JP2000132854A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce coma aberration generated by the skew of an optical disk. SOLUTION: A liquid crystal panel 20 is made of a transparent member having a convex face and a transparent member having a planar surface. A liquid crystal panel 30 is constituted of a transparent member having a concaved face and a transparent member having a planar surface. The panels 20 and 30 are arranged in prallarel with each other with a deviation S with respect to an optical axis in a vertical direction and inserted into the path located between a light source and an optical disk which is illuminated by the light beams from the source. The voltages applied to the panels 20 and 30 are controlled in accordance with the skew of the disk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device, and more particularly, to condensing a light beam emitted from a light source at a predetermined position on an optical disk by an objective lens to record or reproduce information on a recording layer of the optical disk. The present invention relates to an optical disk device that performs the operation.

[0002]

2. Description of the Related Art In recent years, CDs (Compact Disks) and DVDs have been developed.
(Digital Versatile Disk) and the like, the recording density of optical discs is increasing.

For example, a DVD is 12 cm, which is the same as a CD.
5 Gbytes of data (about 8 times the size of a CD) can be recorded on this disc. As described above, in order to improve the recording density of the optical disk, the wavelength of the light beam irradiated on the optical disk for reading and writing data is shortened, and the numerical aperture of the objective lens for condensing the light beam on the optical disk is improved. It is necessary to increase NA (Numeric Apature).

[0004]

By the way, if the wavelength of the light beam is shortened or the numerical aperture NA is increased, the wavefront aberration (mainly coma) is increased when the optical disk has skew. Occurred, and the accuracy of reading and writing information was sometimes reduced.

Therefore, conventionally, in order to solve such a problem, for example, as shown in FIG. 17, two transparent substrates having a concave surface and a convex surface are arranged in a direction perpendicular to the optical axis. In addition, there has been proposed a method of correcting coma aberration by disposing a shift S in a direction parallel to a disk skew to be corrected and controlling the shift S as appropriate.

However, such a method requires an actuator for controlling the displacement S between the two transparent substrates, so that a mechanically operating portion is generated, and as a result, the number of failures increases and the life is shortened. There has been a problem that shortening may be caused.

On the other hand, there is a method of correcting coma aberration by enclosing liquid crystal between two transparent substrates on which a plurality of divided transparent electrodes are formed, and applying voltages of different phases to the respective transparent electrodes. Proposed.

However, since coma generated by disk skew has a spatially continuous phase distribution, coma having such characteristics cannot be completely corrected by a discrete phase distribution. there were.

The present invention has been made in view of such a point, and is characterized by providing an optical disk device capable of reliably compensating for disk skew by adding a simple device.

[0010]

According to the present invention, in order to solve the above-mentioned problems, a light beam emitted from a light source is condensed at a predetermined position on an optical disk by an objective lens, and is focused on a recording layer of the optical disk. In an optical disc device for recording or reproducing information, two transparent members having a concave or convex surface whose center is displaced by a predetermined distance between the light source and the objective lens, and contacting the concave or convex surface Compensating optical system composed of a liquid crystal provided as described above, and a transparent electrode for applying a voltage to the liquid crystal, a skew detecting unit for detecting a skew of the optical disc, and a skew detecting unit for detecting a skew of the optical disc. An optical disk device, comprising: a voltage application unit that applies a predetermined voltage to the compensation optical system according to skew. .

Here, the adaptive optics system includes two transparent members having a concave or convex surface, which are arranged with the center thereof shifted by a predetermined distance between the light source and the objective lens, and abuts on the concave or convex surface. The skew detection unit includes a liquid crystal provided and a transparent electrode for applying a voltage to the liquid crystal, and detects a skew of the optical disc. The voltage application section is
According to the skew detected by the skew detector,
A predetermined voltage is applied to the adaptive optics.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration example of an embodiment of the present invention.

In FIG. 1, an optical disc 1 is, for example, a CD or a DVD, and records information by physically changing a recording layer disposed in a disk-shaped transparent substrate.

