JPS634257B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a servo circuit for a magnetic recording/reproducing device, and the present invention relates to a servo circuit for a magnetic recording/reproducing device, which performs phase locking using a signal corresponding to a synchronization signal of a television system using a rotating drum motor and a capstan motor as a reference signal. It is an object of the present invention to provide a servo circuit that can control rotation and record and reproduce video signals of various television systems using one magnetic recording and reproducing device.

Traditionally, television systems include the NTSC system, PAL system, SECAM system, etc., and generally,
When recording and reproducing video signals in the NTSC format and PAL (SECAM) format using a magnetic recording and reproducing device (VTR), the tapes are run at different tape running speeds using dedicated VTRs for recording and recording.
It was playing. In other words, until now, there has been no single VTR that can process the video signals of each television system, and VTRs dedicated to each system must be prepared, which has the disadvantage of being incompatible and difficult to handle. Ta.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described below with reference to the drawings.

FIG. 1 shows a block system diagram of an embodiment of a servo circuit of a magnetic recording/reproducing apparatus according to the present invention. In the figure, during recording, the movable contacts of switches S _1-1 and S _1-2 are connected to terminal a. Also, when recording in the NTSC system, the movable contacts of switches S _2-1 and S _2-2 are connected to the terminals, while when recording in the PAL (and SECAM) system, the movable contacts are connected to terminal 2. Connect to. The vertical synchronizing signal V input to the input terminal 2 and the horizontal synchronizing signal H input to the input terminal 3 are supplied to a frame pulse forming circuit 4, which generates a frame pulse FP for each even field or for each odd field.
(30Hz for the NTSC system, 25Hz for the PAL (SECAM) system) and is supplied to the phase comparators 5 and 6, and is also supplied to the control head 7 via the switch _S1-2 to record the magnetic tape 1. It is recorded as a control signal at a predetermined position.

At the same time, the tack pulse TP (one pulse per drum rotation) from the drum motor 8 (the rotating drum is a two-head type, and one frame per rotation arm of the drum is recorded) is transferred to a monostable multivibrator (mono multi) 9. The signal is appropriately delayed and supplied to the phase comparator 5, where the phase is compared with the frame pulse FP from the frame pulse shaping circuit 4 and a phase error voltage is extracted. This phase error voltage is supplied to the adder 10, where the drum rotation pulse D.FG generated multiple times per rotation of the drum according to the rotation speed of the drum from the drum motor 8 is frequency detected by the frequency detector 11. is added to the extracted voltage (corresponding to the rotational speed of the drum motor 8), unnecessary frequency components are removed by the low-pass filter 12, and the motor drive circuit 13 converts the voltage into a motor drive signal to drive the drum motor. Drive 8. That is, the drum motor 8 is controlled to rotate at a constant rotation speed required for the television system used, using a voltage obtained by phase-locking the frame pulse FP and the tack pulse TP. Note that the frequency detector 11 is compatible with NTSC and PAL systems.
(SECAM) method, the center frequency of the frequency detection operation can be switched (If the number of drum rotation pulses D.FG for one rotation of the drum is N ₁ , the center frequency is
(30N ₁ for NTSC system, 25N ₁ for PAL (SECAM) system), drum motor 8 is connected to drum 1.
Even during the rotation period, the rotation speed is controlled with high precision by this drum rotation pulse D.FG.

This drum motor servo system is operated during playback in the same manner as during recording. That is, the frame pulse FP and tack pulse TP corresponding to the desired television system from the frame pulse forming circuit 4 are phase-locked, and the drum motor 8 is controlled so that the rotation speed corresponds to the television system.

Next, let's consider the capstan servo system. Figure 2 shows the patterns recorded on the tape 1, , '', ... are the patterns recorded for each field on the tape running at a predetermined speed,
The broken line ' is the locus of the rotary head coming into contact with the stationary tape. Draw a perpendicular line from point A to straight line '', and let the intersection with broken line '' be D, then △
A′DE and △BDA are similar.

Here, ∠DA′A is θ (static angle), vertical synchronization signal frequency is f _V , horizontal synchronization signal frequency is f _H , tape running speed is V ₁ , number of horizontal synchronization signals in one frame period is N _H , If the number of horizontal synchronization signals on the straight line' is S _H and the diameter of the rotating drum is D, then the straight line'
is ′=V ₁ /f _V cosθ=V ₁ N _H /2f _H cosθ (1). On the other hand, the straight line '=S _H /N _H /2+S _H πD/2 (2). Here, θ is small at 2° to 4°, and ′≒
Since A′D, from equations (1) and (2), V ₁ N _H /2f _H cosθ≈S _H /N _H /2+S _H πD/2. From this, the tape running speed V ₁ becomes V ₁ =2S _H f _H / _NH ( _NH +2S _H ) πD/cosθ(3).

On the other hand, the tape running speed of the NTSC system is V _1N , the horizontal synchronizing signal frequency is f _HN , the rotation speed of the capstan (rps) is n _N , the tape running speed of the PAL (SECAM) system is V _1P , and the horizontal synchronizing signal frequency is f _HP , the rotational speed (rps) of the capstan is n _P , and the diameter of the capstan is d. In addition, the tape running speeds for each television system are made to be approximately equal, and
Considering the H arrangement, S _H is 2.5 in the NTSC system,
In the PAL (SECAM) method, it is 3.5, and in this case, the number of rotations of the capstan in each method is (3)
From the formula, n _N = V _1N / πd = 2 × 2.5f _HN / 525 (525 + 2 × 2.5) D /
dcosθ =f _HN /55650 D/dcosθ (4) n _P V _1P /πd=2×3.5f _HP /625 (625+2×3.5) D/dc
osθ = f _HP /56428.571 D/dcosθ (5). Here, when finding M for which AM=55650 (6) A(M+1)=56428.571 (7) holds, it becomes M=71.4771, and if M=71, then A is from equation (6), A=55650/71= 783.8028 Or, from formula (7), A=56428.571/71+1=783.7301, and if this average is A=783.765,
Equations (4) and (5) are n _N ′=f _HN /71 (1/783.765 D/dcosθ) (4)′ n _P ′=f _HP /72 (1/783.765 D/dcosθ) (5)′ becomes. At this time, n _N ′ and n _P ′ in equations (4)′ and (5)′ are
For n _N and n _P in equations (4) and (5), n _N ′=1.0000482n _N n _P ′=0.9999555n _P , respectively, and n _N ≒n _N ′, n _P ≒n _P ′. The error is very small and can be ignored.

Here, if the number of capstan rotation pulses C.FG generated per capstan rotation is S, then S=783.765dcosθ/D holds true. As a result, equations (4)′ and (5)′ become n _N ′=f _HN /71S (8) n _P ′=f _HP /72S (9). From equations (8) and (9), the NTSC method and
In order to rotate the capstan at approximately the same rotation speed for both PAL (SECAM) systems, the capstan must be rotated at a frequency of f _HN /71 (221.6 Hz) for the NTSC system, and at a frequency of f _HP /72 for the PAL (SECAM) system. (217Hz).

Therefore, when recording in NTSC format, the switch
Connect the movable contact piece of S _2-2 to the terminal to set the frequency division ratio of the frequency divider 14 to 1/71, or in the case of the PAL (SECAM) method, connect the movable contact piece to the terminal to set the frequency division ratio of the frequency divider 14 to 1/71. Set the frequency division ratio to 1/72. For example, in the case of NTSC system,
The horizontal synchronizing signal of frequency f _HN input to the input terminal 3 is divided into 1/71 by the frequency divider 14 (221.6
Hz) and is supplied to the phase comparator 15 via the switch S _1-1 . The capstan rotation pulse C.FG from the capstan motor 16 is supplied to the phase comparator 15, where the phase is compared with the signal from the frequency divider 14 and a phase error voltage is extracted.

The phase of this error voltage is compensated by the filter 17 and unnecessary frequency components are removed.Then, the motor drive circuit 18 converts the error voltage into a motor drive signal, which is supplied to the capstan motor 16 to drive the capstan motor 16. Control is performed so that the phase of the rotation pulse C.FG and the phase of the signal from the frequency divider 14 match. That is, the capstan motor 16 is
The signal obtained by dividing the horizontal synchronizing signal frequency of the NTSC system by 1/71 and the capstan rotation pulse C.FG are phase-locked and controlled to rotate at a predetermined rotation speed using the voltage extracted.

In this case, in this embodiment, the frame pulse FP
Since phase comparison is performed using a signal obtained by dividing a horizontal synchronization signal with a higher frequency, the sample period for phase detection is shorter (therefore, the number of samples is larger) than when phase comparison is performed using frame pulses. As a result, even if there is a variation in the rotational phase due to disturbance, the variation can be corrected in a short time, and since the sample period for phase detection is short, the response speed is fast, and as a result, the capstan motor 16 The accuracy of rotational speed control can be improved.

Similarly, in the case of PAL (SECAM) method,
The horizontal synchronizing signal of frequency f _HP that enters input terminal 3 is divided by frequency by 1/72 (217Hz) by frequency divider 14.
and is supplied to the phase comparator 15. in this case,
The capstan motor 16 operates according to the NTSC system using a voltage obtained by phase-locking a signal obtained by dividing the horizontal synchronizing signal frequency of the PAL (SECAM) system by 1/72 and the capstan rotation pulse C.FG. It is controlled to rotate at a rotation speed that is approximately equal to the rotation speed in the case.

On the other hand, during playback, the movable contacts of switches S _1-1 and S _1-2 are connected to terminal b. The control signal reproduced from the tape 1 by the control head 7 is amplified by the amplifier 19, subjected to tracking adjustment by the monomulti 20, and then supplied to the phase comparator 6, where it is converted to the television system from the frame pulse shaping circuit 4. The phase is compared with the frame pulse FP of the corresponding frequency, and a phase error voltage is extracted. This error voltage has unnecessary frequency components removed by a reduction filter 21 and is supplied to a voltage controlled oscillator (VCO) 22. In addition, the above frame pulse FP is
The frame pulse forming circuit 4 is supplied with a vertical synchronizing signal V and a horizontal synchronizing signal H separated from the reproduced video signal.
It may be obtained by supplying the oscillator, or it may be generated using the output of a reference oscillator (not shown) corresponding to each television system.

The oscillation center frequency of the VCO 22 is set between f _HN /71 (≒ 221.6Hz) and f _HP /72 (≒ 217Hz), and its output oscillation frequency increases or decreases depending on the voltage level from the low-pass filter 21. It is said that the configuration is as follows. The output signal of the VCO 22 corresponding to the voltage level from the low-pass filter 21 is supplied as a reference signal to the phase comparator 15 via the switch _S1-1 , where it is combined with the capstan rotation pulse C.FG from the capstan motor 16. The phases are compared and a phase comparison error voltage is extracted to drive and control the capstan motor 16. In this case, the output of the VCO 22 has a frequency corresponding to the difference between the phase of the reproduction control signal from the monomulti 20 and the phase of the frame pulse FP from the frame pulse shaping circuit 4, and the capstan motor 16 outputs the reproduction control signal. The phase of the frame pulse FP is controlled so that the phase of the frame pulse FP matches the phase of the frame pulse FP.

At this time, the output oscillation frequency of the VCO 22 is stable and is controlled by phase comparison with the capstan rotation pulse C.FG, so that control can be performed with the same accuracy as the rotation speed control of the capstan motor 16 during recording. In addition, the capstan motor 16 is rotated while being phase-locked to the reference signal in the loop consisting of the capstan motor 16 - phase comparator 15 - filter 17 - motor drive circuit 18 - capstan motor 16. The capstan motor 16 can also be controlled with high precision.

In addition, in order to further improve the rotation speed accuracy of the capstan, it is only necessary to configure the capstan rotation pulse C.FG to be generated more often.In this case,
If the number of pulses C.FG is multiplied by M, the horizontal synchronizing signal frequencies f _HN and f _HP may be multiplied by M.

Also, the ratio of frequency division by the frequency divider is not limited to 1/71 or 1/72; in the case of the NTSC system, n _N = f _HN /N _N 1/S, and in the case of the PAL (SECAM) system. In this case, it is sufficient to set N _N and N _P (integers) such that n _P =f _HP /N _P 1/S is substantially equal.

Furthermore, although this embodiment has been described using a method in which two fields are recorded per one rotation of the drum, a method in which one field is recorded per one rotation of the drum may also be used. In that case, the reference pulse entering the phase comparator 5 is A vertical synchronization signal may be used instead of a pulse.

As described above, the servo circuit of the magnetic recording and reproducing apparatus according to the present invention includes a means for controlling the rotation of the rotating drum by phase-locking a pulse synchronized with a vertical synchronizing signal and a drum rotation pulse, and a means for controlling the rotation of the rotating drum by locking the phase of a pulse synchronized with a vertical synchronizing signal (or an integer thereof). A frequency division means for dividing the frequency of a signal of twice the frequency) corresponding to each television system, and during recording, a frame pulse is recorded on a magnetic recording medium as a control signal, and a pulse from the frequency division means and a capstan rotation pulse are used. means for controlling the rotation of the capstan by phase-locking the frequency-divided pulse; Since it is a means for controlling the rotation of the capstan by phase-locking the pulse corresponding to the rotation pulse from the capstan and the rotation pulse from the capstan, the rotation drum motor and the capstan motor each use a signal corresponding to the synchronization signal of the television system used respectively. The rotation is controlled by being phase-locked as a reference signal, so one VTR
The drum servo and capstan servo can be applied to any television system, and it is more compatible than the conventional system in which the servo must be applied using a dedicated VTR for each television system. It is easy to use, and since phase comparison is performed using a relatively high frequency pulse obtained by dividing the horizontal synchronization signal as a reference signal during recording, the sample period for phase detection is shorter than when phase comparison is performed using frame pulses. As a result, even if there is a fluctuation in the rotational phase due to disturbance, the fluctuation can be corrected in a short time, and the response speed is fast, and in particular, the rotation of the capstan motor can be controlled with high precision. It has characteristics.

[Brief explanation of the drawing]

FIG. 1 is a block system diagram of an embodiment of the circuit of the present invention, and FIG. 2 is a tape recording pattern for explaining the relationship between running of the magnetic tape and recording tracks. 1... Magnetic tape, 2... Vertical synchronizing signal input terminal, 3... Horizontal synchronizing signal input terminal, 4... Frame pulse shaping circuit, 5, 6, 15... Phase comparator, 7... Control head, 8 ...Drum motor, 13, 18...Motor drive circuit, 14
...1/N frequency divider, 16...capstan motor,
22...Voltage controlled oscillator, _S1-1 , _S1-2 ...Record/
Playback selector switch, S _2-1 , S _2-2 ...NTSC/PAL
(SECAM) changeover switch.

Claims (1)

[Claims] 1. Means for controlling the rotation of a rotating drum by phase-locking pulses synchronized with a vertical synchronizing signal and pulses generated every rotation of a rotating drum provided with a video head; Frequency signal) NTSC system, PAL (SECAM)
A frequency dividing means that divides the frequency at a frequency division ratio corresponding to each television system, and a frame pulse that is generated at a frequency corresponding to the television system for each even field (or odd field) during recording. means for recording a control signal on a recording medium and controlling the rotation of the capstan by locking the phase of a frequency division pulse from the frequency dividing means and a rotation pulse from the capstan; and a means for controlling the rotation of the capstan from the magnetic recording medium during reproduction. generated in response to a phase error voltage obtained by reproducing a signal and comparing the reproduction control signal and the frame pulse,
A servo circuit for a magnetic recording/reproducing apparatus, comprising means for controlling the rotation of the capstan by phase-locking a pulse corresponding to the frequency of the frequency-divided pulse and a rotation pulse from the capstan.