JP2009170011A - Optical pickup and optical recording and reproducing device using the same, and near-field optical recording and reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow recording and reproduction using near-field light for an optical recording medium including two recording layers. <P>SOLUTION: An optical pickup 30 includes a near-field optical system irradiating the optical recording medium with the near-field light. The near-field optical system is an objective lens 20 using a solid immersion lens 22. The objective lens 20 is adjusted to obtain the minimum spherical aberration in a focusing state on one layer L1 from among the recording layers L0, L1 of the optical recording medium. A focus adjustment mechanism 10 for performing the adjustment of the focal position by making incident light into parallel light or non-parallel light is provided. An aberration correction means 7 correcting the spherical aberration generated due to the movement of the focal position is provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical pickup that performs at least one of recording and reproduction by irradiating an optical recording medium with near-field light, an optical recording / reproducing apparatus using the optical pickup, and a near-field optical recording / reproducing method.

In recent years, in order to achieve high recording density and high resolution in information recording media such as optical disks, magnetic disks, and optical memory cards, a near field in which light leaks from the interface when the distance between objects is below a certain distance ( A recording / reproducing system using near-field light (also referred to as evanescent wave) has attracted attention.
Optical recording using a solid immersion lens (SIL), a solid immersion mirror (SIM), a waveguide structure, etc. as a method for recording and reproducing by irradiating an information recording medium with near-field light A reproduction method has been proposed (see, for example, Patent Document 1 and Non-Patent Document 1). This recording / reproducing method using near-field light uses a near-field light irradiation means such as SIL having a numerical aperture NA exceeding 1 for a high-density information recording medium, and the distance between the lens and the surface of the optical recording medium. Is a technique for performing recording and reproduction in close proximity to the extent that an evanescent wave is generated.

As a high-density optical recording medium for recording and reproducing using near-field light, a reflective film made of Al or the like, a dielectric layer made of SiO ₂ or the like on a substrate made of glass or polycarbonate (PC), GeSbTe, or the like Corresponding to recording information on a phase change recording type optical recording medium having a structure in which a dielectric layer made of SiO ₂ or the like is sequentially laminated, or on a substrate made of glass or PC A read-only optical recording medium in which pits are formed and a reflective layer made of Al or the like is formed thereon has been proposed (see, for example, Non-Patent Documents 2 and 3), other magneto-optical recording media, Magnetic recording media using optically assisted magnetic recording are also being studied.

In addition, when a near-field light irradiation unit such as SIL is used, it is reported that the distance between the surface and the surface of the information recording medium, that is, the so-called gap, is preferably 1/10 or less of the wavelength of the light to be irradiated. (For example, refer nonpatent literature 4).
For this reason, various studies have been made on a technique for accurately controlling the gap, a skew control technique for suppressing a collision when the SIL is moved close to the information recording medium (for example, Patent Documents). 2 and 3).

Japanese Patent Laid-Open No. 5-189796 I. Ichimuraet al., “Near-Field Phase-Change Optical Recording of 1.36 Numerical Aperture”, Japanese Journal of Applied Physics, Vol.39, pp.962-967 (2000) M. Shinodaet al., “High Density Near-Field Optical Disc Recording”, Digest of ISOM2004, We-E-03 M. Furukiet al., “Progress in Electron Beam Mastering of 100Gb / inch2 Density Disc”, Japanese Journal of Applied Physics Vol.43, pp.5044-5046 (2004) K. Saito et al., “A Simulation of Magneto-Optical Signals in Near-Field Recording”, Japanese Journal of Applied Physics, Vol.38, pp.6743-6749 (1999) JP 2001-76358 A JP 2006-344351 A

  As described above, in the recording / reproducing system using near-field light, the other handling is the same as that of the conventional information recording medium except that the distance between the lens and the surface of the information recording medium is very small. Is possible. Therefore, in order to achieve a higher recording density, it is possible in principle to perform recording and reproduction using a near-field light on a multilayer optical recording medium in which recording layers are laminated.

  However, since the spherical aberration caused by the small optical distance in the medium is proportional to the fourth power of the numerical aperture NA, this spherical aberration is increased in the near-field optical system that achieves a large numerical aperture NA. Therefore, in reality, it is not possible to correct spherical aberration by simply adopting an optical system that focuses on a plurality of recording layers. In order to solve this, there is a problem that a very complicated design such as changing the thickness of the solid immersion lens is required.

