JPH0116072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a rotary head type video tape recorder (hereinafter referred to as a VTR), in particular, in which a magnetic tape is intermittently run in the opposite direction for playback, so that an operation in the opposite direction to that during recording can be achieved. This invention relates to a slow motion reproduction method that makes it possible to obtain a reproduced image noiseless and responsive to continuous speed changes.

It has been known that in order to perform reverse playback in a VTR, the tape should be run in the opposite direction to the direction in which it was recorded during playback. However, if the track is played back as is, the trajectory of the recorded track and the playback head are different, and a large noise bar will appear on the playback screen, making it impractical. The following methods have been considered to achieve reverse playback without noise bars. In other words, a rotating magnetic head is attached to the movable part (free end) of a head drive element such as a piezoelectric element, so that it can be deflected in the axial direction of the head cylinder (drum), and the tape running speed and direction during playback can be changed. The rotary magnetic head is moved so as to scan a desired track that has been recorded. In this method, complex waveforms related to tape speed information during playback, playback control signals, head switch signals, etc. must be created as signals to be applied to the head drive elements. In other words, in order to make the slow playback speed variable, different drive waveforms must be prepared for every tape speed.
It is necessary to continuously detect the playback tape speed.

Also, in order to perform a very slow reverse throw, the control signal cannot be detected with a normal head and a special head is required.

As mentioned above, special measures not available in conventional VTRs had to be taken, resulting in a very complicated system and an extremely expensive VTR.

The present invention aims to eliminate the drawbacks of the conventional reverse slow motion playback method as described above, and makes it possible to perform reverse slow motion playback that presents a beautiful screen without noise bars by a simple means, and to continuously maintain the slow speed. This provides a method that can be used to change the

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a track pattern recorded on a magnetic tape.
Tracks which are sequentially recorded while traveling in the direction of arrow F during recording are indicated by A ₁ , B ₁ , A ₂ , B ₂ , A ₃ , B ₃ , . . . Here, A ₁ , A ₂ , A ₃ , ... are tracks recorded by the same rotating magnetic head,
B ₁ , B ₂ , B ₃ , . . . are tracks recorded by rotating magnetic heads with different azimuths from A. If the magnetic tape 1 recorded in this way is run at the same speed during playback and is played back using the same rotating magnetic head as during recording, the signals will be in the order A ₁ , B ₁ , A ₂ , B ₂ , etc. It is well known that the same moving image as recorded is reproduced.

In the still mode in which the magnetic tape 1 is stopped during playback, for example, if the track width of the playback head is the same as the recording track width, the scanning locus of the playback head will be the area surrounded by the broken line 2 in Figure 1, and will be one track pitch. It will fall at an angle of . If the azimuth angle of the playback head is A azimuth shown on the tape pattern in Figure 1, the signal to be reproduced is only the shaded part of track _A2 , and the signal is missing in the upper part of the figure. As a result, noise bars appear on the playback screen. Here, in order to reproduce all tracks _A2 even when the magnetic tape is stopped, the first field period (1/60
It is sufficient to move the rotating magnetic head by one track pitch to the right in the figure in the track width direction (the sign is set to +) in seconds). In the second field, the rotating head of B azimuth comes into contact with the magnetic tape and attempts to scan track locus 2, so at this time B ₁
It is sufficient to completely reproduce the track by moving the rotating magnetic head one track pitch to the left in the diagram (the sign is set to -) and returning to 0 at the end of the second field. By doing this, the rotating magnetic head of B azimuth will reproduce track B ₁ in the second field.
Thereafter, the two rotating magnetic heads alternately reproduce the A ₂ and B ₁ tracks, realizing frame still reproduction. Movement of the rotating magnetic head in the width direction can be achieved by attaching the rotating magnetic head to a head driving element such as a piezoelectric element and applying an appropriate signal waveform to the head driving element. FIG. 2 shows the amount of deviation versus time on the horizontal axis. The period indicated by the broken line in FIGS. 2a and 2b is the period when the rotating magnetic head is not in contact with the magnetic tape.
The waveform does not have to be exactly as shown. As is clear from FIG. 2, the waveform of the signal applied to the head drive element in the stop mode can be an extremely simple triangular wave with one cycle of two fields.

