JP2008065931A - Method of controlling objective lens and sil, and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of controlling an objective lens and an SIL capable of preventing collision between the SIL and an optical disk without using a special optical disk in which surface shake is reduced. <P>SOLUTION: When the objective lens 10 and the SIL 11 are controlled near a surface of the optical disk 12, the objective lens and the SIL approach the optical disk. When the SIL approaches the surface of the optical disk to a distance in which a focus error signal is detected, the focus control is started on the basis of the focus error signal. Next, the focus control is released, and the SIL further approaches the surface of the optical disk. Thereafter, when the SIL approaches the surface of the optical disk to a distance in which a gap signal is detected, the gap control is started on the basis of the gap signal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an objective lens and SIL control method and an optical disk apparatus using the same in the field of recording or reproducing information signals at high density using Solid Immersion Lens (hereinafter abbreviated as SIL).

  Conventionally, in order to improve the information signal recording density of an optical disc, the wavelength of the laser beam used for recording and reproduction is shortened, the numerical aperture (NA) of the objective lens is increased, and the information signal recording layer of the optical disc is formed. There is a demand for reducing the diameter of the light spot.

  For example, an SIL is arranged between the objective lens and the optical disc on the surface of the optical disc in the vicinity of a fraction of the wavelength of the laser beam to make the NA substantially 1 or more. It is described in, for example, “Near Field Recording on First-Surface of the World Journal of Physics”. Reference 1).

  Also, Optical Data Storage 2004, Proceedings of SPIE 5380 (2004) “Near Field read-out of first-surface disk with NA = 1.9 and a proposal. (Non-Patent Document 2).

  FIG. 4 shows an example of the configuration of a conventional optical pickup (for example, Japan Journal Applied Physics, Vol. 44 (2005), pages 3564-3567). A light beam emitted from the semiconductor laser 1 having a wavelength of 405 nm is converted into a parallel light beam by the collimator lens 2 and is incident on the beam shaping prism 3 to form an isotropic light amount distribution. Further, the light beam that has passed through the non-polarizing beam splitter 4 and passed through the polarizing beam splitter 7 passes through the quarter-wave plate 8, is converted from linearly polarized light to circularly polarized light, and enters the expander lens 9.

  The expander lens 9 is configured to control the distance between the two lenses in order to correct spherical aberration. The light beam from the expander lens 9 is incident on the objective lens 10 to be converged light, further passes through the SIL 11, and is irradiated onto the optical disk 12 that is rotationally driven by a spindle motor (not shown).

  A part of the light beam from the semiconductor laser 1 is reflected by the non-polarizing beam splitter 4, collected by the lens 5, and received by the photodetector 6. The amount of light detected here is used to control the emission power of the semiconductor laser 1.

  FIG. 5 is an enlarged view of the vicinity of the laser beam irradiation of the optical disc 1. The optical disk 12 includes a substrate 31, an information signal recording layer 30 formed on the substrate 31 in sequence, and a transparent cover layer 29 having a thickness of several μm. The SIL 11 has a hemispherical shape, and is arranged so that its bottom surface faces the optical disk 12 and is close thereto. The SIL 11 and the objective lens 10 are held by a lens holder 32. The SIL 11 and the objective lens 10 are integrally driven by the actuator 28 in the tracking direction and the focus direction.

  At the time of recording or reproducing the information signal, the convergent light transmitted through the SIL 11 passes through the cover layer 29 and forms a light spot S on the information signal recording layer 30. Here, since the incident light beam from the objective lens 10 is arranged so as to be perpendicularly incident on the spherical surface of the SIL 11, it is condensed through almost the same optical path as that without the SIL 11, but when the SIL 11 is provided in the optical path. Is equivalent to shortening the wavelength by the refractive index.

  As a result, when the refractive index of the constituent material of the SIL 11 is N and the numerical aperture of the objective lens is NA, the diameter of the light spot S formed on the information signal recording layer 30 is approximately N × NA. It is equivalent to. For example, when the refractive index of the constituent material of the SIL 11 is N = 2 and the numerical aperture of the objective lens 10 is NA = 0.7, the effective numerical aperture NAeff is 1.4, and the effect of reducing the diameter of the light spot S is achieved. Is obtained.

