JPH01208757A - Head servo circuit - Google Patents

Abstract

PURPOSE:To shorten time from the actuation of a magnetic head to the start of reproducing and recording by synchronizing the rotational speed of the magnetic head with the phase of reference signals simultaneously to the moment when the rotational speed of the magnetic head reaches prescribed speed. CONSTITUTION:During the period when a magnetic head is started to rotate from a stopped state and the rotational speed of the head reaches a prescribed level, a reset switch SW 1 is turned on by means of a resetting timing generating circuit 17 and resetting pulses synchronous to the rotation of the magnetic head are supplied to a reference signal generating circuit 6. When the rotational speed of the magnetic head reaches a prescribed level, the reset switch SW 1 is turned off and, at the same time, phase control is started so as to make the rotation of the magnetic head phase-synchronous to reference signals. Therefore, the period from the actuation of the magnetic head to the start of reproducing and recording can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a helad servo circuit, and particularly in a magnetic recording/reproducing device or a camera-integrated VTR, etc., it is possible to obtain a desired rotational speed and speed by synchronizing the rotation of a head with a reference signal in phase. The present invention relates to a head servo circuit that controls the phase.

Conventional technology Helad servo circuits such as magnetic recording and reproducing devices or camera-integrated VrRs have two
A magnetic tape is wound around a cylindrical drum equipped with two magnetic heads.This drum rotates at a predetermined speed, and the magnetic arp runs on the circumference of the drum at a predetermined speed. tracks are formed on the magnetic tape to record images, and during reproduction, a magnetic head traces along these tracks to obtain reproduced images. Therefore, in order to obtain a good reproduced image, it is necessary that the running of the magnetic tape be stable and that the rotation speed and phase of the drum be accurate, that is, that the rotation of the drum be phase-synchronized with a predetermined reference signal. It becomes necessary.

When starting reproduction from a stopped state in a conventional magnetic recording/reproducing apparatus, first the rotational speed of the drum provided with the magnetic head is set to a predetermined rotational speed. For example, in the case of the N'r SC system, the predetermined rotation speed of the drum having the two magnetic heads is one half of the vertical synchronization frequency, that is, 30 Hz. Next, the number of rotations of this drum is divided from the output of a crystal oscillator, etc. to obtain 301
-1 An operation is performed to synchronize with the phase of the z reference signal, and after this synchronization is achieved, reproduction is started.

When recording an image signal of television broadcasting, a vertical synchronization signal in the image signal is used as the reference signal.

In addition, in a camera-integrated VTR in which a video camera and a recording/playback device are integrated, a signal obtained by dividing the output of an internal crystal oscillator, etc. is used as a reference signal even when starting a recording operation. First, after the drum is brought to a predetermined rotational speed, the phase of the reference signal and the rotation of the drum are synchronized.

Problems to be Solved by the Invention In order to record or reproduce stable images with a magnetic recording/reproducing device or a camera-integrated VTR, it is necessary to ensure that the rotation of the magnetic head is in phase synchronization with the reference signal, and that the running of the magnetic tape is It is necessary that the capstan is stable and that the rotation of the capstan is in phase synchronization with the reference signal for the capstan.

In a conventional 5A setting, the time it takes from starting recording or playback of a stopped magnetic recording/playback device or camera-integrated VTR until the running of the magnetic tape becomes stable and the rotation of the capstan synchronizes with the reference signal is as follows: Whereas it takes about 1 second, it takes about 3.5 seconds for the rotation of the magnetic head to be phase synchronized with the reference signal. This is because it takes about 1.5 seconds for the drum equipped with the magnetic head to reach a rotational speed of 30 Hz, and then about 2 seconds to synchronize with the phase of the reference signal. The reason why it takes longer for the magnetic head to achieve phase synchronization with the reference signal than with a capstan is because the capacity and weight of the drum are larger than that of a capstan. This is because the inertia must become large.

Therefore, the time it takes from when the magnetic recording/reproducing device or camera 5 to body type VTR is started until recording or playback starts depends on the time required for the rotation of the drum to be phase-synchronized with the reference signal. With conventional devices, it takes a very long time to achieve this phase synchronization, approximately 3.5 seconds, so during playback, the viewing name must wait until playback starts, and with the integrated camera v[R] When attempting to record a certain scene, there has been a problem in that the scene that was originally intended to be recorded may be missed before recording begins.

The present invention has been made in view of the above points, and is aimed at improving the time from the start of playback to the start of playback in a magnetic recording/reproducing device or a camera-integrated VTR, and
It is an object of the present invention to provide a head servo circuit that can shorten the time from the start of recording to the start of recording in a TR.

