JP2007200427A - Multilayer optical information recording medium, optical head, and optical drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer optical information recording medium which has tilt stability equivalent to that of an optical information recording medium having the less number of recording layers. <P>SOLUTION: One unit includes a guide track layer S corresponding to light (blue-color light) having a wavelength of 390-420 nm and an information layer M having a plurality of recording layers comprising two-photon absorbing materials corresponding to light (red-color light) having a wavelength of 650-680 nm. Then, the plurality of units (U1, U2 and U3) are sequentially laminated on a cover layer C. Thus, the guide track layer S and the information layer M each correspond to different-wavelength light, and accordingly servo control is executed in the same manner as a case that the number of recoding layers is smaller without reduction in recording capacity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multilayer optical information recording medium, an optical head, and an optical drive device. More specifically, the present invention relates to a multilayer optical information recording medium in which a plurality of recording layers are laminated, an optical head that can handle the multilayer optical information recording medium, The present invention also relates to an optical drive apparatus capable of reproducing at least one of recording, reproduction and erasure of information on the multilayer optical information recording medium.

  In recent years, with the advancement of digital technology and the improvement of data compression technology, DVD (digital versatile disc) and the like are used as media for recording information (hereinafter also referred to as “content”) such as music, movies, photos, and computer software. Optical 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.

  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. Thus, as one of means for increasing the recording capacity of the optical disk, it is conceivable to make the recording layer multi-layered, and an optical disk having a plurality of recording layers (hereinafter also referred to as “multi-layer disk”) and an optical disk for accessing the multi-layer disk. The development of equipment is being actively conducted.

  However, when the number of recording layers in the conventional optical disc is increased to 2, 3, and 4, the amount of reflected light decreases as the distance from the incident surface decreases due to light absorption in each recording layer. The amount of signal light is reduced, and depending on the recording layer, it becomes difficult to detect the signal, and a conventional semiconductor laser cannot provide sufficient recording power. That is, there is a limit to the number of recording layers.

  Accordingly, in recent years, multilayer disks using a two-photon absorption material have been proposed as a technique that can further increase the number of recording layers (for example, Patent Document 1 and Patent Document 2). This utilizes the fact that the refractive index of a two-photon absorption material changes due to two-photon absorption. That is, information is recorded on the recording layer by the length of the region (pit) where the refractive index has changed and the length of the region where the refractive index has not changed and the combination thereof.

  Since the probability of occurrence of two-photon absorption is proportional to the square of the added photoelectric field (incident light intensity), two-photon absorption is induced only in a region where the energy of incident light is concentrated. That is, if the incident light is collected by the lens, it is possible to create a state in which two-photon absorption occurs only near the focal point and no absorption occurs in other unfocused spaces. Therefore, even if light is irradiated on the recording layer other than the vicinity of the condensing point, the refractive index does not change and the light is transmitted as it is, and even if the number of recording layers increases, signal detection becomes difficult or sufficient. There is no problem that the recording power cannot be obtained.

  Therefore, if the number of recording layers is increased from 10, 20 to 50 layers, the capacity can be dramatically increased. However, as with conventional multilayer discs, the formation of guide tracks on each recording layer raises the problem of increased manufacturing costs.

  Thus, it has been devised to form guide tracks other than the recording layer (see, for example, Patent Document 3 and Patent Document 4).

  In the recording medium disclosed in Patent Document 3, in order to detect the reflected light from the servo layer and perform servo control, when the recording medium is inclined in the radial direction with respect to the incident direction of light, the servo layer There is a possibility of causing a track shift in a distant data layer. For example, in the data layer at a position 1 mm away from the servo layer, if the recording medium is tilted by 1 ° with respect to the light incident direction, the light condensing position is shifted by 17.4 μm. This corresponds to a shift of about 50 tracks when the track pitch is 0.32 μm as in the case of an optical disc conforming to the Blu-ray standard. Therefore, the recording medium disclosed in Patent Document 3 requires tilt control different from the case where the number of recording layers is small. Furthermore, although a two-photon absorption can provide a small condensing spot in the data layer, a servo layer without a two-photon absorbing material results in a large condensing spot. As a result, the track density cannot be increased, and the recording capacity per data layer cannot be increased.

  Moreover, in the optical information recording medium disclosed in Patent Document 4, it is very difficult to accurately arrange the first layer and the second layer so that the concavo-convex portions are aligned.

JP-A-6-28672 JP 2004-79121 A JP 2002-31958 A JP 2005-18852 A

  The present invention has been made under such circumstances. The first object of the present invention is to provide a multilayer optical information recording having tilt stability equivalent to the case where the number of recording layers is small without causing a reduction in recording capacity. To provide a medium.

  A second object of the present invention is to provide an optical head capable of accurately acquiring signals from the multilayer optical information recording medium of the present invention.

  A third object of the present invention is to provide an optical drive device capable of accurately performing at least reproduction of information recording, reproduction and erasure on the multilayer optical information recording medium of the present invention. .

  From the first viewpoint, the present invention provides a unit in which a guide layer corresponding to light having a first wavelength and a plurality of recording layers corresponding to light having a second wavelength different from the first wavelength are stacked. A multilayer optical information recording medium in which a plurality of layers are stacked.

  According to this, a plurality of units each including a guide layer and a plurality of recording layers are stacked, and the guide layer and each recording layer correspond to light having different wavelengths, so that the recording capacity is not reduced. Thus, it is possible to have tilt stability equivalent to that when the number of recording layers is small.

  From a second standpoint, the present invention supports a plurality of guide layers corresponding to light having a first wavelength; and a light having a second wavelength different from the first wavelength stacked on the plurality of guide layers. A multilayer optical information recording medium comprising: a plurality of recording layers;

  According to this, a plurality of recording layers are laminated on a plurality of guide layers, and each guide layer and each recording layer correspond to light of different wavelengths, so that the recording layer is not reduced without causing a reduction in recording capacity. It is possible to have tilt stability equivalent to that when the number of layers is small.

