Abstract: The present invention provides a semiconductor integrated circuit that is provided with an address generation circuit that selectively generates an address of a memory cell substituted by a redundancy memory cell based on a defective memory cell address retained in an address retention circuit, and a control circuit that selectively tests the redundancy memory cell by performing a retest on whether the substitution is successful or not based on the address generated by the address generation circuit.

Abstract: A memory component comprises a plurality of bit lines, on which memory cells are arranged, and a plurality of sense amplifiers, which are arranged in a row, each sense amplifier being connected to two bit lines. A bit line which is connected to a first sense amplifier in the row is arranged directly adjacent to a bit line which is connected to a second sense amplifier in the same row.

Abstract: A semiconductor memory device including a memory cell array which has a plurality of memory cells arranged in a matrix form, a plurality of bit line pairs which transfer data among the memory cells, a sense amplifier bank which includes a plurality of sense amplifiers, the plurality of sense amplifiers including a plurality of sense amplifier circuits, and the plurality of sense amplifier circuits being connected respectively to the plurality of bit line pairs to amplify data transferred to the bit line pairs, a plurality of word lines connected to the memory cells, a plurality of wirings disposed respectively corresponding to the plurality of word lines and above the plurality of word lines, and a plurality of stitch portions which connect the plurality of word lines to the plurality of wirings every predetermined intervals.

Abstract: A Magnetic Random Access Memory (MRAM), in which very little current flows through MTJ elements and very little voltage is applied across them, the MRAM being provided with sense-amplifiers capable of amplifying the potential difference between their corresponding pairs of bit lines at high speed. This is accomplished by a sense amplifier including CMOS inverters cross-connected or connected in loop, a P-channel MOS transistor for shutting the power off during standby, and N-channel MOS transistors for initializing the output of the sense amplifier during standby. A ground terminal of the inverter is connected to a bit line through a transistor of a bit switch, and a ground terminal of the inverter is connected to a bit line through a transistor of a bit switch.

Abstract: There is provided a high-density mask ROM operable at a high speed. With the mask ROM, respective source lines are disposed so as to be shared by memory cells in respective columns adjacent to each other, and bit lines are disposed so as to correspond to the respective columns of the memory cells. Further, the dummy cells are disposed for the respective columns of the memory cells. The dummy cells are each made up of a series-circuit including a first switching transistor that is turned into the conducting state in response to a signal potential on a dummy word line (DWL), and a second switching transistor 17 for coupling an adjacent source line to the bit line corresponding thereto in response to a potential of the source line in a column corresponding thereto. The memory cells each are made up of one unit of a transistor and a data storage formed by mask wiring.

Abstract: A wake-up circuit of a memory device employs a cascade chain structure in which bit lines are divided into a plurality of blocks, and if the bit lines of one of the blocks are determined to have undergone a wake-up operation based on a bit line voltage fed back in the block, the wake-up operation is performed on a subsequent block. Accordingly, a wake-up delay can be varied, and therefore peak currents can be controlled, thereby reducing overall system power noise.

Abstract: A semiconductor flash memory includes an erase/write control unit that, when performing an erase/write operation of read memory cells, reads and senses memory current of the read memory cells for each memory cell, and adjusts threshold voltage of each of the read memory cells to a predetermined value, and a readout control unit that, when performing a read operation, selects at least two read memory cells simultaneously from among the read memory cells to which the erase/write control unit stored the same data, and senses total memory current for the at least two read memory cells.

Abstract: A multiport memory in one embodiment of the invention includes a memory cell array, where each column in the array has two exterior complementary bitline pairs and zero, one, or more interior complementary bitline pairs. Across each pair of adjacent columns in the array, the adjacent exterior bitline pairs are associated with the same port in the multiport memory. In addition, within each column, the two exterior bitline pairs have the same, non-zero number of crossovers, and, across each pair of adjacent columns, the exterior bitline pairs have different numbers of crossovers. Furthermore, each column has at least one reference signal line located between the two exterior bitline pairs.

