JPS6356753B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a control device for a magnetic recording/reproducing device having a rotating magnetic head, and is capable of suppressing noise generated when the rotating magnetic head scans between recording tracks when reproducing recorded signals during fast forwarding or rewinding of a magnetic tape. This provides a new control device for stopping the playback screen at a specific position. In conventional magnetic recording and reproducing devices, when reproducing images when fast forwarding or rewinding a magnetic tape in order to quickly find the desired recording position, the rotating speed of the capstan is increased to increase the transport speed of the magnetic tape. In order to keep the relative speed between the tape and the rotating magnetic head the same as during normal reproduction, the rotational speed of the rotating magnetic head cylinder is changed. During normal playback, the cylinder drive system controls the phase of the rotary magnetic head rotation drive motor so that it is phase-synchronized with the servo reference signal, and the capstan drive system uses a control signal reproduced from the magnetic tape to synchronize with the servo reference signal. By controlling the phase of the capstan motor for phase synchronization, tracking is performed in the same state as during recording. However, during fast forwarding or rewound playback, the cylinder drive system and capstan drive system are driven only by speed control. For this reason, since the rotating magnetic head cannot scan a specific location on the recording trajectory, there is a drawback that the position of the noise is not fixed at a specific location on the playback screen, but flows. The present invention solves the above-mentioned drawbacks, and one embodiment thereof will be described below with reference to the drawings. FIG. 1 shows a recording trajectory recorded on a magnetic tape by a rotating magnetic head. In Fig. 1, l is the length of the normally recorded magnetization trajectory,
W is the total width of the track, V _T is the magnetic tape transport speed during normal recording, v is the field frequency of the standard television signal, φ is the diameter of the rotating magnetic head cylinder, H is the number of rotating magnetic heads, π is the ratio of pi, K is the distance in the longitudinal direction of the magnetic tape with respect to the scanning locus of the rotating magnetic head when the magnetic tape is stopped, and l ² = (K〓V _T /v) ² +W ² ... (πφ/H) ² = K ² +W ² ... The following relational expression holds true. In the equation, the minus sign in ≦ means that the rotation direction of the rotating magnetic head cylinder and the magnetic tape transport direction are the same, and the plus sign means that they are opposite. If we substitute K in the formula into the formula, we get becomes. On the other hand, the relative velocity V _H between the magnetic tape and the rotating magnetic head is expressed as V _H =v·l . If we substitute the expression into the expression becomes. here If so, the formula becomes V _H ≒πφ/H·v〓V _T . During normal playback, the cylinder drive system can be controlled to synchronize the rotational phase of the rotating magnetic head cylinder with a servo reference signal having the same frequency as the field frequency of the standard television signal. When reproducing a recorded signal, if the magnetic tape is transported at a transport speed n times the transport speed during recording,
As is clear from the above equation, the relative velocity V _H changes, so to obtain the same relative velocity V _H as during recording,
It is necessary to change the frequency of the servo reference signal. Therefore, in order to make the relative velocity V _H the same as that during recording during playback during fast forwarding or rewound, calculate the frequency Rv' from the following formula, and change the rotational phase of the rotating magnetic head from this frequency Rv'. The motor for driving the rotation of the rotating magnetic head may be controlled in order to synchronize it with the servo reference signal. Rv′=v−V _T (1〓n)/πφ/H Next, tracking by the capstan servo will be explained. In order for the rotating magnetic head to scan a specific location (so-called tracking) at a magnetic tape transport speed n times that of normal recording, a control signal recorded at the widthwise end of the magnetic tape is reproduced, and the reproduced signal is The frequency is divided, and the phase of the obtained frequency-divided output signal and the servo reference signal having the changed frequency Rv' is compared, and the obtained error signal is used to drive the capstan motor for transporting the magnetic tape, and the reproduction is performed. Tracking can be performed by phase-synchronizing the control signal with the servo reference signal. Here, if the frequency division ratio for dividing the control signal is m, then n/m·v=Rv' can be set. Substituting Rv′ in the formula into the formula to find n gives n=v−HV _T /πφ/fv/m〓HV _T /πφ ……. Table 1 below shows, for example, in a VHS (registered trademark) type magnetic recording/reproducing device, the rotating magnetic head cylinder diameter φ = 62 mm, the magnetic tape transfer speed V _T = 33
mm/sec (2 hour mode), V _T = 11 mm/sec (6 hour mode), number of rotating magnetic heads H = 2, and field frequency v = 59.94 Hz, the speed multiplication ratio n for the control signal frequency division ratio m and the servo reference frequency Rv' are calculated using the above formulas and formulas.

