JPS623482B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses at least one rotary head to detect an original signal, such as a video signal including an audio signal;
The present invention relates to a magnetic recording/reproducing device that records information on a recording medium and reproduces the same. Conventionally, the structure of a helical scan video tape recorder (hereinafter referred to as a VTR) using a rotating head means and a long strip magnetic tape is generally known and will not be described in detail. 1 and 2 are 180 relative to rotation center 3
They are indexed at the same time and installed at the same height on the same rotation plane. The magnetic tape 6 is guided and regulated by the guide poles 4 and 5 to the cylinder tape guide 1 which is rotationally driven in the direction of the arrow 7.
1 shows the configuration of a rotating two-head type VTR that is guided in a spiral over approximately 180 degrees and is run in the direction of arrow 8. The magnetic tape 6 runs at a predetermined speed, and the rotating head rotates at a frame period (1/30) of the video signal to be recorded.
SEC), the video signal trajectory that is scanned and recorded on the tape is discontinuous recording magnetization that tilts in the longitudinal direction of the tape surface with the center of the trajectory as shown by the solid line 9 on the tape surface in Figure 2. Draw a trajectory. Thus, it can be seen that approximately one field of the television signal is sequentially recorded and reproduced in parallel as one continuous recording magnetization locus. In conventional recording systems, it has been common knowledge that the rotary head is driven at the same rotational speed during both recording and reproduction. Further, advances in various technologies in VTRs have significantly improved recording density, and the trend is for even higher density recording to continue in the future. This increase in recording density is accompanied by a decrease in magnetic tape speed.
This will result in a reduction in the playback head output. Therefore, if the recording density is increased and the playback head output is reduced, and the playback head output is no longer at a level with sufficient margin against equipment noise, it becomes difficult to ensure playback image quality. . The present invention aims to solve the above-mentioned problems, and aims to improve the S/N ratio by improving the reproduction head output and expanding the signal bandwidth, thereby obtaining excellent image quality. Therefore, the rotational speed of the rotary head during reproduction is higher than that during recording. Below, the configuration of the present invention will be explained in detail using the drawings. The present invention, for example, in a rotating two-head type VTR having the configuration shown in FIG. A video signal is recorded using the same speed, and during playback, it is driven at, for example, twice the speed of recording, that is, 3600 rpm. This will be explained using FIG. 3 showing one embodiment. FIG. 3 shows the configuration of a drive control system that provides two types of rotational speeds for the cylinder 10 in which the rotary heads 1 and 2 are installed, a drive control system that feeds the magnetic tape 6 at a desired speed, and a video signal recording and reproducing system. FIG. A DC motor is generally used as the cylinder motor 11. A cylinder servo system is constructed using a speed control system 12 for rotating the motor at a constant speed and a phase synchronization control system 13 for synchronizing the phase with an external reference signal. The speed control system 12 includes a frequency generator (F.
G.) 14, FG amplifier 15, flip-flop (FF) 16, 17, speed changeover switch 18,
It is composed of a speed reference monomulti (MM) 19, a gate circuit 20, a filter 21, and a motor drive amplifier 22 that drives the cylinder motor 11.
The phase control system 13 includes a rotational pulse generator (PG) 23 that detects the rotational phase of the rotational cylinder, a PG amplifier 24, a phase comparator 25, a gain-phase compensation filter circuit 26, and an external reference signal input signal changeover switch 27. It is comprised of a supplied reference signal generator 28 and a video signal input terminal 29. The speed control system 12 has a conventionally known configuration, but to briefly explain, the FG signal from the FG 14 is amplified by the FG amplifier 15 and converted into a square wave with a period ratio of 50%-50% by the FF 16. However, if the output signal of the FG amplifier 16 is obtained as a square wave with a period ratio of 50%-50%, a configuration in which the FF 16 is removed may be used. F.
F.17 is for further dividing the output signal of FF16 into 1/2 frequency, and the output of FF17 is connected to the terminal P of the speed changeover switch 18, FF1
The outputs of 6 are connected to terminal R, respectively, and the outputs of the next stage are
Guided to MM 19 and gate circuit 20,
Since the FG signal passing through the switch 18 is controlled to always have a constant frequency, the cylinder motor 11 is
speed (e.g. 1800 rpm), and a second speed (double speed, e.g. 3600 rpm) when connected to P. The filter 21 smoothes the AND gate pulse width based on the speed comparison in the gate circuit 20, and controls the cylinder motor 11 at a constant speed through the motor drive amplifier. On the other hand, in the phase synchronization control system 13 , during recording, the rotational frequency of the cylinder motor and the vertical synchronization signal in the video signal to be recorded inputted from the terminal 29 are separated in the synchronization separation circuit 30, and then in the flip-flop circuit (FF) 31. Pulse signal whose frequency is divided by 1/2 (30
Hz) and PG amplifier 24 so that they match.
Occurs every rotation of the cylinder whose width is increased by
The PG signal from the PG 23 is compared with the phase comparator 25, and the phase comparison output is passed through the gain-phase compensation circuit 26 to modulate the time width of the MM 19.
Phase synchronization control is performed. Further, a pulse signal of 30 Hz obtained by frequency-dividing the vertical synchronizing signal is connected to the recording amplifier circuit 32 and the R terminal of the changeover switch 33, and is recorded on the edge of the tape by the control head 34. On the other hand, during playback, the speed control system 12 uses as an input signal a signal obtained by passing the output signal of the FF 16 to the FF 17 and dividing the frequency by 1/2, which is obtained through the P terminal of the changeover switch 18.
The phase synchronization control system 13 performs speed control to obtain double the rotation speed, that is, 3600 rpm, and the reference signal generator 28
By using the 60Hz from PG23 as a reference input signal for one side of the phase comparator 25 through the changeover switch 27, and adding the PG signal from PG23 as the other reference signal, a phase synchronization drive of twice the 60Hz standard, that is, that during recording, is achieved. let it happen. Next, the tape feed drive system will be explained. This system is used to maintain a constant tape feed speed during recording, and to perform tracking control to trace the video recording locus during playback. That is, the magnetic tape 6 is driven while being pressed against the capstan shaft 35 and a pinch roller (not shown). A drive mechanism includes a flywheel 36, a belt 37, a pulley 38, and a DC capstan motor 39. The configuration of the drive circuit system is similar to the drive system of the cylinder motor 11, using a speed control system 40 for rotating the capstan motor 39 at a constant speed, and using phase synchronization control to achieve phase synchronization with an external reference signal. system 41 . The speed control system includes a frequency generator (FG) 42 that detects the rotation speed of the capstan motor 39, an FG amplifier 43, and an F.
F.44, speed reference monomulti (MM) 45, gate circuit 46, filter 47, and motor drive amplifier 48. The phase synchronization control system 41 is
A frequency dividing circuit 49 that divides the frequency of FF44 into 1/m (m is an integer), a changeover switch 50, and a phase comparison circuit 5
1. Gain-phase compensation circuit 52, control signal amplifier 53, changeover switch 54, 1/2 frequency divider circuit 55, reference signal generator 28, 1/2 frequency divider circuit 31, synchronous separation circuit 30, video signal to be recorded and an input terminal 29. The control system has the same concept as the cylinder control system, and to briefly explain its functions, the speed control system controls the speed so that the signal frequency of the FG42 is constant during both recording and playback, and the phase synchronization control system 41 During recording, the vertical synchronization signal is separated from the video signal to be recorded as the reference input signal of the phase comparator 51.
A 30Hz pulse signal with a frequency divided by 0.1/2 is applied through the R terminal of the changeover switch 54, and as a reference signal, the 1/2 frequency divider 44 signal of the FG42 is applied at a desired rotation speed of 1/m so that the frequency is 30Hz. Phase synchronization control is achieved by applying a signal whose frequency has been divided by 49 (m: an integer) through the R terminal of the changeover switch 50. As the reference input signal to the phase comparator 51 during reproduction, a 30 Hz pulse signal obtained by dividing the frequency of the reference signal generator (60 Hz) by 1/2 by the flip-flop FF 55 is applied through the P terminal of the changeover switch 54, and as a reference signal, The 30 Hz pulse signal recorded at the end of the magnetic tape 6 during recording is reproduced by the control head 34, and the signal amplified by the control amplifier 53 is transmitted through the P terminal of the changeover switch 33 to the P terminal of the changeover switch 50. It is applied through a terminal to perform phase synchronization control. That is, during recording, the capstan motor 39 is driven and controlled based on the vertical synchronization signal standard of the video signal to be recorded so as to obtain a desired number of rotations, and is configured to obtain a constant tape feeding speed of a predetermined speed, and during playback, the capstan motor 39 is driven and controlled based on the vertical synchronization signal standard of the video signal to be recorded, so as to obtain a desired rotation speed. The tape feeding speed is controlled so that the signal generator 28 and the reproduction control signal have a specific phase relationship. As is conventionally known,
This is a tracking control system that causes the rotary head to follow the recording locus (FIG. 2, 9) of the rotary head during reproduction. With the drive configuration described above, during recording, a video signal to be recorded is input from the terminal 29, processed by the video signal recording circuit system 56 including FM modulation means, etc., and transmitted through two rotary transformer means (not shown). Information is recorded on the magnetic tape every alternate half revolution through the rotating magnetic heads 1, 2. During playback, the rotary head is driven twice as much as during recording, as described above, and the time axis is changed from that during recording through the playback signal processing circuit system 57 including FM detection means.
Time axis expansion circuit system 58 for the signal compressed to 1/2
By expanding the data twice, a reproduced signal substantially the same as that at the time of recording is obtained. Next, in order to make the reproduced signal substantially the same as the recorded signal when a video signal is recorded using the drive configuration shown in FIG. It is necessary to solve two problems: tracking servo deviation and B: the time axis of the reproduced signal is compressed twice. To explain the state of tracking deviation in A using FIG. 4, the center of the recording magnetic trajectory is drawn by a solid line 9 as shown in FIG. If the scanning center trajectory in this case is drawn with the scanning start position 62 aligned with the recording magnetization trajectory center position, there will be two scanning trajectory center lines as 60 and 61 for one magnetization trajectory 9. In scanning, the magnetization locus is shifted by 1/2 pitch in the longitudinal direction of the tape 6 at the scan end position, and furthermore, in the second scan, it is shifted by 1/2 pitch at the scan start position and by 1 pitch at the end position. However, if the recorded signal can track the entire trajectory in the first reproduction scan, all recorded information can be obtained, and the reproduction signal in the second scan is essentially unnecessary even if trajectory 9 can be tracked. It is something. As a method of compensating for the tracking deviation as described above, there is a method of correcting the diagonal winding angle of the magnetic tape around the cylinder tape guide by the amount of the tracking deviation arrow 64 during playback, and a method of rotating magnetic tape which has recently been put into practical use. A method of controlling the bias through an electro-mechanical transducer consisting of a piezoelectric element or the like by laminating the head in a direction perpendicular to the scanning direction - one example is JP-A-49-9919 (Applicant: Matsushita Electric Industrial Co., Ltd. )
The basic concept of making it possible to reproduce still, slow motion, quick motion, etc. known as VTRs by changing the tape feed speed during recording and playback is now in its original form. Since this method can be applied to solve the above-mentioned problem A in the invention, it will not be described in detail here. In the explanation of the present invention, an example was explained in which the speed of the rotary head is doubled during playback, but the invention is not limited to this.
If 3x speed playback is applied, the track deviation in one scan described above will be reduced to a maximum of 1/3 pitch, and this can be achieved when using the azimuth recording method, which has been put into practice recently, in which the gap directions of the rotary heads 1 and 2 are different from each other. It is possible to eliminate crosstalk from adjacent tracks, and there is a characteristic that it can be realized without necessarily applying the above-mentioned tracking compensation. Next, regarding the above-mentioned item B, that is, during playback in this embodiment,
It is necessary to expand the playback signal, which has been time-axis compressed to 1/2, to 2 times. As shown in Fig. 5, the time width of the video signal A during recording is compressed to 1/2 as shown in B, if we pay attention to only one scan playback at double speed playback. A time axis expansion circuit system that expands the same length as the original recorded signal ( Fig.
8) needs to be introduced. The reproduced video signal processing circuit will be described in more detail. In FIG. 6, the signal reproduced from the magnetic head 1 (or 2) is demodulated by the demodulation circuit 57 , and the output is a reproduced video signal whose time axis is compressed to 1/2, and the time axis expansion circuit 58 . In the time axis expansion circuit 58, the input video signal is guided to a synchronization separation circuit 58-1, and the separated horizontal synchronization signal is sent to a phase synchronization oscillator (PLL) 58-2.
A clock signal with a frequency of ₁ , which is phase-synchronized with the horizontal synchronizing signal of the reproduced video signal, is obtained. This clock signal ₁ has a high frequency of, for example, about 21 MHz, and it is desirable to select a frequency that can sufficiently transmit a video signal whose time axis is compressed to 1/2 by sampling it. This clock pulse is led to the gate circuit 58-3, and the gate circuit operates repeatedly so that the clock pulse is gated for one field period of the time-compressed reproduced video signal, and the clock pulse is blocked for the next one field period. A clock pulse passing through this gate circuit 58-3 is guided to an A/D converter 58-4, which converts the reproduced video signal introduced to this input into a digital signal. The video signal converted into a digital signal is sent to a memory circuit 58.
-5 and is written to memory by a clock signal gated by gate circuit 58-3. Immediately after being written, the signal is read out continuously using the signal (frequency _1/2 ) from the reference clock oscillator 58-6, and is led to the D/A converter 58-7, where the output is a continuous restored playback video signal. A signal can be obtained. Next, the effects of the present invention will be explained. In the case of a magnetic recording/reproducing device in which the recording density is improved and the output of the reproducing head is reduced, and the output of the reproducing head cannot be obtained at a level with sufficient margin against equipment noise, the present invention can be used. Adopting a suitable recording and reproducing method will have a great effect. Assuming that the head rotation speed during recording is constant, doubling the head rotation speed during playback will increase the head output by approximately 2 when using a wound magnetic head.
The signal bandwidth will also be doubled. Since device noise is generally proportional to the square root of the band, the noise level is multiplied by √2, and the signal-to-device noise ratio C/N at the head output is improved by 3 dB. Furthermore, in the case of the FM modulation method generally used when recording video signals, the frequency deviation width is doubled when the rotation speed is doubled, and therefore the demodulated output is doubled. At this time, the signal band is also doubled, so the noise band is also doubled, and the noise level is proportional to the square root of the band, so it is multiplied by √2. Therefore, the S/N ratio during demodulation is also improved by 3 dB. That is, a C/N improvement of 3 dB in the head output and a 3 dB S/N improvement in demodulation is obtained, resulting in a total improvement of 6 dB compared to the conventional method. The present invention is not limited to FM recording.
It is also effective when applied to cases where television signals are converted to digital signals and recorded and reproduced. The difference in rotational speed during recording and reproduction in the present invention is not limited to the double speed and triple speed described in the above embodiments, but
Generally n times faster (n is a real number including integers, n>1)
In that case, the time axis expansion system may be an n-fold expansion circuit system. Furthermore, although the above embodiments have described recording and reproducing video signals, it is clear that the video signals including audio signals, audio signals, or information signals in general may be used. Further, according to the present invention, the present invention can be applied to a digital high-density recording/reproducing device using a newly proposed perpendicular magnetization recording method [Television Society Journal, Vol. 32, No. 5 (1978)] as a magnetic recording method. In some cases, it is necessary to improve the quality of the reproduced signal, to increase the S/N of the reproduced signal by applying the rotary head cylinder system to a more compact high-density recording, or to increase the S/N of the reproduced signal, or to increase the time axis expansion circuit system during reproduction. By using this, it becomes possible to eliminate time axis fluctuations that occur in the reproduction signal of conventional devices of this type.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of a rotating two-head VTR, FIG. 2 is a diagram showing the recording state on a magnetic tape, and FIG. 3 is a block diagram showing the drive system and recording processing system of an embodiment of the present invention. It is a line diagram. Fourth
This figure is a diagram showing a reproduction scanning locus with respect to a recording pattern, and FIG. 5 is a diagram showing a time axis of a reproduction signal with respect to a recording signal. FIG. 6 is a block diagram showing the time axis expansion circuit system. 12... Speed control system for rotating the cylinder motor at a constant speed, 13... Phase synchronization control system, 29...
...Video signal input terminal, 40...Speed control system for rotating the capstan motor at a constant speed, 41...
Phase synchronization control system, 56... video signal recording circuit system,
57... Reproduction signal processing circuit system, 58... Time axis expansion circuit system.

Claims (1)

[Claims] 1. In a magnetic recording and reproducing apparatus that records an original signal on a recording medium using at least one rotary head and reproduces the original signal, means for driving said rotary head at a first rotational speed during recording, and means for driving said rotary head at a first rotational speed during reproduction; means for driving the rotary head by switching to a second rotation speed that is n times the first rotation speed (n: real number); 1. A magnetic recording and reproducing apparatus comprising means for expanding the original signal to obtain a reproduced signal that is substantially the same as the original signal.