Abstract: A semiconductor memory device has a command decoder responsive to a plurality of commands to set the semiconductor memory device to a normal mode, for generating control signals corresponding to the commands, respectively, and a row address prelatch circuit for holding a row address except for a bank address input together with a precharge command, and outputting the row address to a row address latch circuit, when the semiconductor memory device is in a test mode. The row address latch circuit holds the row address output from the row address prelatch circuit in synchronism with a control signal which is generated when an active command is input. The column address latch circuit holds the column address which has already been input when the active command is input, in synchronism with a control signal which is generated when either a read command or a write command is input.

Abstract: A memory device includes a plurality of blocks, with each block having a respective array of memory cells and respective local word lines. The memory device also includes a respective switching device coupled between each local word line and a common voltage node. A global word line driver controls the respective switching devices to turn on for respective local word lines in a row across the blocks including an accessed memory cell. Thus, the common voltage node is in the current path of the accessed memory cell with minimized layout area and resistance of the current path.

Abstract: A memory unit includes width decoding logic enabling data to be accessed in a memory array at different data widths. To improve memory access speed, the memory unit also includes dedicated read output paths for accessing data at the full data width of the memory array. The dedicated read output paths bypass the width decoding logic and provide data from the memory array directly to a data bus, thereby providing improved memory performance when width decoding is not needed. The memory unit can be incorporated in programmable devices and a programmable device configuration can select either the read bypass paths or the width decoding logic. Hardware applications that require width decoding and improved memory access speed can utilize additional programmable device resources outside the memory unit to register the full width data from the memory unit and convert it to a different data width.

Abstract: Semiconductor memory modules and semiconductor memory systems using the same are described herein. The modules divide a conventional DIMM into a series of separate, smaller memory modules. Each memory module includes at least one semiconductor memory chip arranged on a substrate; CAwD signal input lines arranged on the substrate in a first predetermined line number and connecting one of the semiconductor memory chips to CAwD input signal pins on the substrate; and rD signal output lines arranged on the substrate in a second predetermined line number and connecting the one or a last semiconductor memory to a second number of rD output signal pins of the substrate. In a semiconductor memory system including the semiconductor memory modules, each memory module is separately connected to a memory controller by the CAwD signal input lines and the rD signal output lines in a respective point-to-point fashion.

Abstract: A longitudinally segmented acoustic transducer for a cement bond logging (CBL) tool having a plurality of adjoining PZT ring-like segments driven synchronously in parallel by one or more pulses and caused to vibrate in an anti-resonant mode, substantially below the resonant frequency of an individual segment when used in a transmitting application. When used in a receiving application, each of the plurality of transducer rings are caused to vibrate by acoustic signals detected by the transducer array, also in an anti-resonant mode. High speed digital signal processing enables on-depth, high quality data for all azimuths at each depth to be obtained, processed, normalized and either sent to the surface in real time for each 20 Hz firing cycle, as the CBL tool is pulled toward the surface, or stored in a memory module in digital form for later retrieval. Built-in calibration factors used for normalizing the output signals to the operating conditions of use may be accessed at any time.

Abstract: A method for improving the seismic resolution in the field of petroleum exploration and development, using the steps of: (1) ensuring the depth and the velocity of the low-velocity layer and the high-velocity layer and the characteristic of the frequency spectrum of the seismic wave at the near-surface using the borehole seismic survey; (2) separating the ghost wave from the seismic record in the high-velocity layer using the processing method of the vertical seismic profiling, and improving the SNR of the seismic record of the direct wave at the high-velocity layer using the uphole stacking of the vertical seismic profiling; (3) evaluating the de-convolution operator of the near-surface by the convolution math-physics equation; (4) evaluating the seismic record with high resolution by the de-convolution math-physics equation; (5) providing the band-pass filtering and geologic interpretation to the seismic record with high resolution.

