JPH02123525A - Tracking control system for optical disk device - Google Patents

Abstract

PURPOSE:To attain correct signal reproduction immediately after a pull-in action is started by making the gain of a driving system in a moving means only for a prescribed time higher (lower) than the gain at the time of the ordinary action, at the time of rushing into a tracking condition. CONSTITUTION:In a first timing circuit 13, a tracking error signal from a tracking error signal from a tracking sensor 2 and the starting timing of a pull-in action from a tracking control system starting signal 12 are determined and the output signal from a circuit is added to an amplifier 14 with a gain switching circuit. Thus, the gain of the system of a linear motor 10 becomes temporarily high for a prescribed time, the follow-up quantity of the motor 10 for the disturbance becomes large and the follow-up quantity of a tracking actuator 6 is decreased. Next, when the gain of the system of the motor 10 is returned to an ordinary level, the follow-up quantity of the motor is reduced. Then, the timing, in which the follow-up quantity of the motor 10 for the disturbance is not reduced as much as possible, is selected, and when the gain is switched, the tracking control can be executed without increasing the follow-up quantity of the actuator 6.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a tracking control method for an optical disc device, and in particular, the present invention relates to a tracking control method for an optical disc device, and in particular, by irradiating a light beam onto an optical disc as a rotating recording medium, The present invention relates to a tracking control method for an optical disc device for accurately recording, reproducing, or erasing information.

[Prior Art] Figure 10 shows, for example, a collection of papers from the Optical Memory Symposium '85 held on December 12-13, 1985, p.
206 is a block diagram illustrating in more detail the tracking control method of the conventional optical disc device as shown in FIG. In this Figure 10, (2)
is a push-pull tracking sensor,
Detects the disc groove displacement (1) of the target optical disc and converts it into a corresponding voltage. (3) is a phase compensator that compensates the phase of the output of the preceding tracking sensor (2). (4) and (5) are the first and second amplifiers, respectively, for sequentially amplifying the output of the phase compensator (3), and (6) is a tracking actuator. and for converting the output of the second amplifier (5) into the first mechanical displacement.
(7) is an actuator equivalent circuit, which has the same frequency characteristics as the tracking actuator (6) and is connected to the output stage of the first amplifier (4), and (8) is a coupling circuit. a compensator for coupling and compensating the output of the preceding stage actuator equivalent circuit (7);
(9) is a third amplifier, which is used to appropriately amplify the output of the coupling compensator (8), and (10) is a linear motor, which is used to amplify the output of the third amplifier (9). It is for converting into mechanical displacement. Then, the first mechanical displacement, which is the output of the tracking actuator (6), and the second mechanical displacement, which is the output of the linear motor (10), are added to obtain the corresponding light spot displacement (11). can get. Thus, the tracking control system of the conventional optical disk device is comprised of various means from the tracking sensor (2) to the linear motor (10).

Next, the operation of the tracking control method of the conventional optical disc device having the above configuration will be explained.

Now, when the optical disc device is started up and the built-in tracking servo system is turned on, the deviation, which is the difference between the displacement (1) of the disc groove of the optical disc and the displacement (11) of the corresponding optical spot, is detected by the tracking servo system. It is detected by the sensor (2), and the tracking sensor (2) outputs it as a track deviation detection signal. This tracking
The track deviation detection signal from the sensor (2) is applied to the next stage phase compensator (3), and phase compensation is performed to stabilize the operation of the corresponding actuator system.
The output of this phase compensator (3) is sequentially amplified by a first amplifier (4) and a second amplifier (5), and then applied to a tracking actuator (6) in the subsequent stage, and is applied to its objective lens (not shown). ).

On the other hand, the output of the first amplifier (4) is also applied to the actuator equivalent circuit (7). Then, the output of this actuator equivalent circuit (7) is applied to the next stage coupling compensator (8) to perform coupling compensation, and the output of the tracking actuator (6) and the output of the linear motor (10) are combined. The output of this coupling compensator (8) is supplied to the third amplifier (9) in the next stage.
) and then applied to the linear motor (10) to drive the linear motor (10).

The sum of the mechanical displacement of one tracking actuator (6) and the mechanical displacement of the other linear motor (10) obtained as described above is the displacement (11) of the light spot. You will get it. and,
The displacement (11) of this light spot is negatively fed back to the front stage of the tracking sensor (2), and the displacement (11) of the light spot is
) follows the displacement (1) of the disk groove.

