JP5864308B2 - Optical disc apparatus, gap servo apparatus, and gap pull-in control method - Google Patents

Description

  The present invention relates to a technology of an optical disk device, and particularly to an optical disk having a thickness of 1.2 mm and a flexible thin optical disk (FOD: Flexible Optical Disk) (hereinafter collectively referred to as “optical disk”). An optical disk apparatus using a solid immersion lens (SIL) having a numerical aperture (NA) of 1 or more as an objective lens, and a gap pull-in control of the objective lens necessary for recording and / or reproduction in the optical disk apparatus The present invention relates to a gap servo device to be performed and a gap pull-in control method thereof.

  At present, an optical disc apparatus using a laser beam having a wavelength of about 405 nm and an objective lens having a numerical aperture (NA) of 0.85 is commercialized, and this recording medium is known as a Blu-ray disc (BD). The data capacity of the Blu-ray Disc (BD) format is 25 GB.

  In order to increase the recording density, an increase in the numerical aperture (NA) of an objective lens in an optical disc apparatus is being studied as a recording method for an optical disc having a larger capacity and a higher transfer rate.

  For this reason, as a technique for achieving a numerical aperture (NA) larger than 1, an evanescent wave, that is, a recording / reproducing method using near-field light that exponentially attenuates from an interface (“near-field optical recording (NFR: NFR: Also referred to as “Near Field Optical Recording” playback method ”(see, for example, Patent Documents 1 and 2).

  In these patent documents 1 and 2, an objective optical lens and a solid immersion lens (SIL) are combined to form an objective lens of a near-field optical system, and information is recorded and reproduced by irradiating an optical disk with near-field light. A near-field optical disk device for performing the above is disclosed.

  In addition, the gap error amount of the SIL optical head with respect to the optical disk is improved by performing feedforward control (FFC) for adjusting the tangential tilt (TT) and radial tilt (RT) of the SIL optical head in the near-field optical disk apparatus. The technique which performs is known (for example, refer patent document 3).

  In addition, a technique related to feed-forward control (FFC) for realizing high-precision tracking control in tracking servo or focus servo of an optical head in an optical disc apparatus is known (for example, see Patent Document 4).

  As described above, an optical disk apparatus using near-field light requires high-precision servo technology, which is caused by tangential tilt (TT) and radial tilt (RT) adjustment, optical disk eccentric disturbance, and surface vibration disturbance. Feed forward control (FFC) is used to suppress disturbances generated in particular (particularly harmonic component disturbances).

  Also, it is disclosed that it is effective to apply feedforward control (FFC) in the pull-in control of the gap servo (see, for example, Non-Patent Document 1).

  By the way, a gap error signal (GES: Gap Error Signal) of a gap servo by bringing a solid immersion lens (SIL) close to a certain medium is larger than a refractive index value of air = 1 (for example, general) N = 1.5 for a simple quartz glass) and a light source wavelength λ (here, assuming a blue-violet semiconductor laser capable of high-density recording, λ = about 405 nm), the distance is close to λ / 4 or less, When the radial tilt (RT) and tangential tilt (TT) are set to the optimum angles and the optical axis of the solid immersion lens (SIL) is perpendicular to the medium, the amount of reflected light returns linearly according to the approaching distance. The property is known (for example, refer to Patent Document 3).

  On the other hand, in the thin optical disk, when the fixed disk stabilizer is brought close to the thin optical disk rotating at about 4000 rpm so that the distance is about 0.1 mm, the entire surface of the thin optical disk sticks to the surface of the stabilization plate (stabilizer). In addition, it is known to rotate at a low surface runout of 10 μm or less while maintaining a predetermined clearance (see, for example, Patent Document 5 and Non-Patent Document 2).

Japanese Patent No. 2553275 JP 2007-2931979 A JP 2009-70466 A JP 2011-34649 A JP 2007-80336 A

D. Koide et al., “High-Speed Precise Gap Servo System for Near-Field Optical Recording”, International Symposium on Optical Memory and Optical Data Storage (ISOM / ODS), July 17, 2011, Near-field / Plasmonics (2011 ), page OTuA3 D. Koide et al., “High-Speed Recording up to 15,000 rpm Using Thin Optical Disks”, Japanese Journal of Applied Physics, July 18, 2008, vol. 47, No. 7, pp. 58225827

  By the way, in the pull-in control of the gap servo of the near-field optical disk device using the thin optical disk by the solid immersion lens (SIL), the optical disk is brought closer to the solid immersion lens (SIL) that collects the laser beam from the light source. By making the distance between the SIL optical head and the SIL optical head close to 15 mm to 50 nm, the laser light propagates to the optical disk side by evanescent coupling, and the gap servo pull-in control is performed. However, the pull-in control, which was easily possible with a conventional optical disk using 1.2 mm-thick polycarbonate as a substrate material, becomes difficult with a thin optical disk of 0.1 mm to 0.4 mm.

