Abstract: A fan-equipped heatsink includes: a heat receiving substrate made of metal; a centrifugal fan disposed on an upper surface side of the heat receiving substrate; a plate-shaped wall that is made of metal, is provided so as to stand at a position, on the upper surface of the heat receiving substrate, which is around and opposed to an outer peripheral portion having an air discharge opening of the centrifugal fan, and are provided with a plurality of through-holes that are open in a plate surface opposed to the centrifugal fan; and a lid member fixed to an upper end of the plate-shaped wall 4 and configured to close a space on the inner side of the plate-shaped wall.

Abstract: A fan-equipped heatsink includes: a heat receiving substrate made of metal; a centrifugal fan disposed on an upper surface side of the heat receiving substrate; a plate-shaped wall that is made of metal, is provided so as to stand at a position, on the upper surface of the heat receiving substrate, which is around and opposed to an outer peripheral portion having an air discharge opening of the centrifugal fan, and are provided with a plurality of through-holes that are open in a plate surface opposed to the centrifugal fan; and a lid member fixed to an upper end of the plate-shaped wall 4 and configured to close a space on the inner side of the plate-shaped wall.

Abstract: A control unit is caused to drive a collimator lens from a position of an origin, by a clock number A of drive pulses of a pulse rate T1, thereby to move the collimator lens, and is caused to return the lens to the position of the origin at a pulse rate T2 higher than the pulse rate T1, and counts a clock number B of drive pulses required for returning the lens, and repeats the counting while raising the rate T2 stage by stage, until the clock numbers A and B do not become equal. When the clock numbers A and B are not equal, the control unit judges the occurrence of the step-out, and determines the rate T2 being one stage lower than the rate T2 at which the occurrence of the step-out has been judged, as the pulse rate of the operation of correction of spherical aberration.

Abstract: A control unit is caused to drive a collimator lens from a position of an origin, by a clock number A of drive pulses of a pulse rate T1, thereby to move the collimator lens, and is caused to return the lens to the position of the origin at a pulse rate T2 higher than the pulse rate T1, and counts a clock number B of drive pulses required for returning the lens, and repeats the counting while raising the rate T2 stage by stage, until the clock numbers A and B do not become equal. When the clock numbers A and B are not equal, the control unit judges the occurrence of the step-out, and determines the rate T2 being one stage lower than the rate T2 at which the occurrence of the step-out has been judged, as the pulse rate of the operation of correction of spherical aberration.

Abstract: A first photodiode for BD receives a laser light beam separated from a laser light beam emitted from a first semiconductor laser, detects laser power of the first semiconductor laser, and outputs an output current signal. A second photodiode for DVD/CD receives a laser light beam separated from a laser light beam emitted from a second semiconductor laser, detects laser power of the second semiconductor laser, and outputs an output current signal. An output terminal of the first photodiode and an output terminal of the second photodiode are connected to each other, and the output current signal and the output current signal are both inputted to the same input terminal of the first current-voltage conversion circuit.

Abstract: The optical miniaturized module includes a semiconductor laser for irradiating an optical disk with laser light, a diffraction grating for forming a main beam and two sub beams from the laser light, a polarization hologram for dividing reflected light from the optical disk, and a photodetector for detecting the reflected light. The polarization hologram includes a first parting line defined in a direction optically corresponding to a radial direction as the optical disk rotates. A main beam M incident area is divided with a boundary defined by the first parting line. A sub beam A incident area and a sub beam B incident area are each arranged avoiding the first parting line.

Abstract: A signal evaluation device for evaluating a decoded signal of maximum likelihood decoding includes: a differential metric circuit for finding differential metrics; comparators for judging whether a difference of differential metrics exceeds a predetermined threshold; counters for counting respective output pulses of the comparators; and a controller for finding the probability of the differential metrics falling at or below the predetermined threshold, based on the number of measured samples and the number of samples counted by the counters, and processing the probability by arithmetic operations so as to obtain an index of signal evaluation. With this arrangement, signal evaluation devices for evaluating a recording medium or a recording medium driving device can have a simpler structure and can perform evaluations in a plurality of PR modes.

Abstract: An optical disk using both grooves and lands as a recording track is provided with {circle around (1)} a data area for recording/reproducing data and {circle around (2)} DMAs (Data Management Areas) for managing a defective sector in the data area. The DMAs include four DMAs A–D all formed on the lands. The DMA B(D) is formed behind the ending sector of the DMA A(C). This arrangement realizes a DMA format having high resistance to defects and improving a processing rate. Consequently, highly reliable optical disk and optical disk apparatus can be provided.

Abstract: The optical miniaturized module includes a semiconductor laser for irradiating an optical disk with laser light, a diffraction grating for forming a main beam and two sub beams from the laser light, a polarization hologram for dividing reflected light from the optical disk, and a photodetector for detecting the reflected light. The polarization hologram includes a first parting line defined in a direction optically corresponding to a radial direction as the optical disk rotates. A main beam M incident area is divided with a boundary defined by the first parting line. A sub beam A incident area and a sub beam B incident area are each arranged avoiding the first parting line.

Abstract: A signal evaluation device for evaluating a decoded signal of maximum likelihood decoding includes: a differential metric circuit for finding differential metrics; comparators for judging whether a difference of differential metrics exceeds a predetermined threshold; counters for counting respective output pulses of the comparators; and a controller for finding the probability of the differential metrics falling at or below the predetermined threshold, based on the number of measured samples and the number of samples counted by the counters, and processing the probability by arithmetic operations so as to obtain an index of signal evaluation. With this arrangement, signal evaluation devices for evaluating a recording medium or a recording medium driving device can have a simpler structure and can perform evaluations in a plurality of PR modes.

