JP2001307365A - Optical head device and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical head device equipped with a converging device which secures a full optical strength at the time of recording and which forms an optical beam having a small beam spot diameter at the time of reproduction, and also to provide an optical disk device. SOLUTION: The optical head is equipped with a converging device 10 that makes the laser beam enter and that makes it exit with the spot diameter deformed, and equipped with a power supply device 28 that provides a power source for the converging device. The optical head characteristically changes the spot diameter of the laser beam, which is made incident on the converging device 10, by turning on or off the power supply device 28, forming a laser beam spot diameter smaller at the time of reproduction than at the time of recording.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device used for, for example, an optical filing device or a music CD device, and more particularly, to an improved light collecting device for converting a light beam into a focused light. , An optical head, and an optical disk device.

[0002]

2. Description of the Related Art In an optical disk device such as an optical filing device or a music CD device, many methods for reducing the beam spot diameter of a focused light beam applied to a recording surface of an optical disk have been proposed.

For example, in a method called super-resolution, a method of shielding a central portion of a region through which a light beam can pass through an opening, that is, a lens or the like (M. Born and E. Wolf: Princip
lesof Optics = Principles of Optics, Pergamon Press Ltd. Oxf
ord, 1975) and split the light beam into two concentric circles,
A method of shifting the phase of a light beam passing through each region by 180 ° (JEwilkins, Jr .: J. Oct. Soc. Am.,
40 [1950] 22).

However, when the above-mentioned method called super-resolution is used, as the beam spot diameter of the focused light beam becomes smaller, the peak intensity of the center beam spot, that is, the intensity of the light emitted from the light source becomes smaller. It is known that the light use efficiency, which is the ratio of the light spot center intensity, is significantly reduced.

[0005]

When the peak intensity decreases, for example, there is a problem that a recording error easily occurs due to a shortage of light when writing information to an optical disk. There is also a problem that a tracking error or a focusing error is likely to occur when reading information from an optical disc.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical head and an optical disk apparatus having a light condensing device capable of forming a light beam having a small beam spot diameter during reproduction while securing sufficient light intensity during recording.

[0007]

According to another aspect of the present invention, there is provided an optical head device for irradiating a laser beam emitted from a laser beam to an optical disk through an objective lens. A light-condensing device that injects a beam and deforms and emits the spot diameter of the laser beam, and a power supply device that supplies power to the light-condensing device, by turning on or off the power supply device, The spot diameter of the laser beam incident on the light condensing device is deformed so that the spot diameter of the laser beam at the time of reproduction is smaller than that at the time of recording.

According to another aspect of the present invention, there is provided an optical disk device including an optical head device for irradiating a laser beam emitted from a laser to an optical disk via an objective lens, and recording information on the optical disk. Alternatively, in an optical disk device that performs reproduction, the optical head device causes the laser beam to enter, deforms a spot diameter of the laser beam to emit the laser beam, and a power supply device that supplies power to the light focusing device By turning on or off the power supply device, the spot diameter of the laser beam incident on the condensing device is changed, and the spot diameter of the laser beam at the time of reproduction is smaller than that at the time of recording. It is characterized by being formed in a diameter.

[0009]

FIG. 1 shows a light-collecting device according to an embodiment of the present invention.

The light-collecting device 10 is formed of a first support plate 12 made of a transparent material, and is formed of a transparent material like the first support plate 12, and is arranged to face the support plate 12. It includes a second support plate 14 and an outer wall 10 a that maintains a constant distance between the first and second support plates 12 and 14 and provides a housing as the light-collecting device 10.

Inside the first and second support plates 12 and 14,
A first transparent electrode (electrode means) 16 formed in an area approximately equal to the first support plate 12, and at least a part thereof is opposed to the first support plate 12, and the first transparent electrode 16 A second transparent electrode (transparent electrode means) 18 having a desired area ratio to the area is provided. The second transparent electrode 18
Is defined to be substantially circular in this embodiment.

Inside the first and second support plates 12 and 14 and further inside the first and second transparent electrodes 16 and 18,
A liquid crystal member (optical means) 20 having at least two crystal regions, i.e., first and second liquid crystal regions 24 and 26, which are divided through the separation wall 22 and formed so that crystal characteristics can be changed independently of each other, is formed. Have been. Since the separation wall 22 is formed in an annular shape defined so as to be in contact with the outer circumference of the circle defined as the second transparent electrode 18, the first liquid crystal region 24 receives the light beam. It is formed in a substantially circular shape when viewed from the direction in which it is performed. Therefore, the second liquid crystal region 26
Is similarly viewed from the direction in which the light beam is incident,
The central portion (that is, a circular region defined by the first liquid crystal region 24 and the separation wall 22) has a cutout shape.

