JP2008176855A - Optical pickup and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup and optical disk device in which detection accuracy of tracking errors is improved even for an optical disk having a plurality of recording layers. <P>SOLUTION: The optical pickup is provided with: a means for separating a laser beam emitted from a light source into two sub light beams; a means for projecting the separated light beams to the prescribed recording surface of an optical disk having a plurality of recording surfaces; a light receiving means receiving reflected light from the optical disk; and an optical member arranged on an optical path from the optical disk to the light receiving means, wherein a rough surface disturbing wave front of reflected light is provided at the optical member so that interference fringes of the sub light beams caused on the light receiving means by reflected light of the sub light beams form the prescribed recording surface and reflected light of a recording surface of other layer being different from the prescribed recording surface is decreased. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical disk device mounted on an electronic device such as a personal computer, a notebook computer, or a mobile terminal device, and an optical pickup suitably used for the optical disk device.

  The progress of technology for recording information such as music and movies on a disk-type optical recording medium as an external storage device of a personal computer is remarkable. As this optical recording medium, CD-R, CD-RW, DVD ± R, DVD ± Optical discs such as RW and DVD-RAM have been developed, and optical discs having a plurality of recording layers of two or more layers from the conventional optical disc having a single recording layer to further increase the storage capacity (eg, DVD ± R DL) The technology is progressing.

  Information is recorded on or reproduced from the optical disc by keeping the distance from a predetermined recording surface of the optical disc constant and following a predetermined recording track of the optical disc. The focus control for controlling the distance to the predetermined recording surface of the optical disc to be constant and the tracking control for controlling to follow the track recorded on the recording surface of the optical disc are the focus error from the reflected light from the optical disc. This is done by detecting signals and tracking error signals.

  As one method for detecting and tracking control this tracking error signal, the main beam (0th order diffracted light) used for signal recording / reproduction using the optical beam (diffraction grating) of the light beam emitted from the laser light source and the tracking error. The sub-light (± 1st order diffracted light) used for signal detection is separated into three beams, and the reflected light from the recording surface of the optical disk is received by a photodetector. A technique for performing tracking control is used.

  A configuration of a conventional optical pickup will be described with reference to the drawings.

  FIG. 10 is a diagram showing a schematic configuration of a conventional optical pickup.

  As shown in FIG. 10, the light beam emitted from the laser 102 is, by an optical member (diffraction grating) 124, main light (0th-order diffracted light) mainly used for recording and reproduction, and two sub-lights used for tracking control. (± first order diffracted light). The intensity of the main light (0th order diffracted light) and the ± 1st order diffracted light of the separated light beam is 1 / the intensity of the sub light (± 1st order diffracted light) with respect to the intensity of the main light (0th order diffracted light). It is set to about 10 to 1/20. The light beam separated by the diffraction grating 124 passes through the polarization beam splitter 122, is collimated by the collimator lens 121, and is focused on the recording surface 125 of the optical disk 101 by the objective lens 6.

  The reflected light focused on the recording surface 125 of the optical disc 101 passes through the objective lens 6 and the collimator lens 121, is reflected by the inclined surface 122a of the polarization beam splitter 122, passes through the main plane 122b of the polarization beam splitter 122, and is detected by the detection lens. The signal is detected by the detector 105 which is the reflected light receiving means through the light 123. A tracking error signal (TE) is calculated based on the two detected sub-light signals, and tracking control is performed to minimize TE.

  When the optical disc has two recording surfaces (L0 layer, L1 layer), not only the reflected light from the recording layer (self-recording layer) focused on the layer on which recording or reproduction is actually performed, but also the self-recording layer It is influenced by reflected light (stray light) from the recording surface of another layer different from the above.

  FIG. 11 is a diagram showing a schematic diagram of an optical system configuration of an optical pickup for an optical disc having two recording layers in a conventional configuration. FIG. 11A shows a configuration in which the L0 layer is focused. b) shows a configuration in which the L1 layer is focused.

  In FIG. 11A, the reflected light from the L0 layer which is the self-recording layer is irradiated with the main light (0th order diffracted light) on the detector 901 and the sub light (± 1st order diffracted light) on 902a and 902b. Further, the reflected light from the recording surface L1 layer different from the self-recording layer becomes stray light 903 and is irradiated so as to cover the whole detector of the main light and the sub light.

  In FIG. 11B, the reflected light from the L1 layer which is the self-recording layer is irradiated with the main light (0th order diffracted light) on the detector 904 and the sub light (± 1st order diffracted light) on 905a and 905b. Further, the reflected light from the L0 layer lower than the self-recording layer L1 becomes stray light 906 and is irradiated so as to cover the whole detector of the main light and the sub light. As described above, the intensity of the sub light (± 1st order diffracted light) is set to about 1/10 to 1/20 with respect to the intensity of the main light (0th order diffracted light). The intensity of the reflected light becomes weaker. Therefore, the stray light 903 and the stray light 906 may be regarded as having a large influence of the stray light of the reflected light of the main light (0th order diffracted light).

  The reflected light of the sub-light of the self-recording layer and the reflected light of the main light mainly from other layers cause light interference on the detector and are detected as interference fringes.