FIG. 11 is an explanatory diagram of the operation of the conventional tracking control method shown in FIG. 10, in which the shift of the objective lens corresponding to the amount of displacement of the tracking actuator (6) in this method and the displacement amount (B) of the linear motor (10).

As can be seen from FIG. 11, depending on the conditions at the time of retraction, such as the eccentricity of the disk used and the speed at which it enters the tracking state, the amount of lens shift immediately after the start of the retraction operation ( A) is the allowable range of lens shift amount due to sensor offset (W
) may be exceeded. In such a case, even if the tracking servo system is turned on, it is impossible to immediately and accurately reproduce the signal, and it is necessary to wait a certain amount of time in order to reproduce the desired and accurate signal. Time (0
-tl) is required.

[Problem to be Solved by the Invention] The conventional tracking control method for an optical disc device has the above-mentioned configuration, and it is difficult to control the amount of eccentricity of the disc being used, the speed at which it enters the tracking state, etc. Depending on the conditions at the start of the operation, the amount of shift of the objective lens in the tracking actuator immediately after the start of the retracting operation may exceed the allowable range of lens shift amount due to sensor offset. Even when the tracking servo system is turned on, it is impossible to immediately and accurately reproduce the signal, and a certain waiting time is required to reproduce the desired and accurate signal. There was a problem.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to accurately reproduce a signal immediately after the start of the pull-in operation, regardless of the conditions at the start of the pull-in operation. The purpose of this invention is to obtain a tracking control method for an optical disk device that can perform the following steps.

[Means for Solving the Problems] A tracking control method for an optical disc device according to the present invention includes: means for moving the optical disc in the radial direction, which is equipped with a tracking signal detection means and a tracking means;
The apparatus further includes a control means for controlling the moving means, and further includes means for switching a gain of a drive system in the moving means upstream of the moving means.

Further, a tracking control method for a different optical disk device according to the present invention includes a tracking signal detection means and a means for moving the optical disk in the radial direction on which the tracking means is mounted, and a control means for controlling the moving means. Furthermore, means for switching the gain of the drive system in the tracking means is provided upstream of the tracking means.

[Function] According to the present invention, when entering the tracking state, the gain of the drive system in the moving means (or the gain of the drive system in the tracking means) is higher than the gain during its normal operation (or be lowered).

Embodiment FIG. 1 is a block diagram showing a tracking control system for an optical disc device, which is a first embodiment of the present invention. In this FIG. 1, (13) is a first timing circuit, which outputs a tracking control system start signal (12),
This is for receiving the output signal from the tracking sensor (2) and generating a gain switching signal for the linear motor (10) system, which will be described later. <14) is an amplifier with a gain switching circuit, which is the third in the conventional example.
Instead of the amplifier (9), it is provided between the coupling compensator (8) and the linear motor (10). An acceleration sensor (15) is connected to the linear motor (10) and detects the acceleration of the linear motor (10).

(16) is a second timing circuit, which combines the output signal of the first timing circuit (13) and the acceleration sensor (15).
This is for applying a gain restoration signal to the amplifier with gain switching circuit (14) based on the output signal of. Components other than these are the same as the conventional example shown in FIG. 10 described above, so corresponding components are designated by the same reference numerals and detailed explanation thereof will be omitted.

Regarding the operation of the first embodiment with such a configuration, the second
This will be explained with reference to the figures. This second figure is similar to the first figure above.
FIG. 3 is a diagram illustrating waveforms of signals in each part of the embodiment. In addition,
Here, a case will be explained taking as an example a case where the operation is switched to the operation of the tracking control system after a seek operation is performed.