Abstract: An optical disk device of a simple structure using an optical pickup alone as read mechanism for detecting a thickness of the substrate of an optical disk. The optical disk device (1) carries out the focus search by moving the focal point of a laser beam emitted through an objective lens in a direction along the thickness of the optical disk in a region covering both the substrate surface and the recording layer, (2) converts S-shaped wave forms produced in a focus error signal FES from a two-piece photo-diode when the focal point passes through the substrate surface and recording layer, respectively into a digital signal CP.sub.out, and (3) detects a pulse interval of the digital signal CP.sub.out, by means of an MPU. Since the MPU detects the number of pulses of the digital signal CP.sub.out, the optical disk device can also detect the number of the recording layers.

Abstract: A clock extracting section generates a first clock synchronized with a reproducing signal, and a second clock with a frequency twice a frequency of the first clock. An AD converter quantizes the reproducing signal at timing of the second clock. A data classifier classifies the quantized data into two quantized data streams with a period of the first clock. Each equalizer equalizes the two quantized data streams to (1,1) and (1,2,1) partial response characteristics. Each branch metric arithmetic unit calculates a corresponding branch metric respectively. A synthesizer calculates a sum of them so as to generate a synthetic branch metric. An ACS circuit and a data decoding section Viterbi-decode data according to the synthetic branch metric. As a result, even if an SN ratio is lowered by increase in interference between codes and a noises at the time of recording at high density, an error of decoded data can be decreased.

Abstract: An information reproducing apparatus has (1) a reference signal generating circuit for generating a first reference signal corresponding to reproduced signal of the main information; (2) a first switching circuit for selecting one of the reproduced signal and the first reference signal; and (3) a controller, which generates a selection instructing signal, for controlling such that the reproduced signal is selected during reproducing of the main information recorded area while the first reference signal is selected during reproducing of the main information unrecorded area. With the arrangement, when the main information unrecorded area is reproduced, the clock for carrying out the reproducing of main information is synchronized with the first reference signal which corresponds to the reproduced signal.

Abstract: An optical disk apparatus has a galvanic mirror error signal generation circuit for detecting that the galvanic mirror rotates more than an allowed limit value in directions P and Q. When it is detected by the galvanic mirror error signal generation circuit that the galvanic mirror rotates more than the allowed limit value, the light intensity of the light spot is changed from the recording-use (or erasing-use) light intensity into the reproducing-use light intensity. Accordingly, recording and erasing of information is always carried out by the projection of the light beam having a predetermined light intensity, thereby always providing a high grade of optical disk apparatus.

Abstract: An information recording and reproducing device has a first recording clock generation circuit which generates a clock based on pre-recorded information on a magneto-optical disk, a second recording clock generation circuit and a switching circuit The switching circuit selects a first recording clock when recording information is of discrete information and selects a second recording clock when recording information is of successive information. Moreover, in the present device, a first reading clock is used as well as a second clock as a clock for reading out the reproduced data from the magneto-optical disk, which had been once stored in memory. The second reading clock having a reference frequency is generated by a second clock generation circuit and is used for reading out successive information such as music information.

Abstract: The invention provides an improvement of the conventional laser driving circuit mainly including a control logic circuit, a reproducing power producing circuit, and a recording power producing circuit for preventing a recording film of a disk from being damaged by a laser in a reproducing mode. The improved respect is addition of a voltage monitoring circuit and a bypass transistor for an abnormal signal. The voltage monitoring circuit monitors a voltage drop caused in the control logic circuit and supplies a voltage abnormality indicating signal, thereby causing the bypass transistor to be conductive for allowing the abnormal signal to be flown therethrough.

Abstract: A track jumping apparatus for an optical disk pickup which can detect a tracking error signal in performing a track jump, and determine a time of acceleration or deceleration of a jump signal by comparing the tracking error signal with a reference level, the track jumping apparatus comprising storing device for storing of standard values corresponding to the kinds of track jumps, standard value selecting device for selecting a standard value corresponding to a kind of track jump in performing the track jump, reference level setting device for setting a reference level so that the ratio of the reference level to a peak value of the tracking error signal agrees with a value based on the standard value selected by the standard value selecting device in performing the track jump, and standard value amending device for amending the standard value in the storing device selected at that moment according to a state of the tracking error signal at the end of the track jump.

Abstract: A feedback control apparatus in an optical recording and reproducing device for recording, reproducing and/or erasing data from an optical recording medium projects a light beam emitted from an optical head onto the optical recording medium. The apparatus includes an actuator for controlling the illuminating conditions of the light beam projected onto the optical recording medium, a detection unit for detecting the illuminating conditions of the light beam projected onto the optical recording medium, and a control amplifier for driving the actuator in accordance with a detection signal outputted from the detection unit, thereby controlling the illuminating conditions of the light beam projected onto the recording medium.

Abstract: A method of controlling the rotational velocity of an information recording disk having one or more tracks in which patterns and marks are formed, the marks including at least one specific pattern having a predetermined length, which method comprises: measuring a time during which each of the patterns passes; detecting each of the marks on the basis of the values of the measured times; and controlling the rotational velocity of the disk on the basis of the measured time of the specific pattern of the detected mark, thereby making the linear velocity of the detected mark constant.

Abstract: An optical disc medium indexing system having a plurality of elongated parallel tracks wherein each track contains a nonerasable index portion located in less than a single frame. The index portions are formed on the substrate of the disc by a plurality of indentations representing the absolute address of each track on the disc recorded in a multiplex format. Each index portion containing information on the mark, track number and CRC. The disc is constructed so that information may be recorded on the entire surface of the medium including the indexed portions.