【table】

[Table] As is clear from Table 1 above, for example, 2H
mode (2-hour mode), when the control signal frequency division ratio m = 11 during fast-forward playback, the reproduction image speed ratio n = 11.66, and the changed servo reference signal frequency Rv' = 63.55Hz. If so, it is possible to obtain the same relative speed as the relative speed during recording, and to equivalently synchronize the rotational phase of the rotating magnetic head and the phase of the control signal reproduced from the magnetic tape via the servo reference signal. Therefore, so-called tracking can be performed. Similarly, when rewinding and playing, when the control signal frequency division ratio m = 11, the double speed ratio of the reproduced image n =
10.30, and the frequency of the servo reference signal Rv′=
Just set it to 56.11Hz. Also in 6H mode (6 hour mode),
During fast forward playback and control signal frequency division ratio m
= 11, the reproduction image speed ratio n = 11.21,
The frequency of the servo reference signal should be Rv' = 61.09Hz. Similarly, when rewinding and playing, when the control signal frequency division ratio m = 11, the double speed ratio of the reproduced image n =
10.76, and the frequency Rv of the servo reference signal is
Just set it to 58.61Hz. Figure 2 shows that when recording, it is possible to select two different speeds for recording, and when playing back, the magnetic tape transport speed at the time of recording is detected, and the magnetic tape speed is automatically switched to the speed at which the recording was performed. The figure also shows a specific example of the configuration of a control device embodying the present invention, which is capable of fast-forwarding or rewinding playback without noise in each magnetic tape speed mode. First, the speed control loop will be explained. The rotary magnetic head rotation drive motor 1 is provided with a frequency generator 2 for rotational speed detection, and a frequency signal proportional to the rotational speed of the rotary magnetic head obtained thereby is used for speed control for driving the rotary magnetic head. It is input to circuit 3. This speed control circuit 3 for driving the rotating magnetic head compares the frequency signal with a target set frequency, obtains an error voltage according to the magnitude of the frequency error, generates a motor driving voltage, and generates a motor driving voltage. The speed of the head rotation drive motor 1 is controlled. Similarly, the capstan motor 4 for transporting the magnetic tape is also provided with a frequency generator 5 for detecting the rotational speed of the capstan motor, and the frequency signal obtained by this generator is inputted to the speed control circuit 6 for driving the capstan. Ru. This capstan drive speed control circuit 6 compares the frequency signal from the frequency generator 5 for detecting the capstan motor rotation speed with a frequency set corresponding to the target rotation speed, and corrects the frequency error. An error voltage corresponding to the magnitude is obtained to generate a motor drive voltage to control the speed of the magnetic tape transport capstan motor 4. Next, the phase synchronization control loop during normal playback will be explained. The output signal of the rotational phase detector 7 for detecting the rotational phase of the rotating magnetic head is amplified by a first amplifier circuit 8 and inputted to a first phase comparison circuit 9. On the other hand, the output signal of the first servo reference signal generation circuit 10 is input to the first phase comparison circuit 9 via the contact N of the switch _SW5 . The first phase comparison circuit 9 compares the phases of these two input signals, outputs a phase error signal corresponding to the magnitude of the phase error, and corrects the set speed of the rotating magnetic head drive speed control circuit 3. As a result, the rotary magnetic head rotation drive motor 1 is driven under phase synchronization control.
Further, the control signal regenerated by the control head 12 is amplified by the second amplifier circuit 13, and is transmitted to the contact N of the switch _SW1 , the contact N of the switch _SW2 , the contact N of the switch _SW3 , and the contact N of the switch _SW4.