In this embodiment, regarding the light collecting device 10,
The axis defined as the direction in which the light beam should pass, that is, the optical axis, is aligned with the Z axis, and the Z axis is arranged to pass through the center of the first liquid crystal region 24. Therefore, the support plates 12 and 14 are respectively arranged substantially parallel to a plane orthogonal to the Z axis, that is, a plane including the X axis and the Y axis. On the other hand, the crystal orientation direction in the liquid crystal member 20 is the same as that of the transparent electrodes 16 and 18.
Are arranged in parallel with the X axis in a state where no voltage is supplied to both of them. A power supply (that is, a desired voltage is applied to the first and second electrodes 16, 18) for changing the arrangement direction of the crystals of the liquid crystal member 20, which has already been described, is connected to the condensing device 10. Needless to say,

Here, the case where a laser beam (polarized light) having a polarization direction parallel to the X-axis and incident along the optical axis, that is, the Z-axis, is considered with respect to the condensing device 10.

When the voltage is not applied to both the transparent electrodes 16 and 18, that is, the entire area of the liquid crystal member 20 (the first and second liquid crystal areas 24 and 26) separated through the separation wall 22, All the laser beams incident on the light condensing device 10 are emitted with substantially the same optical characteristics as at the time of incidence. On the other hand, when a voltage having a desired magnitude is applied to the first and second transparent electrodes 16 and 18, the arrangement direction of the crystals of the first liquid crystal region 24 is changed. That is, when a voltage is applied to the first and second transparent electrodes 16 and 18, the first liquid crystal region 24 (the liquid crystal member 20) defined corresponding to the area of the second transparent electrode 18 (The area inside the separation wall 22)
Is changed.

More specifically, the first and second transparent electrodes 16 and 18
On the other hand, when no voltage is applied, as described above, the arrangement direction of the crystals of all the liquid crystal members 20 is maintained parallel to the X axis. In this state, since the laser beam whose polarization direction is parallel to the X-axis is incident, the laser beam is emitted with substantially the same optical characteristics as at the time of incidence. On the other hand, when a desired voltage is applied to the transparent electrodes 16 and 18, the liquid crystal member corresponding to the first liquid crystal region 24
The direction of the 20 arrays is changed in the Z-axis direction.

This may be because the refractive index of the laser beam passing through the first liquid crystal region 24 has been substantially changed. In this case, a phase difference is provided between the laser beam passing through the first liquid crystal region 24 and the laser beam passing through the second liquid crystal region 26. Here, regarding the first and second liquid crystal regions 24 and 26, by optimizing the area ratio of each region, the above-mentioned phase difference is set to λ / 2 [r
ad], the beam spot diameter of the laser beam that has passed through the light collecting device 10 is converted into a smaller beam spot diameter than the beam spot diameter immediately before being incident on the light collecting device 10. This indicates that the size of the beam spot when the laser beam emitted from the light condensing device 10 is focused on the recording medium can be made smaller than that of a conventionally used lens or the like.

By changing the voltage applied to the transparent electrodes 16 and 18, the direction of polarization of the laser beam passing through the first liquid crystal region 24 can be changed by 90 °. In this case, an optical member that can pass only a laser beam having polarization in a specific direction,
For example, in combination with an analyzer or the like, a part of the beam spot of the laser beam passing through the light collecting device 10 can be shielded. Needless to say, even when a part of the beam spot is shielded, the size and light intensity of the beam spot are changed as in the method of giving a phase difference to a part of the laser beam.

FIG. 2 shows the principle of changing the beam spot diameter and the light intensity of the laser beam via the condensing device shown in FIG.

Assuming that the beam spot of the laser beam is substantially circular, the light condensing device 10 shown in FIG.
The beam spot divided via the above is shown in FIG. 2 (a).