After the tracking control system start signal (12) shown in FIG. 2(a) is output, the first timing circuit (
In I3), the start timing of the pull-in operation is determined from the tracking error signal of FIG. 2(b) which is the output from the tracking sensor (2) and the tracking control system start signal (12). and a first timing circuit (13) as shown in FIG. 2(C).
The output signal from the amplifier is added to an amplifier H (14) with a gain switching circuit. FIG. 2(d) is an exemplary diagram of the gain in the amplifier with gain switching circuit (14), and (C1) represents the gain of the linear motor (10) system under normal operating conditions; Further, (G2) represents the gain that is increased over a predetermined period immediately after the start of the pull-in operation. Therefore, as described above, by applying the output signal from the first timing circuit (I3) to the amplifier with gain switching circuit (14), the linear motor (10)
The gain of the grid is temporarily increased over a certain predetermined time (t2-t3
) and rises to (G2). That is, by increasing the gain of the linear motor (10) system immediately after the start of the retracting operation, the amount of follow-up of the linear motor (10) with respect to the disturbance (one core of the disk) shown in FIG. 2(i) is , the change will occur as shown within the dotted line in FIG. 2(e). On the other hand, the tracking amount of the tracking actuator (6), which is the amount of shift of the objective lens in the tracking actuator (6>), changes as shown in FIG. 2(h).

Next, the linear motor (10
) The mode of setting the timing for switching the gain of the system to the normal gain (C1) will be explained. Second
As can be seen from the figure, when the gain of the linear motor (10) system is returned to the normal level (G1), the amount of follow-up of the linear motor (lO) to the disturbance decreases,
In contrast, the tracking amount of the tracking actuator (6) increases. Therefore, if the gain is switched by selecting a timing in which the tracking amount of the linear motor (10) with respect to disturbance does not decrease as much as possible, the tracking control system can be changed without increasing the tracking amount of the tracking actuator (6). can be stabilized. Also, when the kinetic energy is large, the linear motor (10) system is set to the normal gain (G1
), it is clear that the amount of overshoot increases.

As can be seen from the above, the best timing for gain switching is set as follows. That is, ■; the kinetic energy of the linear motor (10) is the maximum; ■; the difference between the tracking I of the linear motor (10) and the magnitude of the disturbance is the minimum; ■; the time until switching is the minimum, 3([
It is only necessary to set the timing so that condition 1 is satisfied at the same time. Taking the above into consideration, the best timing for gain switching is when the acceleration of the linear motor (10) first becomes zero, as shown in Figure 2(f), considering the time when the tracking state is entered. This is time t3.

In addition, FIG. 2(g) shows the signal from the second timing circuit (16) which is added to the amplifier with gain switching circuit (14) in order to return the gain of the linear motor (10) system to the normal gain (G1). 2 is a diagram illustrating a waveform of a gain restoration signal of FIG.

In this way, as shown in FIG. 2(h), the amount of tracking of the tracking actuator (6) can be suppressed as desired.

FIG. 3 is a block diagram showing a tracking control method for an optical disc device, which is a second embodiment of the present invention. In FIG. 3, (13) is a first timing circuit, which outputs a tracking control system start signal (12),
This is for receiving the output signal from the tracking sensor (2) and generating a gain switching signal for the tracking actuator (6) system, which will be described later.
(14) is an amplifier with a gain switching circuit, which is provided between the first amplifier (4) and the tracking actuator (6) in place of the second amplifier (5) in the conventional example. Components other than these are the same as the conventional example shown in FIG. 10 described above, so corresponding components are designated by the same reference numerals and detailed explanation thereof will be omitted.

Regarding the operation of the second embodiment with such a configuration, the fourth
This will be explained with reference to the figures. This figure 4 is based on the above 2nd figure.
FIG. 3 is a diagram illustrating waveforms of signals in each part of the embodiment. In addition,
Here again, a case will be described using as an example a case where the operation is switched to the tracking control system after the seek operation is performed.

After the tracking control system start signal (12) shown in FIG. 4 (a>) is output, the first timing circuit (1
In step 3), the start timing of the pull-in operation is determined from the tracking error signal of FIG. 4(b) which is the output from the tracking sensor (2) and the tracking control system start signal (12). Then, a first timing circuit (13) as shown in FIG. 4(c)
The output signal from the amplifier is applied to an amplifier (14) with a gain switching circuit. Figure 4(d) shows an amplifier with a gain switching circuit (
14), in which (G1) is the gain of the tracking actuator (6) in normal operating conditions;
It represents the gain of the system, and (G2) represents the gain lowered over a predetermined period immediately after the start of the pull-in operation. This gain switching is performed as follows. That is, the period (t4) from when the tracking control system is activated until the operation of the tracking actuator (6) system and the linear motor (10) system reaches a nearly steady state against disturbances such as eccentricity of the disk. - t5), the gain of the tracking actuator (6) system is set to the normal gain (Gl
) is set to a lower gain (C2).

In this way, the gain of the linear motor (10) system with respect to disturbance immediately after the start of the retracting operation becomes relatively high, and the linear motor (10) operates as shown in FIG. 4(e). Then, the tracking amount of the linear motor (10) system with respect to the disturbance as shown in FIG. 4(g>) increases, and correspondingly, as shown in FIG. 4(f), the tracking actuator ( 6) (I
The amount of lens shift as the amount of follow-up at I is suppressed.

Next, changes in the safety of the tracking control system due to gain switching as described above will be explained.

Figure 5 shows that the tracking control system has a normal gain (G1
) is an exemplary diagram of the pole arrangement when operating in FIG. 5 is a graph of a complex function in which the horizontal axis is the real number axis and the vertical axis is the imaginary number axis, and the plot on the complex plane represents the pole. Empirically, when the tracking control system is operating at the normal gain (G1), all the poles are on the left half side of the complex plane, and it is stable against disturbances of all frequencies. As can be seen, the conditions for a tracking control system that is included to the left of the line (z) representing 5 in -'0.3 and that operates stably are realized. This applies to both the first and second embodiments.

FIG. 6 is an illustrative diagram of the moving arrangement of the poles when the gain of the tracking control system is switched to (C2) for operation. As is clear from Fig. 6, the poles that move significantly due to gain switching are the poles shown as (A) in the figure and the characteristic function that mainly controls the response of the system closest to the origin. It is. This also applies to both the first and second embodiments.

FIG. 7 is an illustrative diagram of B-like movement of the pole (A) and the characteristic root in FIG. 6, and FIG.
Fig. 7(B) shows the movement of the characteristic root. What can be understood from this Figure 7 is that although the characteristic root moves in the direction of stability and high responsiveness, the pole (A) moves in the direction that the system becomes oscillatory, making the system unstable. This means that all you have to do is raise or lower the gain to the extent that it does not. This also applies to both the first and second embodiments.

FIG. 8 is an illustrative diagram of the displacement operation of the tracking actuator (6) when switching to the operation of the tracking control system after the seek operation in the first embodiment. In this Figure 8, the curve (^l) is the first
In the example, when the gain switching is performed at the timing t2, the tracking actuator (6
) is a waveform diagram representing the displacement operation of the tracking actuator (6), and the curve (^2) is a waveform diagram representing the displacement operation of the tracking actuator (6) when the gain switching described above is performed at a timing far away from t2. (A> is a waveform diagram for comparison, and is a waveform diagram of a conventional example in this invention.
FIG. 6 is a waveform diagram showing the displacement operation of the tracking actuator (6). Furthermore, as shown in Fig. 8 (C
) is the allowable range of lens shift amount due to sensor offset.

First, regarding the curve (A>), a waiting time of (t2-t6) is required until the curve falls within the above-mentioned tolerance range (C).On the other hand, the curve in the first embodiment Regarding (^1), this is within the permissible range (C) from the beginning, and therefore no waiting time is required.This means that the start signal for turning on the tracking control system is This indicates that it is possible to read the signal immediately after the bowing movement is started.However, when looking at another curve (Δ2), this is outside the allowable range (C). (t2-) until it falls within the permissible range (C).
t7) is required. For this reason, it is preferable that the timing of gain switching is at or near time L2, and when the timing of gain switching is far from time t2, a corresponding waiting time is required.

FIG. 9 is an illustrative diagram of the displacement operation of the tracking actuator (6) when switching to the operation of the tracking control system after the seek operation in the second embodiment. In FIG. 9, the curve (^1) is a waveform diagram representing the displacement operation of the tracking actuator (6) when the required gain switching is performed in the second embodiment, and the curve (A) 1 is a waveform diagram for comparison, and is a waveform diagram showing the displacement operation of the tracking actuator (6) in a conventional example according to the present invention.

Note that (C) shown in FIG. 9 is the allowable range of the lens shift amount due to the sensor offset. First, regarding curve (A), a waiting time of (t4-t8) is required until it falls within the above-mentioned tolerance range (C). On the other hand, regarding the curve (^1) in the first embodiment, it is within the permissible range (C) from the beginning, and therefore no waiting time is required. This indicates that the signal can be read immediately after the start signal for turning on the I-racking control system is issued and the required retracting operation is started.

