JPS6340516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing device having still image reproducing means.

Conventionally, in a magnetic recording/playback device that sequentially scans a track recorded obliquely in the longitudinal direction of a magnetic tape using a plurality of rotating magnetic heads with different azimuth angles and plays back recorded signals, the recording/playback device changes from a normal playback state to a stationary state. When transitioning to the video playback state, the tape is first stopped. Next, if the noise band on the reproduced screen appears on the screen out of the position corresponding to the vertical blanking period, the tape running capstan shaft is rotated by a small angle.
At that time, depending on the position of the noise band on the screen, the drive motor of the capstan shaft was pulse-driven once or several times to guide the noise band outside the playback screen, so the noise band was Although the noise is generally removed from the screen, it has the disadvantage that the viewer is made aware of the presence of the noise during the removal time.

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional apparatus, and first, after receiving a still image reproduction command, a reference signal corresponding to a recording position of an information track on a magnetic tape is detected. Then, after an adjustable set time, the magnetic tape starts braking the capstan motor for running the magnetic tape, stops the running magnetic tape at a position where no noise band appears on the playback screen, and plays back a noise-free static screen. The purpose is to provide a recording/playback device.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an overall schematic configuration of an embodiment of this invention, and FIG. 2 is a time chart explaining its operation. In Figure 1, 1 is a magnetic tape, 2 is a capstan shaft, and this shaft 2
The magnetic tape 1 is held between a hinch roller (not shown) that is pressed against the magnetic tape 1. The rotation of the shaft 2 causes the magnetic tape 1 to run in the direction of the arrow 3. The capstan shaft 2 is directly driven by a motor 4. Reference numeral 5 denotes a drive circuit for this purpose, which also constitutes a braking means for the motor 4. Reference numeral 6 denotes a fixed head constituting a reading means for reading control signals as reference signals _.
This is for reading C ₁ , C ₂ etc. The still image reproducing circuit 7 that constitutes the time setting circuit operates when a still image reproducing signal 8 is obtained by a system control device (not shown), and after receiving the control signal C _N read by the fixed head 6 for reading the control signal. , outputs a braking signal BL to the drive circuit 5 of the capstan tape 4 and the stop detection circuit 9 with a delay of a delay time set to a predetermined value, and when the stop signal ST is received from the stop detection circuit 9, braking is performed. signal
Aborts BL transmission and completes the operation. The stop detection circuit 9 inputs the output FG of a speed generator (not shown) built into the capstan motor 4 for speed control, and first detects the amplitude, period, phase, etc. of the output FG to determine the speed of the motor. Detects when the temperature has fallen sufficiently. For example, as shown in FIG. 2d, it is detected that the AC amplitude is smaller than a predetermined value and it is considered to be stopped. In this way, the next time the motor 4 almost stops, the stop signal ST is output.

Figure 3a shows the relationship between the formation state of the video track when an image signal is recorded on the magnetic tape and the locus of the playback head during still image playback, where 1 is the magnetic tape and 3 is the magnetic tape 1. 10a, 10b, and 10c are tracks recorded by the first magnetic head having a predetermined azimuth angle, and tracks 11a, 11b, and 11c have an azimuth angle different from that of the first magnetic head. This is the track recorded by the second magnetic head. now,
10a, 10b, 10c, and 11a, 11b, 1
It is assumed that the track widths of the magnetic heads 1c are equal, the width of the first magnetic head is approximately equal to the track width, and the width of the second magnetic head is slightly wider than the track width. Note that 13 indicates the running direction of the first and second magnetic heads. 12a and 12b are the trajectories of the first and second magnetic heads, respectively, and when a still image is played back, the place where the playback level of the image signal drops is at the edge of the track, so when no noise appears on the TV screen. be. Now, if the trajectories of the first and second magnetic heads are, for example, 14a and 14b, respectively, then the place where the playback level by the first magnetic head drops is away from the top or bottom end of the magnetic tape 1 and near the center 15.
As shown in Figure 3b, the TV screen 1
Noise band 18 appears at 7. The reason is the first
When performing reproduction using the first magnetic head, the first magnetic head follows the trajectory 14a, and the first magnetic head follows the trajectory 16b.
The signal of the part 16a and the part 16a are extracted, but since the signal level is almost lost at the transition point, the reproduced signal is not sufficient as an image signal and appears as noise on the screen.