  From a third viewpoint, the present invention supports a plurality of guide layers corresponding to light of the first wavelength and a light of a second wavelength different from the first wavelength stacked on the plurality of guide layers. A multilayer optical information recording medium in which a plurality of units including a plurality of recording layers are stacked.

  According to this, a plurality of units including a plurality of guide layers and a plurality of recording layers stacked on the plurality of guide layers are stacked, and each guide layer and each recording layer correspond to light of different wavelengths. Therefore, tilt stability equivalent to that when the number of recording layers is small can be achieved without causing a reduction in recording capacity.

  According to a fourth aspect of the present invention, there is provided an optical head that is compatible with the multilayer optical information recording medium of the present invention, and a light source that emits light of a first wavelength in the multilayer optical information recording medium; A light source that emits light of a second wavelength in the optical information recording medium; and condensing the light of the first wavelength on a guide layer of the multilayer optical information recording medium, and the light of the second wavelength of the guide layer An objective lens for condensing on the recording layer of the multilayer optical information recording medium corresponding to the above, guiding light from each of the light sources to the objective lens, and reflecting from the multilayer optical information recording medium via the objective lens An optical system for separating light into reflected light from the guide layer and reflected light from the recording layer; a photodetector for receiving reflected light from the guide layer separated by the optical system; and the optical system Reflected light from the recording layer separated by An optical head comprising; a photodetector for receiving.

  According to this, the light of the first wavelength and the light of the second wavelength in the multilayer optical information recording medium of the present invention are respectively emitted from each light source, and the light of the first wavelength is multilayer optical information by the objective lens. The light is condensed on the guide layer of the recording medium, and the light of the second wavelength is condensed on the recording layer of the multilayer optical information recording medium corresponding to the guide layer. Then, the reflected light from the guide layer and the reflected light from the recording layer are individually received by each photodetector. Therefore, it is possible to acquire a signal with high accuracy from the multilayer optical information recording medium of the present invention.

  From a fifth aspect, the present invention is an optical head that is compatible with the multilayer optical information recording medium of the present invention, and a light source that emits light of a first wavelength in the multilayer optical information recording medium; A plurality of light sources respectively emitting light of a second wavelength in the optical information recording medium; condensing the light of the first wavelength on a guide layer of the multilayer optical information recording medium, and light of each of the second wavelengths An objective lens for condensing each of the plurality of recording layers of the multilayer optical information recording medium corresponding to the guide layer, guiding the light from each light source to the objective lens, and the multilayer via the objective lens An optical system for separating reflected light from the optical information recording medium into reflected light from the guide layer and reflected light from the plurality of recording layers; reflected light from the guide layer separated by the optical system; A photodetector that receives light; An optical head comprising a; and a plurality of photodetectors for receiving a plurality of reflected light individually from the plurality of recording layers separated by the optical system.

  According to this, the light of the first wavelength and the plurality of light of the second wavelength in the multilayer optical information recording medium of the present invention are emitted from each light source, and the light of the first wavelength is emitted from the light source by the objective lens. The light is condensed on the guide layer of the information recording medium, and the plurality of lights having the second wavelength are condensed on the plurality of recording layers of the multilayer optical information recording medium corresponding to the guide layer. Each photodetector receives the reflected light from the guide layer and the reflected light from the plurality of recording layers individually. Therefore, it is possible to acquire a signal with high accuracy from the multilayer optical information recording medium of the present invention.

  According to a sixth aspect of the present invention, there is provided an optical drive device capable of reproducing at least one of information recording, reproduction and erasure with respect to the multilayer optical information recording medium of the present invention. A processing device for reproducing information recorded on the multilayer optical information recording medium using output signals of the respective photodetectors of the optical head.

  According to this, since the optical head of the present invention is provided, at least reproduction of information recording, reproduction and erasure can be accurately performed on the multilayer optical information recording medium of the present invention.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a cross-sectional view of an optical disc 15 as a multilayer optical information recording medium according to an embodiment of the present invention.

  The optical disk 15 shown in FIG. 1 has a cover layer C and three units (U1, U2, U3) stacked on the cover layer C. Here, the thickness direction of the optical disk 15 is taken as the Z-axis direction. The laser beam LB is irradiated from the −Z side of the optical disc 15.

  The cover layer C is disposed at the −Z side end of the optical disc 15. Accordingly, the surface on the −Z side of the cover layer C becomes the incident surface of the laser beam LB. The unit U1 is stacked on the + Z side of the cover layer C, the unit U2 is stacked on the + Z side of the unit U1, and the unit U3 is stacked on the + Z side of the unit U2.

  Each unit includes a guide track layer S and an information layer M.

  The guide track layer S corresponds to light having a wavelength in the range of 390 nm to 420 nm, and a guide spiral or concentric groove (track) is formed. Further, this track meanders (wobbles) at a predetermined cycle.

  The information layer M is arranged on the + Z side of the guide track layer S, and as shown in FIG. 2, is composed of five recording layers D and a resin layer G arranged between the recording layers. . That is, information is recorded and reproduced with respect to the five recording layers D by using one guide track layer S. In each unit, the guide track layer S is disposed closer to the incident surface than each recording layer.

  Each recording layer is made of a two-photon absorption material corresponding to light having a wavelength in the range of 650 nm to 680 nm, and information is recorded in a photon mode. As the two-photon absorption material, a photorefractive crystal, a photopolymer, or a photochromic material is used.