  This is because an objective lens equipped with a solid immersion lens (SIL) has an angle of radial tilt (RT) and tangential tilt (TT) when irradiating a thin optical disc with a laser beam, which is a conventional Blu-ray disc (BD). This is because the numerical aperture (NA) of the objective lens as can be seen is more sensitive than far field recording (FFR), which is a condensing recording system with 1 or less.

  This problem will be described more specifically. Until now, when performing near-field optical recording on a 1.2 mm thick optical disk, pull-in control after adjustment of radial tilt (RT) and tangential tilt (TT) has been performed by one of the following control methods: .

  In the first control method, when the optical disk is stationary before rotating, the solid immersion lens (SIL) on which the laser beam is incident is once brought close to the optical disk, and the radial tilt (RT) and tangential tilt (TT) are set at optimum positions. Thereafter, pull-in control of the gap servo was performed, and thereafter, the optical disk was rotated and held and controlled.

  In the second control method, when the optical disk is stationary before rotating, the solid immersion lens (SIL) on which the laser light is incident is brought closer to the optical disk and the radial tilt (RT) and tangential tilt (TT) are set to the optimum positions. Thereafter, after the optical disk is rotated, the operation is easily realized by performing the pull-in control of the gap servo in the same manner as the focus pull-in control of normal far field recording (FFR).

  In both of the above control methods, when the optical disk is stationary before rotating, the solid immersion lens (SIL) on which the laser beam is incident is brought closer to the optical disk and the radial tilt (RT) and tangential tilt (TT) are optimally positioned. Is set to

  However, since the thin optical disk (FOD) has flexibility, the disk itself hangs down by its own weight when the disk is stationary, and before the gap servo pull-in operation, radial tilt (RT) and tangential tilt (TT). Cannot be set, and there is a problem that pull-in control of the gap servo becomes difficult.

  The object of the present invention has been made in view of the above-mentioned problems, and even when a thin optical disk is used, the radial tilt (RT) and tangential tilt (TT) are adjusted with high accuracy and the pull-in control is performed. Of an optical disk apparatus using a solid immersion lens (SIL) having a numerical aperture (NA) of 1 or more as an objective lens for a thin optical disk, and an objective lens necessary for recording and / or reproduction in the optical disk apparatus It is an object of the present invention to provide a gap servo apparatus that performs gap pull-in control and a gap pull-in control method thereof.

  An optical disc apparatus of the present invention is an optical disc apparatus using a solid immersion lens (SIL) having a numerical aperture of 1 or more as an objective lens for a thin optical disc, the stabilizing plate for stably rotating the thin optical disc, A spindle motor for rotationally driving a thin optical disk at a predetermined rotational speed, a SIL optical head for fixing an objective lens, a tilt actuator for adjusting a tilt amount of the SIL optical head with respect to the thin optical disk, and the SIL light A gap actuator that controls a gap between the head and the thin optical disc, a tilt amount adjustment operation by the tilt actuator, and a control unit that controls a gap pull-in operation by the gap actuator, At the time of initial setting before recording and reproduction, the SIL is applied to the stabilizing plate. It adjusts the tilt of the head, at the time of recording and reproduction, and controlling to perform pull gap based on the amount of tilt was These adjustments to the thin optical disk.

  In the optical disk apparatus of the present invention, the control unit includes means for performing control so as to readjust the adjusted tilt amount within a predetermined allowable range during recording and reproduction.

  In the optical disc apparatus according to the present invention, the control unit may stably rotate the thin optical disc in which the stabilization plate is set in advance without loading the thin optical disc in the tray of the optical disc device at the initial setting before recording and reproduction. And a means for controlling to adjust the tilt amount of the SIL optical head with respect to the stabilizing plate.

  In the optical disk apparatus of the present invention, the control unit records the number of rotations of the thin optical disk at which the thin optical disk is stably rotated after the stabilization plate is set at a predetermined position where the thin optical disk is stably rotated. Rotation is performed as the number of rotations during reproduction, and control is performed so that the gap is drawn into the thin optical disk based on the adjusted tilt amount.

  Furthermore, the gap servo apparatus of the present invention is a gap servo apparatus that performs gap pull-in control in an optical disk apparatus using a solid immersion lens (SIL) having a numerical aperture of 1 or more for a thin optical disk as an objective lens, and performs recording / reproduction. Means for adjusting the tilt amount of the SIL optical head for fixing the objective lens to the stabilizing plate for stably rotating the thin optical disk at the time of the initial setting, and the adjusted tilt amount at the time of recording and reproduction; And a means for controlling to retract the gap with respect to the thin optical disk.