The optical pickup unit 2 includes a light source unit 2a, a lens 2b, a beam splitter 2c, an adaptive optics 2d, an objective lens 2e, a lens 2f, a light detection unit 2g, and a temperature detection unit 2h, which will be described later. Control unit 3
In accordance with the control, a predetermined position on the optical disk 1 is irradiated with a light beam to read and write information.

Here, the light source section 2a is constituted by, for example, a laser diode or the like, and emits coherent light of a single wavelength. The lens 2b converts the light beam emitted from the light source unit 2a into a parallel light beam and enters the beam splitter 2c.

The beam splitter 2c transmits the light emitted from the lens 2b and makes it incident on the compensating optical system 2d, and reflects the light beam reflected from the optical disk 1 in a direction substantially perpendicular to the lens 2f. Let it.

The compensating optical system 2d compensates for coma caused by skew of the optical disk 1, as will be described later. The objective lens 2e focuses the light beam emitted from the adaptive optics system 2d on a predetermined area of the optical disc 1.

The lens 2f condenses the light beam reflected by the optical disk 1 and the traveling direction of which is changed by the beam splitter 2c, on the detection surface of the light detection section 2g. The light detection unit 2g is configured by, for example, a photodiode, and converts light collected by the lens 2f into a corresponding electric signal.

The temperature detecting section 2h detects the temperature of the liquid crystal (details will be described later) of the adaptive optics system 2d, and notifies the control section 3. The control unit 3 is configured by a microcomputer or the like, and controls the optical pickup unit 2 and each unit of the device.

The skew detector 4 is arranged near the objective lens 2e, detects the skew of the optical disk 1 near the light beam irradiation, and notifies the controller 3 of the skew. Next, before describing the details of the adaptive optical system 2d, coma aberration generated by skew of the optical disc 1 will be described.

The light beam applied to the optical disk 1 via the objective lens 2e passes through the substrate of the optical disk 1 and is focused on the recording layer. At this time, if there is a skew in the optical disk 1, A spatial phase distribution of the light beam, that is, a wavefront aberration occurs. The third-order coma is dominant in this wavefront aberration. This coma is converted to the objective lens 2
When represented by coordinates (x, y) normalized by the pupil radius of e, the following equation (1) is obtained.

[0022]

(Equation 1) Here, W31 is 3 normalized by the wavelength λ of the laser beam.
This is the next coma aberration coefficient, and can be expressed by the following equation (2).

[0023]

(Equation 2) Here, NA is the numerical aperture of the objective lens 2e, and n,
t is the refractive index and the thickness of the transparent substrate of the optical disc 1, respectively, and θ is the skew angle of the optical disc 1.

Therefore, the light beam before entering the optical disk 1 has a phase distribution -W (x, y) for compensating for the phase distribution W (x, y) due to coma generated by the disk substrate. By doing so, it is possible to suppress the occurrence of the above-described coma aberration and the like.

In the embodiment of the present invention, the skew angle is changed by changing the refractive index of the liquid crystal by applying a predetermined voltage to a liquid crystal panel in which the liquid crystal is sandwiched by a transparent member having a concave or convex surface shape. The light beam is provided with a predetermined phase distribution corresponding to.

First, the change in the phase distribution of the light beam when a voltage is applied to a liquid crystal panel having a transparent member having a planar shape will be described. FIG. 2 is a cross-sectional view showing a cross section of a liquid crystal panel in which the surface of the transparent member has a planar shape. As shown in this figure, the liquid crystal panel 10 includes transparent members 10a and 10b, transparent electrodes 10c and 10d, an alignment film 1
0e, 10f, and a liquid crystal 10g.

On one surface of the transparent members 10a and 10b, for example, ITO (Indium Thin Oxide) is deposited to form transparent electrodes 10c and 10d. The alignment film 10e,
10f is for specifying the molecular direction of the liquid crystal. The liquid crystal 10g is, for example, a bend-type nematic liquid crystal.