  However, such an effect is limited to the case where the distance between the bottom surface of the SIL 11 and the surface of the cover layer 29 is a near-field region that is a fraction of the wavelength 405 nm of laser light (about 100 nm) or less. Only in this case, a light spot S reduced to NAeff is formed on the information signal recording layer 30, and information signals can be recorded and reproduced. In order to maintain this distance during information signal recording / reproduction, gap control described later is required.

  Returning to FIG. 4, the return optical system will be described. The light beam reflected by the optical disk 12 becomes reverse circularly polarized light, enters the SIL 11 and the objective lens 10 and is converted again into a parallel light beam. This light beam further passes through the expander lens 9 and the quarter-wave plate 8, and the light beam that has been linearly polarized in the direction orthogonal to the forward path is reflected by the polarization beam splitter 7.

  The reflected bundle is incident on the half-wave plate 13, and the S-polarized component of the light beam whose polarization plane is rotated by 45 ° by the half-wave plate 13 is reflected by the polarization beam splitter 14 and passes through the lens 15. The light is collected on the photodetector 16. A reproduction signal of the information signal recorded on the optical disk 12 is obtained from the output of the photodetector 16.

  On the other hand, the P-polarized component of the light beam whose polarization plane has been rotated by 45 ° by the half-wave plate 13 is transmitted through the polarization beam splitter 14, reflected by the mirror 17, and passed through the lens 19 on the photodetector 20. It is focused on. A tracking error signal is obtained from the output of the photodetector 20.

  Of the light beams reflected from the bottom surface of the SIL 11, a light beam corresponding to NAeff <1 that is not totally reflected is also reflected as circularly polarized light that is reverse to the incident, similarly to the light reflected from the optical disk 12. However, for a luminous flux corresponding to NAeff ≧ 1 that causes total reflection, a phase difference δ shown in the following equation is generated between the P-polarized component and the S-polarized component, and is shifted from circularly polarized light to become elliptically polarized light.

tan (δ / 2) = cos θi × √ (N2 × sin2θi−1) / (N × sin2θi) (1) Therefore, when passing through the quarter-wave plate 8, the polarization component in the same direction as the forward path is included. Become. This polarization component is transmitted through the polarization beam splitter 7, reflected by the non-polarization beam splitter 4, and condensed on the photodetector 26 via the lens 25.

  The light quantity of this light beam hardly depends on the distance outside the near-field area where the SIL 11 is sufficiently separated from the optical disk 12, but monotonously decreases as the distance between the bottom surface of the SIL 11 and the optical disk 12 approaches within the near-field area. To do. Therefore, the detection signal of the amount of light totally reflected in this way can be used as a gap signal corresponding to the distance between the bottom surface of the SIL 11 and the optical disk 12.

The distance between the bottom surface of the SIL 11 and the optical disk 12 can be kept at a predetermined distance of 100 nm or less by a gap control operation for driving the actuator 28 so that the gap signal maintains a predetermined target value. Such gap control is described in detail in the aforementioned paper of Japan Journal Applied Physics, Vol. 44 (2005), pages 3564-3567. Further, since this light beam is not modulated by the information signal recorded on the optical disc 12, a stable gap signal can be obtained regardless of the presence or absence of the information signal.
Japan Journal Applied Physics, vol. 44 (2005), pages 3564-3567, “Near Field Recording on First-Surface Write-Once Media with NAI 1S. Optical Data Storage 2004, Proceedings of SPIE 5380 (2004) “Near Field read-out of first-surface disk with NA-1.9 and a proposal for a coer

  As described above, in the optical disk apparatus using the SIL, at least during the recording / reproducing of the information signal, the distance between the bottom surface of the SIL and the cover layer of the optical disk needs to be kept at a predetermined value of 100 nm or less. As means for that purpose, a method of obtaining a gap signal from the amount of total reflected light from the bottom surface of the SIL is conventionally known.

  However, in a state where the power is turned off while the optical disk is left inside the apparatus, or in a power saving state where no information signal recording / reproducing operation is performed, in order to prevent damage due to contact between the SIL and the optical disk, the SIL Must be retracted sufficiently upward from the optical disk. When the information signal recording / reproducing operation is started from such a state, the SIL must be approached from the retracted position to 100 nm at which the gap signal can be obtained, and then the gap control operation must be started.

