JPH07262657A - Magnetic recording/reproducing device - Google Patents

Abstract

PURPOSE:To form a magnetic recording/reproducing device with less jitters and with high picture quality by adding the vibration having a phase opposite to tape vibration to a tape the as to tape vibration due to mainly a head impact and suppressing the tape vibration. CONSTITUTION:A tape vibration exciter 11 is arranged in the vicinity of a cylinder, and a time base error of a regenerative video signal by a magnetic head loaded on the cylinder is detected by a jitters detection means 13, and the tape vibration exciter 11 is controlled by the detection signal. Thus, when the magnetic tape is vibration excited in the direction of the vibration opposite to the tape vibration by a jitters waveform from the regenerative video signal, tape longitudinal vibration is canceled, and thus, the jitters are suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical scan type magnetic recording / reproducing apparatus such as a video tape recorder or an R-DAT.

[0002]

2. Description of the Related Art In a helical scan type video tape recorder, a rotary cylinder having a plurality of magnetic heads on its outer peripheral surface and a fixed cylinder having leads for helically winding a magnetic tape are coaxially arranged to rotate. Recording and playback are performed by rotating the cylinder.

By the way, it has been observed that tape vibration occurs on the entry side and the removal side of the magnetic head with respect to the magnetic tape of the magnetic recording / reproducing apparatus. In particular, in the case of a camera-integrated VTR, in which four magnetic heads are arranged on the outer circumference of a rotating cylinder by shifting 90 degrees each, and magnetic tape is wound around the cylinder by 270 degrees or more, the tape vibration is displayed on the playback screen. Problems such as deterioration of image quality are likely to occur as jitter.

With respect to the above problem, for example, Japanese Patent Laid-Open No. 1-21
Specific measures are also disclosed in Japanese Patent No. 3856. That is, the surface pressure is high at the contact portion of the magnetic tape with the head, and the head rapidly separates from the magnetic tape, so that the magnetic tape from which the magnetic head has been removed vibrates violently. In order to prevent this vibration, a minute protrusion of about 50 μm is provided to reduce the surface pressure applied to the magnetic head at the magnetic tape detachment surface, thereby preventing the magnetic tape from being unnecessarily wound around the magnetic head. The tape is prevented from vibrating due to the smooth detachment of the magnetic tape.

FIG. 4 is an explanatory view of the principle of tape vibration caused by head impact. A plurality of magnetic heads 2 are arranged on the outer peripheral surface of the rotary cylinder 1 which is divided into four parts in the circumferential direction. The magnetic tape 3 is wound around the rotary cylinder 1 to run, and at this time, the rotary cylinder 1 is rotated in the direction of the arrow, and each magnetic head 2 runs from P to Q. 2
Recording and reproduction shall be performed within an angle range of 70 degrees. Also,
The magnetic tape 3 is additionally wound by α degrees on both the entry side and the removal side of the magnetic head 2. The so-called overlap range is an extra head scanning range other than the recording and reproduction of the video signal itself for switching the magnetic head for recording and reproduction.

The supply-side tape guide 4 and the winding-side tape guide 5 are guide members for helically supplying and winding the magnetic tape 3 to the rotary cylinder 1.

Now, assuming that the magnetic head 2 is reproducing, the magnetic head 2a is separated from the magnetic tape 3 when the magnetic tape is scanned from point Q by α degrees. At this time, the magnetic tape vibrates at the time of detachment, and this appears as jitter on the playback screen.

That is, the contact pressure of the magnetic tape 3 on the magnetic head 2 is high, and the magnetic head 2 is rapidly separated from the magnetic tape 3, so that the magnetic head 2 is removed. The magnetic tape 3 vibrates violently, resulting in the tape vibration 6 on the detaching side. Further, when the magnetic head 2 plunges into the magnetic tape 3, the magnetic head 2b collides with the magnetic tape 3 when the magnetic tape is scanned by α degrees from the point P. At this time, the magnetic tape vibrates due to the impact at the time of a collision, which causes the plunge side tape vibration. This appears as jitter in the playback screen as in the case of the above-mentioned separation.