Next, an example of reverse slow motion playback will be described. The magnetic tape 1 is intermittently fed in a direction opposite to that during recording in synchronization with the rotation of a rotating drum to which a rotating magnetic head is attached. That is, the speed at which the magnetic tape moves is the standard speed (same speed as during recording), and the direction is opposite. When not moving, the magnetic tape is stopped and the above-mentioned still mode is set. The deflection applied to the rotating magnetic head is the same as in still mode when the magnetic tape is stopped.
Give a slope of one track pitch as shown in the figure. In the moving state of the magnetic tape, the rotating magnetic head attempts to scan the trajectory surrounded by the broken line 3 with respect to the recorded track A ₄ in FIG. 1, for example. That is, since the magnetic tape 1 moves in the direction of arrow R, the trajectory of the rotating magnetic head is further shifted by one pitch from the stopped state. Therefore, if a deviation with a slope of two track pitches is applied in one field, _A4 tracks can be completely reproduced.

In the next field, the rotating magnetic head of the B azimuth is placed on the _B3 track with a similar slope, so that the signal on the _B3 track is completely reproduced by applying an excursion that also has a slope of two track pitches.

As described above, as a signal to be given to a head drive element such as a piezoelectric element attached to move the rotating magnetic head in the axial direction of the head cylinder (drum), the field time is synchronized with the stopping of the magnetic tape and the movement in the opposite direction. A slope waveform corresponding to one track pitch or a slope waveform corresponding to two track pitches is selected and given in units of .

Reverse slow motion reproduction can be realized by appropriately combining the two modes of the above-mentioned stop state and reverse running state. FIG. 3 shows an example of the amount of deviation applied to the rotating magnetic head during reverse slow playback. The slow playback speed can be varied over a wide range by appropriately selecting the stop time of the magnetic tape, that is, the number of still mode and movement mode. In this case, the above-mentioned two types of signals that give the deviation may be used, and since only the appearance ratio thereof changes, it can be realized with an extremely simple circuit configuration. Furthermore, since the control signals are played back at standard speed while the magnetic tape is in motion, conventional control heads can be used as-is even at very slow reverse slow speeds (for example, reverse frame-by-frame forwarding), reducing system complexity. do not have.

The above is one embodiment of reverse slow motion reproduction according to the present invention, and various other embodiments are possible. The first is that the reverse slow motion explained in Figures 1 to 3 is frame playback (one screen consists of signals from two different tracks, A and B), whereas field playback (one screen is composed of signals from two different tracks, A and B) does not cause image blurring. (composed of signals from the same track) can be realized.

FIG. 4 is a model diagram of a group of rotating magnetic heads for realizing reverse throw by field reproduction, and shows a rotating drum 5 driven by a rotating shaft 4.
Four magnetic heads are attached to the top. That is, 6 and 7 are recording/reproducing heads having different azimuth angles, and are fixedly mounted on the rotating cylinder 5 at a position of 180 degrees. 8 and 9 are reproduction-only heads with the same azimuth angle, and the azimuth angle is the same as that of heads 6 and 7.
coincides with one of the azimuth angles. The heads 8 and 9 are mounted on head drive elements 10 and 11, such as piezoelectric elements, so that the heads can be moved up and down in the axial direction of the cylinder by the head drive elements. During recording, video signals are recorded on the magnetic tape by heads 3 and 4 so as to form one diagonal track for each field, and the azimuth angle is alternately different for each field.The track pattern shown in FIG. 1 is used. becomes.

During reverse slow playback, heads 8 and 9 are used for playback, so only tracks with the same azimuth angle are played back. Field playback can be achieved by appropriately setting the deflection given to head drive elements 10 and 11. Can be done. In this case, the deflection given to the head driving elements 10 and 11 may be a tilt of one track pitch per field when the magnetic tape is stopped, and a tilt of two track pitches during movement, but the deflection shown in FIG. The waveform is parallel to the waveform in the vertical direction.

The second variation is the tape speed during movement. In the above embodiment, the tape was moved at a standard speed (in the opposite direction), but this is not limited to the standard speed, and can also be performed at a speed of 1/2, 1/3, etc. . In that case, since the moving speed is slow, the moving time will span 4 or 6 fields, and the deflection given to the rotating magnetic head during that period will be an inclination smaller than 2 track pitches.
For example, if the speed is 1/2, the slope should be 1.5 pitches. Of course, in the stopped state, the waveform is a one-pitch gradient wave, which is the same as in the previous embodiment.