The transparent electrode 10 of such a liquid crystal panel 10
When a voltage is applied to c and 10d, a change occurs in the direction of the liquid crystal 10g, and as a result, the refractive index changes. For example, the above-mentioned bend-type nematic liquid crystal exhibits birefringence, and the refractive index (n _LC ) in the alignment direction changes according to the applied voltage. Therefore, for a linearly polarized light beam along the alignment direction, A phase of n _LC × d (d: thickness of liquid crystal) can be given.

FIG. 3 is a diagram showing the relationship between the applied voltage and the refractive index change Δn _LC . As shown in this figure, when the applied voltage rises above a predetermined threshold, the change in the refractive index starts to increase, and stops when the voltage reaches a certain constant voltage. Generally, the maximum change amount of the refractive index is about 0.15 to 0.2.

The voltage applied to the liquid crystal is an AC voltage of about several kHz, and the voltage value represents its effective value. In the present invention, by utilizing the above-described properties of the liquid crystal panel, a desired phase distribution (−W
By providing (x, y)), the occurrence of coma and the like is prevented.

FIG. 4 is a diagram showing an example of a liquid crystal panel used in the adaptive optics system 2d of the present embodiment. FIG. 4A shows a liquid crystal panel 20 in which the transparent member has a convex shape. In this liquid crystal panel 20,
The transparent member 20a has a convex shape, and other configurations are the same as those in FIG. FIG. 5 is a diagram showing a surface shape of the transparent member 20a shown in FIG. As shown in this figure, the transparent member 20a has a curved surface proportional to the fourth power of the distance from the center. Here, r is a distance from the center, and a is a proportional constant.

FIG. 4B shows a liquid crystal panel 30 in which the transparent member has a concave shape. In this liquid crystal panel 30, the transparent member 30b has a concave shape, and the other configuration is the same as that in FIG. This transparent member 30b also has a surface shape as shown in FIG. 5, as in the case of FIG.

The phase distribution given to the light beams transmitted through the liquid crystal panels 20 and 30 can be expressed by the following equations (3) and (4), respectively.

[0034]

(Equation 3)

[0035]

(Equation 4) Here, _ng is the refractive index of the transparent substrate. As can be seen from these equations, the liquid crystal panels 20 and 30 can provide a light beam with a phase distribution proportional to the fourth power of the distance in the radial direction and the difference in the refractive index between the liquid crystal and the transparent substrate. .

Here, considering the (x, y) coordinates centered on the optical axis, these two liquid crystal panels are arranged as shown in FIG.
They are juxtaposed so that each has a deviation S in the x direction from the optical axis. At this time, the phase distribution given to the light beam transmitted through each liquid crystal panel is expressed by the following equations (5) and (6).
Can be represented by

[0037]

(Equation 5)

[0038]

(Equation 6) Next, the phase distribution W12 given to the light beam transmitted through both of these two liquid crystal panels 20, 30 is represented by W1 and W1.
2 and can be represented by the following equation (7).

[0039]

(Equation 7) Here, the first term in ｛｝ on the right side is equivalent to the equation of coma aberration that occurs when the optical disc 1 is tilted in the x direction shown in equation (1), if an appropriate coefficient is selected. Since the second term is a linear function of x, the light transmitted through these two liquid crystal panels 20 and 30 is displaced in the x direction (the position of the light spot on the optical disc 1 in the x direction). Misalignment). However, since this deviation is corrected by a tracking servo or a PLL (Phase Locked Loop) circuit or the like, it does not become an obstacle when reading and writing information.

Therefore, by appropriately setting the coefficient of W12 shown in the equation (7), the optical disc 1 shown in the equation (2) can be obtained.
It is possible to correct the coma generated by the skew.