  FIG. 12 is a diagram showing interference between a self-recording layer having a conventional configuration and reflected light from another layer. The interference fringes cause fluctuations in the interference fringe fluctuation due to fluctuations due to fluctuations in wavelength, disc thickness, and interlayer spacing, and fluctuations in the tracking signal controlled by three beams.

As a technique for controlling the fluctuation of the tracking signal for an optical disc having a plurality of recording layers, for example, there is (Patent Document 1).
JP 2005-203090 A

  However, in the conventional technique, the following problems have occurred. That is, when the wave front of the reflected light from the recording layer and the reflected light from the recording surface of the other layer are incident on the main plane 122b of the polarization beam splitter 122 with different inclinations, the phases of the two beams match. In such a position, the intensity of light is increased to be in a bright state, while the intensity of light is decreased to be in a dark state, causing a problem that a clear interference fringe is generated in the light receiving sensor.

  This point will be described with reference to FIG.

  FIG. 13 is an explanatory diagram regarding the generation of conventional interference fringes.

  As shown in FIG. 13A, the reflected light from the self-recording layer travels in the polarization beam splitter 122 as a wavefront 701a inclined with respect to the main plane 122b, while the reflected light from the recording surface of the other layer. Travels in the polarization beam splitter 122 as a wavefront 702a having a different inclination with respect to the main plane 122b. The main plane 122b of the polarization beam splitter 122 is a plane having a mirror finish. Reflected light from the self-recording layer and reflected light from the recording surface of the other layer are incident on the main plane 122b with an inclination and pass through the main plane 122b of the polarization beam splitter 122 into the air. Then, after passing through the main plane 122b, the reflected light from the recording layer proceeds as a wavefront 701b having an inclination, while the reflected light from the recording surface of the other layer proceeds as a wavefront 702b having an angle to the detector 105. Irradiated.

  Since the main plane 122b of the polarization beam splitter 122 is a mirror surface, the wavefront of the reflected light 704 from the self-recording layer and the wavefront of the reflected light 703 from the recording surface of the other layer have different inclinations, respectively. , The starting points where the reflected light escapes from the main plane 122b are also aligned.

  Accordingly, as shown in FIGS. 13B and 13C, at the position where the phases of the two beams incident on the main plane 122b at a constant angle coincide with each other, the two waves 703 and 704 are added and become larger. The light intensity becomes strong and the bright stripe 706a is subtracted at the position where the two waves are out of phase, the light intensity becomes weak and the dark stripe 706b is obtained, and the light and dark states are aligned. There is a problem that a clear interference fringe is generated as in the three-dimensional model (d).

  In order to reduce the interference fringes, it is possible to add an optical member between the laser 102 and the optical disc 101 to diffract the reflected light from the other layers. There was a problem that the quality of reproduction deteriorated. Further, there are problems that the size of the apparatus is increased and the cost is increased due to the additional member.

  The present invention is an optical pickup that can be configured in a small size without specially adding an optical member, improves tracking error detection accuracy for an optical disc having a plurality of recording layers, and improves tracking control accuracy. And an optical disc apparatus.

  The present invention has been made in order to solve the above-described problems. A laser beam emitted from a light source is separated into main light and two sub-lights, and the separated light beam is a predetermined optical disc having a plurality of recording surfaces. Means for irradiating the recording surface, a light receiving means for receiving reflected light from the optical disc, and an optical member disposed on the optical path from the optical disc to the light receiving means, and reflecting sub-light from a predetermined recording surface The optical member is provided with a rough surface that disturbs the wavefront of the reflected light so as to reduce the interference fringes of the sub-light generated on the light receiving means by the light and the reflected light of the recording surface of another layer different from the predetermined recording surface. is there.

  The present invention reduces interference fringes of sub light generated on a light receiving means by reflected light of sub light from a predetermined self recording surface and reflected light (stray light) of a recording layer of another layer different from the predetermined self recording surface. By providing the optical member with a rough surface that disturbs the wavefront of the reflected light, the wavefront of the reflected light from the recording surface and the wavefront of the reflected light from the recording surface of the other layer pass through the polarization beam splitter and Since the starting positions of the adjacent positions that escape into the air can be made uniform when exiting, the starting position of the reflected light itself from the recording surface and the starting position of the reflected light itself from the recording surface of the other layer are also random. . As a result, since the starting position is random, the interference fringes in which both the reflected light from the recording surface and the reflected light from the recording surface of the other layer interfere on the detector are uneven in the bright and dark portions. Since the intensity change is random, the intensity change of the reflected light due to the interference fringes becomes invisible.

  Therefore, since the signal detection accuracy by the sub light for detecting the tracking error when used for the tracking control is improved, the tracking control when recording or reproducing the optical disk having a plurality of recording surfaces can be adjusted with high accuracy. It is possible to provide an optical pickup and an optical disc apparatus that are capable of performing the above.

  Further, there is provided an optical pickup and an optical disk apparatus in which interference fringes are made random by providing a rough surface on the polarization beam splitter, and no new optical member is added, so that the size of the apparatus is not increased and the cost is not increased by the additional optical member. Will be able to.

