JPS5840246B2 - magnetic playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic reproducing device (hereinafter referred to as a VTR) that reproduces video signals recorded on a magnetic tape using a rotating magnetic head, and particularly relates to a magnetic reproducing apparatus (hereinafter referred to as a VTR) that reproduces video signals recorded on a magnetic tape using a rotating magnetic head. It is an object of the present invention to provide a magnetic reproducing device suitable for so-called auto-tracking, which allows a rotating magnetic head to accurately scan a recording track where the recording order of the recording tracks does not match.

Generally, in order to improve recording density, tape speeds in VTRs are reduced to half of the speeds that have been standardized up to now.

By the way, in the case of standardized tape speeds, the recording order of the horizontal synchronization signals of adjacent tracks is made to match, but if the tape speed is simply halved, the recording order of the horizontal synchronization signals described above will be misaligned. come.

As a result, the rotary magnetic head no longer scans the recording track accurately, resulting in a decrease in reproduction output due to track deviation, and the occurrence of jitter and skew distortion.

The present invention eliminates the drawbacks of the conventional apparatus, and provides a magnetic reproducing apparatus equipped with so-called auto-tracking, which allows a rotating magnetic head to accurately scan a recording track.

The magnetic reproducing device of the present invention will be described below with reference to drawings of embodiments.

FIG. 1 is a block diagram of a rotating magnetic head drum device and a magnetic tape running system of a magnetic reproducing apparatus according to the present invention, as well as a block diagram of an electric circuit.

In FIG. 1, the recorded magnetic tape 1 is driven in the direction of an arrow 60 by a capstan 24 (driving source is a motor 26 and a pinch roller 26 at a predetermined speed).

On the other hand, the rotating magnetic head drum device 2 is provided with a normal servo as described below.

That is, as the magnetic tape 1 runs, the control signal recorded on the control track 61 is reproduced from the control head 21.

In this control track 61, a rectangular wave signal having a frame period of a normally recorded video signal is recorded.

Therefore, the recording rectangular wave signal is differentiated and reproduced from the control head 21.

Of this differentiated rectangular wave signal, only the positive pulse (or negative pulse) is amplified by the amplifier 22 and applied to the variable delay circuit 23 .

This variable delay circuit 23 is a so-called tracking shifter in a normal VTR, and tracking is performed by adjusting the amount of delay of this variable delay circuit 23.

Now, the output of this variable delay circuit 23 is applied to the phase comparator 19.

Further, the rotational phase pulse of the rotary head obtained from the fixed head 6B of the rotary magnetic head drum device 2 is applied to the phase comparator 19 via the amplifier 16.

Therefore, the phase comparator 19 → the drive circuit 1 including the phase compensation circuit
8 → drum motor 20 → rotating shaft 7 → rotating drum 3 → rotational phase detection mechanism of permanent magnet 8 attached to rotating drum 3 and fixed head 7 → amplifier 16 → phase control loop of phase comparators 1 and 9 is formed Therefore, the rotary heads 4 and 5 rotate in synchronization with the control signal reproduced from the control head 21. Tracking can be achieved by changing the delay time of the variable delay circuit 23 using this phase control.

The above-mentioned tracking method is commonly used in small VTRs, etc., but here, the above-mentioned tracking is made so that the rotary head can scan the recording track more accurately.

First, the recording track pattern of the magnetic tape 1 will be explained.

FIG. 2 is a recording track pattern diagram, and as described above, the recording positions of horizontal synchronizing signals on adjacent tracks are shifted.

This figure shows the case where the inclination angle of the gap of the magnetic head is zero in order to make this deviation easier to understand.

Actually, as shown in FIG. 3, adjacent tracks have different inclination angles.

This recording method is called azimuth recording, and is often used when recording without providing a guard band and without gaps.

As mentioned above, in the case of the recording pattern in Fig. 1 at normal tape speed (when recording is performed at twice the track pitch in Fig. 2, that is, at a pitch of 2P), the horizontal synchronizing signal recording position of the adjacent track is Matches as shown in Figure 4.

In the case shown in FIG. 4, the difference in the horizontal synchronizing signal arrangement between adjacent tracks is 1.5H (H is the horizontal synchronizing signal period).

On the other hand, as shown in Figure 2, when the tape speed is halved, the pitch becomes P, and the difference in the arrangement of adjacent horizontal synchronizing signals is half of the above-mentioned 1,5H, or 0.75.
It becomes H.

Therefore, the difference in the recording positions of adjacent horizontal synchronization signals is 0.
It will be 25H.

When reproducing the magnetic tape 1 recorded in this manner, a rotating magnetic head having a track width equal to or larger than the recording track width is used as shown in FIG.

The same rotating magnetic head may be used for recording as well.

The reason for this is that during recording, part of the track is recorded twice.

That is, the previously recorded portion is erased by the later recorded signal, so that only the later recorded portion remains.

Now, if a magnetic tape having the track pattern shown in FIG. 2 is reproduced by the above-mentioned rotating magnetic head, signals as shown in FIGS. 5a and 5b will be obtained.

The signals in FIGS. 5a and 5b are shown as the output signals of the amplifiers 12 and 13 including the gate circuit shown in FIG. are added to the amplifiers 12 and 13.

The amplifiers 12 and 13 include flip-flops 17 (hereinafter referred to as Fj
A gate signal from F17) is added.

Since the rotational phase signals of the rotary magnetic heads 4 and 5 obtained from the fixed magnetic heads 6A and 6B described above are added to F and F17, the rotational phase signals of the rotary magnetic heads 4 and 5 obtained from the fixed magnetic heads 6A and 6B are added from F and F17.
A square wave gating signal is obtained indicating one field while 5 is in contact with the magnetic tape.

Therefore, by this gate signal, signals as shown in FIGS. 5a and 5b are obtained at the outputs of the amplifiers 12 and 13.

Next, the signals obtained from the amplifiers 12 and 13 are transferred to the mixer 1
4, resulting in a continuous signal as shown in FIG. 5C.

The signal from the rotating magnetic head thus obtained is then passed through a low-pass filter 30 and a high-pass filter 29.
added to.

A frequency-modulated luminance signal is obtained from the high-pass filter 29 and demodulated by the demodulator 31.

The demodulated video signal is applied to the horizontal synchronization signal separation circuit 35, and a horizontal synchronization signal as shown in FIG. 6d is obtained.

On the other hand, a low-pass converted color signal is obtained from the low-pass filter 30.

This signal is 3.58 MH, the Japanese and American standard television signal.
It is applied to a converter 33 for converting the z color signal subcarrier signal into a centered carrier color signal.

This converter 33 also includes a circuit for removing phase fluctuations of the carrier wave, but since it is not directly relevant here, the explanation will be omitted.

It is assumed that the output of the converter 33 is a carrier color signal as shown in FIG. 6a, which is locked to the phase of the 3.58 MHz (color signal subcarrier) oscillator 32 and has no phase fluctuation.

Now, the carrier color signal obtained in this manner also includes the track signals recorded on the above-mentioned adjacent tracks, that is, the crosstalk signal.

Furthermore, as shown in FIG.
The phase of the subcarrier of IH is alternately inverted (in the figure, φ
0 and φ1800.

). The recording method shown in FIG. 3 is a method for eliminating color signal crosstalk between adjacent tracks, but here this crosstalk is detected and tracking is performed.

A method for detecting this crosstalk will be described below.

In FIG. 1, in the color signal including crosstalk obtained from the converter 33, the phase of the color subcarrier of the signal in every other field is inverted every 1H as described above, so this must be corrected. No.

For this purpose, the color signal obtained from the modulator 33 is first applied to the gate circuit 37, and the color signal portion having a phase of 00 is gated.

On the other hand, in order to restore the color signals having a phase difference of 180°, the phase is inverted by a phase inverter 36, and the portion where the phase becomes 00 is gated by a gate circuit 38.

When the output signals of the gate circuits 37 and 38 are mixed in a mixer 40, a color signal containing a crosstalk signal whose subcarriers are aligned in phase is obtained.

Note that the gate signals applied to the gate circuits 37 and 38 are obtained by a gate signal generation circuit 39.

This gate signal generation circuit 39 receives the horizontal synchronization signal from the horizontal synchronization signal separation circuit 35 described above, and F.

A rectangular wave signal of every other field of F17 is added.

Therefore, gate signals as shown in FIG. 7a and b are obtained from the gate signal generation circuit 39, and the gate signal in FIG. 7a is sent to the gate circuit 38, and the gate signal in FIG. Added.

FIG. 1C shows a gate signal that is inverted every IH.

Further, it is assumed that gating is performed when the signal is at H level.

The color signal containing crosstalk thus obtained is sent to an IH delay line 41 that delays the IH period signal, a phase inversion circuit 42,
and level adjuster 44.

