Abstract: An optical disc recording/reproducing apparatus includes: recording/reproducing means for recording/reproducing information by emitting a light beam onto a disc having a track which wobbles at a predetermined frequency; reflected light detection means for detecting the light beam reflected from the disc; wobble signal detection means for detecting a wobble amplitude signal which represents an amplitude of a signal generated from a component which is extracted from an output of the reflected light detection means and which wobbles at the predetermined frequency; and variation rate detection means for detecting dirt adhered on the disc based on a rate of a variation in the wobble amplitude signal, wherein the variation rate detection means detects the dirt based on the wobble amplitude signal before the recording/reproducing means records/reproduces the information.

Abstract: The sector synchronism of a timing generation section for generating data recording/reproducing timing is corrected at the address-mark detection timing of an address-mark detection section. Moreover, even if only one piece of address information having no error is not reproduced in the sector concerned, when at least one piece of address information having no error is reproduced in any of a predetermined number of sectors preceding the subject sector and at least one address mark is detected in the subject sector, the data recording/reproducing is permitted, and thus, the data is recorded/reproduced at a high speed and a high reliability even if an error rate of a physical address is deteriorated.

Abstract: A laser power control method according to the present invention is a method for controlling an output power of a laser 3 which is used for recording information on a recording medium 1. The method comprises steps of: detecting emitted light of the laser by a first detection section 4; obtaining a first driving current of the laser by a first control section 8 based on an output of the first detection section; detecting reflected light or transmitted light from the recording medium by a second detection section 5; and obtaining a second driving current of the laser by a second control section 12 based on an output of the second detection section. The laser is driven based on the first driving current or the second driving current while the first control section and the second control section are operated alternately such that the second control section does not operate when the first control section is operating, and the first control section does not operate when the second control section is operating.

Abstract: An optical disc apparatus reads the address information from an optical disc which has tracks and track spaces formed between tracks. The apparatus has an optical head which irradiates the disc with light and includes tracking detectors, divided into a first detector and a second detector in a track direction, detecting the light reflected from the disc and outputting detection signals, an adjusting circuit which adjusts amplitudes of the first and second detection signals and outputs the signals at a position where the address information is recorded, a differential amplifying circuit which outputs the differential signal which is the difference between the adjusted first and second detection signals, and an address detecting circuit which detects the address information based on the differential signal. As a result, the optical disc apparatus accurately detects whether information is being recorded on a correct track and improves the reliability during recording.

Abstract: An optical disc drive includes an optical head, a read signal processor, and a controller. The optical head outputs a first read signal representing light reflected from an optical disc and detected at a photodetector. The read signal processor receives the first read signal and outputs the second read signal responsive to a first or second control signal. The second read signal has a predetermined level when output responsive to the first control signal but a level corresponding to that of the first read signal when output responsive to the second control signal. The controller outputs the first and second control signals during first and second periods, respectively. The first period begins before marks are formed on the disc and ends while the marks are formed, and the second period follows the first period. The optical disc drive controls the data write operation in accordance with the second read signal.

Abstract: An optical disk drive reads and/or writes data from/on an optical disk on which a pre-pit has been formed on at least one side edge of a data recording track. The disk drive includes light-emitting element, photodetector section, subtractor and amplifier. The light-emitting element emits a light beam and irradiates the track with the light beam. The photodetector section receives and detects the light beam reflected from the track, thereby generating first and second detection signals, carrying information about shapes of the track at the one and the other side edges thereof, respectively, based on the reflected light beam. The subtractor generates a differential signal representing a difference between the first and second detection signals. The amplifier amplifies the differential signal, output from the subtractor, by a variable amplification factor. The optical disk drive detects the pre-pit in accordance with the amplified differential signal.

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 recording/reproducing apparatus includes: recording/reproducing means for recording/reproducing information by emitting a light beam onto a disc having a track which wobbles at a predetermined frequency; reflected light detection means for detecting the light beam reflected from the disc; wobble signal detection means for detecting a wobble amplitude signal which represents an amplitude of a signal generated from a component which is extracted from an output of the reflected light detection means and which wobbles at the predetermined frequency; and variation rate detection means for detecting dirt adhered on the disc based on a rate of a variation in the wobble amplitude signal, wherein the variation rate detection means detects the dirt based on the wobble amplitude signal before the recording/reproducing means records/reproduces the information.

Abstract: An optical disk drive reads and/or writes data from/on an optical disk on which a pre-pit has been formed on at least one side edge of a data recording track. The disk drive includes light-emitting element, photodetector section, subtractor and amplifier. The light-emitting element emits a light beam and irradiates the track with the light beam. The photodetector section receives and detects the light beam reflected from the track, thereby generating first and second detection signals, carrying information about shapes of the track at the one and the other side edges thereof, respectively, based on the reflected light beam. The subtractor generates a differential signal representing a difference between the first and second detection signals. The amplifier amplifies the differential signal, output from the subtractor, by a variable amplification factor. The optical disk drive detects the pre-pit in accordance with the amplified differential signal.