Therefore, it is assumed that the specifications of the optical disk are the same as those of conventional general products, and the surface runout is ± 50 μm and the rotation speed is 3600 rpm. Further, if the maximum speed of the optical disk itself due to surface wobbling is 1.9 × 10 ⁻² m / s and the SIL approach speed is 0.3 × 10 ⁻² m / s, the relative approach speed of both is maximum. Thus, 2.2 × 10 ⁻² m / s. Further, in a general actuator specification, the instantaneous acceleration is about 500 m / s ² at the maximum, so a stop distance of about 480 nm is required until the relative speed of the both becomes zero.

  However, in reality, the gap signal can be obtained in the approaching process when the SIL reaches a distance of 100 nm from the surface of the cover layer. Even if the actuator is driven at this point to start deceleration. In time, the SIL and the optical disc collide and are damaged.

  In the past, in order to avoid such a situation, a special optical disk with reduced surface runout was used by using a glass substrate with less deformation, but such an optical disk is There existed a subject that manufacturing cost became high. If the rotational speed of the optical disk and the approach speed of the SIL are sufficiently reduced at the start of the control operation, the stop distance can be set to 100 nm or less to avoid a collision. There has been a problem that the time until signal recording / reproduction becomes possible increases.

  An object of the present invention is to provide an objective lens, a SIL control method, and an optical disc apparatus that can prevent a collision between an SIL and an optical disc and do not use a special optical disc with reduced surface shake.

  In the present invention, when the objective lens and the SIL are held in the vicinity of the optical disk surface, the objective lens and the SIL are brought close to the optical disk from the retracted position, and when the SIL approaches the optical disk surface to a distance where a focus error signal is detected. Focus control is started based on the focus error signal. Next, the focus control is canceled and the SIL is further brought closer to the optical disk surface. After that, when the SIL approaches the optical disk surface up to a distance where the gap signal is detected, the gap control is started to keep the distance between the bottom surface of the SIL and the optical disk surface constant based on the gap signal.

  According to the present invention, it is not necessary to use a special optical disk with reduced surface wobble, and even if an optical disk with a general specification is used, damage caused by a collision between the SIL and the optical disk at the start of the position control operation in the focus direction is prevented. Occurrence can be prevented. In addition, there is no increase in time from the start of operation until the transition to a stable control state and recording or reproduction of an information signal becomes possible.

  Next, the best mode for carrying out the invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of an optical pickup of an optical disc apparatus according to the present invention.

  In FIG. 1, a circuit for recording information on an optical disk, a circuit for reproducing information recorded on the optical disk, a servo control circuit for performing focus control and tracking control, a gap control circuit for performing gap control based on the gap signal as described above, etc. Is omitted. Further, a circuit and mechanism such as a spindle motor that rotates the optical disk and a controller that controls the entire apparatus are also omitted.

  First, a light beam emitted from the semiconductor laser 1 having a wavelength of 405 nm is converted into a parallel light beam by the collimator lens 2 and is incident on the beam shaping prism 3 to form an isotropic light amount distribution. Further, the light beam that has passed through the non-polarizing beam splitter 4 and passed through the polarizing beam splitter 7 passes through the quarter-wave plate 8, is converted from linearly polarized light into circularly polarized light, and enters the expander lens 9.

  The expander lens 9 is a lens for correcting spherical aberration, and the spherical aberration can be adjusted by changing the distance between the two lenses by a driving means (not shown). The light beam from the expander lens 9 enters the objective lens 10 to be converged light, and further passes through the SIL 11 to form a minute light spot on the optical disk 12 that is rotationally driven by a spindle motor (not shown). To do.

  The SIL 11 is hemispherical as shown in FIG. The structures of the objective lens 10, SIL 11, and optical disk 12 are the same as in FIG. 5, and the objective lens 10 and SIL 11 are held by a lens holder 32, and the lens holder 32 is mounted on an actuator 28. Then, the objective lens 10 and the SIL 11 are integrally controlled and driven by the actuator 28 in the focus direction and the tracking direction so that the light spot S on the optical disk 12 follows the surface shake or eccentricity of the optical disk 12.

  A part of the light beam from the semiconductor laser 1 is reflected by the non-polarizing beam splitter 4, condensed by the lens 5, and received by the photodetector 6. The amount of light detected here is used to control the emission power of the semiconductor laser 1.

  The light beam that has been transmitted through the SIL 11 and reflected by the optical disk 12 becomes reverse circularly polarized light, and enters the SIL 11 and the objective lens 10 to be converted back into a parallel light beam. This light beam passes through the expander lens 9 and the quarter-wave plate 8, and the light beam that has been linearly polarized in the direction orthogonal to the forward path is reflected by the polarization beam splitter 7.