FIG. 5 is a diagram showing the configuration of essential parts for realizing the above-mentioned reverse slow motion reproduction. In order to perform correct reverse slow playback, the time of tape travel and the time of center stop are controlled based on the position of the magnetic tape and the position of the rotating magnetic head, and the movement of the rotating magnetic head in the axial direction is also controlled. Rotating drum motor 16
Head drive elements 10 and 11 such as piezoelectric elements are attached to the head drive elements 10 and 11, and rotating magnetic heads 8 and 9 are attached to the movable parts at the tips of these elements. It is taken out from the pulse generator 17.
To perform reverse slow motion reproduction, when the reverse slow motion reproduction switch 12 is turned on, a signal for rotating the capstan motor 14 in the reverse direction is given from the reverse rotation command generator 13. At the same time, a signal indicating reversal is given to the drive signal generator 21.
When n drum pulses are received from the drum pulse generator 17, the magnetic tape 1 is sent in the opposite direction and stopped by the next control signal (picked up from the control track on the magnetic tape 1 by the control head 15). Just repeat.
Therefore, the drum pulse from the drum pulse generator 17 is transmitted to the monostable multivibrator 1.
8, by appropriately setting the time constant of the monostable multivibrator 18, an output pulse is produced when n drum pulses arrive, which sets the flip-flop circuit 19. The flip-flop circuit 19 is reset by a control signal from the control head 15, and as a result, a pulse corresponding to the period from the output pulse of the monostable multivibrator 18 to the arrival of the control pulse is obtained at the output of the flip-flop circuit 19. This is amplified by motor drive amplifier 20 and drives capstan motor 14. Therefore, the capstan motor 14 moves the magnetic tape 1 in the opposite direction by one frame and stops when it picks up the control signal. The output signal of the flip-flop circuit 19, which determines the period during which the magnetic tape 1 is to be moved, is also applied to a drive signal generator 21. Control to give a large tilt deviation. When the tape is stopped, the drive signal generator 21 generates a gradient wave of one track pitch for each field using drum pulses, and applies this to the head drive elements 10 and 11. The generation of a gradient wave can be achieved very easily, for example, by controlling the charging and discharging of a capacitor by a constant current source using a head switch signal. Note that during reverse slow playback, the control signal picked up by the control head 15 is played back while the magnetic tape 1 is moving at a predetermined speed, so it is played back at a very slow slow speed (for example, frame-by-frame forwarding).
Conventional control heads can also be used satisfactorily. With this configuration, a beautiful reverse slow motion image without noise bars can be reproduced using extremely simple means.

As described in detail above, the present invention uses a rotating magnetic head mounted on a head drive element such as a piezoelectric element when performing reverse slow motion playback by moving a magnetic tape in two modes, stopping and running in the opposite direction. , when the tape is stopped, it is deflected at an inclination in units of field periods, and when the tape is running in the reverse direction,
By controlling the inclination to change according to the running speed and performing reversing slow motion playback, beautiful reverse slow motion images without noise bars can be easily achieved at continuous reverse slow motions. This has made it possible, and its value is extremely high.

[Brief explanation of drawings]

Fig. 1 is a recording track pattern diagram on a magnetic tape for explaining the principle of the present invention, Fig. 2 a, b
3 is a diagram showing an example of the amount of deviation applied to the rotating head when the tape is stopped, FIGS. 3a and 3b are diagrams showing an example of the amount of deviation applied to the rotating head during reverse slow motion playback, and FIG. FIG. 5 is a diagram schematically showing a group of rotating magnetic heads that can be used in the present invention. 1... Magnetic tape, 6, 7, 8, 9... Head, 10, 11... Head drive element, 12... Reverse slow motion playback switch, 13... Reverse rotation command generator, 14... Capstan motor , 15
... Control head, 16 ... Rotating drum motor, 17 ... Drum pulse generator, 18 ... Monostable multivibrator, 19 ... Flip-flop circuit, 20 ... Motor drive amplifier,
21... Drive signal generator.

Claims (1)

[Claims] 1. In a video tape recorder that moves the magnetic tape while switching between a stopped state and a reverse running state during playback, a pair of rotating magnetic heads are each attached to the movable part of the head drive element, and when the tape is stopped, one field is moved. Approximately 1 in period
In order to give a tilted deviation of the track pitch to a tilted deviation larger than one track pitch when the tape is in the reverse tape transfer state, a forward/reverse signal from a reverse command generator provided in the operation unit and a tape stop state are used. 1. A slow motion reproducing method characterized in that a drive signal to the drive element is formed from a capstan drive signal having information on whether the vehicle is running or a running state and a head switch signal indicating one field period.