  The invention according to claim 1 is a means for separating laser light emitted from a light source into main light and two sub-lights, and means for irradiating a predetermined recording surface of an optical disc having a plurality of recording surfaces with the separated light beam; A light receiving means for receiving reflected light from the optical disk, and an optical member disposed on an optical path from the optical disk to the light receiving means, the reflected light of the sub-light from the predetermined recording surface, and the predetermined recording surface. The optical member is provided with a rough surface that disturbs the wavefront of the reflected light so as to reduce the interference fringes of the sub-light generated on the light receiving means by the reflected light of the recording surface of another different layer.

  According to this configuration, the interference fringes of the sub light generated on the light receiving means by the reflected light of the sub light from the predetermined self recording surface and the reflected light (stray light) of the recording surface of another layer different from the predetermined self recording surface By providing the optical member with a rough surface that disturbs the wavefront of the reflected light, the wavefront of the reflected light from the recording surface and the wavefront of the reflected light from the recording surface of the other layer pass through the polarization beam splitter. Since the starting positions of the adjacent positions that escape into the air can be made uneven when exiting into the air, the starting positions of the reflected light from the recording surface itself and the starting positions of the reflected light from the recording surface of other layers are also random. It becomes. As a result, since the starting position is random, the interference fringes in which both the reflected light from the recording surface and the reflected light from the recording surface of the other layer interfere on the detector are uneven in the bright and dark portions. Since the intensity change is random, the intensity change of the reflected light due to the interference fringes becomes invisible.

  Therefore, since the signal detection accuracy by the sub light for detecting the tracking error when used for the tracking control is improved, the tracking control when recording or reproducing the optical disk having a plurality of recording surfaces can be adjusted with high accuracy. It is possible to provide an optical pickup and an optical disc apparatus that are capable of performing the above.

  Further, there is provided an optical pickup and an optical disk apparatus in which interference fringes are made random by providing a rough surface on the polarization beam splitter, and no new optical member is added, so that the size of the apparatus is not increased and the cost is not increased by the additional optical member. Will be able to.

  According to a second aspect of the present invention, in the first aspect of the invention, the rough surface that disturbs the wavefront of the reflected light provided on the optical member has a surface roughness of 10 μm or more and 20 μm or less, and an arithmetic average roughness Ra of 10 μm or more. 2. The optical pickup according to claim 1, wherein the root mean square roughness Rq is 12 μm or more and 25 μm or less.

  According to this configuration, the roughness of the rough surface that disturbs the wavefront of the reflected light provided on the optical member is such that the arithmetic average roughness Ra of the surface roughness is 10 μm or more and 20 μm or less, and the root mean square roughness Rq of the surface roughness is Since the lower limit value is made larger than the mirror finish by setting it to 12 μm or more and 25 μm or less, the reflected light from the sub-light and the reflected light from the recording surface of the other layer can be made to have different wavefronts. The reflected light from the surface and the reflected light from the recording surface of the other layer pass through the rough surface provided on the optical member at different angles, and each has a different wavefront, and the reflected light on the light receiving means depends on the reflected light. Interference becomes random and the intensity change of interference fringes becomes random. As a result, the intensity change of the reflected light due to the interference fringes becomes invisible. Further, by setting the upper limit values to 20 μm for Ra and Rq to be 25 μm or less, when the reflected light from the self-recording layer passes through the optical member, it is scattered by the rough surface to restrict the decrease in the amount of light received by the light receiving means. be able to. Accordingly, the interference fringes of the sub light generated on the light receiving means by the reflected light of the sub light from the predetermined self recording surface and the reflected light of the recording surface of another layer different from the predetermined recording surface can be reduced. Thus, it is possible to provide an optical pickup capable of accurately adjusting tracking control when recording or reproducing with respect to an optical disc having a plurality of recording surfaces.

  According to a third aspect of the present invention, in the first aspect of the present invention, the optical member is a polarizing beam splitter, and the rough surface is provided on a main plane on the light receiving means side of the polarizing beam splitter.

  According to this configuration, the rough surface is provided on the main plane on the light receiving means side of the polarizing beam splitter, so that the light beam can pass through the rough surface of the polarizing beam splitter only once. It can be prevented that the intensity of the light beam generated when the recording medium is provided is deteriorated and the intensity of the light beam is deteriorated when recording or reproducing, and the quality of recording or reproducing is deteriorated. In addition, since the signal detection accuracy by the sub light for detecting the tracking error when used for tracking control is improved, the tracking control when recording or reproducing with respect to an optical disc having a plurality of recording surfaces can be adjusted with high accuracy. It is possible to provide an optical pickup and an optical disc apparatus that are capable of performing the above.

  According to a fourth aspect of the invention, in the first aspect of the invention, the optical member is provided with a rough surface on at least one of the optical paths from the optical disc to the light receiving means.