  The reflected light enters the half-wave plate 13, and the S-polarized component of the light beam whose polarization plane is rotated by 45 ° by the half-wave plate 13 is reflected by the polarization beam splitter 14 and passes through the lens 15. Then, the light is condensed on the photodetector 16. A reproduction signal of the information signal recorded on the optical disc 12 is obtained from the output of the detector 16.

  The P-polarized component is transmitted through the polarization beam splitter 14, reflected by the non-polarization beam splitter 18, and condensed on the photodetector 20 via the lens 19. A tracking error signal is obtained from the output of the photodetector 20.

  Further, the light beam that has passed through the non-polarizing beam splitter 18 is condensed on the photodetector 23 via the sensor lens 22. For example, the sensor lens 22 is a toric lens and the light detector 23 is a detector having a light receiving surface divided into four, and a focus error signal is obtained by a known astigmatism method by a focus error detection circuit (not shown).

  A focus control circuit and a tracking control circuit (not shown) control the actuator 28 based on the tracking error signal and the focus error signal, and integrally drive the objective lens 10 and the SIL 11 in the tracking direction or the focus direction. Thereby, tracking control and focus control are performed so that the light spot S follows the displacement of the optical disk 12 such as eccentricity and surface deflection.

  Here, only when the distance between the bottom surface of the SIL 11 and the optical disk 12 is a near-field region that is a fraction of the laser light wavelength 405 nm (about 100 nm) or less, the laser light transmitted through the SIL 11 records information signals on the optical disk 12. A light spot S having a diameter corresponding to NAeff is formed on the layer 30. At that time, the information signal can be recorded and reproduced. If the NA of the objective lens 10 is 0.7 and the NA of the material constituting the SIL 11 is 2, NAeff is 1.4.

  In this case, among the light beams reflected by the bottom surface of the SIL 11, the light beam corresponding to NAeff <1 that is not totally reflected is reflected as circularly polarized light that is reverse to the incident, similarly to the light reflected from the optical disk 12. Is done. In addition, for a luminous flux corresponding to NAeff ≧ 1 causing total reflection, a phase difference δ shown in the equation (1) is generated between the P-polarized component and the S-polarized component, deviating from circularly polarized light to become elliptically polarized light, and ¼ wavelength. When the light passes through the plate 8, it includes a polarization component in the same direction as the forward path.

  This polarization component is transmitted through the polarization beam splitter 7, reflected by the non-polarization beam splitter 4, and condensed on the photodetector 26 via the lens 25. The light amount of this light beam depends on the distance between the bottom surface of the SIL 11 and the cover layer 29 in the near-field region, and decreases as they approach each other. Therefore, this light amount detection signal can be used as a gap signal. This gap signal is detected by a gap signal detection circuit (not shown).

  In a gap control circuit (not shown), the distance between the bottom surface of the SIL 11 and the optical disk 12 is set to a predetermined distance of 100 nm or less by driving the actuator 28 so that the gap signal becomes a predetermined target value. Kept. At least during recording or reproduction of an information signal, it is necessary to maintain the distance between them at a predetermined value by such a gap control operation.

  As described above, the optical disc apparatus according to the present invention includes the focus error signal detection means (second detection means) using the reflected light from the optical disc, and the gap signal detection means (first detection means) using the reflected light totally reflected by the bottom surface of the SIL 11. Detection means). Therefore, the detection signals from the two detection means are used for position control of the light spot S in the focus direction.

  Here, when reflected light from the surface of the cover layer 29 of the optical disk 12 is used, a focus error signal can be obtained when the distance between the bottom surface of the SIL 11 and the cover layer 29 is about the same as the thickness of the cover layer 29. That is, the detection distance by the second detection means is about several μm. On the other hand, a gap signal due to reflected light from the bottom surface of the SIL 11 cannot be obtained unless the bottom surface of the SIL 11 and the cover layer 29 are at a distance of 100 nm or less corresponding to the near-field region. That is, the detection distance by the first detection means is 100 nm or less, which is small compared to the focus error signal detection means (second detection means), but the detection accuracy is high.

  Next, the position control operation in the focus direction of the optical disc apparatus according to the present invention will be described in detail. FIG. 2 shows a flowchart of the position control start operation. This operation consists of step 1 to step 4 and is executed in this order. In the following description, the control in FIG. 2 is performed by a controller (not shown).

  An example of the displacement (time change) in the focus direction of the bottom surface of the SIL 11, the light spot, and the surface of the cover layer 29 in each step of the operation is shown in FIG. Is shown in FIG. Hereinafter, the operation in each step will be described with reference to FIGS.

[Step 1]
The objective lens 10 and the SIL 11 are held in advance in a state sufficiently separated from the optical disc 12, and the optical disc 12 is rotated. The surface height of the cover layer 29 changes with periodicity as shown in FIG. 3 (a) due to the surface vibration accompanying the rotation of the optical disk 12.

  At this time, the objective lens 10 and the SIL 11 may be driven to retract in the focus direction by the actuator 28, but the objective lens 10 and the SIL 11 are disposed so as to be in the retracted position in a non-driven state (neutral state) by the actuator 28. Also good. Then, it is not necessary to drive the actuator 28 in particular.

Next, from this state, the objective lens 10 and the SIL 11 are driven in the focus direction by the actuator 28 to gradually approach the optical disk 12. However, since the optical disk 12 is also displaced at the same time due to surface deflection, the change in the distance between the SIL 11 and the cover layer 29 is the sum of the displacements as shown in FIG. That is, even if the driving speed of the SIL 11 by the actuator 28 is sufficiently reduced, the relative speed of the SIL 11 with respect to the optical disk 12 is 2.2 × 10 ⁻² m / max at the maximum depending on the magnitude of the surface deflection of the optical disk 12. may be s.

  During this operation, since the objective lens 10 and the SIL 11 are separated from the optical disc 12 and the formed light spot is above the optical disc 12, no focus error signal is detected from the output of the photodetector 23 yet.

[Step 2]
When the light spot S is sufficiently close to the optical disk 12 and reaches the surface of the cover layer 29 at the time T1 shown in FIG. 3, a focus error detection circuit (not shown) detects a focus error signal from the output of the photodetector 23. The focus control circuit controls the actuator 28 based on the focus error signal and drives the objective lens 10 and the SIL 11 in the focus direction so that the light spot follows the height fluctuation of the surface of the cover layer 29. To start.

  At this time, the distance between the bottom surface of the SIL 11 and the surface of the cover layer 29 is maintained at the same level as the thickness of the cover layer 29 (several μm). That is, as shown in FIG. 3B, at this time, the relative speed of the SIL 11 with respect to the optical disk 12 is decelerated to enter a stationary state (relative speed = 0).

If the relative speed of the SIL 11 with respect to the optical disk 12 is 2.2 × 10 ⁻² m / s at the maximum at the time T1, the stop distance until the relative speed of the both becomes 0 needs to be about 480 nm. To do. In this case, in this embodiment, since the distance between the bottom surface of the SIL 11 and the surface of the cover layer 29 is about several μm at the start of the control operation, the SIL 11 should be stationary (relative speed = 0) without colliding with the optical disk 12. Can do.

  A controller (not shown) controls this state so as to maintain this state for a plurality of rotations (for example, five rotations) of the optical disk 12, and analyzes a plurality of cycles (rotations) of the drive signal of the actuator 28 during the learning operation. Then, a time point T2 slightly before the displacement due to the surface runout is maximized is determined in advance as a time point for the transition to the next step 3.

  Prior to this operation, the expander lens 9 may be driven to make the incident light on the objective lens 10 divergent. By doing so, the light spot S is formed farther from the bottom surface of the SIL 11, so that it is possible to further increase the distance between the SIL 11 and the cover layer 29 in the focus control operation state.

  If the focus control operation fails to start, the process returns to step 1 and the series of operations is performed again.

[Step 3]
At the time T2 shown in FIG. 3, the controller cancels the focus control operation by the actuator 28, and holds the drive signal (voltage or current) level at the value at the time T2. As a result, as shown in FIG. 3A, the SIL 11 stops at a fixed position. However, since the time T2 is slightly before the displacement due to the surface shake of the optical disk 12 becomes the maximum, the surface of the cover layer 29 is Continue approaching SIL11. However, this approach speed is sufficiently small because it is close to the time point at which the time T2 becomes the maximum of the runout, and can be at least about 1/10 of the maximum speed (2.2 × 10 ⁻² m / s) in step 2. .

[Step 4]
When the optical disk 12 approaches the SIL 11 and the distance between the surface of the cover layer 29 and the bottom surface of the SIL 11 reaches the near-field region (100 nm or less) at time T3, the light beam totally reflected on the bottom surface of the SIL 11 as described above. A gap signal can be obtained from the amount of light. The gap signal is detected from the output of the photodetector 26 by a gap detection circuit (not shown) as described above.

