Abstract: An optical disc device includes: an optical pickup including a first laser light source that emits laser light, an objective lens that focuses the laser light emitted from the first laser light source onto an optical disc, and a light receiving element that receives reflected light from the optical disc, and performs photoelectric conversion on the reflected light received to output a received-light signal; an FS signal generator that generates an FS signal indicating the light amount of the reflected light from the optical disc, based on the received-light signal from the light receiving element; and a dirt determiner that determines that dirt is present in the optical pickup, when the peak level of the FS signal is less than a dirt determination threshold, and controls the light receiving element to increase the peak level of the received-light signal from the light receiving element.

Abstract: An optical disc drive device includes a spindle motor that rotates an optical disc, an OPU, a first controller that causes the spindle motor and the OPU to read recorded data from the rotating optical disc, and an transmitter that transmits the read recorded data to a signal processing device disposed external to the optical disc drive device. The recorded data transmitted by transmitter is stored in a buffer provided in the signal processing device. The first controller decreases the rotational speed of the optical disc based on free space information indicating the free space of the buffer.

Abstract: An optical disc drive device includes a spindle motor that rotates an optical disc, an OPU, a first controller that causes the spindle motor and the OPU to read recorded data from the rotating optical disc, and an transmitter that transmits the read recorded data to a signal processing device disposed external to the optical disc drive device. The recorded data transmitted by transmitter is stored in a buffer provided in the signal processing device. The first controller decreases the rotational speed of the optical disc based on free space information indicating the free space of the buffer.

Abstract: After a playback RF signal 3 detected from an optical disc medium 1 is waveform-shaped, it is converted into a digital RF signal 6 with a sampling clock 8 having a cycle twice as long as a channel clock. Thereafter, a first offset correction circuit 9 corrects an offset fluctuation in a high frequency band, and a digital adaptive equalizer 23 performs adaptive equalization, and then a second offset correction circuit 27 corrects an offset component that remains after the offset correction by the first offset correction circuit 9, thereby demodulating a digital binary signal 37. Therefore, even when high-speed playback is carried out and an asymmetry depending on the recording quality is large, a reduction in power consumption can be realized while maintaining high-performance playback. Consequently, it is possible to provide an optical disc playback apparatus which can realize sufficient playback performance at low power consumption.

Abstract: An optical disc recording/playback apparatus is provided with a first AD converter 35 for shaping a push-pull signal 14 detected from an optical disc medium 1 by a light difference signal shaping circuit 21, and converting the signal into a digital sampling signal 38 using a sampling clock 37 synchronized with a channel frequency; a series of means for detecting wobble amplitude information 77 during recording from the digital sampling signal 38; a series of means for detecting address polarity information 60 and address position information during playback; and a recording laser power control circuit 113 for controlling a recording laser power to a power suited for recording on the basis of the wobble amplitude information.

Abstract: An optical disk device is provided with a first analog-to-digital converter for converting a push-pull signal detected from an optical disc medium into a digital sampling signal according to a sampling clock in the vicinity of a channel frequency. The optical disk device also includes an address polarity information detection circuit for detecting address polarity information from the digital sampling signal, and an address position information detection circuit for detecting address position information from the digital sampling signal while maintaining continuity.

Abstract: In a jitter detection apparatus, a playback RF signal 3 detected from an optical disc medium 1 is subjected to waveform shaping, and thereafter, converted into a digital RF signal 6 with a sampling clock having a cycle twice as long as a cycle of a channel clock. Thereafter, an offset variation in a high-frequency band is corrected by an offset correction circuit 9, and data that are missing in the time direction are restored by a Nyquist interpolation filter 23. Then, positions where jitter is to be extracted are selected from an output signal of the Nyquist interpolation filter 23, by a jitter detection preprocessing circuit 28, according to the playback speed of the optical disc medium 1 and the arithmetic capacity of a digital signal operation circuit 29, whereby highly accurate jitters can be extracted by using the digital signal operation circuit 29.

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 provides a process for producing an ?,?-bis(hydroxymethyl)alkanal represented by Formula (II): (wherein R represents an alkyl group, a cycloalkyl group, or an aryl group) which comprises reacting an aldehyde represented by Formula (I): R—CH2—CHO ??(I) (wherein R has the same meaning as defined above) with formaldehyde in the presence of a basic catalyst and a phase-transfer catalyst.

Abstract: An optical disk drive and recording power determination method determine the optimum power with consideration for the recording state of a base layer track when determining the optimum power by test recording before recording user data. After recording at a second recording power that is higher than a first recording power by a specific amount, recording is performed at a third recording power that is lower than the first recording power by a specific amount, and the first recording power is set to the recording power for data recording when a specified playback signal quality is achieved.

Abstract: An optical disk storing write-once information usable for protecting the copyright of the software by preventing the duplication, unauthorized use, etc., of the software. In the optical disk, a recording layer (213) is formed on a disk substrate (211) with a dielectric layer (212) inbetween. Then, an intermediate dielectric layer (214) and a reflecting layer (215) are successively laminated upon the recording layer (213), and an overcoat layer (216) is formed on the surface of the reflecting layer (215). A plurality of BCA (one of write-once identification information systems) sections (220a and 220b) are recorded by lowering the vertical magnetic anisotropy of the recording layer (213). At the time of reproduction, the write-once information is detected from differential signals.