  Further, the gap pull-in control method of the present invention is a gap pull-in control method in an optical disc apparatus using a solid immersion lens (SIL) having a numerical aperture of 1 or more for a thin optical disc as an objective lens. Adjusting the tilt amount of a SIL optical head that fixes the objective lens to a stabilizing plate for stably rotating the thin optical disc at the time of setting, and at the time of recording and reproducing, based on the adjusted tilt amount And a step of performing control so as to perform gap drawing with respect to the thin optical disk.

  According to the present invention, in the initial setting, the SIL optical head with the solid immersion lens (SIL) fixed is brought close to the stabilization plate, and the radial tilt (RT) and the tangential tilt (TT) are adjusted and set. In addition, the gap servo pull-in control operation in the near-field optical recording on the thin optical disk can be easily performed, and the gap servo pull-in control operation can be made highly accurate.

  As a result, high-density recording on a thin optical disk can be performed. In other words, the thin optical disk can be easily operated by a solid immersion lens (SIL) using near-field light with improved data recording capacity and recording transfer rate on the thin optical disk, and stable data recording and / or reproduction is possible. It becomes.

1 is a schematic diagram of an optical disc apparatus according to an embodiment of the present invention. (A), (B) is explanatory drawing of the gap adjustment direction, the tangential tilt adjustment direction, and the radial tilt adjustment direction in the optical disc apparatus of one Embodiment concerning this invention. It is the schematic of the control part which functions as a gap servo apparatus in the optical disc apparatus of one Embodiment which concerns on this invention. It is a flowchart explaining control of the recording / reproducing control management part in the optical disc apparatus of one Embodiment which concerns on this invention. It is a flowchart which shows one Example of the gap drawing-in control method in the optical disc apparatus of one Embodiment which concerns on this invention. (A) and (B) respectively show the angle-dependent characteristics due to the tilt in the tangential direction and the angle-dependent characteristics due to the tilt in the radial direction of the gap error signal (GES) in the objective lens 5 equipped with the solid immersion lens (SIL). FIG. It is a figure which shows the experimental result of gap servo pull-in control operation determination based on the gap pull-in control method in the optical disc apparatus of one Embodiment concerning this invention.

  Hereinafter, an optical disk apparatus according to an embodiment of the present invention, a gap servo apparatus that performs gap pull-in control of an objective lens necessary for recording and / or reproduction in the optical disk apparatus, and a gap pull-in control method thereof will be described.

[Optical disk device]
FIG. 1 is a schematic diagram of an optical disc apparatus 1 according to an embodiment of the present invention. In this example, a solid immersion lens (SIL) having a numerical aperture (NA) of 1 or more with respect to the thin optical disk (FOD) 2 is used for the objective lens 5. Such an objective lens 5 can be realized as a condensing optical lens in which an objective optical lens made up of an aspherical lens or the like and a hemispherical or super hemispherical solid immersion lens (SIL) are combined. It can also be configured as a condensing optical lens integrated with a solid immersion lens (SIL). The objective lens 5 is fixed to the SIL optical head 6.

The optical disc apparatus 1 fixes a mounting portion 3 to which a thin optical disc (FOD) 2 is mounted, a spindle motor 4 that rotationally drives the mounting portion 3 based on a rotation center O and a rotation axis as a rotation axis, and an objective lens 5. SIL optical head 6, gap actuator 7, folding mirror 8, beam splitter 9, collimator lens 10, light source 11 such as a laser diode, and condensing lens 12 disposed on the branch optical path of beam splitter 4 , 4 divided light detector 13 such as a photodiode, a rotation control signal by calculating the detection signal s from the light detecting unit 13 controls the rotational driving of the pull-in control signal C _G and the spindle motor 4 to control the gap actuator 7 and a control unit 14 for generating the C _R. However, these components can have various configurations as long as the functions of the optical disc apparatus 1 operate satisfactorily. For example, the folding mirror 8 can be omitted.

The optical disc apparatus 1 further includes a radial tilt actuator 18 for adjusting the radial tilt (RT) and a tangential tilt actuator 19 for adjusting the tangential tilt (TT). It has a function of generating a tangential tilt control signal C _TT for controlling the radial tilt control signal C _RT and tangential tilt actuator 19 for controlling the tilt actuator 18.

  2A and 2B are explanatory diagrams of the gap adjustment direction, the tangential tilt adjustment direction, and the radial tilt adjustment direction in the optical disc apparatus 1 according to the embodiment of the present invention. For the SIL optical head 6 with the objective lens 5 using a solid immersion lens (SIL) fixed, the gap adjustment direction is the Z-axis direction, the tangential tilt adjustment direction is the Y-axis direction, and the radial tilt adjustment direction is X Axial direction.

The optical disk device 1 also includes a disk loading actuator 20 that controls loading of a thin optical disk (FOD) 2 into a predetermined tray (not shown) in the optical disk device 1. The control unit 14 includes a disk loading actuator. It has a function of generating a disc loading control signal C _D for controlling 20.

