Abstract: Information recording disk comprising a main recording track comprising one or more interruptions and/or changes of turn, this giving rise to non-sequential reading and therefore to information which is difficult to access. The copying of such a disk by conventional means becomes very difficult, and this will make it possible on the one hand to detect counterfeits by detecting the information and on the other hand to render any copy unusable.

Abstract: As pit patterns a pattern A and a pattern B are prepared. The adjacent tracks are made to have different embossed pit patterns.

Abstract: An information recording medium 1 at least comprises a substrate 13 having a microscopic pattern 20, which is constituted by a shape of continuous substance of approximately parallel grooves formed with a groove section G and a land section L alternately, a recording layer 12 formed on the microscopic pattern 20 and a light transmission layer 11 formed on the recording layer. The microscopic pattern 20 is formed so as to satisfy a relation of P<&lgr;<NA and a thickness of the light transmission layer 11 is within a range of 0.07 to 0.12 mm, wherein P is a pitch of the groove section G or the land section L, &lgr; is a wavelength of reproducing light beam and NA is a numerical aperture of an objective lens. Further, there provided an information recording medium, which is improved in cross erase and recorded in high density, and a reproducing apparatus and a recording apparatus for the information recording medium.

Abstract: For an optical recording medium having a phase change type recording layer on its a substrate and having as read only area and a writable area in a recording area, a data recording method is provided which records data in the writable area. This data recording method comprises a transfer step of transferring program data recorded in the read only area in a practical form to an external computer, and an execution step (step A10) of automatically executing the program data in the external computer to record data in the writable area, which can facilitate manufacturing and reduce the possible of destruction or falsification of ROM data.

Abstract: With append_only_flag reset to 0, data is recorded over existing data on a disc in accordance with the value of volume_write_protect_level. With append_only_flag set to 1, on the other hand, data can not be recorded over existing data on the disc but can be appended to already recorded data in a range defined by the value of volume_write_protect_level. As a result, it is possible to prevent new data from being written over already recorded data by mistake and to utilize the recording area of the disc efficiently.

Abstract: A table having a plurality of recording densities and a plurality of recording/reproducing conditions corresponding to the recording densities and each necessary for recording/reproducing a signal at a corresponding recording density is recorded in a TOC region of a magneto-optical disk. A recording/reproducing apparatus finds out a recording density at which it can record/reproduce data from the table and records or reproduces a signal at the recording density. The recording/reproducing conditions include the wavelength of a semiconductor laser, whether or not to employ the optical pulse magnetic field modulation recording method, the presence/absence of an optical super resolution pickup, whether or not to employ the optical pulse reproducing method, whether or not to employ the PRML method and the like.

Abstract: A method for generating a land/groove (L/G) switching signal from pits on a land/groove (POLG) type disc and an apparatus therefor. In the method for generating an L/G switching signal from pits on a POLG type disc having tracks with wobbles, in which header information is recorded in sectors of each track, the header information including physical identification data (PID) and a peak header and a bottom header distinguished by envelopes of the peak header signal and the bottom header signal and both the peak and bottom header signals having phases according to lands or grooves, the phases of the peak header signal and the bottom header signal are compared to determine a track switching point and the sequence of sectors is determined using the physical identification data of the disc.

Abstract: A reproducing apparatus for reading, or a recording apparatus for writing, data from or to a disc having pre-formed thereon a pair of concentrical or spiral tracks adjacent to each other and to which a common address is given, is adapted to control the time at which a read or write head is moved from one to the other of the pair of tracks or vice versa.

Abstract: An optical reproducing device according to the present invention detects mean amplitude values of short marks and long marks, which are recorded marks for reproducing power control, by means of a short mark level detecting circuit and a long mark level detecting circuit. Then a differential amplifier compares a ratio between these two mean amplitude values with a standard value, and outputs the result of this comparison. Thereafter, a reproducing power control circuit controls reproducing power of a semiconductor laser such that the absolute value of this comparison result is reduced. Since mean values of the amplitude values of the short marks and long marks are detected, the detection results are very accurate, and the precision of control of reproducing power can be greatly improved.

Abstract: Stream data has a recording data structure formed in units of stream blocks (or stream object units SOBU) which are segmented to have a predetermined data size. Data are recorded (or encoded) and partially erased (or temporarily erased) in units of the stream blocks (SOBUs).

Abstract: Recording surface of an optical disk is segmented radially into a plurality of volumes each including a lead-in area, program area and lead-out area. In each of the volumes, information indicating presence of a succeeding volume is recorded in a main channel of the program or lead-out area. Dedicated player can receive the information indicating presence of a succeeding volume during reproduction of the first volume and thus is allowed to access the second volume. By contrast, non-dedicated or ordinary CD-ROM players have no capability to read the information indicating presence of a succeeding volume and thus is only allowed to reproduce the first volume without knowing the presence of the succeeding volume.