Abstract: In an optical system including an optical source with an effective aperture for generating a radiation beam to be applied to a data track of an optical storage medium, including optics disposed between the optical source and the data track of the optical storage medium which defines an optical axis along which light is projected to the data track and displacing the optical axis of the return beam to cause it to be substantially outside the effective aperture of the optical source to reduce feedback into the optical source, and a constructive interference beam splitter disposed between the optics and the optical source for producing a beam of light projected along the optical axis and defraction beams and including at least one coating of transparent material selected of a predetermined thickness to cause an increase in the amount of light projected along the optical axis and a desired defraction beam by decreasing light in the non-desired defraction beams.

Abstract: A method of track access is provided which, when there is a large offset in the neutral position of a focusing lens, achieves stable tracking servo operation and prevents a slowing down of access time.

Abstract: An optical pickup for irradiating a first recording medium and a second recording medium with light, at least one of the substrate thickness and the refractive index of the first recording medium being different from that of the second recording medium, where the optical pickup includes: a light source for emitting the light; a polarized beam splitter for receiving the light and for transmitting at least a portion of the light while reflecting the remaining portion of the light depending on the polarization direction of the light; a first objective lens for focusing the portion of the light reflected by the polarized beam splitter onto the first recording medium; and a second objective lens for focusing the portion of the light transmitted through the polarized beam splitter onto the second recording medium.

Abstract: An optical storage disk for use in an optical storage system includes a storage layer which is capable of being disrupted when a laser bee of sufficient intensity is focused thereon. The optical storage disk has a transparent substrate layer on one side of the storage layer and a lacquer layer on the other side of the storage layer. The disruptions provided by the laser beam are selected to provide human readable and/or machine readable patterns. The optical disk can be of the type with data written thereon during fabrication, or the disk can be of the type in which data can be impressed thereon after fabrication of the optical disk. The patterns on the optical disk can be in the form of optical bar codes. In one application of the present invention involving the type of disk on which data can be written after fabrication, the pattern resulting from application of the laser beam to the disk is read by an optical reading device and transferred to the disk in the data format.

Abstract: A variable transfer rate data reproduction system is provided which performs a reproduction operation and a reproduction inhibit operation cyclically to reproduce data recorded on a recording disc. A pickup traces a spiral track formed on the recording disc during the reproduction operation and is also controlled to continue to trace a following portion of the track over a plurality of track turns during the reproduction inhibit operation without a track jump. Upon resumption of the reproduction operation, the pickup jumps over the plurality of tracks to return back to a portion of the track where the reproduction operation has been interrupted previously. This results in decreased mechanical stress acting on mechanical parts for moving the pickup.

Abstract: A reproduced signal is digitized so as to count a time interval of a specified pattern simultaneously with the count of a clock period of a phase lock loop circuit. A phase lock loop clock frequency is subjected to a feedback control based on the information indicated the difference between the time interval and the clock period. In this manner, a frequency loop performs a feedback operation so that a frequency of the reproduced signal falls within a capture range of a phase lock-in, thereby increasing the speed of phase lock-in.

Abstract: A magnetic recording/reproducing apparatus compares speed information obtained by speed detecting means for a magnetic tape with a set travelling speed of the magnetic tape in a control circuit, and controls the rotational frequency of a driving motor for a take-up reel, thereby controlling constant-speed travelling of the magnetic tape, with employment of no capstan. According to this system, the overall apparatus can be simplified and miniaturized with reduction in weight and cost. Further, it is possible to improve constant-speed travelling performance of the magnetic tape by adjusting resonance and antiresonance appearing due to total equivalent inertia moment related to the magnetic tape and reels in the transfer characteristic of the control system.

Abstract: An optical unit (1) is provided for optically scanning a surface, particularly an information surface of a recording medium (9). The unit comprises a frame (13), a radiation source unit (15), a rotatable mirror unit (17), and an objective system (19) for forming a scanning spot on the information surface, which objective system has an entrance pupil (19b) and an optical axis (19a). From an optical point of view, the rotatable mirror unit is situated between the radiation source unit and the objective system, suspension means being provided for movably supporting the objective system relative to the frame. The suspension means allow a longitudinal movement of the objective system along the optical axis and a pivotal movement of the objective system about a pivot which coincides with the point of intersection of the optical axis and the entrance pupil. Actuating means drive the objective system in accordance with these movements.

Abstract: When information signals are recorded on an information signal recording medium formed with circular information signal tracks, the information signals are recorded after being scrambled with scrambling signals of cyclic codes. The period at which the scrambling signal makes a round is determined longer than a time length of an information signal quantity recorded on the maximum recording capacity (e.g., the outermost tracks), or a part of the scrambling signals are used repeatedly. The information signal recording method can remove the correlation between the adjacent tracks, and thereby enable a stable tracking control.

Abstract: An information recording-reproduction method wherein: upon reproducing, recorded information corresponding to a predetermined number of sectors from the leading sector of each of a plurality of information tracks on an optical disk is preliminarily stored on a buffer memory, and during a period in which the optical pickup is shifted to another information track, the recording information, stored in the buffer memory, is reproduced; and upon recording, during a period in which the optical pickup is shifted to another information track, recording information is temporarily stored in the buffer memory, and after completion of the recording, the recording information is recorded on the optical disk. In this method, information tracks, which are formed on the optical disk discontinuously with one .another, are regarded as if they were continuous tracks, and the apparent recording and reproducing operation is carried out continuously.

Abstract: A method and apparatus for preventing generation of third generation data of an original data recorded on a read-only region of a partial read-only memory (ROM) optical disk includes an operation for copying source data from the partial read-only memory to a read-write medium by first attempting to write check data on a read-write region of the partial ROM optical disk. If the check data cannot be written, the copy operation terminates. If the check data can be written, the source data is overwritten. Then, the source data is copied from the partial ROM optical disk to the read-write medium.

Abstract: A digital signal compressing device includes a unit for dividing an input signal into plural bands duping information compression, a unit for producing frequency-domain data of the input signal divided into plural bands, and a unit for operating on frequency-domain characteristics. The unit for operating on frequency-domain characteristics operates on the frequency-domain characteristics so that the condition of canceling the aliasing noise by the frequency division and subsequent frequency synthesis performed by a synthesis filter in association with the division at the time of information expansion will be maintained. The frequency-domain characteristics of the input signal can be acted on easily without obstructing the condition of canceling the aliasing noise without requiring a new mechanism or device other than the information compressing mechanism or device.

Abstract: Methods and apparatus are provided for simultaneously tracking multiple data tracks of an optical disk using a detector matrix formed of a plurality of pixels. Based on track pitch, pixel pitch and predetermined point spread functions of the pixels, a series of simultaneous equations based on sampled pixel data is generated and solved to determine an offset distance between a selected pixel and a selected track and corrected values of the sampled pixel data. Alternatively, the series of equations may be generated, based on sample pixel readout values and a series of weighting coefficients, such that solution of the equations enables the position of a selected track may be determined.

Abstract: An optical pickup device including a lighting source, a condensing apparatus, a diffracting means, and a light detector. The light source generates and emits a light beam to the diffracting means. The diffracting means includes a center region and an outer region which encloses the center region. As the light travels from the light source towards the optical storage medium the main zero-order beam which reads the information on the disk encounters only the center region of the diffracting means while the two sub-beams used for track following are created as +1 and -1 diffraction orders from the outer region of the diffracting means. The three beams reflected from the recording medium all pass through the center region of the diffracting means and are diffracted in the direction of the detector therefrom.

Abstract: It is an object to provide a digital signal reproducing apparatus which can correctly reproduce a digital signal by suppressing a deterioration in decoding performance of a Viterbi decoding even when an asymmetry occurs in an information digital signal read from an optical disc. An amplitude-limited sample value is obtained by limiting an amplitude of a sample value obtained by sampling the read signal up to a predetermined amplitude limit value. The amplitude limit sample values are Viterbi decoded on the basis of a plurality of prediction samples including prediction sample whose values are respectively equal to the predetermined upper and lower amplitude limit values.

Abstract: A disk drive provides a defect list for each recording surface itemizing selected areas of recording surface by location, size and graded by an expected abnormal error rate. The defect list is utilized upon formatting of a recording surface to rate sectors as available or unavailable depending upon a map of data types to be written to the sectors and alignment of the map to the defects.

Abstract: An apparatus and method for measuring and compensating for birefringence in a rotating ground glass disk (20) such as are employed in polarization based optical flying height testers. The polarized light (1, 3) impinges on the top surface (24) of the disk (20) and is refracted through the disk to a measurement point (90) on the opposite surface (25) from which it is reflected back through the disk (20) and refracted before it exits the disk (20) in a beam (9) containing both s aand p polarizations which are detected by a phase detector (13) which measures any difference in phase between the s and p polarizations. Any variation of the phase .theta..sub.G with respect to the position defined by the measurement point provides the birefringence parameters b.sub..parallel.,b.sub..perp. for the positions on the disk (20). The phase detector (13) measures the phase .theta..sub.G at a skew angle .zeta.

Abstract: If data stored in RAM (31) is of a data volume short of one cluster, deficit data is read out from a magneto-optical disc (22) to provide a data volume corresponding to one cluster. Data recorded on the magneto-optical disc (22) is rewritten by means of the RAM (31) on the cluster basis under control of a system controller (29).

Abstract: An optical writing and/or reading device. A radiation source (10) generates a radiation beam (11). This radiation beam (11) is directed by an optical system onto a servotrack (4) of a rotating record carrier (1). The beam reflected via the record carrier is passed on to a push-pull detector (12). The servotrack has a periodical radial wobble whose frequency is modulated in accordance with a position-information signal. A signal-regaining circuit (17) regains the position-information signal from the push-pull signal. A balancing circuit (41, 42; 50, 51) adjusts a weighting the ratio between the detection signals which contribute to the difference signal. The DC component in the adapted push-pull signal is derived by means of a low-pass filter (44). In dependence upon the determined DC component, a circuit (45) sets the weighting ratio to a value at which the determined DC component is substantially zero.

Abstract: Methods and apparatus are provided for simultaneously reading data from multiple tracks of an optical disk at a high rate. Circuitry is provided for use with a detector matrix to read and buffer data in parallel from the multiple adjacent tracks, while asynchronously providing processed data to a host processor. Circuitry is also provided for electronic tracking of tracks on the optical disk and for reducing cross-talk between adjacent tracks. Circuitry is further provided for correcting phase errors resulting from variations in the linear velocity of the tracks being read, depending upon the radial position of the tracks.