  In particular, in the recording / reproducing method using near-field light, since the numerical aperture NA is originally high, very high processing accuracy and assembly accuracy are required. In particular, in order to enable recording and reproduction with respect to a plurality of recording layers, the shape of the solid immersion lens, the shape of the aspherical lens constituting the objective lens in combination with this, the physical distance between these two lenses, etc. It must be adjusted with high accuracy. As described above, when recording / reproduction is performed on an optical recording medium having a multi-layered recording layer, such adjustment is required for each recording layer. Therefore, it is considered very difficult to employ a mechanism capable of adjusting these in a practical optical pickup or optical recording / reproducing apparatus.

  In view of the above problems, the present invention has a plurality of recording layers in an optical pickup and optical recording / reproducing apparatus having a near-field optical system without increasing the adjustment accuracy of the near-field optical system using a solid immersion lens. It is an object to enable recording and reproduction on an information recording medium.

  In order to solve the above problems, an optical pickup according to the present invention includes a light source, a near-field optical system that irradiates the optical recording medium with near-field light, a light detection unit that detects return light from the optical recording medium, and light detection. A control unit that generates a control signal based on a detection signal from the unit, a drive unit that drives the near-field optical system to a predetermined position with respect to the optical recording medium, and a focus that is adjusted to a plurality of recording layers of the optical recording medium And a aberration correction mechanism that corrects spherical aberration caused by movement of the focal length.

  According to the present invention, in the optical pickup described above, a gap control signal for controlling the distance between the near-field optical system and the outermost surface of the optical recording medium, and a focus control signal corresponding to the position of each recording layer of the optical recording medium are provided. It is desirable that the control unit generates the gap control signal and outputs the gap control signal to the driving unit that drives the near-field optical system, and outputs the focus control signal to the focus adjustment mechanism.

  Furthermore, the present invention provides the optical pickup described above, wherein the near-field optical system is an objective lens using a solid immersion lens, and the objective lens is focused on one of the recording layers of the optical recording medium. Desirably, the spherical aberration is adjusted to be minimized.

  In the optical pickup described above, the focus adjustment mechanism may be configured so that incident light is parallel light when performing recording or reproduction on a recording layer whose objective lens is adjusted so that spherical aberration is minimized. It is desirable that the focal position is adjusted by using incident light as non-parallel light when performing recording or reproduction on other recording layers.

  An optical recording / reproducing apparatus according to the present invention includes an optical pickup, an optical recording medium mounting unit, and a drive unit that moves the optical recording medium mounting unit relative to the optical pickup. The optical pickup is controlled based on a light source, a near-field optical system that irradiates the optical recording medium with near-field light, a light detection unit that detects return light from the optical recording medium, and a detection signal from the light detection unit. A control unit that generates a signal, a drive unit that drives the near-field optical system to a predetermined position with respect to the optical recording medium, a focus adjustment mechanism that adjusts the focus on a plurality of recording layers of the optical recording medium, An aberration correction mechanism for correcting spherical aberration generated by movement.

  In the near-field optical recording / reproducing method according to the present invention, the near-field optical system includes an objective lens using a solid immersion lens, and the objective lens is focused on one of the recording layers of the optical recording medium. In this state, the spherical aberration is adjusted to be minimal, and when recording or reproducing on the recording layer, the incident light is made parallel light and when recording or reproducing on the other recording layer In this case, the focal position is adjusted by making the incident light non-parallel, and the spherical aberration caused by the movement of the focal position is corrected.

As described above, in the optical pickup of the present invention and the optical recording / reproducing apparatus using the same, the light source, the near-field optical system for irradiating the optical recording medium with the near-field light, and the return light from the optical recording medium are detected. A light detection unit, a control unit that generates a control signal based on a detection signal from the light detection unit, a drive unit that drives the near-field optical system to a predetermined position with respect to the optical recording medium, and an optical recording medium A focus adjustment mechanism that adjusts the focus on a plurality of recording layers and an aberration correction mechanism that corrects spherical aberration caused by movement of the focal length are provided.
As described above, by providing the focus adjustment mechanism for adjusting the focus on the plurality of recording layers of the optical recording medium and the aberration correction mechanism separately from the drive unit that drives the near-field optical system, the near-field optical system can be Spherical aberrations that occur while adjusting the focal position for multiple recording layers of an optical recording medium while maintaining a predetermined distance from the outermost surface of the recording medium, that is, a minute distance that generates near-field light. Can be suppressed.

