JPH0240158A - Servo device for magnetic recording/reproducing device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of disturbance in a picture image at a concatenating spot of shifting a reproducing operation to a recording operation by performing a servo operation with a phase error output based on a 1st control signal for the reproducing period of time just prior to the changeover from the reproducing operation to the recording operation during the transient time of the changeover. CONSTITUTION:The servo device is provided with a control head 3, capstan motor 4, reel motor 5, frequency generator 7, frequency divider 8, changeover switch SW1, delay 22, phase error detector 21, reference data generating circuit 23, clock generating circuit 24, shunting register 26, changeover switch SW2, error output circuit 27, drive circuit 28 and processing circuit 29. Then, at the transient time of the changeover from the reproducing operation to the recording operation, a phase error of a 2nd control signal is detected during the servo operation with the phase error output based on the 1st control signal for the reproducing period of time just prior to the changeover, and upon detection of this phase error, the changeover is made to the servo operation based on the phase error of the 2nd control signal. By this method, the need for constituting synchronization between the 1st and 2nd control signals is eliminated, while the occurrence of disturbance in the picture image at the concatenating spot for the operation shift is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a servo device suitably implemented as a drum servo, capstan servo, etc. of a video tape recorder, which is a magnetic recording/reproducing device.

In conventional video recorders, in order to reliably reproduce the recorded information, control (hereinafter referred to as
CTL) signal is recorded by a fixed head. During recording, this CTL signal is created based on, for example, the rotational speed of the capstan motor, and is written at equal intervals for each frame. On the other hand, during reproduction, this CTL signal is read out and a reproduction operation is performed based on the CTL signal. However, the intervals of the read CTL signals contain error components due to expansion and contraction of the magnetic tape due to moisture, slippage caused by the drive mechanism, changes in tension, and the like.

For this reason, this error component is detected and servoing of the capstan, drum, etc. is performed based on the error output.

In a typical conventional technique, as shown in Japanese Patent Publication No. 49-18805, the CTL signal read out during playback operation and the output from a capstan motor, for example, to be written when the recording state is entered. A synchronization circuit always maintains synchronization between the two. In other words, Figure 3 (2)
During the 1/30 second interval of the CTL signal shown in Figure 3 (1), pulses are derived from a frequency generator attached to, for example, a capstan motor. The pulse is frequency-divided by a frequency divider, for example, to 1/12, and recorded as the CTL signal during recording. That is, when the CTL signal is read out, the count value of the pulse is reset, and when the count value reaches the frequency division ratio of 12, the CTL signal to be recorded is derived.

Problems to be Solved by the Invention Therefore, when the magnetic tape is temporarily stopped from the playback operation by a so-called pause operation and switched to the recording operation,
And when the recording operation is restarted again after the recording operation is paused, the same thing happens when the recording operation is resumed from the playback operation. At the time when the above-mentioned - time stop operation is performed, the operation is once switched to the playback operation, and the above-mentioned CTL signal is read.
CT read out from magnetic tape for synchronization
The CTL signal l\, which is generated based on the frequency generator, is switched from the L signal. Therefore, at the moment when the recording operation is restarted, the gap between the two CTL signals is at most 1/(30
A phase error of X12>seconds may occur, resulting in disturbances at the seam of images. Furthermore, a configuration is required for synchronizing the CTL signal read as described above and the output of the frequency generator which becomes the CTL signal written.

An object of the present invention is to provide a servo device for a magnetic recording/playback device that can eliminate image disturbances caused by switching CTL signals when switching from playback operation to recording operation, and that has a simplified configuration. It is to be.