  According to this configuration, the optical member is provided with a rough surface at a position close to the detector by providing a rough surface on at least one of the optical path from the optical disk to the light receiving means, so that the light beam is provided with the rough surface of the polarization beam splitter. It can be configured to pass only once, and the intensity of the light beam is deteriorated when the intensity of the light beam is deteriorated, so that the quality of recording or reproduction can be prevented from being deteriorated. In addition, since the signal detection accuracy by the sub light for detecting the tracking error when used for tracking control is improved, the tracking control when recording or reproducing with respect to an optical disc having a plurality of recording surfaces can be adjusted with high accuracy. It is possible to provide an optical pickup and an optical disc apparatus that are capable of performing the above.

  According to a fifth aspect of the present invention, in the optical pickup according to the first to fourth aspects, the heights of the convex portions forming the rough surface provided on the optical member are different.

  According to this configuration, the height of each convex portion forming the rough surface provided on the optical member is different, so that the reflected light of the sub-light from the self-recording surface is different from the self-recording surface. The position at which each reflected light from the recording surface exits from the polarizing beam splitter into the air can be changed according to the height of the rough surface provided on the optical member. As a result, the reflected light of the sub-light from the self-recording surface and the reflected light of the recording layer of another layer different from the self-recording surface can be irradiated as different phases when irradiating the detector, so that the interference fringes are not aligned. To be able to. Therefore, since the signal detection accuracy by the sub light for detecting the tracking error when used for tracking control is improved, it is possible to accurately adjust the tracking control when recording or reproducing on an optical disc having a plurality of recording surfaces. An optical pickup and an optical disc device that can be used can be provided.

  According to a sixth aspect of the present invention, in the optical pickup according to the first to fourth aspects, the convex portions forming the rough surface provided on the optical member are randomly arranged.

  According to this configuration, the arrangement of the convex portions forming the rough surface provided on the optical member is made random so that the reflected light of the sub-light from the self-recording surface and the recording surface of another layer different from the self-recording surface The position at which each of the reflected light exits from the polarizing beam splitter into the air can be changed according to the difference in the arrangement of the rough surfaces provided on the optical member. As a result, the reflected light of the sub-light from the self-recording surface and the reflected light of the recording layer of another layer different from the self-recording surface can be irradiated as different phases when irradiating the detector, so that the interference fringes are not aligned. To be able to. Therefore, since the signal detection accuracy by the sub light for detecting the tracking error when used for tracking control is improved, it is possible to accurately adjust the tracking control when recording or reproducing on an optical disc having a plurality of recording surfaces. An optical pickup and an optical disc device that can be used can be provided.

  A seventh aspect of the present invention is an optical disc apparatus using the optical pickup according to any one of the first to sixth aspects. According to this configuration, the sub-light from a predetermined self-recording surface is provided. The rough surface that disturbs the wavefront of the reflected light on the optical member so as to reduce the interference fringes of the sub-light generated on the light receiving means by the reflected light of the recording layer and the reflected light (stray light) of the recording layer of another layer different from the predetermined self-recording surface When the wavefront of the reflected light from the recording surface and the wavefront of the reflected light from the recording surface of the other layer pass through the polarization beam splitter and escape into the air, the passing position of each reflected light is Random. As a result, since the passing position is random, the reflected light of the recording surface of the other layer different from the reflected light of the self recording surface becomes a random passing position. Interference fringes in which dark portions are aligned also become uneven in bright and dark portions, and the intensity change becomes random, so that the intensity change of reflected light due to the interference fringes becomes invisible.

  Therefore, since the signal detection accuracy by the sub light for detecting the tracking error when used for the tracking control is improved, the tracking control when recording or reproducing the optical disk having a plurality of recording surfaces can be adjusted with high accuracy. It is possible to provide an optical disc device capable of performing the above.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a perspective view of the optical disc device according to the first embodiment of the present invention, and FIG. 2 is an external view of the optical disc device according to the first embodiment of the present invention, with the top portion of the housing removed.

  1 and 2, the optical disc apparatus 1 includes a housing 2 and a tray 3. FIGS. 1 and 2 show a state in which the tray 3 is pulled out from the housing 2.

  The housing 2 is composed of a top 2a and a bottom 2b. An optical pickup module 4 is provided on the tray 3. The optical pickup module 4 includes an optical pickup 5 constituting an optical system, a spindle motor 4a for rotating the optical disk, and a circuit board 4c constituting a control circuit.

  The optical pickup 5 provided in the optical pickup module 4 records information on the optical disk mounted on the optical disk apparatus 1 and reproduces information from the optical disk, and approaches or moves away from the spindle motor 4a. That is, information is recorded and reproduced by moving in the radial direction of the optical disk and moving to a predetermined recording or reproducing position.

  The spindle motor 4a has an optical disk mounting portion 4b, which mounts and rotates the optical disk. Rails 6 are provided on both sides of the tray 3, and both sides are fitted to the rails 7 so as to be slidable in the direction of drawing out the optical disk. The rail 7 is also slidably fitted in the optical disk pull-out direction with rail guides 8 provided on the inner surfaces of both sides of the housing 2, and the tray 3 can be inserted into and removed from the housing 2. When the tray 3 is pulled out from the housing 2 by a predetermined length, the tray 3 is locked to the housing 2. At this time, the optical disk can be mounted on or removed from the optical disk mounting portion 4 b provided on the tray 3. The tray 3 is provided with an extruding portion 12, and the tray 3 pops out of the housing 2 when the extruding portion 12 pushes the housing 2 during a discharge (eject) operation.

