JPH0315876B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a magnetic tape recording and reproducing apparatus such as a video tape recorder (VTR), and more particularly to a magnetic tape recording and reproducing apparatus such as a video tape recorder (VTR). The present invention relates to a four-head helical magnetic tape recording and reproducing device.

Prior Art A rotary four-head VTR is known for its ability to perform still playback and slow playback well. In this type of system, it would be advantageous if noise-free still or slow playback screens could be automatically and easily obtained. However, during still or slow playback, it is difficult to detect the control signal (CTL pulse) recorded on the control track of the magnetic tape, so it is difficult to automatically set a good still or slow playback condition. It was.

OBJECTS OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic tape recording/reproducing apparatus that can perform special reproductions such as slow motion and still recording satisfactorily and easily.

SUMMARY OF THE INVENTION To achieve the above object, the present invention includes a pair of standard tape speed recording and reproducing rotating magnetic heads arranged with an angular interval of 180 degrees, and a rotary magnetic head for standard tape speed recording and reproducing. against 90
A pair of rotating magnetic heads for special reproduction are arranged with an angular interval of 180 degrees from each other, and the inclination of the scanning trajectory by the rotating magnetic heads for special reproduction matches the inclination of the recording track. a first head changeover switch for switching the output of the pair of standard tape speed recording and reproducing rotary magnetic heads at 180 degree angular intervals; A second head changeover switch is provided for switching the output of the pair of rotating magnetic heads for special playback at 180 degree angular intervals, and in the case of playback at standard tape speed, the output of the pair of rotating magnetic heads for special playback is switched between the pair of standard tape speed recording and playback heads. A rotating magnetic head is used to reproduce the FM signal on the magnetic tape, and in the case of special reproduction at a speed other than the standard tape speed, the pair of rotating magnetic heads for special reproduction are used to reproduce the FM signal on the magnetic tape. In a rotating four-head helical magnetic tape recording and reproducing apparatus configured as shown in FIG. A signal corresponding to the maximum or minimum amplitude position of the FM reproduction output with amplitude fluctuation caused by deviation from the recording track is determined by determining the relative positional relationship between the pair of rotating magnetic heads for standard tape speed reproduction and the recording track. a position detection circuit that generates a reference signal as a position detection signal shown in FIG. A reference signal generation circuit that generates a signal in synchronization with the switch head switching timing, and a phase that compares the phase of the position detection signal and the reference signal during slow playback or still playback, and generates an output corresponding to the phase difference between the two. A comparison circuit and means for adjusting the relative positional relationship between the recording track of the magnetic tape and the rotating magnetic head for special reproduction so as to make the phase difference zero during slow playback or still playback. The present invention relates to a magnetic tape recording/reproducing device characterized by:

Effects of the Invention According to the above invention, a CTL pulse obtained from a control track and a special position detection signal are formed based on the output of a rotary magnetic head for standard tape speed recording and reproduction, and this signal is used to detect the tape and the special reproduction. Since the structure is configured so that the relative position with respect to the rotating magnetic head for special reproduction is controlled, the scanning locus of the rotating magnetic head for special reproduction can be automatically and easily matched with the recording track, and a good reproduction output can be obtained.

Embodiment Next, a rotary four-head type VTR according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6.

The main body of the VTR in this example is a small home-use VTR.
The rotary drum 1 is the same as shown in FIG.
The magnetic tape 2 is wound around the fixed drum at the lower part by slightly more than 180 degrees, and the tape 2 is run diagonally along the outer peripheral surface of the drum 1. 3a and 3b are a pair of standard tape speed recording and reproducing rotary magnetic heads arranged at 180 degree angular intervals, and rotate together with the drum 1;
It is fixedly arranged so as not to be displaceable in the axial direction. In the following explanation, this rotating magnetic head 3
Let a and 3b be simply called standard heads. 4
Reference numerals a and 4b designate a pair of rotating magnetic heads for special reproduction arranged at angular intervals of 180 degrees, which are arranged so as to rotate together with the drum 1 and to be displaced in the axial direction of the drum 1. 3b is located at an intermediate angular position. In the following explanation, the rotating magnetic heads 4a and 4b will be simply referred to as special heads. 5a and 5b are bimorph plates made of piezoelectric vibrators. Special head 4
This constitutes a vibration device that periodically displaces a and 4b in the axial direction. 6 is a capstan for running the magnetic tape 2, and is driven by a capstan motor 7. Although not shown in FIG. 1, like a general VTR, there are a pair of reel drive mechanisms, a pinch roller, a tape guide,
It has a fixedly arranged audio head, a control head, and various electrical circuits.

