Abstract: According to one embodiment, a storage medium includes a burst cutting area at an inner periphery, wherein the burst cutting area has includes plural burst-cutting-area data areas.

Abstract: In an optical information reproduction apparatus having optical beam sources having at least two types of wavelengths, an object lens may be damaged by colliding with an information recording medium while driving a focus servo, which is caused by a fake signal generated due to an incompatibility of the wavelength in use with the information recording medium. To solve such a problem, in case the type of the information recording medium is unrecognizable and a focus servo is led in by using the optical beam source having the first wavelength, the focus servo is led in by using the second focus servo lead-in unit which is driven by an output of a near focus point detection unit during an operation of a second focus search unit which renders the object lens move away from the information recording medium.

Abstract: A method for recording a plurality of data sets onto an optical storage medium by utilizing a temporary storage device in an optical storage system includes storing a plurality of data sets corresponding to a plurality of defective data blocks in the memory into the temporary storage device; re-arranging a sequence of the plurality of data sets corresponding to the plurality of defective data blocks in the temporary storage device according to a sorting process; and recording the plurality of re-arranged data sets in the temporary storage device into a spare storing section; and recording the plurality of re-arranged data sets in the spare storing section into corresponding spare data blocks in an optical storage medium.

Abstract: A reproduction method and apparatus for reproducing video data and/or audio data from a recordable medium having video data and/or audio data recorded thereon. The video data and/or audio data is generated by superimposing information concerning an attribute of a video signal and/or an audio signal on a signal of digitized video data and/or a signal of digitized audio data. Information concerning a copyright superimposed on the video data and/or audio data is reproduced from the medium, and a type of the medium is identified. Reproduction is stopped in response to a determination that the medium is illegally produced, the determination being based on a combination of the information concerning a copyright which is reproduced and the type of the medium identified.

Abstract: In an optical recording medium drive apparatus, an optical recording medium is illuminated with a laser beam emitted from a head via an objected leans, and the head detects light reflected from the optical recording medium being illuminated with the laser beam. A signal generator generates a reflected light signal in accordance with the reflected light detected by the head. A controller drives the objective lens via a focusing unit, and detects peaks in the reflected light signal obtained when the objective lens is driven in a focusing direction. The controller determines whether the optical recording medium is of a single layer type or a multiple layer type by determining whether a pattern of the detected peaks is similar to one of patterns which can occur if the optical recording medium is of the single layer type.

Abstract: Expiration information stored on an optical medium is applied to determine an expiration date of the optical medium that provides a predetermined reliability of information archived on the optical medium, such as a predetermined acceptable defect level of the information at the expiration date. An expiration engine associated with an information handling system or optical disc drive determines the expiration date from one or more factors, such as the manufacture date of read-only optical media, the initialization date of recordable optical media, a quality rating associated with a defect growth rate over time of the optical media, and a desired reliability. In one embodiment, the expiration engine writes expiration information to the optical media, such as a date stamp at initialization of a recordable optical medium. Alternatively, an expiration date is stored on an information handling system to provide expiration warnings a predetermined time before the expiration date.

Abstract: An information layer 0 comprises a system lead-in area, data lead-in area, data area, and middle area, an information layer 1 comprises a system lead-out area, data lead-out area, data area, and middle area, an end position of the data area of layer 1 is positioned outer than a start position of the data area of layer 0, the data lead-in area comprises a guard track zone wider than a test zone in the data lead-out area, the data lead-out area comprises a guard track zone wider than a test zone and a management zone in the data lead-in area, the middle area of layer 0 comprises a guard track zone wider than a test zone in the middle area of layer 1, and the middle area of layer 1 comprises a blank zone wider than a test zone in the middle area of layer 0.

Abstract: According to one embodiment, a storage medium includes a burst cutting area at an inner periphery, wherein the burst cutting area has includes plural burst-cutting-area data areas.

Abstract: A method of recording writing speed information and per writing speed write strategy information within disc control information is provided. The standardized disc control information can be uniformly applied to efficiently cope with the record/playback of the optical disc. In configuring disc control information within a management area of an optical disc including at least one recording layer, the method includes steps of providing the at least one disc control information within the management area, the disc control information provided per applicable writing speed to each of the at least one recording layer; and recording applicable recording speed information within the disc control information.

