Abstract: According to this invention, general addresses are given to a multi-layer information storage medium to facilitate handing of information. That is, it is possible to set generalized addresses for multiple information layers, and information indicating a condition for setting the general addresses, e.g., the contents of a disk ID zone in a rewritable zone of a lead-in area, is recorded on an information reproducing layer.

Abstract: According to this invention, general addresses are given to a multi-layer information storage medium to facilitate handing of information. That is, it is possible to set generalized addresses for multiple information layers, and information indicating a condition for setting the general addresses, e.g., the contents of a disk ID zone in a rewritable zone of a lead-in area, is recorded on an information reproducing layer.

Abstract: A head control apparatus of the invention includes a moving unit for moving an optical head to a given information track on an optical disk having concentric information tracks, a detector for detecting a direction of movement of the optical head from the a signal reproduced from the optical head, and a controller that, when the detector has detected the direction of movement of the optical head, controls the moving unit so that the optical head may move to a specified information track at a first speed, and that, when the detector has not detected the direction of movement the optical head, controls the moving unit so that the optical head may move to a specified information track at a second speed slower than the first speed.

Abstract: According to this invention, an optical signal processing apparatus for an optical disk has an actuator for moving an optical head in an radial direction of the optical disk, a plurality of first photodiodes for receiving a light beam reflected by the optical disk, an addition circuit for generating a first sum signal representing a sum of signals from the first photodiodes, a polarizing beam splitter for splitting the light beam reflected by the optical disk in accordance with directions of polarization, a plurality of second photodiodes for receiving light passing through the polarizing beam splitter, a subtraction circuit for generating a difference signal representing a difference between signals from the second photodiodes, and a circuit for determining a moving direction of the optical head, using the sum signal and the difference signal during a seek operation.

Abstract: An optical disk unit having a light spot incident upon an optical disk. The light spot is radially moved to cross tracks formed on the optical disk. The tracks are provided with specific access marks. The number of access marks passed by the light spot as well as the number of tracks crossed by the light spot until a change is found in a detected access mark are counted. The latter number is divided by the former number and multiplied by a coefficient to provide a speed signal indicative of a speed of the light spot relative to the optical disk.

Abstract: An optical disk apparatus is used for an optical disk having a plurality of types of access marks repeatedly formed on the optical disk, each access mark being constituted by at least two pits. The apparatus comprises an optical head for optically reading a pattern represented by each of the access marks, a discrimination circuit for discriminating whether or not the pattern is correctly read out by the optical head, a storage for storing a pattern of access mark which is discriminated to be correct by the discrimination circuit until the discrimination circuit discriminates the next pattern of the access marks, and cross track count detector for comparing the pattern stored in the storage with the correct pattern discriminated by the discrimination circuit and for calculating the cross track count from these two patterns.

Abstract: Disclosed is an optical disk apparatus applied to a data writing/reproducing operation of a sample-servo formatted optical disk having a clock pit and two wobbled pits in each of servo regions. A photodetector receives reflected light of a light beam from the optical disk to produce a reflected light signal. A clock detection unit detects a change in intensity of reflected light components from the clock pit in response to the reflected light signal to produce a binary clock pit detection signal. A tracking error detection unit detects a change in peak intensity of reflected light components from the wobbled pits in each servo region in response to the reflected light signal to produce a binary tracking error signal representing the detected intensity difference. A determination unit is connected to the clock detection unit and the tracking error detection unit.

Abstract: An optical disk unit is incidence a light spot upon an optical disk. The light spot is radially moved to cross tracks formed on the optical disk. The tracks are provided with specific access marks. The number of access marks passed by the light spot as well as the number of tracks crossed by the light spot until a change is found in a detected access mark are counted. The latter number is divided by the former number and multiplied by a coefficient to provide a speed signal indicative of a speed of the light spot relative to the optical disk.

Abstract: A magneto-optic recording/erasing system uses two heads, one for writing formatted information into sectors along a track of a magneto-optical disk and a second head working simultaneously with the first head to read formatted information and detect defects. The system also writes information during formatting to indicate damaged disk track sectors and eliminate reference to them during formatting to produce a more reliable disk.

Abstract: An information recording and reproducing system for a magneto-optical disk having first and second optical systems each including at least first and second optical heads arranged in the positions displaced for example, by 1/4 sectors with each other. A single sector address control unit connected to the first and second optical heads for detecting each sector address on a disk and for controlling each access of the first and second optical means to each of desired sectors on the disk, through a magneto-optical disk control unit. The first and second optical heads are positioned at a first position, e.g., sector head position, of one sector, the second optical head is positioned at a second position, e.g., data position of the other sector, such that when either one of the first or second optical head is detecting one sector address, the other has finished in the address detection for the other sector address.