2 and 3 illustrate scanning on the tape 2 of the diagonal scanning rotary head type VTR shown in FIG. 1. 8a, 8b, 9a, 9b,
10a and 10b are recording tracks. For playback at standard tape speed, the first standard head 3
a sequentially scans the tracks 8a, 9a, 10a, and the second standard head 3b scans the tracks 8b, 9
b, 10b are sequentially scanned. Running speed of tape 2 and standard heads 3a, 3 during recording and playback
If the rotational speeds of the recording tracks 8a to 10b are the same and the phases match, the recording tracks 8a to 10b are connected to the head 3.
a, 3b. This control is performed using a control signal (hereinafter referred to as CTL) consisting of a vertical synchronization signal recorded on the control track 11.
The problem of track deviation does not substantially occur. On the other hand, if the tape 2 is run in the direction of the arrow 12 at 1/2 of the standard speed and played back in slow motion, it becomes impossible to faithfully scan the tracks 8a to 10b with the standard heads 3a and 3b. The second standard head 3a scans along trajectories 13a, 14a and 15a shown by dotted lines in FIG. 2, and the second standard head 3b scans along trajectories 13b, 14b and 15b shown by dotted lines in FIG. As a result, the scanning trajectory deviates from the recording track, making it impossible to obtain a good reproduced screen. For this reason, in a rotating 4-head VTR, the special head 4
The scanning loci of a and 4b are recording tracks 8a to 10b.
The special heads 4a, 4b are periodically vibrated from the bimorph plates 5a, 5b by a vibrating device so that they match the . By the way, even if the inclinations of the recording tracks 8a to 10b match the inclinations of the reproduction scanning loci, if the phases do not match completely, the recording tracks 8
a to 10b cannot be faithfully scanned by the special heads 4a and 4b. If CTL pulse can be obtained during slow playback and still playback,
Although the above-mentioned phase shift problem does not occur, it is difficult to accurately obtain CTL pulses during low-speed slow playback and still playback. Therefore, in the present invention, based on the outputs of the standard heads 3a and 3b,
A position detection signal having the same function as a CTL pulse is formed, and based on this, the position of the magnetic tape 2 is controlled, and the recording tracks 8a to 10b and the special head 4 are
The phases of the scanning trajectories a and 4b are matched.

FIG. 4 shows a control system for the special heads 4a and 4b and a control system for the capstan motor 7, and FIGS. 5 and 6 show the states of each part in FIG. Bimorph plate 5 for displacing special heads 4a, 4b
A and 5b are connected to a bimorph plate drive signal generation circuit 16, and vibrate in response to a signal supplied therefrom, so that the inclination of the scanning locus of the special heads 4a and 4b coincides with the recording track during special reproduction. A speed information signal supply circuit 17 is connected to the bimorph plate drive signal generation circuit 16 in order to change the bimorph plate drive signal in accordance with the tape speed. The speed information signal supply circuit 17 generates a standard speed setting signal, a slow playback setting signal, a still playback setting signal, etc. in response to the operation of the VTR. Special heads 4a, 4b
A head selector switch circuit 18 at the output stage alternately selects the outputs of the heads 4a and 4b, and sends out a special reproduction output signal.

