JPS6212563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking device for a helical scan rotary head video tape recorder.

In recent years, so-called auto-tracking devices have been introduced for the purpose of accurately scanning recorded tracks during playback in video signal magnetic recording and reproducing devices or video signal magnetic reproducing devices that use magnetic tape, such as video tape recorders. Ta. This auto-tracking device is capable of providing reproduced images without noise bands in special modes such as slow playback, still playback, fast playback, and reverse playback in which the tape is played back at a running speed different from the tape running speed at the time of recording. It is possible. Such auto-tracking devices usually attach a magnetic head for reproducing video signals to an electro-mechanical conversion element, apply a DITHER signal, which is a driving signal, to the electro-mechanical conversion element, and combine the DITHER signal and the magnetic head. The position of the magnetic head with respect to the recording track is known from the playback envelope of the head, and a control loop is constructed to keep it on track.

In this type of tracking device,
If the recording track width is narrow (e.g. 20 μm),
The displacement width of the reproducing magnetic head due to the DITHER signal is limited to several μm at most. In other words, the positional information of the reproducing magnetic head obtained from the reproducing envelope has an extremely poor signal-to-noise ratio. In order to configure the above control loop using such a signal, it is necessary to insert a low-pass filter with a large time constant in the middle of the control loop, which limits the response of the control loop. That is, in a transient state such as when fast playback is suddenly switched to reverse playback, the control loop does not respond for a certain period of time, causing a problem that noise bands occur in the reproduced image.

According to the present invention, the phase of a recording track on a magnetic tape wound around a tape guide drum with respect to a rotating magnetic head for reproduction (video head) is divided into a reproduction control signal, a sub-control signal obtained by effectively dividing the same, and a video head. The problem of the conventional example is solved by detecting the rotational phase of the head and displacing the mechanical position of the video head to scan the recording track.

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a diagram showing the main part of a video tape recorder in playback mode using an example of the present invention.
In the figure, 1 and 2 are the same angle (for example +6
It is a video head with an azimuth angle of
These are electrical devices such as bonded piezoelectric elements.
It is attached to the free ends of the mechanical transducers 21 and 22. The electro-mechanical conversion element 21,
The other end of 22 is attached to rotary disk 4. Reference numeral 3 designates a magnet for detecting the rotational phase of the video heads 1 and 2, which is also attached to the rotary disk 4. A rotational phase detector 5 is installed on the fixed part side corresponding to the magnet 3. The rotating disk 4 is driven by a DC motor 6 and is
Rotates at high speed in direction 5. The output signal of a frequency generator 7 attached to the DC motor 6, the output signal of the rotational phase detector 5, and the output signal of the reference oscillator 10 are supplied to a disk servo circuit 8. The output signal of the disk servo circuit 8 is supplied to the DC motor 6 via a drive circuit 9. Thereby, phase control of the rotary disk 4 during reproduction is performed.
The magnetic tape 23 is driven in the direction of an arrow 24 by the capstan 11 and a pinch roller (not shown). The capstan 11 is driven by a DC motor 15 via a pulley 12, a belt 13, and a pulley 14. The capstan control circuit 36 includes
An output signal from a frequency generator 16 that detects the rotational speed of the DC motor 15 and an output signal from a reproduction speed instruction section 35 are supplied.

The output signal of the control head 17 (hereinafter referred to as control signal R), the output signal of the rotational phase detector 20, and the output signal P of the disk servo circuit 8 are input to the arithmetic circuit 33 constituting the signal processing means. be done. The rotational angle of the capstan 11 is detected by the slitted disc 19 and the rotational phase detector 20, and the rotational phase detector 20 outputs a pulse signal corresponding to the rotational angle. For example, when the tape is reproduced at the same speed as the tape running speed during recording, the rotational phase detector 20 is set to output ten pulse signals within the control pulse interval reproduced by the control head 17. Since 10 pulse signals are output per control interval even if the traveling speed is different, this means that the reproduced control signal interval is effectively divided into 10. Hereinafter, the output pulse signal of the rotational phase detector 20 will be referred to as a sub-control signal Q. The rotational phase detector 20 is composed of, for example, a light emitting element and a light receiving element, and is of a type that detects light passing through a slit formed in the slitted disc 19. A gear-like body made of a magnetic material is used instead of the rotary phase detector 2.
A similar output signal can be obtained by using a magnetic flux detector at 0.

The output signal of the arithmetic circuit 33 is supplied to high voltage amplifiers 31 and 32. This signal is amplified to a voltage sufficient to drive the electro-mechanical transducers 21, 22, and is applied to the electro-mechanical transducers 21, 22 via conductive brushes 29, 30 and slip rings 26, 27. . The slip rings 26 and 27 are attached to the rotating shaft 18 of the DC motor 6 while maintaining electrical insulation.

Next, the operation of this embodiment will be explained.

FIG. 2 shows a recording track pattern recorded on the magnetic tape 23. In Figure 2,
A ₀ , B ₀ , A ₁ , B ₁ , and A ₂ each indicate a video track recorded using one field of a video signal as a predetermined unit, and A ₀ , A ₁ , and A ₂ indicate a certain azimuth angle (main In this embodiment, the azimuth angle is +6°), and B ₀ and B ₁ are recorded with video heads having different azimuth angles (-6° in this embodiment).

On the other hand, C is a control track on which a control signal indicating the recording phase of the video signal is recorded. In control track C, 3
Reference numerals 8 and 39 indicate control signals recorded once per frame; during recording, the start point of the _A0 track and the control signal 38 are recorded at the same timing, and the start point of the _A1 track and the control signal 39 are recorded at the same timing. Suppose that they were recorded at the same timing.

Now, when the video head 1 scans the starting point of the _A1 track, the control head 17 reproduces the control signal 39. Here, the magnetic tape 23
If the running of the video head 1 stops, the end of the scanning trajectory of the video head 1 becomes the end point of the _B0 track. This scanning period is defined as a first field. Since the azimuth angle of video head 1 is +6°, in order to reproduce the video signal without noise bars,
must scan the _A1 track in an on-track state throughout. That is, as shown in FIG. 3b, in the first field, by applying a voltage that linearly increases with scanning to the electro-mechanical conversion element 21, the position of the video head 1 is moved with the scanning, Ontrack. This amount of movement is zero at the start point of the _A1 track, and is exactly equivalent to one track pitch at the end point. As will be explained later, this amount of movement is also necessary for cases other than stills, and the amount of movement required for video head 1
and 2 are generated in conjunction with scanning.

Next, an arithmetic circuit 33 that calculates such a movement amount
I will explain about it.

In FIG. 1, the rotational phase of the video head 1 is detected by the magnet 3 and the rotational phase detector 5, and the rotational phase signal is given a certain delay by the disk servo circuit 8, so that the rotational phase as shown in FIG. 3a is obtained. ,
A signal P that becomes H level in the first field is obtained. This signal P is input to the arithmetic circuit 33 as an output signal of the disk servo circuit 8. The rising edge of the signal P indicates the point in time when the video head 1 scans the start point of the _A1 track, and the falling edge indicates the point in time when the video head 1 scans the end point of the _B0 track. Using such a signal P, we can calculate the amount of movement mentioned above, which is zero at the start point of _A1 track and corresponds to one pitch at the end point.
It is generated in a still pattern generating section 51 that constitutes a part of the arithmetic circuit 33. An example of the configuration of the arithmetic circuit 33 is shown in FIG. In FIG. 4, 50 is an input terminal to which the signal P is input, and 51 is a still pattern generating section. Still pattern generation section 5
1 is composed of an oscillator 52, a counter circuit 53, a counter circuit 54, a D/A (digital/analog) converter 55, and a D/A converter 56. 6
3 is an input terminal to which the output signal R of the control head 17 is input, and 64 is the rotational phase detector 2.
This is an input terminal to which the sub control signal Q obtained from 0 is input.

The signals inputted to the input terminals 50, 63 and 64 are sent to the still pattern generator 51, counter 65, D/A converter 69, D/A converter 70, adder 57, adder 58, low-pass filter 59 and Output terminal 61 via low-pass filter 60
and output to 62.

The operation of the arithmetic circuit 33 having such a configuration during still mode as described above will be explained. In this embodiment, the oscillator 52 oscillates a 300 Hz pulse signal. The output pulse signal of this oscillator 52 is input to the CP terminal of the counter 53. The reset terminal of the counter 53 is connected to the input terminal 50, and is reset to zero when the waveform of the signal P is at the L level, and performs a counting operation only when the waveform is at the H level. The output signal of this counter 53 is outputted to an output terminal 61 through a D/A converter 55, an adder 57, and a low-pass filter 59. This output waveform is as shown in FIG. 3b. Note that since the oscillation frequency of the oscillator 52 is 300 Hz and the first field is approximately 16.6 msec, approximately 5 pulses are input to the counter 53 during that period.

Now, when the video head 1 scans the starting point of the _A1 track, the control signal 39 is reproduced and the magnetic tape 23 stops running, so the counter 65 is reset by the control signal 39. Since D/A converter 69 outputs zero, adder 57 outputs only the output signal of D/A converter 55.

The signal waveform obtained here as shown in FIG.
is applied to the video head 1, so that the video head 1
During the field, the _A1 track can be scanned on-track.

Assuming that the magnetic tape 23 continues to stop running, when the video head 1 finishes scanning the _A1 track, the video head 2 scans the starting point of the _A1 track. Since the azimuth angle of the video head 2 is also +6°, if a signal as shown in FIG. 27 and to the electro-mechanical transducer 22, the video head 2 can scan the _A1 track on-track during the second field. In this case, the output pulse signal of the oscillator 52 is transmitted to the counter 54.
After passing through the D/A converter 56, the adder 58, and the low-pass filter 60, a signal waveform as shown in FIG. 3c is outputted to the output terminal 62. It is assumed that the counter 54 is reset to zero when the waveform of the signal P is at the H level, and performs a counting operation only when the waveform is at the L level. Since the magnetic tape 23 continues to stop running, only the output signal of the D/A converter 56 is applied to the adder 58. The signal waveforms shown in FIGS. 3b and 3c are called still patterns.

In the above explanation, when the control head 17 reproduces the control signal 39, the magnetic tape 2
3 stops running, next, after reproducing the control signal 38, the rotational phase detector 2
For example, if the sub control signal Q obtained from 0 is
A case will be explained in which the running of the magnetic tape 23 stops at the time when the pulses are counted. First, regardless of the running state of the magnetic tape 23, the still pattern generating section 51 generates a signal in accordance with the rotational phase of the video head 1 or 2 as shown in FIG.
Adder 5 adds a certain still pattern as shown in
7 or 58.

On the other hand, since the setting is such that 10 sub-control signals Q are output per control signal interval, the fact that the magnetic tape 23 stops running when 5 pulses of the sub-control signal Q are counted means that the video The starting point of the scanning trajectory of heads 1 and 2 is the _B1 track in FIG. 2, and the ending point of the scanning trajectory is the ending point of the _A1 track. In this situation, video heads 1 and 2
In order to scan the _A1 track in an on-track state from beginning to end, it is necessary to apply a constant bias voltage to the above-mentioned still pattern in adders 57 and 58. The means for obtaining this bias voltage will be explained next. In the arithmetic circuit 33, the CP terminal of the counter 65 is connected to the input terminal 64, and the sub control signal Q is input thereto.

On the other hand, the reset terminal of the counter 65 is connected to the input terminal 63, and the control signal R is input thereto. That is, since the counter 65 is reset by the control signal R and counts the sub-control signal Q, it is currently counting five pulses of the sub-control signal Q. By converting this into an analog voltage using D/A converters 69 and 70, a bias voltage corresponding to one pitch of a video track as shown in FIG. 3d can be obtained. Adder 57 adds such a bias voltage.
and 58, signals as shown in FIG. 3e and f are outputted to the output terminals 61 and 62, and the video heads 1 and 2 can scan the _A1 track in an on-track state from beginning to end.

In this way, the phase of the video track for video heads 1 and 2 is controlled by the control signal R.
By detecting the sub control signal Q, which is obtained by effectively dividing the control signal interval, and the signal P indicating the rotational phase of the video heads 1 and 2,
The video track (that is, the magnetic tape 3
Even if 2) stops, the video heads 1 and 2 can always maintain an on-track state by providing the phase information to the electro-mechanical transducers 21 and 22 to which the video heads 1 and 2 are attached.

Next, it will be explained that the above-mentioned concept holds true even when the running speed of the magnetic tape 23 is arbitrary.

First, the case of double speed playback will be explained. The phase relationships among the signal P indicating the rotational phase of the video heads 1 and 2, the control signal R, and the sub-control signal Q in this case are shown in FIGS. 5a, b, and c. Such a signal is input to the input terminal 50 of the arithmetic circuit 33,
63 and 64, the D/A converter 5
5th, 56th, 69th, and 70th output terminals.
Signals as shown in Figures d, e, f, and g are obtained.
These signals are calculated by adders 57 and 58, and then passed through low-pass filters 59 and 60, so that signals as shown in FIG. 5h and i are obtained at output terminals 61 and 62. Note that the vertical scale of each waveform indicates the level converted to the number of pitches of the video track. The phase relationship shown in FIGS. 5a and 5b is such that the timing at which the video head 1 scans the starting point of the _A0 track and the timing at which the control head 17 reproduces the control signal 38 are the same in FIG. When no displacement information is given to the electro-mechanical transducer 21, the video head 1
The end of the scanning trajectory becomes the end point of the _B0 track.
That is, if a voltage equivalent to -1 pitch in terms of video track is applied to the electro-mechanical conversion element 21 during the first field, the video track is scanned in an on-track state.

FIG. 5h shows that in the first field, the arithmetic circuit 33 outputs a voltage corresponding to -1 pitch. Similarly, at the beginning of the second field,
Video head 2 scans the starting point of _A1 track,
When no displacement information is given to the electro-mechanical transducer 22, the end of the scanning trajectory becomes the end point of the _B1 track. That is, if a voltage equivalent to -1 pitch in terms of video track is applied to the electro-mechanical conversion element 22 during the second field, the video track is scanned in an on-track state.

FIG. 5i shows that a voltage corresponding to -1 pitch is output in the second field. In the example of double speed playback described above, the rising edge or falling edge of the signal P indicating the rotational phase of the video heads 1 and 2 matches the phase of the control signal R, as shown in FIGS. 5a and 5b. This is an explanation of the case.

Next, a case where the phase is shifted during double speed reproduction will be described with reference to FIG. 6. In this case, a signal P indicating the rotational phase of video heads 1 and 2, a control signal R, and a sub-control signal Q
The phase relationships of are shown in Fig. 6a, b, and c. Such signals are input to the input terminals 50, 63, 6 of the arithmetic circuit 33.
4, the D/A converter 55,5
6, 69, and 70 are connected to the output terminals shown in FIG. 6d,
Signals as shown in e, f, g are obtained, and adders 57, 58 and low-pass filters 59, 60
After that, signals as shown in FIG. 6h and i are obtained at the output terminals 61 and 62. 6a, b, and c show that the first field starts when three pulses of the sub control signal Q are counted after the control signal R is reproduced, that is, the video head 1 starts scanning the video track. It is shown that. The starting point of the first field in FIG. 6h is biased by three pulses of the sub-control signal Q from the starting point of the first field in FIG. 5h. This is the same concept as applying a bias voltage equal to the amount of sub control signal Q counted when the start of the scanning locus of video heads 1 and 2 deviates from the _A1 track during still playback. 33 is the 6th
By outputting a signal as shown in Figure h, the video head 1 maintains an on-track state during the first half of the first field. In the second half of the first field, since the control signal R is reproduced, the counter 65 is reset as shown in FIG. 6 f and g, so that jumping corresponding to two video track pitches occurs in FIG. do. This shows that the scanning trajectory of the video head 1 jumps, for example, from the _A1 track to the _A2 track. Assuming that the response of the electro-mechanical transducer 21 is sufficiently fast, the video head ₁
Scan the track on-track, and scan the _A2 track on-track in the middle of the field.

As shown in FIG. 6i, the on-track state can be maintained in the same way in the second field.

The relationship between the signal P indicating the rotational phase of the video heads 1 and 2, the control signal R, and the sub-control signal Q used in the above explanation is as follows.
Since this holds true regardless of the running speed of the magnetic tape 23, this embodiment holds true even when the running speed of the magnetic tape 23 is arbitrary.

As described above, the present invention controls the phase of the recording track on the magnetic tape wound around the tape guide drum relative to the video head during playback using a playback control signal, a sub-control signal obtained by effectively dividing the signal, and a video head. Since the rotational phase of the head is also detected and the mechanical position of the video head is displaced to scan the recording track, the video head can maintain an on-track state even during the transient state of magnetic tape running or at any playback speed. This has an extremely excellent effect in that no noise bands occur in the reproduced image.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of a video tape recorder embodying an embodiment of the present invention, FIG. 2 is a recording track pattern diagram of a magnetic tape according to an embodiment of the present invention, and FIGS. 3 a, b, c, d, e and f are signal waveform diagrams of each part in FIG. 1, FIG. 4 is a circuit block diagram showing an example of the configuration of the arithmetic circuit in FIG. 1, and FIG.
a, b, c, d, e, f,
g, h, i are signal waveform diagrams showing other examples of signals of each part in FIG. 1. DESCRIPTION OF SYMBOLS 1, 2... Video head, 3... Rotational phase detection magnet, 5... Rotating phase detector, 8... Disk servo circuit, 11... Capstan, 17... Control head, 19... Disc with slit, 20... Rotating phase detector , 21, 22... electro-mechanical conversion element,
23... Magnetic tape, 26, 27... Slip ring, 29, 30... Conductive brush, 33... Arithmetic circuit, 51... Still pattern generation section, 57, 58...
Adder, 59, 60...low-pass filter, 65...counter, 69, 70...D/A converter.

Claims (1)

[Scope of Claims] 1. A video signal of a predetermined unit length is recorded by a rotating magnetic head as a track having a predetermined angle with respect to the longitudinal direction of the magnetic tape, and a control that indicates the recording phase of the video signal of the predetermined unit length. When reproducing the video signal from a magnetic tape on which signals are recorded in the longitudinal direction of the magnetic tape, the mechanical position of the rotary magnetic head for reproducing the video signal is approximately equal to the track with respect to the electro-mechanical transducer. A tracking device for a video signal reproducing device or a video signal recording and reproducing device that is moved in a right angle direction, and includes a control signal reproducing means for reproducing the control signal, and a tracking device for reproducing the control signal by the control signal reproducing means. control signal interval dividing means for obtaining sub-control signals by dividing control signal intervals independently of the running speed of the magnetic tape; phase detecting means for detecting the rotational phase of the rotary magnetic head for reproduction; and calculation means for calculating the position of the track relative to the rotating magnetic head for reproduction at any magnetic tape running speed by calculating information obtained from the control signal reproduction means, the control signal interval division means, and the phase detection means. . A tracking device, characterized in that the reproducing rotary magnetic head scans the track by applying an output signal of the arithmetic means to the electro-mechanical conversion element. 2. In claim 1, the control signal interval dividing means divides the control signal interval by using a pulse signal indicating a rotation angle of a rotating body that rotates in relation to the running of the magnetic tape. A tracking device configured to obtain a secondary control signal. 3. A tracking device according to claim 1, characterized in that a magnetic flux responsive head is used as the control signal reproducing means. 4. In any one of claims 1 to 3, when the running of the magnetic tape is stopped during reproduction, the phase for detecting the rotational phase of the rotating magnetic head for reproduction in the calculation means. Based on the signal obtained from the detection means, the signal is zero at the starting point where the reproducing rotary magnetic head scans the track, and the signal is 1 of the track at the end point.
A signal corresponding to the pitch is calculated as a still pattern signal, and a bias signal is also calculated using a counter that is reset by the control signal and counts the sub control signal, and a signal obtained by adding the still pattern signal and the bias signal is calculated. A tracking device characterized in that the output signal of the calculation means is an output signal. 5. In any one of claims 1 to 3, if the running speed of the magnetic tape is arbitrary during playback, the output of a counter that is reset by the control signal and counts the sub-control signals. A tracking device characterized in that a signal corresponding to one pitch of the track is added to the signal to obtain an output signal of the calculation means.