JPH09306061A - Recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of reproduced signal quality caused by reverse track reproduction by performing azimuth management for each recording track in a VTR for recording a video signal of one field in each inclined track by two rotary heads different from each other in azimuth angle. SOLUTION: A video signal of one frame is recorded in each inclined track by two rotary heads having different azimuth angles. Control pulses having duty ratios alternately changed one from the other are recorded for each inclined track. During reproducing, based on a relationship between the duty ratio of a reproducing control pulse and a pulse synchronized with the rotation of the rotary head, whether the reproducing rotary head is for reverse track reproduction or not is determined, and if the reverse track reproduction is determined, the operation is automatically correct to correct tracking by controlling the rotation of a capstan motor 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus, and more particularly to a recording / reproducing apparatus for recording and reproducing information signals by alternately forming tracks on a magnetic tape by rotary heads having different azimuth angles. .

[0002]

2. Description of the Related Art A helical scan type magnetic recording / reproducing apparatus (VTR), which is widely used at present, has two rotary heads having different azimuth angles which are mounted on a rotary drum so as to face each other. Approximately 1 magnetic tape diagonally
While winding over an angle range of 80 degrees, it is run at a constant speed and the two rotating heads rotating at high speed alternately form tracks on the magnetic tape to record video signals and the like. It is well known that the recording information signal is reproduced.

Here, the above-mentioned track is an inclined track whose longitudinal direction has an angle with respect to the longitudinal direction of the magnetic tape, and normally one field of each video signal is recorded on each track. Also, as a comparison signal for running control (capstan servo) of the magnetic tape at the time of reproduction, or a control system that controls the rotation phase of the rotary drum so that the rotary head accurately scans the recording track (phase of the drum servo). Control pulses are recorded in a control track along the longitudinal direction of the magnetic tape in a two-field cycle, that is, in a two-track cycle, for use as a reference signal of a control system).

On the other hand, in order to further increase the utilization efficiency of the magnetic tape, the basic structure is the same as that of the above-mentioned VTR, but the rotation speed of the rotary drum and the rotary head is set to the above-mentioned VTR.
It is conceivable to record and reproduce a video signal of one frame for each track as a half of that. Such V
In TR, the control pulse is recorded on the control track at a cycle of two tracks.

[0005]

However, the above-mentioned VT for recording and reproducing a video signal of one frame for each track.
In R, since the control pulse is reproduced at a cycle of two frames, the response of the capstan servo is reduced, which is twice as long as the cycle of the reproduction control pulse of the current VTR. Therefore, in order to solve this problem, it is conceivable to record a control pulse for each track in the above-mentioned VTR which records and reproduces a video signal of one frame for each track. There is a case where reproduction is performed by a rotary head having an azimuth angle different from the angle (reverse track reproduction), and the reproduction signal quality deteriorates.

[0006] The present invention has been made in view of the above points,
An object of the present invention is to provide a recording / reproducing apparatus capable of preventing a rotary head from scanning a reverse azimuth track when recording and reproducing a video signal of one frame for each track.

[0007]

In order to achieve the above object, the present invention forms an inclined track on a magnetic tape alternately by two rotary heads having different azimuth angles to form a video signal on a frame-by-frame basis. A recording means for recording and recording the control pulse on the control track by alternately switching the duty ratio of each frame and a reproducing means for reproducing the recorded video signal on the inclined track by the two rotary heads, and a control means. Duty ratio detecting means for reproducing the recording control pulse from the track and detecting the duty ratio thereof,
The relative phase relationship between the duty ratio of the reproduction control pulse detected by the duty ratio detecting means and the pulse synchronized with the rotation phases of the two rotary heads is detected, and based on the detection result, the reverse track reproduction is indicated. The reverse track detecting means for outputting the track detecting signal and the control means for controlling the rotation of the capstan motor for running the magnetic tape on the basis of the reverse track detecting signal are provided.