Further, the optical disc apparatus 1 includes a stabilization plate (stabilizer) by a stabilization plate (stabilizer) 21 for stabilizing the rotation of the thin optical disc (FOD) 2 and a fixed shaft portion 22 of the stabilization plate (stabilizer) 21. 21 and a stabilizing plate actuator 23 to be movable in the Z axis direction, the control unit 14 has a function of generating a stabilization plate control signal C _S for controlling the stabilization plate actuator 23. The stabilizing plate 21 is a member for stably rotating the thin optical disk 2 and does not rotate itself, but the fixed shaft portion 22 and the stable shaft 22 are not so disturbed that the loading operation of the thin optical disk 2 is not hindered. A movable mechanism composed of the conversion plate actuator 23 is provided.

  In the optical disc apparatus 1, the laser beam emitted from the light source 11 is converted into parallel light by the collimator lens 10, passes through the beam splitter 9, is reflected by the folding mirror 8, and is fixed to the SIL optical head 6 ( SIL) is incident on the objective lens 5. The objective lens 5 irradiates the recording surface of the thin optical disc 2 as near-field light L. The return light reflected from the thin optical disk 2 is reflected by the folding mirror 8, branched by the beam splitter 9, and condensed on the light detection unit 13 by the condenser lens 12.

A part of the detection signal s detected by the light detection unit 13 can be used as a recording signal or a reproduction signal necessary for recording or reproducing information. Here, the description relating to the recording / reproducing is not directly related to the gist of the present invention, and is omitted, and an example in which the detection signal s detected by the light detection unit 13 is used for the gap servo pull-in control according to the present invention will be described. To do. Control unit 14 generates a pull-in control signal C _G on the basis of the detection signal s detected by the light detection unit 13, controls the gap actuator 7. The gap actuator 7 can be constituted by two or three axes by a voice coil motor (VCM). Needless to say, in addition to the configuration shown in FIG. 1, various optical elements for correcting aberrations may be additionally arranged. Gap actuator 7, based on the pull-in control signal C _G, a predetermined target position gap length (GL) between the objective lens 5 of the solid immersion lens is secured to the thin optical disk 2 and SIL optical head 6 (SIL) The follow-up control is performed so that the position error is within a predetermined position error.

In the optical disk apparatus 1, when the thin optical disk 2 is mounted to the mounting portion 3, the control unit 14 generates a rotation control signal C _R, and controls the rotational drive of the spindle motor 4. Although not shown, the optical disc apparatus 1 is provided with a radial direction moving mechanism that translates the SIL optical head 6 in the radial direction along the recording surface of the thin optical disc 2. Therefore, at the time of recording / reproducing in the optical disc apparatus 1, the control unit 14 links the radial direction moving mechanism and the gap actuator 7 of the gap servo so that the near-field light L is spiral, for example, along the recording track of the thin optical disc 2. Or it controls to scan concentrically.

  In the optical disc apparatus 1 according to the present invention, even when the thin optical disc 2 is used, high-precision radial tilt (RT) and tangential tilt (TT) can be adjusted, and high-precision and stable gap pull-in control. Is to do. Hereinafter, the configuration and operation of the control unit 14 will be described in detail.

[Gap servo device]
FIG. 3 is a schematic diagram of the control unit 14 in the optical disc apparatus according to the embodiment of the present invention. The control unit 14 functions as a gap servo device, and includes a stabilization plate control signal generation unit 141, a pull-in control signal generation unit 142, a TT control signal generation unit 143, an RT control signal generation unit 144, a tilt An amount storage unit 145, a disc loading control signal generation unit 146, a disc rotation control unit 147, a recording / reproduction control unit 148, and a recording / reproduction control management unit 149 are provided.

Stabilization plate control signal generating unit 141 has a function in response to an instruction from the reproduction control management unit 149, to generate a stabilizing plate control signal C _S for controlling the stabilization plate actuator 23.

Pull-in control signal generator 142, in response to an instruction from the reproduction control management unit 149 monitors the gap error signal is generated based on the detection signal s (GES), the gap pull-in servo pull-in control signal C _G It has the function to generate. As a configuration of this gap pull-in servo, the combined use of feedback control (FBC) and feedforward control (FFC) described in the prior art is preferable, but only feedback control (FBC) similar to the focus servo of the prior art is used. A servo system may be used. Since the configuration of the gap pull-in servo itself is not directly related to the gist of the present invention, further detailed description is omitted.

The TT control signal generation unit 143 adjusts the tangential tilt control signal C for adjusting the tangential tilt based on the detection signal s with respect to the stabilization plate 21 before recording and reproduction in accordance with an instruction from the recording and reproduction control management unit 149. _It has a function to generate _TT . Moreover, TT control signal generating unit 143 has a function in response to an instruction from the reproduction control management unit 149, it generates a tangential tilt control signal C _TT during recording and reproduction.

In response to an instruction from the recording / reproduction control management unit 149, the RT control signal generation unit 144 generates a radial tilt control signal C _RT for adjusting the radial tilt based on the detection signal s for the stabilization plate 21 before recording / reproduction. It has a function to generate. Moreover, RT control signal generation unit 144, in response to an instruction from the reproduction control management unit 149 has a function of generating a radial tilt control signal C _RT during recording and reproduction.

  The tilt amount storage unit 145 has a function of storing and holding each tilt amount after adjustment by the TT control signal generation unit 143 and the RT control signal generation unit 144.

Disc loading control signal generation unit 146, in response to an instruction from the reproduction control management unit 149 has a function of generating a disc loading control signal C _D.

Disk rotation control section 147, in response to an instruction from the reproduction control management unit 149 has a function of generating a rotation control signal C _R.

  The recording / reproducing control unit 148 uses a part of the detection signal s as a recording signal or a reproducing signal necessary for recording or reproducing information in accordance with an instruction from the recording / reproducing control managing unit 149, and uses a thin optical disk (FOD). 2 has a function of controlling recording / reproduction with respect to 2.

The recording / reproduction control management unit 149, at the time of initial setting before recording / reproduction, in order to adjust the tilt amount based on the detection signal s with respect to the stabilization plate 21, the stabilization plate control signal generation unit 141 and the pull-in control signal generation unit 142. The TT control signal generation unit 143, the RT control signal generation unit 144, and the disk loading control signal generation unit 146 are instructed to store the tilt amount adjusted at the initial setting in the tilt amount storage unit 145. The recording / reproduction control management unit 149 also generates a stabilization plate control signal generation unit 141, a pull-in control signal generation unit 142, a TT control signal generation unit 143, an RT control signal generation unit 144, and a disc loading control signal generation during recording / reproduction. 146, disk rotation control unit 147, and recording / reproduction control unit 148, read each tilt amount stored in the tilt amount storage unit 145 at the time of recording / reproduction, and use this read tilt amount as a reference for the tanger at the time of recording / reproduction. A function of generating a local tilt control signal _CTT and a radial tilt control signal _CRT .

  That is, the control unit 14 functioning as a gap servo device adjusts the tilt amount of the SIL optical head 6 with respect to the stabilizing plate 21 by the recording / reproduction control management unit 149 at the initial setting before recording / reproduction, At the time of recording / reproduction, the gap pull-in control for the thin optical disc 2 is performed based on the adjusted tilt amount.

  The control in the recording / playback control management unit 149 will be described with reference to FIG. In FIG. 4, the recording / reproduction control management unit 149 sets the stabilization plate 21 to a predetermined position (a position where the thin optical disk 2 is stably rotated) without loading the thin optical disk 2 in the tray at the initial setting before recording / reproduction. Thus, the stabilization plate control signal generation unit 141 is instructed (step S11). Here, when the thin optical disk 2 is loaded in the tray, the disk loading control signal generation unit 146 is instructed to unload the tray.

  Next, the recording / reproduction control management unit 149 instructs the pull-in control signal generation unit 142 to execute the gap pull-in control on the stabilization plate 21, and subsequently, the TT control signal generation unit 143 and the RT control signal generation unit 144. To adjust the tilt amount of the SIL optical head 6 (step S12).

  Next, the recording / playback control management unit 149 instructs the TT control signal generation unit 143 and the RT control signal generation unit 144 to indicate the tilt amount of the SIL optical head 6 adjusted with respect to the stabilization plate 21 as a tilt amount storage unit. The data is stored in 145 (step S13).

  Next, the recording / reproduction control management unit 149 instructs the stabilization plate control signal generation unit 141 and the pull-in control signal generation unit 142 to return the stabilization plate 21 and the SIL optical head 6 to the initial positions, and the disk loading control signal. The generation unit 146 is instructed to load the thin optical disk 2 on the tray (step S14).

  Next, the recording / reproduction control management unit 149 instructs the stabilization plate control signal generation unit 141 to set the stabilization plate 21 to a predetermined position (a position where the thin optical disk 2 is stably rotated) (step S15).

  Next, the recording / playback control management unit 149 instructs the disk rotation control unit 147 to rotate the thin optical disk 2 at a predetermined rotational speed (the rotational speed at the time of recording / playback at which the thin optical disk 2 stably rotates) (step S16). .

  Next, the recording / playback control management unit 149 reads the tilt amount stored and held in the tilt amount storage unit 145, and instructs the TT control signal generation unit 143 and the RT control signal generation unit 144 based on this tilt amount to adjust the tilt. While executing the control, the pull-in control signal generator 142 is instructed to perform the gap pull-in control of the SIL optical head 6 (step S17).

  Finally, the recording / playback control management unit 149 instructs the recording / playback control unit 148 to execute the recording / playback control (step S18).