FIG. 5 is an explanatory view showing the above-mentioned reproduction screen. In the rotating cylinder structure, four magnetic heads 2a, 2b, 2c and 2d are arranged in the rotating cylinder 1 in 90 degree division. , Playback screen 9 on TV monitor 8
Then, the detachment side tape vibration 6 and the inrush side tape vibration 7 described above.
Becomes reproduction jitter, and so-called vertical line distortion 10 occurs. This is 2 in one scanning period in the above arrangement of magnetic heads.
There are times of separation and rushing, and these tape vibrations are combined, and reproduction jitter occurs at the position where the reproduction screen is divided into approximately three parts.

FIG. 6 shows a jitter time-axis waveform in a conventional minute protrusion, in which a video signal reproduced by a magnetic head is passed through a commercially available jitter meter (time-axis error detector from the reference frequency of the horizontal synchronizing signal). It was measured. In FIG. 6, the portions C and D correspond to the vertical line distortion 10 on the reproduction screen 9, and are also called “striking jitter” or “head impact”.

In order to prevent this vibration, an example in which minute projections of about 50 μm are provided on the tape releasing side and the tape entering side of the fixed lower cylinder to prevent the tape vibration is described in JP-A 1-213856. It is disclosed in the official gazette.

Incidentally, the tape vibration can be roughly classified into a tape longitudinal vibration vibrating in the tape running direction and a tape lateral vibration vibrating in the tape surface direction. The jitter is a change in relative velocity between the magnetic head and the magnetic tape, and is directly affected by longitudinal vibration of the tape. That is, the jitter and the tape speed fluctuation have a linear correlation as shown in (Equation 1). The tape speed fluctuation corresponds to the tape longitudinal vibration.

[0013]

[Equation 1]

FIG. 7 shows the relationship between jitter and longitudinal vibration of the tape. The jitter time axis waveform represents the reproduction signal from the magnetic head as the output from the above jitter meter, and the tape longitudinal vibration represents the tape speed fluctuation on the rotating cylinder 1 measured with a laser non-contact speed meter at the same timing. It was done. From these two waveforms, the head impact phenomenon portion shows a similar behavioral waveform, and the above correlation equation is confirmed.

FIG. 8 shows the experimental results of the relationship between the jitter and the longitudinal vibration of the tape, and it is confirmed experimentally that the jitter and the longitudinal vibration of the tape have a first-order correlation and a quantitative correlation of the above equation. I can. From this, it is confirmed that the jitter can be reduced by suppressing the vertical vibration of the tape.

[0016]

However, in the above-mentioned structure, there are the following problems. The formation of the minute protrusions is performed by cutting or the like when manufacturing the cylinder, but due to variations in processing, it is impossible to absorb all tape vibration due to variations in the amount of protrusion of the magnetic head, etc. It is transmitted to the entire magnetic tape, resulting in jitter (time axis error), which causes bending and color unevenness on the playback screen, resulting in degradation of the playback screen quality.

Therefore, an object of the present invention is to prevent the tape vibration at the time of head impact, which is the above-mentioned problem, by providing a magnetic tape vibrating means.

[0018]

In a magnetic recording / reproducing apparatus according to the present invention, a tape oscillating device is arranged in the vicinity of a cylinder, and a pulse generating means for generating a signal synchronized with the rotation of a magnetic head of the cylinder is mounted on the cylinder. A jitter detecting means for detecting a time-axis error of a reproduced video signal by the magnetic head, a control circuit for controlling the vibrating device by the detected signal, and a drive circuit for driving the tape vibrating device by the control signal. It has a configuration provided.

[0019]

[Function] Since the horizontal time axis error (jitter) has a unique correlation with the longitudinal vibration of the magnetic tape (vibration in the tape running direction), if the magnetic tape is vibrated in the reverse vibration direction with respect to the tape vibration, the tape Since the longitudinal vibration is canceled out, the jitter is suppressed as a result. That is, since the vibration of the magnetic tape is directly feedback-controlled based on the jitter waveform from the reproduced video signal, the jitter can be reduced with a versatile structure that is not affected by the variation in the protrusion amount of the magnetic head and the variation in the mechanism.