Abstract: In the oil industry, the acoustic sounding method is a well-known technique for taking the depth measurements of particular attributes of an oil well or borehole. The method involves sending a short, sharp, clear, loud bang sound down a borehole, normally between the inside wall of the borehole casing, commonly referred to as the annulus and the outside of the production tubing string, and recording the echoes generated. One device for generating the sound needed in the acoustic sounding method is an air or gas pressurized chamber which is discharged at or near the wellhead of the borehole. The sound being generated by this device, commonly known as an acoustic generator, comes from the energy released by the equilibration of the different gas pressures. The current invention is an acoustic generator with an improved microphone and microphone unit design for more efficient and effective echo detection.

Abstract: The portable electronic device, preferably a wristwatch, includes a radiofrequency signal receiver for receiving, in particular, GPS signals via an antenna, a magnetic compass, a microprocessor data processing unit for processing data provided by the receiver and the compass, and storage means in which almanac and ephemeredes data relating to satellites is stored. The compass is arranged for provide an orientation signal to the data processing device. In this manner, the unit can control means for indicating a direction to indicate a preferred orientation for searching for satellites visible to the user in a reading position of the watch. These indicating means can be formed by the time indicating hands moved above a watch dial. The preferred orientation is calculated by the processing unit on the basis of the almanac and ephemeredes data, time data and the orientation signal.

Abstract: The present invention concerns a water-resistant portable apparatus including a case in which there is mounted an electroacoustic transducer separated from an inlet cavity in a water-resistant manner by a deformable membrane. This inlet cavity is arranged in said case in direct communication with the exterior. The electroacoustic transducer and the inlet cavity are arranged collaterally such that at least one part of said transducer, respectively of the cavity, of a determined thickness is arranged in the same slice of the case and in that an acoustic channel connects the transducer to the membrane to transmit acoustic vibrations.

Abstract: A novel graphical organizational timing device is disclosed. The device indicates tasks or events to be completed within a pre-determined routine using customizable and/or changeable discs attached to a mechanical countdown timer. The device is primarily designed for use with children and adolescents but can be used within any setting in which tasks have to be performed in sequence in a pre-set time period.

Abstract: An optical disk that includes main information and write-once information recorded on the optical disk. The write-once information is recorded as information unique to the optical disk, and the write-once information stores at least watermark production parameters for producing a watermark.

Abstract: The present invention discloses a system and method to telephonically access information related with items printed on a physical document, simply by touching with a finger items marked on the physical document or on any other physical surface. The system includes a touch foil placed over (or under) the document, for reading the coordinates of selected marked items, a telephone set for receiving the coordinates of the items selected by the user and for dialing to an interactive voice response (IVR) service used for accessing and retrieving selected hyperlinked documents from the web through a documents proxy server, for converting retrieved documents to synthesized speech, and for providing to the user through the telephone network, the selected documents that have been converted into speech.

Abstract: An optical head device including a photo detector and an optical system which converges a laser beam emitted by a laser light source onto an optical recording medium and also guides a returning beam from the optical recording medium to the photo detector. The optical head device further includes a base on which the laser light and the photo detector are mounted. An optical element is mounted on the base via an optical element holder which has the same linear expansion coefficient as that of the base and is fixed with adhesive directly to the base. The optical element is fixed on a surface which is perpendicular to a device optical axis of the element holder.

Abstract: An actuator of an optical pick-up device includes two fixing frames, a lens holder disposed between the fixing frames and provided with a focusing lens, coils, and a reflection mirror having a central portion thinner than other portions where the coils are located, springs supporting the lens holder, the springs connecting two points of each fixing frame to the lens holder, each spring having one or more bends, a permanent magnet disposed facing the coils to generate magnetic field, and a yoke forming a path of the magnetic field generated by the permanent magnet.

Abstract: A method for determining a sub-beam add signal (SBAD) value is provided. At first, a jth read SBAD value is obtained at the jth read status. Next, the jth write SBAD value is determined according to the (j?1)th write SBAD gain at the jth write status. Then, the jth SBAD multiple is obtained according to the jth write SBAD value and the jth read SBAD value. Next, the (j?1)th write SBAD gain is changed into the jth write SBAD gain according to the jth SBAD multiple. At last, the level of the (j+1)th write SBAD value is adjusted according to the jth write SBAD gain at the (j+1)th write status.