Means for Solving the Problems The present invention performs a servo operation based on a first control signal recorded on a magnetic recording medium during reproduction, and performs a servo operation during recording based on the output of a drive means for driving the magnetic recording medium. In a servo device of a magnetic recording/reproducing apparatus, the first control signal is generated and recorded on a magnetic recording medium as the first control signal, and a servo operation is performed. phase error detection means for comparing the second control signal with the reference signal during recording and detecting a phase error of these first or second control signals; and temporarily storing the output of the phase error detection means. a storage means for selectively switching between the output from the phase error detection means and the output from the storage means and deriving it as a servo output; and during normal reproduction and recording, the switching means is electrically connected to the phase error detecting means side, and the output from the phase error detecting means is derived as a servo output, and when moving from the reproducing operation to the recording operation, the switching means is once electrically connected to the storage means side, and the output from the phase error detecting means is derived as a servo output. At the same time, the output from the storage means is derived as a servo output, the comparison operation for the first control signal in the phase error detection means is stopped, the comparison operation for the second control signal is started, and the phase of the second control signal is determined. A magnetic recording/reproducing apparatus characterized by comprising: control means for switching the switching means again to the phase error detection means side when an error is detected, and deriving the phase error of the second control signal as a servo output. This is a servo device.

According to the present invention, during reproduction, a servo operation is performed based on the first control signal recorded on the magnetic recording medium, and during recording, the servo operation is performed based on the output of the driving means for driving the magnetic recording medium. The servo operation is performed by the second control signal. Also, during this recording, the second control signal is recorded on the magnetic recording medium as the first control signal.

During normal playback, the control means detects a phase error of the first control signal by comparing the first control signal with a predetermined reference signal in the phase error detection means, and the phase error thus detected is used for switching. The output signal is outputted to the drive means as a servo output during the normal reproduction.

Further, during normal recording, the control means detects the phase error of the second control signal by comparing the second control signal with a predetermined reference signal in the phase error detection means, and detects the phase error of the second control signal through the switching means. The signal is output to the driving means as a servo output during recording.

On the other hand, the output of the phase error detection means is given to a storage means, and the storage means sequentially updates and temporarily stores the output from the phase error detection means.

When recording is paused and then resumed,
When the reproducing operation shifts to the recording operation, the control means temporarily connects the switching means to the storage means side and derives the first control signal stored in correspondence with the previous reproducing operation as a servo output; During this time, the second control signal is given to the phase error detection means, and when a servo output corresponding to the phase error of the second control signal is created, the control means detects the phase error from the storage means side. Switching to the detection means side, the phase error of the generated second control signal is derived as a servo output.

Therefore, during the transition period when switching from playback operation to recording operation, the servo output is
This is due to a phase error based on the control signal, and while the servo operation is being performed by this error output, the phase error of the second control signal is detected, and at the time the phase error of the second control signal is detected. , switching to servo operation is performed based on the phase error of the second control signal. This allows the first
There is no need for a configuration for synchronizing the control signal and the second control signal, and high-precision servo operation can be performed without causing image disturbance at the transition from playback operation to recording operation. .

Embodiment FIG. 1 is a block diagram showing the electrical configuration of a capstan servo device 1 of a video tape recorder according to an embodiment of the present invention. This servo device 1 operates from a CTL rack formed at one end of a magnetic tape 2, which is a magnetic recording medium, extending in the longitudinal direction of the magnetic tape 2, by a CTL head 3 provided at a fixed position. The CTL signal, which is a control signal, is read out, or the CTL signal is read out.
- A second control signal, the CTL signal, is written to the rack.

During recording or reproduction, the magnetic tape 2 is driven to run at a predetermined constant speed by a capstan motor 4 under servo control as described later, and wound onto a reel 6 that is rotationally driven by a reel motor 5. taken. The magnetic tape 2 is also driven by a reel motor 5 for fast forwarding or rewinding.

A frequency generator 7 is attached to the output shaft of the capstan motor 4, and the pulse output from the frequency generator 7 is frequency-divided by a frequency divider 8 to produce a second control signal C T
As the L signal, one individual contact 1 of the changeover switch SW1
1 is given. The CTL signal from the CTL head 3 is applied to the other individual contact 12 of this changeover switch SWI.

The CTL signal with a period of approximately 1/30 seconds, which is thus derived to the common contact 13 of the changeover switch SWI, is provided as phase error data 1 to trigger pulses of the phase error detector 21, which will be described later, via the line 18. 19
The signal is delayed through a delay device 22 and provided as a tri-pulse for the phase error detector 21 to read reference data from a reference data generation circuit 23, which will be described later. Therefore, the delay device 22 operates as a latch circuit for the input signal, thereby controlling the sampling operation of the reference data of the phase error detector 21.