  In the photon mode recording, it is considered that a refractive index change occurs according to the light intensity distribution of the light spot, and pits are formed, and the spot diameter is about 0.71 times (= 1 / √) compared to normal recording. 2). As an example, as shown in FIG. 3, a pit (length: Dz2, width: Dr2) recorded by two-photon absorption is more than a pit (length: Dz1, width: Dr1) recorded by ordinary one-photon absorption. It can be seen that even if the light source wavelength is the same, recording can be performed with higher density than before (Teruhiro Shiono, “two-photon absorption recording of photochromic material using a semiconductor laser”, OPTRONICS, Optronics, July 2005, No. 283, p174). That is, the recording capacity can be increased. The horizontal axis in FIG. 3 is based on the center of the pit.

  Incidentally, in order to increase the recording capacity of the optical disc, the recording layer is multilayered, but it is also important to increase the recording capacity per recording layer. In order to increase the recording capacity per recording layer as much as possible, it is desirable to perform recording at a high density using light having a short wavelength as much as possible. However, at present, it is difficult to find a two-photon absorption material suitable for blue light. Therefore, it is preferable to use a two-photon absorption material suitable for green light and red light. However, since no semiconductor laser that emits green light is mass-produced at present, the two-photon absorption material for the recording layer D is red. A two-photon absorption material suitable for light was used. Even when red light is used, the spot diameter formed in the recording layer is 0.71 times (= 1 / √2) of the spot diameter formed in normal recording as described above. High-density recording at the same level as when recording is possible.

  The guide track layer S does not use a two-photon absorption material. This is because the two-photon absorbing material is deteriorated by irradiation with blue light to ultraviolet light, and ultraviolet light is emitted in a process that requires ultraviolet light (for example, 2P process), for example, when curing an ultraviolet curable resin or adhesive. This is because it is desirable not to use a two-photon absorption material for the irradiated layer.

  By the way, if the same red light as the recording layer is used for the guide track layer S, since there is no two-photon absorbing material, the spot diameter cannot be reduced and the recording capacity per recording layer cannot be increased. Since the spot diameter is generally proportional to the wavelength / the numerical aperture (NA) of the lens, if the light wavelength is shortened, the spot diameter can be reduced without a two-photon absorption material. Therefore, in the present embodiment, as an example, the light irradiated to the guide track layer S is blue light having a shorter wavelength than the wavelength of the light irradiated to the recording layer D. Thereby, the track pitch of the guide track layer S can be narrowed, and as a result, the recording capacity per recording layer can be increased. In addition, the recording capacity per optical disc can be dramatically increased. In addition, even when recording is performed at high density, it is possible to perform servo control with high accuracy.

  Further, by forming the guide track layer S and the plurality of recording layers D as a unit, it is possible to improve the so-called tilt stability. For example, if the thickness per recording layer is 3 μm, the thickness of the information layer M is 15 μm (= 3 μm × 5), and even when the optical disk 15 is tilted by 1 ° with respect to the light incident direction, the track deviation is zero. .. 26 μm. Even when the track pitch is set to 0.32 μm as in the case of an optical disc compliant with the Blu-ray standard, it is possible not to deviate from the original track, and recording and reproduction with sufficiently high reliability can be performed by performing conventional tilt control. In other words, the optical disk 15 satisfies the relationship expressed by the following equation (1). Here, n is the number of recording layers in the unit, d is the thickness of one recording layer, and p is the track pitch.

  n × d × sin (1 °) <p (1)

  That is, by adopting a structure in which the guide track layers S and the information layers M are alternately laminated, even if the total number of recording layers is large, the tilt stability is equivalent to that when the number of recording layers is small. Therefore, stable and reliable recording and reproduction can be performed.

  Next, an optical pickup device 23 as an optical head according to an embodiment of the present invention will be described with reference to FIGS.

  4 includes a light source LD1, a polarizing beam splitter 51, a collimator lens 52, an aberration correction optical element 53, a dichroic prism 54, a quarter wavelength plate 55, an objective lens 60, a light source LD2, and a detection lens 56. , A light receiving device PD1, a half mirror 59, a diffractive optical element 58, a collimator lens 57, a light receiving device PD2, a driving system (not shown) for driving the objective lens 60, and the like.

  The light source LD1 has a semiconductor laser that emits light having a wavelength of about 405 nm. The light source LD1 is arranged so that the maximum intensity emission direction of the emitted light is the + Z direction. As an example, light emitted from the light source LD1 is assumed to be P-polarized light. Hereinafter, the light emitted from the light source LD1 is also referred to as a “servo beam”.

  The polarization beam splitter 51 is disposed on the + Z side of the light source LD1. The polarization beam splitter 51 has a different reflectance depending on the polarization state of incident light. Here, for example, the polarization beam splitter 54 is set so that the reflectance with respect to the P-polarized light is small and the reflectance with respect to the S-polarized light is large. Therefore, most of the servo beam emitted from the light source LD1 can pass through the polarization beam splitter 51.

  The collimator lens 52 is disposed on the + Z side of the polarization beam splitter 51, and makes the servo beam transmitted through the polarization beam splitter 51 substantially parallel light.

  The aberration correction optical element 53 is disposed on the + Z side of the collimator lens 52 and corrects the aberration of incident light.

  The light source LD2 has a semiconductor laser array having at least five light emitting portions that emit light having a wavelength of about 660 nm. The light source LD2 is arranged so that five light beams are emitted in the -Y direction. As an example, it is assumed that each of the five light beams emitted from the light source LD2 is P-polarized light. Hereinafter, the light beam emitted from the light source LD2 is also referred to as a “recording / reproducing beam”.

  The half mirror 59 is disposed on the −Y side of the light source LD2 and bends a part of the optical path of incident light at a right angle.

  The diffractive optical element 58 is disposed on the −Y side of the half mirror 59 and diffracts incident light. Here, the five recording / reproducing beams transmitted through the half mirror 59 are converted by the diffractive optical element 58 so that the optical paths thereof are overlapped with each other and the divergence angles are different from each other.