Figure 5 shows the state of each part during slow playback at 1/2 the standard speed. Figure 5A shows standard heads 3a and 3b.
This shows the state in which the head selector switch 19 selects the head selector switch 19. FIG. 5B illustrates the FM reproduction output of the standard heads 3a and 3b obtained at the output stage of the switch 19. FIG. 5C shows a position detection signal formed based on the reproduced output of FIG. 5B. Figure 5 D is the first
5E shows the displacement of the second special head 4b, and FIG. 5E shows the displacement of the second special head 4b. Figure 5 D, E
The solid line section of the vibration waveform indicates a period related to the slow reproduction output, and the dotted line section indicates a period not related to the slow reproduction output. Standard head 3 in Figure 5A
As is clear from a comparison of the timing of switching a and 3b with FIGS. 5D and E, the special heads 4a and 4b are switched with a delay of 90 degrees in phase angle from the standard heads 3a and 3b. This is because, as shown in FIG. 1, the special heads 4a, 4b are arranged at an angular distance of 90 degrees from the standard heads 3a, 3b. Now, to explain the displacement of the special heads 4a and 4b with reference to the angular positions of the standard heads 3a and 3b, the first special head 4a starts its displacement from 90 degrees, and then 180 degrees, as shown in FIG. 5D. Then, the displacement becomes 1/4 of the pitch of the recording tracks 8a to 10b shown in FIG. 2, and at 270 degrees, the displacement becomes 1/2 of the track pitch, and then returns to the original position at 450 degrees, and the same operation is repeated again. On the other hand, the second special head 4b
As shown in Figure E, -1/4 of the track pitch at 0 degrees.
The displacement becomes zero at 90 degrees, the displacement becomes -1/2 of the track pitch at 270 degrees, and the displacement becomes -1/4 of the track pitch at 360 degrees, which are repeated at regular intervals. Standard head 3 is shown in Figures 2 and 3.
Track deviations during slow playback of tracks a and 3b are shown, but the scanning trajectories of special heads 4a and 4b are shifted parallel to each other by 1/2 track pitch, with trajectories 13a to 3b being shifted in parallel by 1/2 track pitch.
It occurs with the same slope as 15b. Therefore, FIG. 5D,
As shown in E, by vibrating the special heads 4a, 4b, the inclination of the scanning trajectory of the special heads 4a, 4b becomes the same as that of the recording tracks 8a to 10b, and a slow playback output with less noise can be obtained.

By the way, it is desirable not only to match the inclinations of the recording tracks 8a to 10b with the inclinations of the scanning trajectories of the special heads 4a and 4b, but also to make their positions completely match. Therefore, a circuit for controlling the phase of the capstan motor 7 in accordance with the movement of the special heads 4a and 4b is added to the apparatus of this embodiment. A circuit 20 that forms a position detection signal based on the FM playback output obtained from the standard heads 3a and 3b in order to adjust the phase of the capstan motor 7 during special playback without depending on CTL pulses.
is provided. The position detection circuit 20 detects the envelope of the FM playback output shown in FIG. 5B.
an envelope detection circuit 21 for detecting the
It consists of a peak detection circuit 22 that detects the peak (maximum point) of this envelope, and a position detection signal generation circuit 23 that generates the position detection signal shown in FIG. 5C in response to the peak. In the case of 1/2 slow playback shown in FIG. 5, if the scanning loci of the standard heads 3a and 3b deviate from the recording track as shown in FIGS.
As shown in FIG. 5B, the pulses shown in FIG. 5C can be obtained at the same frequency as the switching frequency of the standard heads 3a and 3b. Note that the scanning loci of the standard heads 3a and 3b are not fixed to those shown in FIGS. 2 and 3, but occur at arbitrary positions. Therefore, the maximum point of the envelope in FIG. 5B and the pulse generation point in FIG. 5C also change.
However, in this embodiment, the position of the tape 2 is controlled so that the pulse is generated at the position shown in FIG. 5C. When playing stills, the standard head 3a,
3b changes as shown in FIG. 6B, for example, and the pulse shown in FIG. 6C is generated from the pulse forming circuit 20.

24 in FIG. 4 is a reference signal generation circuit;
Oscillator 25 that simultaneously obtains 3.58MHz subcarrier
and a frequency divider 26 that divides the frequency of this output according to special reproduction conditions. The frequency divider 26 has a frequency division ratio corresponding to the speed information signal from the speed information signal supply circuit 17. For example, in the case of 1/2 slow playback, the frequency divider 26 has the same period as the pulse generation period shown in FIG.
Hz), and in the case of still reproduction, the reference signal is generated at the same frequency (60 Hz) as in FIG. 6C. Further, the frequency divider 26 sends out a reference signal synchronized with the bimorph plate drive signal. For example, in the case of 1/2 slow playback in FIG. 5, the special head 4b is -
A reference signal is generated at the point of displacement of 1/4 track pitch, that is, at the point of 360 degrees×n. Incidentally, such timing can be set based on the switching timing of the standard heads 3a, 3b or the special heads 4a, 4b.

The reference signal obtained from the reference signal generation circuit 24 is input to the phase comparator 28 via the amplifier 27. In the phase comparison 28, the position detection signal obtained from the position detection circuit 20 and the CTL pulse obtained from the control head, that is, the CTL head 29 that scans the control track 11, are input to the amplifier circuit 3.
The signal amplified at 0 is selected by the switch 31 and input, and its phase is compared with the reference signal. The output of the phase comparison circuit 28 is sent to the speed control circuit 32 and the drive amplifier 3.
3 is used to control the capstan motor 7 as a tape moving mechanism. That is, the capstan motor 7 is controlled so that the reference signal obtained from the reference signal generation circuit 24 and the position detection signal obtained from the position detection circuit 20 match in phase. Note that the speed of the capstan motor 7 is controlled by a frequency generator 34 and a speed control circuit 32 coupled thereto.