Means for Solving the Problems The present invention uses a rotation detection pulse obtained by detecting the rotation of a magnetic head that records or reproduces signals by rotating at a predetermined speed and a reference signal generated by a reference signal generation circuit. A reset pulse synchronized with the rotation of the magnetic head is used in the head servo circuit, which uses a phase comparator to compare the phases and output an error signal, and uses the error signal to control the rotation of the magnetic head to phase-synchronize the rotation of the magnetic head with the reference signal. A reset pulse generation circuit that resets the reference signal generation circuit by generating a reset pulse and supplying a reset pulse to the reference signal generation circuit, and a reset that passes or blocks the reset signal supplied from the reset pulse generation circuit to the reference signal generation circuit. and a reset timing for allowing the reset pulse to pass through the reset means when the rotation of the magnetic head reaches a predetermined rotation speed, and interrupting the reset pulse by the reset means when the rotation of the magnetic head reaches a predetermined rotation speed. During the period from when the stopped magnetic head starts rotating until it reaches a predetermined rotation speed, the reset means passes the reset pulse and supplies the reset signal to the reference signal generation circuit. A signal at a predetermined level that causes the magnetic head to rotate at a predetermined number of rotations is output as an error signal, and at the same time when the rotation of the magnetic head reaches the predetermined number of rotations, the reset means cuts off the reset pulse and starts phase control. The configuration is such that the rotation of the head is phase synchronized with the reference signal.

When a playback operation or a recording operation is started, the phase comparator outputs a signal at a constant level so that the rotation of the magnetic head reaches a predetermined rotation speed, and thereby the magnetic head gradually increases its rotation speed. let

During this time, the reset switch is turned on by the reset timing generation circuit, so that the reference signal generation circuit is supplied with a reset pulse synchronized with the rotation of the magnetic head.

When the magnetic head reaches the predetermined rotation speed, the reset switch is turned off, and the phase comparator outputs an error signal as a result of comparing the detection pulse obtained by detecting the rotation of the magnetic head with the reference signal. However, since the reference signal generation circuit is reset when the magnetic head reaches a predetermined rotational speed, the rotation of the magnetic head reaches approximately the predetermined rotational speed and is phase-locked to the reference signal at the same time.

Embodiment FIG. 1 shows a block diagram of an embodiment in which the present invention is applied to a general stationary magnetic recording/reproducing device capable of recording television broadcasting or normal reproduction. Further, FIG. 2 shows a timing chart of signal waveforms at each point in the circuit shown in FIG. 1.

A motor 1 that rotates a drum equipped with a head is provided with a pulse generating head (PG head) 2, which generates a rotation detection pulse a as shown in FIG. 2 (A>) according to the rotation of the drum. Pulse a corresponds to a pair of positive and negative pulses for one revolution of the drum.This rotation detection pulse a is converted into a square wave as shown in FIG. 2(B) in the waveform shaping circuit 3, and is further processed to generate a trapezoidal wave. In circuit 4, the second
It is assumed to be a trapezoidal wave C shown in the figure (C).

The reset pulse generating circuit 5 generates a reset pulse d shown in FIG. 2(D) in synchronization with the fall of the output signal S of the waveform shaping circuit 3. Therefore, this reset pulse d is always synchronized with the rotation of the drum.

The reference signal generation circuit 6 sets the switch SW2 to PB during playback.
A reference signal of 30H2 is generated by counting the pulses connected to the terminal and generated by the crystal oscillation circuit 7 from the time of reset (when an external reset pulse d or an internal reset pulse q described later is generated). (Schematically shown in FIG. 2(E)).

By supplying this result to the sampling pulse generation circuit 8, the limp ring pulse generation circuit 8 is configured as shown in FIG. 2(F).
The sampling pulse f shown in is output after being delayed by a predetermined period T from the reset time.

The sampling pulse f is supplied to a phase comparator 9, and its phase is compared with a trapezoidal wave C supplied from another terminal. In other words, when the sampling pulse r is generated at the center of the slope of the trapezoidal wave C as shown in FIG. 2(F), the output of the phase comparator 9 is Vcc/2 (Vcc is the maximum The voltage is, for example, 5 volts). Furthermore, if the sampling pulse f is generated earlier than the timing shown in FIG. 2, the output of the phase comparator 9 will be greater than Vcc/2, and from FIG. 6, the drum rotation speed will be higher than 30H1. If the sampling pulse f is generated later than the timing shown in FIG. 2, the output of the phase comparator 9 will be Vc.
The output of the phase comparator 9, which is smaller than c/2 and the drum rotation speed becomes lower than 30Hz, is supplied to the motor drive amplifier 11 via the SW3 low-pass filter 10 and the mixer 15, and the frequency/voltage exactly 30 when the output of the converter 14 and the output of the phase comparator 9 are Vcc/2)
12 controls the drum to rotate.