  A circuit board 9 having a control circuit is provided on the bottom 2b of the housing 2, and a circuit board 4c having a control circuit is provided on the tray 3. The circuit board 9 and the circuit board 4c are connected by a flexible printed circuit board (also referred to as an FPC) 10. The FPC 10 establishes electrical continuity between the circuit board 9 and the circuit board 4c. The circuit board 9 includes an interface (not shown) for connecting to an external device such as a personal computer.

  FIG. 3 is a block diagram of the optical disc apparatus according to Embodiment 1 of the present invention.

  In FIG. 3, the laser drive control unit 110 drives the laser 102 to emit a light beam, which is a laser beam, and the emitted light beam is irradiated on the recording surface of the optical disc 101 and focused. Reflected light from the optical disk 101 is detected by the reflected light receiving means 105, a tracking error is calculated by the reflected light calculating means 106, tracking control is performed by the data processing unit 108, and the tracking drive coil control means 109 drives the tracking drive coil 104. Adjust the tracking.

  The rotation driving means 112 controls the rotation of the optical disc 101 during recording or reproduction, and controls the rotation of the spindle motor 4a via the spindle motor driving means 111.

  The tracking control in the embodiment of the present invention is a generally well-known control method using three beams, and the light beam emitted from the laser 102 and the main light (0th order diffracted light) and 2 are emitted by an optical member (diffraction grating or the like). The light is separated into two sub-lights (± first-order diffracted light), the reflected light from the optical disk 101 is received by the reflected light receiving means 105, and tracking control is performed based on the received sub-light.

  When the optical disc 102 has a plurality of recording layers, the reflected light from the recording surface actually recorded and the reflected light from the recording surface of another layer different from the recording layer reach the reflected light receiving means 105, The optical system configuration of the optical pickup is such that interference fringes generated in the reflected light receiving means 105 are reduced by reflected light from the recording surface of another layer different from the reflected light from the self recording surface.

  FIG. 4 is a diagram showing an optical system configuration of the optical pickup according to the first embodiment of the present invention.

  4A is a configuration of the optical system of the optical pickup, and FIG. 4B is an enlarged view of the main plane of the beam splitter of the optical system.

  As shown in FIG. 4A, the light beam emitted from the laser 102 is mainly used for recording / reproduction by the optical member (diffraction grating) 124, and 2 used for tracking control. Separated into two sub-lights (± first-order diffracted light). In the embodiment of the present invention, the intensity of the main light and the sub light is set to about 1/10 to 1/20 of the intensity of the sub light with respect to the intensity of the main light. The separated light beam passes through the polarization beam splitter 122 and is collimated by the collimator lens 121 and is collected on the recording surface 125 of the optical disc 101 by the objective lens 6.

  The optical disc 101 includes a plurality of recording layers. In the first embodiment of the present invention, description will be made by performing recording or reproduction on the optical disc 101 having two recording layers of the L0 layer 125a and the L1 layer 125b. There are two layers, L0 layer 125a and L1 layer 125b, in order from the recording layer facing the optical pickup 5, and FIG. 4 shows a model in which the L0 layer 125a is focused.

  The reflected light collected on a predetermined track of the recording surface 125 of the optical disc 101 passes through the objective lens 6 and the collimator lens 121, is reflected by the inclined surface 122a of the polarizing beam splitter 122, and is the main plane 122b of the polarizing beam splitter 122. , The spot is optimally set through the detection lens 123, and the reflected light receiving means (detector) 105 detects the signal.

  Further, as shown in FIG. 4B, the main plane 122b, which is a plane facing the reflected light receiving means 105 of the polarization beam splitter 122, has an average roughness of the main plane as a rough surface instead of a mirror surface.

  The rough surface has an arithmetic average center roughness Ra of the surface roughness of 10 μm or more and 20 μm or less, and a mean square roughness Rq (rms) of 12 μm or more and 25 μm or less.

  As a result, the main plane 122b provided with the rough surface causes the light beam before passing through the main plane 122b to be a parallel wavefront 126a having the same phase, but when the light beam passes through the main plane 122b, the rough surface effects light. The wave front of the beam is disturbed, and the disturbed wave front 126 b reaches the reflected light receiving means 105. Further, it is possible to prevent the surface roughness from becoming too rough and deteriorating the light receiving intensity received by the light receiving means.

  Therefore, the reflected light from the L0 layer 125a actually recorded and the reflected light from the L1 layer 125b of another layer different from the L0 layer 125a are incident on the main plane 122b at different angles and pass through the main plane 122b. The light beams of the two reflected lights have different optical path lengths, the wave front is disturbed on the main plane 122b, and the polarization directions of the two reflected lights are not the same direction. Therefore, as described in detail later, the reflected light from the L0 layer 125a It is possible to reduce the influence of the reflected light from the L1 layer 125b, which is the other layer, interfering on the reflected light receiving means 105 to form interference fringes.