Next, the operation of this device will be explained.

During standard playback, the speed information signal supply circuit 17 generates a standard speed signal based on the operation of a play switch (not shown), and the frequency divider 26 generates a reference signal corresponding to the standard speed. In addition, contact b of the switch 31 is closed, and the CTL pulse obtained from the CTL head 29 is applied to the phase comparator 28.
The phase and speed of the capstan 7 are controlled. During this standard playback, the standard heads 3a, 3
The output of b is used as the playback output.

In the case of 1/2 slow playback, the speed information signal supply circuit 17 sends out a 1/2 slow playback signal based on the operation of a 1/2 slow playback setting switch (not shown), and the frequency divider 26 sends out a 1/2 slow playback signal. For example, a 30Hz reference signal is generated. That is, the pulse train shown in FIG. 5C and a special reference signal are generated. Also, the speed of the capstan motor 7 is of course controlled to 1/2. Also, the contact a of the switch 31 is closed. In addition, special head 4
a and 4b are vibrated as shown in FIG. 5D and E while maintaining a constant time relationship with the reference signal. Special head 4
Since the heads a and 4b are kept on the same plane as the standard heads 3a and 3b and are rotated at an angular interval of 90 degrees, their scanning trajectories can be changed by vibrating them as shown in FIG. 5D and E. The slope of the recording track 8a
The slope corresponds to ~10b. On the other hand, standard head 3
Since a and 3b are not controlled by the bimorph plate, the tape 2 is scanned with track deviations as shown in FIGS. 2 and 3. As a result, the fifth
As shown in Figure B, the amplitude of the FM modulated carrier wave changes periodically. FIG. 5B shows the output of the desired control state (target control state), and the standard head 3
The maximum point does not necessarily change in this way based on the switching timing of a and 3b, and the maximum point moves in various ways.
The detection signal shown in FIG. 5C obtained from the position detection circuit 20 is compared with a reference signal in the phase comparison circuit 28, and the capstan motor 7 is controlled so that the phases of both signals match. That is, by controlling the capstan motor 7, the standard heads 3a, 3b, the special heads 4a, 4b, and the recording tracks 8a to 10b are
The relative positional relationship with is adjusted. More specifically, the first standard head 3a is in a state of scanning trajectories 13a, 14a, and 15a shown by dotted lines in FIG.
The second standard head 3b is controlled so as to be in the scanning state of trajectories 13b, 14b, and 15b shown by dotted lines in FIG. As a result, as shown in Figure 5B, 360
The maximum point is obtained at the position of degrees×n. Standard head 3
When the relationship between the special heads 4a and 3b and the recording track is controlled as described above, the special heads 4a and 4b have a fixed positional relationship with respect to the standard heads 3a and 3b, so that the recording tracks 8a to 10b can be accurately scanned. do. In addition, during this slow playback, special head 4
The switch 18 for the switches a and 4b is operated with a phase difference of 90 degrees at the switching timing for the standard heads 3a and 3b, and the output of the switch 18 is supplied to the FM demodulation circuit. During still playback, a still switch (not shown) is operated to send out a still playback signal from the speed information signal supply circuit 17 and cause the frequency divider 26 to generate a reference signal of, for example, 60 Hz. In addition, a sixth signal having a certain time relationship with this reference signal
The special heads 4a and 4b are vibrated as shown in Figures D and E. That is, the first special head 4a is displaced to zero at 90 degrees, 1/4 track pitch at 180 degrees, and 1/2 track pitch at 270 degrees, and the second special head 4b is displaced to -1/4 at 0 degrees. Displace the track pitch so that it becomes zero at 90 degrees and -1/2 track pitch at 270 degrees. As a result, the inclination of the scanning trajectory of the special heads 4a and 4b is the same as that of the recording tracks 8a to 9b in FIG.
corresponds to the slope of In addition, in an ideal control state, the scanning loci of the standard heads 3a and 3b are at the 7th position.
The state will be as shown by the dotted line in the figure, and as shown in Figure 6B.
FM playback output is available. The generation point of the detection signal in FIG. 6C corresponding to the maximum point of the output in FIG. 6B varies depending on the positional relationship between the standard heads 3a, 3b and the recording tracks 8a to 9b, Since a signal equivalent to that shown in FIG. 6C is input to the phase comparison circuit 28, the position of the tape 2 is controlled so that the detection signal matches this,
The scanning trajectories a and 4b exactly match the recording tracks 8a to 9b.