The signal is input to the second phase comparator circuit 11 via the contact N of . On the other hand, the first servo reference signal generation circuit 1
The output signal of 0 is input to the second phase comparison circuit 11 via the contact N of the switch _SW5 . The second phase comparison circuit 11 compares the phases of both of these input signals, outputs a phase error symbol according to the magnitude of the phase error, and outputs a phase error symbol to the capstan driving speed control circuit 6.
Correct the speed setting. As a result, the magnetic tape transport capstan motor 4 is driven under phase synchronization control. Next, an explanation will be given of the automatic switching circuit section 22, which detects the magnetic tape transport speed during recording and automatically switches to the magnetic tape speed during recording during playback. The remaining part of the control signal, a part of which is input to the second phase comparison circuit 11, is input to the frequency-voltage conversion circuit 14 and converted into a DC voltage corresponding to the frequency of the control signal. The DC output voltage of this frequency-voltage conversion circuit 14 is input to a Schmitt circuit 15 having hysteresis in its threshold value. This Schmitt circuit 15 has, for example, the conversion characteristics of the frequency-voltage conversion circuit 14,
Assuming that the configuration is such that the higher the input frequency, the lower the output voltage, and the lower the input frequency, the higher the output voltage, when a magnetic tape recorded in 2-hour mode is played back in 6-hour mode, , the control signal is normally regenerated at 30Hz, but since it is regenerated at 10Hz, the output voltage of the frequency-voltage conversion circuit 14 becomes high and exceeds the first threshold of the Schmitts circuit 15, so the output becomes "H". Output the level. This Schmitt circuit 1
The speed setting of the capstan driving speed control circuit 6 is changed by the output signal 5, and the reproduction mode is switched to the 2-hour mode, and the rotation of the magnetic tape transporting capstan motor 4 is increased. Conversely, when a magnetic tape recorded in 6-hour mode is played back in 2-hour mode, the normal control signal is 30Hz.
Since it is played at 90Hz, frequency-voltage conversion circuit 1
Since the output voltage of circuit 4 becomes low and exceeds the second threshold of Schmitt circuit 15, it outputs an "L" level as an output. The output signal of the Schmitt circuit 15 changes the speed setting of the capstan drive speed control circuit 6, switches to the 6-hour playback mode, and drives the capstan motor 4 for transporting the magnetic tape.
rotation becomes slower. In this way, when playing,
It is possible to reproduce data at a speed that matches the magnetic tape transport speed during recording. Next, a loop for reproducing recorded signals and performing phase synchronization control during fast forwarding or rewinding will be explained. When selecting the servo reference signal at a frequency that satisfies the above formula, we used the VHS system (registered trademark)
With VTR, as is clear from Table 1 above,
A total of four types are required: two types for fast-forward playback and rewind playback in 2-hour mode, and two types for fast-forward playback and rewind playback in 6-hour mode. Once determined, the servo reference signal frequency corresponding to each mode can be determined. Therefore, by synchronizing the rotational phase of the rotating magnetic head with the phase of the servo reference frequency signal corresponding to each mode, the relative velocity _VH can be made the same as that during recording. Furthermore, regarding tracking, since the control signal is recorded in synchronization with the rotational phase of the rotating magnetic head, conversely, during playback, the rotational phase of the rotating magnetic head and the phase of the playback control signal are in the same phase. The magnetic tape transport capstan motor 4 may be controlled accordingly. However, during fast forward or rewound playback, the magnetic tape is transferred at a faster speed than the normal magnetic tape transfer speed, and a high frequency signal is obtained as the playback control signal, so it is necessary to divide the control signal by m. This makes it possible to compare the rotational phase of the rotating magnetic head with the phase of the reproduction control signal. Therefore, by determining the division ratio m from the above equation, the multiplication speed ratio n of the magnetic tape transfer speed for each mode is determined as shown in Table 1 above. In the phase control loop during fast-forward playback, the signal detected by the rotational phase detector 7 is amplified by the first amplifier circuit 8 and input to the first phase comparator circuit 9. Assuming that a magnetic tape recorded in the 2-hour mode is being played back, the output signal of the second servo reference signal generation circuit 16 is transmitted to contact C