  FIG. 5 is a schematic diagram of an optical system configuration of the optical pickup according to the first embodiment of the present invention. In FIG. 5, the configuration of an optical system for an optical disc having two recording layers will be described as a model.

  5A shows a configuration in which the focus is on the L0 layer, and FIG. 5B shows a configuration in which the focus is on the L1 layer.

  In FIG. 5A, the reflected light from the L0 layer 125a which is the self-recording layer is irradiated with main light (0th order diffracted light) on the detector 401 and sub light (± 1st order diffracted light) on 402a and 402b. In addition, the reflected light from the L1 layer 125b, which is an upper layer than the self-recording layer, has a focal position that is focused and spreads in front of the detector, so that it becomes stray light 403 at the detector position, and the main light detector 401 and the sub-light. Irradiation is performed so as to cover the entire detectors 402a and 402b.

  In FIG. 5B, the reflected light from the L1 layer 125b, which is the self-recording layer, includes main light (0th order diffracted light) for the detector 404 and sub light (± 1st order diffracted light) for the detectors 405a and 405b. Is irradiated. In addition, since the reflected light from the L0 layer 125a, which is a lower layer than the L1 layer 125b, which is the self-recording layer, is focused behind the detector 105, the stray light 406 remains in a wide state without being focused and becomes the main light. Irradiation is performed so as to cover the entire detector 404 and the sub-light detectors 405a and 405b.

  In addition, as described above, the intensity of the sub light (± 1st order diffracted light) is set to about 1/10 to 1/20 with respect to the intensity of the main light (0th order diffracted light). Since the reflected light of the sub light becomes small, the stray light 403 and the stray light 406 are greatly influenced by the reflected light from the main light (0th order diffracted light).

  The sub-light of the self-recording layer and the reflected light of the main light mainly from other layers cause light interference on the detector and are detected as interference fringes.

  6 and 7 are explanatory diagrams relating to interference fringes according to Embodiment 1 of the present invention.

  6A is a configuration in which the main plane 122b of the polarization beam splitter 122 is a mirror surface, FIG. 6B is a configuration in which the main plane 122b of the polarization beam splitter 122 is a rough surface, and FIG. FIG. 7B shows a three-dimensional display in which the main plane 122b of the beam splitter 122 is a mirror surface, and FIG. 7B shows a configuration in which the main plane 122b of the polarization beam splitter 122 is a rough surface.

  The reflected light from the optical disk is a wave having a parallel wavefront, passes through the polarization beam splitter 122, passes through the main plane 122b, and is emitted to the detector 105.

  The speed of the light beam varies depending on the difference in the refractive index n, and differs depending on whether the light beam passes through the polarization beam splitter 122 or escapes into the air. For example, if the refractive index of the polarizing beam splitter 122 such as glass is 1.5 and the refractive index is 1 in the air, the propagation speed is 1.5 times when passing through the polarizing beam splitter 122. Accordingly, the propagation speed changes at the timing (position) through the polarizing beam splitter 122, and the timing at which the detector 105 is irradiated changes.

  In FIG. 6A, reflected light 611a and 611b from the self-recording layer travels in the polarization beam splitter 122 at a wavefront 601a having an inclination with respect to the main plane 122b, while reflecting from the recording surface of the other layer. Lights 612a and 612b travel in the polarization beam splitter 122 at a wavefront 602a having an inclination with respect to the main plane 122b. After passing through the main plane 122b, the reflected light 611a and 611b from the recording layer travels on the wavefront 601b having an inclination, while the reflected light 612a and 612b from the recording surface of the other layer travels on the wavefront 602b having an inclination. The detector 105 is irradiated. Since the main plane 122b of the polarization beam splitter 122 is a mirror surface, the reflected light 611a, 611b from the self-recording layer and the reflected light from the recording surfaces 612a, 612b of the other layers are aligned at the same timing through the main plane 122b. There is a place. Therefore, at the position where the phases of the two beams incident on the main plane 122b at a constant angle coincide with each other, the waves of the reflected light 611a and 611b from the recording layer and the reflected light 612a and 612b from the recording surface of the other layer are used. Since the two waves are in phase with each other, the intensity of the light is increased to form a bright stripe 606a. On the other hand, at the position where the phases of the two waves are shifted, the waves of the reflected light 611a and 611b from the self-recording layer are obtained. And the reflected lights 612a and 612b from the recording surface of the other layer are out of phase, so that the dark stripes 606b become clear and the bright and dark states become clear and interference fringes.

  FIG. 7A shows in three dimensions the interference fringes in the configuration when the main plane 122b of the polarization beam splitter 122 is a mirror surface. When the main plane 122 b of the polarization beam splitter 122 is mirror-finished, the reflected light beam 301 from the recording layer and the reflected light beam 302 from the recording surface of the other layer are the main plane 122 b of the polarization beam splitter 122. The positions where the light beams pass through the main plane 122b of the polarization beam splitter 122 differ from each other according to the inclination, and the detector 105 interferes with the respective light beams and is out of alignment with the phase of the waves. Interference fringes are generated.

