JP4504866B2 - Optical pickup device, optical drive device, and information processing device - Google Patents

Description

  The present invention relates to an optical pickup device, an optical drive device, and an information processing device. More specifically, the present invention relates to an optical pickup device used for performing at least reproduction of data recording, reproduction, and erasure on an optical information recording medium, The present invention relates to an optical drive device on which the optical pickup device is mounted, and an information processing device including the optical drive device.

  In recent years, with the advancement of digital technology and the improvement of data compression technology, CD (compact) is used as an information recording medium (media) for recording information (hereinafter also referred to as “content”) such as music, movies, photographs, and computer software. Optical discs such as discs and DVDs (digital versatile discs) have attracted attention, and along with the reduction in price, optical disc apparatuses that use optical discs as information recording media have become widespread.

  In an optical disc apparatus, information is recorded by forming a micro-spot of laser light on a recording surface on which spiral or concentric tracks of an optical disc are formed, and information is reproduced based on reflected light from the recording surface. Is going. This optical disc apparatus is equipped with an optical pickup device for irradiating a recording surface of the optical disc with laser light and receiving reflected light from the recording surface.

  In recent years, downsizing of information devices such as personal computers (hereinafter abbreviated as “personal computers”) has rapidly progressed, and along with this, optical disc apparatuses capable of supporting both CDs and DVDs have been commercialized. In such an optical disc apparatus, an objective lens is shared in order to reduce the size and cost. However, since the substrate thickness is 1.2 mm for CD and 0.6 mm for DVD, when the characteristics of the objective lens are matched with one medium, aberration occurs in the other medium. Various aberration countermeasures have been proposed (for example, Patent Documents 1 to 3).

  Incidentally, the amount of content information tends to increase year by year, and further increase in the recording capacity of the optical disc is expected. Therefore, standards for Blu-ray Disc (hereinafter abbreviated as “BD”) and HD-DVD (High Definition DVD, abbreviated as “HD”) have been proposed. The BD uses a light source having a substrate thickness of 0.1 mm, an oscillation wavelength of 405 nm, and an objective lens having a numerical aperture of 0.85. On the other hand, HD uses a light source having a substrate thickness of 0.6 mm, an oscillation wavelength of 405 nm, and an objective lens having a numerical aperture of 0.65. Therefore, an optical disk apparatus that is not commercialized at present but is compatible with both HD and BD requires an objective lens with a short focal length and a numerical aperture of 0.85. However, an objective lens corresponding to a light beam having a shorter wavelength than that of a conventional DVD, a short focal length, and a numerical aperture of 0.85 has a much larger allowable manufacturing error (manufacturing tolerance) than a conventional objective lens. Because it is small, mass production with high accuracy is very difficult. Further, the same technique as the countermeasure against aberration disclosed in Patent Documents 1 to 3 is insufficient.

JP-A-7-98431 Japanese Patent Laid-Open No. 10-27378 JP-A-9-251658

  The present invention has been made under such circumstances, and a first object thereof is to provide an optical pickup device capable of accurately obtaining a desired signal from a plurality of types of optical information recording media having different substrate thicknesses. There is to do.

  A second object of the present invention is to provide an optical drive device capable of accurately accessing a plurality of types of optical information recording media having different substrate thicknesses.

  A third object of the present invention is to provide an information processing apparatus capable of correctly acquiring information from a plurality of types of optical information recording media having different substrate thicknesses.

From the first viewpoint, the present invention provides a plurality of types of light including a first optical information recording medium and a second optical information recording medium having different substrate thicknesses, which are distances between the incident surface of the light beam and the recording surface. An optical pickup device used for accessing any one of information recording media and performing at least reproduction of information recording, reproduction, and erasing, and a light source that emits a light beam having a first polarization direction; An objective lens that is optimized for one optical information recording medium and collects a light beam emitted from the light source on a recording surface of the optical information recording medium to be accessed; light between the light source and the objective lens A polarization branching optical element arranged on the path and for branching a return light beam through the objective lens; a light splitting optical element arranged on the optical path between the polarization branching optical element and the objective lens; Let it pass through The setting and the setting for converting the light beam in the first polarization direction into the light beam in the second polarization direction are possible, respectively, and any one of the first optical information recording medium and the second optical information recording medium one of the optical information recording medium is set to the transmission when the access target or a first polarization rotator and the other of the optical information recording medium is set to the conversion when the access target; the first Is disposed on an optical path between the polarization rotatory element and the objective lens, transmits a light beam having a polarization direction corresponding to the first optical information recording medium, and corresponds to a polarization direction corresponding to the second optical information recording medium. A first polarization diffractive optical element that selectively diffracts the light beam to give an aberration that cancels out the aberration caused by the difference in the substrate thickness and focuses the light on the recording surface of the second optical information recording medium; ; said first polarization diffraction optical element A quarter-wave plate disposed on an optical path between the objective lens and imparting an optical phase difference of a quarter wavelength to the incident light beam; and a predetermined light receiving of the return light beam branched by the polarization branching optical element A photodetector that receives light at a position; disposed on an optical path of a return beam between the polarization splitting optical element and the photodetector, and configured to transmit the return beam as it is, and change a polarization direction of the return beam Each of which can be set, and when one of the first optical information recording medium and the second optical information recording medium is an access target, the transmission is set, and the other A second polarization optical rotator configured to change when the optical information recording medium is an access target;
Arranged on the optical path of the return light beam between the second polarization rotatory element and the photodetector, and transmits the light beam in one of the first polarization direction and the second polarization direction; And a second polarization diffractive optical element that selectively diffracts the light flux in the other polarization direction and imparts an aberration that cancels the aberration generated in the return path.

According to this, it is any access target of the optical information recording medium of the first optical information recording medium and the second optical information recording medium, so that the good light spot is formed on the recording surface . Therefore, as a result, a desired signal can be accurately obtained from a plurality of types of optical information recording media having different substrate thicknesses.

In this case, before Symbol first polarization rotator can be assumed that a liquid crystal element for rotating the polarization direction of the incident light beam by a rotation angle corresponding to the applied voltage.