The output of the phase inversion circuit 42 is further applied to a level adjuster 43.

The output obtained from each level adjuster 44 and 43 is adjusted to be equal to the color signal level obtained from the IH delay line 41.

The color signals thus obtained are mixed in a mixer 45 and a mixer 46.

By mixing the input and output signals of the IH delay line 41 in this manner, a color signal with crosstalk removed is obtained from the mixer 45, and a crosstalk component is obtained from the mixer 46.

IH delay line 41. Phase inverter 42, level adjuster 44.
43, and mixers 45 and 46 is called a comb filter, and has characteristics as shown in FIG.

In FIG. 8, the solid line indicates the characteristic obtained in the mixer 45 (C-shaped filter), and the dotted line indicates the characteristic obtained in the mixer 41 (Y-shaped filter). .

Now, the crosstalk-free color signal obtained from the mixer 45 (see FIG. 6) is applied to the mixer 34, where it is mixed with the luminance signal described above, and a composite video signal is output from the terminal 47. can get.

If a monitor television receiver is connected to this terminal 4T, the reproduced image can be observed.

On the other hand, the crosstalk component (sixth
(see FIG. C) is applied to gate circuit 50 and gate circuit 53.

The gate circuits 50 and 53 are supplied with the horizontal synchronizing signal (FIG. 6e, which is obtained by delaying the horizontal synchronizing signal shown in FIG. 6d in the delay circuit 48 and the delay circuit 49).

Since the gate signal shown at f is applied, only the crosstalk burst signals are taken out from the outputs of the gate circuits 50 and 53, as shown at g and h in FIG.

In FIG. 2, the crosstalk of the track to the right of the scan track is the signal shown in FIG. 6g, which lags the phase of the scan track burst.

Further, the crosstalk of the track on the left side of the scanning track is the signal shown in Figure 6, which is ahead of the burst signal of the scanning track in phase.

The respective burst signals obtained in this way are applied to rectifier circuits 51 and 54, and further applied to hold circuits 52 and 55 that hold the peak voltage of the burst,
Hold the mold pressure for 1H.

The DC voltage thus obtained indicates the direction and amount of track deviation.

That is, it shows that the rotating magnetic head is shifted in the direction where the amount of crosstalk is large, and the amount indicates the distance of the shift.

As described above, when the track width of the rotating magnetic head is equal to or larger than the recording width, track scanning is performed best when the amount of crosstalk on both sides is equal.

Therefore, by applying the voltages obtained from the hold circuits 52 and 55 to, for example, the differential amplifier 56 and comparing the voltages, a control signal proportional to the amount of deviation, which changes to positive or negative depending on the direction of the deviation, can be obtained.

In this way, the control signal obtained from the above-mentioned differential amplifier 56 moves an electro-mechanical conversion element, which will be described later, to perform tracking.

By the way, as mentioned above, tracking is performed by adjusting the delay time of the variable delay circuit 23 in FIG. 1, but when the recording track is curved as shown by the solid line A in FIG. In this case, if the rotary head scans as shown by the dotted line (straight), track deviation will naturally occur in some parts, and the reproduction output of the rotary head will decrease in some parts.

It is impossible to enable the rotating magnetic head to accurately scan such a curved recording track by adjusting the delay time of the variable delay circuit 23 described above.

Therefore, the rotary head is moved directly from this point to accurately scan the recording track.

As described above, the recording track pitch P and the track width T of the magnetic head are different, and it is preferable to have the following relationship in consideration of recording and reproduction.

That is, although the condition of T≧P has been described above, the condition of 2P>T may also be 3P>T during reproduction.

However, at the time of recording, data is recorded in duplicate or triply, so 2P>T must be satisfied.

(See Figure 10) Now, let's talk about the electro-mechanical conversion element that moves the rotary head.

FIG. 11 is a perspective view showing the structure of the drum 3, the electro-mechanical conversion element 73 attached thereto, and the rotary head 4.

This electro-mechanical conversion element 73 is made by gluing piezoelectric elements 65 and 67 together as shown in FIG.

A gold or silver vapor deposited film 64.66.6B is attached to the surface of this piezoelectric element 65.67.

The piezoelectric element 65 uses the vapor deposited films 64, 66.6B as electrodes.
．． The polarization directions of the bonding surfaces of 67 are opposite to each other (the bonding surfaces are the vapor deposited film 66 and the center electrode).

) can be used as an electro-mechanical conversion element.

That is, if this bonded piezoelectric element 73 is fixed to the rotating drum 3 with the screw 63 together with the piezoelectric element retainer 62 made of metal, it becomes a cantilever beam with the part 70 as a fulcrum.

Furthermore, a lead wire T1 is attached to this center electrode 66, and this electrode 66 and one electrode of the slip ring 28 shown in FIG. 1 are connected with a lead wire 71.
is connected to the other electrode of the slip ring 28 with a lead wire (not shown), and the slip ring 10 and the brush 11 are connected to each other using a lead wire (not shown).
When a voltage is applied between the electrodes of the electro-mechanical transducer 73 (between the electrode 66 and the drum 3-earth), the tip of the piezoelectric element moves in the direction shown by arrow 69 in FIG.

This movement is due to the electrostrictive effect of the piezoelectric elements 65 and 67.

This bonded piezoelectric element 73 (-electrical-mechanical conversion element)
The electrode 6 is connected by the piezoelectric element holder 62 and the screw 63 described above.
4 and the electrode 68 are electrically connected, the same voltage in the same direction is applied between the center electrode 66 and the electrode 64 and between the center electrode 66 and the electrode 68.

However, as described above, since the polarization directions are opposite, for example, if the piezoelectric element 65 extends in the direction to the right of the arrow 72, the piezoelectric element 67 will contract in the direction to the left of the arrow 72.

Therefore, the rotary head 4 attached to the tip of the bonded piezoelectric element 73 moves in the downward direction of the arrow 69.

If an applied voltage opposite to the above is applied, the rotary head 4 will move in the upward direction of the arrow 69.

From the above, tracking can be achieved by applying the output of the differential amplifier 56 to the electro-mechanical conversion element 13 via the transmission mechanism of the brush 11 and slip ring 10.

A mixer 57 and a DC bias source 58 located between the differential amplifier 56 and the brush 11 move the electro-mechanical conversion element 73 in a fixed direction, and the output of the differential amplifier 56 described above moves the electro-mechanical conversion element 73 in a fixed direction. It was designed to be kept under control.

That is, applying a DC bias to the electro-mechanical conversion element 73 by the mixer 57 is equivalent to operating the variable delay circuit 23 described above, but it is convenient for fine adjustment.

As described above, the present invention is suitable for so-called auto-tracking, which enables a rotary head to accurately scan a track recorded without gaps, and is suitable for so-called auto-tracking, in which a rotary head is attached to an electro-mechanical transducer and a curved It is also possible to accurately scan the recording track.

In addition, the method for detecting track deviation is accurate, and since the detection is performed for each horizontal line, the response is good.Furthermore, the circuit can be shared with the video demodulation circuit, and its industrial value is extremely high.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the magnetic reproducing device of the present invention;
Figures 2, 3 and 4 are magnetic recording pattern diagrams recorded on the magnetic tape, Figures 5, 6 and 7 are diagrams of the magnetic recording patterns recorded on the magnetic tape.
Fig. 8 is a frequency characteristic diagram of the circuit block in Fig. 1, Fig. 9 is a diagram of a curved magnetic track pattern, No. 10 is an explanatory diagram of tracing, Fig. 11 is a diagram of the signal waveform of each circuit block in the figure. A perspective view of the structure of the electro-mechanical conversion element, Fig. 12a
12 is a plan view thereof, and FIG. 12 is a front view thereof. 1... Magnetic tape, 2... Rotating magnetic head device, 41... IH delay line, 44...
...Phase inverter, 46...Mixer, 50, 53
...Gate, 51, 54... Rectifier circuit, 52, 55... Hold circuit, 56...
...Differential amplifier, 73...Electro-mechanical conversion element.

Claims (1)

[Claims] 1. A rotating magnetic head having a track width equal to or wider than the width of the above-mentioned recording track is helically scanned over a recording track in which the horizontal synchronization signals of adjacent tracks recorded without any gaps do not match. At the same time, crosstalk signals from adjacent tracks of the main scanning track mainly scanned by the rotating magnetic head are detected to obtain a signal indicating the relative positional relationship between the recording track and the rotating magnetic head. It is configured to control an electro-mechanical transducer that moves the rotary magnetic head to perform tracking, and the signal for controlling the electro-mechanical transducer to obtain tracking is a main scanning signal mainly scanned by the rotary magnetic head. A magnetic reproducing device characterized in that it is configured to detect crosstalk from adjacent tracks based on the playback time and level of a burst portion of a color signal.