Abstract: An apparatus operates for recording and reproducing information on and from a recording medium formed with a track and pre-pits. The track has a wobble. The pre-pits are in a predetermined phase relation with the wobble of the track. The apparatus includes a pickup for reproducing a signal from the recording medium. A limiter operates for limiting an amplitude of the signal reproduced by the pickup in response to a limiting level, and thereby processing the signal reproduced by the pickup into a limiting-resultant signal. A filter operates for suppressing components of the limiting-resultant signal, and thereby processing the limiting-resultant signal into a filtering-resultant signal. The components have specified frequencies, and are caused by the pre-pits. The limiting level for the limiter is generated in response to the filtering-resultant signal. A signal caused by the wobble of the groove is extracted from the filtering-resultant signal.

Abstract: To accurately detect whether the information is being recorded on a correct track and improve the reliability during recording. The invention relates to an optical disc apparatus for reading the address information from an optical disc which has tracks and track spaces formed between tracks. The apparatus comprises an optical head which irradiates the disc with light and includes tracking detectors, divided into a first detector and a second detector in a track direction, detecting the reflecting light from the disc and outputting detection signals, an adjusting circuit which adjusts amplitudes of the first and second detection signals and outputting the signals at a position where the address information is recorded, a differential amplifying circuit which outputs the differential signal which is the difference between the first and the second detection signals adjusted, and an address detecting circuit which detects the address information based on the differential signal.

Abstract: An apparatus operates for recording and reproducing information on and from a recording medium formed with a track and pre-pits. The track has a wobble. The pre-pits are in a predetermined phase relation with the wobble of the track. The apparatus includes a pickup for reproducing a signal from the recording medium. A limiter operates for limiting an amplitude of the signal reproduced by the pickup in response to a limiting level, and thereby processing the signal reproduced by the pickup into a limiting-resultant signal. A filter operates for suppressing components of the limiting-resultant signal, and thereby processing the limiting-resultant signal into a filtering-resultant signal. The components have specified frequencies, and are caused by the pre-pits. The limiting level for the limiter is generated in response to the filtering-resultant signal. A signal caused by the wobble of the groove is extracted from the filtering-resultant signal.

Abstract: A regenerated signal process circuit of an optical disk device is developed to solve the problem that a jitter margin is lowered without an optimum regeneration condition because, when data is regenerated independent of a transfer rate, a data frequency fluctuates against a set value of an AGC, a waveform equalization circuit, a binarization circuit, or the like. In a signal process circuit, a set value of the AGC (104), the waveform equalization circuit (105), the binarization circuit (106), or the like is controlled by referring to the amount of oscillation control current of the VCO (1002) of a frequency synthesizer. The characteristics of the VCO of the data PLL (1001) is set equal to the characteristics of the VCO (1002) of the frequency synthesizer, and each set value is controlled by referring to the oscillation control current of each VCO. Then, the reference current is switched depending on the synchronization state of the data PLL (1001).

Abstract: An optical disk device of the present invention performs at least one of recording and reproduction of an optical disk in which a wobble signal is included along a data-recording track, by rotating the optical disk and by scanning the track on the optical disk using an optical head. The device includes: an extraction section for extracting the wobble signal of the optical disk from an output of the optical head; a synchronization clock generation section for generating a synchronization clock signal based on the wobble signal extracted by the extraction section; and a recording/reproduction section for performing at least one of recording and reproduction of data to/from the optical disk by the synchronization clock signal generated by the synchronization clock generation section.

Abstract: The data recording/reproducing device according to the present invention, in response to the detected signal output from the data error detector, repeats a reading operation to form a data from a reproduced signal. The gate signal generator includes an envelope detector and a comparator. The envelope detector has a time constant which is changed in accordance with the detected signal output from the data error detector, and forms a threshold signal that generally follows a level variation of the reproduced signal in accordance with the time constant. The comparator compares the reproduced signal and the threshold signal output from the envelope detector so as to form the gate signal.

Abstract: An optical information recording and reproducing apparatus comprising: a reproduction signal processing circuit including one or more elements which have respective variable parameters for changing states of the elements, respectively at the time of read-out of data from a recording medium such that the data is read out from the recording medium by changing the states of the elements.

Abstract: A clock changeover apparatus including a reference frequency divider for dividing a reference clock by a first frequency division number; a comparative frequency divider for dividing by a second frequency division number an output clock obtained by the clock changeover apparatus; a phase comparator for comparing phase of a signal of the reference frequency divider with that of the comparative frequency divider; a clock controller for changing the output clock so as to make the phase of the signal of the reference frequency divider coincident with that of the comparative frequency divider; a clock determining member which gives an initial value of the output clock to the clock controller and is capable of selecting the initial value of the output clock arbitrarily; a changeover member for effecting changeover between the first and second frequency division numbers; and a phase lock detector for monitoring whether or not the phase of the signal of the reference frequency divider coincides with that of the compa

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: The sector synchronism of a timing generation section for generating data recording/reproducing timing is corrected at the address-mark detection timing of an address-mark detection section. Moreover, even if only one piece of address information having no error is not reproduced in the sector concerned, when at least one piece of address information having no error is reproduced in any of a predetermined number of sectors preceding the subject sector and at least one address mark is detected in the subject sector, the data recording/reproducing is permitted, and thus, the data is recorded/reproduced at a high speed and a high reliability even if an error rate of a physical address is deteriorated.