According to FIG. 2A, the cross-sectional area of the laser beam passing through the first liquid crystal region 24 in the light condensing device 10 is "B", and the laser beam (outside the first liquid crystal region 24) The cross-sectional area of the laser beam passed through the two liquid crystal regions 26 is indicated by "A", respectively. Since the first liquid crystal region 24 is defined according to the area of the second transparent electrode 18 (in FIG. 1), the cross-sectional area “B” is substantially equal to the second transparent electrode 18. It is needless to say that the area is dominant.
In the light-collecting device of the present invention, the sectional areas “B” and “A”
Satisfy the relationship of A> B. Also,
By optimizing the size of “B” and “A”,
The composite amplitude distribution shown in FIG.
(Distribution shape).

FIG. 2 (b) shows the laser beams divided into the area ratios shown in FIG. 2 (a) in a state where each laser beam is independently transmitted to the recording surface of the optical disc Rm. The amplitude distribution of the beam spot is shown.
In this case, the amplitude distribution indicates an energy distribution included in the laser beam that has passed through the condensing device 10, and the absolute value of the amplitude distribution is generally known as an intensity distribution (a state of a beam spot that can be visually observed). ing.

According to FIG. 2B, the amplitude distribution of the beam spot of the laser beam passing through the first liquid crystal region 24 is "Si", and the beam of the laser beam passing through the second liquid crystal region 26 The amplitude distribution of the spot is indicated by “So”, respectively. In this case, a phase difference of λ / 2 [rad] is given between the laser beam passed through the first liquid crystal region 24 and the laser beam passed through the second liquid crystal region 26. This is as described in FIG.

FIG. 2C shows a state in which the amplitude distributions Si and So shown in FIG. 2B are combined, that is, a combination of the beam spots of the laser beam transmitted to the recording surface of the optical disc Rm. The amplitude distribution is defined as “Sr”. Note that Ss in FIG. 2C indicates the amplitude distribution of the beam spot of the laser beam on the recording surface of the optical disc Rm when the light condensing device 10 is not used. As is clear from FIG. 2C, the use of the condensing device of the present invention makes it possible to change the beam spot diameter of the laser beam transmitted to the optical disc Rm to a small value.

The amplitude distributions Si and So correspond to the first liquid crystal region.
It is easily understood that the value is changed according to the size of 24 (the area of the second transparent electrode 18). An example is shown in FIG.
It is clear that when “B” in (a) is gradually increased and B = A is satisfied, the amplitude distributions of the beam spots of the respective laser beams have polarities opposite to each other. In this case, the composite amplitude distribution that can be obtained in the same manner as in FIG. 2C is expected to be approximately “0”. When “B” is further increased and B> A is satisfied, the composite amplitude distribution has a lower peak level and a wider beam spot diameter than Ss in FIG. 2C. Can be expected.

A method of changing the size and light intensity of a beam spot by dividing the beam spot of a laser beam into a plurality of regions is disclosed in Japanese Patent Application No. 3-278400 already filed by the present applicant. Details about the issue.

FIG. 3 shows an example in which the light condensing device shown in FIG. 1 is used, which is incorporated in an optical disk device and records information on the optical disk or reproduces information from the optical disk. An optical head device is shown.

The optical head device 2 includes a semiconductor laser (light source) 30 and a laser 30 which generate a divergent laser beam (light) having a sectional beam shape, ie, an elliptical beam spot.
While correcting the beam spot of the laser beam generated from the laser beam into a substantially circular shape, guiding the laser beam toward the optical disk (recording medium) Rm, and further, the laser beam reflected from the optical disk Rm is reflected from the laser beam toward the optical disk. Polarizing beam splitter 32 for separation
have.

Between the polarizing beam splitter 32 and the laser 30, a collimating lens 34 for converting a laser beam from the laser 30 into a substantially parallel beam is disposed. Between the polarization beam splitter 32 and the optical disc Rm, a light-collecting device 10 (shown in FIG. 1) according to an embodiment of the present invention, and an isolation between a light-transmitting system and a detection system are matched ( The phase difference between the polarization direction of the laser beam toward the optical disk Rm and the polarization direction of the reflected laser beam from the optical disk Rm is 90
The laser beam that has passed through the λ / 4 plate 36 and the polarizing beam splitter 32 is focused on the recording surface of the optical disc Rm, and the reflected laser beam reflected on the recording surface of the optical disc Rm is again parallelized. An objective lens 38 for returning to light is inserted in order. Incidentally, the condensing device 10
May be arranged, for example, between the objective lens 38 and the optical disc Rm or between the laser 30 and the polarizing beam splitter 32.

As described above, the power supply device 28 is connected to the light collecting device 10. In addition, the periphery of the objective lens 38 is energized by a control signal generated with focusing and tracking, which will be described later, and moves the objective lens 38 in the optical axis direction and in a direction parallel to the recording surface of the optical disc Rm. Lens coil 40 is disposed.

On the side of the polarizing beam splitter 32,
In the direction in which the reflected laser beam separated from the laser beam heading for the optical disc Rm via the beam splitter 32 is transmitted, a photodetector for detecting the laser beam reflected on the optical disc Rm and converting it into an electric signal 42
Is arranged. Further, between the polarization beam splitter 32 and the photodetector 42, a focusing lens 44 for focusing the laser beam separated through the polarization beam splitter 32 on the detection surface of the photodetector 42, For this laser beam, a control for enabling beam spot control called focusing and tracking so that the laser beam passed through the objective lens 38 is focused on a desired position on the optical disc Rm with a desired beam spot. A refractor for generating a laser beam, for example, a cylindrical lens 46 is disposed.

The laser beam generated by the laser 30 is
The light beam is converted into a parallel beam through a collimator lens 34, the beam spot is corrected to a substantially circular shape through a polarizing beam splitter 32, and is incident on the light collecting device 10. In this embodiment, the laser 30 is fixed so that the polarization direction of the laser beam is parallel to the X axis.

The laser beam incident on the condensing device 10 is
As already described with reference to FIG. 1, for example, during recording, the laser beam is generated from the laser 30, or during reproduction, the beam spot diameter is changed,
It is emitted toward Rm.

That is, at the time of recording information, the power supply device 28 connected to the light-condensing device 10 is kept in the OFF state, so that the crystal orientation direction in the liquid crystal member 20 is
The state becomes parallel to the X axis. On the other hand, at the time of reproducing information, the power supply device 28 is turned on, and the arrangement direction of the crystal in a part of the liquid crystal member 20, that is, the first liquid crystal region 24 is changed to be parallel to the Z axis.

Therefore, at the time of recording information, the laser beam incident on the condensing device 10 is emitted with substantially the same beam spot diameter and light intensity as at the time of incidence. In contrast,
When reproducing information, a laser beam having a smaller beam spot diameter than the recording beam is emitted. As described above, by reproducing information from the optical disc Rm using the laser beam having a smaller beam spot than during recording, the resolving power at the time of reproduction can be improved. In addition, regarding the recording laser beam, in the past, there was a case where an over-level beam was clearly used in consideration of the attenuation of the light intensity. However, according to the present invention, even if the beam spot diameter is small, Regardless, since a sufficient light intensity is obtained, the length of the recording mark and the recording pitch can be reduced.

The laser beam emitted from the condensing device 10 is converted into circularly polarized light via the λ / 4 plate 36,
The convergence is given by 38 and the recording surface of the optical disc Rm is irradiated. The laser beam applied to the recording surface of the optical disc Rm is reflected on the recording surface of the optical disc Rm. At this time, the reflectance changes depending on whether or not there is information recorded on the optical disc Rm.

The laser beam reflected by the recording surface of the optical disc Rm passes through the objective lens 38 and the λ / 4 plate 36 again in sequence, and is returned to the light collecting device 10. In this case, the direction of polarization of the reflected laser beam is shifted by 90 ° with respect to the direction of polarization of the laser beam toward the optical disc Rm.
(The direction of deflection is changed in the Y-axis direction). By the way, the crystal arrangement direction in the light condensing device 10 is maintained parallel to the X-axis direction during recording. On the other hand, during reproduction, the arrangement direction of the crystals of the first liquid crystal region 24 is maintained parallel to the Z-axis direction. However, the direction of polarization of the laser beam reflected by the optical disc Rm and passed through the λ / 4 plate 36 is directed to the Y axis as described above, so The light is returned to the polarization beam splitter 32 without being affected. The reflected laser beam returned to the polarization beam splitter 32 is reflected toward the photodetector 42 on the λ / 4 plate 36.

The laser beam guided to the photodetector 42 is converted into an electric signal via the photodetector 42, and is converted into a signal.
To be played back as information recorded on the optical disc Rm. In the signal processing circuit 48, an objective lens control signal for controlling a beam spot called the above-mentioned focusing and tracking is simultaneously generated. The lens coil 40 is energized in response to the objective lens control signal, and the laser beam directed to the optical disc Rm is
It is focused at a desired position on Rm with a desired beam spot.

FIG. 4 shows a modification of the embodiment shown in FIG. In addition, about the member same as the member shown in FIG. 1, the same code | symbol is printed and detailed description is abbreviate | omitted.

The light condensing device 50 includes a first support plate 12, a second support plate 14 disposed opposite to the first support plate 12, and a first support plate 12, An outer wall that maintains a constant distance between the two and provides a housing for the light-collecting device 50
Contains 50a.

Inside the first and second support plates 12 and 14,
A first transparent electrode (electrode means) 16 formed in an area approximately equal to the first support plate 12, and at least a part thereof is opposed to the first support plate 12, and the first transparent electrode 16 A desired area ratio is given to the area, and a second transparent electrode (transparent electrode means) 52 formed in an annular shape is arranged. That is, in the light collecting device 50, the second transparent electrode 18 in the light collecting device 10 shown in FIG. 1 is formed in a hollow circular shape.

Inside the first and second support plates 12 and 14 and further inside the first and second transparent electrodes 16 and 52,
A liquid crystal region having at least three crystal regions, that is, first to third liquid crystal regions 60, 62 and 64, each of which is divided via two separation walls 54 and 56 and each of which is formed so as to be capable of independently changing crystal characteristics ( Optical means) 58 are formed. Specifically, the two separating walls 54 and 56 are formed in an annular shape defined so as to be in contact with the inner circumference and the outer circumference of the hollow circle defined as the second transparent electrode 52, respectively. Accordingly, the first liquid crystal region 60 is substantially circular when viewed from the direction in which the light beam is incident, and the second liquid crystal region 62 is similarly viewed from the direction in which the light beam is incident. In this state, they are formed in a concentric annular shape. Needless to say, the third liquid crystal region 64
Is similarly viewed from the direction in which the light beam is incident,
The central portion (ie, the first and second liquid crystal regions 60 and 62 and 2)
A circular area defined by the two separating walls 54 and 56 has a cutout shape.

It goes without saying that the first and third liquid crystal regions 60 and 64 function substantially identically. In other words, the second transparent electrode disposed opposite to the first transparent electrode 16
Only the second liquid crystal region 62 defined by 52 can provide a different crystal alignment as compared to the first and third liquid crystal regions 60 and 64.

Hereinafter, the case where the laser beam (polarized light) is incident on the light collecting device 50 under the same conditions as those of the light collecting device 10 shown in FIG. 1 will be considered.

When a laser beam along the optical axis, that is, the Z-axis and having a polarization direction parallel to the X-axis is incident on the condensing device 50, a voltage is applied to both the transparent electrodes 16 and 52. Otherwise, all the laser beams incident on the light collecting device 50 are emitted with substantially the same optical characteristics as at the time of incidence. On the other hand, when a desired voltage is applied to the transparent electrodes 16 and 52, the arrangement direction of the crystals in the second liquid crystal region 62 is changed. That is, when a voltage is applied to the transparent electrodes 16 and 52, the second liquid crystal region 62 defined corresponding to the shape of the second transparent electrode 52 (the separation walls 54 and 56 The light transmittance of the annular region which is limited by the distance is changed.

In the light-collecting device 50, similarly to the light-collecting device 10, in the liquid crystal region (that is, the second liquid crystal region 62) located between the electrodes to which the voltage is applied, the crystal orientation direction is (X-axis direction). (From a direction parallel to the Z axis direction). Therefore, along the Z-axis and near the center of the light-collecting device 50, that is, between the laser beam passing through the first liquid crystal region 60 and the laser beam passing through the second liquid crystal region 62, and
A desired phase difference is provided between the laser beam passing through the second liquid crystal region 62 and the laser beam passing through the third liquid crystal region 64 outside the second liquid crystal region 62. In this case, by optimizing the area of the second transparent electrode 52, the phase difference between the respective laser beams can be set to λ / 2 [rad]. It goes without saying that the phase difference between the laser beam passing through the first liquid crystal region 60 and the laser beam passing through the third liquid crystal region 64 is the same.

The phases of the laser beam passing through the first liquid crystal region 60 and the third liquid crystal region 64 are the same, and the phases of the laser beam passing through the second liquid crystal region 62 are the first and third. By shifting the laser beam passing through the liquid crystal regions 32 and 36 by λ / 2 [rad], the light intensity of the side lobe that could not be sufficiently reduced in the light condensing device 10 of the first embodiment. Can also be reduced.

FIG. 5 shows a modification of the light collector shown in FIGS.

In the light collecting device 70, an example is shown in which members that function similarly to the first liquid crystal region 24 and the separation wall 22 in the light collecting device 10 shown in FIG. .

That is, the condensing device 70 has an elliptical shape in which an aspect ratio almost equal to the aspect ratio (ratio of the major axis to the minor axis in the ellipse) of the incident laser beam is given. A second transparent electrode 72, a separation wall 74 defined in contact with the outer periphery of the transparent electrode 72, a first liquid crystal region 76 formed through the separation wall 74, and the first A second liquid crystal region 78 defined outside the liquid crystal region 76 is provided. Incidentally, the second transparent electrode 72
It is needless to say that the light-collecting device 50 may be formed in a hollow circular shape as in the light-collecting device 50 shown in FIG.

When this light condensing device 70 is used, for example, regarding the optical head device 2 shown in FIG. 3, the light condensing device 70 is normally combined with the incident surface facing the laser 30 side of the polarizing beam splitter 32. Oval correction function can be omitted.

FIG. 6 shows an embodiment different from the light-collecting device shown in FIGS. 1, 4 and 5.

The light collecting device 90 includes a plate-shaped support 92, and a common electrode formed on the support 92 in an area equal to the area of the support 92.
94a, and a piezoelectric element (piezo element) 96 formed on the common electrode 94a to have a substantially uniform thickness. In a partial area of the piezoelectric element 96, the common electrode 94
A counter electrode 94b having a desired area ratio with respect to the common electrode 94a is disposed at a position facing the common electrode 94a.
A light reflection layer 98 for reflecting a light beam supplied from the outside is formed on a surface of the piezoelectric element 96 including the counter electrode 94b facing the support 92. A power supply (not shown) is connected to the common electrode 94a and the counter electrode 94b. Further, the piezoelectric element 96 is
What was previously divided according to the area of 94b may be used.

The piezoelectric element 96 is known as a member whose thickness changes in response to the applied voltage when a voltage is applied between electrodes sandwiching the piezoelectric element. From this, the light collector 90 can define the entire area of the light reflecting surface 98 to be substantially the same plane when no voltage is applied between the electrodes 94a and 94b. On the other hand, when a voltage is applied between the electrodes 94a and 94b,
Based on the magnitude of the voltage applied between 94a and 94b,
The thickness of the region corresponding to the area of the counter electrode 94b in the piezoelectric element 96 is changed. Therefore, the light reflecting surface 98 is defined as a reflecting surface at least partially not having the same height.

In this case, the condensing device 90 can provide a desired phase difference with respect to the light beam incident on the light reflecting surface 98, as in the other embodiments described above. Incidentally, the light collecting device 90
Obviously, it only functions as a reflective concentrator. Therefore, for example, when used as an optical head device, it goes without saying that the optical path design must be considered.

FIG. 7 shows a modification of the optical head device shown in FIG. In addition, about the member same as the member shown in FIG. 3, the same code | symbol is printed and detailed description is abbreviate | omitted.

According to FIG. 7, the optical head device 100 is formed substantially similar to the embodiment shown in FIG. That is, between the semiconductor laser 30 and the optical disc Rm,
Optical members such as a polarizing beam splitter 32, a collimating lens 34, a light condensing device 10, a λ / 4 plate 36, and an objective lens 38 are sequentially arranged.

By the way, in the optical head device 100,
The condenser device 10 and the objective lens 38 are incorporated in a lens housing 110 that houses each of them integrally. Also,
The lens coil 40 is fixed around the lens housing 110.

This is related to the optical head device 2 shown in FIG. 3, for example, when focusing or tracking, only the objective lens 38 is moved, which may occur when the objective lens 38 and the condensing device 10 are moved. And the effect of the deviation of the optical axis between the two can be reduced. That is, in the optical head device 2 shown in FIG. 3, since only the objective lens 38 is moved during the focusing or tracking, the laser beam passing through the optical axis of the light condensing device 10 and the light of the objective lens 38 are reflected. A displacement or inclination occurs with the shaft.

When a deviation occurs in the optical axis between the condensing device 10 and the objective lens 38, the effective beam spot size of the laser beam emitted from the condensing device 10 toward the objective lens 38 is limited. There is a possibility that. In addition, the coma aberration component of the laser beam traveling from the light focusing device 10 toward the objective lens 38 and the laser beam reflected from the optical disc Rm and returned to the objective lens 38 may be increased. in this case,
With respect to the beam spot guided to the optical disc Rm, there is a possibility that the peak intensity at the beam spot is reduced.

On the other hand, in the embodiment shown in FIG. 7, the objective lens 38 and the condensing device 10 are connected to the lens housing 1.
Be moved at the same time through 10. This means that the light
All of the laser beams that have passed through the objective lens 38 and all of the laser beams that have passed through the objective lens 38 can be incident on the condensing device 10, respectively.

Therefore, through the lens housing 110,
By holding the objective lens 38 and the condensing device 10 integrally,
With respect to the beam spot guided to the optical disc Rm, the laser beam can be effectively used without lowering the peak intensity.

In this embodiment, the first embodiment shown in FIG. 1 has been described as an example of the light-collecting device. However, for example, any one shown in FIGS. It goes without saying that any of the light concentrators (50, 70 or 90) may be used.

[0064]

As described above, according to the present invention, an optical head and an optical disk apparatus having a light condensing device capable of forming a light beam having a small beam spot diameter during reproduction while ensuring sufficient light intensity during recording. Can be provided.

[Brief description of the drawings]

FIG. 1 shows a light collecting device according to an embodiment of the present invention;
(a) is a perspective view showing the appearance of the light collecting device, (b) is (a)
Sectional drawing which cut | disconnected the perspective view of FIG.

FIGS. 2A and 2B are characteristic diagrams illustrating the principle that the beam spot diameter and light intensity of a light beam can be changed by the light condensing device shown in FIG. 1, wherein FIG. 7A and 7B are graphs respectively showing the relationship between the divided area ratio and the amplitude distribution of light.

FIG. 3 is a schematic plan view showing an optical head device into which the light condensing device shown in FIG. 1 is incorporated.

FIG. 4 shows a modification of the light collection device shown in FIG. 1,
(a) is a perspective view showing the appearance of the light collecting device, (b) is (a)
Sectional drawing which cut | disconnected the perspective view of FIG. 4 by line IV-IV.

FIG. 5 shows a modification of the light collection device shown in FIG. 1,
(a) is a perspective view showing the appearance of the light collecting device, (b) is (a)
Sectional drawing which cut | disconnected the perspective view of FIG.

FIG. 6 is a schematic sectional view showing an embodiment different from the light condensing device shown in FIG. 1;

FIG. 7 is a schematic plan view showing a modification of the optical head device shown in FIG.

[Explanation of symbols]

 10… Condenser 12, 14… Support plate 16… First transparent electrode (electrode means) 18… Second transparent electrode (transparent electrode means) 20… Liquid crystal member (optical means) 22… Separation wall 24… First The liquid crystal region 26 of the second liquid crystal region 28 of the power supply device.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H088 EA47 HA24 MA20 5D090 AA01 BB03 BB04 CC01 CC04 DD03 KK01 LL03 5D119 AA09 AA43 BA01 DA01 DA05 FA05 JA30 JA43 5F073 AB21 AB25 AB27 BA05 FA05 FA30

Claims (2)

[Claims] 1. A laser beam emitted from a laser,
An optical head device for irradiating an optical disk through an objective lens, a light-collecting device that causes the laser beam to enter, deforms and emits a spot diameter of the laser beam, and a power supply device that supplies power to the light-collecting device By turning on or off the power supply,
An optical head device, wherein a spot diameter of a laser beam incident on the condensing device is deformed so that a spot diameter of the laser beam at the time of reproduction is smaller than that at the time of recording. 2. A laser beam emitted from a laser,
An optical disk device that includes an optical head device that irradiates an optical disk through an objective lens and records or reproduces information on the optical disk, wherein the optical head device causes the laser beam to enter and deforms the spot diameter of the laser beam. And a power supply device for supplying power to the light collection device, by turning on or off the power supply device,
An optical disc device, wherein a spot diameter of a laser beam incident on the light condensing device is deformed so that a spot diameter of the laser beam at the time of reproduction is smaller than that at the time of recording.