JP2000149304A - Optical disk device and optical pickup as well as hemispherical lens used for the same and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a lens of a low cost by providing a light converging means with a hemispherical lens for holding the surface of an optical disk in an optical contact state, maintaining its aperture ratio at a specific constant and forming planes proximate to the optical disk surface of the hemispherical lens, then forming a spherical portion. SOLUTION: The condenser lens 25 as the light converging means is composed, successively from a light source side, of an objective lens 41 and a front lens 3. The front lens 43 is constituted by first forming a first plane 43a and a second plane 43b, then forming the spherical portion and, therefore, the portions annihilated by polishing in a polishing stage for forming the spherical portion are decreased. Then, the polishing stage ends in a short period of time and the material cost is eventually reduced. If the form of the raw material is a wafer the easy manufacture of the large-sized lens is made possible. Further, the second plane 43b is easily formed with respect to the first plane 43a and, therefore, the accuracy of the first plane 43a and the second plane 43b is easily improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical disk device for recording or reproducing an optical disk signal, an optical pickup, and a method for manufacturing a hemispherical lens used for the optical disk device.

[0002]

2. Description of the Related Art Conventionally, recording and reproduction of information signals on an optical disk such as a magneto-optical disk (MO) are performed by an optical disk device. This optical disc device irradiates a rotating drive means such as a spindle motor for rotating the optical disc with light from a light source via a light focusing means to the rotating optical disc, and focuses the return light from the signal recording surface of the optical disc. An optical pickup for detecting by a photodetector via a means, a biaxial actuator for supporting a light focusing means movably in a biaxial direction, that is, a focusing direction and a tracking direction, and a magnetic field based on a signal to be recorded on an optical disk. And a magnetic head that generates

In the case of reproduction, a light beam emitted from a light source of an optical pickup is condensed on a signal recording surface of an optical disk via a light focusing means. The return light beam from the optical disc is separated from the light beam emitted from the light source via the light focusing means and guided to the photodetector. Thus, the information signal recorded on the optical disc is reproduced based on the detection signal from the photodetector. At this time, the light beam emitted from the light source follows the displacement of the optical disk in a direction orthogonal to the surface direction of the optical disk generated due to the warpage of the optical disk or the like, and is focused on the signal recording surface of the optical disk. Thus, the position of the objective lens in the optical axis direction is adjusted (focus servo). At the same time, the position of the light beam emitted from the light source in the direction perpendicular to the optical axis of the objective lens is adjusted so that the position of the spot on the optical disk follows the eccentricity of the optical disk or the meandering of the track formed on the optical disk. (Tracking servo).

In the case of recording, a light beam emitted from a light source is focused on a signal recording surface of an optical disk by a light focusing means. In this case, the light beam from the light source has a high output, and based on the magnetic field generated by the magnetic head,
Magnetic recording of information signals is performed on the signal recording surface of the optical disk.

[0005]

By the way, the distance D between the optical lens and the optical lens disposed between the optical disk and the light focusing means is increased due to the increase in the density of the optical disk.
A so-called near-field optical recording technique has been developed in which the recording density is increased by setting the optical contact state to an optical contact state and setting the NA of the optical system to 1 or more.

In the practical use of such near-field optical recording technology, it is important to maintain the optical contact state at the distance D, and the assembly accuracy of these optical lenses and light focusing means is extremely high. There is a need to. Further, as the optical lens, a so-called hemispherical lens having, for example, a spherical surface and a flat surface is generally used, and the relationship between the thickness t of the hemispherical lens and the radius of curvature r of the spherical portion depends on the lens. If the refractive index is n, so-called s where t = r
phrase mode (hereinafter referred to as the first mode)
And a so-called super where t = {1+ (1 / n)} r
sphere mode (hereinafter referred to as the second mode)
And, there are two types.

Here, the NA in the first mode (hereinafter, referred to as NA1) is the numerical aperture NA (hereinafter, referred to as NA0) of the objective lens which condenses and makes light incident on the hemispherical lens.
using,

(Equation 1) And NA in the second mode (hereinafter, NA2
Is)

(Equation 2) Since n> 1, the second mode can realize a larger NA than the first mode.

However, in the second mode, since the hemispherical lens refracts light even in the spherical portion, the assembling accuracy and the assembling accuracy are lower than in the first mode.
There are stricter standards for lens manufacturing accuracy, margins due to environmental temperature changes, and the like.

In the method of manufacturing a hemispherical lens described above, generally, as shown in FIG. 8A, a spherical lens A is formed first, and then, as shown in FIG. Next, after the planar portion B is formed by the polishing step, the clamp surface C is finally formed as shown in FIG.
These figures are all rotationally symmetric. In this case, in the spherical surface processing step of FIG. 8A, the size (that is, the radius of curvature) and the surface state of the spherical surface are managed.
In the planar polishing step (B), it is necessary to simultaneously control the dimensional accuracy and the surface state so as to have a predetermined thickness, for example, a thickness equal to the radius of curvature of the spherical surface.

Therefore, since the radius of curvature of the spherical surface is determined by the spherical processing step and the thickness t is determined by the polishing step, it is necessary to control the amount of variation and the absolute value in each step with high precision. If the cost increases, for example, in the plane polishing process, if it has been cut too much or if it has scratches, it cannot be used as a hemispherical lens, and after forming a spherical surface , Because it is made into a hemispherical shape by plane processing,
Material yields cannot be reduced by more than half.

Therefore, when the material of the hemispherical lens is expensive, there is a problem that the cost of the hemispherical lens is particularly high, and the cost of the entire optical disk apparatus is high. In addition, when the plane of the hemispherical lens is used as the crystal cleavage plane of the material, an analysis step such as X-ray analysis is required. In addition, an analysis step is also required to select a so-called easily finished surface that is easily polished. And the cost increases.

Further, when clamping a hemispherical lens, the plane portion B can be brought close to the surface of the optical disk only by the spherical processing step and the plane polishing step shown in FIGS. 8A and 8B. Therefore, it is necessary to clamp at the spherical portion, and it is necessary to clamp the hemispherical lens while holding the flat portion and the optical disk surface in parallel, which makes the clamping operation difficult. For this reason, it is necessary to process the clamp surfaces C on the opposite sides of the hemispherical lens by the clamp surface processing step shown in FIG. 8C, and there is a problem that the number of steps is increased and the manufacturing cost is increased. Was. In particular, when the raw material is in the form of a wafer or the like, it is difficult to manufacture a large lens, and it is difficult to increase the precision (parallelism, squareness, etc.) between the flat surface and the clamp surface. There is a problem that the manufacturing operation is troublesome.

In view of the above, the present invention provides a hemispherical lens held in an optical contact state with an optical disc,
It is an object of the present invention to provide an optical disk device, an optical pickup, a hemispherical lens used therein, and a method of manufacturing the optical disk device and the optical pickup, which are manufactured at low cost.

[0014]

SUMMARY OF THE INVENTION According to the first aspect of the present invention, there is provided a rotary driving unit for driving an optical disk, and a light beam is applied to the rotating optical disk from a light source via a light focusing unit. An optical pickup for detecting return light from the signal recording surface of the optical disc by a photodetector via a light focusing means, and a biaxial actuator for supporting the light focusing means movably in a biaxial direction, that is, a focusing direction and a tracking direction. A signal processing circuit that generates a reproduction signal based on a detection signal from the photodetector, and a servo circuit that moves the optical focusing unit of the optical pickup in two axial directions based on the detection signal from the photodetector. Wherein the light focusing means includes a hemispherical lens held in optical contact with the surface of the optical disc, There has been held in one or more, there is provided an optical disk apparatus, the hemispherical lens, after the plane close to the surface of the optical disc is formed, the spherical portion is formed, the optical disc device is achieved.

According to the second aspect of the present invention, there is provided a light source, a light converging means for converging a light beam from the light source to the rotating optical disk, and a device for returning light from a signal recording surface of the optical disk. A light detector for detecting, wherein the light focusing means includes a hemispherical lens held in an optical contact state with the surface of the optical disc, and the aperture ratio is maintained at 1 or more. The hemispherical lens is achieved by an optical pickup, wherein the hemispherical lens is formed with a flat surface close to the surface of the optical disk and then formed with a spherical portion.

According to a third aspect of the present invention, there is provided a hemispherical lens which is kept in optical contact with a rotating optical disk, wherein the hemispherical lens is provided on a surface of the optical disk. This is achieved by a hemispherical lens, in which a spherical surface is formed after a plane close to is formed.

Still another object of the present invention is to provide a method of manufacturing a hemispherical lens which is kept in an optical contact state with a rotating optical disk. This is achieved by a method of manufacturing a hemispherical lens that includes forming an adjacent plane and subsequently forming a spherical portion.

According to the first, second, third, and eighteenth aspects of the present invention, the hemispherical lens is first polished and then spherically polished, so that the material yield is increased and the cost is reduced. At the same time, a large-diameter lens is easily formed, and the margin of the optical system is increased.

According to the fifth aspect of the present invention, the hemispherical lens has a second plane portion different from the first plane, and the second plane portion is formed before the spherical portion. In this case, since the spherical portion is not formed, the processing of the second plane portion can be performed easily and with high accuracy. Therefore, it can be easily clamped at the time of spherical polishing using the second plane portion as a clamp surface.

According to the present invention, when the material constituting the hemispherical lens is a single crystal having a crystal structure, for example, a material mainly composed of GaAs, GaP, GaN or the like, For example, (100) plane and (110) plane in a cubic crystal structure, (0001) plane, (11-20) plane and (1) plane in a hexagonal crystal structure
Since it has cleavage along the crystal plane such as -120) plane,
By forming the first plane or the second plane along these crystal planes, the first or second plane is easily formed. Further, if the first or second plane is formed by cleaving along these crystal planes, the first or second plane can be formed with high accuracy, and the first or second plane can be formed. The material lost during the formation of the two planes will be reduced. Further, the first plane is set to the (100) plane (claim 8) or (000).
1) By using the surface (claim 12), the surface accuracy can be easily and accurately obtained in the spherical polishing step.

When the radius of curvature of the spherical portion of the hemispherical lens is selected to be equal to the thickness of the hemispherical lens, a particularly large margin in the spherical polishing step can be obtained, and the cost is reduced. Will be. This is especially true if the material is cleaved as described above.
It will be even more effective.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. still,
Since the embodiments described below are preferred specific examples of the present invention, various technically preferred limitations are added.
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows the configuration of an embodiment of a magneto-optical disk drive provided with a hemispherical lens according to the present invention. In FIG. 1, a magneto-optical disc device 1A includes a motor 2 disposed on a rotation axis of an optical disc 1 as a magneto-optical disc, a head 3 disposed on a recording surface side of the optical disc 1, and a connection to the head 3. Head amplifier 4, focus matrix circuit 5, tracking matrix circuit 8, phase compensation circuits 6, 9, amplifier 7,
10 is included.

The motor 2 functions to rotate the optical disk 1 at a predetermined speed. The head 3 functions to write a recording signal supplied from a predetermined device (not shown) to the optical disk 1, read the recording signal written to the optical disk 1, and output it as an MO reproduction signal. In addition, the head 3 functions to output a servo signal used for tracking and focus adjustment of the laser light applied to the optical disc 1 to the focus matrix circuit 5 and the tracking matrix circuit 8 via the head amplifier 4.

The focus matrix circuit 5 functions to calculate a focus error signal from the servo signal supplied from the head 3 and output it to the phase compensation circuit 6. The phase compensation circuit 6 includes the focus matrix circuit 5
The phase compensation of the supplied focus error signal is performed, and the phase compensated signal is output via an amplifier 7 to a focus actuator (described later) provided in the head 3. Tracking matrix circuit 8
Functions to calculate a tracking error signal from the servo signal supplied from the head 3 and output it to the phase compensation circuit 9. The phase compensating circuit 9 compensates the phase of the tracking error signal supplied from the tracking matrix circuit 8, and converts the phase compensated signal into the head 3 via the amplifier 10, for example, a tracking actuator (for example, a voice coil) provided in the head 3. (Not shown).

FIG. 2 shows a detailed configuration of the head 3. In FIG. 2, the head 3 includes a magnetic field generator 3A for writing a recording signal to the optical disc 1 and reading the recording signal written to the optical disc 1, and an optical pickup 3B. The magnetic field generator 3A includes an amplifier 36 and a magnetic field modulation coil 42. The optical pickup device 3B includes a semiconductor laser (light source) 21, a collimator lens 22, a shaping prism 23, beam splitters 24, 26, and 32, and a condenser lens 2 as a light focusing unit.
5, lenses 27, 31, a cylindrical lens 28, photodetectors 29, 33, 34, a half-wave plate 30, and a differential amplifier 35. Here, the condenser lens 25
Is composed of an objective lens 41 and a front lens 43.

The semiconductor laser 21 functions to generate a laser beam of a predetermined wavelength and make it incident on the collimator lens 22. The collimator lens 22 is a semiconductor laser 21
The laser beam from the laser beam is made into a parallel beam and functions to enter the beam splitter 24 via the shaping prism 23. The beam splitter 24 functions to make the laser light from the shaping prism 23 incident on the objective lens 41 and reflect the laser light (return light) from the objective lens 41 toward the beam splitter 26.

The condensing lens 25 has an objective lens 41 and a front lens 43 of the optical pickup device 3B. At the time of data reproduction, the objective lens 41 and the front lens 43 apply the laser light from the beam splitter 24 to the optical disk. It functions to irradiate the recording layer 1b formed on one substrate 1a and to make the return light reflected by the recording layer 1b incident on the beam splitter 24. Here, at the time of data recording, the magnetic field modulation coil 42 applies a magnetic field having an intensity corresponding to the recording signal supplied via the amplifier 36 to the irradiation position of the laser beam.

The beam splitter 26 reflects a part of the return light reflected by the beam splitter 24 at a predetermined ratio to make it enter the lens 27, and transmits a part of the return light to form a half-wave plate. Through the lens 3
It functions so as to be incident on the light source 1. The lens 27 functions to convert return light (parallel rays) from the beam splitter 26 into convergent light and to make it incident on the photodetector 29 via a cylindrical lens 28 that gives astigmatism. The photodetector 29 has a light receiving portion divided into four parts, and functions to convert the laser light incident on each light receiving portion into an electric signal and output the electric signal to the head-up 4 as a servo signal.

The lens 31 functions to convert the return light from the half-wave plate 30 into convergent light and make it incident on the beam splitter 32. The beam splitter 32 includes a lens 31
A part of the convergent light from the light source is transmitted and made incident on the photodetector 33, and a part of the convergent light is reflected and the light
4 so as to be incident. The photodetector 33 and the photodetector 34 function to output an electric signal corresponding to the amount of return light from the beam splitter 32 to the differential amplifier 35, respectively. The differential amplifier 35 includes a photodetector 33
And the output of the photodetector 34 is calculated, and the calculation result is output to a predetermined device (not shown) as an MO reproduction signal.

FIG. 3 shows a first configuration example of the condenser lens 25. In FIG. 3, a condenser lens 25 as a light converging unit includes an objective lens 41 and a front lens 43 in order from the light source 21 side.

The objective lens 41 is composed of, for example, a single convex lens. Based on the focus error signal calculated by the above-described tracking matrix circuit 8, the objective lens 41 is driven by a focus actuator 45 provided in the head 3. Fine movement adjustment is performed in the focus direction, and focus servo is performed.

The front lens 43 is located on one side, that is, the optical disk 1.
The first side is a first flat surface 43a, and the other side, that is, one hemispherical lens whose light source side is a spherical surface 43c, is held at a predetermined distance from the surface of the optical disc 1 as described later. ing.

Further, the front lens 43 is formed integrally with the objective lens 41 as shown in FIG.
That is, the second flat surface 43 formed on the side surface of the front lens 43
b is fixedly held to a lens frame 44 that supports the objective lens 41.

In such a configuration, the laser beam from the beam splitter 24 is converged by the objective lens 41 of the condenser lens 25, then converged by the front lens 43, and irradiated onto the optical disc 1. In this case, the focus servo of the objective lens 41 and the front lens 43 is performed by the actuator 45 based on a focus error signal from the amplifier 7. Further, at the time of data recording, a magnetic field corresponding to a recording signal supplied from a predetermined device is generated by the magnetic field modulation coil 42, and is applied to the irradiation position of the laser beam by the optical pickup 3B.

Here, the front lens 43 is manufactured, for example, as shown in FIG. These are all rotationally symmetric shapes. The material 50 is shown in FIG.
A first planar portion 51 and a second planar portion 52 are formed, and then a spherical portion 53 is formed as shown in FIG. When the radius of curvature R of the spherical portion 53 of the front lens 43 is equal to the thickness t of the lens 43, the material 50 is firstly deposited on the first flat portion 51 as shown in FIG. After the second flat portion 52 is formed, the radius of curvature R and the thickness t are controlled when the spherical portion 53 is polished as shown in FIG. 5B. Therefore,
Even if the absolute value of the radius of curvature R varies, the relationship between the radius of curvature R and the thickness t is constantly polished.

Further, when the material 50 is a single crystal having a crystal structure having a cleavage property, the first plane portion 51 or the second plane portion 52 is first formed as shown in FIG.
The first plane portion 51 or the second plane portion 52 can be easily formed by the dicing step or the cleaving step by using the crystal growth plane and the cleavage plane. Here, when the second plane part 52 is a crystal plane and a cleavage plane of the material 50, the angle of the second plane part 52 with respect to the first plane part 51 can be easily made a right angle, and It is possible to easily make the second flat portions 52 on both sides parallel.

In particular, when the material 50 is cubic GaAs, G
When composed of a material containing aP and GaN as main components, it is a (100) plane which is a crystal plane or a cleavage plane (1).
10) The plane is set to the first flat portion 51 or the second flat portion 5
2, the first flat portion 5 can be easily formed.
A first or second planar portion 52 will be formed.
In this case, the (100) plane or the (110) plane is suitable as the first plane part 51, and the (110) plane is suitable as the second plane part 52.

When the material 50 is composed of a material containing hexagonal GaN as a main component, the (0001) plane which is a crystal plane or the (1-100) plane which is a cleavage plane,
By forming the (11-20) plane as the first plane part 51 or the second plane part 52, the first plane part 51 or the second plane part 52 can be easily formed. In this case, as the first plane portion 51, (0
The (001) plane, the (1-100) plane, or the (11-20) plane is suitable.
The (01) plane or the (1-100) plane is suitable.

The magneto-optical disk drive 1A according to the present embodiment
Is configured as described above, and during data playback,
In FIG. 3, the laser beam from the beam splitter 24 is incident on the objective lens 41 of the condenser lens 25, is focused by the objective lens 41, is further focused by the front lens 43, and is recorded on the optical disc 1. It converges on layer 1b. Then, the return light reflected by the recording layer 1b is
The light again enters the beam splitter 24 via the front lens 43 and the objective lens 41, is converted into an electric signal by the photodetectors 33 and 34, an MO reproduction signal is generated by the differential amplifier 35, and the data is reproduced. It is. Further, at the time of data recording, a magnetic field having an intensity corresponding to the recording signal supplied via the amplifier 36 is applied to the laser beam irradiation position of the optical disk 1 by the magnetic field modulation coil 42, and the data is recorded. ing.

In this case, as described above, the front lens 43 has the first plane 43a and the second plane 43b formed first, and then the spherical part is formed. In the polishing step for forming the layer, there are few portions that disappear by polishing. Therefore, the polishing process is performed in a short time, and the material cost is reduced. When the raw material is in the form of a wafer, a large lens can be easily manufactured. Further, since the second plane 43b is easily formed with respect to the first plane 43a, the first plane 43a and the second plane
The accuracy (parallelism, squareness, etc.) with 3b can be easily improved, and the front lens 43 can be easily clamped.

When the radius of curvature R of the spherical portion of the front lens 43 is equal to the thickness t, the relationship of R = t is easily maintained when the spherical portion is polished as described above. Therefore, in the sphere mode optical disc device 10 or the optical pickup 3, the front lens 43 is
If the relationship of R = t is satisfied, the optical performance is maintained, so that the management in the polishing process of the front lens 43 may be loose, and the cost is reduced.

In particular, when the material of the front lens 43 is a material having a cleavage property, for example, GaAs, GaP, GaN, or the like as a main component, the chipping of the material occurs frequently in the polishing step. Is generated, the front lens 43 is manufactured by further polishing. Therefore, the costs of the front lens 43, the optical pickup 3, and the optical disk device 10 are reduced.

Further, the first plane 43 of the front lens 43
When the a or the second plane 43b is formed along the crystal plane or cleavage plane of the material, the finish of polishing tends to be highly accurate, and the loss of the material hardly occurs, so that the material cost is reduced. Will be.

FIG. 7 shows a second configuration example of the condenser lens in the magneto-optical disk device 1A. 7, the condensing lens 60 has basically the same configuration as the condensing lens 25 shown in FIG. 3, except that the optical contact state of the front lens 43 with the optical disc 1 is maintained by an actuator. Suspension 62, not 45
Only in that it is performed by the slider 61 supported by the.

The slider 61 travels at a constant flying height with respect to the surface of the optical disk 1 by the air lubrication surface provided on the optical disk 1 side. The contact state is maintained. In FIG. 7, the objective lens 41, the lens frame 44, and the actuator 45 are omitted.

According to the condenser lens 60 having such a configuration, the front lens 43 is held in an optical contact state with the optical disc 1 by the slider 61. Thus, the light beam from the beam splitter 24 is transmitted from the objective lens 41 via the front lens 43 to the optical disc 1.
The return light from the optical disc 1 is focused on the recording layer 1b of the optical disc 1 and the photodetectors 33 and 34 and the photodetector 52, respectively.
, An MO reproduction signal is detected.

In this case, similarly, the front lens 43 is firstly moved to the first plane 43a and the second plane 4 as described above.
3b is formed, and then a spherical portion is formed. Therefore, in the polishing step for forming the spherical portion, a small portion is eliminated by polishing. Therefore, the polishing process is performed in a short time, and the material cost is reduced. When the raw material is in the form of a wafer, a large lens can be easily manufactured. Furthermore, since the second plane 43b is easily formed with respect to the first plane 43a, the accuracy (parallelism, squareness, etc.) between the first plane 43a and the second plane 43b is easily improved. In addition, the clamping of the front lens 43 is easily performed.

In the above-described embodiment, the magnetic field modulation coil 42 is disposed on the opposite side of the optical disk 1 from the condenser lens 25, but is not limited to this, and is disposed on the same side as the condenser lens 25. It may be.

In the above-described embodiment, the optical disk apparatus for recording / reproducing a magneto-optical disk has been described. However, the present invention is not limited to this, and other types of optical disks employing near-field optical recording technology, for example, phase change Obviously, the present invention can be applied to an optical disk device for a read-only optical disk such as a recordable optical disk or a compact disk (CD).

[0051]

As described above, according to the present invention, since the hemispherical lens is first subjected to the planar processing and then to the spherical polishing, the material yield is increased and the cost is reduced. At the same time, a large-diameter lens is easily formed, and the margin of the optical system is increased. Thus, according to the present invention, an optical disc device, a hemispherical lens used for the optical disc device, and a lens manufactured therefor are stably maintained while maintaining an optical contact state between the optical lens and the optical disc. A method can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram illustrating a configuration of a first embodiment of a magneto-optical disk device to which the present invention has been applied.

FIG. 2 is a schematic diagram showing a configuration of a head in the magneto-optical disk device of FIG.

FIG. 3 is a schematic diagram illustrating an optical configuration of a first configuration example of a condenser lens in the head of FIG. 2;

4 is a process chart sequentially showing a first example of a manufacturing process of a front lens in the condenser lens of FIG. 3;

FIG. 5 is a process chart sequentially showing a second example of the manufacturing process of the front lens in the condenser lens of FIG. 3;

FIG. 6 is a process chart sequentially showing a third example of the manufacturing process of the front lens in the condenser lens of FIG. 3;

FIG. 7 is a schematic diagram illustrating an optical configuration of a second configuration example of the condenser lens in the head of FIG. 2;

FIG. 8 is a process diagram sequentially showing an example of a manufacturing process of a hemispherical lens used as a front lens in an optical disk device using a conventional near-field optical recording technique.

[Explanation of symbols]

1A: magneto-optical disk device, 1: optical disk,
3 ... head, 3A ... magnetic field generator, 3B ...
Optical pickup, 25, 60: Condensing lens (light focusing means), 41: Objective lens, 42: Magnetic field modulation coil, 43: Front lens (hemispherical lens), 44
... Lens frame, 45 ... Actuator, 50 ...
-Material, 51 ... first plane portion, 52 ... second plane portion, 53 ... spherical surface portion, 60 ... condensing lens, 61 ... slider.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) G11B 7/22 G02B 7/11 L (72) Inventor Isao Ichimura 6-7 Kita Shinagawa, Shinagawa-ku, Tokyo No. 35 Inside Sony Corporation (72) Inventor Kiyoshi Osato 6-7-7 Kita Shinagawa, Shinagawa-ku, Tokyo F-term inside Sony Corporation (reference) 2H051 AA14 BA41 CB07 CB15 CB19 GB01 2H087 KA13 LA01 MA06 PA02 QA07 QA13 QA21 UA02 5D119 AA22 AA40 BA01 BB05 JA44 JB02 JB06 NA05

Claims (18)

[Claims] A light source for irradiating the rotating optical disk with a light beam from a light source through a light focusing means, and returning light from a signal recording surface of the optical disk through the light focusing means; An optical pickup that detects light by a photodetector, a biaxial actuator that supports a light focusing means movably in a biaxial direction, that is, a focusing direction and a tracking direction, and generates a reproduction signal based on a detection signal from the photodetector. A signal processing circuit, and a servo circuit for moving the light focusing means of the optical pickup in two axial directions based on a detection signal from the photodetector. An optical disc device including a hemispherical lens held in an optical contact state and having an aperture ratio of 1 or more, An optical disk device, wherein the hemispherical lens has a spherical surface formed after a flat surface close to the surface of the optical disk is formed. 2. A light source comprising: a light source; light focusing means for focusing a light beam from the light source on a rotating optical disk; and a light detector for detecting return light from a signal recording surface of the optical disk. An optical pickup in which the focusing means includes a hemispherical lens held in an optical contact state with respect to the surface of the optical disk, wherein the aperture ratio is held to 1 or more; An optical pickup characterized in that a spherical portion is formed after a plane close to the surface of an optical disk is formed. 3. A hemispherical lens held in an optical contact state with an optical disk, wherein the hemispherical lens has a spherical portion formed after a plane close to a surface of the optical disk is formed. A hemispherical lens. 4. The radius of curvature of the spherical portion of the hemispherical lens is:
4. The hemispherical lens according to claim 3, wherein the thickness is selected to be equal to the thickness of the hemispherical lens. 5. A hemispherical lens comprising a second planar portion different from said first planar surface, said second planar portion being formed before said spherical portion. Item 4. A hemispherical lens according to item 3. 6. The hemispherical lens according to claim 3, wherein the material forming the hemispherical lens has a single crystal structure. 7. A hemispherical lens having a second plane portion different from the first plane, wherein the second plane portion is formed before the spherical portion, and a material constituting the lens Has a cubic crystal structure. 7. The hemispherical lens according to claim 6, wherein 8. The method according to claim 7, wherein the first plane is a (100) plane in a cubic crystal structure.
2. The hemispherical lens according to 1. 9. The method according to claim 7, wherein the first plane is a (110) plane in a cubic crystal structure.
2. The hemispherical lens according to 1. 10. The hemispherical lens according to claim 7, wherein the second plane is a (110) plane in a cubic crystal structure. 11. The hemispherical lens according to claim 6, wherein the material has a hexagonal crystal structure. 12. The hemispherical lens according to claim 11, wherein the first plane is a (0001) plane in a hexagonal crystal structure. 13. The hemispherical lens according to claim 11, wherein the second plane is a (11-20) plane in a cubic crystal structure. 14. The hemispherical lens according to claim 11, wherein the second plane is a (1-100) plane in a cubic crystal structure. 15. The hemispherical lens according to claim 6, wherein the material is a material containing GaAs as a main component. 16. The hemispherical lens according to claim 6, wherein the material is a material containing GaP as a main component. 17. The hemispherical lens according to claim 6, wherein the material is a material containing GaN as a main component. 18. A method of manufacturing a hemispherical lens that is kept in optical contact with a rotating optical disc, comprising: forming a first plane close to the surface of the optical disc; Forming a hemispherical lens.