JP2001004972A - Optical element, optical pickup and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart low electric power consumption and high responsiveness to an optical element and further correct coma aberrations by simple constitution. SOLUTION: An incident side liquid crystal panel 5a composed of a central electrode part 221, an intermediate toric electrode part 222 and an outer peripheral toric electrode part 223 is arranged by parting the same from the optical axis of a laser beam by a lateral deviation rate(s). On the other hand, an exit side liquid crystal panel 5b composed of the central electrode part 221, the intermediate toric electrode part 222 and the outer peripheral toric electrode part 223 is arranged on the side opposite to the incident side liquid crystal panel 5. Voltage is respectively impressed to the electrodes of the incident side liquid crystal panel 5a and the exit side liquid crystal panel 5b, by which phases are previously imparted to the transmitted light and the coma aberrations generated by the inclination of an optical disk are corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element disposed on an optical path of light emitted from a light source, an optical pickup for irradiating a laser beam to record and / or reproduce a signal on a signal recording medium, and a rotating device. The present invention relates to an optical disk device that records and / or reproduces a signal on a driven disk-shaped recording medium.

[0002]

2. Description of the Related Art When recording or reproducing signals on an optical disk by an optical pickup, a wavefront aberration occurs due to the optical disk being tilted with respect to the optical axis of laser light emitted from the optical pickup. In the wavefront aberration generated in this way, the third-order coma is dominant.

As shown in FIG. 15, two compensating optical elements 201 and 201 are provided on an optical path to correct coma aberration.
Means for correcting the coma aberration by disposing 02 (hereinafter, referred to as a correction plate method) have been conventionally proposed. The first compensating optical element 201 has a convex surface 201a, the second compensating optical element 202 has a concave surface 202a, and these compensating optical elements 201 and 202 face each other,
It is located in the optical path.

[0004] In the correction plate system, as shown in FIG.
And the second compensating optical elements 201 and 202 are displaced in a direction orthogonal to the optical axis and in directions opposite to each other with respect to the optical axis, and transmit the opposite phase distribution as the one corresponding to the coma aberration. This is given to the laser beam in advance and corrects the coma aberration.

[0005]

By the way, the correction plate method requires mechanical moving operation means such as an actuator for driving the first and second compensation optical elements 201 and 202. However, with mechanical movement operation means,
High responsiveness cannot be obtained, and power consumption for driving increases.

Accordingly, the present invention has been made in view of the above situation, and has low power consumption and high responsiveness.
It is still another object of the present invention to provide an optical element, an optical pickup, and an optical disk device that can correct coma with a simple configuration.

[0007]

In order to solve the above-mentioned problems, an optical element according to the present invention comprises a liquid crystal enclosing means for enclosing and holding liquid crystal and a transparent electrode spaced apart on an optical path. And first and second phase distribution generating electrode portions, and a voltage is applied to the first and second phase distribution generating electrode portions to change the alignment direction of the liquid crystal. The first phase distribution generating electrode section includes a substantially annular first annular electrode section having a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, The second phase distribution generating electrode portion has a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, and the center is located at the center of the first annular electrode portion with respect to the optical axis. Is provided with a substantially annular second annular electrode portion located on the opposite side. And the optical element is the first
And applying a voltage to each of the second phase distribution generating electrode portions to give a phase distribution to the emitted light in a direction perpendicular to the optical axis.

In the optical element having such a configuration, for example, a voltage is applied to the first and second phase distribution generating electrode portions so that the phase distribution for correcting the coma aberration generated in the optical member irradiated with the emitted light is applied. The emitted light is given in advance by liquid crystal whose orientation direction has been changed.

Further, the optical pickup according to the present invention comprises:
In order to solve the above-described problem, a first liquid crystal device includes a light source, a liquid crystal enclosing unit that encloses and holds liquid crystal, and a transparent electrode that is spaced apart on an optical path of light emitted from the light source.
And a phase distribution generating electrode means for applying a voltage to the phase distribution generating electrode parts of the first and second electrodes to change the alignment direction of the liquid crystal. And an objective lens for irradiating outgoing light transmitted through the optical element onto a signal recording medium. Also, the first
The first phase distribution generating electrode section has a substantially annular first annular electrode section having a center at a position separated from the optical axis by a predetermined distance in the direction perpendicular to the optical axis of the emitted light, and the second phase distribution The generating electrode section has a center at a position separated by a predetermined distance from the optical axis in a direction perpendicular to the optical axis of the emitted light, and the center is located opposite to the center of the first annular electrode section with respect to the optical axis. A substantially annular second annular electrode portion to be formed. Then, the optical pickup applies a voltage to each of the first and second phase distribution generating electrode portions to give a phase distribution to the emitted light in a direction perpendicular to the optical axis.

In the optical pickup having such a configuration, a voltage is applied to the first and second phase distribution generating electrode portions to correct the phase distribution for correcting the coma aberration generated in the signal recording medium irradiated with the emitted light. The emitted light is given in advance by the liquid crystal whose orientation direction has been changed.

According to another aspect of the present invention, there is provided an optical disc apparatus which includes a light source, a liquid crystal enclosing means for enclosing and holding liquid crystal, and a light source which is spaced apart on an optical path of light emitted from the light source. And a first and a second phase distribution generating electrode portion made of transparent electrodes.
An optical element having phase distribution generating electrode means for changing the alignment direction of the liquid crystal by applying a voltage to the phase distribution generating electrode section, and an objective lens for irradiating outgoing light transmitted through the optical element onto a disc-shaped signal recording medium An optical pickup means comprising: a recording and / or reproducing means for recording and / or reproducing a signal on a disc-shaped signal recording medium by the optical pickup means; and a tilt for detecting a tilt of the disc-shaped signal recording medium driven to rotate. A detection unit; and a control unit that controls a voltage applied to the first and second phase distribution generating electrode units based on a detection result of the inclination detection unit. The first phase distribution generating electrode section includes a substantially annular first annular electrode section having a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, The second phase distribution generating electrode portion has a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, and the center is located at the center of the first annular electrode portion with respect to the optical axis. Is provided with a substantially annular second annular electrode portion located on the opposite side. Then, the optical disc device applies a voltage to each of the first and second phase distribution generating electrode portions to give a phase distribution to the emitted light in a direction perpendicular to the optical axis.

The optical disk device having the above-described configuration is capable of correcting the first and second phase distributions for correcting the coma caused by tilting the signal recording medium irradiated with the emitted light.
A voltage is applied to the phase distribution generating electrode section of (1), and the liquid crystal whose orientation direction has been changed is given to the output light in advance.

In this optical disk apparatus, the control means controls the voltage applied to the first and second phase distribution generating electrodes in accordance with the tilt of the disc-shaped signal recording medium detected by the tilt detecting means, thereby obtaining coma aberration. To generate an optimal phase distribution for correcting.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. This embodiment is applied to an optical pickup that irradiates a laser beam to record a signal on an optical disk and reproduce a signal from the optical disk.

As shown in FIG. 1, an optical pickup 1
Are a semiconductor laser 2, a collimator lens 3, a beam splitter 4, a coma aberration corrector 5 including liquid crystal panels 5a and 5b, an objective lens 6, a condenser lens 7, and a photodetector 8.
It has.

The optical pickup 1 includes an optical disc 101
And is incorporated in an optical disc device for recording and / or reproducing signals to and from the optical disc. The optical disk device includes a rotation driving unit that drives the optical disk 101 to rotate. The optical pickup 1 irradiates a laser beam to the optical disk 101 that is rotated by the rotation driving unit to record and / or reproduce a signal. .

In the optical pickup 1, an incident side liquid crystal panel 5a disposed on the side on which the laser light emitted from the semiconductor laser 2 is incident, and light transmitted through the incident side liquid crystal panel 5a is incident thereon. The optical disc 101 is provided by a coma aberration correcting unit 5 including an emission-side liquid crystal panel 5b for transmitting the emitted light to the objective lens 6 for emission.
To correct the coma aberration generated on the signal recording surface of the optical disc 101 due to the inclination. First, the principle of correcting coma aberration by the coma aberration correcting means 5 will be described.

The optical disc 101 has a signal recording surface formed on a transparent substrate. When recording a signal on the optical disc 101 or reproducing a signal from the optical disc 101,
A light spot is formed on the signal recording surface through the transparent substrate. Here, the light-collecting performance of the light spot formed on the signal recording surface is degraded due to the inclination of the optical disk. This is because a spatial phase distribution, that is, a wavefront aberration is given to the laser light that has passed through the transparent substrate inclined with respect to the optical axis, and particularly, the generated wavefront aberration is dominated by tertiary coma. As a result, the condensing performance of the light spot is deteriorated as described above due to the generated coma aberration.

If this coma aberration is represented by coordinates (x, y) standardized by the pupil radius on the objective lens pupil plane, it can be represented by the following equation (1). W31 is a third-order coma aberration coefficient standardized by the laser light wavelength λ, and is represented by the following equation (2).

[0020]

(Equation 1)

[0021]

(Equation 2)

Here, NA is the numerical aperture of the objective lens, n is the refractive index of the transparent substrate of the optical disk 101, t is the thickness of the transparent substrate, and θ is the tilt (skew) angle of the optical disk. In the present invention, the coma aberration W (x, y) represented by the expression (1) is -W as a phase distribution in advance.
By giving (x, y), the coma aberration is corrected. That is, the optical pickup 1 uses -W (x,
The phase distribution of y) is generated by the above-described coma aberration correcting means 5 to correct the coma aberration.

Next, -W by the coma aberration correcting means 5
The generation of the (x, y) phase distribution will be specifically described.

As described above, the coma aberration correcting means 5
The liquid crystal panel includes two liquid crystal panels 5a and 5b. Each of the two liquid crystal panels 5a and 5b encloses and holds liquid crystal by a pair of transparent substrates, and has electrodes formed on the inner surface of each transparent substrate. . The coma aberration correcting means 5 changes the alignment direction of the liquid crystal by applying a voltage to the electrodes formed on the inner surface of the transparent substrate of each of the liquid crystal panels 5a and 5b, and the liquid crystal panel 5a, 5b Of the laser beam to be transmitted, and a phase is previously given to the transmitted laser beam at each position from the optical axis of the laser beam.

Here, for example, the coma aberration correcting means 5 satisfies the expressions (3) and (4) with respect to the distance r standardized by the pupil radius of the objective lens 6 in the radial direction from the optical axis. The phase distribution shown in a simple polar coordinate system is
Let us consider the case of generating at a and 5b.

[0026]

(Equation 3)

[0027]

(Equation 4)

Here, a and b are arbitrary constants. The phase distribution according to the equations (3) and (4) indicates a phase distribution based on the optical axis r = 0, and the phase at r = 0 is zero. 2A shows the phase distribution given by equation (3), and FIG. 2B shows the phase distribution given by equation (4). The phase distributions expressed by the equations (3) and (4) are replaced by an xy coordinate system, and the phase distributions when the optical axis is moved in the x direction by the distance s in the opposite direction are given by the equations (5) and (5). Equation 6) is obtained.

[0029]

(Equation 5)

[0030]

(Equation 6)

Each of the liquid crystal panels 5a, 5a that gives the phase distribution shown by the equations (5) and (6) to the transmitted light.
As shown in FIG. 3, b is disposed so as to be located opposite to the optical axis of the laser light emitted from the semiconductor laser 2 and is only a distance s from the optical axis (hereinafter referred to as a lateral shift amount). They are arranged separately from each other.

In such an arrangement, the emission-side liquid crystal panel 5a gives the transmitted light the phase distribution shown by the equation (5), and the incident-side liquid crystal panel 5b gives the phase distribution shown by the equation (6) to the transmitted light. Each liquid crystal panel 5
As a result, the phase distribution of the expression (7) expressed by the sum of the expressions (5) and (6) occurs in the transmitted lights a and 5b.

[0033]

(Equation 7)

Here, c is expressed by equation (8).

[0035]

(Equation 8)

Here, if an appropriate value is selected for the coefficient of the first term of the equation (7), it becomes equivalent to the equation of the coma aberration generated when the optical disk 101 is tilted in the x direction of the equation (1). The second term of the equation (7) is a linear function with respect to x, which is a tilt of the wavefront and appears as a displacement of the light spot in the disk surface. Since it can be corrected, it does not affect recording and reproduction. That is, the second term is considered negligible.

From the above, with respect to the coma aberration coefficient W31 given by the equation (2), the first value of W12 in the equation (7) is obtained.
If the coefficient of the term is determined to be a value that is -W31, a phase distribution can be generated corresponding to the coma aberration generated according to the tilt angle of the optical disc 101. For example, an optimum phase distribution is generated by fixing the lateral shift amount s and changing the constant a.

Further, it can be seen that the constant b may be an arbitrary constant for the purpose of correcting coma as described above. Therefore, from Expressions (1) and (7), note that W31 in Expression (1) is standardized by wavelength as a condition for correcting the coma aberration coefficient W31 generated due to the tilt of the optical disk. , (9) are derived.

[0039]

(Equation 9)

Here, for example, when W31 = 1 and s = 0.2, a = λ / 1.6.

As described above, the phase distribution that satisfies the expression (9) is given to the laser beam irradiated on the optical disc in advance by the liquid crystal panels 5a and 5b of the coma aberration correcting means 5, whereby the optical disc 101 can be obtained. Can be corrected for coma caused by the inclination of.

Here, each of the liquid crystal panels 5a and 5b has a phase distribution for correcting coma aberration by changing the refractive index in a direction perpendicular to the optical axis of the laser beam. The structure of the liquid crystal panels 5a and 5b will be described. Here, the incident side liquid crystal panel 5a and the exit side liquid crystal panel 5b have the same structure, and therefore, the following description will mainly be directed to the incident side liquid crystal panel 5a.

As shown in FIG. 4, the incident side liquid crystal panel 5a includes an incident side transparent substrate 11, an incident side transparent electrode 12, an incident side alignment film 13, a liquid crystal 14, an emission side alignment film 15, an emission side transparent electrode 16, The light-emitting side transparent substrate 17 is stacked in this order. That is, the incident-side liquid crystal panel 5a is formed by laminating the incident-side transparent electrode 12 and the incident-side alignment film 13 on the incident-side transparent substrate 11, and further, on the output-side transparent substrate 17, the emission-side transparent electrode 16 and the output-side alignment film. The structure is such that the liquid crystal 14 is sealed and held between the film 15 and the film 15 so that they face each other.

Here, the incident side transparent electrode 12 is formed by depositing a conductive material on the incident side transparent substrate 11.
For example, it is made of a transparent electrode such as ITO. Similarly,
The emission side transparent electrode 16 is formed of a transparent electrode such as ITO, for example, and is formed by vapor deposition. The incident side alignment film 13 and the emission side alignment film 15 are for specifying the molecular direction of the liquid crystal 14. The liquid crystal 14 is, for example, a nematic liquid crystal having a parallel alignment.

The incident side liquid crystal panel 5 configured as described above
a, the incident side transparent electrode 12 and the exit side transparent electrode 16
When a voltage is applied between the liquid crystal 14 and the liquid crystal 14, the liquid crystal 14 exhibits birefringence, and changes the refractive index (n _LC ) according to the applied voltage. As a result, when d is the thickness of the liquid crystal 14, the incident side liquid crystal panel 5a gives a phase d times n _LC to the linearly polarized light component of the transmitted light along the alignment direction of each of the alignment films 13 and 15.

The output-side liquid crystal panel 5b having the same configuration as the incident-side liquid crystal panel 5a gives a phase d times n _LC to the linearly polarized light component of the transmitted light along the alignment direction of the alignment films 13 and 15. . FIG. 5 shows a refractive index change (Δn _LC ) characteristic with respect to an applied voltage. As shown in FIG. 5, in this embodiment, the refractive index has a maximum change amount of 0.15 to 0.2. Here, the applied voltage represents an effective value (Vrms) and is, for example, a rectangular wave signal having a frequency of KHz centered on 0 V and a duty of 50%.

In order to provide the laser beam with a phase distribution in the direction perpendicular to the optical axis, it is necessary to optimally design the electrode pattern. Next, the electrode patterns of the transparent electrodes 12 and 16 of each of the liquid crystal panels 5a and 5b that generate the phase distribution satisfying the equations (3) and (4) in the transmitted light will be described.

The phase distribution is shown as a continuous distribution by the equations (3) and (4), and it is difficult to obtain a phase distribution that strictly satisfies the equations (3) and (4). Therefore, the continuous phase distributions expressed by the equations (3) and (4) are sampled at arbitrary intervals and approximated by a discrete phase distribution, so that the continuous phase distributions are expressed by the equations (3) and (4). Consider generating a phase distribution that is substantially the same as the phase distribution to be generated. For example, as an approximation of the phase distribution of equation (3), consider a discrete phase distribution as shown in FIG. For example, FIG. 6 discrete phase distribution as shown in, as shown in FIG. 7, the central electrode 21 ₁ substantially circular central to portion in the electrode pattern is formed on the outer periphery of the central electrode 21 ₁ A plurality of substantially annular electrodes 21 ₁ , 2
This is made possible by a transparent electrode (hereinafter, referred to as a concentric electrode) composed of an electrode pattern composed of ₁₂ ,..., 21 _n−1 , 21 _n .

It is not necessary that both the incident side transparent electrode 12 and the exit side transparent electrode 16 be formed as concentric electrodes shown in FIG. 7, and one of the transparent electrodes is an undivided electrode, a so-called solid electrode. It can also be configured as

[0050] Then, for the voltage applied to the transparent electrode made of the electrode pattern as shown in FIG. 7, a given phase in the corresponding portion as a reference example by fixing the voltage applied to the central electrode 21 _1, the reference The phase given through the portions corresponding to the other electrodes 21 ₂ ,..., 21 _n−1 , 21 _n is substantially the same as the phase distribution shown by the equation (3). As shown, the other electrode 2
1 _2, ..., may be applying a voltage to 21 _n-1, 21 _n.

Similarly, for the incident side liquid crystal panel 5a, the above-described concentric electrode solution is formed, and a voltage is applied so as to give the transmitted light a phase distribution corresponding to the equation (4). A phase distribution approximate to the desired phase distribution shown in the equation (4) can be given to the transmitted light.

Accordingly, as shown in FIG. 3, the centers of the electrode patterns of the concentric electrodes in the incident side liquid crystal panel 5a and the outgoing side liquid crystal panel 5b are located at a distance s in the x direction from the optical axis in the opposite direction. By arranging the incident side liquid crystal panel 5a and the exit side liquid crystal panel 5b on the optical path as described above, a phase distribution for correcting the coma aberration can be given to the transmitted light in advance.

However, the concentric circle shown in FIG.
Since the electrode pattern is subdivided, it becomes difficult to control each electrode unit.

Next, another electrode pattern capable of giving the transmitted light the phase distribution represented by the equations (3) and (4) will be described.

[0055] As shown in FIG. 8, a transparent electrode, the outer periphery is a central electrode portion 22 ₁ which is a substantially circular shape, is disposed on the outer periphery of the center electrode part 22 _1, its center at the center of the center electrode part 22 ₁ generally annular shape but which match substantially circular intermediate annular electrode portion 22 ₂ of the ring shape is, its center is aligned with the center of the central electrode portion 22 _1, and is disposed on the outer periphery of the intermediate annular electrode portion 22 ₂ and an outer peripheral annular electrode portion 22 ₃ which the. And
The center electrode part 22 ₁ and the outer annular electrode 22 ₃ electrically partially by the connection electrode portions 22 ₄ are connected.

Here, when the coefficients in the expressions (3) and (4) are b = −a × (1 + s) ² , the expressions (3) and (4) are replaced by the expressions (10) and (11). It is transformed like the expression.

[0057]

(Equation 10)

[0058]

[Equation 11]

The phase distributions given by the equations (10) and (11) show the phase distributions normalized by (1 + s) as shown in FIGS. 9A and 9B. Further, the phase distribution shown by the equations (10) and (11) is r
= 0, r = 1 + s and r = −1−s, W1 (r)
= 0, and as shown in FIGS. 10A and 10B,
It can be seen that approximation can be made with at least two phase amounts.

Then, let the pupil radius of the objective lens 6 be 1,
Considering that a transparent electrode having the electrode pattern shown in FIG. 8 (hereinafter, simply referred to as a concentric electrode) is arranged on the optical path at a distance of s from the optical axis, the coma aberration can be corrected. Since the minimum radius rmin is 1 + s, the simplified concentric electrode can also generate a phase distribution similar to the phase distribution shown by the equations (10) and (11).

The simplified concentric electrodes are formed on the incident side liquid crystal panel 5a and the exit side liquid crystal panel 5b, and the incident side liquid crystal panel 5a and the exit side liquid crystal panel 5b are arranged on the optical path as follows.

The transparent electrode of the incident side liquid crystal panel 5a is
As shown in the middle (A) and (B), the central electrode portion 22
_1, the intermediate annular electrode 22 ₂ which is located on the outer periphery of the center electrode part 22 _1, a first simplified consisting periphery an annular electrode portion 22 ₃ which are located on the outer periphery of the intermediate annular electrode portion 22 ₂ It is configured as a concentric electrode (first phase distribution generating electrode part), and the electrode pattern center of the first simplified concentric electrode, that is,
Central electrode part 22 _1, the intermediate annular electrode portion 22 _2, and the center of the outer annular electrode portion 22 ₃ are positioned separated by the horizontal shift amount s from the optical axis in a direction perpendicular to the optical axis of the laser beam Thus, the incident side liquid crystal panel 5a is arranged on the optical path.

The first simplified concentric electrode need only be formed as one of the incident-side transparent electrode 12 and the exit-side transparent electrode 16. In this case, the electrode pattern of the opposed transparent electrode is a so-called solid electrode. There may be.

[0064] On the other hand, the transparent electrode of the emission-side liquid crystal panel 5b, as shown in FIG. 11 (A) and (B), an intermediate circle between the central electrode part 22 ₁ is positioned on the outer circumference of the center electrode part 22 ₁ an annular electrode portion 22 _2, and configured as a second simplified concentric electrodes consisting of an outer peripheral annular electrode portion 22 ₃ which are located on the outer periphery of the intermediate annular electrode portion 22 ₂ (second phase distribution generating electrode unit), The center of the electrode pattern of the second simplified concentric electrode is
In the direction perpendicular to the optical axis of the laser light, it is separated from the optical axis by a lateral shift amount s, and is located opposite to the electrode pattern center of the first simple concentric electrode formed on the incident side liquid crystal panel 5a. In other words, the emission-side liquid crystal panel 5b is arranged on the optical path so that the optical axis of the laser beam is opposed to the first simplified concentric electrode by 180 ° and is separated from the optical axis of the laser beam by the amount s of lateral displacement. I do.

Note that such an electrode pattern only needs to be formed on one of the incident side transparent electrode 12 and the exit side transparent electrode 16, and in this case, the electrode pattern of the opposed transparent electrode may be a so-called solid electrode. Good.

Further, the emission-side liquid crystal panel 5b is arranged at a distance from the incident-side liquid crystal panel 5a on the optical path.

The outer diameter of the outer annular electrode portion is set to twice (1 + 2) as shown in FIG.

By applying a voltage to each of the simple concentric electrodes of the incident side liquid crystal panel 5a and the outgoing side liquid crystal panel 5b arranged as described above, (1)
The phase distributions given by Equations (0) and (11) are given, respectively. This makes it possible to correct coma aberration generated when the optical disc 101 is tilted.

[0069] The center electrode 22 ₁ and the annular electrode 22 _2, 22 ₃ of the first simplified concentric electrodes, the ideal phase distribution shown by (11) upon application of a suitable voltage And the shape is such that the rms error of
The center electrode 22 ₁ and the annular electrode 22 ₂ of the simplified concentric electrodes, 22 _3, upon application of a suitable voltage (1
Needless to say, the shape is such that the rms error from the ideal phase distribution shown by the equation (0) is minimized.

The voltage applied to each electrode section is specifically as follows. For incident side liquid crystal panel 5a is the center electrode part 22 ₁ and the outer annular electrode 22 _third reference voltage V _0, an intermediate annular electrode portion 22 ₂ V ₀ + delta
Applying a V _1. Also, the exit side liquid crystal panel 5b, and applies the V ₀ + [Delta] V ₁ to the central electrode portion 22 ₁ and the outer annular electrode 22 _third reference voltage V _0, an intermediate annular electrode portion 22 _2. Here, the voltage ΔV ₁ is an applied voltage that changes according to the skew. The reference voltage V ₀ is determined to be a predetermined voltage value, for example, 0V.

By appropriately controlling the voltage ΔV ₁ in accordance with the tilt angle of the optical disc 101, the formula (10) and the formula (11), which are optimal for correcting coma aberration generated as being different depending on the tilt angle, are used. ) Can be given to the transmitted light.

Further, by using the simplified concentric electrodes, unlike the case of using the concentric electrodes shown in FIG. 7, the effect of correcting the coma aberration is somewhat sacrificed, but the sampling of the phase distribution is made coarser. With this configuration, for example, it is possible to correct coma aberration while easily controlling the voltage applied to the electrodes. Further, as described above, the coma aberration can be corrected using only two values V ₀ and ΔV ₁ as the voltage values applied to the electrodes.

Although the effect of the coma aberration correction and the simplification of the electrode pattern (the number of divisions of the electrode) are in conflict with each other, it is necessary to keep the number of divisions at a necessary minimum while appropriately dividing the number of divisions. It can be said that by selecting the number, the coma aberration correction effect can be improved.

Since W1 (r) and W2 (r) change in proportion to a by using the simplified concentric electrodes, once the electrode pattern is determined, an appropriate applied voltage is applied. In addition, it is possible to generate a phase distribution that effectively suppresses a reduction in the light condensing performance of the light spot.

As described above, the optical pickup 1 has low power consumption and high responsiveness by the coma aberration correcting means 5.
Furthermore, coma can be corrected by an inexpensive configuration.

Next, as described above, the liquid crystal panels 5a, 5a
The case where the simplified concentric electrodes respectively formed in b are formed in one liquid crystal panel will be described.

As shown in FIGS. 12A and 12B,
The liquid crystal panel 31 is incident side transparent electrode 32, a center electrode part 23 _1, the position and the intermediate annular electrode portion 23 _2, the outer periphery of the intermediate annular electrode portion 23 ₂ which is located on the outer periphery of the center electrode part 23 ₁ consists outer peripheral annular electrodes 23 ₃ which is in the first simplified concentric electrodes (first phase distribution generating electrode unit), also,
Emitting-side transparent electrode 33, a center electrode part 24 _1, the intermediate annular electrode portion 24 ₂ which is located on the outer periphery of the center electrode part 24 _1,
From the outer annular electrode 24 ₃ which are located on the outer periphery of the intermediate annular electrode portion 24 ₂ is configured as a second simplified concentric electrode (second phase distribution generating electrode).

[0078] Then, the electrode pattern center of the incident side transparent electrode 32, i.e., the central electrode part 23 _1, the intermediate annular electrode portion 23 _2, and the center of the outer annular electrode portion 22 _3, the laser beam perpendicular to the optical axis separated by the lateral shift amount s from the optical axis direction, the electrode pattern center of the exit-side transparent electrode 33, i.e., the central electrode part 24 _1, the center of the intermediate annular electrode portion 24 _2, and the outer peripheral annular electrode portion 24 ₃ Of each of the transparent substrates 11 and 17 is separated from the optical axis of the laser beam by a lateral shift amount s in the vertical direction from the optical axis of the laser light and opposite to the electrode pattern center of the incident side transparent electrode 32. Formed on the inner surface.

In order for the liquid crystal panel 31 having such a configuration to give the transmitted light the same phase distribution as the liquid crystal panels a and 5b shown in FIG. 11 described above, specifically, the following is applied to each electrode portion. Apply voltage.

In a region where the relationship between the applied voltage and the change in the refractive index is linear, when a rectangular wave signal is applied to opposing electrode surfaces at a duty ratio of 50% opposite in phase to the effective values V ₁ and V ₂ , respectively. The fact that the voltage V ₁ + V ₂ is applied to the liquid crystal is utilized. That is, giving reversed phase are rectangular signals with each other on the incident side transparent electrode 32 and the outgoing-side transparent electrode 33, the outgoing-side transparent electrode 33, the reference voltage to the center electrode part 24 ₁ and the outer peripheral annular electrode portion 24 ₃ the V ₀ is applied, the V ₀ + [Delta] V ₂ is applied to the intermediate annular electrode portion 24 _2, also for the incident-side transparent electrode 32, the reference voltage V ₀ to the center electrode part 23 ₁ and the outer circumferential annular electrode portion 23 ₃ It was applied, applying a V ₀ - [Delta] V ₂ to the intermediate annular electrode portion 23 _2. Then, the voltage ΔV ₂ is changed according to the skew angle of the optical disk.

By forming a simple transparent electrode on one liquid crystal panel 31 in this manner, it is possible to provide a further simplified coma aberration correcting means.

As described above, the coma aberration correcting means 5 forms a simplified electrode pattern on the two liquid crystal panels 5a and 5b as shown in FIG. 11, or one liquid crystal panel as shown in FIG. A simplified electrode pattern is formed on the panel 31 to correct coma due to the tilt of the optical disk.

It should be noted that the present invention is not limited to the electrode pattern shown in FIG. For example, the electrode arranged to surround the outer periphery of the intermediate annular electrode portion, that is, the outer peripheral annular electrode is not limited to being formed in an annular shape. For example, the shape of the electrode surrounding the outer periphery of the intermediate annular electrode portion is such that the shape of the inner periphery surrounds the outer periphery of the intermediate annular electrode portion, and the shape of the outer periphery is the same as the outer peripheral shape of the transparent substrate. . That is, the shape of the electrode arranged on the outer periphery of the intermediate annular electrode portion is such that the outer periphery has a substantially square shape and a central portion has a substantially circular opening.

It is not essential to provide the center electrode portion and the outer annular electrode portion. That is, an electrode pattern may be provided in which only the intermediate annular electrode portion is provided without providing an electrode in a region corresponding to the region where the central electrode portion and the outer peripheral annular electrode portion are formed.

Further, a central electrode portion, an intermediate annular electrode portion,
The center of the outer annular electrode portion may not be coincident with the center. That is, the centers of the central electrode portion, the intermediate annular electrode portion, and the outer annular electrode portion may be eccentric.

Further, the coma aberration correcting means 5 may be provided with another function. For example, as another function, a function of reducing crosstalk when using an optical disc having a recording surface composed of lands and grooves can be provided in the coma aberration correcting means 5.

As a function of reducing crosstalk,
For example, a technique relating to a phase compensation function disclosed in Japanese Patent Application Laid-Open No. 10-69678 can be adopted. Here, the technology disclosed in Japanese Patent Application Laid-Open No. 10-69678 will be briefly described. When a signal recorded on a land is reproduced, an optical phase difference of 45 ° (π / 4 rad) and a groove are generated. When reproducing the recorded signal, it is necessary to use −45 ° (−π
/ 4 rad) by changing the optical phase difference according to the time of reproduction of the land and the groove so as to give an optical phase difference to the reproduction light, thereby reducing crosstalk and consequently reducing the recording density in the track direction. It is to raise it.

The liquid crystal panel of the coma aberration correcting means 5 has a phase compensation function for giving such an optical phase difference.
Specifically, the phase compensation function can be realized by one undivided electrode in the liquid crystal panel (hereinafter, referred to as a phase compensation electrode).

FIG. 13 shows the relationship between the voltage applied to the phase compensation electrode and the phase difference. As shown in FIG. 13, the voltage applied to the phase compensation electrode is a voltage V _L giving a phase difference of π / 4 + nπ when reproducing a land, with a phase difference nπ (n is an integer) as a center value. It applied to, at the time of reproduction of the groove applying a voltage V _G so as to provide a phase difference of -π / 4 + nπ.

FIG. 8 shows an example of such a phase compensation electrode.
When applied to the incident-side transparent electrode 32 and the exit-side transparent electrode 33 of the liquid crystal panel 31 shown in (1), a voltage is applied to each electrode as follows.

At the time of reproducing the land, rectangular wave signals having mutually opposite phases are applied between the incident side transparent electrode 32 and the exit side transparent electrode 33 in a region where the relationship between the applied voltage and the change in the phase difference is linear. For the side transparent electrode 33, the central electrode portion 2
4 ₁ and the voltage of V _L / 2 is applied to the outer peripheral annular electrode portion 24 _3, a voltage of V _L / 2 + [Delta] V ₃ to the intermediate annular electrode portion 24 _2. Further, the incident-side transparent electrode 32, a voltage of V _L / 2 is applied to the center electrode part 23 ₁ and the outer circumferential annular electrode portion _{23 3, V L / 2-} ΔV 3 to the intermediate annular electrode portion 23 ₂
Is applied. Then, ΔV ₃ is changed according to the tilt of the optical disk. Thereby, the liquid crystal panel 31
When the optical disc is tilted, ΔV ₃ is appropriately selected, so that the coma due to the tilt of the optical disc can be corrected while the phase is compensated. Function.

When the optical disc is tilted during reproduction of both lands and grooves, ΔV ₃
Although a phase compensation error occurs in the liquid crystal portion corresponding to the intermediate annular electrode portion to which the above voltage is applied, the influence on recording and reproduction is small.

The optical pickup includes a disc tilt detecting means for controlling the driving of the liquid crystal panel according to the tilt angle of the optical disc. FIG. 14 shows a configuration example of an optical pickup 41 having a function of detecting the degree of inclination of the optical disc 101. An optical pickup 41 shown in FIG. 14 has the same components as the optical pickup 1 shown in FIG. 1 described above, that is, a semiconductor laser 2, a collimator lens 3, a beam splitter 4, a coma aberration corrector 5, and an objective lens 6. , A condenser lens 7, and a photodetector 8. Here, the coma aberration correcting means 5 is composed of two liquid crystal panels 5a and 5 as described above.
b, or a single liquid crystal panel 31.

The optical pickup 41 controls the driving state of the liquid crystal panel 5 in accordance with the tilt of the optical disk 101. The optical pickup 41 detects the disk tilt detecting sensor 42 and the coma aberration correcting means 5 based on the detection results of the disk tilt detecting sensor 42. And a microcomputer 41 for controlling the driving of the liquid crystal panel. Thus, the inclination of the optical disk 101 is detected by the disk inclination detection sensor 42, and the microcomputer 43 can control the voltage applied to the electrodes of the liquid crystal panel of the coma aberration correcting means 5 according to the detection result. Thereby, the optical disk 10
The liquid crystal panel of the coma aberration correcting means 5 can be controlled so that the coma aberration correcting function is maximized according to the inclination of 1.

By storing the temperature information in a microcomputer for compensating the temperature characteristics of the liquid crystal in advance, it becomes possible to drive the liquid crystal panel in consideration of the temperature of the operating environment.

[0096]

The optical element according to the present invention comprises a liquid crystal enclosing means for enclosing and holding liquid crystal, and first and second phase distribution generating electrode portions made of transparent electrodes spaced apart on the optical path. Phase distribution generating electrode means for applying a voltage to the first and second phase distribution generating electrode portions to change the orientation direction of the liquid crystal. Further, the first phase distribution generating electrode portion has a substantially annular first shape having a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light.
The second phase distribution generating electrode section comprises:
A substantially circular circle having a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, and having the center opposite to the center of the first annular electrode portion with respect to the optical axis. An annular second annular electrode portion is provided. Then, the optical element applies a voltage to each of the first and second phase distribution generating electrode portions to give a phase distribution to the emitted light in a direction perpendicular to the optical axis.

By having such a configuration, the optical element applies, for example, a phase distribution for correcting coma aberration generated in the optical member irradiated with the outgoing light to the first and second phase distribution generating electrode portions with a voltage. Can be given to the emitted light in advance by the liquid crystal whose orientation direction has been changed by the application of.

Therefore, the optical element can correct coma aberration with, for example, low power consumption, high responsiveness, and an inexpensive configuration.

The optical pickup according to the present invention is
A light source, liquid crystal sealing means for sealing and holding the liquid crystal, and first and second phase distribution generating electrode portions including transparent electrodes spaced apart on the optical path of light emitted from the light source, and An optical element including phase distribution generating electrode means for applying a voltage to the phase distribution generating electrode portions of the first and second electrodes to change the alignment direction of the liquid crystal; and outputting the light transmitted through the optical element to a signal recording medium. And an objective lens for irradiating on the top. The first phase distribution generating electrode section includes a substantially annular first annular electrode section having a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, The second phase distribution generating electrode section has a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, and the center is the center of the first annular electrode section with respect to the optical axis. A substantially annular second annular electrode portion is provided opposite to the center. Then, the optical pickup applies a voltage to each of the first and second phase distribution generating electrode portions to give a phase distribution to the emitted light in a direction perpendicular to the optical axis.

With such a configuration, the optical pickup applies a phase distribution for correcting coma aberration generated in the signal recording medium irradiated with the outgoing light to the first and second phase distribution generating electrode portions by applying a voltage to the first and second phase distribution generating electrode portions. Is applied to the emitted light in advance by the liquid crystal in which the alignment direction is changed.

Therefore, the optical pickup can correct coma aberration with, for example, low power consumption, high responsiveness, and a low-cost configuration.

Further, in order to solve the above-mentioned problems, the optical disk device according to the present invention has a light source, a liquid crystal enclosing means for enclosing and holding liquid crystal, and a light source and a liquid crystal enclosing means which are spaced apart on an optical path of light emitted from the light source. And a first and a second phase distribution generating electrode portion made of transparent electrodes.
An optical element having phase distribution generating electrode means for changing the alignment direction of the liquid crystal by applying a voltage to the phase distribution generating electrode section, and an objective lens for irradiating outgoing light transmitted through the optical element onto a disc-shaped signal recording medium An optical pickup means comprising: a recording and / or reproducing means for recording and / or reproducing a signal on a disc-shaped signal recording medium by the optical pickup means; and a tilt for detecting a tilt of the disc-shaped signal recording medium driven to rotate. A detection unit; and a control unit that controls a voltage applied to the first and second phase distribution generating electrode units based on a detection result of the inclination detection unit. The first phase distribution generating electrode portion includes a substantially annular first annular electrode portion having a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, The second phase distribution generating electrode portion has a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, and the center is the center of the first annular electrode portion with respect to the optical axis. And a substantially annular second annular electrode portion located opposite to the second annular electrode portion. Then, the optical disk device applies a voltage to each of the first and second phase distribution generating electrode portions to give a phase distribution to the emitted light in a direction perpendicular to the optical axis.

With such a configuration, the optical disc device can change the phase distribution for correcting the coma aberration generated when the signal recording medium irradiated with the emitted light is tilted by the first and second phase distribution generating electrodes. The outgoing light can be given in advance by the liquid crystal whose orientation is changed by applying a voltage to the portion.

Further, in this optical disc apparatus, the voltage applied to the first and second phase distribution generating electrode sections is controlled by the control means in accordance with the tilt of the disc-shaped signal recording medium detected by the tilt detection means, and the coma aberration is controlled. Can be generated.

Therefore, the optical pickup 1 is, for example,
Coma can be corrected with low power consumption, high responsiveness, and an inexpensive configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical pickup according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a phase distribution used for explaining a phase portion for correcting coma aberration.

FIG. 3 is a front view showing two liquid crystal panels constituting coma aberration correcting means provided in the optical pickup described above.

FIG. 4 is a front view showing a configuration of a liquid crystal panel constituting the above-described coma aberration correcting means.

FIG. 5 is a characteristic diagram showing a relationship between an applied voltage and a change in a refractive index in the above-described liquid crystal panel.

FIG. 6 is a characteristic diagram of a phase distribution which is a phase distribution for correcting coma aberration and is discretized.

FIG. 7 is a plan view showing an electrode pattern of a transparent electrode capable of generating the above-mentioned discrete phase distribution.

FIG. 8 is a plan view showing a transparent electrode including a central electrode portion, an intermediate annular electrode portion, and an outer annular electrode portion.

FIG. 9 is a characteristic diagram of a phase distribution used for explaining a phase portion for correcting coma aberration, when the phase distribution is shifted by a distance s from the optical axis.

FIG. 10 is a characteristic diagram of the phase distribution used to explain that the above-described phase distribution of FIG. 9 can be approximated by binary values.

11A and 11B are a plan view and a front view, respectively, showing a coma aberration correcting unit in which the liquid crystal patterns of FIG. 8 are formed on two liquid crystal panels.

12A and 12B are a plan view and a front view, respectively, showing a coma aberration correcting unit in which the liquid crystal pattern of FIG. 8 is formed on one liquid crystal panel.

FIG. 13 is a characteristic diagram showing a relationship between an applied voltage and a phase difference used for explaining that the coma aberration correcting means also has a phase compensation function.

FIG. 14 is a block diagram illustrating a configuration of an optical pickup including a disk tilt detecting unit and a microcomputer that controls driving of a coma aberration correcting unit in accordance with a detection result of the optical disk tilt detected by the disk tilt detecting unit.

FIG. 15 is a front view showing a conventional means for correcting phase coma aberration constituted by a pair of compensating optical elements.

[Description of Signs] 1 Optical pickup, 5 coma aberration correction means, 5a,
5b the liquid crystal panel, 22 ₁ center electrode part, 22 _second intermediate annular electrode portion, 22 ₃ periphery an annular electrode portion

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yasuyuki Takeshita F-term (reference) 2H088 EA47 GA02 MA10 5D118 AA08 AA13 BA01 BB02 BF02 BF03 CD04 DC16 5D119 within Sony Corporation 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo AA03 AA10 AA24 AA37 BA01 DA01 EC04 EC13 JA30 JA31

Claims (18)

[Claims] 1. An optical element arranged on an optical path of light emitted from a light source, comprising: a liquid crystal enclosing means for enclosing and holding a liquid crystal; and a transparent electrode spaced apart on the optical path. A phase distribution generating electrode unit having first and second phase distribution generating electrode units, wherein a voltage is applied to the first and second phase distribution generating electrode units to change the alignment direction of the liquid crystal; The first phase distribution generating electrode unit includes a substantially annular first annular electrode unit having a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, The second phase distribution generating electrode portion has a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, and the center is the first annular electrode portion with respect to the optical axis. Substantially annular second torus positioned opposite the center of the Comprising a pole unit, by applying the first and second respective voltages to the phase distribution generating electrode unit, wherein the optical element to provide a phase distribution in the vertical direction from the optical axis with respect to the emitted light. 2. The first phase distribution generating electrode section is located on the inner periphery of the first annular electrode section at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light. An outer periphery having a center is provided with a first circular electrode portion having a substantially circular shape, and the second phase distribution generating electrode portion is spaced apart from the optical axis by a predetermined distance on an inner periphery of the second annular electrode portion. A second circular electrode portion having a center at the position defined and having a substantially circular outer periphery, the center of which is located opposite to the center of the first circular electrode portion with respect to the optical axis. Outside the first and second annular electrode portions, the first
2. The optical element according to claim 1, wherein an outer peripheral electrode having a shape surrounding the outer periphery of the second annular electrode portion is provided. 3. The optical element according to claim 2, wherein the outer peripheral electrode is at least one substantially annular electrode. 4. The optical element according to claim 2, wherein a center of said circular electrode portion, a center of said annular electrode portion, and a center of said outer peripheral electrode coincide with each other. 5. The liquid crystal enclosing means includes a liquid crystal sealed between a pair of transparent substrates facing each other, and includes a first and a second liquid crystal enclosing bodies which are spaced apart from each other on the optical path. Wherein the first phase distribution generating electrode section is provided in the first liquid crystal enclosure, and the second phase distribution generating electrode section is provided in the second liquid crystal enclosure. The optical element according to claim 1, wherein: 6. The liquid crystal enclosing means encloses the liquid crystal between a first transparent substrate and a second transparent substrate facing each other, and the first phase distribution generating electrode section comprises: 2. The optical element according to claim 1, wherein the optical element is provided on an inner surface of the first transparent substrate, and the second phase distribution generating electrode portion is provided on an inner surface of the second transparent substrate. 3. 7. A first and second phase distribution generating electrode comprising a light source, liquid crystal sealing means for sealing and holding liquid crystal, and transparent electrodes spaced apart on an optical path of light emitted from the light source. Part
A voltage is applied to the first and second phase distribution generating electrode portions to change the alignment direction of the liquid crystal. An optical element including: a phase distribution generating electrode means; and the emitted light transmitted through the optical element is signaled. An objective lens for irradiating the recording medium with the objective lens, wherein the first phase distribution generating electrode portion has a substantially annular shape having a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light. The second phase distribution generating electrode section has a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, and the center Comprises a substantially annular second annular electrode portion which is located opposite to the center of the first annular electrode portion with respect to the optical axis, and wherein the first and second phase distribution generating electrode portions respectively By applying a voltage, the optical axis An optical pickup characterized by providing a phase distribution in a direction perpendicular to the optical pickup. 8. The first phase distribution generating electrode section is located on the inner periphery of the first annular electrode section at a position separated by a predetermined distance from the optical axis in a direction perpendicular to the optical axis of the emitted light. An outer periphery having a center is provided with a first circular electrode portion having a substantially circular shape, and the second phase distribution generating electrode portion is spaced apart from the optical axis by a predetermined distance on an inner periphery of the second annular electrode portion. A second circular electrode portion having a center at the position defined and having a substantially circular outer periphery, the center of which is located opposite to the center of the first circular electrode portion with respect to the optical axis. Outside the first and second annular electrode portions, the first
8. The optical pickup according to claim 7, further comprising an outer peripheral electrode having a shape surrounding the outer periphery of the second annular electrode portion. 9. An optical pickup according to claim 8, wherein said outer peripheral electrode is at least one substantially annular electrode. 10. The optical pickup according to claim 8, wherein the center of the circular electrode portion, the center of the annular electrode portion, and the center of the outer peripheral electrode coincide with each other. 11. The liquid crystal sealing means includes liquid crystal sealed between a pair of transparent substrates facing each other, and includes a first liquid crystal sealing body and a second liquid crystal sealing body which are separated from each other on the optical path. Wherein the first phase distribution generating electrode section is provided in the first liquid crystal enclosure, and the second phase distribution generating electrode section is provided in the second liquid crystal enclosure. The optical pickup according to claim 7, wherein: 12. The liquid crystal enclosing means includes:
The liquid crystal is sealed between the transparent substrate and the second transparent substrate. The first phase distribution generating electrode portion is provided on an inner surface of the first transparent substrate, and the second phase distribution generating electrode portion is provided on the inner surface of the first transparent substrate. The optical pickup according to claim 7, wherein the distribution generating electrode portion is provided on an inner surface of the second transparent substrate. 13. A rotation driving means for driving a disk-shaped signal recording medium to rotate, a light source, a liquid crystal enclosing means for enclosing and holding liquid crystal, and a light-emitting element. Phase distribution generating electrode means having first and second phase distribution generating electrode portions made of a transparent electrode, wherein a voltage is applied to these first and second phase distribution generating electrode portions to change the orientation direction of the liquid crystal. An optical element comprising: an optical element comprising: an optical element; and an objective lens for irradiating the emitted light transmitted through the optical element onto the disk-shaped signal recording medium; and a signal for the disk-shaped signal recording medium by the optical pickup means. Recording and / or reproducing and / or reproducing
A reproducing means; a tilt detecting means for detecting a tilt of the disk-shaped signal recording medium which is driven to rotate; and a voltage applied to the first and second phase distribution generating electrode portions based on a detection result of the tilt detecting means. Control means for controlling a voltage, wherein the first phase distribution generating electrode portion has a substantially annular shape having a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light. The second phase distribution generating electrode portion has a center at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light, and the center is the center of the second phase distribution generating electrode portion. A substantially annular second annular electrode portion which is positioned opposite to the center of the first annular electrode portion with respect to the optical axis; and a voltage is applied to the first and second phase distribution generating electrode portions, respectively. By applying, perpendicular to the optical axis with respect to the emitted light Optical disc apparatus characterized by giving a phase distribution in countercurrent. 14. The first phase distribution generating electrode section is located on the inner periphery of the first annular electrode section at a position separated from the optical axis by a predetermined distance in a direction perpendicular to the optical axis of the emitted light. An outer periphery having a center is provided with a first circular electrode portion having a substantially circular shape, and the second phase distribution generating electrode portion is spaced apart from the optical axis by a predetermined distance on an inner periphery of the second annular electrode portion. A second circular electrode portion having a center at the position defined and having a substantially circular outer periphery, the center of which is located opposite to the center of the first circular electrode portion with respect to the optical axis. Outside the first and second annular electrode portions, the first
14. The optical disk device according to claim 13, further comprising an outer peripheral electrode having a shape surrounding the outer periphery of the second annular electrode portion. 15. The optical disk device according to claim 14, wherein the outer peripheral electrode is at least one substantially annular electrode. 16. The optical disk device according to claim 14, wherein a center of said circular electrode portion, a center of said annular electrode portion, and a center of said outer peripheral electrode coincide with each other. 17. The liquid crystal enclosing means, wherein liquid crystal is encapsulated between a pair of transparent substrates each facing each other, and the first and second liquid crystal enclosures which are arranged separately on the optical path. Wherein the first phase distribution generating electrode section is provided in the first liquid crystal enclosure, and the second phase distribution generating electrode section is provided in the second liquid crystal enclosure. 14. The optical disk device according to claim 13, wherein: 18. The liquid crystal sealing means includes a first liquid crystal facing means.
The liquid crystal is sealed between the transparent substrate and the second transparent substrate. The first phase distribution generating electrode portion is provided on an inner surface of the first transparent substrate, and the second phase distribution generating electrode portion is provided on the inner surface of the first transparent substrate. 14. The optical disk device according to claim 13, wherein the distribution generating electrode portion is provided on an inner surface of the second transparent substrate.