JP2006344262A - Solid immersion lens, optical pickup, and optical recording/reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid immersion lens which can stably record or reproduce optical signals with the near-field light without dust sticking to its light condensing section, and also provide an optical pickup and an optical recording/reproducing device. <P>SOLUTION: This solid immersion lens has a section inclining toward the light condensing section, and is configured by forming multiple inclining faces on the above section so that their inclination angles are different from one another. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid immersion lens, an optical pickup device using the same, and an optical (or magneto-optical) recording / reproducing device, and more specifically, using a material having a high refractive index of the optical lens. A solid immersion lens, an optical pickup device, and an optical recording / reproducing apparatus applicable to a so-called near-field optical recording / reproducing system that performs recording / reproducing on an optical (or magneto-optical) recording medium by increasing the numerical aperture of the condenser lens It is about.

Recording media (including magneto-optical recording media) represented by compact disc (CD), mini disc (MD), and digital versatile disc (DVD) are widely used as storage media for music information, video information, data, programs, and the like. It's being used. However, in order to further improve the sound quality, image quality, longer time, and capacity of music information, video information, data, programs, etc., a larger capacity recording medium and an optical recording / reproducing apparatus for recording / reproducing the recording medium (Including a magneto-optical recording / reproducing apparatus) is desired.
Therefore, in order to cope with these, in the optical recording / reproducing apparatus, the wavelength of the light source, for example, the semiconductor laser is shortened, the numerical aperture of the condensing lens is increased, and the light spot converged through the condensing lens is reduced. The diameter has been reduced.

  For example, with regard to semiconductor lasers, GaN semiconductor lasers whose oscillation wavelength has been shortened from the 635 nm to 400 nm bands of conventional red lasers have been put into practical use, and thereby the diameter of the light spot is being reduced. Further, for example, for further shortening of the wavelength, a far ultraviolet solid-state laser UW-1010 manufactured by Sony Corporation that continuously oscillates light having a single wavelength of 266 nm has been put on the market. It is being planned. In addition to this, research and development of a Nd: YAG laser double wave laser (266 nm band), a diamond laser (235 nm band), a GaN laser double wave laser (202 nm band), and the like are underway.

  Further, by using an optical lens having a large numerical aperture represented by a solid immersion lens, for example, a condensing lens having a numerical aperture of 1 or more is realized, and an object surface of the solid immersion lens used for the condensing lens is used as a light source. A so-called near-field optical recording / reproducing system in which recording / reproducing is performed by bringing the recording medium close to about one-tenth of the wavelength has been studied (see, for example, Patent Document 1).

  In this near-field optical recording / reproducing system, it is important to maintain the distance between the recording medium and the solid immersion lens in an optical contact state with high accuracy. In addition, the diameter of the light beam emitted from the light source and incident on the solid immersion lens becomes small, and the distance between the recording medium and the solid immersion lens is very small, about tens of nanometers or less, so the recording medium and the solid immersion lens The so-called tilt margin becomes very small, and the shape of the solid immersion lens is greatly restricted.

  Conventionally, as a solid immersion lens (SIL) considering a tilt margin, those shown in FIGS. 16A and 16B are known. The solid immersion lens shown in FIG. 16A has a structure in which a convex condensing part is provided at the center of the objective surface of the super hemispherical lens, so that the distance between the objective surface excluding the convex part and the recording medium. To increase the tilt margin (Non-patent Document 1). In addition, the solid immersion lens shown in FIG. 16B has a structure in which a conical inclined portion is provided on the objective surface side of the hemispherical lens, so that the distance between the objective surface and the recording medium is increased. The margin is improved (see, for example, Patent Document 2).

When the solid immersion lens having such a configuration is applied to, for example, an optical recording / reproducing apparatus, the solid immersion lens is attached to an optical pickup device having a biaxial actuator, and the distance between the recording medium and the solid immersion lens is optically determined. Keep in contact. When used for magneto-optical recording, a magnetic head device used for magnetic recording / reproducing is incorporated in the optical pickup device, and similarly the distance between the recording medium and the solid immersion lens is maintained in an optical contact state. It is supposed to be configured.
Japanese Laid-Open Patent Publication No. 5-189796 JP 2003-161801 A ISOM'04 Technical Digest pp210-211

  However, in the solid immersion lens of FIG. 16A described above, since the objective surface has a convex portion, when the recording medium rotates, the convex shape located between the objective surface and the recording medium. An air flow is generated around the part. This airflow causes dust floating on the recording medium to enter the gap formed between the tip of the convex portion of the solid immersion lens and the recording medium, and dust is provided near the tip of the convex portion. As a result, there is a problem that stable recording / reproduction becomes difficult by blocking light incident on the lens. In particular, in the near-field optical recording / reproducing method, the distance between the condensing part provided at the tip of the convex part and the recording medium is extremely short (generally 70 nm or less), so this gap is near the surface of the recording medium. There is a problem that minute dust floating in the air is easily caught.

