JPS62277633A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To shorten the access time by reducing the servo gain of a fine actuator system at a low frequency band and, at the same time, inhibiting the reduction of the servo gain of said actuator system in a pull-in period of the tracking servo action. CONSTITUTION:A switch 7 is turned on to turn on the control signal Cdown of a servo gain reduction means 6. Thus a rough actuator system works and the means 6 works with a fine actuator system. Then the servo gain is reduced at a low frequency band of a fine actuator 2. Here the gain of the low frequency band of a rough actuator system is sufficiently larger than that of a fine actuator system. Thus a rough actuator 3 substantially follows up the large displacement component of a low frequency of a track 9. While the displacement of the actuator 2 is reduced immediately when the rough actuator system has a servo action even though a tracking servo pull-in action is carried out in a state where the actuator 2 has a large displacement in an access mode. Thus the access time is shortened to attain a high-speed access.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an optical information recording/reproducing device.

(Prior Art) In an optical information recording/reproducing apparatus using an optical disk having spiral or concentric tracks, an optical pickup optical system focuses a light beam onto the track to record information on the track. Alternatively, methods for reproducing recorded information are known. In such a recording and reproducing system, focusing servo control is performed to accurately focus the light beam onto the trunk, and tracking servo control is performed to align the focused position of the light beam with the track.

In tracking servo control, a so-called parallel control method using a fine actuator and a coarse actuator is known in order to control the position of a light beam with higher precision.

FIG. 5 shows a schematic configuration of a tracking servo control system using conventional parallel control.

The deviation between the light beam a and the track C on the optical disc b is detected by the optical pickup d, and a tracking error signal (TE
S) is generated. The tracking error signal (TBS) is applied to the fine actuator g and the coarse actuator h through respective phase compensation circuits e and f in respective servo loops. Generally, the gain curves of both are determined as shown in FIG. 6 so that the low frequency large displacement component of the trunking error is followed by the coarse actuator h, and the high frequency small displacement component is followed by the fine actuator g.

(Problem to be solved by the invention) By the way, the coarse actuator h is used for the target track C.
In many cases, it also serves as a so-called access mechanism for locating. During access, the coarse actuator h
performs relatively rapid acceleration and deceleration, so the fine actuator g located above it is greatly displaced by the inertial force based on the mass of its moving part, or vibrates when it is excited by the coarse actuator h. or Therefore, when the tracking servo is pulled in immediately after the so-called rough access by the rough actuator h is completed,
As shown in Fig. 7, there is a possibility that the tracking servo is applied when the precision actuator g is largely displaced, and in such a state, the tracking error signal (TES
) an offset occurs. FIG. 8 Tal shows a state in which the offset has occurred in the negative direction, FIG. 8(b) shows the normal state, and FIG. 8(C) shows the state in which the offset has occurred in the positive direction. For example, in the offset state shown in Figure 7, the tracking servo is activated as shown in Figure 8 (C
), and normal tracking servo control cannot be performed.

Of course, if the servo operation of the coarse actuator h is started after the tracking servo pull-in of the fine actuator g, and a so-called parallel control state is established, the coarse actuator h will control the displacement of the fine actuator g by following in the X direction in FIG. The offset can be reduced to eliminate the offset. The speed at which this offset disappears varies depending on the gain of the servo, especially the gain of the coarse actuator system in the low frequency range. For example, consider a case where the gain of the precision actuator system is relatively large in the low frequency range, as shown in FIG. 9, where the servo gain curve during parallel control is shown. In this case, since the fine actuator g follows the low frequency component of the displacement of the track C relatively well, the amount of tracking by the coarse actuator h becomes small. In other words, it takes time to eliminate the above-mentioned offset. Therefore, during access, it takes a relatively long time from the end of coarse access to the normal trunking control state, making it difficult to shorten the access time. Furthermore, even when disturbance vibration is applied, the fine actuator g follows relatively well in order to cancel it, and the coarse actuator h follows only a small amount. In other words, the displacement of the fine actuator g is large and the problem of offset occurs, so that normal tracking control cannot be performed.