  In FIG. 6B, reflected light 611c and 611d from the self-recording layer travels in the polarization beam splitter 122 with a wavefront 601a having an inclination with respect to the main plane 122b, while reflected light 612c from the recording surface of the other layer. , 612d travels in the polarization beam splitter 122 at a wavefront 602a having an inclination with respect to the main plane 122b. Since the main plane 122b of the polarization beam splitter 122 is a rough surface, the timing of exiting from the main plane 122b of the polarization beam splitter 122 changes according to the height of the rough surface, and the light beam that passes through the high surface of the rough surface Delays the time for which the detector 105 is irradiated. Accordingly, the state of the wavefront varies depending on the position depending on the rough surface of the main plane 122b of the polarization beam splitter 122, and wavefront shifts 604 and 605 are generated as shown in FIG. As a result, the time irradiated to the detector 105 varies depending on the position, and the phases of the reflected light from the recording layer and the reflected light from the recording surface of the other layer are randomly shifted, and the waves interfere with each other and the phase is also random. Therefore, the number of places where the phases are aligned is reduced, and the bright stripes and dark stripes are reduced to form stripes 606c and 606d, respectively.

  In the configuration of FIG. 7B, the interference fringes in the configuration when the main plane of the polarization beam splitter 122 is a rough surface are shown in three dimensions. The reflected light beam 301 from the self-recording layer and the reflected light beam 302 from the other recording layer pass through the main plane 122b of the polarizing beam splitter 122 at different angles in the same manner as in the case of a mirror surface. The main plane 122b of the polarization beam splitter 122 is a rough surface, but the position of the polarization beam splitter 122 passing through the main plane 122b varies depending on the inclination, and the detector 105 In this case, the light beams interfere with each other and the places where the phases of the waves are randomly aligned are shifted, resulting in random interference fringes that are not regularly aligned.

  Therefore, since the signal detection accuracy by the sub light for detecting the tracking error when used for the tracking control is improved, the tracking control when recording or reproducing the optical disk having a plurality of recording surfaces can be adjusted with high accuracy. It is possible to provide an optical pickup and an optical disc apparatus that are capable of performing the above.

  FIG. 8 is a diagram showing the surface roughness of the main plane of the polarization beam splitter according to Embodiment 1 of the present invention.

  The main plane 122b of the polarization beam splitter 122 is roughened by sandblasting or the like, and polished so that each of the convex portions has a different height. In addition, each of the convex portions has a different arrangement.

  By this processing, the height of each convex portion forming the rough surface provided on the optical member is made different, or the arrangement is random, so that the reflected light of the sub-light from the self-recording surface differs from the self-recording surface. The position at which the reflected light of the recording surface of the other layer exits from the polarizing beam splitter into the air can be changed according to the difference in the arrangement of the rough surfaces provided on the optical member. As a result, the reflected light of the sub-light from the self-recording surface and the reflected light of the recording layer of another layer different from the self-recording surface can be irradiated as different phases when irradiating the detector, so that the interference fringes are not aligned. To be able to. Therefore, since the signal detection accuracy by the sub light for detecting the tracking error when used for tracking control is improved, it is possible to accurately adjust the tracking control when recording or reproducing on an optical disc having a plurality of recording surfaces. An optical pickup and an optical disc device that can be used can be provided.

(Embodiment 2)
Embodiment 2 of the present invention will be described with reference to the drawings.

  In the description of the second embodiment of the present invention, portions common to the first embodiment will not be described repeatedly and will be omitted.

  FIG. 9 is a diagram showing the configuration of the optical pickup according to the second embodiment of the present invention.

  In FIG. 9, the configuration of the optical pickup includes a laser 501, a diffraction grating 502, a polarization beam splitter 503, a reflection mirror 504, a collimator lens 505, an objective lens 506, a detection lens 507, and a detector 508. ing.

  The light beam emitted from the laser 501 is split into three light beams by the diffraction grating 502. Of these three light beams, the central light beam is referred to as main light, and the two light beams on both sides thereof are referred to as sub light. The light beam branched into three is reflected by the polarization beam splitter 503 and reflected by the reflection mirror 504 so that the traveling direction of the light beam is further bent by 90 degrees. Then, the light beam guided to the collimator lens 505 and reflected by the reflection mirror 504 is converted into parallel light and incident on the objective lens 506, and the light beam is collected on a predetermined track on the recording surface of the optical disk 101 by the objective lens 16. Shine. The condensed light beam passes through the objective lens 506, the collimator lens 505, and the reflection mirror 504 and is incident on the polarization beam splitter 503 as return light.

  The light beam incident on the polarization beam splitter 503 is expanded in the uniaxial direction by the detection lens 507. Irradiate detector 508. The detector 508 generates an electrical signal corresponding to the detected light intensity.

  The detector 508 receives the reflected light of both the reflected light from the recording surface of the self-recording layer and the reflected light (stray light) from the recording surface of the other layer for recording or reproducing when the optical disc 101 has a plurality of recording layers. Since the light beam interferes, interference fringes due to this interference are reduced.

  The detection lens 507 includes a main plane 507 a that faces the polarization beam splitter 503.

