JPS6217283B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating head type magnetic recording/reproducing device such as a video tape recorder, and in particular, the present invention relates to a rotating head type magnetic recording/reproducing device such as a video tape recorder, and in particular, to a rotating head type magnetic recording/reproducing device such as a video tape recorder. The present invention relates to a magnetic recording/reproducing device that allows tapes to be played back on one side.

In recent years, the popularity of video tape recorders (hereinafter referred to as VTRs) for general home use has been increasing.
Since each company uses different recording and playback methods, a major drawback is that video tapes (also called video software) recorded using a certain method cannot be played back on VTRs using other methods. As a result, there are inconveniences such as a narrower selection of video software and the inability to freely exchange video tapes between individuals.Furthermore, this reduces the consumer's desire to purchase video tapes. This has become a major obstacle to industrial development.

The present invention has been made in view of the above circumstances, and even between VTRs with different recording methods, especially between VTRs with different diameters of the rotation locus circles of the magnetic heads,
The object of the present invention is to provide a magnetic recording and reproducing apparatus that can reproduce magnetic tapes recorded using other recording methods.

First, before explaining the present invention, looking at general household VTRs currently on the market, there are four types that are particularly known: Betamax, VHS, V-code, and VX (all registered trademarks). There is. These all use a 1/2 inch wide magnetic tape and use a rotating video head to sequentially record diagonally parallel recording tracks on the magnetic tape, but the shape of the cassette and the size of the tape The running speed, the number of video heads, the diameter of the rotation locus circle of the video heads (diameter of the guide drum, rotary disk, etc.), signal processing method for recording and reproducing video signals, etc. are different. In the present invention,
Correcting the difference in the inclination angle of the recording track caused by the difference in the diameter of the rotation locus circle of the video head,
Furthermore, it is an object of the present invention to provide a magnetic recording and reproducing apparatus that can also correct fluctuations in the horizontal synchronizing signal that inevitably occur due to this correction.

Hereinafter, preferred embodiments of the present invention will be described.
This will be explained with reference to the drawings. Here, two methods, X and Y, are set as recording and reproducing methods for the VTR, and both methods are recorded and reproduced using a two-head rotating magnetic head device 10 as shown in FIG. The diameter of the rotation locus circle (or rotating disk 2, guide drums 3, 4, etc.) is
74.487mm, Y method is 62.000mm. At this time,
Recording track T of each method on the magnetic tape 5
(or the inclination angle of the tracking trajectory U of video head 1) is 5° in the X method.
01′25.8″, Y method is 5°58′09.9″.

First, the rotating magnetic head device 10 shown in FIG. 1 will be schematically explained. Such a rotating magnetic head device 10 has a rotating disk 2 that rotates in the direction of arrow A.
At the lower position, guide drums 3 and 4 fixed to the chassis of the VTR or the like are arranged. The magnetic tape 5, which is a magnetic recording medium, is guided by being wound diagonally (in a shape that becomes part of a spiral) around the guide drums 3 and 4 over an angular range of just over 180 degrees, and is driven to run in the direction of arrow B. be done. The rotating disk 2 is driven to rotate in the direction of arrow A by a motor 6, and two video heads 1 are attached near the periphery of the rotating disk 2 with an angular difference of 180 degrees from each other. There is. The tip of the video head 1 slightly protrudes from the outer peripheral surface of the guide drums 3 and 4, and magnetically records and reproduces video signals while making sliding contact with the magnetic tape 5. Alternatively, instead of using the rotary disk 2, either the upper or lower guide drums 3, 4 may be rotated, and the video head 1 may be attached to this.

FIG. 2 shows the recording track T recorded on the magnetic tape 5 in this way. In the figure, arrow A indicates the tracking direction of the video head 1, and arrow B indicates the running direction of the magnetic tape 5. There is.
In the following explanation, a case will be explained in which the magnetic tape 5 recorded in the Y method is reproduced by the X method VTR. That is, the recording track T _Y is recorded in the Y system, and the tracking locus U _X (see broken line) shows the trajectory when the X system video head 1 moves without correction. Also, in either method, one field is recorded and reproduced on one recording track.

In order to track the recording track T _Y magnetically recorded in the Y method using the video head 1 of the X method VTR, as shown in FIG. It may be supported by a bimorph plate 7.

That is, in FIG. 3, the bimorph plate 7 is made of two plates (piezoelectric plates) made of a piezoelectric material such as BaTiO ₃ , a solid solution of PbZrO ₃ and PbTiO ₃ , or a piezoelectric organic polymer material. It is constructed by bonding these together and forming electrodes on both sides of the outside, and the direction and amount of curvature are determined according to the direction and intensity of the electric field caused by the electric signal applied to these electrodes. It is. By attaching the video head 1 to one end of the bimorph plate 7 and fixing the other end to the rotary disk 2 etc. via the head base 8, the video head 1 is mounted in the direction of the rotation axis of the rotary disk 2, that is, in the direction of the rotation axis of the rotary disk 2. On the magnetic tape 5 shown in FIG. 2, it can be displaced in the direction of arrow C, which is approximately the width direction of the recording track T. In this case, the maximum amplitude of video head 1 is 1.5898 mm, and the maximum amplitude of video head 1 is 1.5898 mm.
Assuming that the displacement is 0 at the center of the recording track T _Y as shown in the figure, it is sufficient to displace the video head 1 by ±0.7949 mm. Bimorph plates 7a, 7b supporting each video head 1a, 1b shown in FIG.
Just apply it to . At this time, each bimorph plate 7
a and 7b are controlled independently, and in order to avoid transients, for example, at the end of the tracking period of the video head 1a, the voltage applied to the bimorph plate 7a supporting this head 1a is adjusted to the displacement at the start of tracking. It is preferable to quickly return the voltage to such a level that the next tracking can be carried out smoothly. The same applies to the bimorph plate 7b that supports the video head 1b.

Next, even if such tracking correction is performed, the video head 1 also tracks on an extended line that deviates from the recording track _TY , such as from point P to point Q in FIG. During the tracking period, there is no signal for about 10% at the start and end, and in the remaining 80%, all the video signals within one vertical scanning period (one field), that is, 262.5 horizontal scanning periods (262.5H ^* ) will be compressed and played. Here, the frequency _H ^* of the reproduced horizontal synchronization signal is _H ^* = 74.487/62.000 _H = 1.2014 _H , which is approximately 20% higher frequency, when the frequency of the regular horizontal synchronization signal is _H. becomes.

In this way, it is necessary to reinsert at least the horizontal synchronizing signal for the missing portions of the video signal that occur at 10% of each of the start and end portions within one tracking section. This can be done, for example, by inserting a periodic signal synchronized with a horizontal synchronizing signal for obtaining a reference signal in the rotating servo system of the rotating magnetic head into the missing portion as a pseudo horizontal synchronizing signal. Alternatively, as shown in FIG. 5, in the vicinity of the tracking start position or end position of the video head 1 where the above-mentioned dropout occurs, the video signal can be reproduced by tracking another adjacent recording track _TY (see the shaded area). A horizontal synchronizing signal may be obtained by this method, and this signal may be reinserted into the missing portion.

When playing back the video signal obtained in this way on a general television receiver, a good playback image cannot be obtained because the frequency _H ^* of the horizontal synchronization signal is about 20% higher than the regular one. . If you want to return this to the regular horizontal synchronization frequency _H , the simplest way is to convert all of 262.5H ^* for one field to 20%.
However, this requires a memory element that can store one field, which is expensive.

Therefore, each horizontal scanning period H ^* of the reproduced video signal is made to have a regular length by sequentially expanding each of the 5H ^* out of 6H ^* without extending the time axis of all 262.5H ^* . That is, as shown in FIGS. 6A and 6B, the reproduction video signal A is
By expanding each of 5H ^* of the 6H ^* periods by 20% and thinning out the remaining 1H ^* , a video signal B of a regular horizontal scanning period H is obtained. Therefore, for the obtained video signal B, there is no video signal during the 21.875H period at the start and end of one field, and only the horizontal synchronization signal H with a regular period exists, and the 21.875H period at the center of the field is 21.875H. The period of
There are a video signal and a horizontal synchronization signal obtained by time-axis expanding the reproduced video signal. Furthermore, the reproduced image of the television receiver appears as shown in the hatched area in FIG. 7, with 10% no-signal areas occurring at the top and bottom of the screen. In this case, the image in the shaded area has a vertical resolution of 5/6 and is shrunk in the vertical direction by 5/6 from the normal aspect ratio.

Next, in order to maintain the normal aspect ratio of the screen, it is necessary to shrink the image in the horizontal direction as well, and this ratio is 20%. This takes advantage of the fact that the playback video signal as it is (before time axis expansion) has already been time axis compressed by 20% compared to the regular one. Without decompression, as shown in Fig. 8, the signals every 1H ^* are converted by O, T _D , 2T _D , 3T _D , 4T _D , respectively.
For example, the delay is caused by switching fixed delay lines, and these five signals are arranged in 6H ^* periods (see FIGS. 8A and 8B). At this time, if the horizontal synchronization signal remains in the same position, the image will be biased toward the left side of the screen, and a 20% no-signal portion will appear on the right side. Therefore, if the external horizontal synchronizing signal shown by the broken line in Figure 8B is shifted to the front position by about 10% of 1H, 10% of the signal will be placed at each end of the horizontal direction as shown in Figure 9. The no-signal part of is placed.

In other words, as shown in Figure 9, the screen obtained by the above video signal processing has a no-signal area of about 10% in both the horizontal and vertical directions around the screen, and the remaining horizontal and vertical areas. In both cases, images can be obtained in approximately 80% of the area (shaded area). This video part has approximately 219 scanning lines, which is the normal number of scanning lines.
Although it is fewer than 262.5 lines, it does not look grainy because the image plane is almost proportionately smaller.

Next, an example of a circuit configuration for performing such signal processing will be described with reference to FIG.

In FIG. 10, the reproduction output from the magnetic heads 1a and 1b attached to the rotary disk 2 etc. is transmitted to an amplifier 12 via a switching circuit 11.
is being sent to. This switching circuit 11 receives the output from a pulse generator 13 that detects the rotation of the rotary disk 2, etc. and generates pulses, and sends the output from a pulse generator 13 to a duty switch by a head switching control circuit 14 such as a monomulti.
An output converted to a 50% square wave (frequency is equal to the rotation speed of the rotating disk 2, etc., 30 Hz) is supplied, and only the output from the magnetic head 1 that is in contact with the magnetic tape is transmitted to the next stage. is sent to amplifier 12.
As shown in FIG. 11A, the reproduction output from this amplifier 12 is within about 80% of the normal 1V period.
The signal includes the video signal (shaded area) of 262.5 horizontal scanning periods, and this horizontal synchronization signal H
As mentioned above, the frequency _H ^* of ^* is 1.2014 times the normal frequency _H. In order to make this reproduction signal have the same period as the regular horizontal synchronizing signal, 5H of 6H is sequentially O, T _D , 2T _D , 3T _D , 4T _D
and delay. This means that four delay elements with delay time _TD , for example CCD15, 16, 17, 18
are connected in series, and these CCDs15, 16, 17,
18 and the output from the amplifier 12 are supplied to the switching circuit 19, and switching is performed sequentially at a regular H cycle. Here, as a delay element, a BBD or the like can be used in addition to a CCD. In addition, the above delay time T _D
is H ^* /5 (=H/6), and the amplifier 12,
Of course, the outputs from the CCDs 15, 16, 17, and 18 have delay times of O, _TD , _2TD , _3TD , and _4TD, respectively. Therefore ^, when numbers 1 _to 6 are sequentially assigned to each H ^* in 6H ^* as shown in FIG. After being extracted, the signal of the first H ^* section of the next 6H ^* is extracted with a delay time of 0, so the signal of the 6th H ^*
The signals in this section will be thinned out (see FIGS. 11B and 11C).

The horizontal synchronization signal H ^* of the reproduced output from the amplifier 12 is separated by a synchronization separation circuit 20 and sent to a phase comparison circuit 21. This phase comparator circuit 21 is supplied with a signal obtained by dividing the output from a VCO (voltage controlled oscillator) 22 which oscillates at a frequency of 5 _H ^* (≒6 _H ) by 1/5 using a frequency divider 23 (the frequency becomes _H) . ) is input, and the phase is compared with the reproduced output H ^* signal, and an error signal corresponding to the phase difference is sent to the VCO 22. Therefore, VCO2
2 outputs a signal synchronized with the reproduced output H ^* signal (however, the frequency is 5 _H ^* ), and this signal is divided by 1/6 by the frequency divider 24 to almost the normal H signal frequency.
The signal becomes _H , and this is sent to the switching circuit 19.

Next, the CCDs 15, 16, 17, and 18 are supplied with a clock signal from an oscillator 25 that oscillates at a high frequency. Generally, this clock signal has a higher frequency than the highest frequency of the video signal delayed and transmitted by each CCD 15, 16, 17, and 18. Also, this clock signal is passed through the frequency divider 2.
By dividing the frequency by 6, a pulse having a period of a regular horizontal scanning period (frequency _H ) is obtained, which is further divided by a frequency divider 27 and used as a reference signal for the rotation servo system. That is, the reference signal from the frequency divider 27 is sent to the phase comparison circuit 28, where it is phase-compared with the signal from the head switching control circuit 14, and an error signal corresponding to the phase difference is sent to the motor 6 via the amplifier 29. is sent as a control signal to Further, the pulse of frequency _H from the frequency divider 26 is made into a pseudo-horizontal synchronizing signal via a monomulti 30 or the like, and is reinserted into the no-signal portion of the reproduced output. This can be done, for example, by switching between the output of the switching circuit 19 and the output of the monomulti 30 or the like using the changeover switch 31. This changeover switch 31 operates in one field cycle (frequency 60Hz),
For example, the switching operation is controlled by a control circuit 32 which outputs a pulse of a predetermined width at 60 Hz in accordance with the output from the dividing period 27. Therefore,
The output from the changeover switch 31 is as shown in FIG. 11D.

Furthermore, in order to arrange the position of the reproduced image on the screen in the center, it is only necessary to change the horizontal synchronization signal. It is sufficient to supply the signal to the circuit 34 and replace the H pulse shown in FIG. 11D with a signal as shown in FIG. 11E. The horizontal synchronization signal generation circuit 33 may be a circuit that processes (for example, delays the phase) the H-period signal from the frequency divider 24 or the frequency divider 26 using a monomultiplier or the like. .

As is clear from the above explanation, between VTRs with different recording methods such as the X method and Y method, for example, a magnetic tape recorded in the Y method can be played back on a VTR of the X method to obtain an image. . Therefore, the range of video software that can be used is expanded, and recording tapes can be freely exchanged between individuals without being restricted by the VTR system. In addition, for every predetermined number of horizontal periods of the reproduction signal, for example 6H ^* , other predetermined number of horizontal periods, for example 1H ^* , are removed or thinned out, and the remaining 5H ^* signal is used as a regular horizontal synchronization signal. Since it is configured to synchronize with CCD15,1
The delay time of the delay elements such as 6, 17, 18, etc. or the storage capacity of the temporary storage element can be small, and it can be supplied at low cost.

It should be noted that the present invention is not limited to the above embodiments; for example, only one of the reinsertion of the missing portion of the reproduced signal and the replacement of the horizontal synchronization signal may be performed. In addition, a separate oscillator with frequency _H is installed to generate the horizontal synchronization signal to be reinserted.
It is also possible to adopt a configuration in which the signal is obtained from this oscillator. In addition, a magnetic tape recorded using the X method can be transferred to a magnetic tape recorded using the Y method.
It goes without saying that reproduction on a VTR can be performed by substantially the same signal processing as in the embodiment, and in addition, the present invention can generally perform signal correction processing due to the fact that the rotation locus circles of the video heads are different from each other.

[Brief explanation of the drawing]

The drawings are all for explaining embodiments of the present invention, and FIG. 1 is a schematic perspective view showing a rotary head section of a video tape recorder, and FIG. 2 is a plan view showing a recording track and a tracking locus on a magnetic tape. Figure 3 is a perspective view showing a rotary disk equipped with a video head, and Figures 4A and B
5 is a plan view of a magnetic tape to explain an example of tracking. FIGS. 6A and 6B are time charts showing an example of signal processing of a reproduced signal. 7 is a front view showing the reproduced image on the screen of the television receiver after the signal processing in FIG. 6; FIGS. 8A and 8B are time charts showing other examples of signal processing of the reproduced signal;
9 is a front view showing the reproduced image after the signal processing in FIG. 8; FIG. 10 is a circuit diagram showing an example of the circuit configuration;
11A to 11F are time charts showing output waveforms at each point A to F in FIG. 10. 1...Video head, 2...Rotating disk, 5
...Magnetic tape, 7...Bimorph board, 15,1
6, 17, 18... CCD, 19... Switching circuit, 23, 24, 26, 27... Frequency divider, 3
1... changeover switch, 34... amazing changeover circuit.

Claims (1)

[Scope of Claims] 1. A magnetic recording and reproducing device that performs magnetic recording and reproducing by rotating a magnetic head while drawing a locus circle of a predetermined diameter, in which the magnetic head is supported via an electro-mechanical transducer element, and the magnetic head is When reproducing a magnetic tape recorded using another magnetic recording/reproducing device having a rotation locus circle having a different diameter, the magnetic head is displaced in the direction of the axis of rotation to track the recording track. magnetic recording and reproducing device. 2. A magnetic recording and reproducing apparatus according to claim 1, characterized in that a horizontal synchronizing signal is reinserted into a missing portion of a reproduction signal from one recording track. 3. The magnetic recording and reproducing apparatus according to claim 2, wherein the reinserted horizontal synchronizing signal uses a reference signal used for rotation servo of the rotary head. 4. In the magnetic recording and reproducing device according to claim 1, a signal obtained by removing signals of a predetermined number of horizontal periods of the reproduction signal from the magnetic head at a period of a predetermined number of horizontal periods, A magnetic recording/reproducing device characterized in that it is configured to be synchronized with a regular horizontal synchronization signal.