JPH0740331B2 - Magnetic recording / reproducing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a helical scan type magnetic recording / reproducing apparatus suitable for recording / reproducing video signals.

[Prior art]

As a recording / reproducing apparatus for video signals, a helical scanning type magnetic recording / reproducing apparatus has come into widespread use in general households. This magnetic recording / reproducing apparatus is one in which two magnetic heads alternately scan the magnetic tape to record and reproduce a video signal one field at a time with each magnetic head. Since the recording method is adopted, a large recording density can be obtained.

By the way, in recent years, much attention has been paid to the integration of a video camera into a helical scan type magnetic recording / reproducing device.
For this reason, it is desired for the helical scan type magnetic recording / reproducing apparatus to realize high quality reproduced images and reduction in size and weight as fundamental requirements.

In order to satisfy these requirements at the same time, under the condition that the recording density is constant, the rotational speed of the head cylinder is increased, the relative speed between the magnetic head and the magnetic tape is increased, and the head cylinder is The method of miniaturization is the best method. However, this method is unsuitable for a two-head helical scan type magnetic recording / reproducing apparatus because the diameter of the head cylinder is increased, which leads to an increase in size even if the image quality is improved.

On the other hand, for a 1-head helical scan type magnetic recording / reproducing apparatus, the head cylinder is used for the video signal 1
If the diameter of the head cylinder is equal to the diameter of the head cylinder of the two-head helical scan type magnetic recording / reproducing apparatus when rotating in a field cycle,
The relative speed between the magnetic head and the magnetic tape is almost doubled to improve the image quality, and when the relative speed between the magnetic head and the magnetic tape is made equal to the relative speed in the two-head helical scan type magnetic recording / reproducing apparatus. The diameter of the head cylinder can be halved and the size can be reduced, which in turn can improve the quality of reproduced images and reduce the size and weight. The same applies to a so-called 1.5-head helical scan magnetic recording / reproducing apparatus that is adopted as a magnetic recording / reproducing apparatus for broadcasting, and in particular, has an auxiliary head for recording / reproducing a vertical blanking period portion of a video signal. .

However, in these 1-head and 1.5-head helical scanning magnetic recording / reproducing apparatuses, even if the above requirements are met, the same magnetic head sequentially scans the magnetic tape. It is impossible to adopt the above method. Therefore, a guard band is inevitably required between recording tracks, and the recording density is lowered. Such a decrease in recording density unduly increases the amount of magnetic tape used, and is not particularly preferable as a magnetic recording / reproducing apparatus for home use.

[Object of the Invention]

An object of the present invention is to provide a helical scan-type magnetic recording / reproducing apparatus capable of obtaining a reproduced image of high quality, small in size and light in weight, and having a high recording density, excluding the above-mentioned drawbacks of the prior art.

[Outline of Invention]

In order to achieve this object, the present invention provides two magnetic heads having head gaps of different azimuth angles at a predetermined angular interval in a head cylinder that makes one rotation for each unit cycle of an input video signal. A signal is time-compressed, and an image signal of at least a unit cycle is alternately provided to each of the magnetic heads for each rotation of the head cylinder and a part of the image of another unit cycle temporally adjacent to this unit cycle. And a recording track on which at least more video signals than the unit period are recorded can be formed without a guard band.

Example of Invention

 First, a basic example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a magnetic tape running mechanism of a magnetic recording / reproducing apparatus according to the present invention, in which 1 is a magnetic tape, input is a tape cassette, 3 is a supply reel, 4 is a take-up reel,
5 is a head cylinder, 6 and 7 are magnetic heads, 8 and 9 are tape guides, 10 is a tension post, 11 is an erasing head, 12, 13 and
14, 15 is a moving tape guide, 16 is a voice / control head, 17 is a pinch roller, and 18 is a capstan.

In the figure, when the tape cassette 2 is not mounted on the magnetic recording / reproducing apparatus, the magnetic tape 1 is fed from the supply reel 3 in the tape cassette 2 to the tape guide 8 on the output side.
When the tape cassette 2 is attached to the magnetic recording / reproducing apparatus and operated in a recording mode, the moving tape guide 1 is wound around the take-up reel 4 along the tape guide 9 on the entry side.
2, 13, 14 and 15 pull out the magnetic tape 1 from the tape cassette 2 and wind it around the head cylinder 5 at a winding angle of about 360 ° (for example, about 300 °). At the same time, the magnetic tape 1 has an erasing head 11, a voice / control head 1
The pinch roller 17 and the capstan 18 are in contact with the pinch 6, and the tension post 10 applies a predetermined tension to the pinch roller 17.

The magnetic tape 1 travels in the direction of arrow A by a driving means including a pinch roller 17 and a capstan 18, and the head cylinder 5
Rotates in the direction of arrow B, and the magnetic heads 6 and 7 alternately record or reproduce for each rotation of the head cylinder 5.

2 (a) and 2 (b) are a plan view and a front view showing the basic structure of an embodiment of the head cylinder portion of FIG. 1, 5a being an upper cylinder and 5b being a lower cylinder. The same reference numerals are given to the parts corresponding to the drawings.

In the figures (a) and (b), the magnetic tape 1 is spirally wound around the outer circumference of the head cylinder 5 in an angle range of 360 °-°, and the winding angle is restricted by the tape guides 13 and 14. There is. Then, the head cylinder 5 rotates in the direction of arrow B, and the magnetic tape 1 runs in the direction of arrow A.

The head cylinder 5 is composed of a rotatable upper cylinder 5a and a fixed lower cylinder 5b. The upper cylinder 5a has magnetic heads 6 and 7 having head gears with different azimuth angles.
In the direction of the axis of rotation of the upper cylinder 5a, with a step difference of a value obtained by multiplying a pitch P of a recording track (not shown) by Θ ° / 360 ° and arranged at an angular interval of Θ °. However, Θ
° is set to be slightly larger than °. The head cylinder 5, and hence the magnetic heads 6 and 7 rotate at a cycle corresponding to one field period of a video signal of the standard system, and at 3600 rpm in the case of the NTSC system.

The magnetic heads 6 and 7 alternately perform a recording or reproducing operation for every one rotation of the head cylinder 5, and the recording or reproducing operation is performed by the magnetic tape 1 in which the head cylinder 5 is moved.
Except for the range of angle Θ ° from point Q to point P, which includes the range of angle θ apart from, the angle 360 ° from point P to point Q at which the magnetic heads 6 and 7 contact and scan the magnetic tape 1 − It is performed over the range of Θ °. In this case, at the time of recording,
The magnetic heads 6 and 7 are respectively supplied with a 1-field video signal during one rotation recording operation, and at the time of reproduction, the magnetic heads 6 and 7 are respectively 1-field video signal during a reproduction operation during one rotation. Is played.

This point will be described in further detail. During recording, a magnetic field 6 is supplied to the magnetic head 6 while the magnetic head 6 travels from the point P to the point Q during one revolution of the head cylinder 5. , The recording track shown in FIG.
19 is formed. When the magnetic head 6 reaches the point Q, recording is stopped, and when the magnetic head 7 reaches the point P, the video signal of the next field is supplied to the magnetic head 7, and when the point Q is reached, the recording is stopped. As a result, a recording track 20 (Fig. 3) is formed. In this manner, the magnetic heads 6 and 7 are alternately recorded between the points P and Q for each rotation, and the magnetic heads 6 and 7 alternately form a recording track in which a video signal of one field is recorded.

Since the magnetic heads 6 and 7 have head gears having different azimuth angles, the recording track formed by the magnetic head 6 and the recording track formed by the magnetic head 7 can be formed so as to partially overlap each other. The width of the recording track is narrower than the track width of the magnetic heads 6 and 7, and the guard band is unnecessary, so that the recording density is increased.

During reproduction, the magnetic heads 6 and 7 reproduce-scan the recording tracks in the magnetization directions matching the respective azimuth angles during the traveling from the point P to the point Q. In this case, since the width of the recording track is narrower than the track width of the magnetic heads 6 and 7, the magnetic heads 6 and 7 scan a part of the adjacent recording tracks at the same time, but the signal reproduction from the adjacent recording tracks cannot be performed due to the azimuth loss. It is suppressed, and even if the magnetic heads 6 and 7 are slightly displaced in the width direction of the recording track, the reproduction output is not reduced.

By the way, one field period of the standard video signal is set to T _f
Then, the magnetic heads 6 and 7 rotate in the cycle of the period T _f , and the period from the midpoint P of one rotation to the point Q, that is, Since a 1-field video signal will be recorded or played back, the standard system video signal must be (360 ° -Θ °) / 360 ° times time-axis compressed during recording. At the time of reproduction, the reproduced video signal
The time axis must be extended by 0 ° / (360 ° -Θ °) times. Moreover, when the magnetic head 7 travels from the point P and reaches the point Q, the magnetic head 6 reaches the point P, and when the magnetic head 6 next travels from the point P and reaches the point Q, the magnetic head 7 is reached. Yes, it has not yet reached point Q, and it must rotate an additional 2Θ ° in order for it to reach point P, for which reason the magnetic heads 6, 7 are at points for one revolution of the head cylinder 5. The temporal position of the recording or reproducing operation period from P to the point Q is different. Therefore, it is necessary to set the supply timing of the video signal of one field to the magnetic heads 6 and 7 during recording or to make the video signals from the magnetic heads 6 and 7 continuous during reproduction.

FIG. 4 is a block diagram showing an embodiment of a recording / reproducing circuit in the magnetic recording / reproducing apparatus according to the present invention for performing such recording or reproducing operation of the magnetic heads 6 and 7, wherein 21 is an input terminal and 22 is an input terminal. Time axis conversion circuit, 23 is frequency modulation circuit, 24 and 25 are gate circuits, 26 and 27 are recording amplification circuits, 2
8, 29 is a preamplifier circuit, 30 and 31 are gate circuits, 32 is an adder circuit, 33 is a frequency demodulator circuit, 34 is a tack signal generator, 35 is an output terminal, and 36, 37, 38 and 39 are switching switches. Therefore, the parts corresponding to those in FIGS. 2A and 2B are designated by the same reference numerals.

Next, the operation of this embodiment will be described.

In FIG. 4, the video signal of the standard system is supplied from the input terminal 21 to the time axis conversion circuit 22.

As described above with reference to FIGS. 2 (a) and 2 (b), the video signal of the standard system having the one-field time _Tf is brought into contact with the magnetic tape 1 during one rotation of the magnetic heads 6 and 7 to scan. Point from P to Q
Must be recorded within the period (360 ° −θ °) · T _f / 360 °. Therefore, the time base conversion circuit 22 can change the supplied video signal to (360 ° −θ °) / 360 °. The time axis is compressed at a rate of.

The time axis conversion circuit 22 is configured by, for example, a memory device such as a random access memory, an analog-digital conversion circuit, a digital-analog conversion circuit, and the supplied video signal is converted into a digital signal and written in the memory device. Furthermore, writing speed of 360 ° / (360 ° -Θ °)
Reading is performed at double reading speed (360 ° −Θ
°) / 360 ° times time-axis compressed digital signal is obtained, and this is digital-analog converted to obtain the time-axis compressed analog video signal. A tack signal synchronized with the rotational phase of the magnetic heads 6 and 7 from the tack signal generator 34 is supplied to the time axis conversion circuit 22, and the video signal of the video signal is generated at the timing described in FIGS. 2 (a) and 2 (b). So that the recording will take place
The time axis conversion circuit 22 is controlled to set the read timing of the time axis compressed video signal.

The video signal from the time axis conversion circuit 22 is supplied to the frequency modulation circuit 23.
Is modulated by and is supplied to the gate circuits 24 and 25. The gate circuits 24 and 25 operate in synchronization with the task signal, and the magnetic head 6
The gate circuit 24 opens while traveling from point P to point Q (Fig. 2 (a)), and the magnetic head 7 is moved from point P to point Q at the next rotation.
The gate circuit 25 is opened during traveling up to, and alternately opened for each field of the time axis compressed video signal. For this reason, the video signals are alternately supplied to the recording / amplifying circuits 26 and 27 every other field, and the video signals are amplified and are respectively supplied to the magnetic heads.
Supplied to 6,7.

Next, the reproducing operation will be described.

The switching switches 36, 37, 38, 39 are closed to the contact P side, and the magnetic heads 6, 7 reproduce and scan the recording tracks in the magnetization direction matching the azimuth angle, and therefore the preamplifier circuits 28, 29.
Is alternately supplied with video signals that are compressed every other field for time. These video signals are amplified and supplied to the gate circuits 30 and 31, respectively. The gate circuits 30 and 31 operate in synchronization with the tack signal from the tack signal generator 34, the magnetic head 6 travels from the point P to the point Q (Fig. 2 (a)), and the recording that matches the azimuth angle is recorded. The gate circuit 30 is opened while the track is reproduced and scanned, and the magnetic head 7 travels from the point P to the point Q in the next rotation, and the gate circuit 31 is reproduced while the recording track matching the azimuth angle is reproduced and scanned. open. Therefore, only the desired video signal passes through the gate circuits 30 and 31. The video signals that have passed through the gate circuits 30 and 31 are added by the addition circuit 32, demodulated by the frequency demodulation circuit 33, and supplied to the time axis conversion circuit 22.

The time axis conversion circuit 22 is controlled by the tack signal from the tack signal generator 34, and its memory device writes the supplied video signal at a writing speed equal to the reading speed at the time of recording, and at the same time (360 °
Read at a read speed of −Θ °) / 360 ° times. Therefore, at the output terminal 35, a video signal which is expanded by 360 ° / (360 ° −Θ °) times in the time axis, that is, the same time axis as in the standard system is obtained.

As a memory device of the time axis conversion circuit 22 necessary for performing the time axis compression / expansion as described above, the memory capacity required for storing a video signal of at least one field is 2θ °.
The memory capacity should be the value obtained by multiplying / 360 °.

The time axis compression of the video signal and the supply timing to the magnetic heads 6 and 7 when using the memory device having such a memory capacity will be described.

In FIG. 2 (a), when a point Q'having an angular interval Θ ° is set on the side opposite to the point P with respect to the point Q, the magnetic head 6
Therefore, the rotational phase of the head cylinder 5 is synchronized with the standard type video signal so that the time when the magnetic head 7 is at the point Q'is the start point of one field for the standard type video signal. ing. Then, at this point, the memory device starts writing the 1-field video signal,
When the magnetic head of the magnetic heads 6 and 7 to be recorded reaches the point P, the memory device starts reading the field.

The time base compression operation and the read timing by the memory device will be described in more detail with reference to FIGS. 5 (a) and 5 (b). Note that FIG. 5 (a) is a standard format video signal supplied to the memory device from the input terminal 21 (FIG. 4), and FIG. 5 (b) is a time-axis compressed image from the memory device. Signals 40 to 45 are standard video signal fields, and 40 'to 45' are time-axis compressed fields.

Now, after the magnetic head 6 reaches the point Q and the magnetic head 7 reaches the point Q ', the field 40 of the video signal (simply the field 40
Say. The same shall apply hereinafter) is written in the memory device, and the field 40 is written in sequential addresses.

When the last address of the memory device is written,
Writing is continued after returning to the first address, and at the same time when the magnetic head 7 reaches the point P, at the same time from the first address of writing, the reading speed, that is, 360 ° of the writing speed.
Reading is started at a reading speed of / (360 ° -Θ °) times. Then, writing and reading are repeated in the memory device so that reading at high speed follows writing. Therefore, the field 40 is obtained from the memory device as the field 40 'which is time-axis compressed by (360 ° -Θ °) / 360 ° times, and this field 40' is supplied to the magnetic head 7 as described above. To be done.

When the magnetic head 7 reaches the point Q ', the writing of the entire field 40 is completed, and then the memory device starts writing the field 41 from the next address. At this point, the magnetic head 6 is at point Q, and the memory device has T _f · θ
The last part of the field 40 corresponding to a period of ° / (360 ° -Θ °) is left unread, and this part is all read while the magnetic head 7 rotates from the point Q'to the point Q.

When the magnetic head 7 reaches the point Q, all reading of the field 40 is completed. At this point, the magnetic head 6 is at point P and the memory device has the first T _f · θ ° of field 41.
The part of the period of / 360 ° has been written, and the reading of the field 41 from the first address of writing is started. When the writing to the final address is completed, the writing is performed from the first address, and the writing and the reading are repeated in the memory device so that the reading at a high speed follows the writing. Therefore, the field 41 is (360 ° −Θ °) / 360 ° from the memory device.
A double-time-compressed field 41 'is obtained, and this field 41' is supplied to the magnetic head 6 as described above.

When the magnetic head 6 reaches the point Q, all the reading of the field 41 from the memory device is completed, and at the same time, from the address next to the address where the field 41 is written to the next field.
Start writing 42. When the magnetic head 7 reaches the point P, the reading of the field 42 is started, and the field 42 is read.
The time-field-compressed field 42 'is obtained and supplied to the magnetic head 7.

As described above, the read timing of the memory device is set at the positions of the magnetic heads 6 and 7. As described above, the read timing is set by the tack signal from the tack signal generator 34.

In this case, as is clear from FIG. 5 (b), the video signal obtained from the memory device is composed of the field 40 'supplied to the magnetic head 7 and the field 41' supplied next to the magnetic head 6. It is continuous, but between the field 41 'and the field 42' which is supplied to the magnetic head 7 next,
There is a ΔT interval. As described above, this is the period required for writing while the magnetic head 7 travels from the point Q ′ to the point P after the completion of reading the time-axis-compressed video signal supplied to the magnetic head 6. ΔT = 2 · T _f · θ ° / 360 °. That is, in other words, the memory device compresses the video signal of the standard system every two fields, and thus every one frame.

Next, regarding the time base expansion operation by the memory device,
The description will be given with reference to FIGS.

The relative timing of each field of the video signal reproduced by the magnetic heads 6 and 7 depends on the magnetic heads 6 and 7 during recording.
Since it can be regarded that the relative timings of the respective fields supplied to the time axis are the same, FIG. 5 (b) shows the time axis compressed video signal supplied to the memory device of the time axis conversion circuit 22. , FIG. 5 (c) shows a time-expanded video signal from the memory device. 40 ″
Through 45 "are time-extended fields of fields 40 'through 45', respectively.

Now, assuming that the magnetic head 7 is reproducing a recording track in the magnetization direction that matches the azimuth angle while the magnetic head 7 is traveling from the point P to the point Q, the memory device, as in the case of recording, has a field. Write 40 ', and at the same time,
The writing speed (360 ° −
Read at a read speed of Θ °) / 360 ° times. Then, writing and reading are repeated so that the reading follows the writing at a slow speed, and when the magnetic head 7 reaches the point Q, the field by the magnetic head 7 is reached.
40 'playback is completed. However, at this time, since the last period of T _f · θ ° / (360 ° -θ °) of the field 40 ′ is not read out and remains, this remaining portion is from the point Q to the point P of the magnetic head 7. Is read during the running period.
In this way, a time-extended field 40 'of field 40' is obtained from the memory device.

On the other hand, at the time point when the magnetic head 7 reaches the point Q, the magnetic head 6 is at the point P, and during the traveling period from the point P to the point Q, the magnetic head 6 has the next magnetization direction matching the azimuth angle. The recording track is reproduced and scanned, and the field 41 'is reproduced. This field 41 'is written from the next address of the memory address at the end of the field 40', and when the magnetic head 6 reaches the point P'with an angular interval Θ ° in the rotational direction from the point P, the reading of the field 41 'is performed. Be started.

Then, as described above, the writing and reading of the field 41 'are repeated, and when the magnetic head 6 reaches the point Q, the writing of the field 41' is completed, and further, the magnetic field 6 reaches the point P '. The reading of 41 'continues. Therefore, a time-extended field 40 ″ of field 41 ′ is obtained from the memory device.

When the magnetic head 6 reaches the point P ', the magnetic head 7 is located at the point P, and the magnetic head 7 reproduces the field 42' from this point, and thereafter, the fields 42 ", 43", 44 expanded in the same manner as the time axis. ″, 45 ″, ……… is obtained.

Needless to say, the video signal of FIG. 5 (c) that has been expanded in the time axis is a standard video signal.
Further, FIG. 5 (d) shows a tack signal.

For example, if Θ ° = 60 °, 1/6 of the head cylinder 5
Since the rotation period is not recorded, the compression ratio α of the standard video signal becomes 5/6. This will increase the frequency of the video signal by a factor of 1.2, but it is a value that can be sufficiently achieved by improving the magnetic tape, magnetic head and the like.

In this case, the memory capacity of the memory device of the time axis conversion circuit 22 may be one that can store 1/3 video signal of one field of the standard system. Assuming that the video signal is sampled at 10 MHz and written to the memory device as an 8-bit digital signal, the memory capacity of this memory device is In other words, it only needs to be 56 kbytes, which can be realized with today's memory technology without being so expensive. In this case, the read speed at the time of recording is 1.2 times the write speed, and vice versa at the time of reproducing.

As described above, in this basic example, the rotational speed of the head cylinder is increased as compared with the magnetic recording / reproducing apparatus of the two-head helical scan system. Therefore, from the relationship between the relative speed between the magnetic head and the magnetic tape, It is possible to reduce the diameter of the head cylinder, and the magnetic recording / reproducing apparatus can be reduced in size and weight while maintaining the quality of the reproduced image in a good state, and the azimuth recording system can be adopted. Therefore, the recording density can be increased and recording / reproduction can be performed without any loss of the video signal.

As is clear from FIGS. 5 (a), (b), and (c), when an audio signal is recorded in the longitudinal direction of the magnetic tape, the audio signal and the reproduced video signal are separated from each other. To ΔT
However, this time lag is slight and does not cause any particular problem. Incidentally, when the compression ratio α is 5/6, ΔT is about 3 msec.

In the above basic example, the standard system video signal may be a video signal for broadcasting or a video signal from a video camera, but especially in a magnetic recording / reproducing apparatus incorporating a video camera. By recording a video signal from the video camera, the video camera is caused to perform a special scan, so that the time axis compression of the video signal at the time of recording can be omitted.

Therefore, another basic example of the magnetic recording / reproducing apparatus according to the present invention configured as described above will be described.

A video camera can be considered as a kind of memory device,
The scanning is synchronized with the rotation of the magnetic heads 6, 7 (Fig. 2 (a)). And, the scanning speed is (360 ° −) of the period required for one frame scanning period for two rotations of the magnetic heads 6, 7.
Θ °) / 360 ° times the speed, and the scanning is paused by ΔT (−2 · T _f · θ ° / (360 ° −Θ °) every frame. From
As shown in FIG. 5 (b), a time axis compressed video signal is obtained. This video signal can be directly supplied to the frequency modulation circuit 23 shown in FIG. 4, and at the time of reproduction, it is processed by the reproduction system shown in FIG. 4 and a standard system video signal is obtained at the output terminal 35.

The above scanning of the video camera can be achieved by a simple modification of the deflection system when a normal vidicon is used, and in the case of a solid-state image pickup device, a method of scanning the picture elements is slightly different. It is self-evident that you can change it. Also,
If the scanning pause period of ΔT is sufficiently short, no particular unnaturalness appears in the reproduced moving image.

By the way, the recording track pattern (FIG. 3) formed on the magnetic tape according to the above basic example is a recording track formed by a conventional two-headed helical scan system home magnetic recording / reproducing apparatus adopting the azimuth recording system. The pattern can be exactly the same as that of No. 1 and the formed recording track can be reproduced by the above-mentioned home magnetic recording / reproducing apparatus. That is, if the diameter and lead angle of the head cylinder in the above basic example are φ and Θ _{o, respectively,} and the diameter and lead angle of the head cylinder in the above home magnetic recording / reproducing apparatus are φ ′ and Θ ′ _o , respectively, and Φ and Θ _o may be set so that However,
The right side of the equation (1) has a negative sign when the scanning direction of the magnetic head and the running direction of the magnetic tape are the same, and a positive sign when the magnetic head is in the opposite direction.

Further, v _{t is} the running speed of the magnetic tape f _{v is the} field frequency α is the compression ratio.

Therefore, considering the 2-hour mode of the so-called VHS system video tape recorder for home use, φ ′ = 62mm Θ ′ _o = 5 ° 56′7.4 ″ v _t = 33.35mm / sec f _v = 59.94 (NTSC system) Therefore, if α = 5/6, then φ = 37.167 mm Θ _o = 5 ° 58′22 ″. Therefore, the diameter of the head cylinder in the above basic example can be reduced to about 60% of the head cylinder in a VHS type video tape recorder, and the video signal from the video camera incorporated into the head cylinder can be recorded. The recorded track can be played back on a VHS video tape recorder.

A magnetic recording / reproducing device with a video camera integrated into it
It is an important issue that it is small and lightweight and convenient to carry when taking an image, and this can be achieved by the present invention from the above.

The basic example of the present invention has been described above. Next, examples of the present invention based on the basic example will be described.

6 (a), (b) and (c) are timing charts for explaining an embodiment of the magnetic recording / reproducing apparatus according to the present invention, in which 41,4243 are overlap recording signals and _TF is one frame. period, T _o is Obaratsupu recording period, [Delta] T 'is between the following如期, FIG. 5 (a), (b),
The parts corresponding to (c) are given the same reference numerals.

Normally, in a two-head helical scan type magnetic recording / reproducing apparatus, the same video signal is partially overlap-recorded between adjacent tracks so that the influence of the change in the magnetic head switching position does not appear on the reproduction screen. There is. That is, in the overlap recording, one magnetic tape scanning period of each magnetic head is set longer than one field period of the video signal, and the video signal is recorded on each recording track more than one field. Is something that
In each recording track, the beginning portion thereof records the end portion of the field of the video signal recorded in the preceding recording track for one field, and the trailing end portion corresponds to one field in the succeeding recording track. The beginning of that field of the recorded video signal is recorded. in this way,
The start and end portions of the recording track where the end portion and the beginning portion of the video signal of the field recorded on the adjacent recording track are recorded are called the overlap recording area of the recording track. When the magnetic recording head scans such an overlap recording area, the other recording head simultaneously scans the overlapping recording area in which the same video signal of the recording track adjacent thereto is recorded. The same video signal is recorded and reproduced. When such a period is called an overlap period, as long as a reproduction signal is switched from one magnetic head to another magnetic head during this overlap period during reproduction, even if the head switching time fluctuates, The reproduction signal from the magnetic head is continuously connected, and there is no effect of fluctuations at the head switching time.

However, in the basic example described above with reference to FIG. 5, after recording on the magnetic head 6 (FIG. 2 (a)) is completed,
Since the lacking period of the period ΔT is provided, the overlap recording is not performed.

That is, in the basic example described above, the video signals supplied to the magnetic heads 6 and 7 are compressed in the time axis for each field as described above, but the magnetic heads 6 and 7 are magnetic tapes. Each time one scan is performed, one field is recorded. Therefore, as will be described with reference to FIG. 3, the video signals are recorded only on a field-by-field basis on each of the sequential recording tracks 19 and 20 formed on the magnetic tape 1, and no overlap recording area is formed. Therefore, overlap recording is not performed.

The examples are intended to perform Obaratsupu recording within a period corresponding to the period ΔT of Figure 5, set the Obaratsupu period T _o for each frame of FIG. 6 (a), the period T The same video signal in _o is recorded in two adjacent recording tracks.

As described above, a random access memory is used as the memory device of the time axis conversion circuit 22 of FIG. 4, and its memory capacity is the memory capacity of the memory device of the basic example described with reference to FIG. By multiplying T _F + T _o ) / T _F times, the recording / reproducing circuit of FIG. 4 can be used.

On the other hand, the timing of writing each field to the memory device and the timing of reading each field are slightly different from those in the above-mentioned basic example.

FIG. 7 schematically shows the head cylinder portion in order to explain each timing of such a memory device, and the portions corresponding to FIG. 2 (a) are denoted by the same reference numerals.

In FIG. 7, a point P ″ having an angular interval δ from the point P in the direction opposite to the rotational direction B of the head cylinder 5, and a point Q from the point Q in the direction opposite to the rotational direction B of the head cylinder 5 and the forward direction, The points Q ″ and Q at the angular intervals δ ′ and δ are determined. The video signal of one field between points P and Q is read out from the memory device and recorded by the magnetic head 6 or 7 as in the previous embodiment, but the memory device of each field is read. The writing start time is the time when the magnetic head 6 is at the point Q ″. The magnetic heads 6 and 7 are magnetic so as to scan a magnetic tape (not shown) at least while traveling from the point P ″ to the point Q. Tape head cylinder 5
Winding angle (360 °-°) with respect to (Fig. 2 (a))
Is set.

Therefore, referring also to FIGS. 6A and 6B, when the magnetic head 6 is located at the point Q ″ and the field 40 is written in the memory device and the magnetic head 7 reaches the point P, The field 40 is read out at high speed and the field 40 'which is time-axis compressed by the magnetic head 7 is recorded. When the magnetic head 6 reaches the point Q ", the writing of the next field 41 is started, but the field 40 Magnetic head 7
Continues until point Q is reached.

When the magnetic head 7 reaches the point Q, the magnetic head 6 has reached the point P, the memory device starts reading the field 41, and the time-field-compressed field 41 'is supplied to the magnetic head 6. When the magnetic head 6 reaches the point Q ″, the memory device starts writing the next field 42.

When the magnetic head 6 reaches the point Q, the reading of the field 41 is completed. Further, while the magnetic head 6 travels from the point Q to the point Q, the field 42 written in the memory device is read. Therefore, magnetic head 6
A time-field-compressed field 41 'and a part of the field 42 time-axis-compressed overlap recording signal 42 are supplied to and are recorded on the same recording track.

Next, when the magnetic head 7 reaches the point P ″, the memory device reads the number of addresses read while the magnetic head 7 travels between the points P ″ and P, rather than the first address where the field 42 is written. Read ahead from the address where the preceding field 41 is written, and the magnetic head 7 is at the point P.
Field is reached, reading of the field 42 is started.

That is, the memory device returns to the preceding predetermined address and starts reading, and the reading of the field 42 is performed in a period until the magnetic head 7 reaches the point Q. While the magnetic head 7 travels from the point P ″ to the point Q, the time-axis-compressed overlap recording signal 41 and the field 42 ′ of a part of the preceding field 41 are read out from the memory device. It is supplied and recorded on the same recording track.

Thereafter, the fields of the memory device are similarly written and read, and the magnetic heads 6 and 7 form the recording track including the overlap portion.

During reproduction, for example, the magnetic head 6 moves from the point P to the point Q.
Field 41 'and the overlap recording signal are written to the memory device, and the next magnetic head 7 scans the overlap recording signal 41 from the point P "to the point Q.
And field 42 'are written and read out by jumping from the address written in field 41' to the address next to the address in which the overlap recording signal of the information content corresponding to this is written. By jumping from the address where the recording signal 42 is written to the address next to the address where the field 42 'of the corresponding information content is written, the continuous original standard shown in FIG. A system video signal is obtained.

As described above, in this embodiment, since it is possible to perform the overlap recording although it is performed for each frame, it is possible to approximate the track pattern by the conventional magnetic recording / reproducing apparatus of the two-head helical scan system.
It is possible to greatly prevent the influence of the change in the switching position of the magnetic head during reproduction.

In this case, at the time of reproduction, as described in the basic example above, reproduction can be performed by the conventional magnetic recording / reproducing apparatus of the two-headed helical scan method, and in any case, the overlap recording portion exists. Therefore, the reproduced image is not affected by the change in the magnetic head switching position.

Incidentally, in this embodiment, Obaratsupu recording period T _o
Is sufficiently smaller than one frame period T _F , the memory capacity of the memory device increases only slightly even if the overlap recording is performed.

Also in the embodiment shown in FIGS. 6 and 7, similar to the case of the basic example described above with reference to FIG. 5, the same operation is performed by being integrally combined with the video camera for special scanning. Further, the formed recording track can be made reproducible by a conventional two-headed helical scan type magnetic recording / reproducing apparatus.

〔The invention's effect〕

As described above, according to the present invention, the number of revolutions of the head cylinder can be increased, and recording / reproduction can be performed without missing the video signal. Therefore, the diameter of the head cylinder can be made sufficiently small. It is possible to achieve a significant reduction in size and weight while improving the image quality without deteriorating the image quality of the reproduced image. Moreover, the azimuth recording method is possible. It has a high recording density, and in particular, when incorporating a video camera into one unit, it is possible to fully satisfy the essential requirements of ultra-compact size and light weight, and to make it compatible with the conventional two-headed helical scan magnetic recording and reproducing device. In addition, there is a portion where overlap recording is performed between adjacent tracks formed on the magnetic tape, and there is a change in the switching position of the head during reproduction. Effect be one that can be eliminated, it is possible to provide a magnetic recording and reproducing apparatus of the prior art, if not superior functionality.

[Brief description of drawings]

FIG. 1 is a structural view showing a magnetic tape running mechanism in a magnetic recording / reproducing apparatus according to the present invention, and FIGS. 2 (a) and 2 (b) are plan views showing the basic structure of an embodiment of the head cylinder portion of FIG. , A front view, FIG. 3 is a pattern diagram showing a recording track on a magnetic tape, FIG. 4 is a block diagram showing an embodiment of a recording / reproducing circuit in a magnetic recording / reproducing apparatus according to the present invention,
5 (a), (b), (c), and (d) are timing charts showing one specific example of the operation of the time base conversion circuit of FIG. 4, and FIGS. 6 (a), (b), (). c) is a timing chart for explaining one embodiment of the magnetic recording / reproducing apparatus according to the present invention, and FIG. 7 is a schematic for explaining the position of the magnetic head with respect to the write / read timing of the time axis conversion circuit in the embodiment. It is a figure. 1 …… Magnetic tape, 5 …… Head cylinder, 6,7 …… Magnetic head, 21 …… Input terminal, 22 …… Time axis conversion circuit, 2
4,25,30,31 …… Gate circuit, 34 …… Tac signal generator,
35 …… Output terminal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Shibata Akira Shibata, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Home Appliance Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-49-131107 (JP, A) Sho 53-45216 (JP, A)

Claims (1)

[Claims] 1. A magnetic recording / reproducing apparatus in which a video signal is recorded in each successive recording track formed in a diagonal direction of the magnetic tape, wherein the magnetic tape is 1 in every unit cycle of an input video signal. Around the circumference of the rotating head cylinder is approximately equal to 360 ° (360 ° −
a first magnetic head mounted on the head cylinder and traveling at a predetermined angle relative to the first magnetic head. A second magnetic head that is arranged ahead of the rotation direction by an interval θ ° (where θ °> ψ °) and has a head gap with an azimuth angle different from that of the first magnetic head; and the input video signal. The input video signal is time-axis-compressed so that the unit period of is equal to the (360 ° -θ °) rotation period of the first and second magnetic heads, and every other one of the head cylinders. In the rotation period of, the rotation period is (360 ° −θ ° + δ °) from the preset first rotation position within the period in which the first magnetic head scans the magnetic tape (however, 360 ° 1 unit that is time-axis compressed over −θ ° ＋ δ ° <360 ° −ψ °) A video signal of one unit period, which is the terminal part of the video signal of the first period and which is required for the first magnetic head to rotate by an angle δ °, and which is followed by a time-axis-compressed video signal of one unit period. 1 time-axis compressed video signal is output, and in every other rotation period of the head cylinder, it is within the period in which the second magnetic head scans the magnetic tape from the first rotation position. Angle δ °
From the second rotation position rotated only by (360 ° −θ ° + δ
Angle), the time axis-compressed video signal of one unit cycle and the subsequent time-axis-compressed video signal of one unit cycle, which is the starting end portion of the second magnetic head, are angled. a circuit for outputting a second time-axis compressed video signal consisting of a portion of a period required to rotate by δ °; and the first cylinder for every other rotation period of the head cylinder.
The time-axis compressed video signal of is supplied to the first magnetic head,
Means for supplying the second time-axis compressed video signal to the second magnetic head for every other rotation period of the head cylinder, and recording is performed by the first magnetic head. The end portion of the first time-axis compressed video signal is the time axis of the second time-axis compressed video signal recorded by the second magnetic head during the immediately preceding rotation period of the head cylinder. The start portion of the second time-axis compressed video signal which is the same partial video signal as the end portion of the compressed video signal of one unit cycle and which is recorded by the second magnetic head is the head cylinder. The same partial video signal as the beginning portion of the time-axis-compressed video signal of one unit period in the first time-axis compressed video signal recorded by the first magnetic head during the next rotation period of Magnetic recording / reproducing device characterized by .