  As a result, the gap servo pull-in control operation in the near-field optical recording on the thin optical disk 2 can be easily performed, and the gap pull-in control can be performed with high accuracy to perform high-density recording on the thin optical disk 2. Will be able to.

[Gap pull-in control method]
Next, an embodiment of a gap pull-in control method of the control unit 14 in the optical disc apparatus 1 will be described. In the pull-in control based on the prior art, the focus servo and tracking servo are operated, the thin optical disk 2 to be recorded / reproduced is placed in the tray, and the stabilization plate 21 with respect to the thin optical disk 2 has a desired clearance (CL). After the thin optical disk 2 is rotated by the spindle motor 7 and rotated stably with low surface shake, the SIL optical head 6 is driven with the tilt amount being unadjustable or insufficient to perform the pull-in control. It was. On the other hand, in the gap pull-in control method according to the present invention, it is possible to adjust the radial tilt (RT) and the tangential tilt (TT) with high accuracy even when the thin optical disk 2 is used, thereby improving the accuracy. To perform stable gap pull-in control. FIG. 5 is a flowchart showing an example of the gap pull-in control method in the optical disc apparatus 1 according to the embodiment of the present invention.

  First, as an initialization process, the control unit 14 initializes the optical disc apparatus 1 so that the radial tilt (RT) and the tangential tilt (TT) of the SIL optical head 6 are set to 0 degrees (see FIG. Step S21).

  Next, the control unit 14 lowers the stabilization plate 21 in advance to a predetermined position in the z direction when rotating the disk (a position of 100 to 300 μm on the disk where the thin optical disk is stably rotated) (step S22). That is, before loading the thin optical disk 2 on the tray, the stabilizing plate 21 is moved to a desired position (for example, a position of about 100 μm on the thin optical disk 2) where the thin optical disk 2 is stably rotated.

  Next, the control unit 14 brings the SIL optical head 6 close to the position of 20 nm to 100 nm from the surface of the stabilization plate 21, irradiates the laser beam from the light source 11, and emits the laser beam on the surface of the stabilization plate 21. The gap error signal (GES) is monitored by evanescent coupling (that is, the laser beam for recording / reproducing is condensed at the tip of the solid immersion lens (SIL)) (step S23).

  Next, the control unit 14 moves the radial tilt (RT) and the tangential tilt (TT) with a gap actuator (for example, a two-axis gonio stage) mounted on the SIL optical head 6 to maximize the evanescent coupling and reflect the light. Then, the optimum radial tilt (RT) and tangential tilt (TT) are determined so as to return (that is, GES is minimized) (step S24).

  More specifically, the control unit 14 brings the objective lens 5 in an evanescently coupled state closer to the stabilization plate 21. Since the stabilizing plate 21 is mainly formed of metal (copper or brass) or acrylic resin, the refractive index nstb> 1 of each medium. For this reason, the laser beam returns depending on the installation position and angle of the stabilization plate 21. When the solid immersion lens (SIL) of the objective lens 5 is moved closer to a position greater than 0 and less than or equal to 100 nm, for example 10 nm, from the surface of the stabilization plate 21, a gap error signal (GES) is returned and this gap error signal ( The position where the evanescent coupling is maximized from GES) and the light is reflected and returned can be searched.

  Next, the controller 14 temporarily returns the SIL optical head 6 to the initial position in the z direction while holding the radial tilt (RT) and the tangential tilt (TT) (or storing and holding them back to the initial state). The stabilizing plate 21 is once returned to the initial position in the z direction so that the angle does not change (step S25). In addition, it is preferable to provide a mechanism that moves the stabilizing plate 21 along a predetermined guide rail so that the angle does not change. In this way, the respective angles of the radial tilt (RT) and the tangential tilt (TT) are swung, the optimum angular position at which the gap error signal (GES) returns most is stored, and then the thin optical disc 2 is stored. Is temporarily retracted to a position away from the thin optical disc 2 so that it does not come into contact with the SIL head 6 when loaded on the tray. This completes the preparation for recording / playback.

  Next, the control unit 14 loads the thin optical disk 2 on the tray in the optical disk apparatus 1 (step S26).

  Next, the control unit 14 starts the rotation of the thin optical disk 2 by controlling the spindle motor 4 (step S27).

  Next, the control unit 14 moves the stabilization plate 21 to a predetermined position at the time of recording / reproduction of 100 μm to 300 μm on the thin optical disk 2, and touches the thin optical disk 2 with a low touch of about 10 μm (peak-peak value). The rotation is stabilized (step S28). More specifically, since the stabilization plate 21 is approaching the thin optical disk 2, the thin optical disk 2 is rotated to a fixed rotational speed (for example, an arbitrary rotational speed of 2500 rpm or more and 4000 rpm or less) that reduces surface vibration. Then, the thin optical disk 2 rotates so as to stick to the surface of the stabilization plate 21 while maintaining a surface runout amount of 10 μm or less while maintaining a distance of about 100 μm with respect to the stabilization plate 21.

  Subsequently, the control unit 14 proceeds to an operation process of gap servo (retraction control). The SIL optical head 6 is brought close to the position of 20 nm to 50 nm with respect to the surface of the thin optical disk 2 by the previously held radial tilt (RT) and tangential tilt (TT) (step S29).

  Next, the control unit 14 starts an operation of gap pull-in control (step S30). In this way, the solid immersion lens (SIL) that condenses the laser light at the tip of the SIL optical head 6 is brought close to the surface of the thin optical disk 2 while maintaining the radial position, and the gap servo pull-in operation is performed.

  Next, the control unit 14 determines whether the gap pull-in control is successful based on whether the gap servo operation is stable and the gap error signal (GES) is stable (step S31). When it is determined that the gap pull-in control has failed (step S31: N), the control unit 14 retracts the SIL optical head 6 to the initial position (step S32), and performs radial tilt (RT) and tangential tilt (TT). Fine adjustment or reshuffling is performed (step S33), and the processing from step S29 is repeated. If it is determined that the gap pull-in control is successful (step S31: Y), the control unit 14 proceeds to step S34. As described above, since the optimum angles of the radial tilt (RT) and tangential tilt (TT) of the SIL optical head 6 with respect to the stabilization plate 21 are stored in advance, the pull-in control of the gap servo is performed based on this optimum angle. Thus, the pull-in control of the gap servo with respect to the thin optical disk 2 can be easily performed with respect to the thin optical disk 2 rotating so as to stick to the surface of the stabilization plate 21.

  Next, the control unit 14 performs control so that data is recorded / reproduced with respect to the thin optical disk by the tracking servo operation (steps S34 and S35). As a result, the tracking operation of the gap servo is enabled, the tracking servo operation is performed, and the recording / reproducing operation can be performed.

  Therefore, the gap servo pull-in control operation in the near-field optical recording on the thin optical disk 2 can be easily performed, and the pull-in control can be made highly accurate. Will be able to do.

  Next, the objective lens 5 on which the solid immersion lens (SIL) is mounted has a conventional Blu-ray disc (BD) as an angle of radial tilt (RT) and tangential tilt (TT) when the thin optical disc 2 is irradiated with laser light. The objective lens has a numerical aperture (NA) that is more sensitive than far-field recording (FFR), which is a condensing recording system with 1 or less.

  FIGS. 6A and 6B show the angle dependence characteristics of the gap error signal (GES) in the tangential direction and the angle dependence due to the tilt in the radial direction in the objective lens 5 on which the solid immersion lens (SIL) is mounted. It is a figure which shows a characteristic. As can be seen from FIG. 6, the amount of return light is about 90% with an angle change of ± 0.15 °, and the amount of return light is about 50% with an angle change of ± 0.3 °. A certain amount of light does not return. In this case, FIG. 7 shows an experimental result of the gap servo pull-in control operation determination based on the gap pull-in control method according to the present invention. In FIG. 7, the gap servo pull-in control operation experiment was performed by changing the angles of tangential tilt (TT) and radial tilt (RT). .

  In this experiment, first, the angle at which the most light amount of tangential tilt (TT) and radial tilt (RT) returns to the stabilizing plate 21 was examined. As a result, the tangential tilt (TT) was 0 °, and the radial tilt. (RT) was -0.1 °. According to the gap pull-in control method of the present invention, these values are stored and held as initial settings.

  After performing this initial setting, the thin optical disk 2 is loaded into the optical disk apparatus 1 and gap servo pull-in control is performed. As a result, the initial setting of tangential tilt (TT) = 0 °, radial tilt (RT) = At the setting of -0.1 °, the pull-in control operation of the gap servo was successful.

  For confirmation, gap servo pull-in control does not operate under the conditions of this peripheral angle, such as TT = 0.5 °, RT = -0.1 °, TT = 0 °, RT = -0.5 °. It was. Moreover, TT = 0.5 °, RT = −0.5 °, etc. did not work. Therefore, in the experimental machine of this optical disc apparatus 1, as shown in FIGS. 6A and 6B, even when fine adjustment operation is performed, tangential tilt (TT) = 0 ° ± 0.1, radial tilt ( RT) =-0.1 ° ± 0.1 is preferable.

  By the way, without depending on the gap pull-in control method according to the present invention, the values of the tangential tilt (TT) and radial tilt (RT) of the stabilizing plate 21 in the optical disc apparatus 1 are measured in advance and stored as default values. There is also a concern that this default value may be set at the time of factory shipment. However, since the stabilization plate 21 is actually accompanied by a movable mechanism for approaching the thin optical disk 2, the result shown in FIG. 6 is maintained without prior tilt adjustment when approaching the thin optical disk 2. Therefore, the gap servo pull-in operation is not always stable. For this reason, some commercially available DVD and BD optical disc drives have a function capable of adjusting and controlling tangential tilt (TT) and radial tilt (RT). In these optical disc drives, adjustment control of tangential tilt (TT) and radial tilt (RT) is performed so as to obtain optimum reflected light with the highest intensity at the time of focus servo pull-in or recording / reproduction. As can be seen from the above, since the allowable angle is narrower in gap servo pull-in control especially in optical recording using near-field light, it is necessary to perform adjustment control of tangential tilt (TT) and radial tilt (RT). become.

  This is because when the tangential tilt (TT) and radial tilt (RT) are not within the allowable angles, or when the gap pull-in control is performed on the thin optical disk 2, the evanescent coupling is always performed on the rotating disk surface. This is because no gap occurs and the light is not transmitted and the gap servo operation is broken. For this reason, the gap pull-in control method according to the present invention is effective for the gap pull-in control to the thin optical disk 2.

  Although specific examples have been described in the above embodiments, the present invention is not limited to these embodiments. For example, although the example in which the stabilizing plate 21 and the SIL optical head 6 are moved in the Z-axis direction has been described, it is a matter of course that a configuration involving movement in other directions may be employed.

  According to the present invention, the gap servo pull-in control operation in the near-field optical recording on the thin optical disk can be easily performed, which is useful for the application of the optical disk technology using the thin optical disk.

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 2 Thin optical disk 3 Mounting part 4 Spindle motor 5 Objective lens 6 SIL optical head 7 Gap actuator 8 Folding mirror 9 Beam splitter 10 Collimate lens 11 Light source 12 Condensing lens 13 Light detection part 14 Control part 18 Radial tilt actuator 19 Tanger Tilt Tilt Actuator 20 Disc Loading Actuator 21 Stabilizer (Stabilizer)
22 Stabilizing plate actuator 23 Stabilizing plate actuator 141 Stabilizing plate control signal generating unit 142 Pull-in control signal generating unit 143 TT control signal generating unit 144 RT control signal generating unit 145 Tilt amount storage unit 146 Disc loading control signal generating unit 147 Disc rotation Control unit 148 Recording / reproduction control unit 149 Recording / reproduction control management unit

Claims (6)

An optical disk apparatus using a solid immersion lens (SIL) having a numerical aperture of 1 or more for a thin optical disk as an objective lens,
A stabilizing plate for stably rotating the thin optical disk;
A spindle motor for rotationally driving the thin optical disk at a predetermined rotational speed;
An SIL optical head for fixing the objective lens;
A tilt actuator for adjusting a tilt amount of the SIL optical head with respect to the thin optical disk;
A gap actuator for controlling a distance between the SIL optical head and the thin optical disk;
A tilt amount adjusting operation by the tilt actuator, and a control unit for controlling a gap pull-in operation by the gap actuator,
The control unit adjusts the tilt amount of the SIL optical head with respect to the stabilizing plate at the initial setting before recording and reproduction, and at the time of recording and reproduction, pulls in the gap to the thin optical disk based on the adjusted tilt amount. An optical disc apparatus that is controlled to perform   2. The optical disc apparatus according to claim 1, wherein the control unit has means for controlling to readjust the adjusted tilt amount within a predetermined allowable range during recording and reproduction.   The control unit sets the stabilization plate to a predetermined position where the thin optical disk is stably rotated without loading the thin optical disk on a tray of the optical disk device at the initial setting before recording and reproduction, and the stabilization 3. The optical disc apparatus according to claim 1, further comprising means for controlling to adjust a tilt amount of the SIL optical head with respect to a plate.   The control unit sets the stabilizing plate at a position where the thin optical disk is stably rotated during recording and reproduction, and then rotates the rotational speed of the thin optical disk as the rotational speed during recording and reproduction, 4. The optical disc apparatus according to claim 3, wherein control is performed so that a gap is drawn into the thin optical disc based on the adjusted tilt amount. A gap servo device that performs gap pull-in control in an optical disc apparatus using a solid immersion lens (SIL) having a numerical aperture of 1 or more for a thin optical disc as an objective lens,
Means for adjusting a tilt amount of a SIL optical head for fixing the objective lens to a stabilization plate for stably rotating the thin optical disk at the time of initial setting before recording and reproduction;
Means for controlling to pull in the gap with respect to the thin optical disk based on the adjusted tilt amount during recording and reproduction;
A gap servo device comprising: A gap pull-in control method in an optical disc apparatus using a solid immersion lens (SIL) having a numerical aperture of 1 or more for a thin optical disc as an objective lens,
Adjusting the tilt amount of the SIL optical head for fixing the objective lens to a stabilization plate for stably rotating the thin optical disk at the initial setting before recording and reproduction;
A step of controlling to pull in the gap with respect to the thin optical disk based on the adjusted tilt amount during recording and reproduction;
A gap pull-in control method.