to both inputs of a comparator; Each time the comparator output changes, the sample and hold circuit is alternately switched to the sample mode, and the counter count value at the time of the change in the comparator output is latched. By presetting the count value at the time of the final comparator output change into the counter and continuing to hold that value, the counter count value when the reproduction pilot signal is at its maximum output is stored, and the digital-to-analog converted voltage is sent to the drive element. 1. A height adjusting device for a rotary head, characterized in that the height of two rotary heads is kept substantially the same by supplying the height of the two rotary heads. 2. In the description of claim 1, the recording of the pilot signal is performed by a first control pulse formed by a start signal and a reference clock.
, and a second frequency outside the band of a bandpass filter for extracting the first frequency with a second control pulse formed from the counting end signal of the counter. A rotating head height adjustment device featuring: