Sharp Kabushiki Kaisha Corporation

Tomiyuki Numata

Kunio Kojima

Shigemi Maeda

Shigeo Terashima

Tsuneo Fujiwara

Hiroshi Fuji

Toshihisa Deguchi

Takashi Iwaki

Kentaroh Tsuji

Takeshi Yamaguchi

Masaru Nomura

Jun Akiyama

Tomoyuki Miyake

Tetsuo Ueyama

Tetsuya Okumura

Kohji Minami

Masaru Ogawa

Masanori Ushioda

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 T, thereby to move the collimator lens, and is caused to return the lens to the position of the origin at a pulse rate Thigher than the pulse rate T, and counts a clock number B of drive pulses required for returning the lens, and repeats the counting while raising the rate Tstage 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 Tbeing one stage lower than the rate Tat which the occurrence of the step-out has been judged, as the pulse rate of the operation of correction of spherical aberration.

Drive control apparatus, drive control method and optical pickup apparatus

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.

Optical miniaturized module, optical pickup device, and optical disk device provided with light source and photodetector

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.

Signal evaluation devices and signal evaluation methods, signal quality evaluation methods and reproducing devices and recording devices

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&#x2013;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.

Optical disk and optical disk apparatus using spatially separated grooves and lands for recording tracks

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.

Optical disk device using an optical pickup as a read mechanism for

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.

Data detecting circuit

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. So, when the reproducing area is changed from the main information unrecorded area to the main information recorded area, the synchronizing with the reproduced signal is carried out in a short time, thereby improving the reliability of the reproducing process.

Information reproducing apparatus for properly synchronizing the

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.

Optical disk apparatus

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. The first reading clock in synchronization with the reproduced signal is generated by a first reading clock generation circuit and is used for reading out discrete information such as computer-use data. In addition, in the case of discrete information, it is possible to start recording/reproducing operation immediately after an optical head reaches a desired position, thereby permitting to shorten an access time.

Information recording and reproducing device providing faster access

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.

Semiconductor laser driving circuit with control circuit power voltage

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.

Track jumping apparatus for an optical disk pickup

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. The apparatus further includes a switching device for selectively switching from a detection signal from the detection unit to a reference signal, or vice versa, and for inputting into the control amplifier, the reference signal having the same signal level as that of a detection signal which is expected to be outputted from the detection unit when the illuminating conditions of the light beam projected onto the recording medium are appropriate. An offset compensation device outputs an offset compensation signal to the control amplifier. The offset compensation signal is set such that a control signal generated in the control amplifier has a predetermined signal level when the reference signal is inputted into the control amplifier. The apparatus prevents a DC offset from being included in the control signal from the control amplifier and reduces the procedures required for adjustment during the manufacturing process without employing expensive parts and devices and the like, thereby lowering the production costs.

Feedback control apparatus in an optical recording and reproducing device

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.

Method for controlling the rotational velocity of an information

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.

Optical recording medium track indexing system

An apparatus for recording and reproducing information on and from an optical disk includes a first control for producing a first control signal for controlling the rotational speed of a rotational driving apparatus, on the basis of the detected radial position; a judging apparatus which judges whether or not the reproduced signals are reproduced from a recorded region of the optical disk; a second control for producing a second control signal for controlling the rotational speed of the rotational driving apparatus, on the basis of the signals reproduced from the disk; and a switch apparatus which switches the circuit so that the rotational driving apparatus is controlled by the first control signal when the reproduced signals are not reproduced from a non-recorded region, and controlled by the second control signal when the reproduced signals are reproduced from a recorded region.

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Tenri, Japan

Tomiyuki Numata