Abstract: An object of the present invention is to provide an optical recording/reproducing apparatus capable of improving medium usability through a laser power adjusting process while keeping compatibility with a read only type medium. The optical recording/reproducing apparatus adjusts laser power using a PCA till the PCA is used up. After the PCA is used up, an additional area is reserved at the outermost circumference position, thereafter when the additional area is used up, a new additional area is reserved at an inner circumference side of the used up additional area to adjust laser power. The additional area is reserved at an outer circumference than a lead-out area, and therefore format compatibility with a read only type optical disc can be maintained. The additional area is reserved only when the PCA is used up, thus capacity compatibility with a read only type optical disc can be maintained while laser power is adjusted with only the PCA.

Abstract: An information recording method records information to a multilayer recording medium in which a number of record layers are laminated and recording of information to each record layer is possible. When an amount of the information being recorded to the medium does not exceed a maximum amount of information which can be recorded to the medium, the information being recorded to the medium is divided into data blocks by the number of the record layers. The data blocks are recorded to data areas of the respective record layers so that the recording areas of the record layers where the data blocks are recorded are overlapped each other with respect to a thickness direction of the medium.

Abstract: A method of recording read/write compatibility information on an optical disc and a recording medium employing the method. Extended part version information, latest part version having recording capability, and latest part version having reproducing capability are stored in n.xy form on 6 bytes of a reserved zone of a physical format information zone of the optical disc. A recording/reproducing apparatus to record extended part version information on a reserved zone of a physical format information zone of a recording medium. The recording/reproducing apparatus has a base part version and a comparing unit to determine recording/reproducing compatibility with a recording medium having a detailed extended part version stored in a reserved zone of a physical format information zone.

Abstract: A recording device, which writes data to a recording medium in which a data area and a middle area are disposed adjacent to each other, includes: an area expanding unit expanding the middle area to reduce the data area; a first writing unit writing data to the reduced data area; and a second writing unit writing a terminator to a vacant area of the data area to which the data has been written.

Abstract: A diffraction element is interposed between a semiconductor laser and collimator lens. Other diffracted light than zero-order light output from the diffraction element will not be focused on an optical recording medium and the amount of light condensed to the focus of the zero-order light is thus smaller. The diffraction element is variable in diffraction efficiency. When the diffraction efficiency of the diffraction element is raised, an optical pickup device will utilize the light with a lower efficiency. With the diffraction efficiency being lowered, the optical pickup device will utilize the light with a higher efficiency. Thus, the optical pickup device can utilize the light with a variable efficiency without having to being designed larger.

Abstract: This optical disk device includes a pickup head, a spindle motor, a signal generation unit, a runout amount calculation unit, and an out of balance disk detection unit. The signal generation unit generates a tracking error signal. The runout amount calculation unit controls the rotational speed of the spindle motor to first and second disk rotational speeds, and obtains, at these rotational speeds, runout amounts TE1 and TE2 of a tracking error signal, and runout amounts FE1 and FE2 of a focus error signal. And an out of balance disk detection unit detects that this optical disk is an out of balance disk, if the absolute value of (TE2×FE2)/(TE1×FE1) is greater than or equal to a threshold value.

Abstract: A method of determining a type of a disc for a disc system to record/reproduce a plurality of recordable discs having different track pitches, including detecting a plurality of signals for determination while moving an objective lens up or down and simultaneously making the objective lens vibrate in a radial direction of the disc, and determining the types of the discs having different track pitches by using the detected signals for determination.

Abstract: A record carrier has a track pattern of substantially parallel tracks. Control data packs are stored repetitively in several control locations (32) for protection against damage and contamination. The control locations (32) are separated at spacer positions (33) by one or more spacers (34,35). The length of the spacers (34,35) is selected for preventing overlap of the position of the first block of the control data packs in the parallel tracks.

Abstract: The amount of light reflected from a disk is detected, and it is determined according to the amount of reflected light whether the disk is a recordable disk or a rewritable disk. The disk is controlled according to the result of determination such that it is rotated at a constant angular velocity (CAV) or at a constant linear velocity (CLV) and recording is executed. Further, rotation driving control of the disk is selected according to factors other than the type of the disk, such as according to whether random recording is allowed or not, according to a recording state in the disk, according to whether an alternative area is provided or not, according to a recording start position, or according to whether initialization is required or not. CLV control or CAV control is appropriately selected for a disk at recording to suppress a reduction in accessibility and a reduction in data transmission rate.