[0020]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention. A magnetic head 2 for recording and reproducing is arranged on the rotary cylinder 1, and a magnetic tape 3 is helically wound around the rotary cylinder 1 by a supply-side tape guide 4 and a winding-side tape guide 5. A vibrating device 11 for vibrating the magnetic tape 3 is provided in the vicinity of the supply guide 4, and the vibrating device 11 has a high mechanical rigidity like a laminated piezoelectric element.
A high resonance frequency is preferable. The tip of the vibrating device 11 is in contact with the magnetic tape 3 so as to be slightly wound, so that the vibration of the vibrating device 11 is efficiently transmitted. Magnetic head 2 provided on rotary head 1
The signal thus obtained is guided to the jitter detecting means 13 via the video reproduction signal circuit 12. Jitter detection means 13
Is to extract a horizontal synchronizing signal and detect a time axis error from the reference frequency of the horizontal scanning frequency, and a time axis error waveform shown in FIG. 6 is obtained. The pulse generator 14 determines the rotational phase of the magnetic head 2 on the rotary cylinder 1. Generally, a PG (pulse generator) signal from a rotary motor (not shown) is used, and the pulse generator 14 is used once per revolution. Provides a pulse signal of. The pulse obtained from the pulse generating means 14 is used for the synchronizing signal of the jitter detecting means 13 to obtain the jitter waveform corresponding to each magnetic head. The jitter signal obtained from the jitter detecting means 13 is guided to the control circuit 15 for driving the vibration exciter 11 according to the jitter signal, and the driving condition of the drive circuit 16 for driving the vibration exciter 11 is determined. Therefore, the drive phase, drive amplitude, drive pulse width, etc. are adjusted in accordance with the amount of jitter. In the above structure, the jitter from the video reproduction signal is directly detected, and from the result, the magnetic tape 3 is vibrated in the direction of arrow AA ′ in the direction opposite to the jitter waveform as shown in FIG. Since the vibration of 3 is canceled, the vertical vibration of the tape is suppressed as a result.

FIG. 2 shows a second embodiment of the present invention. Figure 2
In addition, from the vibrating device 11 for vibrating the magnetic tape 3, the drive circuit 16 therefor, the control circuit 16 for giving drive conditions, the pulse generation means 14 for detecting the rotation phase with the magnetic head 2, and the magnetic head. The video reproduction signal circuit 12 for demodulating the reproduction signal and the jitter detecting means 13 for detecting the time base error of the horizontal synchronizing signal from the reproduction signal have the same functions as those described with reference to FIG.
A feature of this embodiment is a function of temporarily storing the jitter waveform detected by the jitter detecting means 13 in the memory circuit 17. In a normal magnetic recording / reproducing apparatus, after the initial adjustment of each part is performed at the time of production, readjustment is not normally performed until a failure occurs. That is, the magnitude of the head impact by the magnetic head 2 and the phase in which it occurs hardly change. Therefore, the jitter time axis waveform shown in FIG. 6 is peculiar to the magnetic recording / reproducing apparatus, and its time-dependent change is almost constant. Therefore, even when the jitter pattern stored in the memory circuit 17 is read out at the time of reproduction and the jitter from the reproduced signal is not fed back, the same effect can be obtained even if a constant tape vibration is applied by the open loop control. I can expect it. Furthermore, if the jitter pattern stored in the memory circuit 17 is updated every time there is a reproduced signal, it is possible to cope with the jitter time axis waveform that has changed with time for some reason.
In particular, this configuration is effective in a recording process without a reproduction signal, and even if there is no successive reproduction signal, it is possible to suppress the vibration with a temporary jitter pattern, and it is possible to reduce the jitter during recording.

FIG. 3 shows a third embodiment of the present invention. Figure 3
At the vibration device 1 for vibrating the magnetic tape 3
1, a drive circuit 16 therefor, a control circuit 16 for giving drive conditions, a pulse generation means 14 for detecting a rotation phase with the magnetic head 2, a video reproduction signal circuit 12 for demodulating a reproduction signal from the magnetic head, a reproduction signal The jitter detection means 13 for detecting the time base error of the horizontal synchronizing signal from the memory circuit 17 and the memory circuit 17 for temporarily storing the jitter pattern are shown in FIG.
Since the function is the same as the content described in, the description thereof will be omitted. The feature of this embodiment is that the function for temporarily storing the jitter waveform detected by the jitter detecting means 13 in the memory circuit 17 and the selection circuit 18 for selecting when the function is not used are selected.
Is provided. The selection circuit 18 selects the normal reproduction state and the recording state. In the reproduction state in which a reproduction signal is generated, the magnetic tape 3 is sequentially excited in the direction in which the magnetic tape vibration is canceled by the jitter pattern from the video reproduction signal. Perform feedback control. When there is no reproduction signal in the recording state, the jitter pattern is read from the memory circuit 17, the magnetic tape 3 is vibrated in the direction of canceling the magnetic tape vibration, and open loop control is performed. As described above, the magnetic recording / reproducing apparatus selects the reproduction or recording state, and selects the vibration method of the magnetic tape with the optimum configuration for that state.