Abstract: A method for detecting and controlling disc tilt in an optical disc mechanism comprising the steps of (A) measuring a 2-dimensional displacement of an optical lens of the optical disc mechanism, (B) extracting an absolute value of a disc tilt angle in the optical disc mechanism based upon the 2-dimensional displacement and (C) controlling deflection of a tilt moving coil according to the absolute value of the disc tilt angle.

Abstract: The method and apparatus described utilise the fact that CDs manufactured from the same master will have distinctive physical characteristics attributable to the physical manufacturing process of the master to distinguish counterfeit CDs from genuine discs. For a genuine disc, the relative angular orientation of specified sections of the recorded data are determined and recorded. The relative angular orientation of the same sections of data on a test disc are also determined. Where the relative angular orientations are the same it is concluded that the test disc derives from the same source as the genuine disc and is therefore bona fide. Where there is no correlation, the test disc may be identified as counterfeit. The relative angular orientations, or other physical characteristics of the discs, may be physically measured, or may be calculated from information gained by reading the data on the disc. The disclosed technique can also be used to copy protect discs.

Abstract: An information recording medium (100) is provided with: a user data area (108) for recording therein record data; a plurality of temporary defect management areas (104, 105) for temporarily recording therein defect management information (120) which is a basis of defect management for a defect in the data area; and a flag area (111) for recording therein distinction information for distinguishing a temporary defect management area in which the defect management information that is effective is recorded, from the plurality of temporary defect management areas, the distinction information being recorded as a type of a combination pattern of an area set to be in a recorded condition and an area left to be in an unrecorded condition according to a predetermined rule, in the flag area.

Abstract: In step S1, the address generator generates address information composed of a sync signal which is recorded on an optical disc, address data and an error correction code for the address data, pre-encodes and supplies it to a modulator. At the same time, a carrier signal generator generates a carrier signal which is to carry the address information, and supplies it to the modulator. In step S2, the modulator makes MSK modulation of the carrier signal supplied from the carrier signal generator on the basis of the pre-encoded address information supplied from the address generator, and supplies a resultant MSK modulation signal to a wobbling unit. In step S3, the wobbling unit forms, on the optical disc, a spiral groove wobbled adaptively to the MSK modulation signal supplied from the modulator. In this optical disc, a given address can be accessed quickly and accurately.

Abstract: In a PLL circuit, a phase error of a reproduced signal is extracted in either a way based on a zero-cross timing or a way based on a self-running timing. A decision is made as to whether the reproduced signal is in a continuous-wave interval where an inversion period of the reproduced signal remains constant or in a random-wave interval where the inversion period of the reproduced signal varies at random. When the reproduced signal is in a continuous-wave interval, a phase error is extracted on the self-running-timing basis. When the reproduced signal is in a random-wave interval, a phase error is extracted on the zero-cross-timing basis. A continuous-wave interval may be replaced by a specified-pattern repetition interval where the inversion period of the reproduced signal changes in accordance with a repetition of a specified pattern.

Abstract: A method for controlling an optical power level includes the steps of a) regularly increasing a control value of a driving signal generator for driving a pickup unit adapted to output an optical power, b) checking a driving signal of the driving signal generator according to the increasing control value, and c) setting a control value at which the driving signal begin to be generated as an offset value for setting up an optical power. Therefore, an offset value for a reference optical power needed for setting up laser power levels for individual operation modes is more accurately calculated, and the laser power levels for individual operation modes are optimally controlled based on the offset value.

Abstract: An optical recording method is designed for recording data on a recordable optical disk by use of a laser beam of a present recording apparatus under a desired recording condition. The method detects identification information which is reserved in the optical disk and which is indicative of a type of a previous recording apparatus. The detected identification information is compared with a plurality of identification information which are previously stored in correspondence to various types of recording apparatuses. As results of the comparison, the method determines whether the detected identification information matches with one of the stored identification information which does not correspond to the type of the present recording apparatus. Upon the determining of matching, the method retrieves a recording condition which is previously stored in association with the matching identification information.