Abstract: The amount of light reflected from a disk is detected, and it is determined according to the amount of reflected light whether the disk is a recordable disk or a rewritable disk. The disk is controlled according to the result of determination such that it is rotated at a constant angular velocity (CAV) or at a constant linear velocity (CLV) and recording is executed. Further, rotation driving control of the disk is selected according to factors other than the type of the disk, such as according to whether random recording is allowed or not, according to a recording state in the disk, according to whether an alternative area is provided or not, according to a recording start position, or according to whether initialization is required or not. CLV control or CAV control is appropriately selected for a disk at recording to suppress a reduction in accessibility and a reduction in data transmission rate.

Abstract: The amount of light reflected from a disk is detected, and it is determined according to the amount of reflected light whether the disk is a recordable disk or a rewritable disk. The disk is controlled according to the result of determination such that it is rotated at a constant angular velocity (CAV) or at a constant linear velocity (CLV) and recording is executed. Further, rotation driving control of the disk is selected according to factors other than the type of the disk, such as according to whether random recording is allowed or not, according to a recording state in the disk, according to whether an alternative area is provided or not, according to a recording start position, or according to whether initialization is required or not. CLV control or CAV control is appropriately selected for a disk at recording to suppress a reduction in accessibility and a reduction in data transmission rate.

Abstract: On an information recording medium, an entire stream including a plurality of portion streams, each of which is provided with content information including still picture information, is multiplexed-and-recorded by a unit of packet. The information recording medium is provided with a file for storing object data, which is provided with a plurality of packets, each of which stores therein a piece of the content information. The information recording medium is further provided with a file for storing information which defines a reproduction sequence of the object data. The object data includes packets, each packet storing therein a piece of respective one of still picture information sets, the still picture information set including still picture information and control information thereof. A display control to the still picture information included in one still picture information set is described by the control information included in another still picture information set.

Abstract: An optical disk drive for recording data in accordance with a recording strategy determines a recording strategy of an unknown optical disk through comparatively-simple processing. When a loaded optical disk is an unknown disk, a control section reads a recommended recording strategy from a predetermined area on the loaded optical disk and reads correction parameters corresponding to the loaded optical disk from memory. The control section makes a correction to the read, recommended recording strategy in accordance with the correction parameters, and converts a recording pattern into a recording pulse in accordance with the corrected, recommended recording strategy. After conversion of the recording pattern into the recording pulse, the control section performs OPC and subsequently commences recording of actual data.

Abstract: An optical disc apparatus includes a pickup unit, a pickup control unit, a data reading circuit, a PLL control circuit, a CPU, a RAM, a ROM, an LED drive circuit, an LED display unit, and an interface circuit. The CPU functions as at least a CD/DVD determining unit, a type-of-disc determining unit, a thread motor drive unit, a focusing servo executing unit, an obtaining unit, a threshold calculating unit, a number-of-peaks calculating unit, and a checking unit.

Abstract: A recording-medium identification device has a light-emitting element for applying light on the recording medium and a detection element for detecting diffusely reflected light reflected in a backward direction, that is, a direction opposite to the direction in which the applied light is made incident, the diffusely reflected light being part of the applied light that is scattered and reflected on the recording medium.

Abstract: In a recording material, physical characteristic information of the recording medium, and more specifically, material information representing the material of the disc, is recorded. Accordingly, a recording apparatus and a reading apparatus easily and accurately determine the physical characteristics of the disc, thereby making it possible to provide suitable setting for performing an operation.

Abstract: An optical disk device includes a optical pickup head which emits a laser beam to an optical disk and detects light reflected therefrom, a signal output unit which outputs at least a servo signal and RF signal in accordance with the detected light, a gain control unit which determines the type of the optical disk from identification information recorded thereon, and sets first and second adjusted gains for a data recorded region and data unrecorded region, when determining that the optical disk is of a type wherein a light reflectance is higher in the data recorded region than in the unrecorded region, and a gain adjustment unit including a memory storing the first and second adjusted gains, the gain adjustment unit adjusting the gain of the servo signal in the data recorded region, using the first adjusted gain, and in the data unrecorded region, using the second adjusted gain.

Abstract: On a recording medium, the version information indicating a version of the recording standard to which the information recording medium is adapted is recorded. Moreover, the normal recording condition information for recording information at a normal recording speed and the high speed recording condition information for recording the information at a higher recording speed than the normal recording speed are recorded. The recording condition information includes, for example, information about a write strategy for driving a laser light source. At the time of recording, the information recording device compares the version information on the information recording medium with the version information of the information recording device so as to judge whether or not the information can be recorded.