  The collimator lens 57 is disposed on the −Y side of the diffractive optical element 58 and makes light from the diffractive optical element 58 substantially parallel light. However, since the five recording / reproducing beams from the diffractive optical element 58 have different divergence angles, the light that has passed through the collimator lens 57 is a mixture of parallel light, slightly divergent light, and slightly convergent light. become.

  The dichroic prism 54 is disposed on the + Z side of the aberration correcting optical element 53 and on the −Y side of the collimator lens 57, and bends the optical path of light having a wavelength of about 660 nm (here, a recording / reproducing beam) at a right angle. .

  The quarter wavelength plate 55 is disposed on the + Z side of the dichroic prism 54, and imparts an optical phase difference of a quarter wavelength to incident light.

  The objective lens 60 is disposed on the + Z side of the quarter wavelength plate 55 and condenses light from the quarter wavelength plate 55. Here, as shown in FIG. 5 to FIG. 7 as an example, five recording / reproducing beams LB2 are condensed on each recording layer of one unit, and the servo beam LB1 is a guide track layer of the unit. Condensed to S.

  The detection lens 56 is disposed on the + Y side of the polarization beam splitter 51 and gives astigmatism to the return light from the guide track layer S reflected in the + Y direction by the polarization beam splitter 51.

  The light receiver PD1 is disposed on the + Y side of the detection lens 56, and receives light from the detection lens 56.

  The light receiver PD2 is disposed on the −Z side of the half mirror 59, and receives the return light from the information layer M reflected by the half mirror 59 in the −Z direction.

  The drive system slightly drives the objective lens 60 in a tracking direction which is a direction perpendicular to the tangential direction of the track and a focusing actuator for slightly driving the objective lens 60 in a focus direction which is an optical axis direction of the objective lens 60. It has a tracking actuator.

  The operation of the optical pickup device 23 configured as described above will be briefly described. Here, it is assumed that the five recording layers D of the unit U2 of the optical disc 15 are recording layers to be accessed.

  The linearly polarized light (P-polarized light in this case) servo beam LB1 emitted from the light source LD1 is incident on the polarization beam splitter 51. Most of the servo beam LB1 incident on the polarization beam splitter 51 passes through the polarization beam splitter 51 as it is, and is made into substantially parallel light by the collimator lens 52, and then is aberration-corrected by the aberration correction optical element 53 and applied to the dichroic prism 54. Incident. The servo beam LB1 incident on the dichroic prism 54 passes through the dichroic prism 54 as it is, is made circularly polarized by the quarter wavelength plate 55, and is condensed on the guide track layer S of the unit U2 via the objective lens 60. .

  The reflected light from the guide track layer S of the unit U2 becomes circularly polarized light opposite to the outward path, and enters the quarter-wave plate 55 as return light through the objective lens 60, where it is linearly polarized light orthogonal to the forward path. (Here, S-polarized light). The return light then enters the polarization beam splitter 51 via the dichroic prism 54, the aberration correction optical element 53, and the collimator lens 52.

  The return light reflected in the + Y direction by the polarization beam splitter 51 is received by the light receiver PD1 through the detection lens 56. The light receiver PD1 includes a plurality of light receiving elements (or a plurality of light receiving regions) that output signals including wobble signal information and servo information (focus error information, track error information, and the like), as in a normal optical disk device. Has been. Each light receiving element (or each light receiving region) generates a signal corresponding to the amount of received light by photoelectric conversion.

  On the other hand, five recording / reproducing beams LB2 of linearly polarized light (here P-polarized light) emitted from the light source LD2 enter the half mirror 59. The five recording / reproducing beams LB2 transmitted through the half mirror 59 are incident on the dichroic prism 54 via the diffractive optical element 58 and the collimator lens 57, and the optical path is bent in the + Z direction by the dichroic prism 54, so that the ¼ wavelength is obtained. The light is made circularly polarized by the plate 55 and condensed on the five recording layers D of the unit U <b> 2 via the objective lens 60.

  The five reflected lights from the five recording layers D of the unit U2 are circularly polarized light opposite to the outward path, and enter the quarter-wave plate 55 as return light through the objective lens 60, and are orthogonal to the forward path here. Linearly polarized light (here, S-polarized light). These five return lights are reflected in the + Y direction by the dichroic prism 54 and enter the half mirror 59 via the collimator lens 57 and the diffractive optical element 58. The five return lights reflected in the −Z direction by the half mirror 59 are received by the light receiver PD2. The light receiver PD2 includes five light receiving elements (or five light receiving regions) that individually receive five return lights and output a signal including reproduction information. Each light receiving element (or each light receiving region) generates a signal corresponding to the amount of received light by photoelectric conversion. That is, signals from the five recording layers D can be read simultaneously.

  As described above, since the light receiver PD1 that receives the light including the servo information and the light receiver PD2 that receives the light including the reproduction information are separated, each of the light receivers can be optimized. Specifically, the low-speed receiver PD1 can be used, and the high-speed receiver PD2 can be used. In particular, since a low-speed receiver PD1 that receives light with a short wavelength with low sensitivity can be used, it is advantageous in assembling the system. In addition, since the servo beam may have a constant intensity regardless of whether it is recorded or reproduced, it is not necessary to provide a gain switching device in the light-receiving device PD1, and the circuit configuration can be simplified.

  In addition, a Si-Pin photodiode having a wide dynamic range can be used for the photodetector PD1, and an avalanche photodiode (APD) having a large multiplication factor can be used for the photodetector PD2. As a result, light including servo information that requires a wide dynamic range and linearity with respect to the amount of light can be detected with high accuracy by a Si-Pin photodiode, while weak light from the recording layer D having a low reflectivity can be detected. Light containing reproduction information can be amplified by an avalanche photodiode.

  Next, an optical disk device 20 as an optical drive device according to an embodiment of the present invention will be described with reference to FIG.

  An optical disk device 20 shown in FIG. 8 includes a spindle motor 22 for rotating the optical disk, an optical pickup device 23, a seek motor 21 for driving the optical pickup device 23 in the seek direction, a laser control circuit 24, and 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. Note that the arrows in FIG. 8 indicate the flow of typical signals and information, and do not represent the entire connection relationship of each block. The optical disk device 20 is assumed to be compatible with the optical disk 15 described above.

  The reproduction signal processing circuit 28 acquires address information, synchronization information, a focus error signal, a track error signal, and the like based on the output signal (a plurality of photoelectric conversion signals) of the light receiver PD1. Further, the reproduction signal processing circuit 28 acquires an RF signal or the like for each recording layer based on the output signals (five photoelectric conversion signals) of the light receiver PD2.

  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 a decoding process and an error detection process on each RF signal. When an error is detected, the reproduction signal processing circuit 28 performs an error correction process. Store in the buffer 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 drive system based on the servo signal from the reproduction signal processing circuit 28 and outputs the drive signal to the optical pickup device 23. Thereby, tracking control and focus control are performed. 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 disk 15 (recording data), data reproduced from the optical disk 15 (reproduction data), and the like. Data input / output to / from the buffer RAM 34 is managed by the buffer manager 37.

  Based on an instruction from the CPU 40, the encoder 25 takes out the recording data stored in the buffer RAM 34 via the buffer manager 37, modulates the data, adds an error correction code, and the like, and transfers it to the information layer M of the optical disc 15. Write signal is generated. For example, when recording is performed on five recording layers, five write signals are 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 each light source.

  For example, at the time of recording, the drive signal for the light source LD2 is generated based on the write signal, the recording conditions, the light emission characteristics of the semiconductor laser array of the light source LD2, and the like. For example, when recording is simultaneously performed on five recording layers, five drive signals are generated corresponding to the five light emitting units of the semiconductor laser array.

  The interface 38 is a bidirectional communication interface with a host device 90 (for example, a personal computer) and conforms to standard interfaces such as ATAPI (AT Attachment Packet Interface), SCSI (Small Computer System Interface), and USB (Universal Serial Bus). is doing.

  In the flash memory 39, various programs described by codes readable by the CPU 40, light emission characteristics of the semiconductor laser of the light source LD1, light emission characteristics of the semiconductor laser array of the light source LD2, recording conditions including recording power and recording strategy information, etc. Is stored.

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

<Recording process>
Next, processing (recording processing) in the optical disc device 20 when a user data recording request is received from the host device 90 will be described with reference to FIG. The flowchart in FIG. 9 corresponds to a series of processing algorithms executed by the CPU 40. Here, as an example, it is assumed that user data is recorded in a plurality of recording layers.

  When a recording request command is received from the host device 90, the start address of the program corresponding to the flowchart of FIG. 9 is set in the program counter of the CPU 40, and the recording process starts.

  In the first step 401, the drive control circuit 26 is instructed to rotate the optical disc 15 at a predetermined linear velocity (or angular velocity), and the reproduction signal processing circuit 28 is notified that the recording request command has been received from the host device 90. To do.

  In the next step 403, the recording request command is analyzed, and the recording layer and the recording target unit are specified based on the designated address. Then, the specified result is notified to the reproduction signal processing circuit 28, the drive control circuit 26, the encoder 25, the laser control circuit 24, and the like. Accordingly, the drive control circuit 26 drives and controls the objective lens 60 so that the servo beam LB1 is condensed on the guide track layer S of the recording target unit. Further, a light emitting unit to be driven in the light source LD2 and a light receiving element (or light receiving region) to be signal acquired in the light receiver PD2 are specified.

  In the next step 405, the drive control circuit 26 is instructed so that a light spot is formed near the target position corresponding to the designated address with reference to the address information obtained from the output signal of the light receiver PD1. Thereby, a seek operation is performed. If the seek operation is unnecessary, the process here is skipped.

  In the next step 407, recording is permitted. Thus, user data is recorded almost simultaneously on each recording layer to be recorded via the encoder 25, the laser control circuit 24, and the optical pickup device 23. During recording, the tracking control and focus control are performed at predetermined timings.

  In the next step 409, it is determined whether or not the recording is completed. If it is not completed, the determination here is denied and the determination is made again after a predetermined time has elapsed. If the recording is completed, the determination here is affirmed and the recording process is terminated. Here, since recording on a plurality of recording layers is performed almost simultaneously, the recording process can be completed in a single time as compared with the conventional case.

《Reproduction processing》
Next, processing (playback processing) in the optical disc device 20 when a playback request is received from the host device 90 will be described using FIG. The flowchart in FIG. 10 corresponds to a series of processing algorithms executed by the CPU 40. Here, as an example, information is reproduced from a plurality of recording layers.

  When a playback request command is received from the host device 90, the start address of the program corresponding to the flowchart of FIG. 10 is set in the program counter of the CPU 40, and the playback process starts.

  In the first step 501, the drive control circuit 26 is instructed to rotate the optical disc 15 at a predetermined linear velocity (or angular velocity), and the reproduction signal processing circuit 28 is notified that a reproduction request command has been received from the host device 90. To do.

  In the next step 503, the reproduction request command is analyzed, and the recording layer to be reproduced and the unit to be reproduced are specified based on the designated address. The identification result is notified to the reproduction signal processing circuit 28, the drive control circuit 26, the laser control circuit 24, and the like. Thus, the drive control circuit 26 drives and controls the objective lens 60 so that the servo beam LB1 is condensed on the guide track layer S of the unit to be reproduced. Further, a light emitting unit to be driven in the light source LD2 and a light receiving element (or light receiving region) to be signal acquired in the light receiver PD2 are specified.

  In the next step 505, the drive control circuit 26 is instructed to form a light spot near the target position corresponding to the designated address. Thereby, a seek operation is performed. If the seek operation is unnecessary, the process here is skipped.

  In the next step 507, reproduction is permitted. As a result, the data recorded on each recording layer to be reproduced is reproduced almost simultaneously via the optical pickup device 23 and the reproduction signal processing circuit 28. Then, the reproduction data stored in the buffer RAM 34 is transferred to the host device 90 when a predetermined data amount is reached.

  In the next step 509, it is determined whether or not the reproduction is completed. If it is not completed, the determination here is denied and the determination is made again after a predetermined time has elapsed. If the reproduction is completed, the determination here is affirmed, and the reproduction process is terminated. Here, since the reproduction from the plurality of recording layers is performed almost simultaneously, the reproduction process can be completed in a single time as compared with the conventional case.

  As is clear from the above description, a guide layer is realized by the guide track layer S in the optical disc 15 according to the present embodiment.

  Further, in the optical pickup device 23 according to the present embodiment, a light source that emits light of the first wavelength is realized by the light source LD1, and a light source that emits light of the second wavelength is realized by the light source LD2, and the light receiver PD1. Thus, a photodetector that receives reflected light from the guide layer is realized, and a plurality of photodetectors that individually receive a plurality of reflected lights from a plurality of recording layers are realized by the light receiver PD2.

  Further, in the optical disc apparatus 20 according to the present embodiment, a processing apparatus is configured by the reproduction signal processing circuit 28, the CPU 40, and a program executed by the CPU 40. 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 disc 15 according to the present embodiment, the guide track layer S (guide layer) corresponding to light having a wavelength (first wavelength) in the range of 390 nm to 420 nm and the range of 650 nm to 680 nm. A plurality of units in which a plurality of recording layers D made of a two-photon absorption material corresponding to light having a wavelength of (second wavelength) are stacked are stacked. This makes it possible to have tilt stability equivalent to that when the number of recording layers is small without causing a reduction in recording capacity.

  In addition, according to the optical disk 15 according to the present embodiment, a laser beam having a wavelength of 660 nm can be used for the recording / reproducing beam, and a laser beam having a wavelength of 405 nm can be used for the servo beam. Therefore, it is possible to realize an inexpensive optical pickup apparatus and optical disk apparatus that use the optical disk 15 as a target medium.

  Further, according to the optical disk 15 according to the present embodiment, since the guide track layer S is provided corresponding to the plurality of recording layers D, it is not necessary to form a guide groove in each recording layer, and the manufacturing process is performed. Can be simplified.

  Further, according to the optical disk 15 according to the present embodiment, the guide track layer S and each recording layer are separated. Thereby, even when blue light is used for the servo beam, a small condensing spot is not formed in the vicinity of the recording layer, and there is no fear that the two-photon absorption material that is weak against blue or ultraviolet light is deteriorated.

  Further, according to the optical disk 15 according to the present embodiment, the guide track layer S is disposed closer to the incident surface than the information layer M in one unit. As a result, even when blue light is used for the servo beam, the substrate thickness is reduced with respect to blue light, and in the optical pickup device 23, even if the optical disk 15 is inclined by about 1 ° with respect to the objective lens 60, Thus, it is possible to stably obtain highly accurate servo information. That is, the optical disk 15 is a multilayer optical information recording medium that is stable against tilt.

  In addition, according to the optical pickup device 23 according to the present embodiment, since a semiconductor laser that emits blue light is used as a light source that emits a servo beam, signals necessary for servo control can be accurately obtained from the optical disk 15. Can do.

  Further, according to the optical pickup device 23 according to the present embodiment, a semiconductor laser array that emits blue light is used as a light source that emits a servo beam, and a semiconductor laser array that emits red light is used as a light source that emits a recording / reproducing beam. Since it is used, size reduction and cost reduction can be achieved.

  Further, according to the optical pickup device 23 according to the present embodiment, light having a wavelength of about 405 nm is condensed at a position closer to the objective lens 60 than light having a wavelength of about 660 nm. Thereby, deterioration of the recording layer D of the optical disk 15 can be suppressed. In addition, since the refractive index of glass is often shorter when the wavelength is short, there is an advantage that the focal length can be shortened with respect to light having a short wavelength, and the objective lens can be easily designed. That is, an inexpensive lens corresponding to both short wavelength light and long wavelength light can be used as the objective lens by utilizing the chromatic aberration of the glass material.

  Further, according to the optical pickup device 23 according to the present embodiment, the light receiver that receives the reflected light of the servo beam and the light receiver that receives the reflected light of the recording / reproducing beam are individually arranged. Thereby, the response speed, gain, sensitivity, modulation characteristic, etc. of each light receiver can be optimized, and a good signal can be generated.

  Further, according to the optical disk device 20 according to the present embodiment, since the optical pickup device 23 is provided, it is possible to accurately perform at least reproduction of information recording, reproduction, and erasure on the optical disk 15. .

  In the above embodiment, the case where the number of units in the optical disk 15 is three has been described, but the present invention is not limited to this.

  In the above embodiment, the case where the number of recording layers included in one unit is five has been described, but the present invention is not limited to this. At this time, the number of light emitting portions of the light source LD2 may be changed according to the number of recording layers included in one unit.

  Further, as a multilayer optical information recording medium according to an embodiment of the present invention, as an example, a plurality of guide track layers (S1, S2, S3) on the + Z side of the cover layer C, as in the optical disc 15a shown in FIG. And a plurality of information layers (M1, M2, M3) may be stacked on the + Z side of the plurality of guide track layers. Here, the distance between the guide track layer S1 and the information layer M1, the distance between the guide track layer S2 and the information layer M2, and the distance between the guide track layer S3 and the information layer M3 are set to the same distance t. Yes.

  In this optical disc 15a, as shown in FIG. 12 as an example, the guide track layer S1 is used when recording and reproduction is performed on the information layer M1, and in the information layer M2 as shown in FIG. 13 as an example. On the other hand, when recording and reproduction are performed, the guide track layer S2 is used. As an example, as shown in FIG. 14, when recording and reproduction is performed on the information layer M3, the guide track layer S3 is used. Accordingly, in this case, the objective lens 60 is set so that the distance between the condensing position of the servo beam LB1 and the closest condensing position of the recording / reproducing beam LB2 is t.

  Further, in the optical disc 15a, the plurality of guide track layers are closer to the incident surface than the plurality of information layers, so that the servo beam does not pass through the recording layer D even when an interlayer jump occurs. Accordingly, since the reflected light (flare light) from the extra layer is not received during the interlayer jump, a stable servo signal can be obtained. That is, servo control can be performed at high speed without interruption.

  Further, in the optical disc 15a, the recording layer and the guide track layer are separated from each other, so that the manufacturing process can be simplified.

  In this case, as an example, as in the optical disc 15b shown in FIG. 15, light having a wavelength in the range of 390 nm to 420 nm is reflected at the boundary between the plurality of guide track layers and the plurality of information layers, and the range of 650 nm to 680 nm. You may arrange | position the filter layer F which permeate | transmits the light of the inside wavelength. As a result, the servo beam LB1 is completely reflected by the filter layer F and is not irradiated to the recording layer D made of the two-photon absorption material, and one of the causes of deterioration of the recording layer D can be eliminated. it can. As a result, highly reliable recording and reproduction can be performed.

  Further, as an example, like the optical disc 15c shown in FIG. 16, the plurality of guide track layers and the plurality of information layers may be used as a unit, and a plurality of the units (UN1, UN2,...) May be stacked.

  In the optical pickup device 23, the optical disk 15a is changed by changing the NA of the objective lens 60 by changing the effective diameters of the servo beam LB1 and the recording / reproducing beam LB2 according to t of the optical disk 15a. Can be easily accommodated.

  Moreover, in the said embodiment, the wavelength of the light radiate | emitted from light source LD1 should just be in the range of 390 nm-420 nm. The wavelength of the light emitted from the light source LD2 may be in the range of 650 nm to 680 nm.

  In the above embodiment, the guide track layer S corresponds to light having a wavelength in the range of 390 nm to 420 nm, and the recording layer D corresponds to light having a wavelength in the range of 650 nm to 680 nm. However, the present invention is not limited to this. In short, the guide track layer S and the recording layer D may correspond to light having different wavelengths. At this time, naturally, the light source LD1 emits light having a wavelength corresponding to the guide track layer S, and the light source LD2 emits light having a wavelength corresponding to the recording layer D.

  In the above embodiment, an optical disk device capable of recording and reproducing information has been described as an optical drive device. However, the present invention is not limited to this, and an optical disk capable of reproducing at least information among recording, reproducing, and erasing information is provided. Any device can be used.

  In the above embodiment, the case where recording and reproduction are simultaneously performed on a plurality of recording layers has been described. However, the present invention is not limited to this. For example, recording and reproduction may be performed on any one recording layer. In this case, the light source LD2 only needs to have one light emitting unit. The light receiver PD2 only needs to have one light receiving element (or light receiving region).

  In the above-described embodiment, the guide track layer S is described as having a groove for guiding. However, the present invention is not limited to this. For example, a guide pit (pre-pit) may be formed. good. Further, both grooves and pre-pits may be formed.

  In the above embodiment, the guide track layer S may be a recordable layer. As a result, the recording capacity can be further increased. Then, for example, a read-only program or security data may be recorded on the guide track layer S like a so-called hybrid disk. In this case, if recording is performed in accordance with the Blu-ray standard, a signal processing system used in an optical disc apparatus compliant with the Blu-ray standard can be used, and an inexpensive optical drive device can be realized. .

  In the above embodiment, information including information for specifying the guide track layer S such as a unit number may be recorded in the guide track layer S in advance. Thereby, the time required for so-called interlayer jump and access can be shortened.

  As described above, the multilayer optical information recording medium of the present invention is suitable for having a tilt stability equivalent to that in the case where the number of recording layers is small without causing a reduction in recording capacity. Also, the optical head of the present invention is suitable for acquiring signals with high accuracy from the multilayer optical information recording medium of the present invention. Also, the optical drive device of the present invention is suitable for performing at least reproduction of information recording, reproduction and erasure with high accuracy on the multilayer optical information recording medium of the present invention.

It is sectional drawing for demonstrating the structure of the optical disk 15 as a multilayer optical information recording medium based on one Embodiment of this invention. It is sectional drawing for demonstrating the information layer M in FIG. It is a figure for demonstrating the difference in the magnitude | size of the pit formed by the two-photon absorption, and the pit formed by the conventional system. It is a figure for demonstrating the optical pick-up apparatus as an optical head concerning one Embodiment of this invention. FIG. 5 is a diagram (part 1) for describing the optical pickup device of FIG. 4; FIG. 5 is a diagram (part 2) for explaining the optical pickup device of FIG. 4; FIG. 5 is a third diagram for explaining the optical pickup device in FIG. 4; It is a figure for demonstrating the optical disk device as an optical drive device concerning one Embodiment of this invention. FIG. 9 is a flowchart for explaining processing in the optical disc apparatus of FIG. 8 when a recording request is received from a host apparatus. FIG. 9 is a flowchart for explaining processing in the optical disc apparatus in FIG. 8 when a reproduction request is received from a host device. It is sectional drawing for demonstrating the optical disk 15a as a multilayer optical information recording medium based on one Embodiment of this invention. FIG. 12 is a diagram (No. 1) for explaining the converging positions of the servo beam and the recording / reproducing beam in the optical disc of FIG. 11; FIG. 12 is a diagram (No. 2) for explaining the converging positions of the servo beam and the recording / reproducing beam in the optical disc of FIG. 11; FIG. 13 is a diagram (No. 3) for explaining the converging positions of the servo beam and the recording / reproducing beam in the optical disc of FIG. 11; It is sectional drawing for demonstrating the optical disk 15b as a multilayer optical information recording medium based on one Embodiment of this invention. It is sectional drawing for demonstrating the optical disk 15c as a multilayer optical information recording medium based on one Embodiment of this invention.

Explanation of symbols

  15, 15a, 15b, 15c ... optical disc (multilayer optical information recording medium), 20 ... optical disc device (optical drive device), 23 ... optical pickup device (optical head), 28 ... reproduction signal processing circuit (part of processing device) 40 ... CPU (part of processing apparatus), 60 ... objective lens, LD1 ... light source (light source that emits light of the first wavelength), LD2 ... light source (light source that emits light of the second wavelength), D ... Recording layer, S ... Guide track layer (guide layer), F ... Filter layer, PD1 ... Light receiver (photodetector that receives light reflected from the guide layer), PD2 ... Light receiver (light reflected from the recording layer) Photodetector for receiving light), U1, U2, U3... Unit, UN1, UN2.

Claims (19)

  A multilayer optical information recording medium in which a plurality of units in which a guide layer corresponding to light having a first wavelength and a plurality of recording layers corresponding to light having a second wavelength different from the first wavelength are stacked are stacked.   The multilayer optical information recording medium according to claim 1, wherein the plurality of recording layers are stacked on one side of the guide layer. The light of the first wavelength and the light of the second wavelength are both incident through the same incident surface,
3. The multilayer optical information recording medium according to claim 2, wherein in the unit, the guide layer is disposed at a position closer to the incident surface than the plurality of recording layers. The guide layer is formed with a spiral or concentric track,
4. The number n of recording layers in the unit, the thickness d of one recording layer, and the pitch p of the track satisfy n × d × sin (1 °) <p. The multilayer optical information recording medium described in 1. A plurality of guide layers corresponding to light of the first wavelength;
And a plurality of recording layers corresponding to light having a second wavelength different from the first wavelength, stacked on the plurality of guide layers. The light of the first wavelength and the light of the second wavelength are both incident through the same incident surface,
6. The multilayer optical information recording medium according to claim 5, wherein the plurality of guide layers are disposed closer to the incident surface than the plurality of recording layers.   It further includes a filter layer that is disposed between the plurality of guide layers and the plurality of recording layers and reflects the light of the first wavelength and transmits the light of the second wavelength. The multilayer optical information recording medium according to claim 5 or 6.   A unit including a plurality of guide layers corresponding to light of a first wavelength and a plurality of recording layers corresponding to light of a second wavelength different from the first wavelength stacked on the plurality of guide layers; A multi-layered multilayer optical information recording medium. The light of the first wavelength and the light of the second wavelength are both incident through the same incident surface,
9. The multilayer optical information recording medium according to claim 8, wherein in the unit, the plurality of guide layers are disposed closer to the incident surface than the plurality of recording layers.   The multilayer optical information recording medium according to any one of claims 1 to 9, wherein information can be recorded on the guide layer.   11. The multilayer optical information recording medium according to claim 1, wherein information is recorded in advance on the guide layer.   12. The multilayer optical information recording medium according to claim 11, wherein the information recorded in advance on the guide layer includes information for specifying the guide layer.   The multilayer optical information recording medium according to claim 1, wherein the first wavelength is shorter than the second wavelength.   The multilayer optical information recording medium according to claim 13, wherein the first wavelength is a wavelength in a range of 390 nm to 420 nm, and the second wavelength is a wavelength in a range of 650 nm to 680 nm.   15. The multilayer optical information recording medium according to claim 1, wherein at least one of a guide groove and a pit is formed on the guide layer. An optical head compatible with the multilayer optical information recording medium according to any one of claims 1 to 15,
A light source that emits light of a first wavelength in the multilayer optical information recording medium;
A light source that emits light of a second wavelength in the multilayer optical information recording medium;
An objective for condensing the light of the first wavelength on the guide layer of the multilayer optical information recording medium and condensing the light of the second wavelength on the recording layer of the multilayer optical information recording medium corresponding to the guide layer. Including a lens, guiding light from each of the light sources to the objective lens, and reflecting light from the multilayer optical information recording medium via the objective lens as reflected light from the guide layer and reflected light from the recording layer An optical system that is separated into
A photodetector for receiving reflected light from the guide layer separated by the optical system;
And a photodetector for receiving reflected light from the recording layer separated by the optical system. An optical head compatible with the multilayer optical information recording medium according to any one of claims 1 to 15,
A light source that emits light of a first wavelength in the multilayer optical information recording medium;
A plurality of light sources respectively emitting light of a second wavelength in the multilayer optical information recording medium;
The light of the first wavelength is condensed on the guide layer of the multilayer optical information recording medium, and the light of the second wavelength is respectively applied to the plurality of recording layers of the multilayer optical information recording medium corresponding to the guide layer. A focusing objective lens that guides light from each of the light sources to the objective lens, and reflects reflected light from the multilayer optical information recording medium via the objective lens to the reflected light from the guide layer and the plurality of light sources. An optical system that separates into a plurality of reflected lights from the recording layer;
A photodetector for receiving reflected light from the guide layer separated by the optical system;
And a plurality of photodetectors that individually receive a plurality of reflected lights from the plurality of recording layers separated by the optical system.   The optical head according to claim 16, wherein the objective lens condenses the light having the first wavelength at a position closer to the objective lens than the light having the second wavelength. An optical drive device capable of reproducing at least one of recording, reproduction and erasure of information with respect to the multilayer optical information recording medium according to any one of claims 1 to 15,
An optical head according to any one of claims 16 to 18;
An optical drive device comprising: a processing device that reproduces information recorded on the multilayer optical information recording medium using an output signal of each photodetector of the optical head.

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