In the present invention, the control pulse is recorded corresponding to each inclined track in which the video signal for one frame is recorded, and the duty ratio of the control pulse is alternated for each frame. Since the recording is performed by switching, the duty ratio of the control pulse can be associated with the azimuth angle of the inclined track recorded corresponding to the recording position. Therefore, by detecting the relative phase relationship between the duty ratio of the reproduction control pulse detected at the time of reproduction and the pulse synchronized with the rotation phase of the two rotary heads, the rotary head reproducing the tilted track can detect the relative phase relationship. It is possible to determine whether they have different azimuth angles (that is, whether they are reverse tracks). Further, the determination result can be obtained for each tilt track.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

First, the recording operation of an embodiment of the recording / reproducing apparatus according to the present invention will be described with reference to the time chart of FIG. The recording / reproducing apparatus of this embodiment records a video signal by forming two inclined tracks on a magnetic tape by two rotary heads having different azimuth angles, similarly to the conventional helical scan VTR, and , The recorded video signal of the inclined track is reproduced, but unlike the conventional case, the rotation speed of the rotary drum is set to 1
/ 2 times, for example 900 rpm, 1 for each track
A video signal for a frame is recorded and reproduced, and the control pulse shown in FIG. 1B is recorded on the control track.

That is, the drum flip-flop (DFF) shown in FIG. 1A is a symmetrical square wave of one rotation one cycle (15 Hz) of the rotary drum, which is synchronized with the rotation of the rotary drum, and is provided on the rotary drum, for example. It is generated by a known means including a magnet, a pickup head that is fixed at a predetermined position, generates a pulse each time the magnet passes through a position facing each other, and a circuit that shapes the waveform of the pulse.

On the other hand, at the time of recording, the vertical synchronizing signal separated from the video signal recorded on the magnetic tape is supplied to the control pulse generating circuit to be frequency-divided by 1/2.
In synchronization with the polarity of the DFF, as shown in FIG. 1B, the duty ratio is 50 during the one-frame recording period by the first rotary head immediately after the DFF becomes high level, for example.
%, A control pulse having a repetition frequency of 30 Hz is generated with a duty ratio of 70% in the one-frame recording period by the second rotary head immediately after the DFF becomes low level.

The control pulse is recorded by forming a control track along the longitudinal direction on the magnetic tape by a fixed control head. Therefore, at least a tilted track (video track) on which one frame of video signal is recorded and a control track are formed on the magnetic tape, and a control pulse having a 2-frame period corresponds to each tilted track. Will be recorded. Further, since the duty ratio of this control pulse is alternately switched to 50% and 70% for each frame, the duty ratio corresponds to the azimuth angle of the recording tilt track.

Next, an embodiment of the reproducing system of the recording / reproducing apparatus of the present invention will be described. 2 is a block diagram of an embodiment of a main part of a reproducing system of the recording / reproducing apparatus according to the present invention, and FIG.
Shows a time chart for explaining the operation of FIG. When reproducing, as in the case of recording, the rotation of the rotary drum is synchronized with FIG.
While the DFF as shown in FIG. 3A is generated, the control pulse as shown in FIG. 3B is reproduced from the control track of the magnetic tape by the control head (not shown) and supplied to the waveform shaping circuit. A reproduction control pulse (PbCTL pulse) having a polarity corresponding to that of FIG.

As can be seen from FIGS. 3 (A) and 3 (C), the waveform-shaped reproduction control pulse has a rectangular shape with a 2-frame cycle in which the duty ratio is alternately switched between 50% and 70% for each frame. The duty ratio of the wave corresponds to the azimuth angle of the reproduction tilted track and is input to the reverse track detection circuit 1 and the phase detection circuit 2 shown in FIG. 2 together with the DFF.

The phase detection circuit 2 receives these input signals DFF.
An error voltage corresponding to the phase difference between the waveform-shaped reproduction control pulses is generated, and this phase error voltage is supplied to the terminal 5a of the changeover switch circuit 5 through the filter 3 and the amplifier 4 exhibiting the low-pass characteristic.

On the other hand, the reverse track detection circuit 1 receives the input signal D
A latch pulse having a timing as schematically shown in FIG. 3D, which is generated based on the FF, is generated, and the input waveform-shaped reproduction control pulse is latched by this latch pulse to generate a latch pulse. ) Signal is obtained. Here, the latch timing of the above-mentioned latch pulse is the duty ratio of the reproduction control pulse of 50% and 7
Since it is set to 60% which is the middle of 0%, the signal shown in FIG.
It is a duty ratio detection signal that changes to a low level when% detection is performed and to a high level when 70% duty ratio is detected.

Further, the reverse track detection circuit 1 performs an exclusive OR operation of the duty ratio detection signal (FIG. 3 (E)) thus generated and the DFF shown in FIG. 3 (A) by an exclusive OR circuit. After the calculation to generate the discriminated signal shown in FIG. 6F, as schematically shown in FIG. 6G, at the rising edge timing of the input waveform shaping reproduction control pulse (FIG. 3C). The signal to be discriminated is latched, and the latched output signal is supplied as a reverse track detection signal to the changeover switch circuit 5 to control the changeover.

Here, when the above-mentioned reverse track detection signal is at a low level (in the example of FIG. 3), when the phase relationship between DFF and the waveform-shaped reproduction control pulse is the same as during recording, that is, the rotary head is This indicates normal tracking in which tilted tracks having the same azimuth angle are reproduced. At this time, the changeover switch circuit 5 is connected to the terminal 5a side to supply the phase error voltage from the amplifier 4 to the adder 9. .

On the other hand, when the reverse track detection signal is at a high level, when the phase relationship between the DFF and the waveform-shaped reproduction control pulse is different from that at the time of recording, that is, the rotary head reproduces an inclined track having different azimuth angles. In this case, the changeover switch circuit 5 is changeably connected to the terminal 5b side to supply a predetermined fixed voltage V _fix to the adder 9.

On the other hand, a capstan motor 12 for rotating a capstan which holds the magnetic tape between the pulleys for traveling.
A pulse having a repetitive frequency corresponding to the rotation speed is extracted from the frequency generator (FG) formed in the capstan motor 12 and supplied to the speed detection circuit 6 in FIG. The speed detection circuit 6 compares the capstan rotation detection pulse with a predetermined reference signal to generate a speed error signal, and supplies the speed error signal to the adder 9 through the filter 7 and the amplifier 8 exhibiting a low-pass characteristic. The adder 9 adds the speed error signal and the phase error signal input via the changeover switch circuit 5.

The output signal of the adder 9 is passed through a DC / DC converter 10 to a motor drive amplifier (MDA) 1
1 is supplied to the capstan motor 12 as a motor drive signal after being amplified to a required level.
The rotation speed and rotation phase are controlled. Here, when the reverse track is detected, the fixed voltage V _fix is supplied to the adder 9 instead of the phase error voltage, so that the DC / DC converter 10
The phase error signal is set to a large value within the range where the saturation is not saturated, and the rotation of the capstan motor 12 is accelerated to force the rotation phase to 1
Advance the frame and set the normal tracking state.

Thus, in this embodiment, 1
In a recording / reproducing apparatus in which a video signal of one frame is recorded in each inclined track is detected from the phase relationship between the reproduction control pulse and the DFF whose duty ratio alternates every frame. ,
By controlling the running of the magnetic tape so as to prevent the reverse track, a high quality reproduced video signal can be obtained.

Further, in this embodiment, since the control pulse is recorded in units of each inclined track, 2
It has the feature that the response of the capstan servo is higher than that of the conventional device in which the control pulse is recorded for each track.

FIG. 4 is a block diagram of another embodiment of the main part of the reproducing system of the recording / reproducing apparatus according to the present invention. In the figure,
The same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 4, a changeover switch circuit 15 for switching between the output speed error signal of the amplifier 8 and the fixed voltage V _fix is provided. As a result, when the reverse track detection circuit 1 supplies a signal having a logical value indicating normal tracking to the changeover switch circuit 15, the changeover switch circuit 15
Is connected to the terminal 15a side and outputs the speed error signal from the amplifier 8 to the adder 9.

On the other hand, when the reverse track detection circuit 1 supplies a signal of a logical value indicating a reverse track to the changeover switch circuit 15, the changeover switch circuit 15 is connected to the terminal 15b side so as to be changed over and the fixed voltage V _fix is added. Output to 9.
Therefore, when the reverse track is detected, the fixed voltage V _fix is supplied to the adder 9 instead of the speed error signal, and thus the DC / D
A large disturbance is given to the speed error signal in a range where the C converter 10 is not saturated, and the rotation of the capstan motor 12 is accelerated to forcibly advance one frame to bring about a normal tracking state.