[0024]

As described above, according to the present invention, the tape oscillating device is arranged in the vicinity of the cylinder, and the pulse generating means for generating a signal synchronized with the rotation of the magnetic head of the cylinder is provided.
A jitter detecting means for detecting a time base error of a reproduced video signal by a magnetic head mounted on a cylinder, a control circuit for controlling the tape vibration device by the detection signal, and a tape vibration device driven by the control signal. A drive circuit for driving is used as a main basic configuration, and if the magnetic tape is excited in the reverse vibration direction with respect to the tape vibration, the longitudinal vibration of the tape is canceled, and as a result, the jitter is suppressed. That is, since the vibration of the magnetic tape is directly feedback-controlled based on the jitter waveform from the reproduced video signal, the jitter can be reduced with a versatile structure that is not affected by the variation in the protrusion amount of the magnetic head and the variation in the mechanism. Furthermore, the reproduction and recording states of the magnetic recording / reproducing apparatus can be selected, and an optimum jitter pattern can be obtained according to the selection, and an extremely low-cost, high-quality reproduction signal with little jitter can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a magnetic recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a magnetic recording / reproducing apparatus according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a magnetic recording / reproducing apparatus according to a third embodiment of the present invention.

FIG. 4 is a top view of the rotating cylinder for explaining the structure of the rotating cylinder and the head impact.

FIG. 5 is an explanatory diagram showing the relationship between jitter, reproduced image, and vertical line distortion.

[Fig. 6] Fig. 6 is a jitter waveform diagram in the conventional arrangement of minute protrusions.

FIG. 7 is a waveform diagram showing a waveform comparison between jitter and longitudinal tape vibration.

FIG. 8 is a characteristic diagram showing the relationship between jitter and longitudinal tape vibration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotating cylinder 2 magnetic head 3 magnetic tape 4 supply side tape guide 5 winding side tape guide 11 vibrating device 12 image reproduction signal circuit 13 jitter generating means 14 pulse generating means 15 control circuit 16 drive circuit 17 memory circuit 18 selection circuit

Claims (3)

[Claims] 1. A tape vibrating device installed near a cylinder for vibrating a magnetic tape, pulse generating means for generating a pulse in synchronization with rotation of a magnetic head of the cylinder, and mounted on the cylinder. A jitter detecting means for detecting a time axis error of a horizontal synchronizing signal from a video reproduction signal reproduced by the magnetic head; a control circuit for timely controlling a phase, a pulse width and an amplitude by a signal from the jitter detecting means, A drive circuit for driving the tape vibrating device in a direction of canceling the vibration of the magnetic tape generated when the magnetic head enters or leaves the magnetic tape in response to a control signal of a control circuit. Magnetic recording / reproducing device. 2. A tape vibrating device installed near a cylinder for vibrating a magnetic tape, pulse generating means for generating a pulse in synchronization with rotation of a magnetic head of the cylinder, and mounted on the cylinder. A jitter detecting means for detecting a time axis error of a horizontal synchronizing signal from a video reproduction signal reproduced by the magnetic head; a control circuit for timely controlling a phase, a pulse width and an amplitude by a signal from the jitter detecting means, A drive circuit for driving the tape vibrating device in a direction of canceling the vibration of the magnetic tape generated when the magnetic head enters or leaves the magnetic tape by a control signal of a control circuit, and records the jitter detection signal. A magnetic recording / reproducing apparatus comprising a memory circuit. 3. A tape oscillating device installed near the cylinder for oscillating a magnetic tape, pulse generating means for generating a pulse in synchronization with rotation of a magnetic head of the cylinder, and mounted on the cylinder. A jitter detecting means for detecting a time axis error of a horizontal synchronizing signal from a video reproduction signal reproduced by the magnetic head; a control circuit for timely controlling a phase, a pulse width and an amplitude by a signal from the jitter detecting means, A drive circuit for driving the tape vibrating device in a direction of canceling the vibration of the magnetic tape generated when the magnetic head enters or leaves the magnetic tape by a control signal of a control circuit, and records the jitter detection signal. It has a memory circuit and a selection circuit for selecting the memory circuit according to a reproducing or recording operation. Magnetic recording / reproducing device as a characteristic.