  Here, a gap control circuit (not shown) starts a gap control operation based on the gap signal. At this time, the SIL 11 is driven by the actuator 28 until the gap signal reaches a predetermined target value, for example, 30 nm, and is held at a constant value when the distance between the bottom surface and the surface of the cover layer 29 reaches a predetermined value.

  Prior to this operation (step 3), the relative speed of the SIL 11 with respect to the optical disk 12 is sufficiently small. Therefore, in this operation, the SIL 11 is kept stationary (relative speed = 0) without colliding with the optical disk 12, and stable. Transition to a different control state. Further, since the driving amount of the SIL 11 in this step is 100 nm or less, the required time is extremely short although the speed is small.

  If the start of the gap control operation fails, the process returns to step 1 and the series of operations is performed again.

It is a figure which shows one Embodiment of the optical pick-up of the optical disk apparatus based on this invention. It is a flowchart figure which shows the position control start operation | movement of a focus direction which concerns on this invention. It is a figure which shows an example of the displacement (time change) of each part in the position control start operation | movement of a focus direction which concerns on this invention. It is a figure which shows the structure of the optical pick-up of the conventional optical disk apparatus. It is an enlarged view around the light spot of the conventional optical disk apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Collimator lens 3 Beam shaping prism 4 Non-polarization beam splitter 5 Lens 6 Photo detector 7 Polarization beam splitter 8 1/4 wavelength plate 9 Expander lens 10 Objective lens 11 SIL
DESCRIPTION OF SYMBOLS 12 Optical disk 13 1/2 wavelength plate 14 Polarizing beam splitter 15 Lens 16 Photo detector 17 Mirror 18 Non-polarizing beam splitter 19 Lens 20 Two-split photo detector 22 Sensor lens 23 Photo detector 25 Lens 26 Photo detector 28 Actuator 29 Cover Layer 30 Information signal recording layer 31 Substrate 32 Lens holder

Claims (4)

An objective lens, a SIL disposed between the objective lens and the optical disc, means for integrally driving the objective lens and the SIL in a focus direction, and a gap signal detected based on reflected light from the bottom surface of the SIL. In the method for controlling the objective lens and the SIL of the optical disc apparatus, comprising the first detection means and the second detection means for detecting the focus error signal based on the reflected light from the optical disc surface,
Making the objective lens and the SIL approach the optical disc from the retracted position by the driving means;
Starting focus control based on the focus error signal when the SIL approaches the surface of the optical disc up to a distance at which a focus error signal is detected by the second detection means;
Releasing the focus control and further bringing the SIL closer to the optical disc surface;
When the SIL approaches the surface of the optical disk up to a distance at which the gap signal is detected by the first detection means, based on the gap signal, the gap control is started to keep the distance between the bottom surface of the SIL and the optical disk surface constant. An objective lens and a method for controlling SIL. In the step of releasing the focus control, the focus control is performed while the optical disk is rotating, and the displacement due to the surface vibration of the optical disk is analyzed from the drive signal of the driving means during the rotation, and the displacement is determined to be a maximum value. 2. The method for controlling an objective lens and an SIL according to claim 1, wherein the focus control is canceled at a time point before. 3. The objective lens and SIL control method according to claim 2, wherein in the step of canceling the focus control, the drive signal of the drive means maintains the value at the time of canceling the focus control as it is. An objective lens, a SIL disposed between the objective lens and the optical disc, means for integrally driving the objective lens and the SIL in a focus direction, and a gap signal detected based on reflected light from the bottom surface of the SIL. An optical disc apparatus comprising: 1 detection means; and second detection means for detecting a focus error signal based on reflected light from the surface of the optical disk.
Means for causing the objective lens and SIL to approach the optical disc from a retracted position by the driving means;
Means for starting focus control based on the focus error signal when the SIL approaches the surface of the optical disc up to a distance at which the focus error signal is detected by the second detection means;
Means for releasing the focus control and further bringing the SIL closer to the optical disc surface;
When the SIL approaches the surface of the optical disk up to a distance at which the gap signal is detected by the first detection means, based on the gap signal, the gap control is started to keep the distance between the bottom surface of the SIL and the optical disk surface constant. And an optical disc apparatus characterized by comprising:

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