It should be noted that the first surface is attached to the rotating surface of the small diameter rotating drum.
The first and second rotary heads having an azimuth angle of 3 mm and a third rotary head having a second azimuth angle.
The rotary heads of the above are attached at positions different from the first and second rotary head positions so as to face each other, and the magnetic tape is wound around the rotary drum at an angle over an angle range of about 270 degrees,
The first, third, second, and fourth rotary heads adjacent to each other in the rotation direction are sequentially used one field period at a time to record a video signal by forming an inclined track for each field,
As a recording / reproducing apparatus for reproducing, there is conventionally known a recording / reproducing apparatus in which the duty ratio of a control pulse is alternately switched to 55% and 60% for each one field for recording.

However, in this conventional recording / reproducing apparatus, the control pulse is recorded every two tracks, and the difference in the duty ratio of the reproducing control pulse at the time of reproducing is recorded by the same rotary head as the recording track at the time of self recording / reproducing. It is used for reproduction (that is, for example, a tilted track having a first azimuth angle can be played back by both the first and second rotary heads, but the tilted track is recorded at the first rotation. In the case of a head, reproduction is performed by the first rotary head), and it cannot be used for reverse track prevention in both the self-recording / reproduction and compatible reproduction of the present invention.

According to each of the above embodiments, the number of phase comparisons per unit time in the capstan servo is the same as that in the conventional recording / reproducing apparatus for recording the video signal of one field for each track, so that the rotation is performed. By changing the number of rotations of the drum, it can easily be used as a conventional recording / reproducing device.Because the duty ratio of the control pulse is variable, different information can be obtained by changing the duty ratio of the control pulse. It can also be used for recording and reproduction (however, it is necessary to alternately switch to a duty ratio within a range of a predetermined value or more and a duty ratio within a range of a predetermined value or less for each frame).

[0030]

As described above, according to the present invention,
In an apparatus for recording / reproducing a video signal of one frame for each track, it is a reverse track by detecting the relative phase relationship between the duty ratio of the reproduction control pulse and the pulse synchronized with the rotation phase of the two rotary heads. Since it is possible to determine whether or not it is possible, the reverse track state can be automatically corrected to the normal tracking state based on the determination result. Further, according to the present invention, since the reproduction control pulse can be obtained for each inclined track unit, the response of the capstan servo can be improved as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a time chart for explaining an operation of an embodiment of a main part of a recording system of an apparatus of the present invention.

FIG. 2 is a block diagram of an embodiment of a main part of a reproduction system of the device of the present invention.

FIG. 3 is a time chart for explaining the operation of FIG.

FIG. 4 is a block diagram of another embodiment of the main part of the reproducing system of the device of the present invention.

[Explanation of symbols]

1 Reverse Track Detection Circuit (Duty Ratio Detection Means, Reverse Track Detection Means) 2 Phase Detection Circuits 5, 15 Changeover Switch Circuit (Control Means) 6 Speed Detection Circuit 9 Adder 11 Motor Drive Amplifier (MDA) 12 Capstan Motor

Claims (3)

[Claims] 1. An inclined track is alternately formed on a magnetic tape by two rotary heads having different azimuth angles to record a video signal on a frame-by-frame basis, and a control pulse has a duty ratio alternated on a frame-by-frame basis. Recording means for switching to the control track and recording on the control track by the control head, reproducing means for reproducing the recorded video signal of the inclined track by the two rotary heads, and reproducing the recording control pulse from the control track and the duty ratio thereof. Detecting the relative phase relationship between the duty ratio of the reproduction control pulse detected by the duty ratio detecting means and the pulse synchronized with the rotation phases of the two rotary heads, and detecting the relative phase. Inverse indicating whether or not reverse track playback based on the result A recording / reproducing apparatus comprising: a reverse track detecting means for outputting a track detecting signal; and a controlling means for controlling rotation of a capstan motor for running the magnetic tape based on the reverse track detecting signal. 2. An exclusive OR circuit for performing an exclusive OR operation on the reverse track detection means for the duty ratio detection signal from the duty ratio detection means and a pulse synchronized with the rotation phases of the two rotary heads. And a latch circuit that latches the output signal of the exclusive OR circuit and outputs the reverse track detection signal at the timing of the leading edge of the reproduction control pulse. apparatus. 3. The control means, when the reverse track detection signal has a logical value indicating a reverse track state,
By applying a fixed voltage as a drive voltage to the capstan motor instead of one of the phase error signal and the speed error signal of the capstan motor, the rotation of the capstan motor is accelerated and the phase of the reproduction control pulse is changed. The recording / reproducing apparatus according to claim 1, wherein the recording / reproducing apparatus is forcibly advanced by one frame.