The locus of the lower end side of the magnetic head when transitioning from a normal playback state to a still screen playback state without noise is shown by a broken line in FIG. In the figure, during reproduction by the first magnetic head, the capstan motor 4 starts braking when the lower end of the first magnetic head passes the _P0 point. When the speed of the capstan motor 4 decreases, the running speed of the magnetic tape 1 driven by the capstan shaft 2 decreases, and the relative speed with the magnetic head becomes small, so that the lower end of the first magnetic head away from the bottom end of track 10a.
The lower end of the second magnetic head draws the trajectory shown by the broken line between P ₀ and P ₁ , and then the lower end of the second magnetic head draws the trajectory shown by the broken line between P _{2 and} P ₃ . If the brake of the capstan motor is released, assuming that the motor 4 has stopped when the magnetic tape passes the magnetic tape, the magnetic tape stops, and still image reproduction without noise as explained in FIG. 3A is performed. During the transition period from normal reproduction to still image reproduction, the first head reproduces the shaded area 19 on the track 10a, and the second head reproduces the point cloud area 20 on the track 11a. In either case, there is no dropout of the reproduced signal, and no noise appears on the screen. Braking of the capstan motor 4 is performed by generating electromagnetic braking torque based on a braking signal.

The braking of the capstan motor 4 is started after a predetermined delay time after a still image reproduction command is issued and a control signal is detected by the control signal reading head 6. Control signals are recorded on the magnetic tape 1 for every two tracks, but the recording positions vary depending on the characteristics of individual magnetic recording and reproducing devices. If this variation is adjusted by the length of the delay time, the fourth
Braking of the capstan motor can be started from the P ₀ point in the figure.

The braking force for stopping the rotation of the motor 4 is
While the two magnetic heads rotate once, the magnetic tape 1
Sufficient braking torque is required to stop the vehicle from running under normal regeneration conditions.

Next, FIG. 5 shows a specific configuration of the still image reproduction circuit 7 as the time setting circuit in FIG. 1. Reference numeral 27 denotes a one shot used as a delay circuit, and is constructed so that the delay time can be varied. 28 is a T-flip-flop, 29 is a protection circuit,
This is a circuit for preventing runaway of the capstan motor 4, which is provided so that the braking of the capstan motor 4 is always terminated when the still image reproduction signal is terminated before the tape stops, and the still image reproduction signal is high. The flip-flop 28 is reset in synchronization with the change from a potential to a low potential, and the braking signal BL is set to a low potential.