This phase error detector 21 also includes a tarlock generation circuit 24.
The phase error detector 21 receives the CTL signal from the reference data generation circuit 23 in response to the trigger pulse of the CTL signal via the delay device 22.
The reference data is read without indicating the number NO of the reference clocks to be counted during one period of the signal.

When the reference data NO is read in this way, the phase error detector 21 counts down the reference data NO every time the reference clock is input, and
When the number of pulses of the reference clock 7 input during the period is N1, the phase error detector 21 outputs phase error data corresponding to the difference between the reference data No. and the number of pulses N1 of the reference clock. For example, the binary code is the CT
line 25 in response to the trigger pulse of the L signal.

This binary code is selected to take an intermediate value when N1=NO, and corresponds to the amount of error in both cases, N1>NO and N1<NO. The exact value can be derived.

The phase error data thus derived on the line 25 is applied to one individual contact 14 of the changeover switch SW2, and is also written into a save register 26, which may be implemented, for example, by a random access memory. The output of this save register 26 is the output of the changeover switch SW.
2 to the other individual contact 15.

The phase error data derived to the common contact 16 of the changeover switch SW2 is provided to an error output circuit 27. In this error output circuit 27, the phase error data is subjected to, for example, pulse width modulation (hereinafter abbreviated as PI3WM) or digital or analog (hereinafter abbreviated as D//'A) conversion, The thus converted output controls the rotational direction and speed of the capstan motor 4 via the drive circuit 28.The drive circuit 28 acts as a low-pass filter when PWM conversion is performed in the error output circuit 27. It also has the function of an amplifier when D/A conversion is performed.

The switching states of the changeover switches SWI and SW2 are controlled by two processing circuits, and an input circuit 30 is provided in connection with these two processing circuits. From this input circuit 30, operation commands such as the aforementioned fast forwarding or rewinding, or recording or reproducing operation are input. The two processing circuits also control write (update) and read operations of the save register 26 in synchronization with the output of phase error data from the phase error detector 21, and also supply reference data No. to the reference data generation circuit 23. and controls the output of the error output circuit 27 during special playback such as slow playback.

For example, when a fast forward or rewind command is input as described above at time to, the reel motor 5 is driven as shown in FIG. 2 (4), and the magnetic tape 2 is driven to fast forward or rewind at high speed. Ru. At this time, the two processing circuits switch the changeover switch S as shown in FIG. 2 (2).
WI is electrically connected to the individual contact 12 side, and changeover switch SW2 is electrically connected to the individual contact 14 side as shown in FIG. 2 (3).

At time t1, when a reproduction operation command is input from the input circuit 30, the reel motor 5 is driven and the magnetic tape 2 is
is driven to travel. At time t2, when the CTL signal is detected as shown in FIG. 2 (5), phase error data is derived from the phase error detector 21 as shown in FIG. 2 (8), and Time 3 delayed by a predetermined time T from time t2 by the delay device 22
2, the reference data NO from the reference data generation circuit 23 is input to the phase error detector 21 as shown in FIG.
is loaded.

As a result, the phase error detector 21 from the groove 3 performs counting and counting of the reference data No. every time the reference clock 7 shown in FIG. 2 (1) is input, and at time t.
4, as shown in Figure 2(5), the following CTL
When the signal is read out and the reference data NO is read again at time t5 as shown in FIG. Phase error data is created based on the difference between N1 and the reference data NO. ,
The rotational speed of the capstan motor 4 is controlled via the error output circuit 27 and the drive circuit 28. For example, when the error output circuit 27 is a D/A converter and the output is NO/N1, the rotational speed of the capstan motor 4 is controlled to increase as shown in FIG. 2 (9). In this way, cab stan servo during regeneration is realized.

As described above, when a pause and recording command is input from the input circuit 30 at the time opening 6 while the playback operation is being performed, the changeover switch SWI changes to the individual contact 11.
As a result, as shown in FIG. 2 (3), the changeover switch SW2 conducts to the individual contact 15 side.
Phase error data stored in the save register 26 is derived to an error output circuit 27. At this time, the changeover switch SWI is connected to the individual contact 1 as shown in Fig. 2 (2).
Conducted to the 1 side.

At time t7, when the CTL signal from the frequency generator 7 whose frequency has been divided by the frequency divider 8 is derived as shown in FIG. 2 (6), the phase error detector 21 detects the C'T, L
Create error data based on the signal and select switch SW
2 individual contacts] is derived in 4. This changeover switch sw2
is conductive to the individual contact 14 side from time t7 when the CTL signal via the frequency divider 8 is derived to time t8 when reading of the phase error data stored in the save register 26 is completed. However, after time t8, the C T derived from the frequency divider 8
Based on the L signal, a servo operation of the capstan motor 4 is performed, and the CTL signal is recorded in the magnetic data 2 from the CTL/\\nd 3 by a configuration not shown.

In this way, even when switching from the playback operation to the recording operation at the time gap 6, the phase error is detected by the CTL signal derived from the frequency generator 7 via the frequency divider 8. Until the read operation of the reference data NO of the device 21 is reset and the phase error data for the CTI- signal is generated, the save register 26 is
-2! according to the last phase error data during the playback operation that is being performed. Since the servo operation of the capstan motor 4 is performed, the servo operation of the capstan motor 4 can be performed with high precision without phase shift even when switching from the playback operation to the recording operation I\.

In addition, as mentioned in the prior art section, there is a complex synchronization circuit between the CTL signal detected by the CTL head 3 and the signal detected by the frequency photoelectric device 7. This eliminates the need for a configuration, simplifies the configuration, and uses the above-mentioned PWM converter and LPF, or D/A converter and amplifier, etc. for the error output circuit 27 and the drive circuit 28, so that so-called digital Servos can be realized. At this time, by making the address from which the output from the phase error detector 21 is derived different from the address from which the output from the save register 26 is derived, a so-called software can be used instead of the changeover switch SW2. switching control is possible, and the configuration can be further simplified.

Effects of the Invention As described above, according to the present invention, at the time of transition when switching from reproducing operation to recording operation, the servo output is due to the phase error based on the first control signal during the reproducing period immediately before the switching. While the servo operation is being performed by the error output, a phase error of the second control signal is detected, and at the time the phase error of the second control signal is detected, the servo operation is performed based on the phase error of the second control signal. Since the operation is switched, there is no need for a configuration for synchronizing the first control signal and the second control signal, and image distortion occurs at the joint where the playback operation changes to the recording operation. Highly accurate servo operation can be performed without any trouble.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the electrical configuration of a servo device 1 according to an embodiment of the present invention, FIG. 2 is a timing chart for explaining the operation, and FIG. 3 is a waveform for explaining the operation of the conventional technology. It is a diagram. 1... Servo device, 2... Magnetic tape, 3... C
TL head, 4... Capstan motor, 5... Reel motor, 7... Frequency generator, 8... Frequency divider,
21... Phase error detector, 22... Delay device, 23.
... Reference data generation circuit, 24 ... Clock generation circuit, 26 ... Save register, 27 ... Error output circuit, 28 ... Drive circuit, 29 ... Processing circuit, 30 ...
Input circuit, 5WISW2... Changeover switch agent Patent attorney Stroke number Keiichi

Claims (1)

[Claims] During reproduction, a servo operation is performed based on a first control signal recorded on a magnetic recording medium, and during recording, a second control signal is created based on the output of a driving means for driving the magnetic recording medium. In a servo device of a magnetic recording/reproducing device, the first control signal is recorded on a magnetic recording medium as the first control signal, and the servo device performs a servo operation. phase error detection means for comparing the second control signal with the reference signal during recording and detecting a phase error of these first or second control signals; storage means for temporarily storing the output of the phase error detection means; Servo output by selectively switching the output from the phase error detection means and the output from the storage means. During normal playback and recording, the switching means is connected to the phase error detection means to derive the output from the phase error detection means as a servo output, and during normal playback and recording, the output from the phase error detection means is derived as a servo output, and When moving to a recording operation, the switching means is once connected to the storage means, and the output from the storage means is derived as a servo output, and the comparison operation with respect to the first control signal in the phase error detection means is stopped. , starts a comparison operation for the second control signal, and when a phase error of the second control signal is detected, switches the switching means to the phase error detection means side again to detect the phase error of the second control signal. 1. A servo device for a magnetic recording/reproducing device, comprising: control means for deriving a servo output.