In the first embodiment, an acceleration sensor <15) is used to detect the acceleration of the linear motor (10), but the present invention is not limited to this. The timing at which the acceleration of the linear motor (10) becomes zero may be detected based on the drive current (10). In this case, the timing at which the drive current of the linear motor (10) crosses zero corresponds to the timing at which the acceleration of the linear motor (10) becomes zero.

[Effects of the Invention] As explained above, the tracking control method for the optical disk device according to the present invention is such that when entering the tracking state, that is, at the start of the retracting operation, one of the moving means for tracking is activated. The structure is such that the gain of the signal that operates the linear motor system is temporarily increased until the acceleration of the moving means becomes zero for the first time. By suppressing the amount of lens shift by the actuator, so-called sensor offset can be significantly reduced.

Further, in the 1-racking control method of the different optical disk device according to the present invention, a tracking actuator as one of the moving means performs tracking at the time of entry into the tracking layer, that is, at the start of the retraction operation. It is configured to temporarily lower the gain of the signal that operates the system, and by suppressing the amount of lens shift by the tracking actuator, it is possible to significantly reduce so-called sensor offset.

As a result, the amount of lens shift by the tracking actuator as a moving means for tracking as described above can be reliably kept within the allowable range due to the sensor offset, and the waiting time after activation is not required. The effect is that the signal can be accurately reproduced immediately after the start of the pull-in operation without causing any problems.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a tracking control method of an optical disc device according to a first embodiment of the present invention, and FIG.
1st example diagram of signal waveforms in each part of the above embodiment, 3rd
FIG. 4 is a block diagram showing a tracking control method for an optical disc device according to a second embodiment of the present invention. FIG. 4 is a diagram illustrating waveforms of signals in each part of the second embodiment. FIGS. 5 to 7 is the operation associated with a change in the gain of the signal that drives the linear motor system or tracking actuator system in the first and second embodiments! 8 is an explanatory diagram of the operation of the tracking control system in the first embodiment, FIG. 9 is an explanatory diagram of the operation of the tracking control system in the second embodiment 4, and FIG. FIG. 11 is a block diagram illustrating a tracking control system of a conventional optical disc apparatus. FIG. 11 is an explanatory diagram of the operation of the conventional tracking control system. 2. Tracking sensor, 3. Phase compensator, 4. First amplifier, 5. Second amplifier, 6. Tracking actuator, 7. Actuator equivalent circuit, 8. Coupling compensator, 10. Linear motor, 13. 1st timing circuit, 14 amplifier with gain switching circuit, 15: acceleration sensor, 16: second timing circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts. 2nd map city 4th map (a) Nibushi d

Claims (2)

[Claims] (1) Tracking signal detection means for detecting a tracking signal indicating the irradiation position of the light beam with respect to a track on the optical disk: Tracking means for correcting the irradiation position of the light beam based on the detected tracking signal: The tracking signal detection means and a means for moving the optical disc in the radial direction by mounting at least a portion of the tracking means: and a control means for controlling the moving means: A tracking control method for an optical disc device, comprising: the tracking according to the tracking signal. The tracking operation is performed based on the control of the means and the moving means, and the gain of the drive system in the moving means is made higher than its normal gain for a predetermined period of time when entering the tracking state. , characterized in that the gain of the drive system in the moving means is restored to the normal gain when the acceleration of the moving means becomes zero for the first time after entering the tracking state or becomes close to zero. , a tracking control method for optical disk devices. (2) Tracking signal detection means for detecting a tracking signal indicating the irradiation position of the light beam with respect to a track on the optical disk: Tracking means for correcting the irradiation position of the light beam based on the detected tracking signal: The above-mentioned tracking signal detection means and tracking A tracking control method for an optical disc device, comprising: a means for moving in the radial direction of the optical disc by mounting at least a portion of the means; and a control means for controlling the moving means: the tracking means using the tracking signal; The tracking operation is performed based on the control of the moving means, and the gain of the drive system in the tracking means is made lower than its normal gain for a predetermined period of time when entering the tracking state. A tracking control method for an optical disk device, characterized by: