JP2000322755A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup capable of recording/reproducing information stably for a long time without any reductions in the optical performance of an optical element caused by a contaminant. SOLUTION: This optical pickup is provided with an optical element 109 for further drawing a converged light from an objective lens 108 to irradiate the recording surface 112a of a recording medium 112 with it. The optical element 109 is provided with an adsorbing part 200 formed to adsorb a contaminant in the region of a recording medium side surface opposite the recording surface 112a of the recording medium 112 excluding its optical effective region F. The adsorbing part 200 is provided with a rough surface 202 formed by specified etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for performing high-density recording / reproduction by bringing an optical element such as an SIL (Solid Immersion Lens) having the function of increasing the numerical aperture into or out of contact with a recording medium.

[0002]

2. Description of the Related Art For example, Japanese Patent No. 25553275 discloses that a focused light from an objective lens is
L) to further reduce the spot diameter on the recording medium by increasing the numerical aperture by a multiple corresponding to the refractive index of the hemispherical SIL, thereby performing high-density recording and reproduction of information on the recording medium. Optical systems capable of doing so have been proposed.

The recording / reproducing technique of this optical system is different from the recording / reproducing technique for a disk having a recording surface on the back side (for example, CD, MO, etc.). The information is recorded and reproduced while the hemispherical SIL is in contact with or close to the surface (recording surface).

Further, as an improvement of such a recording / reproducing technique, for example, in Nikkei Electronics 1997.6.16 (No. 691), a lens called a super hemispherical SIL, a super hemispherical SIL or a stigmatic focusing solid immersion lens is disclosed. An optical system used has been proposed, in which the numerical aperture is
It increases by a multiple corresponding to the square of the refractive index of the lens.

[0005] For example, Japanese Patent Application Laid-Open No. 8-315404 discloses an optical pickup device having an optical system in which an objective lens and a substantially hemispherical SIL are combined.
In this optical pickup device, information is recorded and reproduced while a substantially hemispherical SIL is brought close to a recording medium having a thin cover glass on the surface.

In each of the conventional techniques described above, it is necessary to bring a high numerical aperture lens (SIL) very close to a recording medium during recording and reproduction. A typical example is at least 5
It is necessary to make the distance close to 00 μm or less or 200 nm or less. The numerical aperture increased by the high numerical aperture lens is at least 0.65 or more.
Techniques for increasing the numerical aperture to 0.8 to 0.9 or more have been announced by academic societies and the like.

[0007]

However, the prior art as described above has the following problems.

A transparent protective film is provided on the recording surface of the recording medium in order to protect the recording surface, and the surface of the protective film is contaminated with moisture, organic matter or dust in the air. Material is attached. On the other hand, since the optical element (SIL) as described above is arranged very close to the surface of the protective film of the recording medium, when the recording medium is rotated during recording / reproduction, the contaminant acts on the contaminant at that time. Are scattered and adhere to and deposit on the optical element (SIL). Specifically, contaminants scattered from the surface of the protective film of the recording medium are transferred to an optical element (SIL) facing the recording medium.
And adhere to and accumulate on the opposing surface of. Then, the optical element (SI
As the deposition and deposition of contaminants on the optically effective area of the optical element (SIL) progresses due to the deposition and deposition of contaminants on the opposing surface of L), the transmittance of laser light gradually decreases (the optical property of the optical element). Performance gradually decreases), and it becomes difficult to perform stable recording and reproduction of information over a long period of time.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to stably record and reproduce information for a long period of time without deteriorating the optical performance of an optical element due to contaminants. An object of the present invention is to provide an optical pickup that can perform the optical pickup.

[0010]

In order to achieve the above object, the present invention provides a light source, an optical system for converging laser light from the light source, and an optical element having a function of increasing a numerical aperture. An optical pickup that performs recording and reproduction by bringing the optical element into contact with or in proximity to a recording medium, wherein the optical element has an area other than the optically effective area on the surface facing the recording medium. And an adsorbing section for adsorbing contaminants. In addition, the present invention includes a light source, an optical system that focuses laser light from the light source, and an optical element that has an effect of increasing the numerical aperture. An optical pickup that performs recording and reproduction by using an optically effective surface of the surface facing the recording medium so that the flow velocity and pressure of the air flow between the optical element and the recording medium are increased. In a region including at least a part of the region, a protruding portion protruding toward the recording medium is provided.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical pickup according to a first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, an optical pickup 100 according to this embodiment includes a light source (semiconductor laser) 104 capable of emitting recording and reproducing laser light, and a light source 104.
A deflection optical element for scanning the laser light emitted from the lens in a predetermined direction, for example, a galvanometer mirror 106, an imaging lens 110 for converting the laser light emitted through the galvanometer mirror 106 into a substantially parallel light beam, Lens 1
And an optical head 128 for condensing the laser light guided through the recording medium 112 on the recording surface 112a of the recording medium 112.

Further, the optical pickup 10 of the present embodiment
0 is provided with a light guiding optical system 114 for guiding the laser light from the light source 104 to the galvanomirror 106,
The light guide optical system 114 includes a collimator lens 116 that converts a laser beam from the light source 104 into a parallel light beam, and a relay lens 118 that condenses the parallel light beam emitted from the collimator lens 116 again. .

In the optical path between the collimator lens 116 and the relay lens 118, the galvanomirror 10
A signal detector 120 capable of optically detecting the tracking state detection signal and the recording signal by receiving the return light from the laser beam 6 (reflected light reflected from the recording surface 112a of the recording medium 112) is provided.

The signal detector 120 includes a galvanomirror 1
Beam splitter 124 that reflects the return light from
And a light receiving element 126 that receives the return light reflected from the beam splitter 124 and outputs an electric signal (that is, a tracking state detection signal and a recording signal) corresponding to a change in the light receiving position and the amount of received light. I have.

The optical head 128 reflects a laser beam guided from the light source 104 through the galvanometer mirror 106 and the imaging lens 110 toward the recording medium 112, and reflects the laser beam from the reflection mirror 132. An objective lens 108 for converging a laser beam;
And an optical element (a lens with a high numerical aperture) 109 for irradiating the twelve recording surfaces 112a. The optical element 109 has a function of increasing the numerical aperture.

The optical head 128 is mounted on the end of a swing arm (not shown), and the optical head 128 is moved in the radial direction of the recording medium 112 by operating the swing arm. There are a type in which the optical head 128 is swung in a curved shape along the direction and a type in which the optical head 128 is linearly moved in parallel along the radial direction of the recording medium 112, and both types are optical pickups according to the present embodiment. 100 configurations.

According to such a configuration, the optical head 128 is swung or translated along the recording medium 112 in a state where the laser beam is focused on the recording surface 112a of the recording medium 112. The spot position of the laser beam on the recording surface 112a of the laser beam 112 is roughly adjusted (coarse movement tracking control). At this time, by rotating the galvanomirror 106 in the direction of arrow R,
The spot position of the laser beam with respect to the recording surface 112a of the recording medium 112 is finely adjusted (finely tracking control).

While such coarse and fine tracking control is being performed, the laser light emitted from the light source 104 is transmitted to the light guide optical system 114 and the galvanomirror 10.
After being irradiated from 6 through the imaging lens 110 to the reflection mirror 132, the light is condensed on the recording surface 112 a of the recording medium 112 from the objective lens 108 by the optical element 109. At this time, the optical element 109 is on the recording surface 1 of the recording medium 112.
12a is in contact with or in proximity to 12a. As a result, the recording medium 1
Optical recording or optical reproduction of information on the 12 recording surfaces 112a is performed.

In the optical pickup 100, the optical element 109 of the optical head 128 is driven by aerodynamic lift acting between the recording medium 112 rotating at a high speed and the optical element 109 during recording and reproduction. The recording medium 112 is slightly floated from the recording surface 112a of the recording medium 112 and is stable. Therefore, laser light can be focused on the recording surface 112a of the recording medium 112 without performing focus control.

The optical pickup 10 according to the present embodiment
0 has a configuration (see FIG. 2) for performing stable recording and reproduction of information over a long period of time without deteriorating the optical performance of the optical element 109 due to contaminants.

As shown in FIG. 2, an optical element (a lens with a high numerical aperture) 109 applied to the present embodiment is a recording medium 1
12 is a hemispherical lens having a substantially flat surface facing the recording surface 112a, that is, a recording medium side surface, and can be formed of, for example, TIH53 manufactured by Ohara Optical Co., Ltd. Also,
On the surface of the optical element 109 on the recording medium side, an adsorbing section 200 for adsorbing contaminants is provided in an area other than the optically effective area F.

The optically effective area F of the optical element 109 is
The area where the laser light focused by the objective lens 108 is further narrowed down via the optical element 109 and focused on the recording surface 112a of the recording medium 112.
9 indicates an area defined in a substantially central portion of the recording medium side surface.

The suction unit 200 is provided on the recording medium side surface of the optical element 109 excluding the optically effective area F.
In the present embodiment, as an example, the suction section 200 is configured by the rough surface 202. In this case, the suction unit 20
The occupied area of the rough surface 202 as 0 is the optically effective area F
It is preferable to set it to be larger than that in terms of improving the adsorptivity.

As a method of forming the rough surface 202 as the attraction portion 200, for example, a mask (diameter of about 10 μm) slightly larger than the optically effective area F is provided at a substantially central portion of the surface of the optical element 109 on the recording medium side. (Not shown), and a predetermined etching process is performed to form a rough surface 202. In this case, as the etching method, it is possible to select chemical etching or physical etching.

In the chemical etching, the surface on the recording medium side of the optical element 109 except for the masked optically effective area F is slightly dissolved with an etchant such as various kinds of acid (hydrofluoric acid) or an alkaline chemical. Thereby, the rough surface 202 can be formed. In this case, the time required for chemical etching is preferably set based on an etching rate determined by the material of the optical element 109.

In the physical etching, the rough surface 202 is formed by irradiating, for example, an ion beam, an electron beam, or plasma to the surface of the optical element 109 other than the masked optically effective area F, on the recording medium side. be able to. In this case, particularly when performing physical etching by electron beam irradiation, it is preferable to select a mask material that does not affect the optically effective area F by the electron beam.

According to such an etching process, the rough surface 2 having a very fine pitch of the molecular level can be obtained.
02 can be formed. Surface roughness is the surface energy based on the contact angle with water (the ability to adsorb pollutants)
It can be expressed as the height of In this case, the level of the surface roughness is such that the contact angle is 60 degrees or less, preferably
It is desirable that the angle is set to 30 degrees or less, more preferably 10 degrees or less. By setting the contact angle small in this way, it is possible to form the rough surface 202 having a very high surface energy (contaminant adsorption ability) as compared with the optically effective area F.

Then, after the above-described etching process is completed, the mask is removed to remove a mirror-like optically effective area F and a rough surface whose periphery is white and rough by etching as shown in FIG. The optical element 109 having the recording medium side surface composed of the optical element 202 can be realized.

As described above, according to the present embodiment, the optical element 1
On the recording medium side surface 09, around the optically effective area F, a rough surface 202 having a very high surface energy (contaminant adsorption ability) as compared with the optically effective area F was formed. Contaminants (such as moisture, organic matter, and dust in the air) scattered from the recording medium 112 during reproduction are strongly attracted to the rough surface 202 having high surface energy and are preferentially adsorbed on the rough surface 202. For this reason, it is possible to prevent adhesion and deposition of contaminants to the optically effective area F, and as a result, without lowering the optical performance of the optical element 109 due to the contaminants
An optical pickup 100 capable of performing stable recording and reproduction of information over a long period of time can be realized.

The present invention is not limited to the above-described embodiment, but can be variously modified as follows.

In the above embodiment, the optical element 109
Is formed using TIH53 manufactured by Ohara Optical Co., Ltd., but if the numerical aperture can be increased, the optical element 109 may be formed using, for example, glass or a transparent optical crystal.

Further, on the surface of the optical element 109 on the recording medium side, the optically effective area F may be coated with a coating having an optical effect such as anti-reflection. In this case, it is preferable to select a material that does not affect the coating material as the etchant.

On the recording medium side surface of the optical element 109, a coating having water repellency may be applied to the optically effective area F. As the coating material, a commercially available water-repellent coating agent or fluoride can be selected, and by applying such a coating, the effect of preventing contamination of the optically effective area F can be further enhanced.

Next, an optical pickup according to a second embodiment of the present invention will be described with reference to FIG. In the description of the present embodiment, the same components as those of the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The present embodiment relates to an improvement of the first embodiment, and more specifically, to an improvement of the suction portion 200 on the surface of the optical element 109 on the recording medium side. Since it is the same as the embodiment, in the following description, the description will be limited to the improved part (the suction unit 200).

As shown in FIG. 3, the suction section 200 is constituted by a plurality of (in the drawing, six as an example) grooves 204. These six grooves 204 are provided on each side of the optically effective area F by three in parallel with each other.

These grooves 204 can be formed by mechanically cutting the surface of the optical element 109 on the recording medium except for the optically effective area F.

By forming these grooves 204, the surface energy of the adsorbing section 200 is reduced to the optically effective area F.
Therefore, contaminants (moisture, organic matter, dust, and the like in the air) scattered from the recording medium 112 during recording and reproduction are strongly attracted to the grooves 204 having a high surface energy. Is preferentially adsorbed to the groove 204. For this reason, it is possible to prevent adhesion and deposition of contaminants to the optically effective area F, and as a result, to stably record information for a long period of time without deteriorating the optical performance of the optical element 109 due to the contaminants. Optical pickup 100 capable of performing reproduction and reproduction (FIG. 1)
Reference) can be realized.

In the present embodiment, as an example, the suction section 200 is constituted by six grooves 204. However, if the number of grooves 204 is further increased, the suction section 2
The surface energy (adsorption ability of contaminants) can be increased.

The grooves 204 are provided in the recording medium 112, respectively.
It is preferable to arrange the recording tracks (not shown) formed on the recording surface 112a (see FIG. 1) in a tangential direction. By arranging the grooves 204 in such a direction, the surface of the optical element 109 on the recording medium side and the recording medium 1
12 can be obtained (rectification (hard to disturb)) of the airflow between the optical element 10 and the optical element 10 during recording and reproduction.
When the air 9 is levitated by air, the flying height can be stabilized.

Further, the shape, length, depth, etc. of the groove 204
Needless to say, it is possible to set a desired size and size or to arbitrarily combine them according to the purpose of use.

Next, an optical pickup according to a third embodiment of the present invention will be described with reference to FIG. In the description of the present embodiment, the same components as those of the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

This embodiment relates to an improvement of the first embodiment, and more specifically, relates to an improvement of the optical element 109, and the other configuration is the same as that of the first embodiment. In the following description, only the improvement (the optical element 109) will be described.

As shown in FIGS. 4 (a) and 4 (b), the optical element 109 has a recording medium having at least a part of the optically effective area F on the surface of the recording medium on the recording medium side more than the other parts. A rectangular protrusion 206 protruding in the 112 direction is provided.

As a method of forming the protruding portion 206, a method of forming the optical element 109 simultaneously during the manufacturing process, a method of mechanically shaping at least a portion other than the optically effective area F after manufacturing the optical element 109, and the like. Can be used. In this case, it is preferable that the projecting portion 206 is formed so as to project along a direction crossing the rotation direction R of the recording medium 112.

As described above, the protrusion 20 is formed on the surface of the recording medium.
6, the air flow between the surface of the optical element 109 and the recording medium 112 is protruded when the recording medium 112 is rotated during recording and reproduction. In the vicinity of the optically effective area F where the portion 206 is provided, both the flow velocity and the pressure are increased. In this case, the contaminants scattered from the recording medium 112 are blown off in a direction away from the optically effective area F by the increased airflow. it can. As a result, it is possible to realize the optical pickup 100 (see FIG. 1) capable of performing stable recording and reproduction of information for a long time without deteriorating the optical performance of the optical element 109 due to contaminants.

The shape and the amount of protrusion of the protrusion 206 can be variously changed depending on the purpose of use. For example, as shown in FIGS. 4 (c) and 4 (d), if the protruding portion 206 having a concave central portion is formed, the air flow can be concentrated on the central portion. The flow velocity and pressure in the vicinity of the optically effective area F can be further increased.

Next, an optical pickup according to a fourth embodiment of the present invention will be described with reference to FIG. In the description of the present embodiment, the same components as those of the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The present embodiment relates to an improvement of the first embodiment, and more specifically, to an improvement of the suction section 200 on the surface of the optical element 109 on the recording medium side. Since it is the same as the embodiment, in the following description, the description will be limited to the improved part (the suction unit 200).

As shown in FIG. 5, the adsorbing section 200 is constituted by a thin film 208. This thin film 208 is made of a metal oxide such as tantalum oxide, silicon oxide, titanium oxide, zirconium oxide, and aluminum oxide. Is formed.

As a method of forming the thin film 208 as the attraction portion 200, for example, a mask (diameter of about 10 μm) slightly larger than the optically effective area F is formed at the approximate center of the surface of the optical element 109 on the recording medium side. After that, a thin film 208 is formed by vapor deposition (chemical vapor deposition, physical vapor deposition) of the above metal oxide.

When such a thin film 208 is expressed as a height of surface energy (contaminant adsorption ability) based on a contact angle with water, a very high surface energy having a contact angle of 10 degrees or less (contaminant adsorption ability) is obtained. ) Having thin film 2)
08.

As described above, according to the present embodiment, the optical element 1
Since the thin film 208 having a very high surface energy (capability of adsorbing contaminants) compared to the optically effective area F was formed around the optically effective area F on the recording medium side surface of the recording medium 09, the recording / reproducing was performed. At times, contaminants (such as moisture, organic matter, and dust in the air) scattered from the recording medium 112 are strongly attracted to the thin film 208 having high surface energy, and are preferentially adsorbed on the thin film 208. For this reason, it is possible to prevent adhesion and deposition of contaminants to the optically effective area F, and as a result, without lowering the optical performance of the optical element 109 due to the contaminants.
An optical pickup 100 (see FIG. 1) that can record and reproduce information stably for a long period of time can be realized.

The present invention is not limited to the configurations of the first to fourth embodiments described above, but can be applied to the following configurations.

For example, as shown in FIG. 6, an optical element 1 having a chamfered portion other than the optically effective area F on the recording medium side surface.
09 or an optical element 10 having a step at a portion other than the optically effective area F on the surface of the recording medium as shown in FIG. 7, for example.
The technical idea of the present invention can also be applied to 9.

Further, as shown in FIG.
There is a case where a transparent protective film 210 is provided on the recording surface 112a, but the technical idea of the present invention is applied even when the thickness of the protective film 210 is different (thick and thin). It is possible.

According to the technical idea of the present invention as described above, the following invention is constituted.

(1) It has a light source, an optical system for focusing laser light from the light source, and an optical element having an effect of increasing the numerical aperture. The optical element is brought into contact with or close to a recording medium. An optical pickup that performs recording and reproduction by using the optical element, wherein a surface of the surface facing the recording medium other than the optically effective region is provided with an adsorbing portion that adsorbs contaminants. Optical pickup.

(2) It has a light source, an optical system for focusing laser light from the light source, and an optical element having an effect of increasing the numerical aperture. The optical element is brought into contact with or close to a recording medium. An optical pickup that performs recording and reproduction by using an optically effective surface of the surface facing the recording medium so that the flow velocity and pressure of the air flow between the optical element and the recording medium are increased. An optical pickup characterized in that a projecting portion projecting toward a recording medium is provided in a region including at least a part of the region.

(3) The optical pickup according to the above (1), wherein the suction section is constituted by a rough surface.

(4) The optical pickup according to the above (1), wherein the suction section is constituted by a plurality of grooves.

(5) The optical pickup according to (3), wherein the rough surface is formed by chemical etching or physical etching.

(6) The optical pickup according to the above (1), wherein the optically effective area has water repellency.

(7) The optical pickup according to the above (1), wherein the adsorbing section is constituted by a thin film made of a metal oxide.

[0066]

According to the present invention, it is possible to provide an optical pickup which can record and reproduce information stably for a long period of time without deteriorating the optical performance of the optical element due to contaminants. .

[Brief description of the drawings]

FIG. 1 is a diagram showing the overall configuration of an optical pickup according to the present invention.

FIG. 2 is a diagram showing a configuration of an optical element applied to the optical pickup according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of an optical element applied to an optical pickup according to a second embodiment of the present invention.

FIG. 4A is a diagram illustrating a configuration of an optical element applied to an optical pickup according to a third embodiment of the present invention;
(B) is a perspective view of an optical element applied to the third embodiment, (c) is a perspective view of an optical element applied to a modification of the third embodiment, and (d) is a third example. FIG. 16 is a perspective view of an optical element applied to another modification of the embodiment.

FIG. 5 is a diagram showing a configuration of an optical element applied to an optical pickup according to a fourth embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of an optical element in which a portion other than an optically effective area on a recording medium side surface is chamfered.

FIG. 7A is a diagram illustrating a configuration of an optical element in which a step is provided in a portion other than an optically effective area on a recording medium side surface,
(B) is a perspective view of an optical element.

FIG. 8 is a diagram showing an example in which the optical pickup of the present invention is applied to a recording medium provided with a transparent protective film.

[Explanation of symbols]

 108 Objective lens 109 Optical element 112 Recording medium 112a Recording surface 200 Suction unit 202 Rough surface F Optically effective area

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H087 KA13 LA01 LA21 LA25 NA17 PA01 PA02 PA17 PB01 PB02 QA02 QA05 QA13 QA14 QA21 QA33 QA41 RA41 5D119 AA11 AA22 AA32 BA01 CA06 DA01 DA05 JA44 MA06 MA10 MA16 9A001 KK03 KK03 H31 KK31 KK34 KK35 KK37 LL02

Claims (2)

[Claims] An optical system includes a light source, an optical system for converging laser light from the light source, and an optical element having an effect of increasing a numerical aperture. The optical element is brought into contact with or close to a recording medium. An optical pickup for performing recording / reproduction, wherein the optical element is provided with an adsorbing portion for adsorbing a contaminant in a region other than an optically effective region on a surface facing the recording medium. Optical pickup. 2. A light source, an optical system for converging laser light from the light source, and an optical element having an effect of increasing a numerical aperture, wherein the optical element is brought into contact with or close to a recording medium. An optical pickup for performing recording and reproduction, wherein the optical element has an optically effective area of a surface facing the recording medium so that a flow velocity and a pressure of an air flow between the optical element and the recording medium are increased. An optical pickup characterized in that a protruding portion protruding in the direction of the recording medium is provided in a region including at least a part of the optical pickup.