In the above SL each optical pickup device, before Symbol first polarization diffraction optical element may be to offset the spherical aberration and higher order aberrations in the recording plane.

In the above SL each optical pickup device is disposed on the optical path between the front Symbol first polarization rotator and said first polarization diffraction optical element, the first polarization diffraction optical element and integral collimator lens Can be further provided.

In the above SL each optical pickup device, before Symbol first polarization diffraction optical element can be a be driven in conjunction with the objective lens.

In the above SL each optical pickup device is disposed on the optical path between the front Symbol first polarization rotatory element and the quarter-wave plate, enters the objective lens according to the type of the accessed optical information recording medium A beam diameter defining element that defines the beam diameter of the luminous flux to be emitted can be further provided.

In this case, before Symbol beam diameter defined by the element has a first region of the circular transmitting the incident light beam, a donut-shaped region adjacent to the outer periphery of the first area, the transmissivity in response to polarization direction of the incident beam Can have different second regions.

In the above SL each optical pickup apparatus, and said beam diameter defined by the element before Symbol first polarization diffraction optical element can be that they are integrated.

In the above SL each optical pickup apparatus, the previous SL quarter-wave plate and the beam diameter defined by the element may be that they are integrated.

In the above SL each optical pickup device, before Symbol objective lens can be to have an appropriate number of apertures in the substrate thickness is the smallest of the optical information recording medium among the plurality of types of optical information recording medium.

In each optical pickup apparatus, between the front Stories second polarization rotator and the light detector is disposed on the optical path of the returning light flux, wherein by transmitting the other light beam of the polarization direction, said one polarization direction A third polarization diffractive optical element that selectively diffracts the light beam and imparts an aberration that cancels out the aberration generated in the return path.

According to a second aspect of the present invention, light capable of at least reproduction of information recording, reproduction, and erasure is performed on a plurality of types of optical information recording media having different intervals between the incident surface of the light beam and the recording surface. A drive device, the optical pickup device of the present invention ; and a processing device for reproducing information recorded on the optical information recording medium using an output signal of a photodetector constituting the optical pickup device. An optical drive device provided.

According to this, since the optical pickup device of the present invention capable of accurately obtaining desired signals from a plurality of types of optical information recording media having different substrate thicknesses is provided, a plurality of types of light having different substrate thicknesses are provided. Access to the information recording medium can be performed with high accuracy.

From a third viewpoint, the present invention is an information processing apparatus capable of accessing a plurality of types of optical information recording media having different distances between the incident surface of the light beam and the recording surface, and the optical drive device of the present invention ; And a main control device that controls the optical drive device.

According to this, since the optical drive device of the present invention is provided, information can be correctly acquired from a plurality of types of optical information recording media having different substrate thicknesses.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a personal computer 10 as an information processing apparatus according to an embodiment of the present invention.

  The personal computer 10 shown in FIG. 1 includes a main control device 92, an optical disk device 20 as an optical drive device, a hard disk device (HDD) 94, an input device 95, a display device 96, a drive interface 97, and the like.

  The HDD 94 includes a hard disk 94b and a drive device 94a for driving the hard disk 94b.

  The display device 96 includes a display unit (not shown) using, for example, a CRT, a liquid crystal display (LCD), a plasma display panel (PDP), and the like, and displays various information instructed from the main control device 92.

  The input device 95 includes at least one input medium (not shown) of, for example, a keyboard, a mouse, a tablet, a light pen, a touch panel, and the like, and notifies the main control device 92 of various information input by the user. Note that information from the input medium may be input in a wireless manner. In addition, an example in which the display device 96 and the input device 95 are integrated includes an LCD with a touch panel.

  The drive interface 97 is a bi-directional interface between the main controller 92, the optical disc apparatus 20, and the HDD 94, such as ATAPI (AT Attachment Packet Interface), SCSI (Small Computer System Interface), and USB (Universal Serial Bus). Complies with standard interface.

  The optical disk device 20 records and reproduces information with respect to the set optical disk (here, the optical disk 15) based on an instruction from the main controller 92.

  As shown in FIG. 2 as an example, the optical disc device 20 includes a spindle motor 22 for rotating the optical disc 15, an optical pickup device 23, a seek motor 21 for driving the optical pickup device 23 in the sledge direction, A laser control circuit 24, an encoder 25, a drive control circuit 26, a reproduction signal processing circuit 28, a buffer RAM 34, a buffer manager 37, an interface 38, a flash memory 39, a CPU 40, a RAM 41, and the like are provided. Note that the arrows in FIG. 2 indicate the flow of typical signals and information, and do not represent the entire connection relationship of each block. In addition, the optical disc apparatus 20 can handle an optical information recording medium compliant with the BD and HD standards as an example. Therefore, an optical information recording medium compliant with the BD and HD standards is used for the optical disc 15.

  As described above, the distance from the light incident surface to the recording surface of the optical disc, the so-called substrate thickness, is 0.1 mm for an optical information recording medium (hereinafter abbreviated as “BD” for convenience) conforming to the BD standard. (See FIG. 3A), and 0.6 mm for an optical information recording medium (hereinafter abbreviated as “HD” for convenience) conforming to the HD standard (see FIG. 3B). The appropriate numerical aperture of the objective lens is 0.85 for BD and 0.65 for HD. In the present embodiment, in particular, when discriminating between BD and HD, the optical disc 15a is BD and the optical disc 15b is HD.

  The optical pickup device 23 is a device for irradiating the recording surface of the optical disc 15 with laser light and receiving reflected light from the recording surface. As shown in FIG. 4 as an example, the optical pickup device 23 includes a light source LD, a polarization beam splitter 54 as a polarization branching optical element, a liquid crystal element 101 as a polarization optical rotator, a collimator lens 52, a prism 53, and polarization diffraction optics. A polarization hologram element 103 as an element, an aperture limiting element 105 as a beam diameter defining element, a quarter wavelength plate 55, an objective lens 60, a detection lens 58, a light receiver PD as a photodetector, and a drive system 61 are provided. ing.