  The main plane 507a facing the polarization beam splitter 503 has an average roughness of the main plane as a rough surface 507b instead of a mirror surface.

  The rough surface 507b has a surface roughness with an arithmetic mean center roughness Ra of 10 μm or more and 20 μm or less, and a mean square roughness Rq (rms) of 12 μm or more and 25 μm or less.

  As a result, the wavefront of the parallel wavefront of the light beam whose phases are aligned before passing through the main plane 507a is disturbed by the main plane 507a provided with the rough surface 507b, and is irradiated to the detector 508. Further, it is possible to prevent the light receiving characteristic of the detector 508 from being deteriorated excessively.

  Therefore, the reflected light from the self-recording layer actually recorded and the reflected light from the recording surface of another layer different from the self-recording layer are incident on the main plane 507a at different angles and passed through the main plane 507a. The light beams of the both reflected lights have different optical path lengths, the wave fronts are disturbed on the main plane 507a, and the polarization directions of both reflected lights are not the same direction. Therefore, the reflected light from the self-recording layer and the reflected light from the reflecting surface of the other layer Can interfere with each other on the detector 508 to reduce the influence of interference fringes.

  In the first embodiment and the second embodiment of the present invention, the optical member provided in the optical path of the reflected light reaching the detector, which is the reflected light receiving means, has been described as having a rough surface. Regardless of the second embodiment of the present invention, another form, for example, a configuration in which a flat plate having a rough surface may be added to the optical path of the reflected light, and a plane having a rough surface in the optical path of the reflected light may be provided.

  INDUSTRIAL APPLICABILITY The present invention can be used as an optical disk device mounted on an electronic device such as a personal computer, a notebook computer, a mobile terminal device, and an optical pickup suitably used for the optical disk device, and an optical disk having a plurality of recording layers. Thus, it is possible to realize an optical disc apparatus that can reduce the influence from layers other than the self-recording layer when recording or reproducing, improve the accuracy of tracking control, and perform stable recording or reproduction.

1 is a perspective view of an optical disc apparatus according to Embodiment 1 of the present invention. 1 is an external view of an optical disc device according to Embodiment 1 of the present invention. 1 is a block diagram of an optical disc apparatus according to Embodiment 1 of the present invention. The figure which shows the optical system structure of the optical pick-up in Embodiment 1 of this invention. 1 is a schematic diagram of an optical system configuration of an optical pickup according to Embodiment 1 of the present invention. Explanatory drawing regarding the fluctuation of interference fringes according to Embodiment 1 of the present invention Explanatory drawing regarding the interference fringes according to Embodiment 1 of the present invention The figure which showed the surface roughness of the main plane of the polarization beam splitter concerning Embodiment 1 of this invention The figure which showed the structure of the optical pick-up concerning Embodiment 2 of this invention. The figure which showed the outline of the composition of the conventional optical pickup The figure which showed the schematic of the optical system structure of the optical pick-up with respect to the optical disk which has two recording layers in the conventional structure The figure which showed interference with the reflected light from the self-recording layer of the conventional composition and other layers Explanatory drawing about generation of conventional interference fringes

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 2 Housing | casing 3 Tray 4 Optical pick-up module 5 Optical pick-up 6 Objective lens 101 Optical disk 102 Laser 105 Detector 121 Collimator lens 122 Polarizing beam splitter 122a Slope 122b Main plane 124 Diffraction grating 125 Recording surface 126 Wavefront 501 Laser 502 Diffraction grating 503 Polarizing beam splitter 504 Reflecting mirror 505 Collimator lens 506 Objective lens 507 Detection lens 507a Main plane 507b Rough surface 508 Detector

Claims (7)

Means for separating the laser light emitted from the light source into main light and two sub-lights;
Means for irradiating a predetermined recording surface of an optical disc having a plurality of recording surfaces with the separated light beam;
A light receiving means for receiving reflected light from the optical disc;
An optical member disposed on an optical path from the optical disc to the light receiving means,
The interference light fringes of the sub light generated on the light receiving means are reduced by the reflected light of the sub light from the predetermined recording surface and the reflected light of the main light on the recording surface of another layer different from the predetermined recording surface. An optical pickup comprising a rough surface for disturbing a wavefront of reflected light on the optical member. The rough surface provided on the optical member has a surface roughness of an arithmetic average roughness Ra of 10 μm or more and 20 μm or less, and a root mean square roughness Rq of 12 μm or more and 25 μm or less. Item 1. The optical pickup according to Item 1. 2. The optical pickup according to claim 1, wherein the optical member is a polarization beam splitter, and the rough surface is provided on a main plane on the light receiving means side of the polarization beam splitter. 2. The optical pickup according to claim 1, wherein the optical member is provided with a rough surface on at least one optical member on an optical path from the optical disk to the light receiving means. 5. The optical pickup according to claim 1, wherein each convex portion forming a rough surface provided on the optical member has a different height. 5. The optical pickup according to claim 1, wherein the convex portions forming the rough surface provided on the optical member are randomly arranged. 7. An optical disc apparatus using the optical pickup according to claim 1.

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