In order to prevent these phenomena, the low frequency gain of the fine actuator system is made extremely low as shown in Fig. 10. First of all, the resonance frequency f of the fine actuator g,
It is difficult to achieve this because the tracking servo needs to be extremely high.Secondly, from the time immediately after the tracking servo is pulled in by the fine actuator system until the servo operation of the coarse actuator system starts, the fine actuator system alone is required to keep track of the trunk displacement. The gain required for this tracking (10th
This was virtually impossible for a variety of reasons, including the need to ensure the precision actuator system alone (see the broken line in the figure).

(Means for Solving the Problems) The optical information recording and reproducing apparatus of the present invention records information by focusing a light beam on the tracks of an optical disk in which tracks are formed in a spiral or concentric pattern, or This is an optical type that reproduces recorded information, and tracking servo control for aligning the focused position of the light beam with the trunk is performed by a two-stage actuator system: a fine actuator system and a coarse actuator system. In the information recording and reproducing device, the servo gain of the precision actuator system is reduced in a low frequency range, and
During the tracking servo pull-in period, reduction of the servo gain of the precision actuator system can be prohibited.

(Function) Tracking servo control is performed by a fine and coarse two-stage actuator system. At this time, by reducing the servo gain of the fine actuator system in the low frequency range, the tracking amount of the coarse actuator in the low frequency range is made sufficiently larger than the tracking amount of the fine actuator. Furthermore, the servo gain reducing operation can be prohibited during the tracking servo pull-in period. When servo gain reduction is thereby prohibited, the servo gain of the fine actuator will be greater than the gain required for trunk tracking.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of a tracking servo system in an optical information recording/reproducing apparatus.

■ is an optical pickup, and trunk 9 of optical disk 8
to detect the positional deviation between the two by focusing the light beam 10 on the
Based on this, a tracking error signal (TBS) is generated. The tracking error signal (TBS) is applied to the coarse actuator 3 via the phase compensation circuit 5 and the switch 7, and to the fine actuator 2 via the phase compensation circuit 4 and the servo gain reduction means 6. The servo gain reduction means 6 is for reducing the servo gain of the precision actuator system in a low frequency range.

The low frequency range refers to a frequency range lower than the resonance frequency f1 of the gain curve of the precision actuator system. The switch 7 is used to turn on/off the operation of the coarse actuator system.

The control means 11 controls the 0N10FF of the switch 7, and also controls the servo gain reduction means 6 with the control signal Qd o
It is controlled by wn. FIG. 2 shows the control means 1
1 shows a frequency characteristic diagram of the servo gain reduction means 6 of the precision actuator system according to the control signal Gdown from 1. In the figure, the control signal Gdown from the control means 11 is OFF.
The gain curves of the above-mentioned reducing means are shown in the case where the control signal Gdown is turned on and the case where the control signal Gdown is turned on. Here, the control signal G
d.

The case where wn is OFF means that the servo gain reducing means 6 is prohibited, and the case where the control signal Qdown is ON means that the servo gain reducing means 6 is activated. When the control signal Gdown is in the ON state, the servo gain curve has two corner frequencies of 1° f2, and there is a constant gain from DC to the lower corner frequency f, and from this corner frequency f1 It has a linearly increasing gain characteristic up to the higher corner frequency f2, and has the same gain as when the control signal Gdown is in the leaf F state at the corner frequency 12 or higher.

Next, the operation of the tracking servo system configured as described above will be explained.

When the tracking servo is pulled in, the control means 11 first turns off the switch 7 and turns off the control signal Gdown of the servo gain reduction means 6.
In this case, the coarse actuator system does not operate and only the fine actuator system follows the displacement of the track. At this time, the precision actuator system is operated by the servo gain reducing means 6.
does not operate, that is, the operation of the servo gain reducing means 6 is prohibited, and the servo gain curve becomes like the solid line shown in FIG. The figure shows a servo gain curve of the precision actuator system, and this servo gain curve also has a resonance point at the resonance frequency f3.

The broken line shows the servo gain curve required for track following, which has a smaller gain than the precision actuator system servo gain in the entire frequency range. In other words, if the required servo gain curve is the broken line shown in the figure, it will be possible to follow the displacement of the track 9 using only the precision actuator system.

However, at this time, the displacement of the precision actuator 2 is large,
Due to the offset problem mentioned above, it is still difficult to record and reproduce information normally.

