JPS62170030A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent a fault of servo pull-in by changing the servo gain of an accurate actuator system depending on temperature to inhibit the operation of a servo gain change means at the pull-in of a tracking servo. CONSTITUTION:A tracking error signal TES outputted from a signal generating circuit 10 is fed to a coarse actuator 1 via a phase compensation circuit 3 and fed to an actuator 2 via a phase compensation circuit 4 and a temperature compensation circuit 5. The compensation circuit 5 changes the servo gain of the accurate actuator system depending on the temperature. A control circuit 11 controls each switch SW to be opened at the servo pull-in thereby inhibiting the operations to be acted as the compensation circuit 5.

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 device using an optical disk having a trunk formed in a spiral or concentric shape, a light beam is focused onto a track by an optical pink amplifier optical system to record information on the trunk. , or methods for reproducing recorded information are known.

In such a recording/reproducing method, focusing servo control to correctly focus the light beam on the track,
Tracking servo control is performed to align the focus position of the light cloud with the track, and here we will refer to the latter.

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

FIG. 6 shows a schematic configuration of a tracking servo group using conventional parallel control. A photodetector d detects the deviation between the light beam a and the track C on the optical disk b,
A tracking error signal (TES) is generated by a tracking error signal generating circuit e. Tracking error signal (
TBS) is applied via each phase compensation circuit to fine actuator j and coarse actuator g in their respective servo loops via i. Generally, the gain curves of both are determined as shown in FIG. 7 so that the low frequency large displacement component of the tracking error is followed by the coarse actuator g, and the high frequency small displacement component is followed by the fine actuator j.

(Problem to be Solved by the Invention) By the way, the rough actuator g also serves as a so-called access mechanism for finding the desired trunk, and a near motor is generally used, but a linear motor is a rolling type using a hair ring or a rubbing type. Since it is a system with mating parts, it naturally has a finite mechanical resolution.

If this mechanical resolution is x+ and the frequency component with the target track displacement is X2, then the gain that can be imposed on the coarse actuator system at this frequency is limited to a maximum of X, /X. If this mechanical resolution X1 is not sufficiently fine, as shown in FIG. 8, the expected servo gain will not be obtained. In particular, at the rotational frequency of the optical disk b, most of the frequency components of the track displacement are concentrated, so this effect is significant.

Even if this resolution is sufficiently fine at some point, the resonance D'' of the fine actuator j.

When characteristics such as wave number fl change due to temperature etc.,
A similar phenomenon is observed as shown in FIG.

Therefore, when trying to obtain the expected servo gain even in the above-mentioned case, problems such as a narrowing of the tolerance range for characteristic fluctuations of the fine actuator j occur.

(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 An optical information recording and reproducing apparatus for reproducing recorded information, the servo control means performing servo control in the tracking direction by a two-stage actuator system, a fine actuator system and a coarse actuator system, The apparatus includes a servo gain changing means for changing the servo gain of the precision actuator system, and a prohibiting means for prohibiting the operation of the servo gain changing means when the tracking servo is pulled in.

(Function) The servo control means performs servo control in the tracking direction using a two-stage actuator system. At this time, the servo gain of the product actuator system is changed depending on the temperature by the servo gain changing means to compensate for characteristic fluctuations of the fine actuator system. Further, when the tracking servo is pulled in, the inhibiting means inhibits the operation of the servo gain changing means, thereby preventing trouble in the servo pulling due to phenomena such as undulation of the tracking error signal with low frequency components.

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

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

In the figure, 1 is a coarse actuator, 2 is a fine actuator, 3.4 is a phase compensation circuit, 5 is a temperature compensation circuit, and 6
7 is a photodetector, 7 is an optical disk, 8 is a track, 9 is a light beam, 10 is a tracking error signal generation circuit, and 11 is a control circuit.

The tracking error signal (TBS) output from the tracking error signal generation circuit 10 is applied to the coarse actuator 1 via the phase compensation circuit 3, and is also applied to the fine actuator 2 via the phase compensation circuit 4 and temperature compensation circuit 5. It will be done. The temperature compensation circuit 5 changes the servo gain of the precision actuator system depending on the temperature.