Abstract: A DVD-R recorder according to the invention detects an item of recording speed information (d15) from a DVD-R (30) on which histories of recording speed information, write strategy, and recording power condition are stored. When the decoded item of recording speed information (d15) agrees with a set item of recording speed information (d17), the recorder detects the write strategy (d6) and the recording power condition (d10) corresponding to the decoded item of recording speed information (d15). A recording-pulse-determination section (9) converts a recording pattern (d8) into a recording pulse (d9) according to the write strategy (d6). A recording-power-determination section (12) performs an OPC based on the recording power condition (d10). The recording power condition (d10) may include information specifying that a recording pulse corresponding to the front edge of a recorded mark has a larger recording power than other recording pulses.

Abstract: An information storage medium having a plurality of information storage layers, each of which includes an optimal power control (OPC) area for obtaining an optimal recording condition. Optimal power control areas in odd-numbered and even-numbered information storage layers viewed from a direction in which light is incident upon the information storage medium are disposed one on another to not directly face each other. An actually usable area of an optimal power control area in each of the information storage layers varies depending on use circumstances of each of the information storage layers. Therefore, when an OPC area of one information storage layer performs OPC, this OPC does not affect another information storage layer. Also, an area of each of the information storage layers can be efficiently used.

Abstract: The present invention allows the usability of a write-once recording medium to be enhanced. The write-once recording medium is provided with an ordinary recording/reproduction area, an alternate area, a first alternate-address management information area (DMA) and a second alternate-address management information area (TDMA). In addition, written/unwritten state indication information (a space bitmap) is also recorded. The second alternate-address management information area is an area allowing alternate-address management information recorded therein to be renewed by adding alternate-address management information thereto. In addition, the written/unwritten state indication information indicates whether or not data has been recorded in each data unit (cluster) on the recording medium. Thus, it is possible to correctly execute management of defects and properly implement renewal of data in the write-once recording medium.

Abstract: A disc having an updatable defect management area used by an apparatus for managing defects on the disc, the disc including a user data area which includes user data, a spare area that is a substitute area for a defect existing in the user data area, and an area in which are recorded an address of data that is last recorded in the user data area and an address of a replacement data recorded in the spare area. Accordingly, the disc defect management method and apparatus are applicable to a recordable disc such as a write-once disc while effectively using a defect management area of the disc.

Abstract: A calibration of a focus error signal gain in a focus servo system of an optical disk drive is presented. The focus error signal gain can be calibrated by oscillating an optical pick-up unit in a focus direction through a focus point and determining a focus sum threshold. The optical pick-up unit can then be oscillated around a focus control effort that results in a sum signal equal to the focus sum threshold and the peak-to-peak value of a focus error signal can be measured. The focus error signal gain can be determined from the peak-to-peak value of the focus error signal.

Abstract: The present invention provides a data recording device that can restrain the low-pass component in data to be written onto a recording medium without causing a problem in decoding the data using likelihood information. This data recording device includes: a data bit string combining unit that combines, by predetermined combining rules, a plurality of predetermined parity bit strings one by one with a data bit string obtained prior to a change to the bit order in a bit order rearranging procedure, thereby generating a plurality of composite data bit strings; and a data bit string selecting unit that selects one encoded data bit string from a plurality of encoded data bit strings generated through encoding procedures including the bit order rearranging procedure carried out for each of the plurality of composite data bit strings. Based on the selected encoded data bit string, the data recording device performs a data write operation onto the recording medium.