of switch SW ₇ , contact 2H of switch SW ₆ , and switch SW The signal is input to the first phase comparison circuit 9 through the contact S of _{No. 5} . The first phase comparison circuit 9 compares the phases of both input signals and supplies the error signal to the speed control circuit 3 for driving the rotating magnetic head. As a result, the rotary magnetic head rotation drive motor 1 is controlled in phase synchronization with the output frequency of the second servo reference signal generation circuit 16. On the other hand, the output signal of the second servo reference signal generation circuit 16 is also input to the second phase comparison circuit 11. Further, the control signal reproduced by the control head 12 is amplified by the second amplifier circuit 13, and the control signal is amplified by the second amplifier circuit ₁₃ , and the control signal is
It is input to the frequency divider circuit 17 via the contact N of SW ₂ and the contact S of switch SW ₃ . The control signal input to the frequency dividing circuit 17 is frequency-divided by a frequency division ratio corresponding to the speed ratio, and is input to the second phase comparator circuit 11 via the contact S of the switch SW ₄ . Second
The phase comparison circuit 11 compares the phases of both input signals and supplies the error signal to the capstan drive speed control circuit 6. Thereby, the magnetic tape transporting capstan motor 14 is controlled so that the control signal reproduced from the magnetic tape and frequency-divided is phase-synchronized with the output signal of the second servo reference signal generation circuit 16. For example, when playing back a magnetic tape recorded in the 6-hour mode, the output signal of the Schmitt circuit 15 causes the switch SW ₆ to be activated.
is switched to the contact 6H side, so the output signal of the third servo reference signal generation circuit 19 is switched to the switch SW ₈
The signal is input to the first and second phase comparator circuits 9 and 11 via the contact C of . As a result, the rotating magnetic head rotation driving motor 1 is controlled in phase synchronization with the output signal of the third servo reference signal generation circuit 19, and the magnetic tape transporting capstan motor 4 is regenerated by the control head 12 and frequency-divided. circuit 1
The control signal frequency-divided by 7 is driven in phase synchronization with the output signal of the third servo reference signal generation circuit 19. Next, a loop for reproducing the recorded signal during unwinding and performing phase synchronization control will be described. When the recording mode of the recorded magnetic tape is the 2-hour mode, the fourth servo reference signal generation circuit 18
The output signal is the contact R of switch SW ₇ ,
By being input to the first phase comparison circuit 9 through the contact 2H of SW ₆ and the contact S of switch SW ₅ , the rotating magnetic head rotation drive motor 1 is input to the fourth servo reference signal generation circuit 18. is controlled in phase synchronization with the output signal of Further, the output signal of the fourth servo reference signal generation circuit 18 is also input to the second phase comparison circuit 11. On the other hand, the control signal reproduced by the control head 12 is
The second amplifier circuit 13 amplifies the switch.
It is input to the inverting circuit 20 through the contact R of SW ₁ , the polarity of which is inverted, and input to the frequency dividing circuit 17 through the contact R of switch SW ₂ and the contact S of switch SW ₃ , where the frequency is divided corresponding to the speed ratio. The frequency is divided by the ratio, and the frequency is divided by the _second phase comparison circuit 11 via the contact S of the switch
is input. As a result, the capstan motor 4 for transporting the magnetic tape is connected to the control head 12.
The control signal reproduced by the servo reference signal generating circuit 18, whose polarity is inverted by the inverting circuit 20, and whose frequency is further divided by the frequency dividing circuit 17 is driven in phase synchronization with the output signal of the fourth servo reference signal generating circuit 18. The inverting circuit 20 serves to restore the control signal to a normal signal since during unwinding playback, the control signal is played back with an inverted polarity compared to during fast forward or normal playback. Furthermore, if the recorded magnetic tape is in the 6-hour mode, the fifth servo reference signal generation circuit 2
1 output signal is switch SW ₈ contact R, switch
The rotary magnetic head rotation drive motor 1 is connected to the fifth servo by being inputted to the first and second phase comparator circuits 9 and ₁₁ via the contact 6H of SW ₆ and the contact S of switch SW 5. Reference signal generation circuit 2
The capstan motor 4 for transporting the magnetic tape is controlled in phase synchronization with the output signal of the control head 12 and the inverting circuit 20.
The control signal whose polarity is inverted at , and whose frequency is further divided according to the speed ratio by the frequency dividing circuit 17 is driven in phase synchronization with the output signal of the fifth servo reference signal generating circuit 21 . Table 2 below shows the contacts connected to each switch for each mode.

[Table] FIG. 3 shows waveform diagrams of various parts of the circuit block shown in FIG. ) is a sampling waveform created inside the second phase comparison circuit 11, and (d) is a trapezoidal wave formed by the output signal of the second servo reference signal generation circuit 16 inside the second phase comparison circuit 11. The converted waveform (e) is the output waveform of the second phase comparison circuit 11. In this way, by making the relative speed between the rotating magnetic head and the magnetic tape the same as the relative speed during recording during fast forwarding or rewinding playback,
Since the horizontal synchronization signal frequency (approximately 15.75KHz in the NTSC television system) in the playback signal is the same,
The horizontal synchronization of the television receiver does not work. In addition, it is possible to divide the control signal and equivalently perform phase synchronization control between the rotational phase of the rotating magnetic head and the control signal.
The position of the noise generated when the rotating magnetic head crosses the magnetization locus can be maintained at a specific phase, so that good fast-forwarding or rewinding images can be reproduced without noise on the screen of the television receiver. Obtainable. Also, as in this embodiment, an automatic switching circuit section detects the magnetic tape transport speed during recording from the period or frequency of the control signal and automatically switches the magnetic tape transport speed during playback to the magnetic tape transport speed during recording. In a magnetic recording/reproducing apparatus having a magnetic recording/reproducing apparatus, if a plurality of servo reference signal frequencies are selectively switched by the output signal of the automatic switching circuit section during fast-forwarding or rewinding reproduction, it is possible to always automatically switch between the rotating magnetic head and the magnetic The relative speed with the tape can be the same as during recording, and the rotational phase of the rotating magnetic head and the phase of the playback control signal can be controlled in phase synchronization, allowing for good fast forwarding or rewinding playback without noise flow. It is. As explained above, according to the control device for a magnetic recording and reproducing apparatus according to the present invention, when a recorded signal is reproduced during fast forwarding or rewinding of a magnetic tape, when the rotating magnetic head scans between recording tracks, The generated noise can be stopped at a specific position on the playback screen, and therefore a good fast-forward or rewind playback image without noise flow can be obtained.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a pattern diagram of a magnetization locus, FIG. 2 is a block diagram showing the overall configuration, and FIG. 3 is a waveform diagram of each part of the block diagram shown in FIG. 2. DESCRIPTION OF SYMBOLS 1... Rotating magnetic head rotation drive motor, 4... Capstan motor for magnetic tape transfer, 7... Rotating phase detector, 9, 11... Phase comparator circuit, 12... Control head, 16, 18, 19, 21... Servo Reference signal generation circuit, 17...frequency division circuit.

Claims (1)

[Scope of Claims] 1. In a magnetic recording/reproducing device having a rotating magnetic head and capable of reproducing recorded signals by causing a magnetic tape to come into contact with the rotating magnetic head cylinder during fast forwarding or unwinding, The speed ratio n of the magnetic tape transfer speed to the normal playback speed and the output frequency Rv' of the servo reference signal generation circuit are expressed as n=v-HV _T /πφ/fv/m〓HV _T /πφ Rv'=v-HV _T ( 1〓n)/πφ (where, v is the field frequency, V _T is the magnetic tape transport speed during normal recording and reproduction, m is the control signal frequency division ratio, φ is the diameter of the rotating magnetic head cylinder, and H is the diameter of the rotating magnetic head The head number, π, is pi, and 〓 in the formula is - when the magnetic tape transport direction and the rotation direction of the rotating magnetic head cylinder are in the same direction, and + when they are in the opposite direction.) 1. A control device for a magnetic recording and reproducing apparatus, characterized in that the rotational phase of a head and the phase of a control signal reproduced from a magnetic tape are controlled in phase synchronization with the output signal of the servo reference signal generation circuit.