The motor 1 is provided with a frequency generator (FG) 12, which generates a signal with a frequency corresponding to the number of rotations of the motor 1.

This signal is waveform-shaped in a waveform shaping circuit 13 and converted into a signal with a voltage level according to the frequency by a frequency/voltage converter (FV converter) 14. This output signal is passed through a mixer 15 to a low-pass filter 10. It is mixed with the output signal and supplied to the motor drive amplifier 11 to control the rotational speed of the motor 1.

The FV conversion timing generation circuit 17 turns on and off the switch SWI at appropriate timing. That is, the output signal of the FV converter 14 containing information on the rotational speed of the drum is supplied to the FV conversion timing generation circuit 17, so that the switch S W + is turned on at a predetermined timing.
Turn off. This specific situation is shown in FIGS. 3(A) and 3(B).

In the figure (A), the horizontal axis is the frequency generated by the FGII 2, and the vertical axis is the output voltage of the FV converter 14 that changes depending on this frequency. In the same figure, fo
The frequency indicated by corresponds to the state in which the drum is rotating at 30)1z, and the frequencies f, , f, near fo respectively determine a predetermined frequency range. The same figure (B) is FV
Switch SWI is turned on by conversion timing generation circuit 17.

It shows the timing to turn off the SWI, and it shows that the SWI is turned on in the shaded part where the frequency of the signal generated by FG12 is below fl or above f2, and turns off in the frequency range from f'+ to f2. .

When the switch S W + is in the off state and the external reset input from the reset pulse generation circuit 5 is not supplied to the reference signal generation circuit 6, the reference signal generation circuit 6 counts the pulses generated from the crystal oscillation circuit 7. Shi30H2
It generates an internal reset pulse as shown in FIG. 2 (G) at a period of , and by resetting itself, becomes the reference source of 30H2. This is generated based on the oscillation signal of the crystal oscillator 7, so it is always constant at 30H.
It has a cycle of 2. When the rotation of the drum is in phase synchronization with the reference signal, the timing T at which the drum sampling pulse f is generated (corresponding to (The phase difference is set to 00)
is set.

At the same time, this time-pulling pulse d is generated at the timing to sample the level at the exact center of the slope of the trapezoidal wave C, the output of the phase comparator 9 is set to be Vcc/2, and the drum rotates at 30H7. I will do it.

In addition, in the circuit shown in FIG. 1, when the switch SWI is turned on, the output reset pulse d of the reset pulse generation circuit 5 is inputted to the reference signal generation circuit 6 via the gate 16, regardless of whether the phase is synchronized or not. At the same time, SW3 is connected to the S side, and a constant value of Vcc/2 is output from SW3. In this case, the drum rotates at 301-1z due to the operation of the feedback loop rotational speed control system consisting of the waveform shaping circuit 13, FV transformer 14, and motor drive amplifier 11. From this state, switch SW +
When SW3 is turned off, SW3 is connected to the L side at the same time.
The output of the trapezoidal wave generating circuit 4 is converted into a υ combining pulse f.
If we output a value with 1 non-bling, the reference signal generation circuit was reset when the switch SW θ0. Reset pulse generation circuit 5 by turning off switch S W +
Since the output signal of the reference signal generating circuit has continuity even if it is separated, this phase difference θ0 will be maintained.

This means that the rotation of the drum is phase synchronized at the moment the switch SWI is turned off.

Next, a description will be given of the operation when the reproduction of the apparatus shown in FIG. 1 which is in a stopped state is started. When reproduction is started, the drum and capstan (not shown) on which the magnetic head is installed start rotating, and the rotational speed is gradually increased. The rotation of the capstan is set to a predetermined rotational speed by the capstan rotation control section 20 shown in FIG. 1, and is further synchronized with reference No. 11 for capstans.

During this time, SW3 of the drum is connected to the S side, and the rotational speed of the drum is gradually increased by the Vcc/2 signal until it reaches 3 Of-1z. At this time, as shown in Fig. 3, the switch SW + is set to FV It is turned on by the conversion timing generation circuit 17.

At this time, the reset pulse d shown in FIG. 2(D) whose pulse interval gradually decreases as the rotational speed of the drum increases is supplied from the reset pulse generation circuit 5 to the reference signal generation circuit 6 via the gate 16. .

Approximately 1.0 seconds after the start of playback of the device, the rotational speed of the drum is 3, which corresponds to the range from f'+ to f2 in Fig. 3.
01-1z, FV conversion timing generation circuit 1
7 turns off the switch SW + and connects SW3 to the t side. Therefore, the reset pulse d is no longer supplied to the reference signal generation circuit 6, but the reference signal generation circuit 6 generates an internal reset pulse q, and the rotation of the drum becomes around 30Hz while the switch SWI is on. As a result, the external reset pulse d and the internal reset pulse Q are synchronized, and approximately 0.5
Within seconds, the rotation of the drums becomes phase-locked. Therefore, playback starts approximately 1.5 seconds after playback is started, which is significantly shorter than the conventional time of about 3.5 seconds.

When recording television broadcasting with the apparatus shown in FIG. The signal whose frequency is divided in half by the circuit 24 to 30Hz is sent to the gate 1.
6 to the reference signal generating circuit 6. Therefore, when recording a television signal, the operation of the present invention cannot be applied because the drum must be synchronized with a 30+12 signal frequency-divided from this vertical synchronizing signal.

As another embodiment of the present invention, instead of the FV conversion timing generation circuit 17, it is also possible to generate a signal for controlling the on/off of the switch SWI by a control means that controls the mechanical part of the entire device. be. As shown in Figure 4, this occurs for a certain period of time after playback is started (Figure 4 (B)).
), or by turning on the switch for a predetermined period just before the drum reaches 30112 after starting playback ((C) in the same figure).(A) shows the number of rotations of the drum after starting playback. It shows the changes. This is a predetermined rotation speed (here, 30
)-1z), there is relatively little variation in the time it takes to reach ()-1z), so instead of controlling the switch S W + by detecting the rotational speed, the switch S W + can be controlled at predetermined time intervals after regeneration is started. This is because there is no problem in turning it on and off.

FIG. 5 shows a block diagram of an embodiment in which the present invention is applied to a so-called camera-integrated VTR in which a video camera and a magnetic recording/reproducing device are integrated. In the figure, a head servo circuit 21 is similar to the head servo circuit 21 forming the main part of FIG. However, in this embodiment, the user uses a video camera (
The present invention is also applicable to the case where images are recorded using a method (not shown).

That is, in a stationary magnetic recording and reproducing apparatus such as the circuit shown in FIG. 1, the vertical synchronization signal in the television signal is used as the reference signal when recording television broadcasting, so the present invention Although it cannot be applied and is limited to playback only, when the user records with a camera-integrated VTR, the internal synchronization signal generator (S
Since the signal from SG) 22 is used, it is possible to obtain a reference signal from this signal, and the present invention can also be applied during recording.

This makes it possible to significantly shorten the time from when the user recognizes the recorded scene to when recording actually starts, and eliminates the need to record the scene that you want to record because of the delay in starting recording as in the past. Risk can be reduced.

Effects of the Invention As described above, according to the present invention, it is possible to synchronize the phase with the four quasi-signals as soon as the rotational speed of the magnetic head reaches a predetermined speed, so that it is possible to perform phase synchronization with the four quasi-signals at the same time as when the rotational speed of the magnetic head reaches a predetermined speed. It has the feature that it is possible to significantly shorten the time until playback and recording start.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
The timing charts of the signals at each point in the circuit shown in the figure, Figures 3 and 4 are for the reset switch...motor, 2...
- Pulse generation head, 5... Reset pulse generation circuit, 6... Reference signal generation circuit, 7... Crystal oscillator, 9
... Phase comparator, 17 ... FV conversion timing generation circuit, 21 ... Head servo circuit, SW+, SW2
, SW3... switch. Patent applicant: Victor Japan Co., Ltd. Patent attorney: Kaneyuki Matsuura
1・-”′ 1 ・, 1 , :rl ) L, i 2nd illustration IT2 5th ward

Claims (1)

[Claims] A rotation detection pulse obtained by detecting the rotation of a magnetic head that records or reproduces signals by rotating at a predetermined speed and a reference signal generated by a reference signal generation circuit are detected by a phase comparator. A head servo circuit that compares the phases and outputs an error signal, and controls the rotation of the magnetic head using the error signal to phase-synchronize the rotation of the magnetic head with the reference signal. a reset pulse generation circuit that resets the reference signal generation circuit by generating a synchronized reset pulse and supplying the reset pulse to the reference signal generation circuit; a reset means for passing or blocking a reset signal; and a reset means for passing a reset pulse before the rotation of the magnetic head reaches the predetermined rotation speed, and causing the rotation of the magnetic head to reach the predetermined rotation speed. and a reset timing generation circuit that interrupts the reset pulse by the reset means at the time when the magnetic head in the stopped state starts rotating until the rotation speed reaches around the predetermined rotation speed. The reset signal is passed through the reset pulse and is supplied to the reference signal generation circuit, and a signal of a predetermined level is outputted so that the magnetic head rotates at a predetermined number of rotations, and the rotation of the magnetic head reaches the predetermined number of rotations. A head servo circuit characterized in that the rotation of the magnetic head is phase-synchronized with the reference signal by cutting off the reset pulse by the reset means at the same time when .