The operation of the circuit shown in FIG. 5 will be explained using FIG. 2. During normal playback, when a still image playback signal from a system control device (not shown) is input at a high potential from the terminal 8, the AND gate 30 opens and the control signal C _N is input to the one shot of the delay circuit 27.
The one-shot delay circuit 27 outputs a low potential in synchronization with the rising edge of the input signal, and returns to the high potential output after a delay time adjusted to an optimum value in advance. The differentiating circuit 31 provides a pulse synchronized with the rise of the one-shot output of the delay circuit 27, which, after passing through an OR gate 32, triggers the flip-flop 28. Since the Q output of the flip-flop 28, that is, the braking signal BL, is at a low potential before the still image reproduction signal is applied at a high potential, the above-mentioned trigger pulse causes the braking signal to become a high potential and is output to the drive circuit 5 as a braking means. Then, a reverse rotation driving voltage is applied to the motor 4, and the motor 4 starts decelerating. When the rotational speed of the motor 4 falls below the set value, the stop signal ST, which is the output of the stop detection circuit 9, rises from a low potential to a high potential, and in synchronization with this, the differentiating circuit 33 outputs a pulse, and this pulse is sent to the OR gate. 32 through flip-flop 28
, the braking signal BL becomes low potential,
Braking command BL to the drive circuit 5 constituting the braking means
is released, the application of the reverse rotation drive voltage to the motor 4 is eliminated, and the rotation of the motor 4 is completely stopped due to the friction torque of the motor 4 and the like. In this case, the inertia of the rotation system of the motor 4 that runs the tape 1 is:
Normally, the inertia time constant of the motor rotation system is set to a large value to contribute to stabilizing tape running.
Normally, the ratio to the viscous resistance of rotation can be set as large as about 10 seconds in the case of this embodiment), and the braking force for stopping the rotation of the motor 4 is generated from the drive circuit 5 constituting the braking means. This is an electromagnetic braking force based on the reverse rotation drive voltage, and this braking force becomes almost constant when the voltage is constant, and is sufficiently larger than the viscous resistance and the resistance due to tape running, so that the braking force is not transmitted from the still image playback circuit 7. The error in the amount of movement of the tape 1 from the output of the braking signal BL to the time when the tape 1 stops running is almost negligible. Therefore, the transition from the normal playback state to the noise-free static screen playback state is achieved by adjusting the delay of the delay circuit 27 to compensate for the difference in characteristics between the respective magnetic recording and reproducing devices due to minute differences in the mounting positions of the magnetic heads. The correction can be made by adjusting the length of time in advance, and a transition from a normal playback state to a still image playback state can be realized without generating noise in the playback screen. By using the stop detection circuit 9, the braking is terminated when the motor has sufficiently stopped, so accurate stop control can be realized, and the magnetic tape 1 can be more stably moved to a noiseless still image position. It can be stopped. In other words, if the braking time is fixed by a one-shot circuit, etc., the tape speed at the end of braking may not be small due to uneven motor torque, etc., and the magnetic tape stop position may be less than the ideal stop position. There are also cases where there is a large overshoot or a return, but this type of overshoot or return can be eliminated.

As described above, according to the present invention, in the magnetic recording/reproducing apparatus, after receiving a still image reproduction command, the time setting circuit detects the reference signal corresponding to the recording position of the information track on the magnetic tape.
By starting to apply the reverse rotation drive voltage to the capstan motor for running the magnetic tape after a pre-adjustable set time, and stopping the application of the reverse rotation drive voltage just before the capstan motor completely stops. As a result, the magnetic tape can be stopped at a still picture playback position where no noise is generated on the playback screen, so there is an effect that the normal playback state can be shifted to the still picture playback state without noise appearing.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a magnetic recording/reproducing device according to an embodiment of the present invention, FIG. 2 is an operation time chart of the device shown in FIG. 1, and FIG. 3a is a recording of a magnetic tape when obtaining a still image. Relationship diagram between the information track of the finished image and the trace locus of the reproducing magnetic head, Fig. 3b
Fig. 4 is a diagram showing the occurrence of noise bands in the playback screen, and Fig. 4 is a relationship diagram showing the information track of the recorded image on the magnetic tape and the trace locus of the magnetic head for playback. This shows a case where the state shifts to the still image playback state without causing the occurrence of the error. FIG. 5 is a block diagram of a still image reproduction circuit of the apparatus shown in FIG. In the figure, 1 is a magnetic tape, 2 is a capstan shaft, 4 is a motor, 5 is a braking means, and 7 is a time setting circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A magnetic tape, a rotating magnetic head for reading information signals azimuthally recorded on the information tracks of the magnetic tape, reading means for reading reference signals recorded in correspondence with recording positions of the information tracks, and In the magnetic reproducing device, which has a capstan motor for driving and reproduces a still image upon receiving a still image reproduction command, the reference signal is detected by the reading means immediately after receiving the still image reproduction command. a time setting circuit that starts outputting a braking signal after a predetermined time from the time of detection, and a braking means that applies a reverse rotation drive voltage to the capstan motor for the output time of the control signal from the time setting circuit; A magnetic regeneration device comprising: a stop detection circuit that detects the rotational speed of the capstan motor and stops outputting a braking signal from the time setting circuit when the rotational speed becomes less than a predetermined value.