  Similarly, since the solid immersion lens of FIG. 16B described above has a conical inclined portion on the object plane side, when the recording medium rotates, air flows near the tip of the inclined portion. appear. And by this air flow, dust floating on the recording medium is sucked between the tip part of the inclined part and the recording medium and adheres to the vicinity of the light collecting part provided at the tip part of the inclined part. As a result, there arises a problem that it is difficult to stably record and reproduce by blocking light incident on the lens.

  In view of the above-described problems, the present invention provides a solid immersion lens, an optical pickup device, and an optical recording / reproducing device capable of performing stable optical recording / reproduction without dust adhering to the light collecting portion of the solid immersion lens. It is to provide.

  The present invention is a solid immersion lens having an inclined portion that is inclined toward the light collecting portion, wherein the inclined portion is provided with a plurality of inclined surfaces, and the inclined angles of the inclined surfaces are different from each other. .

  Preferably, it is appropriate that the inclination angle of the inclined surface is provided so as to increase as it approaches the light collecting portion.

The present invention is an optical pickup device including at least a light source and a condensing lens composed of a solid immersion lens and an optical lens, wherein the solid immersion lens has an inclined portion inclined toward the condensing portion. The inclined portion is provided with a plurality of inclined surfaces, and the inclined angles of the inclined surfaces are different from each other.
The present invention also includes at least a light collecting lens, a condensing lens composed of a solid immersion lens and an optical lens, an optical pickup device that condenses light on a recording medium and performs recording and / or reproduction, and the collecting device. An optical recording / reproducing apparatus comprising a drive control means for driving and controlling an optical lens and an optical pickup device, wherein the solid immersion lens has an inclined portion inclined toward a condensing portion, The inclined surfaces are provided so that the inclined angles of the inclined surfaces are different from each other.

  In the solid immersion lens according to the present invention, since the inclined portion is provided with a plurality of inclined surfaces, dust attached to the light collecting portion can be reduced, and in the optical pickup device and the optical recording / reproducing device using the same, Recording and reproduction by stable near-field light can be performed.

  According to the solid immersion lens of the present invention, the tilt margin can be increased as compared with the conventional case, and the dust adhering to the light collecting portion can be reduced.

  Further, according to the optical pickup device and the optical reproducing / recording device using the solid immersion lens of the present invention, it is possible to reduce the dust adhering to the condensing part of the solid immersion lens, so that the recording / reproducing by the stable near-field light is possible. Can do.

  Examples of the best mode for carrying out the present invention will be described below, but the present invention is not limited to the following examples.

  FIG. 1 is a schematic configuration diagram showing an example of an optical recording / reproducing apparatus including an optical pickup device according to the present invention.

  As shown in FIG. 1, in this example, an example of a light irradiation mode in the case of recording on a disk-shaped recording medium 9 based on information from the information source 1 is shown, and a light source composed of a laser diode (LD) or the like. The light emitted from 3 is modulated by the information source 1 in response to the information signal, and the output is controlled by the automatic power control means (APC) 2. The emitted light is converted into parallel light by the collimator lens 4 in the optical unit 41 and is incident on the head unit 42 via the beam spiriter 6 and the mirror 7. The head unit 42 includes an optical system that irradiates the recording medium 9 with near-field light by a condensing lens that achieves a numerical aperture of 1 or more, which includes the solid immersion lens 10 and the optical lens 16 including an aspherical lens. Is done. The head unit 42 is configured by installing, for example, the solid immersion lens 10 and the optical lens 16 on the actuator 8 constituting the driving unit 43. The light emitted from the optical unit 41 is irradiated as near-field light onto the recording surface on which information of the recording medium 9 is recorded by the head unit 42. The optical pickup device 47 is configured by a portion surrounded by a dotted line shown in the figure.

  The recording medium 9 is held by a moving mechanism unit 46 including, for example, a rotating unit 15 that rotates and moves the recording medium 9. By the interlocking, the near-field light emitted from the head unit 42 is scanned along, for example, a spiral or concentric recording track along the surface of the recording medium 9.

  The detection mode of the spots arranged in this way will be described with reference to FIG. 1 again. In this case, the light reflected from the recording medium 9 is reflected by the beam splitter 6 through the head unit 42 and detected by the light detection unit 44 including the photodetector (PD) 12. Then, the return light amount detected in this way is input to the gap servo 13, converted from a detected light amount value into a control signal based on a detection method described later, a gap control signal is output, and a drive unit by the actuator 8 43 is input to correct the gap. As a result, the gap between the solid immersion lens 10 and the recording medium 9 is kept constant.

  FIG. 2 is a schematic configuration diagram illustrating an incident mode in which incident light is incident on the recording medium 9 via the head unit 42. The aspherical lens 16 and the solid immersion lens 10 are arranged in this order from the light source side, and the head portion 42 that irradiates the recording medium 9 with near-field light is installed in an actuator 8 such as a biaxial actuator. In the illustrated example, incident light A is incident on the solid immersion lens 10 at an angle at which the incident light is totally reflected. In FIG. 2, an alternate long and short dash line c indicates the optical axis of the incident light. The light that has soaked into the recording medium 9 from the light condensing part 20 on the recording medium side end face of the solid immersion lens 10 forms a spot on the recording medium 9.

  Next, a method for detecting the gap g between the solid immersion lens 10 and the recording medium 9 for the recording medium 9 using near-field light will be described with reference to FIGS. 3A is a schematic configuration diagram showing a gap between the recording medium 9 and the head portion 42, that is, a gap between the recording medium side end surface of the solid immersion lens 10, and FIG. 3B is a total reflection with respect to the gap. It is a figure which shows the change of return light quantity. In FIG. 3A, parts corresponding to those in FIG.

  When the gap between the solid immersion lens 10 and the recording medium 9 is generally greater than or equal to the distance at which near-field light that is ¼ or less of the wavelength of the incident light is generated, that is, as indicated by the dashed arrow Ff in FIG. In the far field region, light incident at an angle causing total reflection at the end face of the solid immersion lens 10 is totally reflected at this end face. Therefore, as shown in FIG. 3B, the return light amount Lr is always constant. It is.

  On the other hand, the gap between the solid immersion lens 10 and the recording medium 9 is approximately ¼ or less (generally, 70 nm or less) of the wavelength λ of incident light, and is equal to or less than the distance at which near-field light is generated. When entering the field light region, a part of the light incident at an angle of total reflection from the light condensing unit 20 of the solid immersion lens 10 begins to permeate, and the return light amount Lr decreases. When the solid immersion lens 10 and the recording medium 9 come into contact with each other (that is, at the position where the gap is 0), all of the incident light is transmitted to the recording medium 9, so that the return light amount Lr becomes zero.

Such a change in the amount of return light in the gap region that generates near-field light occurs in the near-field light region indicated by the broken-line arrow Fn, and the amount of return light gradually decreases as the gap approaches the recording medium from a position of approximately λ / 4. Then, a curve is obtained that decreases substantially linearly in the middle portion and gradually gradually decreases again in a region closer to the recording medium surface.
Therefore, the gap between the solid immersion lens 10 and the recording medium 9 is detected from the return light amount by utilizing the fact that the total reflected return light amount changes substantially linearly within a certain range with respect to the gap length. In the case where the gap is held at a constant value d as shown in FIG. 3B, for example, the actuator 8 or the like is controlled by the gap control unit so that the return light amount Lr is held at the target value α corresponding to the gap. By driving, the gap between the solid immersion lens 10 and the recording medium 9 can be controlled to be constant, for example, 20 nm.

  Next, an example in which the present invention is applied to a playback system of a recording / playback apparatus will be described. FIG. 4 shows a schematic configuration diagram of a reproducing apparatus when spots are formed on a recording medium 9 using a light source 3 such as one laser. 4, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  In this case, the reproduction RF signal can be detected by receiving the return light amount by the photodetector 12. Further, the servo signal can be detected by observing the reproduction RF signal through a low-pass filter, and an error signal to the gap servo 13 can be obtained. As a result, stable gap control can be performed and good reproduction can be performed.

  FIG. 5A is a schematic diagram illustrating a path when the dust D entering the solid immersion lens is wound up by an air flow generated by the rotation of the recording medium. FIG. 5B is a plan view used for explaining the entering direction of the dust D when entering the solid immersion lens.

  First, dust D emitted from a position of X = −100 μm on the X axis starts to enter toward the center point x of the solid immersion lens 10 along the X axis. Next, when the dust D approaches the center point x of the solid immersion lens 10 to a certain position, the air flow generated in the space between the recording medium 9 and the inclined surface 11 of the solid immersion lens 10 due to the rotation of the recording medium 9. The recording medium 9 is wound up under the influence of the above. At this time, the length of the perpendicular line segment between the recording medium 9 and the inclined surface 11 of the solid immersion lens 10 at the position where the dust D is closest to the center point x of the solid immersion lens 10 on the X-axis. , L1. In addition, the inclination angle of the inclined surface 11 of the solid immersion lens 10 is defined as an inclination angle θ, which is defined as an angle generated by the intersection of the optical axis c and the cross-sectional line of the inclined surface 11.

Next, the principle of dust D being rolled up on the recording medium will be described in detail with reference to FIG.
FIG. 6A is a schematic cross-sectional view showing the positional relationship between the solid immersion lens and the recording medium.
At this time, a space formed between the inclined surface 11 of the solid immersion lens 10 and the recording medium 9 is S, and the dust D entering the central portion x of the solid immersion lens 10 along the surface of the recording medium 9 is defined as S. Let the approach speed be v.

  First, the dust D advances toward the center of the solid immersion lens 10 along the surface of the recording medium 9 at an approach speed v. On the other hand, as the recording medium 9 rotates, an air flow f indicated by an arrow flowing upward along the inclined surface 11 of the solid immersion lens 10 is generated in the air existing in the space S. Therefore, when the dust D that has progressed toward the center x of the solid immersion lens 10 at the approach speed v approaches the center x of the solid immersion lens 10 to some extent, it is affected by the air flow f and is above the recording medium 9. Rolled up.

FIG. 7 is a diagram showing the relationship between the tilt angle of the solid immersion lens and the lens-disk distance L1.
FIG. 7 shows a result when the above-described L1 is measured by changing the inclination angle θ of the inclined surface 11 provided in the solid immersion lens 10. The vertical axis in FIG. 7 represents L1 (Disk-SIL Gap) defined above, and the horizontal axis represents a value obtained by subtracting the inclination angle θ of the inclined surface from 90 degrees (90 ° −θ). That is, as the horizontal axis increases, the inclination angle θ of the inclined surface 11 decreases. Here, the linear velocity of the recording medium 9 is set to 6.3 m / s, the emission position of the dust D is set to a height of 10 nm from the surface of the recording medium 9, and the diameter of the dust D is 20 nm. Further, the entry position of the dust D with respect to the center part x of the solid immersion lens is set to a position of y = 0 on the Y axis shown in FIG.

  As is apparent from the results shown in FIG. 7, when the horizontal axis (90 ° −θ) is 10 degrees, that is, when the inclination angle θ of the inclined surface 11 of the solid immersion lens 10 is 80 degrees, the solid immersion lens. The dust D entering the central portion x of 10 is wound up above the recording medium 9 when reaching a position where L1 is 140 nm. That is, the dust D is rolled up above the recording medium before entering the light collecting unit 20 of the solid immersion lens 10.

  On the other hand, when the horizontal axis (90 ° -θ) is 10 degrees or less, that is, when the inclination angle θ of the inclined surface 11 is 80 degrees or more, and when the horizontal axis (90 ° -θ) is 20 degrees or more, that is, the inclination. When the inclination angle θ of the surface 11 is 70 degrees or less, the entering dust D is not wound up above the recording medium. In particular, when the horizontal axis (90 ° −θ) is 20 degrees or more, L1 on the vertical axis is 20 nm, that is, the same value as the diameter of the dust D, so that the dust D is wound up from the surface of the recording medium 9. Without entering, the center part x of the solid immersion lens 10 is entered as it is. As a result, the dust D is sandwiched between the condensing unit 20 of the solid immersion lens 10 and the recording medium 9 and adheres to the condensing unit 20 of the solid immersion lens 10.

Next, the results shown in FIG. 7 will be considered with reference to FIG.
FIG. 8C is a diagram for explaining the results when the horizontal axis (90 ° −θ) is 10 degrees, that is, when the inclination angle θ of the inclined surface 11 of the solid immersion lens is 80 degrees.
The velocity distribution of the air flow f generated between the recording medium 9 and the solid immersion lens 10 is based on the force for accelerating the air due to the movement of the recording medium 9 and the air caused by the stationary solid immersion lens 10 to be stationary. Power, inertial force of the air flow itself, and static pressure difference.

Here, the static pressure increases as the distance between the solid immersion lens 10 and the recording medium 9 decreases. For example, the solid immersion lens 10, if it has an inclined surface 11 as shown in FIG. 8 (a) ~ (c) , the static pressure _{p 2} positions _{x 2} on the recording medium, the position _{x 1} static pressure greater than p _1, it causes a reduction of air flow. Further, the static pressure difference between the position x ₁ and the position x _2, the angle (90 ° -θ) increases, i.e., the larger the inclination angle θ decreases.

FIG. 8 (c), the velocity distribution of the airflow f at position x ₁ is shown schematically by the arrows. Assuming that the velocity direction toward the center of the solid immersion lens 10 is positive, the velocity distribution of the air flow becomes a positive velocity distribution due to the movement of the recording medium 9 near the recording medium 9, but as the distance from the recording medium 9 increases, the velocity increases. reduced by static pressure difference, the direction of the velocity at height h _alpha is a negative velocity distribution reversed. The range having the negative velocity distribution corresponds to a region where the dust D is wound up by the air flow f as shown in FIG. Further, when approaching the solid immersion lens 10 that is stationary at a position distant from the recording medium, the negative speed decreases and becomes zero at the solid immersion lens surface 11. Accordingly, at a position where the boundary height h _{α at} which the air flow that winds up the dust D is generated is lower than the height of the dust D, the dust D is located above the recording medium 9 before entering the central portion x of the solid immersion lens. It is thought that it is rolled up.

FIG. 8B is a diagram for explaining a result when the horizontal axis (90 ° −θ) is 20 degrees or more, that is, when the inclination angle θ of the inclined surface 11 of the solid immersion lens is 70 degrees or less.
In this case, when compared 8 and (c), the angle (90 ° -θ) increases, static pressure difference position _{x 1} and the position _{x 2} is increased. However, when the height h _{α at} which the direction of the velocity distribution of the air flow at the position x ₁ is reversed is compared, the height h _α is higher than the distance h ₀ between the recording medium 9 and the solid immersion lens central portion x. Become. Therefore, the dust D of the recording medium 9 near the surface until it enters the position x ₂ closer to the center x of the solid immersion lens, without being rolled up from the recording medium 9, as to near the center portion x of the solid immersion lens The possibility of entering is considered high.

FIG. 8A is a diagram for explaining the results when the horizontal axis (90 ° −θ) is 10 degrees or less, that is, when the inclination angle θ of the inclined surface 11 of the solid immersion lens is 80 degrees or more.
In this case, when compared with FIG. 8 (c), the angle (90 ° -θ) is reduced, since the static pressure difference position x ₁ and the position x ₂ is smaller, it does not occur reversed itself velocity distribution of the air flow , D is considered to enter the central portion x of the solid immersion lens 10.

FIG. 9A is a schematic diagram showing dust D wound up on the recording medium 9. FIG. 9B is a plan view used for explaining the direction in which the dust D enters the solid immersion lens.
In FIG. 9, parts corresponding to those in FIG. The dust D enters the X axis shown in FIG. 9B toward the center point x of the solid immersion lens 10, but the air generated between the inclined surface 11 of the solid immersion lens 10 and the recording medium 9. The recording medium 9 is wound up by the flow f. Here, the distance between the center of the dust D wound up on the recording medium 9 and the surface of the recording medium 9 is defined as L2.

FIG. 10 is a diagram showing the relationship between the inclination angle of the solid immersion lens and the dust-disk distance L2.
FIG. 10 shows the result of measuring L2 by changing the inclination angle θ of the inclined surface 11 provided on the solid immersion lens 10. The vertical axis in the figure indicates L2 defined in FIG. 9A, and the horizontal axis indicates a value obtained by subtracting the inclination angle θ of the inclined surface 11 of the solid immersion lens 10 from 90 degrees (90 ° −θ). Here, the linear velocity of the recording medium 9 is set to 6.3 m / s, the emission position of the dust D is set to a height of 50 nm from the surface of the recording medium 9, and the diameter of the dust D is set to 100 nm. Further, the entry position of the dust D with respect to the center part x of the solid immersion lens is set to a position of y = 0 on the Y axis shown in FIG.

  From the results shown in FIG. 10, the dust D that has entered the center x of the solid immersion lens 10 is rolled up on the recording medium 9 as the inclination angle θ of the inclined surface 11 provided on the solid immersion lens 10 decreases. I understand that

FIG. 11 is a diagram showing the relationship between the inclination angle of the solid immersion lens and the dust-disk distance L2 by changing the diameter of the dust D in FIG.
In FIG. 11, L2 is measured by changing the inclination angle θ provided in the solid immersion lens 10. The vertical axis represents L2 defined in FIG. 9A, and the horizontal axis represents a value (90 ° −θ) obtained by subtracting the angle θ provided in the inclined portion 11 of the solid immersion lens 10 from 90 degrees. Yes. Here, the linear velocity of the recording medium 9 is set to 6.3 m / s, the emission position of the dust D is set to a height of 100 nm from the surface of the recording medium 9, and the diameter of the dust D is set to 200 nm. Further, the entry position of the dust D with respect to the center part x of the solid immersion lens is set to a position of y = 0 on the Y axis shown in FIG.

  As is apparent from the results shown in FIG. 11, the dust D that has entered the center of the solid immersion lens 10 is recorded on the recording medium 9 as the inclination angle θ of the inclined surface 11 provided on the solid immersion lens 10 decreases. It can be seen that it can be rolled up high.

  From the results shown in FIGS. 10 and 11, in the case of dust D floating at some distance from the surface of the recording medium 9, the smaller the inclination angle θ of the inclined surface 11 of the solid immersion lens 10, It can be seen that soars high. As a result, the possibility of dust D adhering to the light collecting portion 20 of the solid immersion lens 10 is reduced. This is because the volume of air existing in the space S formed between the recording medium 9 and the solid immersion lens 10 increases as the inclination angle θ of the inclined surface portion 11 of the solid immersion lens 10 decreases, that is, the amount of fluid. This is because the air flow f becomes stronger in proportion to the dust D and the dust D floating at a certain distance from the surface of the recording medium 9 is considered to be wound up to a higher position.

  From the above consideration, the solid immersion lens used when using near-field light is both dust D floating at a position close to the surface of the recording medium 9 and dust D floating at a position far from the surface of the recording medium 9. It can be understood that the inclination angle θ provided on the inclined surface 11 of the solid immersion lens 10 needs to be determined in consideration of the above.

Next, the shape of the solid immersion lens of the present invention based on the above consideration will be described.
FIG. 12A is a cross-sectional view of an example of a solid immersion lens according to the present invention. FIG. 12B is a plan view for facilitating understanding of the shape of the solid immersion lens.

  The solid immersion lens 10 in this example includes a spherical portion 31 and a convex portion 32. The spherical portion 31 is formed to have a super hemispherical shape. The convex portion 32 is connected to the spherical portion 31 so as to have a conical shape. A condensing part 20 is provided at the tip of the convex part 32, and an object surface having a flat surface facing the recording medium 9 is formed on the condensing part 20. The convex portion 32 is provided with an inclined surface 11 that is inclined toward the light collecting portion 20 as an inclined portion. Further, the inclined surface 11 is formed with a first inclined surface 11α and a second inclined surface 11β having different inclination angles θ.

FIG. 13 is an enlarged view of the vicinity of the light condensing part of the solid immersion lens shown in FIG.
A first inclined surface 11α is formed on the inclined surface 11 of the lens so as to be connected to the condensing unit 20, and a second inclined surface 11β is formed so as to be connected to the first inclined surface 11α. The first inclined surface 11α has an inclination angle θα, and the second inclined surface 11β has an inclination angle θβ.
In the solid immersion lens 10 of this example, the inclination angle θα of the first inclined surface 11α is formed to be larger than the inclination angle θβ of the second inclined surface 11β. Further, based on the result shown in FIG. 7, the inclination angle θα of the first inclined surface 11α is formed to be about 80 degrees. Here, the inclination angle θ provided on the inclined surface means an angle formed by intersecting a line parallel to the optical axis c and a cross-sectional line of the inclined surface.

  As described above, according to the solid immersion lens 10 of the present example, the inclined surface 11 of the convex portion 32 is formed with the plurality of inclined surfaces 11α and 11β having different inclination angles θ. The dust D floating at a position away from the surface of the recording medium 9 can be rolled up on the recording medium at the portion of the second inclined surface 11β having a small inclination angle θ, and then near the surface of the recording medium 9 and in the near field. The dust D floating in the range where light is generated can be wound up at the portion of the first inclined surface 11α having a large inclination angle θ provided near the light collecting unit 20. That is, the dust that enters the center of the solid immersion lens 10 can be removed stepwise by setting the inclination angle of the inclined surface 11 to two steps in this way. For this reason, since dust can be removed efficiently, the dust resistance of the solid immersion lens 10 can be improved.

  Further, the near-field light is used by forming each inclination angle θ of the plurality of inclined surfaces provided on the inclined surface 11 so as to increase as it approaches the condensing unit 20 of the solid immersion lens 10. Even if it is a case, the dust which approachs can be removed exactly and the dust resistance of the solid immersion lens 10 can be improved.

  Further, according to the optical pickup device using the solid immersion lens 10 of the present example, the possibility of dust D being sandwiched between the solid immersion lens 10 and the recording medium 9 is reduced. Even in such a case, a stable light pickup operation can be performed. Further, according to the optical recording / reproducing apparatus using the solid immersion lens 10 of the present example, the possibility of dust D being sandwiched between the solid immersion lens 10 and the recording medium 9 is reduced, so that near-field light is used. Even so, it is possible to perform a stable recording / reproducing operation in which the gap servo does not fail.

FIG. 14 is a sectional view showing another embodiment of the solid immersion lens according to the present invention.
A first inclined surface 11α is formed on the inclined surface 11 of the convex portion 32 of the solid immersion lens 10 so as to be connected to the condensing portion 20, and the second inclined surface 11β is connected to the first inclined surface 11α. Is formed. Further, a third inclined surface 11γ is formed in connection with the second inclined surface 11β, and a fourth inclined surface 11δ is formed in connection with the third inclined surface 11γ. The inclined surfaces 11α, 11β, 11γ, and 11δ have inclination angles θα, θβ, θγ, and θδ, respectively, and the inclined surfaces are formed so that the inclination angles satisfy θα>θβ>θγ> θδ. Note that the number of inclined surfaces formed in the inclined portion 11 is not limited to the number of inclined surfaces in this example as long as the inclination angle increases as the light collecting portion 20 is approached. Further, by forming the inclined surface 11 of the inclined surface 11 provided on the convex portion 32 in such a manner that the inclination angle θ is gradually changed, the operation of forming the inclined surface on the solid immersion lens 10 can be facilitated. .

FIG. 15 is a cross-sectional view when the solid immersion lens shown in FIG. 12 is set on a recording medium.
In FIG. 15, parts corresponding to those in FIG. In the solid immersion lens 10 of this example, the distance L3 from the recording medium 9 at the boundary between the first inclined surface 11α and the second inclined surface 11β is set to be approximately 50 nm or less. That is, on the second inclined surface 11β of the solid immersion lens 10, the distance from the second inclined surface 11β to the surface of the recording medium 9 is set to be 50 nm or more.

  In addition, the shape of the convex part 32 of the solid immersion lens 10 mentioned above is not restricted to a cone shape, It is good also as a pyramid shape. In addition, the inclination angle of the inclined surface 11 provided on the convex portion 32 is set to an angle that does not interfere with the incident light of the laser incident on the lens. In the near-field optical recording / reproducing system for the magneto-optical recording medium, a magnetic field is required at the time of recording and / or reproduction. Therefore, a magnetic coil or the like is attached to a part of the objective surface of the solid immersion lens or its periphery. It may be configured.

In addition, as described above, the material of the solid immersion lens has a large refractive index, a large transmittance, and a small light absorption with respect to the wavelength of the laser light source equipped in the optical recording / reproducing apparatus and optical pickup apparatus to be used. Those are suitable as materials. For example, S-LAH79 (trade name) manufactured by OHARA INC. Which is a high refractive index glass, Bi ₄ Ge ₃ O ₁₂ , SrTiO ₃ , ZrO ₂ , which is a high refractive index ceramic, a high refractive index single crystal material, HfO ₂ , SiC, KTaO ₃ , diamond and the like are preferable.

  Further, it is desirable that these lens materials have an amorphous structure or a cubic structure in the case of a single crystal. In the case where the lens material has an amorphous structure or a cubic structure, the etching rate and etching characteristics do not change depending on the crystal orientation, so that it is possible to use a known etching method or apparatus used for processing a semiconductor or the like.

  Furthermore, for the processing of the flat portion of the objective surface provided at the tip of the convex portion such as the cone shape of the solid immersion lens, known etching methods and apparatuses used for semiconductor processing can be used, For processing the tip, it is preferable to use a focused ion beam processing method and processing apparatus such as a focused ion beam processing observation apparatus FB-2100 (trade name) manufactured by Hitachi, Ltd., for example. Further, a solid immersion lens may be formed by cutting and polishing the ball lens.

FIG. 1 is a schematic configuration diagram of an example of an optical recording / reproducing apparatus including an optical pickup device according to the present invention. FIG. 2 is a schematic configuration diagram showing a light incident mode on a recording medium in the optical pickup device according to the present invention. FIG. 3A is a schematic configuration diagram showing a gap between a recording medium and a head portion of an optical pickup device using near-field light. FIG. 3B is a diagram showing the relationship between the gap and the return light amount in the recording medium of the optical pickup device using near-field light. FIG. 4 is a schematic configuration diagram of an example of an optical recording / reproducing apparatus including the optical pickup device according to the present invention. FIG. 5A is a schematic diagram showing a path when the dust D moves on the recording medium by an air flow. FIG. 5B is a plan view of the solid immersion lens used for explaining the direction in which the dust D enters the solid immersion lens. FIG. 6A is a schematic cross-sectional view of the solid immersion lens and the recording medium used for explaining the air flow generated between the recording medium and the solid immersion lens. FIG. 6B shows the relationship between the distance h between the recording medium 9 and the inclined surface 11 of the solid immersion lens and the approach speed v. FIG. 7 is a diagram showing the relationship between the tilt angle of the solid immersion lens and the lens-disk distance L1. FIG. 8A is a diagram for explaining the results when the horizontal axis (90 ° −θ) is 10 degrees or less, that is, when the inclination angle θ of the solid immersion lens 10 is 80 degrees or more. FIG. 8B is a diagram for explaining the results when the horizontal axis (90 ° −θ) is 20 degrees or more, that is, when the inclination angle θ of the solid immersion lens is 70 degrees or less. FIG. 8C is a diagram for explaining the results when the horizontal axis (90 ° −θ) is 10 degrees, that is, when the inclination angle θ of the solid immersion lens is 80 degrees. FIG. 9A is a schematic diagram showing a state of dust D floating between the solid immersion lens and the recording medium. FIG. 9B is a plan view used for explaining the direction in which the dust D enters the solid immersion lens. FIG. 10 is a diagram showing the relationship between the inclination angle of the solid immersion lens and the dust-disk distance L2. FIG. 11 is a diagram showing the relationship between the inclination angle of the solid immersion lens and the dust-disk distance L2 by changing the diameter of the dust D in FIG. FIG. 12 is a cross-sectional view showing an example of a solid immersion lens according to the present invention. FIG. 13 is an enlarged cross-sectional view of the vicinity of the light condensing part of the solid immersion lens shown in FIG. FIG. 14 is a cross-sectional view showing another example of the solid immersion lens according to the present invention. FIG. 15 is an enlarged view of the vicinity of the first inclined surface provided in the solid immersion lens according to the present invention. 16A and 16B are cross-sectional views of a conventional solid immersion lens.

Explanation of symbols

  9 .. Recording medium (disc), 10.. Solid immersion lens (SIL), 11.. Inclined portion, 11 α... First inclined surface, 11 β. 31 ..Spherical part, 32 ..Convex part, 43 ..Drive part, 44 ..Light detection part, 45 ..Control part, 47 ..Optical pickup device, .theta ... tilt angle, L1. Lens distance, L2 ... disc-dust distance, c ... optical axis, S ... space, v ... entry speed, D ... dust

Claims (4)

A solid immersion lens having an inclined part inclined toward the light collecting part,
A solid immersion lens, wherein the inclined portion is provided with a plurality of inclined surfaces, and the inclined angles of the inclined surfaces are different from each other. 2. The solid immersion lens according to claim 1, wherein an inclination angle of the inclined surface is provided so as to increase as it approaches the light condensing unit. An optical pickup device comprising at least a light source and a condenser lens composed of a solid immersion lens and an optical lens;
The solid immersion lens has an inclined portion that is inclined toward the condensing portion. The inclined portion is provided with a plurality of inclined surfaces, and the inclined angles of the inclined surfaces are different from each other. Pickup device. At least a light source, a condensing lens composed of a solid immersion lens and an optical lens, an optical pickup device for condensing and recording light on a recording medium, and the condensing lens and the optical pickup device An optical recording / reproducing apparatus comprising drive control means for driving and controlling
The solid immersion lens has an inclined portion inclined toward the condensing portion, and the inclined portion is provided with a plurality of inclined surfaces, and the inclined angles of the inclined surfaces are different from each other. Recording / playback device.

Images