Abstract: An optical disc recording and reproducing apparatus includes: an error occurrence deciding unit that decides whether or not a record error occurred during recording operation on an optical disc; an error information storing unit that stores record error information in a memory when the record error occurred; and an error information recording unit that reads out the record error information from the memory and records the record error information in a predetermined area on the optical disc when the recording operation is finished if a record error occurred during the recording operation.

Abstract: In a first reflected light amount comparing step and a first reflected light storing step, disc search is performed while moving a laser spot position from below to above an optical disc D, and a first reflected light amount which first becomes larger than or equal to a predetermined reflected light amount threshold is stored. Thereafter, in a second reflected light amount comparing step and a second reflected light storing step, disc search is performed while moving the laser spot position from above to below the optical disc D, and a second reflected light amount which first becomes larger than or equal to the predetermined reflected light amount threshold is stored. Thereafter, in a reflected light amount comparing step, the first and second reflected amounts are compared with each other. In a type determining step, it is determined whether or not the optical disc D is an SACD Hybrid, using the result of the comparison.

Abstract: A light-plasmon coupling lens including an optically transparent substrate having a light incident surface and a light-plasmon coupling surface opposite the light incident surface. The light-plasmon coupling surface including at least a set of circular concentric peaks/valleys which form a Fourier sinusoidal pattern in the radial direction of the circular concentric peaks/valleys. A conformal layer of metal is deposited on the light-plasmon coupling surface of the substrate and has aperture at the center of thereof through which plasmons are transmitted. An optical recording medium including a light-plasmon coupling lens.

Abstract: A method of reproducing an audio file includes: reading an extension information of the audio file, the extension information of the audio file being separated but associated with audio data of the audio file; establishing a reproducing mode for reproducing the audio file based on the extension information; obtaining at least a part of the audio file under the established reproducing mode; and determining whether the audio file is reproducible under the established reproducing mode by checking whether the part of the audio file constructs a specific format stream corresponding to the established reproducing mode.

Abstract: In a recording material, physical characteristic information of the recording medium, and more specifically, material information representing the material of the disc, is recorded. Accordingly, a recording apparatus and a reading apparatus easily and accurately determine the physical characteristics of the disc, thereby making it possible to provide suitable setting for performing an operation.

Abstract: A bandpass filter receives a tracking error signal. An average/minimum frequency measurement circuit repeats measurement prescribed times, of an average frequency and a minimum frequency of a signal output from the bandpass filter. A standard deviation calculation circuit assumes the average frequency and the minimum frequency obtained by prescribed times of measurement as one variate, and calculates a standard deviation of this variate. A determination circuit determines an optical disc to be reproduced as a read-only optical disc when the standard deviation is equal to or larger than a prescribed value, while it determines the optical disc to be reproduced as a recordable optical disc when the standard deviation is smaller than the prescribed value.

Abstract: A method of recording read/write compatibility information on an optical disc and a recording medium employing the method. Extended part version information, latest part version having recording capability, and latest part version having reproducing capability are stored in n.xy form on 6 bytes of a reserved zone of a physical format information zone of the optical disc. A recording/reproducing apparatus to record extended part version information on a reserved zone of a physical format information zone of a recording medium. The recording/reproducing apparatus has a base part version and a comparing unit to determine recording/reproducing compatibility with a recording medium having a detailed extended part version stored in a reserved zone of a physical format information zone.

Abstract: A method and device for determining the presence or absence of a disk and/or a disk size without using FG signals, are provided. The method includes placing a pickup at a first zone on the optical recording medium, the first zone located between an outer radius of a first recording medium type and an outer radius of a second recording medium type, where the outer radius of the second recording medium type is larger than the outer radius of the first recording medium type; detecting a reflected signal based on a returned beam from the first zone of the optical recording medium; and determining at least one of a size and an absence of the optical recording medium based on the detected reflected signal. Therefore, an FG sensor that is provided in a general disk device can be eliminated, thereby reducing the size and cost of a disk device.

Abstract: A method for identifying digital video disc (DVD) type identification is employed in a digital disc writing apparatus. Optical data is read from a DVD. Wobble signal amplitude and the maximum amplitude are calculated according to the read data. It is determined whether the difference between the wobble signal amplitude and the maximum amplitude exceeds a predetermined threshold. If so, the DVD is determined as a first type, otherwise, as a second type.