Abstract: A system and method are disclosed for providing a gain control signal for a multilevel read signal. In one embodiment, maximum automatic gain control marks are periodically inserted amongst a series of data fields. The automatic gain control marks include a series of high level marks such that the maximum signal detected in the interior portion of each maximum automatic gain control mark is not reduced by intersymbol interference. Minimum automatic gain control marks are also periodically inserted amongst a series of data fields. The automatic gain control marks include a series of high level marks such that the maximum signal detected in the interior portion of each minimum automatic gain control mark is not reduced by intersymbol interference. In another embodiment, multilevel signals are encoded to facilitate automatic gain control. The effect of a plurality of candidate merge symbols on the residual running total power associated with a current data block is determined.

Abstract: A method and apparatus extract information from a burst cutting area (BCA) of a recording medium. The BCA extraction includes (a) receiving a signal from the recording medium, the signal including BCA data read from the BCA, the BCA data being represented by channel symbols, (b) analog-to-digital (A/D) sampling the signal to generate input data, (c) identifying a BCA region within the input data, the BCA region corresponding to the BCA data, (d) determining an average channel symbol width of the BCA data, the average channel symbol width corresponding to an average number of A/D samples per channel symbol in the BCA data, (e) increasing a signal-to-noise ratio (SNR) of the BCA data using the average channel symbol width, (f) generating a channel pattern data from the BCA data using a selected threshold value, and (g) generating a channel symbol data from the channel pattern data using the average channel symbol width.

Abstract: An information recording medium includes a lead-in area and a data area for storing contents information. The lead-in area includes a first lead-in information area and a second lead-in information area. The first lead-in information area corresponds to a first playback mode. The second lead-in information area corresponds to a second playback mode different from the first playback mode. The first lead-in information area has a first depth and is designed for storing lead-in information related to the contents information stored in the data area. The second lead-in information area includes pre-pits having a second depth greater than the first depth. The pre-pits represent predetermined information, such as information of copyright protection, related to the contents information stored in the data area.

Abstract: An information recording medium includes a lead-in area and a data area for storing contents information. The lead-in area includes a first lead-in information area and a second lead-in information area. The first lead-in information area corresponds to a first playback mode. The second lead-in information area corresponds to a second playback mode different from the first playback mode. The first lead-in information area has a first depth and is designed for storing lead-in information related to the contents information stored in the data area. The second lead-in information area includes pre-pits having a second depth greater than the first depth. The pre-pits represent predetermined information, such as information of copyright protection, related to the contents information stored in the data area.

Abstract: A recording medium comprising a recording area, the recording area includes a first area and a second area, the first area includes a frame area, the frame area includes an area in which a second synchronization code sequence and at least a portion of data are to be recorded, and the second area includes an area in which a third synchronization code sequence and a fourth synchronization code sequence are to be recorded.

Abstract: An optical pickup device and an optical recording and reproducing apparatus are suitable for use with a near-field optical recording and reproducing system. An optical pickup device comprises an objective lens composed of a solid immersion lens (SIL) the objective lens having a numerical aperture greater than 1, a beam splitter configured to reflect both of a p-polarized light component and an s-polarized light component of reflected lights from an optical recording medium when the optical pickup device irradiates the optical recording medium with a bundle of rays in a predetermined polarized state from a light source through the objective lens, a divider configured to divide incident light into a p-polarized light component and an s-polarized light component reflected by the beam splitter, and a photo-detector configured to separately detect the p-polarized light component and the s-polarized light component divided by the divider.

Abstract: There is provided an objective lens used for a plurality of types of optical discs having a front surface and a rear surface, each of which includes an inner region and an outer region. The outer region has a surface shape which suppresses a coma caused when a beam used for a first optical disc is incident thereon obliquely with respect to an optical axis of the objective lens. The inner region is configured such that, at a boundary position between the inner region and the outer region, the coma caused when a beam used for a second optical disc is incident on the inner region obliquely at a first angle with respect to the optical axis is less than the coma caused when the beam used for the second optical disc is incident on the outer region obliquely at the first angle with respect to the optical axis. Further, an inclination ?2A of the inner region and an inclination ?2B of the outer region of the rear surface satisfy a condition: ?2.5<?2B??2A<0.0.

