JP2008146739A - Optical recording and reproducing method and device, and optical head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording and reproducing device and a method for stably correcting the tilt of an optical recording medium and a near-field light irradiation part, and an optical head. <P>SOLUTION: In the optical disk device, after the tilt of an SIL with respect to an optical disk is corrected, a gap length and a full-reflection return light amount forms a linear relation. Thus, a data processing part switches the target value of a gap servo from a tilt correction gap servo target value to a final gap servo target value, thereby controlling a gap from, e.g., a current gap length of 50 nm to a final target value of 30 nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical recording / reproducing method, an optical recording / reproducing apparatus, and an optical head for recording a signal on an optical recording medium using near-field light.

  In recent years, for example, in an optical disc, in order to improve the recording density of laser light, signals are recorded and / or reproduced using near-field light (near field light) localized in a region much smaller than the wavelength of the light. Optical disk devices have been developed.

  In an optical disc apparatus using near-field light, it is necessary to control the gap between the optical disc and the end surface of an SIL (Solid Immersion Lens) installed in a head such as an objective lens unit to a distance (near field) where near-field light is generated. is there. Generally, this near field is ½ of the wavelength of the input laser beam. For example, when a 400 nm blue-violet laser is used, the near field is about 200 nm. In order to keep such a slight gap constant, there is a gap servo method in which the gap is controlled based on the amount of laser light reflected from the disk side.

  For example, Patent Document 1 discloses an SIL that is disposed opposite to a disk and that can collect light emitted from a light source as near-field light on the optical disk at a position where the distance from the disk is a predetermined distance. A control method is described in which the tilt is corrected while the SIL is in contact with the disc, and then the final gap length is controlled.

JP 2005-259329 A

  However, when tilt correction is performed in a state where the SIL is in contact with the optical disk as described in Patent Document 1, it is a precondition that the optical disk is stationary. Further, if the SIL is in contact with the optical disc, the SIL end surface may be contaminated by dust adhering to the disc surface.

  The present invention has been proposed in view of such a conventional situation, and controls the gap between an SIL and an optical disc in order to record and / or reproduce a signal using near-field light (near-field light). It is an object of the present invention to provide an optical recording / reproducing method, an optical recording / reproducing apparatus, and an optical head that stably perform the above.

  In order to achieve the above-mentioned object, the present invention provides an optical recording / reproducing method for recording and / or reproducing data by irradiating an optical recording medium with a near-field light from a near-field light irradiating unit. A first gap control step of performing gap servo so that a gap between the medium and the near-field light irradiation unit becomes a first gap length in the near field; and the first gap in the first gap servo step. A tilt control step for correcting the tilt of the near-field light irradiation unit with respect to the optical recording medium while maintaining the gap controlled to be long, and the gap between the optical recording medium and the near-field light irradiation unit is the proximity And a second gap control step of performing gap servo so as to have a second gap length for detecting data by field light.

  In order to achieve the above-described object, the present invention is an optical recording / reproducing apparatus that records and / or reproduces data by irradiating an optical recording medium with near-field light, and a light source that emits light; A near-field light irradiating unit that irradiates the optical recording medium with light emitted from the light source as near-field light, recording / reproducing means for recording and / or reproducing data on the optical recording medium, and the light source Light receiving means for receiving the totally reflected return light of the emitted light, control means for controlling the gap between the optical recording medium and the near-field light irradiation section, and the tilt of the near-field light irradiation section with respect to the optical recording medium Tilt control means for controlling the gap, and the gap control means performs gap servo so that a gap between the optical recording medium and the near-field light irradiation unit becomes a first gap length in the near-field, and the tilt control means Control means The tilt of the near-field light irradiation unit with respect to the optical recording medium is corrected while maintaining the gap controlled to the first gap length by the first gap control means, and the gap control means After the tilt is corrected by the control means, gap servo is performed so that the gap between the optical recording medium and the near-field light irradiator becomes a second gap length for performing data detection by the near-field light. It is characterized by that.

  In order to achieve the above-described object, the present invention provides an optical head for recording and / or reproducing data by irradiating an optical recording medium with near-field light, the light source for emitting light, and the light source. A near-field light irradiating unit that irradiates the optical recording medium with light emitted from the optical recording medium, recording / reproducing means for recording and / or reproducing data on the optical recording medium, and the light source. Light receiving means for receiving the totally reflected return light of the reflected light, control means for controlling the gap between the optical recording medium and the near-field light irradiating section, and controlling the tilt of the near-field light irradiating section with respect to the optical recording medium Tilt control means, and the gap control means performs gap servo so that a gap between the optical recording medium and the near-field light irradiation unit becomes a first gap length in the near-field, and the tilt control means Is the above The tilt of the near-field light irradiation unit with respect to the optical recording medium is corrected while maintaining the gap controlled to the first gap length by one gap control unit, and the gap control unit includes the tilt control unit. After the tilt is corrected by the gap servo, the gap servo is performed so that the gap between the optical recording medium and the near-field light irradiation unit becomes a second gap length for performing data detection by the near-field light. Features.

  According to the present invention, gap servo is performed so that the gap between the optical recording medium and the near-field light irradiation unit becomes the first gap length in the near-field, and the gap controlled to the first gap length is maintained. The gap servo is adjusted so that the gap between the optical recording medium and the near-field light irradiating unit is corrected to the optical recording medium, and the gap between the optical recording medium and the near-field light irradiating unit becomes the second gap length for detecting data by the near-field light By doing so, it becomes possible to control the final gap position without causing the near-field light irradiating part to collide with the optical recording medium at the time of pull-in, and a stable gap servo can be realized, so that a stable near-field optical recording medium can be realized. The data can be recorded / reproduced by

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an optical disc apparatus according to an embodiment to which the present invention is applied. The optical disc apparatus 1 controls the gap between the SIL 61 and the optical disc 50 (hereinafter referred to as gap servo) in order to record and / or reproduce a signal using near-field light (near field light).

  The optical head 10 includes a laser diode 11 as a light source, collimator lenses 12 and 13, an anamorphic prism 14 for shaping laser light, a polarization beam splitter 15, a quarter wavelength plate 16, and a chromatic aberration correction lens 17. A laser beam expansion lens 18, a beam splitter 19, and a condensing element 22 are provided on the optical axis of the light emitted from the laser diode 11. In addition, the optical head 10 includes a photodetector 23 that is a first light receiving unit on the optical axis of light reflected by the polarization beam splitter 15, and a second optical axis on the optical axis of light reflected by the beam splitter 19. A photodetector 24 which is a light receiving unit is provided. The optical head 10 also includes a condenser lens 21, an auto power controller 25, a laser diode driver 26, and a photodetector 28.

  The photo detector 24 is a quadrant photo detector having light receiving areas 24a, 24b, 24c, and 24d.

  In the optical disc apparatus 1, focusing servo, tracking servo servo, spindle servo, and the like may be performed based on the return light amount received by the photo detector 23 as the first light receiving unit and the photo detector 24 as the second light receiving unit. . The control unit 27 may include a sled servo module that roughly moves the optical head 10.

  The tracking servo performs tracking control of the light collecting element 22 based on the tracking error signal. For this tracking servo, a method such as a phase difference method, a three-beam method, a push-pull method, or the like can be used. The spindle servo controls the rotation of the spindle motor 40.

  The auto power controller 25 outputs a predetermined signal to the laser diode driver 26 so that the laser power output from the laser diode 11 becomes constant based on the signal output from the photodetector 28.

  FIG. 2 is a side view showing the condensing element 22 and the optical disc 50 in the optical head 10. The condensing element 22 is configured by installing a SIL 61 and an aspherical lens 62 on a biaxial actuator 63 (actuators 63a and 63b).

  The SIL 61 and the aspheric lens 62 are moved by the biaxial actuator 63. The biaxial actuator 63 is driven so that the distance between the SIL 61 and the aspherical lens 62 becomes a near field of, for example, 30 nm.

  For the gap servo in the present embodiment, return light (total reflection return light) of light incident on the SIL 61 at an angle causing total reflection is used in the incident laser light.

  The overall operation of the optical disc apparatus 1 having such a configuration will be described.

  When the optical disk 50 is set in the optical disk apparatus 1, each servo control is performed by the control unit 27. The laser light emitted from the laser diode 11 is converted into parallel light by the collimator lens 12 and shaped by the anamorphic prism 14. The laser light incident on the beam splitter 19 is split into laser light that passes through the beam splitter 15 as it is and enters the quarter-wave plate 16 and laser light that enters the condenser lens 21. The laser light incident on the condenser lens 21 is received by the photodetector 28 and then controlled by the auto power controller 25 so that the power of the laser light emitted from the laser diode 11 becomes constant. The light incident on the quarter-wave plate 16 is converted into circularly polarized light by the quarter-wave plate 16, corrected for chromatic aberration by the chromatic aberration correction lens 17, and collected through the extension lens 18 and the collimator lens 13. The light enters the optical element 22.

  The laser light incident on the condensing element 22 is condensed as near-field light on the optical disc 50 and a signal is recorded on the optical disc 50.

  The totally reflected return light reflected by the optical disk 50 enters the polarization beam splitter 15 via the SIL 61, the aspherical lens 64, the collimator lens 13, the expansion lens 18, the chromatic aberration correction lens 17, and the quarter wavelength plate 16. Is done. Here, the totally reflected return light from the optical disk 50 is reflected by the polarization beam splitter 15 because the phase is advanced by a half of the wavelength by passing through the quarter wavelength plate 16 in the forward path and the return path. The light is received by the photodetector 23 which is the first light receiving unit.

  On the other hand, since the total reflected return light reflected by the SIL 61 rotates slightly while being reflected at the end face of the SIL 61, it passes through the polarizing beam splitter 15 and is reflected by the beam splitter 19 to be second received light. The light is received by the photodetector 24 which is an optical part.

  That is, the optical disc apparatus 1 includes the polarization beam splitter 15 and the beam splitter 19 to form a light separation unit 80, separates the total reflection return light from the optical disc 50 and SIL 61, and converts the total reflection return light from the optical disc 50 to the polarization beam splitter. 15 is separated by 15 and received by the photodetector 23 as the first light receiving unit, and the totally reflected return light from the SIL 61 is reflected by the beam splitter 19 and received by the photo detector 24 as the second light receiving unit. Is provided.

  The photo detector 23 which is the first light receiving unit detects information recorded on the recording surface of the optical disc 50. On the other hand, the photo detector 24 as the second light receiving unit detects total reflection return light that varies depending on the distance between the SIL 61 and the optical disc 50.

  Therefore, in the optical disc apparatus 1, it is possible to detect a gap, which is the distance between the surface of the optical disc 50 and the end face of the SIL 61, based on the total reflected return light amount detected by the photodetector 24 that is the second light receiving unit.

  Here, FIGS. 3A and 3B show the principle of detecting the gap between the SIL 61 and the optical disk 50 arranged at a position facing the optical disk 50 that performs recording and / or reproduction using near-field light. The description will be given with reference. 3A is a diagram showing a gap (here, referred to as gap g) between the optical disc 50 and the end surface of the SIL 61 on the optical disc 50 side, and FIG. 3B is a total reflected return light amount with respect to the gap g. It is a figure which shows the change of.

  As shown in FIG. 3B, in the far field region where the gap g is approximately ¼ or less of the incident light wavelength λ and is equal to or longer than the distance at which the near-field light is generated, the incident light is incident at the angle of total reflection at the end face of the SIL 61. The reflected light is totally reflected by this end face, so that the total reflected return light amount is always constant.

  Further, in the near field region where the gap g is approximately ¼ or less of the incident light wavelength λ and is equal to or less than the distance at which the near-field light is generated, a part of the incident light is soaked at an angle at which the SIL 61 is totally reflected. Therefore, the total reflected return light amount decreases.

  Further, at the position where the SIL 61 and the optical disc 50 are in contact, that is, the position where the gap is zero, all of the incident light is transmitted to the optical disc 50, and thus the total reflected return light amount becomes zero.

  As described above, the change in the total reflected return light amount in the gap region that generates near-field light occurs in the near-field region, and gradually decreases as the gap g approaches the optical disc 50 from the position of λ / 4, and is substantially reduced in the intermediate portion. In a region that linearly decreases and further approaches the surface of the optical disc 50, a curve that gradually decreases gradually is obtained again.

  Therefore, the gap g between the SIL 61 and the optical disk 50 can be 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 g.

  In the optical disc apparatus 1, total reflected return light is detected in four light receiving areas (light receiving areas 24a, 24b, 24c, and 24d) that constitute the photodetector 24 that is the second light receiving section.

Here, if the signal amounts of the signals detected in the light receiving regions 24a, 24b, 24c, and 24d are GES11, GES12, GES13, and GES14, GES11, GES12, GES13, and GES14 are expressed as shown in Equation (1). The gap error signal amount GES is obtained by addition.
GES = GES11 + GES12 + GES13 + GES14 (1)

  FIG. 4 is a graph showing a change in the gap error signal amount GES with respect to the gap. Generally, in gap control, a predetermined gap control reference value s is set, and a gap control amount based on a difference from the gap error signal amount GES is calculated. At this time, in the optical disc apparatus 1, the control unit 27 calculates a gap control amount, outputs a gap control signal that is the gap control amount to the biaxial actuators 63a and 63b, and drives the biaxial actuator.

  FIG. 5 is a block diagram illustrating an internal configuration of the control unit 27. The control unit 27 controls the total reflected return light amount from the SIL 61 by driving the biaxial actuator 63. The photodetector 24 detects the total reflection return light amount. The detected total reflected return light amount is normalized to 1 V, for example, by a normalization gain 71. The normalized total reflected return light amount is converted from an analog signal to a digital signal by an AD (analog to digital) converter 72. The digitized total reflected return light amount is input to the data processing unit 73. When the total reflected return light amount is input, the data processing unit 73 outputs a gap error signal generated based on the difference between the predetermined threshold and the total reflected return light amount to the driver 74. The driver 74 drives the biaxial actuators 63a and 63b so that the signal amount of the gap error signal becomes zero.

  FIG. 6 is a diagram for explaining the relationship between the gap length and the total reflected return light amount. In FIG. 6, the vertical axis represents the amount of light (unit is arbitrary), and the horizontal axis represents the gap (nm).

  Here, a case where a laser having a wavelength of 140 nm is used as incident light will be described. Since the near-field state is generally ½ or less of the wavelength, in the far-field state where the gap length is 70 nm or more, the light incident on the end surface of the SIL 61 at an angle causing total reflection is All are reflected by the end face of the SIL 61, and the total reflected return light amount is constant.

  However, in the near-field state in which the gap length is 70 nm or less, a part of the light incident on the SIL end face is transmitted through the end face of the SIL 61 at an angle causing total reflection, so that the total reflected return light amount decreases. Further, when the gap length is zero, that is, when the SIL 61 and the optical disk 50 come into contact, all the light incident on the end surface of the SIL 61 at an angle causing total reflection is transmitted through the end surface of the SIL 61, and the total reflected return light amount becomes zero.

  In FIG. 6, in the linear region 100 in which the gap length and the total reflected return light amount are linear, the total reflected return light amount having a linear relationship with the gap length is obtained. In the optical disc apparatus 1, the total reflected return light amount is detected as a servo error signal in the linear region 100, and gap servo by feedback is performed.

  In order to obtain the total reflection return light quantity characteristic as shown in FIG. 6, when the gap is zero, the optical disk 50 and the SIL 61 are completely parallel, that is, between the optical disk 50 and the SIL 61, as shown in FIG. Must be controlled so that the tilt of the lens becomes zero.

  However, as shown in FIG. 8, when the optical disk 50 and the end surface of the SIL 61 are in contact with each other in the initial state where the tilt exists, the total reflected return light amount is zero even when the gap length becomes zero, as shown in FIG. In other words, the gap length and the total reflected return light amount have a non-linear relationship. For this reason, it is impossible to accurately adjust the gap.

  However, even when there is a tilt in the initial state, as shown in FIG. 10, in the region 101 where the gap length and the total reflected return light amount have a linear relationship, gap servo based on linear characteristics is possible. .

  In the optical disc apparatus 1, when performing the gap control to obtain the target gap length, the gap control is performed so that the gap length once becomes a predetermined value, for example, 50 nm, and the tilt of the SIL 61 is adjusted at this gap length. After adjusting the tilt of the SIL 61 in this gap length, gap control is performed so as to obtain a final gap length of, for example, 30 nm.

  In this case, in the total reflected return light amount, the gap servo start threshold for determining the near field state and starting the gap servo, the gap servo target value for tilt correction for performing the tilt correction, and the final gap The final gap servo target value for the length is set. In the optical disc apparatus 1, the SIL 61 is brought close to the optical disc 50, and the gap servo is started at the moment when the total reflected return light amount falls below the gap servo start threshold, so that the total reflected return light amount matches the tilt correction gap servo target value. Control to maintain the SIL 61 is performed. Then, the tilt of the SIL 61 is corrected with the tilt correction gap servo target value, and thereafter, control is performed so that the total reflected return light amount becomes the final gap servo target value. The tilt correction gap servo target value may be the same value as the gap servo start threshold, but is set to a value larger than the final gap servo target value.

  In the optical disc apparatus 1, when such gap servo is performed, the total reflected return light amount and the gap servo switch are input to the data processing unit 73. This gap servo switch is a signal that is input to the data processing unit 73 based on, for example, that an optical disk is loaded in the optical disk apparatus 1, but is not limited thereto.

  The data processing unit 73 sets a gap servo start threshold and compares the input total reflected return light amount with the gap servo threshold. The gap servo start threshold is set to a value larger than the final gap servo target value in the near field region. For example, when the comparator compares the total reflected return light amount with the gap servo threshold value and the total reflected return light amount is larger than the gap servo start threshold value, that is, when the SIL 61 is at the far field distance, the data processing unit 73 is low. When the total reflected return light amount is smaller than the gap servo start threshold value, that is, when the SIL 61 is at the near field distance, High is output, and the switch is turned ON when the output of the comparator becomes High. The gap servo may be started.

  Further, the data processing unit 73 sets a tilt correction gap servo target value. When the gap servo is started, the data processing unit 73 adds the tilt correction gap servo target value to the total reflected return light amount voltage (approach voltage) at the start of the gap servo, and the target value for tilt correction such that the gap is, for example, 50 nm. Servo voltage is output so that The data processing unit 73 includes, for example, a low-pass filter, and generates an approach voltage when the gap servo switch is low-passed by the low-pass filter, so that the condensing element 22 can be made to approach the optical disc 50 smoothly based on the approach voltage. The driver 74 is controlled. This gap servo is started when the approach voltage reaches the final voltage value.

  In the optical disc 1, the initial position of the SIL 61 is set so that the speed of the light collecting element 22 becomes substantially zero at the position of the SIL 61 when the gap servo is started. That is, the distance between the optical disc 50 and the end surface of the SIL 61 is set in advance and the final voltage value is set so that the speed of the SIL 61 becomes substantially zero at the position of the SIL 61 when the gap servo is started. . The reason why such a setting is made is to prevent the SIL 61 from colliding with the disk 50 when there is an initial speed at the start of the gap servo. This initial position is in the far field from the optical disc 50. As described above, by setting the initial positions of the optical disc 50 and the SIL 61 in advance, the control of the approaching operation of the SIL 61 and the control of the gap servo can be performed independently, and a relatively simple configuration. It becomes possible to perform gap servo.

  The gap servo is described in, for example, “T. Ishimoto et al.,“ Gap Servo System for a Biaxial Device Using an Optical Gap Signal in a Near Field Readout System ”, Japanese Journal Applied Physics, Vol. 42, pp 2719-2724 ( 2003) ”, it is possible to use various methods such as a method of hierarchically performing gap servo from the far field to the near field using a biaxial actuator.

  The data processing unit 73 starts the gap servo, and performs tilt control for correcting the tilt of the SIL 61 with respect to the optical disc 50 when the approach voltage reaches the tilt correction gap servo target value. Here, the tilt control method in the present embodiment will be described in detail.

In FIG. 1, when the arrow r is a radial direction (radial direction) and the arrow t perpendicular to the arrow r is a tangential direction (tangential direction of the recording track) with respect to the photo detector 24 which is the second light receiving unit, The tilt error signal is calculated by Expression (2).
GES (r) = GES11 + GES12− (GES21 + GES22) (2)

In addition, the tilt error signal in the tangential direction is calculated by Equation (3).
GES (r) = GES11 + GES22− (GES12 + GES21) (3)

  The data processing unit 73 generates a tilt error signal based on the results of the mathematical formulas (2) and (3), and sends the radial tilt control signal Srs and the tangential tilt control signal Sts via the driver 74. To the biaxial actuator 63. Thereby, in the optical disc apparatus 1, the tilt of the SIL 61 with respect to the optical disc 50 is corrected.

  Note that the tilt control method of the SIL 61 with respect to the optical disc 50 is such that the gap error signal is received by a four-divided photodetector and the push-pull signals in the radial direction and the tangential direction are detected and the tilt control signals are detected. In addition to the method of correcting radial tilt and tangential tilt, various methods such as a method of correcting tilt using a multi-beam can be applied.

  After the tilt of the SIL 61 with respect to the optical disk 50 is corrected, as shown in FIG. 11, the gap length and the total reflected return light amount have a linear relationship. For this reason, the data processing unit 73 switches the target value in the gap servo from the tilt correction gap servo target value to the final gap servo target value, for example, from the current gap length of 50 nm to the final value of 30 nm, for example. Control the gap to the target value. In addition, this switching process may be switched in a step shape, for example, or may be switched in a non-linear manner.

  As described above, in the optical disc apparatus 1 in the present embodiment, the gap is controlled so that the total reflected return light amount becomes the tilt correction gap servo target value, and under that, control for correcting the tilt of the SIL 61 with respect to the optical disc 50 is performed. Then, the final gap length is controlled.

  FIG. 12 is a diagram showing the results of actual measurement of GES when the final target value of the gap is 30 nm and the tip diameter of the SIL 61 is 40 μm. In this case, as shown in FIG. 13, the tilt margin calculated by ± 2 × g / D using the gap g and the tip diameter D of the SIL 61 is ± 0.075 rad = ± 1.3 mrad.

  As shown in FIG. 12A, a tilt of 1.56 mrad occurs in the initial state. The gap error indicates non-linearity, and if the final gap is controlled to 30 nm as it is, 1.56 mrad> 1.3 mrad, and the SIL 61 collides with the optical disc 50.

  Therefore, as described above, as shown in FIG. 12B, first, the gap is controlled to 50 nm (step S1), and the control is performed so that the tilt is zero (step S2). Control is performed to set the gap to 30 nm (step S3).

  As described above, in the optical disc apparatus 1 in the present embodiment, the gap is controlled so that the total reflected return light amount becomes the tilt correction gap servo target value, and under that, control for correcting the tilt of the SIL 61 with respect to the optical disc 50 is performed. After that, by controlling to the final gap length, the SIL 61 can be controlled to the final gap position without colliding with the optical disc 50 at the time of pulling, and a stable gap servo can be realized. This makes it possible to record and reproduce data on a stable near-field optical disk.

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

It is a figure which shows the structure of the optical disk apparatus in one embodiment to which this invention is applied. It is a figure which shows the condensing element and optical disk in an optical head from a side surface. (A) is a figure which shows the gap of an optical disk and the end surface by the side of the optical disk of SIL, (B) is a figure which shows the change of the total reflected return light quantity with respect to a gap. It is a graph which shows the change of the gap error signal amount with respect to a gap. It is a block diagram which shows the internal structure of a control part. It is a figure for demonstrating the relationship between gap length and a total reflection return light quantity. It is a figure which shows the condensing element and optical disk in an optical head from a side surface. It is a figure which shows the condensing element and optical disk in an optical head from a side surface. It is a figure for demonstrating the relationship between gap length and a total reflection return light quantity. It is a figure for demonstrating the relationship between gap length and a total reflection return light quantity. It is a figure for demonstrating the relationship between gap length and a total reflection return light quantity. It is a figure which shows the result of having actually measured GES by making the final target value of a gap into 30 nm and making the tip diameter of SIL into 40 micrometers. It is a figure for calculating a tilt margin.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Optical disk apparatus, 10 Optical head, 11 Laser diode, 12, 13 Collimator lens, 14 Anamorphic prism, 15 Polarization beam splitter, 16 1/4 wavelength plate, 17 Chromatic aberration correction lens, 18 Expansion lens, 19 Beam splitter, 21 Collection Optical lens, 22 Condensing element, 23, 24, 28 Photo detector, 25 Auto power controller, 26 Laser diode driver, 27 Control unit

Claims (10)

An optical recording / reproducing method for recording and / or reproducing data by irradiating an optical recording medium with a near-field light from a near-field light irradiation unit,
A first gap control step of performing gap servo so that a gap between the optical recording medium and the near-field light irradiation unit becomes a first gap length in the near-field,
A tilt control step of correcting the tilt of the near-field light irradiation unit with respect to the optical recording medium while maintaining the gap controlled to the first gap length in the first gap servo step;
And a second gap control step of performing gap servo so that a gap between the optical recording medium and the near-field light irradiation unit becomes a second gap length for performing data detection by the near-field light. An optical recording / reproducing method.   In the first gap control step, gap servo is performed so that the total reflected return light amount from the near-field light irradiation unit becomes a first target value that is a total reflected return light amount corresponding to the first gap length. After the tilt of the near-field light irradiating unit with respect to the optical recording medium is corrected in the tilt control step, the total reflected return light amount is changed from the first target value to the first target value in the second gap control step. 2. The optical recording / reproducing method according to claim 1, wherein the gap servo is performed so that the second target value is the total reflected return light amount corresponding to the gap length of 2.   3. The optical recording / reproducing method according to claim 2, wherein the first target value is larger than the second target value.   2. The optical recording / reproducing method according to claim 1, wherein the near-field light irradiation unit is a solid immersion lens. An optical recording / reproducing apparatus that records and / or reproduces data by irradiating an optical recording medium with near-field light,
A light source that emits light;
A near-field light irradiating unit that irradiates the optical recording medium with light emitted from the light source as near-field light;
Recording / reproducing means for recording and / or reproducing data on the optical recording medium;
A light receiving means for receiving the total reflection return light of the light emitted from the light source;
Control means for controlling a gap between the optical recording medium and the near-field light irradiation unit;
A tilt control means for controlling the tilt of the near-field light irradiation unit with respect to the optical recording medium,
The gap control unit performs gap servo so that a gap between the optical recording medium and the near-field light irradiation unit becomes a first gap length in the near field, and the tilt control unit includes the first gap control. The tilt of the near-field light irradiating unit with respect to the optical recording medium is corrected in a state where the gap controlled to the first gap length by the means is maintained, and the gap control means adjusts the tilt by the tilt control means. After the correction, the gap servo is performed so that the gap between the optical recording medium and the near-field light irradiation unit becomes a second gap length for performing data detection by the near-field light. Recording / playback device.   The gap control means performs gap servo so that the total reflected return light amount from the near-field light irradiating unit becomes a first target value that is a total reflected return light amount corresponding to the first gap length, and the tilt control is performed. After the tilt of the near-field light irradiation unit with respect to the optical recording medium is corrected by the control unit, the gap control unit corresponds to the total gap return light amount from the first target value to the second gap length. 6. The optical recording / reproducing apparatus according to claim 5, wherein gap servo is performed so as to be a second target value which is a total reflected return light amount. The light receiving means includes: a first light receiving unit that receives total reflected return light from the optical recording medium of light emitted from the light source; and a total light from the near-field light irradiating unit of light emitted from the light source. A second light receiving portion for receiving the reflected return light,
The recording / reproducing means records and / or reproduces data with respect to the optical recording medium based on the amount of total reflected return light received by the first light receiving unit,
The tilt control means is configured to detect a relative relationship between the optical recording medium and the near-field light irradiation unit based on a plurality of gap detection signals generated from detection signals detected in a light receiving region obtained by dividing the second light receiving unit into a plurality of parts. To detect a typical tilt,
The optical recording / reproducing apparatus according to claim 5, wherein the gap control unit performs the gap control based on a light amount of total reflection return light received by the second light receiving unit. An optical head that records and / or reproduces data by irradiating an optical recording medium with near-field light,
A light source that emits light;
A near-field light irradiating unit that irradiates the optical recording medium with light emitted from the light source as near-field light;
Recording / reproducing means for recording and / or reproducing data on the optical recording medium;
A light receiving means for receiving the total reflection return light of the light emitted from the light source;
Control means for controlling a gap between the optical recording medium and the near-field light irradiation unit;
A tilt control means for controlling the tilt of the near-field light irradiation unit with respect to the optical recording medium,
The gap control unit performs gap servo so that a gap between the optical recording medium and the near-field light irradiation unit becomes a first gap length in the near field, and the tilt control unit includes the first gap control. The tilt of the near-field light irradiating unit with respect to the optical recording medium is corrected in a state where the gap controlled to the first gap length by the means is maintained, and the gap control means adjusts the tilt by the tilt control means. After the correction, the gap servo is performed so that the gap between the optical recording medium and the near-field light irradiation unit becomes a second gap length for performing data detection by the near-field light. head.   The gap control means performs gap servo so that the total reflected return light amount from the near-field light irradiating unit becomes a first target value that is a total reflected return light amount corresponding to the first gap length, and the tilt control is performed. After the tilt of the near-field light irradiation unit with respect to the optical recording medium is corrected by the control unit, the gap control unit corresponds to the total gap return light amount from the first target value to the second gap length. 9. The optical head according to claim 8, wherein gap servo is performed so that the second target value which is a total reflected return light amount is obtained. The light receiving means includes: a first light receiving unit that receives total reflected return light from the optical recording medium of light emitted from the light source; and a total light from the near-field light irradiating unit of light emitted from the light source. A second light receiving portion for receiving the reflected return light,
The recording / reproducing means records and / or reproduces data with respect to the optical recording medium based on the amount of total reflected return light received by the first light receiving unit,
The tilt control means is configured to detect a relative relationship between the optical recording medium and the near-field light irradiation unit based on a plurality of gap detection signals generated from detection signals detected in a light receiving region obtained by dividing the second light receiving unit into a plurality of parts. To detect a typical tilt,
The optical head according to claim 8, wherein the gap control unit performs the gap control based on a light amount of total reflection return light received by the second light receiving unit.

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