  The light source LD is a semiconductor laser that emits laser light having a central wavelength of 405 nm. Note that the maximum intensity emission direction of the light beam emitted from the light source LD is defined as the + Z direction. Further, as an example, it is assumed that a linearly polarized light (P-polarized light) light beam (light beam in the first polarization direction) is emitted from the light source LD.

  The polarizing beam splitter 54 is disposed on the + Z side of the light source LD, and branches the light beam reflected by the optical disk 15 (return light beam) in the + Y direction. The polarization beam splitter 54 has different reflectance depending on the polarization state of the incident light beam. Here, as an example, the polarization beam splitter 54 is set so that the reflectance with respect to P-polarized light is small and the reflectance with respect to S-polarized light is large. That is, most of the light beam emitted from the light source LD can pass through the polarization beam splitter 54.

  As an example, as shown in FIGS. 5A and 5B, the liquid crystal element 101 includes a twisted nematic (TN) liquid crystal having positive dielectric anisotropy sealed between two glass substrates. Liquid crystal element. A transparent electrode made of indium tin oxide (ITO) and an alignment film made of polyimide are formed on each glass substrate, and the alignment film is subjected to an alignment process by rubbing. Here, the thickness of the liquid crystal layer is about 5 mm. Further, the orientation direction of the major axis of the liquid crystal molecules, that is, the rubbing direction, crosses 90 degrees between the incident side glass substrate and the exit side glass substrate, and the liquid crystal layer is continuously twisted by 90 degrees and aligned. An alternating voltage is applied to the liquid crystal element 101 via a transparent electrode.

  The liquid crystal element 101 is on the + Z side of the polarizing beam splitter 54 and linearly polarized light (here, P-polarized light) from the light source LD is orthogonal to the alignment direction of the liquid crystal molecules on the glass substrate surface adjacent to the deflection surface. Is arranged. Therefore, as shown in FIG. 6 as an example, in a state where an AC voltage (2 V or less in FIG. 6) sufficiently lower than a threshold value (about 4 V in FIG. 6) is applied (hereinafter also referred to as “off state”). The liquid crystal element 101 emits light after rotating the polarization direction of the incident light beam by 90 degrees (see FIG. 5A). On the other hand, in a state where an AC voltage sufficiently higher than the threshold (6 V or more in FIG. 6) is applied (hereinafter also referred to as “on state”), the twisted alignment of the liquid crystal molecules is eliminated, so The light is emitted as it is without changing the polarization direction of the light beam (see FIG. 5B). Note that the off state and the on state are set by the CPU 40. That is, in the present embodiment, the S-polarized light beam becomes a light beam in the second polarization direction.

  The collimating lens 52 is disposed on the + Z side of the liquid crystal element 101 and makes the light beam from the liquid crystal element 101 substantially parallel light.

  The prism 53 is disposed on the + Z side of the collimating lens 52 and bends the optical path of the light beam from the collimating lens 52 in the −Y direction. Note that a reflecting mirror may be used instead of the prism 53.

  The polarization hologram element 103 is disposed on the −Y side of the prism 53, transmits an ordinary light component (here, P-polarized component) included in the incident light beam as it is, and an abnormal light component (here, S-polarized component) included in the incident light beam. ) To give a predetermined aberration. Here, as an example, as shown in FIG. 7, the polarization hologram element 103 is formed by forming a concentric diffraction grating on the substrate surface by, for example, a proton exchange method, and then forming a dielectric film on the diffraction grating. Has been. The phase function of this polarization hologram element 103 is shown in FIG. The refractive index of the substrate is 1.53, the refractive index of the dielectric film with respect to ordinary light is 1.53, and the refractive index of the dielectric film with respect to extraordinary light is 1.73.

  The aperture limiting element 105 is arranged on the −Y side of the polarization hologram element 103 and defines the beam diameter of the light beam incident on the objective lens 60 according to an appropriate numerical aperture on the optical disk 15. As shown in FIG. 9A and FIG. 9B as an example, the aperture limiting element 105 has a circular complete transmission region (first region) in the center and is adjacent to the outer periphery of the complete transmission region. There is a donut-shaped polarization region (second region). This polarization region is formed of a polarizer that quenches S-polarized light. The size of the complete transmission region is set so that the light beam transmitted through only the complete transmission region becomes a light beam corresponding to the numerical aperture 0.65 in the objective lens 60. The size of the polarization region is set so that the light beam that has transmitted through both the complete transmission region and the polarization region becomes a light beam corresponding to the numerical aperture 0.85 of the objective lens 60.

  The quarter-wave plate 55 is disposed on the −Y side of the aperture limiting element 105 and imparts an optical phase difference of a quarter wavelength to the incident light beam.

  The objective lens 60 is disposed on the −Y side of the quarter wavelength plate 55 and condenses the light beam transmitted through the quarter wavelength plate 55 on the recording surface of the optical disc 15. The objective lens 60 has a numerical aperture of 0.85. As an example, as shown in FIG. 10 to FIG. 11B, the one side surface and the other side surface in the optical axis direction have different aspherical shapes, and light with small aberration on the recording surface of the BD. A spot (see FIG. 12A) is designed to be formed. As for the eccentricity tolerance, a value capable of mass production is secured.

  The detection lens 58 is disposed on the + Y side of the polarization beam splitter 54 and condenses the return light beam branched in the + Y direction by the polarization beam splitter 54 on the light receiving surface of the light receiver PD. The light receiver PD includes a plurality of light receiving elements (or light receiving regions) for generating signals (photoelectric conversion signals) used for detecting an RF signal, a wobble signal, a servo signal, and the like in the reproduction signal processing circuit 28. It is configured to include. That is, in the present embodiment, a detection system is configured by the polarization beam splitter 54, the detection lens 58, and the light receiver PD.