Abstract: The present invention provides a process for producing an ?,?-bis(hydroxymethyl)alkanal represented by Formula (II): (wherein R represents an alkyl group, a cycloalkyl group, or an aryl group) which comprises reacting an aldehyde represented by Formula (I): R—CH2—CHO??(I) (wherein R has the same meaning as defined above) with formaldehyde in the presence of a basic catalyst and a phase-transfer catalyst.

Abstract: The present invention provides a signal processing device for optical discs that is capable of more accurately check signal quality at a higher speed than the conventional technique, even if a playback RF signal is deteriorated. A short recording mark detecting unit 115 detects short recording marks in an RF signal read from an optical disc 101, the short recording mark counting unit 116 counts a first short recording mark number as the number of the detected short recording marks, an error number counting unit 110 counts errors in the RF signal, an error number converting unit 111 converts the number of the errors to a second short recording mark number equivalent to the number of the errors, and a signal quality judging unit 112 judges recording quality based on a total of the first and second short recording mark numbers.

Abstract: A tilt control apparatus includes an orthogonal shift detector (9) which detects an orthogonal shift by comparing a pair of a plurality of tap coefficients (C1, . . . , C7) of a FIR filter and generates an orthogonal shift signal, and an actuator varies the inclination of the optical axis of the light beam to correct the orthogonal shift, and a tilt controller (10) controls the drive of the actuator in accordance with the orhogonal shift signal to minimize the orthogonal shift. In the information recording operation, the orthogonal shift obtained based on a recording track is previously stored in a temporary storage portion and the stored orthogonal shift is used to conduct the tilt control.

Abstract: After a playback RF signal 3 detected from an optical disc medium 1 is waveform-shaped, it is converted into a digital RF signal 6 with a sampling clock 8 having a cycle twice as long as a channel clock. Thereafter, a first offset correction circuit 9 corrects an offset fluctuation in a high frequency band, and a digital adaptive equalizer 23 performs adaptive equalization, and then a second offset correction circuit 27 corrects an offset component that remains after the offset correction by the first offset correction circuit 9, thereby demodulating a digital binary signal 37. Therefore, even when high-speed playback is carried out and an asymmetry depending on the recording quality is large, a reduction in power consumption can be realized while maintaining high-performance playback. Consequently, it is possible to provide an optical disc playback apparatus which can realize sufficient playback performance at low power consumption.

Abstract: In a jitter detection apparatus, a playback RF signal 3 detected from an optical disc medium 1 is subjected to waveform shaping, and thereafter, converted into a digital RF signal 6 with a sampling clock having a cycle twice as long as a cycle of a channel clock. Thereafter, an offset variation in a high-frequency band is corrected by an offset correction circuit 9, and data which are missing in the time direction are restored by a Nyquist interpolation filter 23. Then, positions where jitter is to be extracted are selected from an output signal of the Nyquist interpolation filter 23, by a jitter detection preprocessing circuit 28, according to the playback speed of the optical disc medium 1 and the arithmetic capacity of a digital signal operation circuit 29, whereby highly accurate jitters can be extracted by using the digital signal operation circuit 29.

Abstract: A recording/producing device for writing data on a recording medium, or reading data from the recording medium, wherein data matching a recording pattern so specified as to include a plurality of mutually different sets of mark lengths and space lengths is written on the recording medium, and the data is then read to generate data signals. An edge shift detector uses data signals to measure the edge shift amount of a mark formed on a recording medium for each set of a mark length and a space length. A record controller sets a recording parameter for each set of a mark length and a space length based on the measured edge shift amount.

Abstract: An optical disc recording/playback apparatus is provided with a first AD converter 35 for shaping a push-pull signal 14 detected from an optical disc medium 1 by a light difference signal shaping circuit 21, and converting the signal into a digital sampling signal 38 using a sampling clock 37 synchronized with a channel frequency; a series of means for detecting wobble amplitude information 77 during recording from the digital sampling signal 38; a series of means for detecting address polarity information 60 and address position information during playback; and a recording laser power control circuit 113 for controlling a recording laser power to a power suited for recording on the basis of the wobble amplitude information.

Abstract: Hold registers receive a hold register enable signal. When reading one kind signal of header field data, the hold register enable signal is High and the registers store newly renewed values of filter coefficients, and when reading a different kind signal of recording field data, the hold register enable signal is Low and the hold registers hold the last stored header field contents of the registers. Then, when a header field of a next sector is detected, the contents held in the hold registers are taken and preset to the registers. Thus, even in a case where an intermittent reproduction signal having different kinds of formats is processed in playback, the continuous adaptive equalization can be realized over the different kinds of reproduction signals in quality.

Abstract: An optical disc drive usable with discs to which data is continuously recorded and discs having a sector format can quickly resume playback signal output after passing imperfection causing potential reading errors, and plays disc with few read errors. A detection signal generator detects DC level fluctuation in the playback signal read from the disc and generates a detection signal tracking the DC level fluctuation. A selector selects a detection signal or a null signal without valid polarity based on the detection signal generated by the detection signal generator and input to the selector. A clamping unit performs a clamping process to suppress DC level fluctuation in the playback signal based on the detection signal when the selection unit selects the detection signal, and does not perform the clamping process when the selection unit selects the null signal. A signal processor performs specific signal processes based on clamping unit output.