Next, the control means 11 turns on the switch 7, and the control signal Gdo of the servo gain reduction means 6 is turned on.
When wn is turned on, the coarse actuator system is operated, and the servo gain reduction means 6 is operated in the fine actuator system, so that the gain of the fine actuator 2 is reduced in the low frequency range. These servo gain curves are shown in FIG. The figure shows a coarse actuator-based servo gain curve and a fine actuator-based servo gain curve. The precision actuator system servo gain curve has a first corner frequency f and a second corner frequency "2" in a frequency range lower than the wave number f for resonance.

The first turning point frequency r is lower than the gain required for tracking shown in the same figure, and this low amount is compensated for by the servo gain of the coarse actuator system.

At the second corner frequency r2, the gain is higher than the gain required for tracking. Therefore, the gain of the coarse actuator system in the low frequency range is sufficiently larger than the gain of the fine actuator system in the low frequency range, and the coarse actuator 3 almost follows the low frequency large displacement component of the track 9. Therefore, the displacement of the precision actuator 2 is small, and the problem of offset generation on the tracking control '+B signal (TES) does not occur, allowing normal tracking control, that is, normal recording and reproduction of information. Furthermore, since the coarse actuator 3 follows most of the disturbance vibrations, the problem of offset generation does not occur.

Furthermore, even if the tracking servo is pulled in when the fine actuator 2 is largely displaced during access, as soon as the coarse actuator system joins the servo operation, it will be driven to reduce the displacement of the fine actuator 2. The waiting time until normal recording and reproduction of information becomes possible is shortened, and high-speed access becomes possible.

(Effects of the Invention) As described above, according to the present invention, not only the access time can be shortened, but also information can be recorded and reproduced in a good state even against disturbance vibrations, and the present invention is suitable.

[Brief explanation of the drawing]

1 to 4 show an optical information reproducing device of the present invention and characteristic diagrams of this device, FIG. 1 is a schematic configuration diagram showing a tracking servo control system, and FIG. 2 is a control means 11.
Frequency characteristic diagram of the servo gain reduction means of the precision actuator system controlled by the control signal Gdown from
The figure shows a characteristic diagram showing the gain curve when the servo gain of the precision actuator system is not reduced in the low frequency range, that is, the reduction operation is prohibited. Figure 4 shows the servo gain reduction means of the precision actuator system operating during parallel control. 5 to 10 show a conventional optical information recording/reproducing device and characteristic diagrams of this device, and FIG. 5 is a schematic configuration diagram showing a conventional tracking servo control system. , FIG. 6 is a characteristic diagram showing the servo gain curve, FIG. 7 is a state explanatory diagram showing a state in which the precision actuator is largely displaced during access, FIG. 8 is an explanatory diagram showing the offset that occurs in the tracking error signal at that time, and FIG. 9
The figure is a characteristic diagram showing a servo gain curve when the low frequency gain of the precision actuator system is relatively large, and Figure 10 is a characteristic diagram showing the servo gain curve when the low frequency gain of the precision actuator system is extremely low. . l... Optical pickup 2... Fine actuator 3... Coarse actuator 4.5... Phase compensation circuit 6... Servo gain reduction means 7... Switch 8... Optical disk 9...
・Truck 10...Light beam 11...Control means Fig. 1 and Fig. 2 fr/2! I'll Kai--Nakayu 3 figure f2 Zhou'1a- t#t Risen, Eta co-reflection J1 no Ki 4 figure +1 1 ft b fa Zhou = Ja-fa of Figure 5 IaE Shield Ja---- t, elliptical acti, and eta are both 1 (A,) '#E 7 Fig.6

Claims (1)

[Scope of Claims] 1) Information is recorded or recorded information is reproduced by focusing a light beam onto a track of an optical disk having spiral or concentric tracks, and In an optical information recording/reproducing device in which tracking servo control for aligning a focused position of a light beam with a track is performed by a two-stage actuator system, that is, a fine actuator system and a coarse actuator system, the servo gain of the fine actuator system is low. 1. An optical information recording and reproducing apparatus, characterized in that the servo gain of the precision actuator system can be inhibited from being reduced during a tracking servo pull-in period.