Here, the coefficients included in equation (7) are:
These are a constant a relating to the surface shape of the transparent member, a deviation S of the liquid crystal panel in the x direction, and a difference between the refractive indexes of the liquid crystal and the transparent member.
In the present embodiment, the shift S is fixed, and the refractive index n of the liquid crystal is set.
By controlling the _LC by the applied voltage, the value of W12 is appropriately changed to correct any coma.

From the equations (1) and (7), when the condition for correcting the coma caused by the skew of the optical disc 1 by these two liquid crystal panels 20 and 30 is obtained, the following equation (8) is obtained. Can be represented.

[0043]

(Equation 8) Here, r _obj is the pupil radius of the objective lens 2e, and λ
Is the wavelength of the light beam.

By controlling the voltage applied to the liquid crystal so as to satisfy the above equation (8), it is possible to correct the occurrence of coma due to the skew of the optical disc 1. Next, a method for setting and driving each coefficient of the liquid crystal panels 20 and 30 will be described.

First, as shown in FIG. 7, the refractive indexes of the transparent members of the liquid crystal panels 20 and 30 and the refractive index of the liquid crystal are set such that the refractive index of the transparent member falls within the range of change in the refractive index of the liquid crystal. . That is, n and _ng are selected so as to satisfy the relationship of n < _ng <(n + 0.2).

If there is no skew in the optical disc 1, no correction is required by the liquid crystal panels 20 and 30, and in that case, the voltage V0 that satisfies n _LC = _ng (see FIG. 7).
Is applied to the liquid crystal panels 20 and 30, respectively.

With respect to the skew, the voltage V1 (see FIG. 7) is calculated so that the difference in the refractive index between the liquid crystal and the transparent member satisfies the relationship of equation (8), and the liquid crystal panels 20, 3 are calculated.
0 is applied.

For the skew in the direction opposite to the above-described case, the voltage V2 (see FIG. 7) that also satisfies the relationship of equation (8) is calculated, and the voltage V2 is applied to the liquid crystal panels 20 and 30. To apply.

According to the above method, the optical disk 1
It is possible to correct the coma generated by the skew included in the image. Next, the liquid crystal panel 2 described above
The operation of the adaptive optical system 2d having 0 and 30 will be described. Note that the liquid crystal panels 20 and 30 are built in the adaptive optics system 2d shown in FIG. 1 and are juxtaposed so as to be shifted from each other along the skew direction of the optical disc 1. Further, the temperature detection unit 2 h
0 or liquid crystal 20 g or 3 of liquid crystal panel 30
It is assumed that a temperature of 0 g (or a temperature in the vicinity thereof) is detected.

Now, in the embodiment shown in FIG. 1, if the optical disk 1 is mounted and reproduction or recording is started, the optical disk 1 is rotated at a predetermined angular velocity by a spindle motor (not shown). At this time, the skew detection unit 4 detects a skew near the light beam of the optical disk 1 irradiated with the light beam, and notifies the control unit 3 of the skew angle.

The control unit 3 obtains the control voltage Vc corresponding to the skew angle notified from the skew detection unit 4 from a table (a table in which the skew angle and the control voltage are stored in association with each other) in a memory (not shown) or the like. Then, it is supplied to the adaptive optics 2d. At this time, the control unit 3 controls the temperature detection unit 2
The control voltage is appropriately calibrated with reference to the temperature of the liquid crystal supplied from h. Note that this calibration method is performed by referring to a table or the like that stores the temperature of the liquid crystal and the calibration value of the control voltage in association with each other.

As a result, the liquid crystal panels 20, 3 shown in FIG.
To 0, Vc is supplied, and the refractive index changes by changing the alignment direction of the liquid crystal accordingly. as a result,
The light beam transmitted through these liquid crystal panels 20 and 30 is
It has a phase distribution that satisfies Expression (8).

When a light beam having such a phase distribution is focused on the recording layer of the optical disk 1, no coma aberration occurs even when the optical disk 1 has a skew, and a stable light spot is always generated. It is formed.