Abstract: A semiconductor laser device includes: a semiconductor laser chip which is composed of a semiconductor substrate and a plurality of semiconductor layers stacked on an element formation face of the semiconductor substrate and which outputs an irradiation light for irradiating an optical disk; and a light receiving element which receives the irradiation light reflected by the optical disk as a feedback light. The semiconductor laser chip includes on one face thereof an electrode facing an optical element and is fixed in a package so that at least one of sub-beams reflected by the optical disk is incident on the one face. A chip exposing portion for exposing a region of the one face where the sub-beam is incident is formed in the electrode.

Abstract: In an optical pickup apparatus which includes at least a laser light source and an object lens and can apply a laser beam to different types of optical discs, an aberration correction liquid crystal device is placed on the optical axis of the laser beam emitted from the laser light source. The aberration correction liquid crystal device includes a first electrode section being placed on the side of the laser light source and having a first electrode pattern for correcting aberration concerning a first optical disc, a second electrode section being placed on the side of the optical disc and having a second electrode pattern for correcting aberration concerning a second optical disc different from the first optical disc in type, and liquid crystal being sandwiched between the first and second electrode sections.

Abstract: An optical head device and an optical recording and reproducing apparatus using this optical head device, which can record information and reproduce the recorded information at any of optical recording media, such as a next generation optical recording medium, in which the wavelength of the light source is made to be shorter, the numerical aperture of the objective lens is made to be higher, and the thickness of the recording medium is made to be thinner, and conventional recording media of DVD and CD standards, are provided. A light having wavelength of 405 nm, emitted from one of optics, is inputted to an objective lens as a collimated light, and is focused on a disk having thickness of 0.1 mm. A light having wavelength of 650 nm, emitted from the other of optics, is inputted to the objective lens as a diverged light, and is focused on a disk having thickness of 0.6 nm.

Abstract: A laser driving apparatus for a light source of an optical head apparatus includes a laser, a laser driving circuit, and a radio frequency current generation circuit for generating a radio frequency current to be superimposed on the drive current. The laser driving apparatus further includes a current monitor circuit, an optical detector for detecting an optical output of the laser; a selection circuit for selecting either of non-superimposing or superimposing the radio frequency current on the drive current, an APC circuit for controlling the optical output of the laser at a constant level, and a control circuit. The control circuit controls the amplitude of the radio frequency current on the basis of current values of the drive current on non-superimposing and superimposing or detection values of the optical output of the laser on non-superimposing and superimposing.

Abstract: A data storage device comprises a media including a memory layer within which are formable domains associated with information, and a conductive layer disposed over the memory layer, the conductive layer having anisotropically increased electrical conductivity in a thickness direction. A conductive tip contactable with the conductive layer is adapted to form domains within the memory layer and one of the conductive tip and the media is movable to access the memory layer.

Abstract: A phase-change optical information recording medium in which information can be recorded, reproduced and rewritten and which includes a first transparent substrate having a wobbling guide groove which is spirally formed thereon at a pitch; a first dielectric layer located overlying the first transparent substrate and having an optical thickness of from 80 nm to 200 nm; a phase-change recording layer located overlying the first dielectric layer and having an optical thickness of from 20 to 50 nm when the recording layer is in an erased state; a second dielectric layer located overlying the recording layer and having an optical thickness of from 10 nm to 70 nm; a reflection layer located overlying the second dielectric layer; optionally a third dielectric layer located between the second dielectric layer and the reflection layer; and a second transparent substrate located overlying the reflection layer.

Abstract: An optical disc including one or more than one recording layers has land areas (131) and groove areas (132) as recording tracks, wherein a data recording area of at least one of the recording layers is divided into a plurality of zones in a radial direction. In each of the divided zones, one or more than one prepits (133) with predetermined data are disposed in a track so that each header area is disposed at ever other boundary among the boundaries between the land areas and the groove areas. Each header area is shifted in the circumferential direction from other header areas apart from the each header area by two boundaries without overlapping in the radial direction.