  In the optical pickup of the present invention, the control unit includes a gap control signal for controlling the distance between the near-field optical system and the outermost surface of the optical recording medium, and a focus control signal corresponding to the position of each recording layer of the optical recording medium. In the same manner, the gap control signal is output to the drive unit that drives the near-field optical system, and the focus control signal is output to the focus adjustment mechanism. It is possible to adjust the focal position on the desired recording layer with high accuracy while maintaining high accuracy.

  Further, in the optical pickup of the present invention, the near field optical system is an objective lens using a solid immersion lens, and the spherical aberration is in a state where the objective lens is focused on one of the recording layers of the optical recording medium. By adjusting so as to be the minimum, it is possible to correct the spherical aberration only when the focal position is adjusted to a recording layer other than the recording layer. In other words, it is not necessary to adjust the shape of the sled and the optical lens combined therewith and the distance between the lenses corresponding to each recording layer of the optical recording medium, and the aberration correction mechanism can be simplified. .

  Further, in the optical pickup of the present invention, the focus adjustment mechanism uses the incident light as parallel light when performing recording or reproduction on the recording layer in which the objective lens is adjusted so that the spherical aberration is minimized. When the recording layer is recorded or reproduced, the focal position is adjusted by making the incident light non-parallel light. It is possible to satisfactorily adjust the focal position on the desired recording layer while reliably maintaining the gap.

  Further, according to the near-field optical recording / reproducing method of the present invention, similarly, the focal position adjustment to the plurality of recording layers of the optical recording medium is favorably performed while maintaining the gap with the optical recording medium of the near-field optical system. Thus, it is possible to satisfactorily perform recording and reproduction on an optical recording medium having a plurality of recording layers.

  According to the present invention, it is possible to perform recording and reproduction on an information recording medium having a plurality of recording layers without increasing the adjustment accuracy of a near-field optical system using a solid immersion lens.

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

  FIG. 1 is a schematic configuration diagram of an optical recording / reproducing apparatus 100 including an optical pickup device 30 according to an embodiment of the present invention. The optical recording / reproducing apparatus of the present invention can be applied to a recording / reproducing apparatus that performs recording and reproduction, a reproduction-only apparatus, and can also be applied to a recording apparatus. Further, the optical recording medium that is symmetrical in the optical pickup and the optical recording / reproducing apparatus of the present invention may be of any recording mode as long as the recording layer is multi-layered. The present invention can be applied to an optical recording medium, an optical recording medium for recording / reproduction having a plurality of phase change recording films, and the like.

  In the example shown in FIG. 1, as the near-field optical system 20, a hemispherical or super hemispherical solid immersion lens (SIL) 21 disposed on the optical recording medium 200 side, and an optical lens 22 made of an aspherical lens or the like The case where an objective lens is comprised from is shown. Although FIG. 1 shows a super hemispherical SIL, it may be a hemispherical SIL. The optical pickup device 30 includes a power control unit 1, a light source 2 such as a laser diode, a collimating lens 3, a polarization beam splitter 4, a ¼ wavelength plate 5, a mirror 6, for example, in a direction orthogonal to the optical axis indicated by an arrow a. A focus correction mechanism 10 such as an expander composed of a movable aberration correction mechanism 7, movable lens groups 8 and 9, a near-field optical system 20, and a condensing lens disposed on a branch optical path of the beam splitter 4. 13 and a photodetection unit 14 such as a quadrant photodiode. Furthermore, it has the control part 15 which calculates the detection signal by the photon detection part 14. FIG. The control unit 15 generates control signals for controlling the driving unit 11, the focus adjustment mechanism 10, and the aberration correction mechanism 7 of the near-field optical system 20, that is, the gap control signal Sg, the focus control signal Sf, and the aberration correction signal Sa. The control unit 15 may generate the tilt control signal St for controlling the tilt of the SIL 22 with respect to the optical recording medium 200 and output the tilt control signal St to the drive unit 11.

  The optical recording / reproducing apparatus 100 further includes a mounting unit 25 for mounting an optical recording medium 200 such as a disk, and the mounting unit 25 is rotated around, for example, a one-dot chain line Cs as a rotation axis so A drive unit 26 that relatively moves the field optical system 20 and the optical recording medium 200 is provided.

  In this configuration, at the time of recording, light whose output is controlled by the power control unit 1 is emitted from the light source 2, converted into parallel light by the collimating lens 3, transmitted through the beam splitter 4, reflected by the mirror 5, and corrected for aberrations. When the mechanism 7 is disposed on the optical path, the light passes through the aberration correction mechanism 7, the focal position is adjusted by the focus adjustment mechanism 10, and enters the near-field optical system 20. For example, the power control unit 1 controls the output of the light source 2 in accordance with recording information from an information storage unit (not shown) during recording. During reproduction, output control from the power control unit 1 may be omitted, and the output of the light source 2 may be constant. When configured as a reproduction-only device, the power control unit 1 may be omitted. The near-field optical system 20 irradiates the target recording layer of the optical recording medium 200 with the incident light L using near-field light. The return light reflected from the optical recording medium 200 is reflected by the mirror 5, reflected by the beam splitter 4, and condensed on the light detection unit 14 by the condenser lens 13.

Part of the light detected by the light detection unit 14 is output as an RF (high frequency) signal S _RF corresponding to the recording information of the optical recording medium 200 during reproduction. On the other hand, the return light from the predetermined recording layer L 1 or L 2 of the optical recording medium 200 is input to the control unit 15 that generates a signal for controlling the driving unit 11 of the near-field optical system 20. The control unit 15 generates a gap control signal Sg and a tilt control signal St and outputs them to the drive unit 11 that drives the near-field optical system 20. The drive unit 11 is composed of, for example, a biaxial actuator including a voice coil motor, a triaxial actuator, or the like. The gap control drive unit and the tilt control drive unit may be provided separately, and a control signal may be input to each drive unit.

  On the other hand, the control unit 15 generates a focus control signal Sf corresponding to each recording layer L1 or L2 based on the return light from the optical recording medium 200 and outputs the focus control signal Sf to the focus adjustment mechanism 10. As the recording layer L1 or L2 is selected, whether the aberration correction mechanism 7 is arranged on the optical path as necessary, or whether the movement out of the optical path as indicated by the arrow a is performed is an aberration to the drive unit. A correction signal Sa is output from the control unit 15 to the aberration correction mechanism 7. As this signal Sa, a signal for selecting a recording layer may be used substantially.

  In this optical recording / reproducing apparatus 100, the optical recording medium 200 is mounted on the drive unit 26 that is rotationally driven as described above, and for example, a horizontal movement mechanism in which the optical pickup device 30 moves in parallel along the recording surface of the optical recording medium 200. (Not shown). Then, the near-field light irradiated from the near-field optical system 20 is scanned along the recording track on the disk surface of the optical recording medium 200, for example, spirally or concentrically by the interlocking of the horizontal movement mechanism and the drive unit 26. The configuration.

  FIG. 2 is a diagram schematically showing the relationship between the total reflected return light quantity with respect to the gap in the optical pickup device 30 using near-field light. FIG. 2A shows a gap between the end surface of the SIL 21 and the optical recording medium 200 in the near-field optical system 20 including the SIL 21 and the optical lens 22. FIG. 2B shows the relationship between the total reflected return light quantity and the gap. In this case, the total reflected return light amount is a return light amount of light (a component with an aperture ratio ≧ 1) incident on the end surface of the SIL 21 facing the optical recording medium 200 at an angle of total reflection.

  As shown in FIG. 2B, the far field region Ff, which is a region that is not in the near-field state, generally corresponds to a range in which the gap is 1/2 to 1/5 or more of the wavelength of the incident laser light. In the far field region Ff, all light is totally reflected at the SIL end face, so that the total reflected return light amount is constant. On the other hand, in general, a near-field state, that is, a near-field region Fn is obtained in a gap of 1/2 to 1/5 or less of the wavelength of incident laser light. In the example shown in FIG. 2B, as an example, when the wavelength of incident light is 405 nm, the total reflected return light amount is reduced below 70 nm. The relationship between the gap and the wavelength serving as the near field region is not uniform, and is about 1/2 to 1/5 as described above depending on the wavelength, the material configuration of the optical recording medium or SIL, and in some cases, 1/10 or less. Varies to the extent.

In the near field region Fn, evanescent coupling occurs between the SIL end face and the surface of the optical recording medium, and a part of the total reflected return light penetrates the SIL end face and is transmitted to the optical recording medium side. For this reason, the total reflected return light amount decreases. When the SIL completely contacts the optical recording medium, all the totally reflected return light is transmitted to the optical recording medium side, so that the total reflected return light amount becomes zero. Therefore, as shown in FIG. 2B, the relationship between the gap between the SIL end face and the optical recording medium and the total reflected return light amount is gradually reduced in the near field region Fn, which was constant in the far field Ff. When the gap is zero, the total reflected return light amount becomes zero. In the region where the total reflected return light amount decreases, there is a region where the relationship between the gap and the total reflected return light amount is linear as shown by being surrounded by a broken line l. Therefore, in this linear range, by using the total reflected return light amount as a gap control signal, the gap is kept constant, and recording and reproduction using near-field light, that is, high-density recording with a numerical aperture NA> 1. Playback is possible.
The gap control signal can be obtained by detecting the total reflected return light quantity as described above, or by a method using a change in polarization described later.

  On the other hand, a focus control signal is also generated using the return light. In the present invention, the focus control method is not particularly limited, and a general knife edge method, astigmatism method, or the like can be used. By driving the focus adjusting mechanism 10 based on this focus control signal, the focal position can be adjusted with respect to the target recording layer among the recording layers of the optical recording medium 200.

Next, with reference to FIG. 3 and FIG. 4, in the optical pickup and the optical recording / reproducing apparatus of the present invention, a more specific configuration example of the optical system when the focal position is adjusted to different recording layers of the optical recording medium will be described. To do.
3 and 4 schematically illustrate basic elements of the optical pickup according to the embodiment of the present invention, and show configuration diagrams in a state in which the focal positions are adjusted in the recording layers L1 and L2 of the optical recording medium 200, respectively. 3 and 4, the same reference numerals are given to the portions corresponding to those in FIG. In the present embodiment, when the SIL 21 and the optical lens 22 constituting the near-field optical system 20 adjust the focal position on the recording layer L1 closest to the outermost surface of the optical recording medium 200 having two recording layers. Shows an example in which the spherical aberration is minimized.

This is schematically shown in FIG. The shapes of the SIL 21 and the optical lens 22 supported by the holding body 23 are adjusted from the shapes indicated by the broken lines 21a and 22a so that the spherical aberration is minimized with the focal position adjusted to a specific recording layer. The distance between the SIL 21 and the lens 22 is also adjusted. In the present embodiment, after the SIL 21 and the optical lens 22 are adjusted and incorporated in the optical pickup 30 as described above, it is not necessary to adjust again in accordance with a state where the focal position is aligned with another recording layer.
In addition, the recording layer that minimizes the spherical aberration in advance is a recording layer that is close to the outermost surface of the optical recording medium. There is an advantage that the adjustment of is relatively simplified.

In this case, the basic operation when at least one of recording and reproduction with respect to the optical recording medium 200 will be described with reference to FIG.
First, when recording or reproducing is performed on the recording layer (first recording layer) L1 closest to the outermost surface of the optical recording medium 200, the aberration correction mechanism 7 uses the light source 2 as indicated by an arrow a1. To a position deviating from the optical path from the near-field optical system 20 to the near-field optical system 20. In this state, the light emitted from the light source 2 is converted into parallel light through the collimator lens 3 and is incident on the focus adjustment mechanism 10 through the polarization beam splitter 4.

  At this time, the aberration correction mechanism 7 is in a moving state deviating from the optical path and is not involved in incident light. The high NA objective lens composed of the SIL 22 and the optical lens 21 is adjusted in terms of the lens thickness of the SIL 22 and the distance between the SIL 22 and the optical lens 21 so as to focus on the first recording layer L1 with respect to parallel light incidence. . For this reason, the focus adjustment mechanism 10 passes through almost parallel light, and the light converged by the high NA can be focused on the first recording layer L1 in a state of almost no aberration.

  Next, with reference to FIG. 4, a basic operation when performing either recording or reproduction on the recording layer (second recording layer) L2 below the first recording layer L1 will be described. In this case, as shown in FIG. 4, the aberration correction mechanism 7 moves as indicated by an arrow a <b> 2 and is disposed at a predetermined position in the optical path from the light source 2 to the near-field optical system 20. As in the case of the first recording layer L 1, the light emitted from the light source 2 becomes parallel light and is then incident on the aberration correction mechanism 7 via the polarization beam splitter 4. The aberration correction mechanism 7 corrects the spherical aberration in the near-field optical system 20 generated when the focal position moves to the second recording layer L2. In this case, the aberration-corrected light is incident on the near-field optical system 20 as non-parallel light. Similarly, the light converged by the high NA is focused on the second recording layer L2 in a state of almost no aberration. Can be tied.

  Basically, the aberration correction mechanism 7 in the present embodiment is only required to generate an aberration opposite to the spherical aberration that occurs when one layer is recorded and reproduced. That is, in this example, as described above, in the case where the recording layer of the optical recording medium 200 is fixed to two layers, and the design value such as the correlation film thickness is fixed, a simple lens-shaped optical An element can also be used. In that case, since it acts in a reciprocating manner, the value is corrected by half.

  Further, the aberration correction mechanism 7 is not necessary when recording and reproducing the first recording layer in the present embodiment, and therefore, it is necessary to provide a drive mechanism that can be retracted from the optical path. On the other hand, it is also possible to apply an aberration correction mechanism that can be adjusted without movement, such as a phase correction element using liquid crystal, in which case the drive mechanism is not necessary. In this case, the aberration correction signal Sa shown in FIG. 1 is not output to the drive mechanism of the aberration correction mechanism 7, but is output to the aberration correction mechanism 7 including a phase correction element using liquid crystal.

An example in which the focus adjustment mechanism 10 used in the present embodiment is configured by a combination of a concave lens and a convex lens is shown. In this case, the focal position can be adjusted by changing the position of one lens. These combinations enable recording and reproduction operations on the second recording layer.
Further, as the other focus adjustment mechanism 10, it is of course possible to use an optical system that does not use a driving mechanism, such as a liquid lens using an electrowetting phenomenon.

  Furthermore, an optical system that combines the functions of the focus adjustment mechanism 10 and the aberration correction mechanism 7 is configured by adjusting the number, shape, and movement distance of each lens using a lens group having a movable mechanism, that is, a so-called beam expander. Is also possible.

In the example described above, an optical pickup and an optical recording / reproducing apparatus are configured by using one light source (that is, light of one wavelength). However, when performing near-field optical recording / reproducing, In some cases, light of different wavelengths is used. An embodiment of the optical recording / reproducing apparatus in this case will be described with reference to FIG. In FIG. 6, parts corresponding to those in FIG.
As shown in FIG. 6, in this optical pickup 30, a collimator lens 3, a polarization beam splitter 4, a quarter wavelength plate 5, an aberration correction mechanism 7, a focus adjustment mechanism 10, and a dichroic prism are provided on the light path of the light source 2. 45 is arranged. On the optical path reflected by the dichroic prism 45, the near-field optical system 20, that is, the optical lens 22 and the SIL 21 mounted on the drive unit 11 is disposed. A condensing lens 13 and a light detection unit 14 are disposed on the reflected light path by the return light of the polarization beam splitter 4.

In this case, light having a wavelength different from that for recording / reproducing light is used as so-called gap detection light for detecting the distance between the SIL 21 of the near-field optical system 20 and the surface of the optical recording medium 200. That is, in this case, a light source 40 having a wavelength different from that of the light source 2 is used, and a collimator lens 41, a beam splitter 42, a polarization beam splitter 43, A quarter-wave plate 44 is disposed, and light that has passed through the quarter-wave plate 44 enters the dichroic prism 45. The dichroic prism 45 is configured to reflect this light, and is disposed so that the reflected light is incident on the near-field optical system 20. A condensing lens 46 and a light detection unit 47 are disposed on the reflected light path by the return light of the beam splitter 42.
Moreover, the control part 15 into which the return light obtained from the light detection parts 14 and 47 is input is provided. A gap control signal Sg and a focus control signal Sf generated based on the return light in the control unit 15 are output to the drive unit 11 on which the near-field optical system 20 is mounted and the focus adjustment mechanism 10, respectively. Even in this case, a tilt control signal St for controlling the tilt of the SIL 21 may be output to the drive unit 11. Further, as the aberration correction signal Sa, for example, a signal for selecting the recording layer L1 or L2 of the optical recording medium 200 is output from the control unit 15 to the aberration correction mechanism 7.

In this configuration, the light emitted from the light source 2 is converted into parallel light by the collimating lens 3, passes through the polarization beam splitter 4, and passes through the quarter wavelength plate 5. When the aberration correction mechanism 7 is disposed on the optical path, the light is incident on the aberration correction mechanism 7 and the focus adjustment mechanism 10. The light whose aberration has been corrected by the aberration correction mechanism 7 as necessary is adjusted in focal length by the focus adjustment mechanism 10 and is incident on the dichroic prism 45. The light reflected by the dichroic prism 45 enters the near-field optical system 20, that is, the optical lens 22 and the SIL 21, and irradiates the optical recording medium 200 using the near-field light.
The light reflected from the recording surface of the optical recording medium 200 is reflected again by the dichroic prism 45 through the near-field optical system 20, and polarized through the focus adjustment mechanism 10, the aberration correction mechanism 7, and the quarter wavelength plate 5. A part of the light is reflected by the beam splitter 4 and condensed by the condenser lens 13 on the light detection unit 14 as a recording / reproducing signal and a focus control signal.

  On the other hand, the light emitted from the light source 40 enters the dichroic prism 45 via the collimating lens 41, the beam splitter 42, the polarizing beam splitter 43, and the quarter wavelength plate 44. The light having this wavelength is transmitted through the dichroic prism 45, and is combined with the light from the light source 2 in the dichroic prism 45, and the gap is detected in the optical recording medium 200 via the optical lens 22 and the SIL 21 of the near-field optical system 20. Irradiated as business light.

  The return light for gap detection passes through the dichroic prism 45, passes through the quarter-wave plate 44, and is almost reflected by the polarizing beam splitter 43. The light leaked from the polarizing beam splitter 45 is reflected by the beam splitter 42. The light can be reflected and detected by the light detection unit 47 via the condenser lens 46.

In this example, the gap is detected using the change in polarization described above. That is, when the gap between the optical recording medium and the near-field optical system, that is, the SIL is wide and the light is substantially totally reflected at the SIL end face, the polarization changes on the SIL surface. The light of the part leaks. On the other hand, when the optical recording medium is close to the SIL and the near-field light leaks and is close to normal reflection, the change in polarization is small, so the amount of light leaking through the polarization beam splitter 43 is small. Gap detection is performed using this difference, that is, a change in the total reflected return light quantity, and based on this, the control unit 15 generates a gap control signal Sg. By driving the drive unit 11 that holds the near-field optical system 20 based on the control signal Sg, the distance between the optical recording medium 200 and the near-field optical system 20 can be accurately held.
As the gap detection method, various other methods such as a method of detecting a change in capacitance can be employed.

As described above, even when photons having different wavelengths are used for gap control, the same effects as those of the embodiment shown in FIG. 1 can be obtained by applying the present invention.
That is, the control unit 15 outputs the gap control signal Sg, the focus control signal Sf, and the aberration correction signal Sa to the drive unit 11, the focus adjustment mechanism 10, and the aberration correction mechanism 7, respectively, so that the focus adjustment mechanism 10 and the aberration correction mechanism 7 are output. The operation mode is performed in the same manner as the embodiment shown in FIGS. Furthermore, the adjustment of the shape of the near-field optical system 20 and the lens interval is the same as in the embodiment shown in FIG. 5, so that the first recording layer L1 and the second recording layer L2 of the optical recording medium 200 are adjusted. Thus, it is possible to focus on each lens with almost no aberration.

  As described above, according to the present invention, even an optical recording medium that performs recording and reproduction using near-field light can be relatively easily adapted to a multilayer medium having multiple recording layers. Further, as a configuration of the optical pickup and the optical recording / reproducing apparatus, focus adjustment and aberration correction can be realized by a practical mechanism. Thereby, the capacity of the near-field optical recording medium can be increased.

  The present invention is not limited to the configuration described in the above-described embodiment, and various modifications and changes can be made without departing from the configuration of the present invention.