This light spot is reflected in accordance with the physical state of the recording layer (for example, unevenness of the recording layer) and the like, and the objective lens 2e, the compensation optical system 2d, the beam splitter 2c,
Then, the light is incident on the light detection unit 2g via the lens 2f, and is converted into an electric signal corresponding to the information recorded on the recording layer.

As a result, even when the optical disc 1 has a skew, the occurrence of coma can be prevented, so that the information recorded on the recording layer can be accurately reproduced, and the recording layer can be accurately reproduced. It is possible to reliably record information even when information is recorded with respect to.

Next, a second embodiment of the adaptive optics 2d will be described. FIG. 8 is a diagram illustrating a configuration example of the second embodiment of the adaptive optical system 2d. In the second embodiment, two liquid crystal panels 30 having a concave shape are juxtaposed so as to have a shift S in a direction perpendicular to the optical axis.

As can be inferred from the above description, it can be said that the liquid crystal panel 20 is a liquid crystal panel 30 having negative characteristics. Therefore, by arranging two identical liquid crystal panels in parallel and individually setting the voltage applied to each liquid crystal panel, it is possible to achieve the same effect as in the case described above.

In the example shown in FIG. 8, two liquid crystal panels 30 having a concave shape are arranged side by side, but it goes without saying that a liquid crystal panel 20 having a convex shape may be used.

Next, the driving method of the above embodiment will be described. In the embodiment shown in FIG. 8, as shown in FIG. 9, when there is no skew in the optical disc 1,
A voltage V0 at which the liquid crystal and the transparent member have the same refractive index is applied to the two liquid crystal panels 30.

For the skew, the voltage V1 at which the refractive index of the liquid crystal and the transparent member satisfies the relationship shown in equation (8)
(See FIG. 9) to one of the liquid crystal panels, and a voltage V that gives a refractive index difference of the same amount and a different sign to the refractive index given by V1.
2 (see FIG. 9) may be applied to the other liquid crystal panel.

According to such an embodiment, as in the case described above, even when the optical disk 1 has a skew, it is possible to prevent the occurrence of coma aberration.
The information recorded on the optical disc 1 can be accurately reproduced, and the information can be reliably recorded on the optical disc 1.

In this embodiment, since two liquid crystal panels of the same type are used, it is possible to reduce the types of components to be used. As a result, the cost of the apparatus can be reduced. Becomes possible.

Next, referring to FIG. 10, the adaptive optical system 2d
The third embodiment will be described. FIG. 10 is a diagram illustrating a configuration example of the third embodiment of the adaptive optical system 2d. In this figure, a transparent member 40a having a convex shape and a transparent member 40b having a concave shape are juxtaposed with a shift S, and a liquid crystal 40c is sealed between them.

In this embodiment, the functions realized by two liquid crystal panels in the embodiment shown in FIG. 4 are integrated into one liquid crystal panel. Therefore, the phase distribution generated by this liquid crystal panel can be expressed by equation (7). The driving method is the same as that in the case of FIG.

According to the above-described embodiment, it is possible not only to prevent the occurrence of coma aberration as in the embodiment shown in FIG. 4, but also to reduce the number of parts as compared with the case of FIG. Therefore, the manufacturing cost of the device can be reduced.

Next, referring to FIG. 11, the compensating optical system 2d
The fourth embodiment will be described. FIG. 11 is a diagram illustrating a configuration example of the fourth embodiment of the adaptive optical system 2d. In this figure, a transparent member having a convex shape and a transparent member having a concave shape are formed as one member 50c, and transparent members 50a and 50b are arranged above and below the member, and between the transparent members. Liquid crystal 50d, 5
0e is enclosed.

In this embodiment, only one transparent member is reduced as compared with the case of FIG. 4, and the phase distribution and the driving method generated by the liquid crystal panel 50 are the same as those of FIG. The same is true.

According to the above-described embodiment, not only can the occurrence of coma be prevented as in the embodiment shown in FIG. 4, but also it is slightly smaller than that of FIG.
Since the number of parts can be reduced, the manufacturing cost of the device can be reduced.

Next, referring to FIG. 12, adaptive optics 2d
The fifth embodiment will be described. FIG. 12 is a diagram illustrating a configuration example of the fifth embodiment of the adaptive optical system 2d. In this figure, a transparent member 60a having a convex shape and a transparent member 60b having a concave shape are juxtaposed with a deviation S, a transparent member 60c is disposed therebetween, and a liquid crystal 60d, 60e is enclosed.

This embodiment is basically the same as that of FIG. 4. The phase distribution generated by liquid crystal panel 60 is the same as that of FIG. 4, and the driving method is the same as that of FIG. Conform.

According to the above-described embodiment, not only can the occurrence of coma be prevented as in the embodiment shown in FIG. 4, but also the components are slightly smaller than those in FIG. Since the number of points can be reduced, the manufacturing cost of the device can be reduced.

Next, referring to FIG. 13, adaptive optical system 2d
The sixth embodiment will be described. FIG. 13 is a diagram illustrating a configuration example of the adaptive optical system 2d according to the sixth embodiment. In this figure, a transparent member 70c having a concave shape formed with a shift S on both surfaces is disposed between the transparent members 70a and 70b, and liquid crystals 70d and 70e are sealed between the transparent members 70a and 70b. I have. The transparent member 70
c may form a convex shape instead of a concave shape.

This embodiment is basically a method in which the embodiment shown in FIG. 8 and the embodiment shown in FIG. 11 are mixed, and the driving method is the same as that in FIG. is there. According to the above-described embodiment, not only can the occurrence of coma be prevented as in the embodiment shown in FIG. 4, but also the number of components can be reduced, although slightly, as compared with the case of FIG. Therefore, the manufacturing cost of the device can be reduced.

Next, referring to FIG. 14, adaptive optics 2d
The seventh embodiment will be described. FIG. 14 is a diagram illustrating a configuration example of the seventh embodiment of the adaptive optics 2d. In this figure, transparent members 80a, 8 having a concave shape are shown.
0b are arranged so as to have a shift S, and a transparent member 80c having a planar shape on both sides is arranged between them. The liquid crystal 8 is disposed between the transparent members 80a to 80c.
0d and 80e are enclosed. The transparent member 80
a and 80b may form a convex shape instead of a concave shape.

This embodiment is basically a method in which the embodiment shown in FIG. 8 and the embodiment shown in FIG. 12 are mixed, and the driving method is the same as that in FIG. It is. According to the above-described embodiment, not only can the occurrence of coma be prevented as in the embodiment shown in FIG. 4, but also the number of components can be reduced, although slightly, as compared with the case of FIG. Therefore, the manufacturing cost of the device can be reduced.

FIG. 15 is a diagram showing a configuration example of the eighth embodiment of the adaptive optical system 2d. In this embodiment, liquid crystal panels 90 and 100 similar to those shown in FIG. 10 are juxtaposed. In the panel 90, a transparent member 90a having a convex shape and a transparent member 90b having a concave shape are juxtaposed with a shift S, and a liquid crystal 90c is sealed between them. Similarly, in the panel 100, a transparent member 100a having a convex shape and a transparent member 100b having a concave shape are juxtaposed with a shift S, and a liquid crystal 10
0c is enclosed. The shift directions of the respective liquid crystal panels are set so as to be staggered.

Although the same liquid crystal panel as that shown in FIG. 10 is used in the above example, any of the liquid crystal panels shown in the first to seventh embodiments may be selected. In this embodiment, the phase distributions given to the light beams by the liquid crystal panel 90 and the liquid crystal panel 100 have the same sign, and therefore, the phase distribution generated by the liquid crystal panel 100 is:
This is offset by the liquid crystal panel 90. Therefore, the phase distribution when no voltage is applied is “0”. By applying a voltage to one of these liquid crystal panels in accordance with the skew of the optical disc 1 while using one of the liquid crystal panels for the positive direction and the other for the negative direction,
The occurrence of coma can be prevented.

Now, let the refractive index of the liquid crystal sealed in the liquid crystal panel to which the voltage is applied be n _LC1 and the applied voltage be 0
_Assuming that the refractive index of the liquid crystal in the case of V is n _LC0 , the phase distribution of the light beam transmitted through these two liquid crystal panels can be expressed by the following equation (9).

[0079]

(Equation 9) As can be seen from this equation, since the term ( _ng ) relating to the transmittance of the transparent member has been deleted from the phase distribution of the light beam transmitted through the liquid crystal panels 90 and 100, the refractive indices of the transparent member and the liquid crystal have been deleted. Can be simplified.

FIG. 16 is a diagram showing a method of driving the liquid crystal panels 90 and 100. As shown in FIG. 15, in the embodiment shown in FIG. 15, the skew in the + direction (for example, the skew in which the surface of the optical disc 1 in FIG. The voltage Vs is applied, and the skew in the negative direction (the skew in which the surface of the optical disc 1 is inclined counterclockwise from the horizontal plane) is dealt with by applying the voltage Vs to the liquid crystal panel 100. I do. Therefore, since a voltage corresponding to the skew may be applied, the driving method can be simplified. In addition, when no skew occurs, it is not necessary to apply a voltage, so that power consumption can be reduced.

According to the above-described embodiment, it is possible not only to prevent the occurrence of coma aberration as in the embodiment shown in FIG. 4, but also to simplify the driving method and reduce the power consumption. It becomes possible. Further, since it is not necessary to set the refractive indexes of the liquid crystal panel and the transparent member, the design can be simplified.

[0082]

As described above, according to the present invention, an optical disk for condensing a light beam emitted from a light source at a predetermined position on an optical disk by an objective lens and recording or reproducing information on a recording layer of the optical disk. In the device, two transparent members having a concave or convex surface whose center is displaced by a predetermined distance between a light source and an objective lens, a liquid crystal provided so as to contact the concave or convex surface, and a liquid crystal. A compensating optical system composed of a transparent electrode for applying a voltage to the compensating optical system, a skew detecting unit for detecting a skew of the optical disc, and a predetermined skew for the compensating optical system according to the skew detected by the skew detecting unit. Since it has a voltage application unit for applying a voltage, even when the optical disc has skew, information is recorded or reproduced accurately. Theft is possible.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a general liquid crystal panel.

3 is a diagram showing a relationship between a voltage applied to the liquid crystal panel shown in FIG. 2 and a change in refractive index.

4 (A) is an example of a liquid crystal panel in which a transparent member used in the adaptive optics system shown in FIG. 1 has a convex shape, and FIG. 4 (B) also shows a transparent member having a concave shape; It is an example of a liquid crystal panel having the following.

FIG. 5 is a diagram showing a shape of a concave surface or a convex surface shown in FIG. 4;

FIG. 6 is a configuration example of a first embodiment of the adaptive optics system shown in FIG. 1;

FIG. 7 is a diagram showing a relationship between a voltage applied to the liquid crystal panel shown in FIG. 6 and a refractive index.

FIG. 8 is a configuration example of a second embodiment of the adaptive optics system shown in FIG. 1;

9 is a diagram showing a relationship between a voltage applied to the liquid crystal panel shown in FIG. 8 and a refractive index.

FIG. 10 is a configuration example of a third embodiment of the adaptive optics system shown in FIG. 1;

FIG. 11 is a configuration example of a fourth embodiment of the adaptive optics system shown in FIG. 1;

FIG. 12 is a configuration example of a fifth embodiment of the adaptive optics system shown in FIG. 1;

FIG. 13 is a configuration example of a sixth embodiment of the adaptive optics system shown in FIG. 1;

FIG. 14 is a configuration example of a seventh embodiment of the adaptive optics system shown in FIG. 1;

FIG. 15 is a configuration example of an eighth embodiment of the adaptive optics system shown in FIG. 1;

16 is a diagram illustrating a relationship between a voltage applied to the adaptive optics system illustrated in FIG. 15 and a skew.

FIG. 17 is a diagram illustrating an example of a conventional coma aberration correction method.

[Explanation of symbols]

1 ... optical disk, 2 ... optical pickup unit, 2a ...
Light source unit, 2b ... lens, 2c ... beam splitter,
2d ... Compensating optical system, 2e ... Objective lens, 2f ... Lens, 2g ... Light detection unit, 2h ... Temperature detection unit, 3 ...
Control unit, 4 skew detection unit

Continuation of the front page F term (reference) 5D118 AA11 BA01 BB01 BB07 CD04 DC16 5D119 AA22 BA01 BB01 BB04 EC04 JA09 JB03

Claims (9)

[Claims] 1. An optical disc apparatus for converging a light beam emitted from a light source to a predetermined position on an optical disc by an objective lens and recording or reproducing information on a recording layer of the optical disc, wherein the light source and the objective Two transparent members having a concave or convex surface whose center is displaced by a predetermined distance between the lenses, a liquid crystal provided to contact the concave or convex surface, and a voltage applied to the liquid crystal. A compensating optical system composed of a transparent electrode to be applied; a skew detecting unit for detecting a skew of the optical disc; and a predetermined voltage for the compensating optical system according to the skew detected by the skew detecting unit. An optical disk device, comprising: a voltage application unit that applies a voltage. 2. The optical disk device according to claim 1, wherein the concave surface or the convex surface has a curved surface proportional to the fourth power of a distance from a center. 3. An adaptive optics system comprising: a first liquid crystal panel formed by enclosing liquid crystal between a pair of transparent members, one of which is a flat surface and the other is a concave surface; A second liquid crystal panel formed by enclosing liquid crystal between a pair of transparent members, one of which is a flat surface and the other of which is a convex surface, the center of which is displaced by a predetermined distance; 2. The optical disk device according to claim 1, wherein the voltage applying unit applies the same voltage to transparent electrodes formed on respective opposing surfaces of the first and second liquid crystal panels. 4. The liquid crystal panel according to claim 3, wherein one transparent member of the first liquid crystal panel and one transparent member of the second liquid crystal panel are formed of one transparent member.
An optical disk device as described in the above. 5. The adaptive optics system comprises: a first liquid crystal panel formed by enclosing liquid crystal between a pair of transparent members each having a flat surface on one side and a concave or convex surface on the other side; A second liquid crystal panel formed by enclosing liquid crystal between a pair of transparent members, one of which is a flat surface and the other has the same shape as the first liquid crystal panel, is positioned at a predetermined distance from the center thereof. Wherein the voltage applying unit applies different voltages to the transparent electrodes formed on the respective opposing surfaces of the first and second liquid crystal panels. 2. The optical disk device according to claim 1, wherein: 6. The liquid crystal panel according to claim 5, wherein one transparent member of said first liquid crystal panel and one transparent member of said second liquid crystal panel are formed of one transparent member.
An optical disk device as described in the above. 7. The adaptive optics system is formed by disposing a pair of transparent members, one of which is a concave surface and the other is a convex surface, with its center shifted by a predetermined distance, and a liquid crystal is sealed therebetween. 2. The optical disk device according to claim 1, wherein the optical disk device is constituted by a liquid crystal panel formed. 8. The apparatus according to claim 1, further comprising a second compensating optical system, wherein the voltage applying section selectively applies a voltage to the compensating optical system and the second compensating optical system. 2. The optical disc device according to 1. 9. The liquid crystal display according to claim 1, further comprising: a temperature detecting unit for detecting the temperature of the liquid crystal or the vicinity thereof; and a calibrating unit for calibrating the voltage applied by the voltage applying unit based on the temperature detected by the temperature detecting unit. 2. The optical disk device according to claim 1, wherein: