Abstract: The present invention provides an optical information medium capable of suppressing the influence of reflection light from an unnecessary information recording face and effectively eliminating spherical aberration at the time of recording/reproducing information to/from a recording medium having a plurality of information recording faces. When reflectance of an information recording face is ?h and transmittance between information recording faces is th, ?h and th of the optical information medium are set so as to satisfy ((?(h?1)2×?(h?2))/(th2×?h))<0.01.

Abstract: According to one embodiment, an optical recording medium is provided in which interlayer crosstalk is low and in which stable and high-quality recording characteristics can be obtained. To this end, an optical recording medium comprises a first recording part which includes a first recording layer and a first light reflecting layer and which is disposed on a side closer to a light receiving surface, and a second recording part which includes a second recording layer and a second light reflecting layer and which is disposed on a side farther from the light receiving surface, the first recording part and the second recording part being stacked, wherein the thickness of the first light reflecting layer is smaller than the thickness of the second light reflecting layer.

Abstract: An optical recording medium driving apparatus supporting an optical recording medium having multiple recording layers includes head means including a focusing mechanism and a spherical aberration correction mechanism; focusing control means for driving the focusing mechanism on the basis of a reflected light to perform focusing control on each recording layer; spherical aberration correcting means for driving the spherical aberration correction mechanism on the basis of a spherical aberration correction value to correct spherical aberration; and control means for controlling the focusing control means so as to set the spherical aberration correction value given by shifting the spherical aberration correction value appropriate for the midpoint between a target layer and a first recording layer by a desired value in the spherical aberration correcting means and controlling the focusing control means so as to perform the focusing control with the spherical aberration correction value after the shift being set.

Abstract: An optical disk apparatus can reliably detect the target recording layer of an optical disk having two recording layers. The optical disk apparatus is adapted to recording information on and reproducing information from an optical disk formed by sequentially laying a first recording layer, a second recording layer and a cover layer. The focal point of the light beam is moved closer to the optical disk from the side of the cover layer and the focal point of the light beam is determined to be coming close to the recording layer when the signal level of the focus error signal falls below a positive focus error threshold value after rising above the latter or rises above the negative focus error threshold value after falling below the latter.

Abstract: An optical disk apparatus for use with the combination type optical disk medium comprises an optical head capable of accessing the first and second recording layers and reading recording marks, a demodulator for applying a demodulation process to a signal read out of the first or second recording layer, an address converter for deciding from an optical disk reproduction instruction a recording layer to be accessed and performing conversion to a physical address of the recording layer, a reproduction controller following the recording layer determination and the physical address to control the optical head and the demodulator so as to control access and reproduction to and from the optical disk medium, and an instruction generator for generating an instruction to reproduce the optical disk.

Abstract: To prevent the focal point of a light beam from entering an unrecorded area, where no data has been written yet, when data is being read continuously from multiple storage layers. An optical disc drive can read data from an optical disc with at least first and second storage layers. The drive includes: a drive mechanism for rotating the disc; an optical pickup, which irradiates the disc in the drive mechanism with converged light and generates a read signal based on the light reflected from the disc; and a control section for controlling operations of the drive mechanism and the pickup, thereby shifting the focal point of the light. In reading data from the first and second layers continuously, the control section shifts the focal point in a first radial direction while data is read from the first layer and then moves the focal point to a location on the second layer before data starts to be read from the second layer.

Abstract: The present invention relates to an recording method for a multi-layered optical recording medium including M phase change recording layers, with M?2. The method comprises recording a mark in a Kth one of said recording layers by using a laser to irradiate the Kth recording layer using a recording pulse train including a plurality of laser beam pulses. The recording pulse train for the Kth recording layer has a cycle of t(K)[T], the 1st recording layer is the recording layer closest the laser beam, and the Mth recording layer is the recording layer furthest from the laser beam, T is a clock cycle. The following relationship is satisfied: t(1)<t(M), and the cycle of recording pulse train does not decrease from one recording layer to the next recording layer in the direction in which the laser beam irradiates.

Abstract: A recording apparatus for recording record data onto a recording medium on which a plurality of recording layers are formed in a thickness direction, is provided with: a recording device for recording the record data into each of the plurality of recording layers by emitting each of a plurality of recording light beams to be focused on a corresponding one of the plurality of recording layers; a calculating device for calculating a leaked beam feature of another recording light beam, which is emitted to be focused on another recording layer other than one recording layer of the plurality of recording layers, leaking to the one recording layer; and an adjusting device for adjusting an emission condition of at least one of the plurality of recording light beams, on the basis of the calculated leaked beam feature.

Abstract: A stamper which has a region information according to a destination is set to the resin molding machine for HDDVD and the resin molding machine for DVD, respectively. The contents information (contents A) of the same program is held in each stamper. The region information of each stamper is different according to the destination of contents information. Two disc substrates to which the information on each stamper is transferred are formed using the resin molding machine for HDDVD and the resin molding machine for DVD, and the reflecting layer is further formed on the transfer face of each substrate by sputtering. And as the reflecting layer side faces each other, each disc substrate is laminated. Thereby, hybrid type next-generation DVD from which the destination of the contents information of a HDDVD layer and a DVD layer is different is manufactured.

Abstract: An optical disk device for writing data into a disk including a plurality of recording layers, wherein the disk includes a recording layer in which a track for recording the data is formed in a clockwise spiral direction, and a recording layer in which a track for recording the data is formed in a counter-clockwise spiral direction, and the optical disk device records the data into a first recording layer, and selects a layer in which the data can be recorded and of which a spiral direction is opposite to the spiral direction of the first recording layer, as a recording layer for recording the data next to the first recording layer.

Abstract: A method and a device are disclosed for reducing a perceived discontinuity in a continuous digital information stream read back from a first (LO) and a second (L1) layer of a multi-layer record carrier (104), said discontinuity occurring during the transition from the first (LO) to the second (L1) layer. The method comprises the steps of monitoring (S1) said digital information stream to be recorded on said multi-layer record carrier (104), determining (S2) a time (ti) corresponding to a point in said digital information stream where an effect of a perceived discontinuity is reduced, and recording (S3) said digital information stream such that a transition from recording on the first layer (LO) to recording on the second layer (L1) of the multi-layer record carrier (104) occurs at said determined time (ti), thereby reducing perceived discontinuity that occurs in, for example, a read back device with a relatively small data buffer.

Abstract: When it is determined that the disc loaded on a player is a hybrid next generation DVD, the DVD layer is reproduced with a red laser light. In parallel with this reproduction process, a process for notifying the presence of the HDDVD layer is performed. That is, determination is made on whether the notification timing defined in advance has been reached. If the notification timing has been reached, a control instruction is output from a controller to an AV processing circuit, and the image information including the image notifying the presence of the HDDVD layer is output from the AV processing circuit. Thus, the user may learn that the HDDVD layer can be reproduced.

Abstract: When a hybrid type next-generation DVD is loaded in the optical disc device, first, a red laser is turned on and parameter value and a lead-in information with respect to a DVD layer are acquired. The acquired information is stored in a memory. Next, a blue laser is turned on, parameter value and a lead-in information to a HDDVD layer are acquired, and the acquired information is stored in a memory. Then, the HDDVD layer is reproduced while lighting of the blue laser beam is maintained. Then, when a jump instruction to the DVD layer is inputted, the parameter value for the DVD layer is read from the memory and set to a process system. And the lighting laser is changed to the red laser and reproduction of the DVD layer is performed based on the lead-in information of the DVD layer stored in the memory.

Abstract: An optical recording medium to be used for a retail activation solution is proposed. The optical recording medium is a modified ROM disk that can only be played after the application of an activation process. For this purpose at least a part of a reflective layer of a read-only area of the optical recording medium is replaced by a light sensitive layer stack that changes its reflectivity upon illumination. Also proposed are a method for producing such an optical recording medium as well as methods and apparatuses for initializing and/or activating such an optical recording medium.

Abstract: According to the present invention, the size of defect management information is reduced by using a top spare area 102 and middle spare areas 103 in the ascending order of their physical block addresses and spare areas can be expanded more easily by using only the last spare area 104 in the descending order of its physical block addresses.

Abstract: The invention relates to an optical data carrier which combines a CD layer with at least one further format, such as a DVD layer for example. If a hybrid data carrier of this kind is to be produced in a thickness of less than 1.7 mm, and preferably in a thickness of 1.5 mm or less, then, seen from the surface which is to be read from, the CD layer will normally be situated at a depth of considerably less than 1.1 mm, and the CD substrate therefore has to be thinned down. The quality of the reading signals obtained is increased by increasing the length of the optically readable structures of the CD layer in comparison with the values which are usual in this case. Because of the difficulties which certain CD players have in focussing when the substrates are thin, the refractive index of the disc material used is reduced from the figure for polycarbonate, at least in the case of the CD substrate, the recommended range being between 1.40 and 1.55.

Abstract: An optical system has an objective lens condensing a light beam from the light source on a recording layer selected from the plurality of recording layers of the optical disk, and leading a returning light beam reflected by the selected recording layer to a predetermined position; an aberration detecting part detecting a physical amount relative to spherical aberration based on an output signal of the photodetector; an aberration correcting part correcting the spherical aberration based on the physical amount; and a processing device carrying out at least the information reproduction o from among information recording, information reproduction and information deletion with the use of the output signal of the photodetector.

Abstract: An optical disk device is provided with an optical pickup that includes a convergent optical system having an objective lens for converging a light beam emitted from the laser light source to form a microspot on an optical disk and an aberration correcting optical system for controlling a spherical aberration of the convergent optical system, and performs information recording or reproduction with respect to a multi-layer optical disk having at least a first recording layer and a second recording layer. In the optical disk device, an operation of changing a correction quantity of the spherical aberration from a value adequate for the first recording layer to a predetermined value is started before an operation of moving a focus position of the microspot from the first layer to the second layer is completed.

Abstract: An optical information medium measurement method of the present invention, for measuring a degree of modulation in an optical information medium of a multilayered structure having a plurality of information layers, includes a first step of measuring the modulation degree of each layer of the optical information medium, by use of a measurement optical system, a second step of obtaining a thickness between layers of the optical information medium, a third step of obtaining a reflectance of each layer of the optical information medium, and a fourth step of converting the modulation degree of each layer, the modulation degree being measured in the first step, into a modulation degree at a reference optical system differing from the measurement optical system, based on a value indicative of the thickness between layers, the thickness being obtained in the second step, and a value indicative of the reflectance of each layer, the reflectance being obtained in the third step.

Abstract: In a method for recording information on an information recording medium having a data recording area for storing user data and a test area used for test recording by a recording apparatus, it is detected whether the test area is unusable when executing the test recording. The test recording is executed in the test area when the test area is detected not to be unusable, or executed in the data recording area when detected to be unusable. Management information relating to the test recording executed in the data recording area is recorded in a predetermined area. Hence, it is possible to eliminate a limit of number of times of test recording which depends on the size of the test recording area.

Abstract: The present invention has an object of providing an optical information recording medium including three or more information layers, which allows information to be reproduced from all the information layers at high quality, and a method for reproducing information from such an information recording medium. The reflectance of a third information layer 43 is made higher than that of each of a second information layer 42 and a first information layer 41. Thus, the upper limit reproduction power of laser light 31 directed to the third information layer 43 can be made lower than that of the laser light 31 directed to each of the second information layer 42 and the first information layer 41. For reproduction, the reproduction power of each information layer is equal to or lower than the upper limit reproduction power, and a product of the reflectance and the reproduction power is substantially the same among the information layers. Thus, the information reproduction can be conducted at high quality.

Abstract: The number of recording layers of the loaded disc is determined using the blue laser light. If the number of recording layers is two, drawing is performed in the recording layer on the near side when seen from the laser light entering side, and demodulation is performed with the HDDVD decoder. If demodulatable, the disc is determined as a disc in which two HDDVD layers are arranged. If not demodulatable, determination is made on whether or not the data of the recording layer is demodulatable with the DVD decoder. If demodulatable with the DVD decoder, the laser light is switched to the red laser light and the number of recording layers is determined. If two recording layers are detected in this determination, the disc is determined as a disc in which two DVD layers are arranged. On the other hand, if one recording layer is detected, the disc is determined as a hybrid HDDVD in which one HDDVD layer and one DVD layer are arranged.

Abstract: A recording apparatus to record data on a recording medium including a plurality of recording layers is provided. The recording apparatus includes a recording circuit adapted to record data on a recording layer selected from among the plurality of recording layers included on the recording medium; a recordable capacity detecting circuit adapted to detect recordable capacity of each of the plurality of recording layers; an instructing circuit adapted to provide instructions to start recording of the data; and a selecting circuit adapted to select a recording layer on which the data is to be recorded in accordance with the instructions to start recording provided from the instructing circuit based on the recordable capacity of the plurality of recording layers detected by the recordable capacity detecting circuit.

Abstract: A method of recording control information in a recording medium, such as an optical disc, including at least one recording layer is provided Velocity information and per recording velocity write strategy (write strategy parameters) is included in control information, such that standardized control information can be uniformly applied to cope with the playback of a recorded optical disc. The method includes steps of recording, per applicable recording velocity, the control information within a management area of the at least one recording layer of the optical disc; and recording at least one write strategy information per the applicable recording velocity within the control information.

Abstract: An optical record carrier (30) comprising a plurality of information layers formed above a first surface of a substrate wherein at least one of the information layers is a re-writable cache layer is disclosed. The data that is read more than once is copied on to the re-writable cache layer when the recording/reproducing device is not in active use. Next time when the same data is requested, it can be read from the re-writable cache layer. This is advantageous since the data is stored un-fragmented on the re-writable cache layer and the re-writable cache layer can have higher read speeds than the other information layers in the optical record carrier. Therefore, the re-writable cache layer can improve the system performance in terms of read speed.

Abstract: A multi-layered information recording medium including a plurality of recording layers, the multi-layered information recording medium comprising: a user data area for recording user data; and a plurality of spare areas including at least one replacement region, wherein when the user data area includes at least one defect region, the at least one replacement region may be used in place of the at least one defect region, wherein a first spare area of the plurality of spare areas is positioned so as to be contiguous to a first user data area of a first recording layer, a second spare area of the plurality of spare areas is positioned so as to be contiguous to a second user data area of a second recording layer, and the first spare area and the second spare area are positioned approximately at the same radial position on the multi-layered information recording medium.

Abstract: An optical disc according to the present invention includes a plurality of recording layers; a receiving section for receiving, from outside an optical disc, a switching instruction for switching a target layer to be targeted for recording or reproducing information among the plurality of the recording layers; and a switching section for switching the target layer among the plurality of recording layers, based on the switching instruction received.

Abstract: The present invention relates to a method and apparatus for finalizing a dual layer disc medium. The present invention checks whether particular areas on each recording layer of a dual layer recording medium separated from each other, e.g., the innermost circumference of data zone and around an area of radius 4 cm, are unrecorded and records null data in a particular area found to be unrecorded and carries out finalization. The present invention has an advantage in that time needed for finalization is considerably reduced compared with a traditional procedure of recording null data throughout the entire unrecorded data section.

Abstract: A multi-layered information recording medium including a plurality of recording layers, the multi-layered information recording medium comprising: a user data area for recording user data; and a plurality of spare areas including at least one replacement region, wherein when the user data area includes at least one defect region, the at least one replacement region may be used in place of the at least one defect region, wherein a first spare area of the plurality of spare areas is positioned so as to be contiguous to a first user data area of a first recording layer, a second spare area of the plurality of spare areas is positioned so as to be contiguous to a second user data area of a second recording layer, and the first spare area and the second spare area are positioned approximately at the same radial position on the multi-layered information recording medium.

Abstract: The present invention provides a novel physical structure for a multilayer optical information recording medium including a plurality of information recording layers, and a recording method and a recording/reproduction apparatus for such a recording medium using the same. The multilayer optical information recording medium according to the present invention includes a test recording area for performing test recording for data recording and/or reproduction conditions in at least one of an inner zone and an outer zone. The test recording area is categorized as one of at least two categories of test recording areas (OPC-A area and OPC-B area). In the OPC-B area, an upper limit value is set on a recording power for the test recording.

Abstract: An information recording medium having at least a read only area and a recording and reproducing area is composed of at least: a substrate; a recording layer formed on the substrate so as to record and reproduce information; and a light transmission layer having transparency formed on the recording layer. The information recording medium is further characterized in that a wobbling groove corresponding to the read only area and another wobbling groove corresponding to the recording and reproducing area is formed on the substrate without overlapping with each other, the recording and light transmitting layers are continuously adhered over at least two areas of the read only area and the recording and reproducing area, reflectivity of the recording layer is more than 5%, and a push-pull signal output T3 reproduced from the read only area and another push-pull signal output T4 reproduced from the recording and reproducing area before recording satisfies relations of T3?0.1, T4?0.1 and 1.5?T3/T4?0.5.

Abstract: An information recording method for a multi-layered optical recording medium that can form information recording layers in 3 layers or more. When all the information recording layers are blank, the information recording layer that is the closest to the light incident surface is irradiated with a laser beam to start recording. High quality information recording is thus implemented in consideration of adherence of foreign matters and occurrence of scratches.

Abstract: An information recording medium (100) is provided with: a first recording layer (L0 layer) and a second recording layer (L1 layer) in each of which record information can be recorded, the information recording medium includes a plurality of block areas, each of which is a unit of recording the record information and each of which includes a partial recording area of the first recording layer (105a) and a partial recording area of the second recording layer (115a) located in a position facing the partial recording area of the first recording layer.

Abstract: An information recording medium (100) includes (i) a first recording layer (L0 layer) having a first track and (ii) a second recording layer (L1 layer) having a spiral or coaxial second track sharing the rotation center with the first track. (iii) The first recording layer has a first point (point Bx) indicated by a first address. (iv) The second recording layer has a second point (point Dx) which can be defined according to a predetermined positional relationship (allowable area: 10) with respect to the first point (point Bx).

Abstract: A first data-recorded region is formed in one of multiple recording layers of a rewritable optical disc before a second data-recorded region is formed therein. A first on-disc position is related to an innermost position within the second data-recorded region. Information is reproduced from a recording management area of the disc. A second on-disc position is derived from the reproduced information. The second on-disc position is in substantial coincidence with an outermost position within the first data-recorded region. The first on-disc position and the second on-disc position are compared to decide whether an unused portion is present in or absent from a region therebetween. When the unused portion is present, padding data is recorded thereon. The second on-disc position is updated into substantial coincidence with an outermost position within the second data-recorded region. The information in the recording management area is updated to reflect the updated second on-disc position.

Abstract: There are provided an optical recording method, an optical recording apparatus, a one-chip CPU device, and a computer program. Reference data corresponding to a recording condition of a first recording layer, a physical characteristic value correlated with the recording condition, and a physical characteristic value correlated with a recording condition of a second recording layer are extracted from a data table in a memory, and the recording condition of the extracted reference data is set as a recording condition of a recording medium as an information recording target. When no correlated reference data exists, the closest reference data are extracted from the data table, and a recording pulse condition suitable for recording information on the second recording layer of an optical disk as the information recording target is extracted on the basis of the correlation between the recording condition of the reference data and the physical characteristic value.

Abstract: The same contents having different recording rates are recorded on a multi-layer disk. A plurality of contents or the same contents having different recording rates are independently recorded respectively in different layers of an optical disk having a plurality of recording layers. In order to record a plurality of contents or the same contents having different recording rates in parallel at that time, recording on the multi-layer optical disk is conducted by repeating an operation of dividing each content into recording units, recording a recording unit of one kind of information in a recording layer, and recording a recording unit of the other kind of information in a different recording layer.

Abstract: A system and method in which read information is calculated with additional information as a coefficient and has superior in quality to basic information. The read information contains a larger amount of information than the basic information. So, even if an attempt is made to record the read information as it is to any other recording medium, the recording medium having a sufficiently large capacity for storage of the read information. Thus, copy of recorded data in the recording medium to any other recording medium is difficult.

Abstract: The present invention provides a method of recording disc control information in a recordable optical disc including at least one recording layer, and more particularly, a method of recording information indicating a specific location of disc control information within the disc control information itself and a method of searching requested disc control information, thereby enabling to uniformly apply the standardized disc control information to efficiently cope with the record/playback of the optical disc and to efficiently search a plurality of disc informations.

Abstract: An information reproducing device reproduces information in an information recording medium provided with, in addition to a first recording layer readable by a first laser beam, at least one of a second recording layer readable by a second laser beam, and a third recording layer readable by a third laser beam. The information reproducing device includes an optical pickup element applying a laser beam and receiving its reflection; a first judging element first determining whether the first recording layer exists, based on an output from the optical pickup element; a second judging element secondly determining on either of the recording layers is set by a user as a prioritized reproducing layer to be reproduced first; a reproducing element reproducing recorded information; and a control element controlling the reproducing element to reproduce the recorded information, based on outputs from the first judgment element, second judgment, and optical pickup elements.

Abstract: An optical recording medium having a plural number of recording layers includes a n-th recording layer (23) (n?1), made up by a substrate (20) and a semi-reflective layer (21) carried by the substrate (20) and adapted for partially reflecting and partially transmitting the incident light, a (n+1)th recording layer (28), made up by another substrate (25) and a reflecting layer (26) carried by the substrate (25) and adapted for reflecting the incident light, and a light condensing layer (24) for condensing the light incident via the n-th recording layer (23) on the (n+1)th recording layer (28).

Abstract: An optical disc, and a recording/reproducing method and apparatus to record information on the optical disc. The optical disc includes an optical information storage layer, including a layer format region and a user data region. The layer format region is divided into virtual layers that are disposed at different depths. The virtual layers include layer information to distinguish the virtual layers from one another.

Abstract: A disk has a plurality of recording layers in a laminated direction. When a defect occurs in any one of recording layers during disk manufacture, information about the defect is recorded in a read-only region in the recording layer. An optical disk apparatus determines which of the recording layers is usable based on the information about the defect read from the disk, and executes a recording/reproducing operation according to a determination result. Therefore, even when a disk with a defect in the recording layer is used, that disk may be offered to a user as an appropriately usable disk.

Abstract: An information recording medium having at least a read only area and a recording and reproducing area is composed of at least: a substrate; a recording layer formed on the substrate so as to record and reproduce information; and a light transmission layer having transparency formed on the recording layer. The information recording medium is further characterized in that a wobbling groove corresponding to the read only area and another wobbling groove corresponding to the recording and reproducing area is formed on the substrate without overlapping with each other, the recording and light transmitting layers are continuously adhered over at least two areas of the read only area and the recording and reproducing area, reflectivity of the recording layer is more than 5%, and a push-pull signal output T3 reproduced from the read only area and another push-pull signal output T4 reproduced from the recording and reproducing area before recording satisfies relations of T3?0.1, T4?0.1 and 1.5?T3/T4?0.5.

Abstract: A method of inter-layer search of a multi-layer disk, the method including determining whether a search is required of a layer other than a currently accessed layer; searching the currently accessed layer for a position corresponding to a target address on the layer not currently accessed; and moving access to the layer not currently accessed according to the position corresponding to the target address.

Abstract: A fabrication method of a multilayer optical recording medium having a plurality of recording layers, comprises a step of preparing an optical recording medium having at least one record area; a write-position mark generating step of recording write-position marks in the record area beforehand; a step of preparing an optical system including a common objective lens to focus a data recording beam and a position mark recording beam on different positions in a thickness direction of the record area; a first data writing step of writing data between the write-position marks with following the write-position marks by the data recording beam; a position mark recording step of, in parallel with the first data writing step, recording new write-position marks in the record area by the position mark recording beam; and a second data writing step of writing data between the new write-position marks with following the new write-position marks by the data recording beam.

Abstract: A hybrid disk useable with a recording and or reproducible apparatus having an optical pickup. The hybrid disk includes a first recording layer having a first format on which data is recordable or readable by a first format beam and a second recording layer having a second format on which the data is recordable or readable by a second format beam. The transmivities and reflectivities of the first and second recording layers are interrelated to control relative intensities of the first and second format beams incident on the optical pickup.

Abstract: Information is recorded on a multi-layered optical recording medium by irradiating it with a laser beam. The recording medium can form a first information recording layer that is the farthest from a light incident surface, a second information recording layer that is the second farthest from the light incident surface, and at least one third information recording layer that is located closer to the light incident surface than the second information recording layer is. At this time, if all the information recording layers other than the first information recording layer are either blank or have been completely recorded, then information is recorded on the first information recording layer. This allows for stabilizing the energy of a recording laser beam during recording and thereby providing improved recording quality.

Abstract: An information recording medium is provided, which comprises a plurality of recording layers and a first disc information area for storing parameters relating to access to the plurality of recording layers and formats relating to the plurality of recording layer. The first disc information area is provided in a first recording layer which is one of the plurality of recording layers.

Abstract: When recording or reading an optical disc having plural data recording layers, which data recording layer the light spot is focused on is detected to improve playback signal quality and signals written to the layer on which the light spot is focused are read more reliably. A convergent lens converges the laser beam on the optical disc, and a focus controller controls the focal point of the laser beam on the data layer. A tracking controller positions and tracks the focal point of the laser beam converged by the convergent lens on a track of the optical disc. A photodetector detects the reflected laser beam from the disc. A convergence detector then detects the convergence state of the laser beam emitted to the plural data recording layers. Based on output from the convergence detector, the laser driver is controlled to separately set beam power appropriately for each of the plural data layers of the disc during playback.