The frequency characteristics of this temperature compensation circuit 5 and an example of a specific circuit are shown in FIGS. 3(a) and (bl), and the relationship between the resonance frequency and gain of the precision actuator 2 is shown in FIG.
In the figure, the resonance frequency f1 of the precision actuator 2 is low at high temperatures and increases at low temperatures, so
The characteristics of the temperature compensation circuit 5 are adjusted to match this change [see FIG. 3(a)].

In the circuit example shown in FIG. 3(b), the purpose is achieved using a positive temperature coefficient thermistor PTh.

FIG. 2(a) shows the servo gain curve of the tracking servo system by the optical information recording/reproducing apparatus of the present invention.

(Al shows the case where the resonant frequency f1 of the precision actuator 2 fluctuates to fa' depending on the temperature, but the desired value of the servo gain is obtained.

Since the upper limit permissible value of the resonant frequency of the precision actuator 2 without temperature compensation is f1', the permissible range of characteristic fluctuations is expanded.

In addition, in FIG. 2(b), the mechanical resolution XI' of the coarse actuator 1 is coarse, and the gain share XI' of the coarse actuator 1 is coarse.
2/ It will also be a good thing.

As described above, according to the present invention, a desired servo gain can be obtained even with respect to characteristic fluctuations of the fine actuator 2 or roughness of the mechanical resolution of the coarse actuator 1.

In other words, the permissible range of performance for each actuator to obtain the same servo gain is expanded.

Note that since the temperature compensation circuit 5 has phase delay characteristics, phenomena such as the tracking error signal (TBS) waving with low frequency components occur when the tracking servo is pulled in, as shown in FIG. It can become difficult. For this reason, as shown in FIG. 1, a control circuit 11 is provided to inhibit the operation of the temperature compensation circuit 5 during servo pull-in. Specifically, taking the circuit shown in FIG. 3 (bl) as an example, if each resistor and capacitor have the relationship shown in (■) below, each switch SW will be in an open state under the control of the control circuit 11. By doing so, the operation as the temperature compensation circuit 5 can be prohibited.

Note that the present invention is applicable not only to information recording and reproducing devices but also to devices that simply reproduce information.

(Effects of the Invention) As explained above, according to the present invention, a desired servo gain can be obtained even with respect to characteristic fluctuations of a fine actuator or roughness of mechanical resolution of a coarse actuator. That is, it is possible to expand the permissible range of performance for each actuator to obtain the same servo gain.

[Brief explanation of drawings]

1 to 4 show an embodiment of the optical information recording/reproducing apparatus of the present invention, FIG. 1 is a schematic configuration diagram showing an example of a tracking servo system, and FIG. 2(a). (bl is a diagram showing the servo gain curve, Figure 3 (al is a diagram showing the frequency characteristics of the temperature compensation circuit, Figure 3 (bl is a specific circuit diagram of the temperature compensation circuit, Figure 4 is a diagram showing the temperature of the precision actuator) Figure 5 is a curve diagram to explain characteristic fluctuations. Figure 5 is a diagram to explain that servo pull-in is somewhat difficult due to wavy tracking error signals due to a circuit with phase lag characteristics. Figure 6 is a diagram to explain that servo pull-in is somewhat difficult due to a circuit with phase delay characteristics. 7 to 9 are diagrams showing servo gain curves in a conventional parallel control system. ■... Coarse actuator 2... Precision actuator 3.4... Phase compensation circuit 5... Temperature compensation circuit 6.
... Photodetector 7 ... Optical disk 8 ... Track 9 ... Light beam 10 ... Tracking error signal generation circuit 11 ... Control circuit π7 Figure θ 〓A( Criminature 2A(LLl de Souf turn leg j city skin collection Fig. 3(a゛・ ”liquid collection □ wealth 3 medicine 1., Phi 4G ES

Claims (1)

[Claims] 1) Optical information recording and reproducing that records information or reproduces recorded information by focusing a light beam onto a track of an optical disk having spiral or concentric tracks. A device comprising: servo control means for performing servo control in the tracking direction by a two-stage actuator system including a fine actuator system and a coarse actuator system; and servo gain changing means for changing the servo gain of the fine actuator system based on temperature changes. and inhibiting means for inhibiting the operation of the servo gain changing means when the tracking servo is pulled in.