  The drive system 61 has a focusing actuator for minutely driving the objective lens 60 in the focus direction, which is the optical axis direction of the objective lens 60, and a tracking actuator for minutely driving the objective lens 60 in the tracking direction. . Here, for convenience, the optimum position of the objective lens 60 in the focus direction when the optical disc 15 is BD is referred to as “first lens position”, and the optimum position of the objective lens 60 in the focus direction when the optical disc 15 is HD is “first”. 2 lens positions ”.

  The operation of the optical pickup device 23 configured as described above will be described with reference to FIGS.

<< When the optical disk 15 is a BD (see FIG. 13) >>
Here, it is assumed that the liquid crystal element 101 is already turned on by the CPU 40, and the objective lens 60 is positioned at the first lens position by the focusing actuator.

  Most of the linearly polarized light (here, P-polarized light) emitted from the light source LD passes through the polarization beam splitter 54 as it is and enters the liquid crystal element 101. Here, since the liquid crystal element 101 is on, the light beam incident on the liquid crystal element 101 is transmitted as it is.

  The light beam from the liquid crystal element 101 becomes substantially parallel light by the collimator lens 52, and its optical path is bent in the −Y direction by the prism 53, and then enters the polarization hologram element 103. Since this incident light is P-polarized light, it passes through the polarization hologram element 103 as it is and enters the aperture limiting element 105. Since this incident light is P-polarized light, it transmits both the complete transmission region and the polarization region in the aperture limiting element 105.

  The light beam from the aperture limiting element 105 enters the quarter-wave plate 55 in a substantially parallel state, is given a quarter-wave optical phase difference, and becomes circularly polarized light. The light beam from the quarter-wave plate 55 is condensed as a minute spot on the recording surface of the optical disk 15a through the objective lens 60. Here, a light flux having a numerical aperture of about 0.85 is collected. In this case, since the objective lens 60 is optimized for the BD as described above, a good light spot is formed on the recording surface.

  The reflected light from the optical disk 15a becomes circularly polarized light in the opposite direction to the outward path, and is converted into substantially parallel light again by the objective lens 60 as a return light beam, and linearly polarized light (here, S-polarized light) orthogonal to the outward path by the quarter wavelength plate 55. ). The light beam from the quarter wave plate 55 enters the aperture limiting element 105. Since this incident light is S-polarized light, it passes only through the complete transmission region in the aperture limiting element 105 and enters the polarization hologram element 103. Since this incident light is S-polarized light, it is diffracted by the polarization hologram element 103, and its optical path is bent in the −Z direction by the prism 53, and then enters the liquid crystal element 101 via the collimator lens 52. Here, since the liquid crystal element 101 is in the on state, the light beam incident on the liquid crystal element 101 is transmitted as it is and then enters the polarization beam splitter 54. Since this incident light is S-polarized light, it is branched in the + Y direction by the polarization beam splitter 54, and the branched light beam is received by the light receiver PD through the detection lens 58. In the light receiver PD, photoelectric conversion is performed for each light receiving element (or light receiving region), and each photoelectric conversion signal is output to the reproduction signal processing circuit 28.

<< When the optical disk 15 is HD (see FIG. 14) >>
Here, it is assumed that the liquid crystal element 101 has already been turned off by the CPU 40 and the objective lens 60 has been positioned at the second lens position by the focusing actuator.

  Most of the linearly polarized light (here, P-polarized light) emitted from the light source LD passes through the polarization beam splitter 54 as it is and enters the liquid crystal element 101. Here, since the liquid crystal element 101 is in the OFF state, the light beam incident on the liquid crystal element 101 is emitted with the polarization direction rotated by 90 degrees. That is, it is converted to S-polarized light.

  The light beam from the liquid crystal element 101 becomes substantially parallel light by the collimator lens 52, and its optical path is bent in the −Y direction by the prism 53, and then enters the polarization hologram element 103. Since this incident light is S-polarized light, it is diffracted by the polarization hologram element 103. Here, as described above, since the objective lens 60 is optimized with respect to the BD, in the case of HD, if no aberration correction is performed, an example is shown in FIG. Aberrations (wavefront aberrations and higher order aberrations) occur. Therefore, in the present embodiment, the diffraction grating of the polarization hologram element 103 is formed so that an aberration that cancels this aberration (hereinafter also referred to as “correction aberration” for convenience) is imparted by the polarization hologram element 103. ing. A diffraction grating is formed so that the divergence angle does not change due to diffraction.

  The light beam from the polarization hologram element 103 enters the aperture limiting element 105. Since this incident light is S-polarized light, it transmits only the complete transmission region in the aperture limiting element 105. That is, only the central portion of the light beam from the polarization hologram element 103 is transmitted.

  The light beam from the aperture limiting element 105 enters the quarter-wave plate 55 in a substantially parallel state, is given a quarter-wave optical phase difference, and becomes circularly polarized light. The light beam from the quarter-wave plate 55 is condensed as a minute spot on the recording surface of the optical disk 15b through the objective lens 60. Here, a light flux corresponding to a numerical aperture of about 0.65 is collected. In this case, since a correction aberration is given by the polarization hologram element 103, a good light spot is formed on the recording surface.

  The reflected light from the optical disk 15b becomes circularly polarized light opposite to the outward path, and is converted into substantially parallel light again by the objective lens 60 as a return beam, and is linearly polarized light (here P-polarized light) orthogonal to the outward path by the quarter wavelength plate 55. ). The light beam from the quarter wave plate 55 enters the aperture limiting element 105. Since this incident light is P-polarized light, it passes through both the complete transmission region and the polarization region in the aperture limiting element 105 and enters the polarization hologram element 103. Since this incident light is P-polarized light, it passes through the polarization hologram element 103 as it is, and its optical path is bent in the −Z direction by the prism 53 and then enters the liquid crystal element 101 via the collimator lens 52. Here, since the liquid crystal element 101 is in the OFF state, the light beam incident on the liquid crystal element 101 is emitted with the polarization direction rotated by 90 degrees. That is, it is converted to S-polarized light. The light beam from the liquid crystal element 101 enters the polarization beam splitter 54. Since this incident light is S-polarized light, it is branched in the + Y direction by the polarization beam splitter 54, and the branched light beam is received by the light receiver PD through the detection lens 58. In the light receiver PD, photoelectric conversion is performed for each light receiving element (or light receiving region), and each photoelectric conversion signal is output to the reproduction signal processing circuit 28.

  Returning to FIG. 2, the reproduction signal processing circuit 28 determines the servo signal (focus error signal, track error signal, etc.), address information, synchronization information, and the like based on the output signal (a plurality of photoelectric conversion signals) of the light receiver PD. An RF signal or the like is acquired. The servo signal obtained here is output to the drive control circuit 26, the address information is output to the CPU 40, and the synchronization signal is output to the encoder 25, the drive control circuit 26, and the like. Further, the reproduction signal processing circuit 28 performs decoding processing, error detection processing, and the like on the RF signal. When an error is detected, the reproduction signal processing circuit 28 performs error correction processing, and then plays back the buffer via the buffer manager 37 as reproduction data. Store in the RAM 34. The address information included in the reproduction data is output to the CPU 40.

  The drive control circuit 26 generates a drive signal for the tracking actuator for correcting the displacement of the objective lens 60 in the tracking direction based on the track error signal from the reproduction signal processing circuit 28. The drive control circuit 26 also generates a driving signal for the focusing actuator for correcting the focus shift of the objective lens 60 based on the focus error signal from the reproduction signal processing circuit 28. The drive signals for the actuators generated here are output to the optical pickup device 23. Thereby, tracking control and focus control are performed. Furthermore, the drive control circuit 26 generates a drive signal for driving the seek motor 21 and a drive signal for driving the spindle motor 22 based on an instruction from the CPU 40. The drive signal of each motor is output to the seek motor 21 and the spindle motor 22, respectively.

  The buffer RAM 34 temporarily stores data to be recorded on the optical disc 15 (recording data), data reproduced from the optical disc 15 (reproduction data), and the like. Data input / output to / from the buffer RAM 34 is managed by the buffer manager 37.

  The encoder 25 takes out the recording data stored in the buffer RAM 34 through the buffer manager 37 based on an instruction from the CPU 40, modulates the data, adds an error correction code, and the like, and writes a signal to the optical disc 15. Is generated. The write signal generated here is output to the laser control circuit 24.

  The laser control circuit 24 controls the light emission power of the light source LD. For example, at the time of recording, a drive signal for the light source LD is generated by the laser control circuit 24 based on the write signal, recording conditions, light emission characteristics of the light source LD, and the like.

  The interface 38 is a bidirectional communication interface with the main control device 92 via the drive interface 97, and conforms to the same standard interface as the drive interface 97.

  The flash memory 39 stores various programs described by codes readable by the CPU 40, recording conditions including recording power and recording strategy information, and light emission characteristics of the light source LD.

  The CPU 40 controls the operation of each unit in accordance with the program stored in the flash memory 39 and stores data necessary for control in the RAM 41 and the buffer RAM 34.

  Whether the optical disc 15 is HD or BD is determined based on disc information recorded at a predetermined position of the optical disc when the optical disc 15 is set in the optical disc apparatus 20. Then, the determination result is notified to the reproduction signal processing circuit 28 and the like. Further, the CPU 40 sets the liquid crystal element 101 in an appropriate state according to the type of the optical disk 15.

《Reproduction processing》
When the user inputs a playback request for the optical disc 15 via the input device 95, the main control device 92 outputs a playback request command to the optical disc device 20.

  When receiving the reproduction request command, the CPU 40 instructs the drive control circuit 26 to rotate the optical disc 15 at a predetermined linear velocity (or angular velocity) and notifies the reproduction signal processing circuit 28 that the reproduction request command has been received. To do.

  When the CPU 40 confirms that the optical disk 15 is rotating at a predetermined linear velocity (or angular velocity), the CPU 40 instructs the drive control circuit 26 to form a light spot near the target position corresponding to the designated address. To do. Thereby, a seek operation is performed.

  When the seek operation is completed, the CPU 40 permits reproduction. Thereby, the reproduction signal processing circuit 28 performs reproduction processing.

  When the reproduction of the designated data is completed, the CPU 40 ends the process for the reproduction request command.

  As is clear from the above description, in the optical disc apparatus 20 according to the present embodiment, the reproduction signal processing circuit 28, the CPU 40, and a program executed by the CPU 40 constitute a processing apparatus. It should be noted that at least a part of the processing according to the program by the CPU 40 may be configured by hardware, or all may be configured by hardware.

  As described above, according to the optical pickup device 23 according to the present embodiment, when the optical information recording medium to be accessed is a BD (first optical information recording medium), the objective lens 60 is optimal for the BD. Therefore, a good light spot is formed on the recording surface. When the optical information recording medium to be accessed is HD (second optical information recording medium), the P-polarized light beam (light beam in the first polarization direction) emitted from the light source LD is the liquid crystal element 101 (polarization optical rotation). After being converted into an S-polarized light beam (light beam in the second polarization direction) by the element, it is diffracted by the polarization hologram element 103 (polarization diffractive optical element). At this time, a correction aberration that cancels out aberrations (wavefront aberration and higher-order aberration) caused by the difference in substrate thickness between BD and HD is given, so that a good light spot is formed on the recording surface. That is, a good light spot is formed on the recording surface regardless of whether the optical information recording medium to be accessed is BD or HD. Therefore, as a result, a desired signal can be accurately obtained from a plurality of types of optical information recording media having different substrate thicknesses.

  In addition, since an inexpensive objective lens can be used, the cost can be reduced.

  In addition, regardless of whether the optical information recording medium to be accessed is BD or HD, a single objective lens can form a good light spot on the recording surface, enabling downsizing and cost reduction of the apparatus. It becomes.

  Further, since a liquid crystal element is used as the polarization rotatory element, a special drive mechanism is not required, and the apparatus can be reduced in size and cost.

  Further, in the polarization hologram element 103, since the divergence angle of the incident light beam is maintained, the axial deviation in the objective lens 60 can be suppressed. Thereby, the aberration (wavefront aberration and higher order aberration) generated in the objective lens 60 is reduced.

  In addition, since the aperture limiting element 105 is composed of a circular complete transmission region (first region) and a donut-shaped polarization region (second region) adjacent to the outer periphery of the complete transmission region, the aperture limitation is performed. It can be done easily.

  In addition, according to the optical disk device 20 according to the present embodiment, a signal with a high S / N ratio is output from the optical pickup device 23 regardless of whether the optical disk 15 is HD or BD. However, access can be performed with high accuracy. Therefore, it is possible to accurately access a plurality of types of optical information recording media having different substrate thicknesses. Further, the optical pickup device 23 can be reduced in size and cost by reducing the size and cost thereof.

  In addition, the personal computer 10 according to the present embodiment includes the optical disc device 20 capable of accurately accessing both HD and BD, and therefore, a plurality of types of optical information recording media having different substrate thicknesses. It becomes possible to acquire information correctly from Further, the size and cost of the personal computer 10 can be reduced by reducing the size and cost of the optical disk device 20.

  In the above embodiment, as the liquid crystal element 101, as shown in FIG. 15, a half-wave plate that can rotate in a plane perpendicular to the traveling direction of the light beam may be used. In this case, when the optical disk 15 is a BD, the CPU 40 transmits the light beam from the light source LD as it is through the half-wave plate, whereas when the optical disk 15 is an HD, the CPU 40 converts the light beam from the light source LD to the light beam LD. The rotation of the half-wave plate is controlled so that the half-wave optical phase difference is given.

  Moreover, in the said embodiment, as FIG. 16 shows as an example, while arrange | positioning the said polarization hologram element 103 on the optical path between the said liquid crystal element 101 and the said collimating lens 52, the polarization hologram element 103 and a collimating lens 52 may be integrated. Thereby, the number of parts can be reduced and cost reduction can be achieved.

  In the above embodiment, as shown in FIG. 17 as an example, the quarter-wave plate 55, the aperture limiting element 105, and the polarization hologram element 103 are driven in conjunction with the objective lens 60, respectively. You may make it. In this case, specifically, the quarter wavelength plate 55, the aperture limiting element 105, and the polarization hologram element 103 are fixed to a lens holder (not shown) that holds the objective lens 60. Thereby, the number of parts can be reduced and cost reduction can be achieved. Thereby, even if the objective lens 60 is shifted in the tracking direction, a good light spot can be formed.

  Further, in the above embodiment, when it is necessary to further increase the S / N ratio of the signal output from the light receiver PD, as shown in FIG. 18 and FIG. A liquid crystal element 107 and two polarization hologram elements (108, 109) may be further disposed on the optical path of the returning light flux between the detection lens 58 and the detection lens 58. That is, a liquid crystal element 107 and two polarization hologram elements (108, 109) may be added to the detection system.

  In this case, the liquid crystal element 107 has the same optical characteristics as the liquid crystal element 101 in the above embodiment, and is disposed on the + Y side of the polarizing beam splitter 54. The BD is turned on and the HD is turned off. The polarization hologram element 108 is disposed on the + Y side of the liquid crystal element 107, transmits an ordinary light component (here, a P-polarized component) included in the incident light beam (return light beam) as it is, and an abnormal light component (here, the light beam component). S-polarized component) is diffracted. Here, the diffraction grating of the polarization hologram element 108 is formed such that an aberration that cancels out aberrations (wavefront aberration and higher-order aberration) generated in the return path is added to the extraordinary light component. The polarization hologram element 109 is arranged on the + Y side of the polarization hologram element 108, transmits the extraordinary light component (here, the S polarization component) included in the incident light beam as it is, and the ordinary light component (here, the P polarization component) included in the incident light beam. ). Here, the diffraction grating of the polarization hologram element 109 is formed such that an aberration that cancels out aberrations (wavefront aberration and higher-order aberration) generated in the return path is added to the ordinary light component. The operation of the detection system in this case will be described.

<< When the optical disc 15 is a BD (see FIG. 18) >>
The return light beam (S-polarized light) branched in the + Y direction by the polarization beam splitter 54 passes through the liquid crystal element 107 as it is, is diffracted by the polarization hologram element 108, passes through the polarization hologram element 109 as it is, and passes through the detection lens 58. Light is received by the light receiver PD. Thereby, the aberration (wavefront aberration and higher-order aberration) generated in the return path is canceled by the polarization hologram element 108, and the S / N ratio of the signal output from the light receiver PD can be further increased. That is, the light utilization efficiency can be further improved.

<< When the optical disk 15 is HD (see FIG. 19) >>
The return light beam (S-polarized light) branched in the + Y direction by the polarization beam splitter 54 is converted into P-polarized light by the liquid crystal element 107, passes through the polarization hologram element 108 as it is, is diffracted by the polarization hologram element 109, and then is detected. The light is received by the light receiver PD via 58. Thereby, the aberration (wavefront aberration and higher order aberration) generated in the return path is canceled out by the polarization hologram element 109, and the S / N ratio of the signal output from the light receiver PD can be further increased.

  18 and 19, the case where the polarization hologram element 108 is arranged closer to the liquid crystal element 107 than the polarization hologram element 109 has been described. However, the polarization hologram element 109 is more liquid crystal element 107 than the polarization hologram element 108. It may be arranged on the side.

  18 and 19, the liquid crystal element 107 is described as being turned on when the optical disk 15 is BD and turned off when the optical disk 15 is HD. However, the liquid crystal element 107 is turned off when the optical disk 15 is BD. It may be in the state, and may be in the on state when HD. However, in this case, the polarization hologram element 108 transmits the extraordinary light component (here, the S-polarized component) included in the incident light beam (return light beam) as it is, and the ordinary light component (here, the P-polarized light) included in the incident light beam. Component) must be set to diffract. Further, the polarization hologram element 109 transmits the ordinary light component (here, P-polarized component) included in the incident light beam (return light beam) as it is, and diffracts the extraordinary light component (here, S-polarized component) included in the incident light beam. It is necessary to set as follows. Alternatively, in this case, the polarization hologram element 108 gives an aberration that cancels the aberration that occurs in the return path when the optical disc 15 is HD, and the aberration that cancels the aberration that occurs in the return path when the optical disc 15 is BD. The polarization hologram element 109 may be used.

  18 and 19, the polarization hologram element 109 may be omitted when the aberration generated on the return path is small when the optical disk 15 is HD.

  18 and 19, when the optical disk 15 is a BD and the aberration generated in the return path is small, the polarization hologram element 108 may be omitted.

  In this case, instead of the detection lens 58, for example, a detection lens 58 ′ designed to correct aberrations (wavefront aberration and higher-order aberration) generated on the return path during BD, for example, is used. As shown in FIGS. 20 and 21, the polarization hologram element 108 can be omitted. The operation of the detection system in this case will be described.

<< When the optical disc 15 is a BD (see FIG. 20) >>
The return light beam (S-polarized light) branched in the + Y direction by the polarization beam splitter 54 is transmitted as it is through the liquid crystal element 107 and the polarization hologram element 109, and the aberration (wavefront aberration and higher-order aberration) is corrected by the detection lens 58 ′. Thereafter, the light is received by the light receiver PD. Thereby, the aberration (wavefront aberration and higher order aberration) generated in the return path is corrected by the detection lens 58 ′, and the S / N ratio of the signal output from the light receiver PD can be further increased.

<< When the optical disk 15 is HD (see FIG. 21) >>
The return light beam (S-polarized light) branched in the + Y direction by the polarization beam splitter 54 is converted into P-polarized light by the liquid crystal element 107, diffracted by the polarization hologram element 109, and then received by the light receiver PD via the detection lens 58 ′. Received light. Thereby, the aberration (wavefront aberration and higher order aberration) generated in the return path is canceled by the polarization hologram element 109, and the S / N ratio of the signal output from the light receiver PD can be further increased. For example, as shown in FIG. 22, the straight line area in the focus error signal detected by the reproduction signal processing circuit 28 is enlarged, and the accuracy of focus control can be further increased. In the case of BD and HD, aberrations that occur on the return path are different from each other.

  Moreover, although the said embodiment demonstrated the case where the said aperture limiting element 105 was arrange | positioned between the said polarization hologram element 103 and the said 1/4 wavelength plate 55, it is not limited to this. In short, it may be disposed between the liquid crystal element 101 and the quarter-wave plate 55.

  In the above embodiment, the liquid crystal element 101 has been described as being turned on when the optical disk 15 is BD and turned off when the optical disk 15 is HD. However, the liquid crystal element 101 is turned off when the optical disk 15 is BD. In addition, it may be turned on in the HD. However, in this case, the polarization hologram element 103 transmits the extraordinary light component (here, the S-polarized component) contained in the incident light beam as it is, and diffracts the ordinary light component (here, the P-polarized component) contained in the incident light beam. Therefore, it is necessary to set so as to give the aberration.

  In the above embodiment, the optical disk apparatus capable of recording and reproducing information has been described. However, the present invention is not limited to this, and any optical disk apparatus capable of reproducing at least information among recording, reproducing and erasing of information may be used. .

  In the above embodiment, the case where the optical pickup device includes one semiconductor laser has been described. However, the present invention is not limited thereto, and for example, a plurality of semiconductor lasers that emit light beams having different wavelengths may be included. In this case, for example, at least one of a semiconductor laser that emits a light beam with a wavelength of about 660 nm and a semiconductor laser that emits a light beam with a wavelength of about 780 nm may be further provided. That is, the optical disk apparatus may be an optical disk apparatus that supports a plurality of types of optical disks that conform to different standards.

  In the above embodiment, the optical disk device 20 may be either a built-in type or an external type with respect to the personal computer 10. Similarly, the HDD 94 may be either a built-in type or an external type.

  Moreover, although the said embodiment demonstrated the case of the personal computer as information processing apparatus, this invention is not limited to this.

  As described above, the pickup device of the present invention is suitable for accurately obtaining a desired signal from a plurality of types of optical information recording media having different substrate thicknesses. The optical drive device of the present invention is suitable for accurately accessing a plurality of types of optical information recording media having different substrate thicknesses. The information processing apparatus of the present invention is suitable for correctly acquiring information from a plurality of types of optical information recording media having different substrate thicknesses.

It is a block diagram which shows schematic structure of the personal computer as an information processing apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the optical disk apparatus in FIG. It is a figure for demonstrating the optical disk in FIG. It is a figure for demonstrating the optical pick-up apparatus in FIG. 5A and 5B are diagrams for explaining the liquid crystal element in FIG. It is a figure for demonstrating the characteristic of the liquid crystal element in FIG. It is a figure for demonstrating the polarization hologram element in FIG. It is a figure for demonstrating the phase function of the polarization hologram element in FIG. FIG. 9A and FIG. 9B are diagrams for explaining the aperture limiting element in FIG. 4, respectively. FIG. 5 is a first diagram for explaining the objective lens in FIG. 4; FIGS. 11A and 11B are views (No. 2) for explaining the objective lens in FIG. 12A and 12B are views (No. 3) for explaining the objective lens in FIG. 4, respectively. FIG. 3 is a diagram (part 1) for explaining the operation of the optical pickup device in FIG. 2; FIG. 3 is a diagram (part 2) for explaining the operation of the optical pickup device in FIG. 2; It is a figure for demonstrating the polarization optical rotation element which can be used instead of the liquid crystal element in FIG. It is a figure for demonstrating the modification 1 of the optical pick-up apparatus in FIG. It is a figure for demonstrating the modification 2 of the optical pick-up apparatus in FIG. FIG. 10 is a diagram (No. 1) for describing a third modification of the optical pickup device in FIG. 2; FIG. 10 is a diagram (No. 2) for explaining the third modification of the optical pickup device in FIG. FIG. 10 is a diagram (No. 1) for describing a fourth modification of the optical pickup device in FIG. 2; FIG. 10 is a diagram (No. 2) for describing a fourth modification of the optical pickup device in FIG. 2; It is a figure for demonstrating the effect of the polarization hologram element 109 in the optical pick-up apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Personal computer (information processing apparatus), 15 ... Optical disk (optical information recording medium), 15a ... BD (first optical information recording medium), 15b ... HD (second optical information recording medium), 20 ... Optical disk apparatus ( Optical drive device), 23 ... Optical pickup device, 28 ... Reproduction signal processing circuit (part of processing device), 40 ... CPU (part of processing device), 52 ... Collimator lens, 54 ... Polarization beam splitter (polarization splitting optics) Element), 55... Quarter-wave plate, 60... Objective lens, 92. Main controller, 101... Polarization rotatory element, 103 .. polarization hologram element (polarization diffractive optical element), 105. ), 107... Polarization rotatory element (second polarization rotatory element), 108... Polarization hologram element (second polarization diffractive optical element), 109... Polarization hologram element (third polarization diffracted light) Elements), LD ... light source, PD ... photodetector (light detector).

Claims (13)

Access to any of a plurality of types of optical information recording media including a first optical information recording medium and a second optical information recording medium having different substrate thicknesses, which are distances between the incident surface of the light beam and the recording surface, and information An optical pickup device used for performing at least reproduction among recording, reproduction, and erasure of
A light source that emits a light beam in a first polarization direction;
An objective lens that is optimized for the first optical information recording medium and condenses the light beam emitted from the light source on the recording surface of the optical information recording medium to be accessed;
A polarization branching optical element that is disposed on an optical path between the light source and the objective lens and branches a return light beam through the objective lens;
A setting that is arranged on an optical path between the polarization splitting optical element and the objective lens and that allows the light beam in the first polarization direction to pass through as it is, and the light beam in the first polarization direction is a light beam in the second polarization direction. Each of the optical information recording media of the first optical information recording medium and the second optical information recording medium can be set to be transmitted when it is an access target. A first polarization optical rotator configured to perform the conversion when the other optical information recording medium is an access target;
It is disposed on the optical path between the first polarization optical rotator and the objective lens, transmits a light beam having a polarization direction corresponding to the first optical information recording medium, and corresponds to the second optical information recording medium. The first polarization diffraction that selectively diffracts the light beam in the polarization direction to be applied, gives an aberration that cancels out the aberration caused by the difference in the substrate thickness, and focuses the light on the recording surface of the second optical information recording medium. An optical element;
A quarter-wave plate disposed on the optical path between the first polarization diffractive optical element and the objective lens and imparting an optical phase difference of a quarter wavelength to the incident light beam;
A photodetector for receiving the return light beam branched by the polarization branching optical element at a predetermined light receiving position;
It is arranged on the optical path of the return light beam between the polarization branching optical element and the photodetector, and the setting for transmitting the return light beam as it is and the setting for changing the polarization direction of the return light beam are possible, The optical information recording medium is set to transmit when one of the first optical information recording medium and the second optical information recording medium is an access target, and the other optical information recording medium is an access target. A second polarization rotatory element, sometimes set to change;
Arranged on the optical path of the return light beam between the second polarization rotatory element and the photodetector, and transmits the light beam in one of the first polarization direction and the second polarization direction; selectively diffracts light beams in the other polarization direction, and the second polarization diffraction optical element which imparts the aberration to cancel the aberration generated in the return path; optical pickup device comprising a. 2. The optical pickup device according to claim 1, wherein the first polarization rotator is a liquid crystal element that rotates a polarization direction of an incident light beam at a rotation angle corresponding to an applied voltage. 3. The optical pickup device according to claim 1, wherein the first polarization diffractive optical element cancels spherical aberration and high-order aberration on the recording surface. 4. A collimating lens disposed on an optical path between the first polarization rotatory element and the first polarization diffractive optical element, and further integrated with the first polarization diffractive optical element. Item 4. The optical pickup device according to any one of Items 1 to 3. The optical pickup device according to claim 1, wherein the first polarization diffractive optical element is driven in conjunction with the objective lens. A beam that is disposed on the optical path between the first polarization rotator and the quarter-wave plate and that defines the beam diameter of the light beam incident on the objective lens according to the type of the optical information recording medium to be accessed. The optical pickup device according to claim 1, further comprising a diameter defining element.   The beam diameter defining element includes a circular first region that transmits an incident light beam, and a donut-shaped region that is in contact with the outer periphery of the first region, and a second region that has different transmittance depending on the polarization direction of the incident light beam The optical pickup device according to claim 6, further comprising: 8. The optical pickup device according to claim 6, wherein the first polarization diffractive optical element and the beam diameter defining element are integrated.   The optical pickup device according to any one of claims 6 to 8, wherein the quarter-wave plate and the beam diameter defining element are integrated.   The light according to claim 1, wherein the objective lens has a numerical aperture suitable for an optical information recording medium having a minimum substrate thickness among the plurality of types of optical information recording media. Pickup device. It is disposed on the optical path of the return light beam between the second polarization rotatory element and the photodetector, transmits the light beam in the other polarization direction, and selectively diffracts the light beam in the one polarization direction. third polarization diffraction optical element which imparts the aberration to cancel the aberration generated in the return path; optical pickup device written in any one of claims 1 to 10, further comprising a. An optical drive device capable of reproducing at least one of recording, reproducing and erasing information with respect to a plurality of types of optical information recording media having different intervals between a light incident surface and a recording surface,
An optical pickup device according to any one of claims 1 to 11 ;
An optical drive device comprising: a processing device that reproduces information recorded on the optical information recording medium using an output signal of a photodetector constituting the optical pickup device. An information processing apparatus capable of accessing a plurality of types of optical information recording media having different intervals between a light incident surface and a recording surface,
An optical drive device according to claim 12 ;
An information processing apparatus comprising: a main control device that controls the optical drive device.

Images