As is clear from the above, according to the method of this embodiment, during slow playback and still playback, the capstan motor 7 is controlled by the signal corresponding to the maximum amplitude point of the FM playback output, and the tape position is controlled. Therefore, it becomes possible to easily match the scanning loci of the special heads 4a, 4b with the recording track. Therefore, reproduction with less noise can be easily performed.

Further, since the settings of the frequency divider 26 and the bimorph plate drive signal generation circuit 16 are changed in a certain relationship, various special reproduction modes can be easily obtained.

Modifications The present invention is not limited to the above-described embodiments; for example, the following modifications are possible.

(A) The lowest point of the amplitude of the FM playback output shown in FIGS. 5 and 6 may be detected, and the position detection signal may be generated based on this.

(B) Other than 1/2 slow playback, 1/4 slow playback, etc. can be performed in the same way.

(C) Since CTL pulses are obtained during high-speed playback,
Although it is possible to utilize this, there is no problem even if the method of the present invention is adopted.

(D) Instead of controlling the tape position using the capstan 6, a separate tape moving mechanism may be provided and this may be controlled by the output of the phase comparison circuit 28.

(E) It is applicable not only to video signals but also to recording and reproducing information signals such as audio.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the principal parts of a VTR according to an embodiment of the present invention, and FIGS. 2 and 3 show a track on a tape and a head during 1/2 slow playback in the VTR shown in FIG. Fig. 4 is a block diagram showing the control circuit of the VTR shown in Fig. 1, and Fig. 5 is a waveform diagram showing the state of each part in Fig. 4 during 1/2 slow playback. , FIG. 6 is a waveform diagram showing the state of each part of FIG. 4 during still playback, and FIG. 7 is a plan view showing the relationship between the track on the tape and the scanning locus of the head during still playback. 2... Magnetic tape, 3a, 3b... Rotating magnetic head for standard tape speed recording and reproduction (standard head),
4a, 4b... Rotating magnetic head for special reproduction (special head), 5a, 5b... Bimorph board, 6...
Capstan, 7...Capstan motor, 8a
~10b... Track, 16... Bimorph plate drive signal generation circuit, 17... Speed information signal supply circuit, 20... Position detection circuit, 24... Reference signal generation circuit, 28... Phase comparator.

Claims (1)

[Scope of Claims] 1. A pair of standard tape speed recording and reproducing rotating magnetic heads arranged with an angular spacing of 180 degrees, and an angular spacing of 90 degrees with respect to the standard tape speed recording and reproducing rotating magnetic heads. and each other 180
a pair of rotating magnetic heads for special reproduction arranged with an angular interval of 100 degrees; and a vibrating device that vibrates the output of the pair of standard tape speed recording and reproducing rotating magnetic heads.
It is equipped with a first head changeover switch for switching at 180 degree angular intervals, and a second head changeover switch for switching the output of the pair of special reproduction rotating magnetic heads at 180 degree angular intervals. In the case of playback at tape speed, the pair of standard tape speed recording/playback rotating magnetic heads are used to play back the FM signal on the magnetic tape, and in the case of special playback at a speed other than the standard tape speed, the pair of special playback heads are used for playback of the FM signal on the magnetic tape. In a rotating four-head type helical magnetic tape recording and reproducing apparatus configured to use a rotating magnetic head for reproducing FM signals on the magnetic tape, the pair of standard A signal corresponding to the maximum or minimum amplitude position of the FM playback output with amplitude fluctuations caused by the deviation of the scanning locus of the rotating magnetic head for tape speed recording and playback from the recording track of the magnetic tape is transmitted to the pair of standards. a position detection circuit for obtaining a position detection signal indicating the relative positional relationship between the rotary magnetic head for tape speed reproduction and the recording track; and a position detection circuit for each rotation of the rotary magnetic head for standard tape speed recording and reproduction at a rate of one or two circuits. a reference signal generation circuit that generates a reference signal in synchronization with the head switching timing of the first head changeover switch; a phase comparator circuit that compares the phases of the magnetic tape and generates an output corresponding to the phase difference between the two; 1. A magnetic tape recording and reproducing apparatus, comprising means for adjusting the relative positional relationship with a rotating magnetic head.