Abstract: A read out means reads out, from a multisession type optical disk which has been loaded, identification information which indicates its type, and a recommended write strategy pulse width. A calculation means, when a decision means has decided that the multisession type optical disk is of an unknown type, calculates a compensated pulse width based upon the value of the difference between the average value of the intrinsic write strategy pulse widths which are stored by a strategy storage means in correspondence with the identification information, and the recommended write strategy pulse width which has been read out by the read out means. And a recording means performs recording of data with laser light which has been modulated to the compensated pulse width as calculated by the calculation means.

Abstract: A method for identifying the size of an optical disc includes the steps of driving a motor at a specified rotary torque for rotating the optical disc, measuring angular acceleration of the optical disc, and comparing the measured angular acceleration with a reference angular acceleration to identify the size of the optical disc. A system that performs the method is also disclosed.

Abstract: An apparatus for impeding counterfeiting, impeding stealing and managing optical disk stock is described. The radio frequency identification (RFID) system is applied in an apparatus for impeding counterfeiting, impeding stealing, and managing optical disk stock. The apparatus has a disc, a RFID chip and an antenna. The disc has a first annular area, a second annular area and a third annular area. The second annular area is a data recording area with a metal recording layer. The first annular area and the third annular area both are areas without data. The RFID chip is embedded in the disc and the antenna connects to the RFID chip. The RFID chip and the antenna are located in the third annular area. The apparatus further has a foldable matching circuit to increase an inductance of the antenna and shorten the length of the antenna with even poles.

Abstract: A drive reads and/or writes data from/on an optical data storage medium, including first and second data storage layers stacked in this order toward the depth thereof, by radiating light through the surface. The drive includes a light source, a lens, a light detector, and a layer sensor. The light source emits the light. The lens produces a focal spot. The light detector includes at least one photodetector for receiving the light and generating a light quantity signal. The photodetector is used as a layer-sensing photodetector not receiving the light from the second data storage layer when the focal spot is located on the first data storage layer and receiving the light from the first data storage layer when the focal spot is located on the second data storage layer. The layer sensor determines, by the light quantity signal, where the focal spot is now located.

Abstract: An optical disc apparatus includes an optical pickup which irradiates a first laser beam for reproducing a first DVD medium, or a second laser beam for reproducing a second DVD medium onto a installed optical disc, and receives the reflected light from the installed optical disc, a controller determines that the installed optical disc is the second DVD medium when a value by normalizing the amplitude of a RF signal generated from the reflected light with a coefficient is larger than first threshold value and smaller than a second threshold value, and the controller determines that the installed optical disc is the first DVD medium when the value is not larger than first threshold value and smaller than a second threshold value.

Abstract: In an optical disc apparatus reading and writing data with respect to an optical disc, a motor controller uses widest pattern signals outputted from an optical pickup for judging size of an optical disc mounted on a turn table and stop of rotation of the optical disc. Since an inverse number of the widest pattern signal has correlation with a frequency sensed by a conventional frequency generator, the motor controller calculates a difference between inverse numbers of the widest pattern signals before and after putting braking force to the turn table, and judges the size of the optical disc with reference to variation of rotation speed before and after the braking. The motor controller further calculates a prediction time when the rotation of the optical disc will be stopped with using the variation of the inverse number of the widest pattern signal, stops to put the braking force to the turn table at the prediction time, and judges the rotation of the optical disc has been stopped.

Abstract: A method for recognizing at least two types of optical discs, which are associated with multiple different numerical apertures, includes the step of setting the numerical aperture of a focusing mechanism equal to a first one of the multiple different numerical apertures. The focusing mechanism is used to focus a light beam on a data storage layer of a given optical disc. The first numerical aperture is smaller than any of the other numerical apertures. The method further includes the step of recognizing the type of the given optical disc by the first numerical aperture that has been selected in the step of setting the numerical aperture.

Abstract: A control circuit for an optical disk drive includes a frequency detector, a phase detector, a low pass filter, a voltage-controlled oscillator (VCO), and a controller. The frequency detector and the phase detector both receive an eight-to-fourteen modulation (EFM) signal and a data phase-locked loop (DPLL) signal. The controller can calculate a target frequency and control the VCO to output the DPLL signal according to the target frequency. During a non-seek mode, the VCO outputs the DPLL signal according to output of the frequency detector, phase detector, and low pass filter. During a seek mode or when spindle speed of the optical disk drive changes, the VCO outputs the DPLL signal according to the target frequency. The controller further outputs charge pump currents for the frequency detector and the phase detector and sets an RF equalizer signal and a differential phase detector (DPD) equalizer signal according to the target frequency.

Abstract: An optical disc apparatus for recording, reproducing or erasing an information signal by converging a light flux onto a recording layer through a transparent substrate. The apparatus includes one or a plurality of optical heads having a plurality of objective lenses whose aberrations have respectively been corrected for a plurality of disc substrates of different thicknesses, a cartridge for enclosing the optical disc, a discrimination hole which is formed on the cartridge, and a sensor for detecting the opening/closing state of the discrimination hole and for generating a discrimination signal. In accordance with the result of the discrimination as to the thickness of the loaded optical disc, the objective lens, in which the occurrence of the aberration is smallest, is used, so that the information signal can preferably be recorded, reproduced or erased onto/from the optical discs having different substrate thicknesses.

Abstract: An optical disc apparatus for recording, reproducing or erasing an information signal by converging a light flux onto a recording layer through a transparent substrate. The apparatus includes one or a plurality of optical heads having a plurality of objective lenses whose aberrations have respectively been corrected for a plurality of disc substrates of different thicknesses, a cartridge for enclosing the optical disc, a discrimination hole which is formed on the cartridge, and a sensor for detecting the opening/closing state of the discrimination hole and for generating a discrimination signal. In accordance with the result of the discrimination as to the thickness of the loaded optical disc, the objective lens, in which the occurrence of the aberration is smallest, is used, so that the information signal can preferably be recorded, reproduced or erased onto/from the optical discs having different substrate thicknesses.

Abstract: A power control device for controlling a power of a light source of an optical beam directed to an optical medium. The power control device includes a reflected light detector for detecting reflected light from the optical medium when irradiated by an optical beam which is following a track; an arithmetic unit for calculating from the reflected light a transmissivity of light transmitted from a disk surface to a recording layer or an amount of directed light on the recording layer of the medium; and power control means for controlling the power of the light source for emission based on a calculation result produced by the arithmetic unit.

Abstract: An optical disc apparatus for recording, reproducing or erasing an information signal by converging a light flux onto a recording layer through a transparent substrate. The apparatus includes one or a plurality of optical heads having a plurality of objective lenses whose aberations have respectivley been corrected for a plurality of disc substrates of different thicknesses, a cartridge for enclosing the optical disc, a discrimination hole which is formed on the cartridge, and a sensor for detecting the opening/ closing state of the discrimination hole and for generating a discrimination signal. In accordance with the result of the discrimination as to the thickness of the loaded optical disc, the objective lens, in which the occurrence of the aberration is smallest, is used, so that the information signal can preferably be recorded, reproduced or erased onto/from the optical discs having different substrate thicknesses.

Abstract: An optical disc apparatus for recording, reproducing or erasing an information signal by converging a light flux onto a recording layer through a transparent substrate. The apparatus includes one or a plurality of optical heads having a plurality of objective lenses whose aberrations have respectively been corrected for a plurality of disc substrates of different thicknesses, a cartridge for enclosing the optical disc, a discrimination hole which is formed on the cartridge, and a sensor for detecting the opening/closing state of the discrimination hole and for generating a discrimination signal. In accordance with the result of the discrimination as to the thickness of the loaded optical disc, the objective lens, in which the occurrence of the aberration is smallest, is used, so that the information signal can preferably be recorded, reproduced or erased onto/from the optical discs having different substrate thicknesses.

Abstract: An optical disc apparatus for recording, reproducing or erasing an information signal by converging a light flux onto a recording layer through a transparent substrate. The apparatus includes one or a plurality of optical heads having a plurality of objective lenses whose aberrations have respectively been corrected for a plurality of disc substrates of different thicknesses, a cartridge for enclosing the optical disc, a discrimination hole which is formed on the cartridge, and a sensor for detecting the opening/closing state of the discrimination hole and for generating a discrimination signal. In accordance with the result of the discrimination as to the thickness of the loaded optical disc, the objective lens, in which the occurrence of the aberration is smallest, is used, so that the information signal can preferably be recorded, reproduced or erased onto/from the optical discs having different substrate thicknesses.