1 is a schematic configuration diagram of an optical recording / reproducing apparatus including an optical pickup according to an embodiment of the present invention. A and B are explanatory views of the total reflected return light amount. It is a schematic block diagram which shows the one operation | movement aspect of the optical pick-up which concerns on embodiment of this invention. It is a schematic block diagram which shows the one operation | movement aspect of the optical pick-up which concerns on embodiment of this invention. 1 is a schematic configuration diagram of a near-field optical system in an optical pickup according to an embodiment of the present invention. 1 is a schematic configuration diagram of an optical recording / reproducing apparatus including an optical pickup according to an embodiment of the present invention.

Explanation of symbols

  1. 1. Power control unit, 2. light source; Collimating lens, 4. 5. beam splitter, 5.4 wavelength plate, Mirror, 7; Aberration correction mechanism, 8,9. Optical lens, 10. 10. focus adjustment mechanism; Drive unit, 13. Condensing lens, 14. 15. light detection unit; Control unit, 20. Near-field optical system, 21. Solid immersion lens (SIL), 22. Optical lens, 25. Mounting part, 26. Drive unit, 30. Optical pickup, 40. Light source, 41. Collimating lens, 42. Beam splitter, 43. Polarizing beam splitter, 44.4 quarter wave plate, 45. Dichroic prism, 46. Condensing lens, 47. Light detection unit, 100. Optical recording / reproducing device

Claims (9)

A light source;
A near-field optical system for irradiating the optical recording medium with near-field light; and
A light detection unit for detecting return light from the optical recording medium;
A control unit that generates a control signal based on a detection signal from the light detection unit;
A drive unit that drives the near-field optical system to a predetermined position with respect to the optical recording medium;
A focus adjustment mechanism for adjusting the focus on a plurality of recording layers of the optical recording medium;
An optical pickup comprising: an aberration correction mechanism that corrects spherical aberration caused by movement of the focal length. A gap control signal for controlling the distance between the near-field optical system and the outermost surface of the optical recording medium and a focus control signal corresponding to the position of each recording layer of the optical recording medium are generated in the control unit,
The gap control signal is output to a driving unit that drives the near-field optical system,
The optical pickup according to claim 1, wherein the focus control signal is output to the focus adjustment mechanism. The near-field optical system is an objective lens using a solid immersion lens,
2. The optical pickup according to claim 1, wherein the objective lens is adjusted so that spherical aberration is minimized while focusing on one of the recording layers of the optical recording medium. The focus adjustment mechanism is
When performing recording or reproduction on the recording layer in which the objective lens is adjusted so that the spherical aberration is minimized, the incident light is made parallel light,
4. The optical pickup according to claim 3, wherein when performing recording or reproduction on another recording layer, the focal position is adjusted by making the incident light non-parallel light.   The objective lens using the solid immersion lens is characterized in that it is adjusted so as to minimize spherical aberration while being focused on the recording layer closest to the outermost surface of the optical recording medium. The optical pickup according to claim 4.   The optical pickup according to claim 1, wherein the aberration correction mechanism is provided with a drive unit that enables entry and exit into an optical path from the light source to the near-field optical system.   The optical pickup according to claim 1, wherein the aberration correction mechanism is driven based on a selection signal for selecting a recording layer of the optical recording medium. An optical pickup,
A mounting portion of an optical recording medium;
A drive unit that moves the mounting unit of the optical recording medium relative to the optical pickup;
The optical pickup is
A light source;
A near-field optical system for irradiating the optical recording medium with near-field light;
A light detection unit for detecting return light from the optical recording medium;
A control unit that generates a control signal based on a detection signal from the light detection unit;
A drive unit that drives the near-field optical system to a predetermined position with respect to the optical recording medium;
A focus adjustment mechanism for adjusting the focus on a plurality of recording layers of the optical recording medium;
An optical recording / reproducing apparatus comprising: an aberration correction mechanism that corrects spherical aberration caused by movement of a focal length. The near-field optical system is composed of an objective lens using a solid immersion lens.
Adjusting the objective lens so that the spherical aberration is minimized while focusing on one of the recording layers of the optical recording medium;
When performing recording or reproduction with respect to the recording layer, the incident light is made parallel light, and when performing recording or reproduction with respect to another recording layer, the incident light is made non-parallel light so that the focal position is obtained. Make adjustments
A near-field optical recording / reproducing method comprising correcting spherical aberration caused by movement of a focal position.

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