JPH0574079A - Track jump control device for optical disk device - Google Patents

Abstract

PURPOSE:To stabJy operate track jump by applying a control signal to a voltage control amplifier after the track jump back and increasing monotonously a track servo gain. CONSTITUTION:This device is constituted so that the output of a servo amplifier 1 receiving a tracking error signal and the output of waveform generating circuits 2, 12 performing the track jump back are switched by a switch SW1 and a switch SW2 and applied to a track coil 3. Then, a voltage control amplifier 11 is provided on the poststage of the amplifier 1, a track coil 3 is driven by the output of the amplifier 11 and simultaneously the coil 3 is driven by the output of the circuit 2 and the track jump back is performed. Thereafter, the control signal to be the output of the circuit 12 is applied to the amplifier 11 and the track servo gain is increased monotonously Thus, the track jump is operated stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track jump control device for an optical disk device. Generally, the tracks of an optical disc are formed in a spiral shape (spiral shape) as shown in FIG. 10 is a track. The direction of rotation is counterclockwise. The optical head (optical pickup) of the optical disk device continuously moves from the inner peripheral side to the outer peripheral side in the operating state.

By the way, in seeking (retrieving) recorded data, the optical head must stay at the same position in order to read data in a certain sector. Therefore, it is necessary to hold the optical head and perform tracking control (track jump back control) for one track for each rotation of the optical disk. In other words, it is necessary to perform jumpback control in which the head moves from the position B in the figure and returns to the position B when it reaches the position A.

[0003]

2. Description of the Related Art FIG. 5 is a diagram showing a conventional circuit example of a track jump control device. In the figure, 1 is a servo amplifier which receives a tracking error (TE) signal from an optical head (not shown), and 2 is a servo amplifier which receives an index signal generated for each rotation of the optical disk and generates a jumpback control signal. It is a waveform generation circuit.

Reference numeral 3 is a track coil, and 4 is a driver for driving the track coil 3. The output of the servo amplifier 1 is input to the input section of the driver 4 via the switch SW1, and the output of the waveform generation circuit 2 is input via the switch SW2. The switch SW1 is on (switch SW2 is off) when in the servo state, and the switch SW
2 is on during track jumpback operation (switch S
W1 is off). The operation of the circuit thus configured will be described below with reference to the time chart shown in FIG.

First, it is assumed that the optical head (hereinafter, simply abbreviated as a head) is located at the position B in FIG. At this time, the switch SW1 is turned on, the output of the servo amplifier 1 enters the driver 4, and the head is in the servo state as shown by the hatched portion in (g). The head gradually moves in the outer circumferential direction as the disk rotates, and after one rotation, the head of FIG.
Reach the position.

Here, an index signal, which is output once for each revolution of the disk, is generated at time t1 as shown in (a). As a result, the switch SW1 is turned from the previous ON to the OFF as shown in (b), and the switch SW2 is turned from the previous OFF to the ON as shown in (c). At this time, the track gain of the servo amplifier 1 is switched from high to low as shown in (d). During this time, the servo loop is disconnected.

On the other hand, the waveform generating circuit 2 receives the index signal and generates a track jump control signal composed of a forward pulse and a back pulse as shown in the period T2 of (g). Here, as the waveform generation circuit 2,
It can be easily realized by a combination of simple monostable multivibrators or a combination of counters.

This track jump control signal enters the driver 4 via the switch SW2, the driver 4 amplifies the current, and drives the track coil 3. As a result, the position of the head is forcibly returned from the position A in FIG. 4 to the position B, and the track jump back is performed. At this time, the track number is the relative position + as shown in (e).
It will return from 1 to 0.

During the track jump back period T2, the tracking error signal TE changes as shown in (f). At the time t2 when the track jump ends,
As shown in (b) and (c), the switch SW1 is turned on again and the switch SW2 is turned off again to return to the normal servo operation state. The track gain also returns to the original high state as shown in (d). The tracking error signal TE is (f)
As shown in (3), the transient state occurs for a certain period Δt, and then stabilizes.

[0010]

In order for the servo system to be immediately stabilized again after the track jump operation, the tracking error TE = 0, and the speed = 0 and the acceleration = 0 at the time t2. Is desirable. However, in reality, there are mechanical variations, and the speed and acceleration of the head in the track direction immediately before the jump are not 0 in most cases, so at the time t2, the track gain as shown in FIG. Setting to high makes the servo system unstable.

That is, during the period of Δt in FIG. 6, the head causes the maximum δ damping vibration with respect to the target track as shown in (f). Then, it becomes stable at time t3. In this case, during Δt, it becomes difficult to read the data from the disk surface normally, which is very inconvenient for the system operation. Further, depending on the situation, when the servo system is turned on after the jumpback, the head may oscillate in the track direction.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a track jump control device for an optical disk device which can stably perform a track jump operation.

[0013]

According to the present invention for solving the above-mentioned problems, first, the output of a servo amplifier which receives a tracking error signal and the output of a waveform generating circuit for performing track jumpback are switched by a switch. In the device configured to apply the voltage to the track coil, the voltage control amplifier is provided in the subsequent stage of the servo amplifier, the track coil is driven by the output of the voltage control amplifier, and the output of the waveform generation circuit is used. After the track coil is driven to perform the track jump back, a control signal is given to the voltage control amplifier to monotonically increase the track servo gain, and secondly, a tracking error signal is provided. The output of the servo amplifier that receives the data and the output of the waveform generation circuit that performs track jumpback In a device configured to switch with a switch to apply to the track coil, velocity and acceleration are detected from a position error signal from the optical pickup, a tracking error signal is also detected from the optical pickup, and positions of these optical pickups are detected. The track jumpback pulse width of the waveform generating circuit is determined from the speed and the acceleration.

[0014]

In the first aspect of the invention, after the track jump back is performed, a control signal is given to the voltage control amplifier to monotonically increase the track servo gain.
The second invention detects the tracking error signal and determines the track jump back pulse width of the waveform generating circuit from the position, speed and acceleration of these optical pickups. With such a configuration, the transition to the servo system after the track jump back can be smoothly performed, and the track jump operation can be stably performed.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a configuration block diagram showing an embodiment of the first invention. The same parts as those in FIG. 5 are designated by the same reference numerals. In the figure, 1 is a servo amplifier which receives a tracking error signal, and 10 is a timing generation circuit which receives an index signal and generates various timing signals.

Reference numeral 2 is a first waveform generating circuit for receiving the output of the timing signal 1 from the timing generating circuit 10 to generate a track jump signal, and 11 is a voltage control amplifier for receiving the output of the servo amplifier 1 (hereinafter referred to as VCA amplifier). Is. As the VCA amplifier 11, for example, a divider or an inexpensive electronic volume can be used. Reference numeral 12 is a second waveform generating circuit which receives the timing signal 2 of the timing generating circuit 10 and gives a VCA control signal for controlling the gain of the voltage control amplifier 11 to the VCA amplifier 11.

The output of the VCA amplifier 11 is the switch SW1.
To the driver 4, and the output of the waveform generating circuit 2 enters the driver 4 via the switch SW2. The driver 4 drives the track coil 3 according to the input signal. The operation of the circuit thus configured will be described below with reference to the time chart shown in FIG.

First, it is assumed that the optical head (hereinafter, simply abbreviated as a head) is located at the position B in FIG. At this time, the switch SW1 is turned on, and the output of the VCA amplifier 11 enters the driver 4. At this time, the gain of the VCA amplifier 11 is at a high level as shown in (g) of the VCA control signal, the track gain is at a high level as shown in (i), and the head is in the servo state. The head gradually moves in the outer circumferential direction as the disk rotates, and reaches the position A in FIG. 4 after one rotation.

Here, an index signal, which is output once for each revolution of the disk, is generated at time t1 as shown in (a). As a result, the switch SW1 is turned from the previous ON to the OFF as shown in (b), and the switch SW2 is turned from the previous OFF to the ON as shown in (c). At this time, the timing generation circuit 10 generates a timing signal 1 as shown in (e) and a timing signal 2 as shown in (f).

Of these signals, the timing signal 1 enters the waveform generating circuit 2, and the waveform generating circuit 2 outputs the forward pulse and the back pulse as shown in (d) during the period when the timing signal 1 is "1". A track jump control signal consisting of a pulse and a pulse is generated. As a result, the track jump control signal enters the driver 4 via the switch SW2, the driver 4 amplifies the current, and drives the track coil 3. As a result, the position of the head is
A track jump back is performed in which the track is forcibly returned from the position B to the position B. The track gain of the servo system switches from high to low as shown in (i). During this time, the servo loop is disconnected.

During the track jumpback period T2, the tracking error signal TE rings as shown in (h). At the time t2 when the track jump ends,
As shown in (b) and (c), the switch SW1 is turned on again and the switch SW2 is turned off again to return to the normal servo operation state.

Here, the timing generation circuit 10 is (f)
As shown in (g), the output of the waveform generation circuit 9 receiving the timing signal 2 has a characteristic that it increases monotonically from time t2. Such a monotonic increase characteristic can be realized by a simple CR charging circuit, or a method of inputting the output of the counter to the D / A converter may be used.

The VCA amplifier 11 receives this VCA control signal and similarly monotonically increases its gain. As a result, the track gain of the system is time t2 as shown in (i).
Since the servo gain has a characteristic that the track gain monotonically increases from time t2 to t3, tracking can be stably driven with high accuracy.

As described above, according to the first aspect of the present invention, stable tracking can be performed after the track jump back, and tracking can be stabilized within a short time after the jump.

FIG. 3 is a block diagram showing the essential parts of an embodiment of the second invention. The same parts as those in FIG. 1 are designated by the same reference numerals. In the figure, 20 is a speed detection circuit that receives a position error signal PE and differentiates it by one circuit to detect a speed, and 21 is an acceleration detection circuit that further differentiates the output of the speed detection circuit 20 to detect acceleration.

The position error signal PE will be described here. The deviation from the track position of the head (optical pickup) is the tracking error signal TE,
This TE signal is a relative position error signal. As the signal regarding the absolute position, the signal PE from the pickup is usually obtained as the absolute position signal.

Reference numeral 22 is an arithmetic circuit for inputting a TE signal, a speed signal from the speed detecting circuit 20 and an acceleration signal from the acceleration detecting circuit 21 to perform a predetermined arithmetic processing, and 2'is a timing generating circuit 10 (see FIG. 1). Is a waveform generation circuit which outputs a track jump control signal (track jump back pulse) in response to the timing signal 1 from the output of the waveform generator, and the output of which is input to the driver 4 via the switch SW2. The output of the arithmetic circuit 22 is given as a control signal for the waveform generating circuit 2 '. The operation of the circuit thus configured will be described below.

The point of the second invention is that the position, speed and acceleration of the pickup are detected and the pulse width of the track jump control signal is changed according to these values. As a result, the track position after track jump back is set to on-track (TE = 0), velocity = 0, and acceleration = 0. By doing so, it becomes possible to quickly shift to stable tracking after the jump.

The PE signal is differentiated by the speed detection circuit 20 to obtain the speed signal i, and the speed signal i is further differentiated by the acceleration detection circuit 21 to obtain the acceleration signal j. These speed detection circuit 2
As the 0 and the acceleration detection circuit 21, a so-called resistor and capacitor CR differentiating circuit can be used. That is, the speed detection circuit 20 and the acceleration detection circuit 21 can use the same circuit.

Here, assuming that the TE signal is h, the TE signal h, the velocity signal i and the acceleration signal j are input to the arithmetic circuit 22 and are arithmetically operated. Here, the calculation of the calculation circuit 22 is usually performed with respect to the pulse width. The arithmetic expression is represented by the following expression, for example.

Tw = T-Ah-Bi-Cj (1) Here, Tw is a pulse width to be obtained, and T, A, B, and C are constants. The pulse width Tw calculated by the arithmetic circuit 22 is input to the waveform generating circuit 2'as a control signal. The waveform generating circuit 2'performs track jumpback with the pulse width Tw obtained by the equation (1). As a result, position error after track jumpback = 0, velocity = 0, acceleration = 0,
It is possible to shift to stable tracking.

In the above embodiment, the case where the pulse width of the track jump control signal is controlled according to the position, speed and acceleration is taken as an example. However, the present invention is not limited to this, and the amplitude of the track jump control signal can be changed according to the position, velocity and acceleration. In this way, the track jump control signal can be generated using at least one of the pulse width and the pulse amplitude, or both.

[0033]

As described above in detail, according to the present invention, firstly, the track gain is monotonically increased immediately after the track jumpback, and secondly, the track jump control signal is set to the position error after the track jumpback. =
Provided is a track jump control device for an optical disk device, which can perform a track jump operation in a stable manner by varying the pulse width or / and the pulse amplitude of the track jump control signal such that 0, velocity = 0 and acceleration = 0. can do.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of a first invention.

FIG. 2 is a time chart showing the operation of each part of the circuit shown in FIG.

FIG. 3 is a configuration block diagram showing a main part of an embodiment of the second invention.

FIG. 4 is a diagram showing a track shape of an optical disc.

FIG. 5 is a block diagram showing a conventional circuit example of a track jump control circuit.

FIG. 6 is a time chart showing the operation of each unit of the conventional circuit.

[Explanation of symbols]

 1 Servo Amplifier 2 Waveform Generation Circuit 3 Track Coil 4 Driver 10 Timing Generation Circuit 11 VCA Amplifier 12 Waveform Generation Circuit SW1 Switch SW2 Switch

Claims (2)

[Claims] 1. A device configured to apply a switch coil between an output of a servo amplifier that receives a tracking error signal and an output of a waveform generation circuit for performing track jumpback and apply the same to a track coil. A voltage control amplifier is provided in the subsequent stage so that the track coil is driven by the output of the voltage control amplifier, and the track coil is driven by the output of the waveform generating circuit to perform track jumpback, and then the voltage A track jump control device for an optical disk device, characterized in that a control signal is applied to a control amplifier to monotonically increase the track servo gain. 2. An apparatus configured to apply a switch coil between an output of a servo amplifier that receives a tracking error signal and an output of a waveform generating circuit for performing track jumpback and apply the same to a track coil. The velocity and acceleration are detected from the position error signal of the optical pickup, the tracking error signal is also detected from the optical pickup, and the track jump back pulse width of the waveform generating circuit is determined from the position, velocity and acceleration of the optical pickup. A track jump control device for an optical disk device, characterized in that