Abstract: In a magneto-optical recording technique by which an improved domain expansion reading is achieved, a mark region is recorded as a sub-mark portion and an adjacent sub-space portion, wherein the sum of predetermined first and second lengths of the sub-mark and sub-space portions, respectively, is changed in dependence on the pattern of marks and spaces. The write strategy enables writing a long run length with sub-mark and/or sub-space lengths selected independent of the channel bit length, such that a long run length can be written with few well-chosen domains with a stray field larger than the minimum field for MAMMOS readout. In this way, differences in readout conditions for all combinations of short and long run lengths can be eliminated, resulting in substantially improved power margins for random data.

Abstract: A method of and apparatus for varying a recording density of a data storage system. The method includes setting a range of a region whose recording density is to be changed, judging whether a region in which data read and write commands are to be executed is within the set range, and performing data read and write operations by allocating only one data among a plurality of continuous tracks as a data track if the region in which the data read and write commands are to be executed is within the set range.

Abstract: A method of reading out data from a domain expansion data storage such as a MAMMOS magneto-optic disk (1) which includes a data storage layer in which data is stored in the form of magnetic marks, and an expansion layer capable of copying and expanding domains from the storage layer, the system applying a first radiation beam (7), having a first spot size on the disk, in order to initiate copying of a domain from the storage layer to the expansion layer, and applying a second radiation beam (9), having a second spot size larger than the first spot size on the disk, in order to read out data from the expansion layer.

Abstract: The present invention relates to magneto-optical recording technique whereby improved domain expansion reading is achieved. A mark region is recorded as a sub-mark portion and an adjacent sub-space portion, wherein the length of the sub-mark portion is set to be less than or equal to the length of the sub-space portion. Stray field variations due to different runlengths of the recording data can thus be equalized even for short channel bit lengths, while the resolution and/or power margin is improved.

Abstract: The present invention provides a method of recording information on a magneto-optical recording medium of domain wall displacement type having a preformat area and a data area succeeding thereto, comprising the steps of generating a reproduction signal from said medium by utilizing a light beam, detecting a reference position based on said reproduction signal, determining, based on a result of the detection, a recording start timing at which a formation of a recording magnetic domain is started at a distance at least not shorter than a displacement amount of a domain wall away from a start position of said data area; and starting a recording with said determined recording start timing.

Abstract: A magneto-optical recording medium has magneto-optical recording layers (11, 12, 13) and reproducing layers (21, 22, 23). The information recorded in the reproducing layers are reproduced by means of reproducing light beams (31, 32, 33) of different wavelengths, respectively. In reproduction, magnetic domains (4) recorded in the recording layers are transferred in the reproducing layers formed on the respective recording layers, the transferred magnetic domains (5) are enlarged with an external magnetic field, and the information is reproduced. Since information is recorded and reproduced for each recording layer, the recording density is improved. Further since the reproduction signals are amplified by the magnetic domain enlargement, the C/N is improved.

Abstract: A method of designing a thermally-assisted magnetic recording apparatus having a magnetic recording medium, a heater and a magnetic head includes, determining a stable retention time tst for recorded magnetization and a thermal-fluctuation stability coefficient ?st calculated from ?(T)=KuV/kBT, where Ku is a magnetic anisotropy energy density, V is an activation volume, and kB is Boltzmann's constant, obtaining an equivalent degradation time tEQ calculated from tEQ=?(?tEQ), that sums values of ?tEQ within a period of time ?t for a time span during which the medium is substantially degraded, where ?tEQ=exp(ln(?t)????st) and ? is a thermal-fluctuation stability coefficient for a medium temperature T in ?t, and determining specifications of the medium, the heater and the magnetic head in a manner to meet the relationship of tEQ<tst.

Abstract: The present invention relates to a method, an apparatus and a record carrier for controlling radiation power and/or field strength during a reading operation from a magneto-optical recording medium comprising a storage layer and a read-out layer. An expanded domain leading to a pulse in a reading signal is generated in said read-out layer by copying a mark region from said storage layer to said read-out layer upon heating by said radiation power and by applying an external magnetic field. A pulse pattern in the reading signal is analyzed. The analyzing result is compared with run length characteristics of the data stored in said storage layer. The radiation power and/or the magnetic field strength are controlled on the basis of the comparison result. Thus, much less or no disc capacity has to be reserved for radiation power and/or magnetic field calibration, since the user data can be used for this purpose.

Abstract: A method for performing full optimization of most of the files on a volume in accordance with a composed optimization plan, is performed, including the separation of less frequently accessed files from those whose number or location of clusters is being more frequently modified by user applications. Optimization does not continue indefinitely—it reaches a final state even if a small percentage of its file data is still out of place under the optimization plan and therefore not in the planned part of a plan-defined, Placed Files Area. Each time a Push of out-of-place file data is attempted, or a Pull of file data into a correspondingly planned free space within the Placed Files Area is attempted, a copy of the current volume bitmap is made in order to determine what is the largest free space currently available in the Placed Files Area. Once determined, the size of the largest free space is compared to the size of the largest out-of-place range of corresponding clusters in the Placed Files Area.

Abstract: The present invention relates to a method and an apparatus for reading information from a domain expansion magneto-optical recording medium, wherein the duration of the expansion direction of an external magnetic field is determined according to the upper limiting frequency of the reading system. The reading density and power margin can thus be improved.

Abstract: In a magneto-optical disk drive using a domain wall moving magneto-optical recording medium, the test-writing adjustment in operation to deal with dynamic fluctuation factors is minimized, and a reproducing or recording laser power is automatically optimized.

Abstract: A recording/reproducing apparatus for a domain-wall-displacement magneto-optical recording medium with good format efficiency, capable of providing a good reproduction signal and securing a maximum recording region for a user is provided which comprises a recording circuit that starts recording of an information in a data region at a predetermined timing with a detection signal obtained in the preformat region being used as a reference, and a reproducing circuit that starts reproducing of the information recorded in the data region at a timing earlier than the predetermined timing with the detection signal being used-as a reference.

Abstract: A reproducing apparatus reproduces a signal recorded in a magneto-optical disk. The magneto-optical disk includes a layered structure having a recording layer, an intermediate layer and a reproducing layer. Laser light is illuminated from an optical head to the magneto-optical disk in such an intensity that no magnetic domain is transferred from the recording layer to the reproducing layer only by the laser light. In this state, alternating magnetic field is applied through a magnetic head to the magneto-optical disk, thereby concurrently causing transfer and expansion of a magnetic domain to the reproducing layer. As a result, transfer of the magnetic domain is effected with expansion.

Abstract: A reproducing apparatus for a magneto-optical recording medium has, at one end of a swing arm, a magneto-optical head provided with a slider and a solid immersion lens. A reproducing light beam-detecting system is installed to the other end of the swing arm. During reproduction on a magneto-optical recording medium, an alternating magnetic field is applied while radiating a reproducing light beam which is power-modulated to have a low power and a high power in synchronization with a reproducing clock. The reproducing light beam having the low power causes transfer of a magnetic domain in the information-recording layer to the reproducing layer and magnification thereof. The reproducing light beam having the high power extinguishes the magnified magnetic domain. Minute magnetic domains can be individually reproduced at high C/N.

Abstract: A laser beam for reproduction emitted from an LD (41) at the time of reproduction passes through an As correction board (42) and a grating (43) and becomes incident on a beam splitter (44). The beam splitter (44) transmits the laser beam and causes the laser beam to be incident on a liquid crystal unit (45). Then, at the time of reproduction, a light spot shaping device provides aberration to the laser beam transmitted through the liquid crystal unit (45) in accordance with the type of a magneto-optical disc and thus shapes a light spot on the magneto-optical disc. Therefore, optimum light spots for different media can be shaped.

Abstract: The present invention relates to a method and an apparatus for reading information from a domain expansion magneto-optical recording medium, wherein the duration of the expansion direction of an external magnetic field is determined according to the upper limiting frequency of the reading system. The reading density and power margin can thus be improved.

Abstract: The present invention relates to magneto-optical recording technique whereby improved domain expansion reading is achieved. A mark region is recorded as a sub-mark portion and an adjacent sub-space portion, wherein the length of the sub-mark portion is set to be less than or equal to the length of the sub-space portion. Stray field variations due to different runlengths of the recording data can thus be equalized even for short channel bit lengths, while the resolution and/or power margin is improved.

Abstract: A magnetic lens has a reproducing layer and a magnetic slit. When the leak magnetic field Hlk of a recording magnetic domain on a recording disk exceeds the coercive force He of the magnetic slit, the magnetization in the magnetic slit is inverted into the same direction as that of the magnetization of the recording magnetic domain. Transition occurs from the inplane magnetization to the perpendicular magnetization in a magnified area of the reproducing layer in which the temperature exceeds the critical temperature Tcr. The upward magnetization in the magnetic slit is transferred thereto. The magnetization information on the recording magnetic domain is reproduced with amplified signal intensity on the basis of the magneto-optical effect by detecting the reflected light beam of the reproducing light beam from the magnified area. A plurality of minute magnetic domains contained in an object can be detected respectively at a high sensitivity in an independent manner.

Abstract: Disclosed herein is a magneto-optical reproducing apparatus for reproducing information recorded on a magneto-optical medium comprising a substrate, and a first magnetic layer, a second magnetic layer and a third magnetic layer which are laminated on the substrate in that order, the first magnetic layer being a magnetic film relatively smaller in domain wall coercivity and greater in domain wall displaceability at a temperature close to ambient temperature compared with the third magnetic layer, and the second magnetic layer being a magnetic film having a Curie temperature lower than the first magnetic layer and the third magnetic layer, the apparatus comprising: an optical system that the medium is irradiated with a light beam, domain walls of a magnetic domain for information formed on the medium being displaced by the irradiation of the light beam; a photosensor for detecting a change in the polarization direction of reflected light of the light beam to output a reproduction signal; a differentiating ci

Abstract: A reproducing apparatus reproduces a signal recorded in a magneto-optical disk. The magneto-optical disk includes a layered structure having a recording layer, an intermediate layer and a reproducing layer. Laser light is illuminated from an optical head to the magneto-optical disk in such an intensity that no magnetic domain is transferred from the recording layer to the reproducing layer only by the laser light. In this state, alternating magnetic field is applied through a magnetic head to the magneto-optical disk, thereby concurrently causing transfer and expansion of a magnetic domain to the reproducing layer. As a result, transfer of the magnetic domain is effected with expansion.

Abstract: A magneto-optic recording medium includes a second auxiliary magnetic film, a first auxiliary magnetic film and a magneto-optic recording film on a substrate. The auxiliary magnetic films change from in-plane magnetization to vertical magnetization at critical temperatures TCR1 and TCR2. Since they have the relation TCR1>TCR2, the magnetic domain transferred from the magneto-optic recording film to the first auxiliary magnetic film at the time of reproduction is expanded in diameter and is transferred to the second auxiliary magnetic film when the temperature profiles of the auxiliary magnetic films inside an optical spot are utilized. The magnetic domain of the magneto-optic recording film can be expanded and transferred, too, by means of magnetostatic coupling by using a non-magnetic film in place of the first auxiliary magnetic film. Pulse reproduction light subjected to power modulation in synchronism with a reproduction clock can be used at the time of reproduction.

Abstract: A magneto-optical recording medium includes a reproducing layer. When a laser beam is irradiated to the magneto-optical recording medium, a magnetic domain in a recording layer is transferred, through enlargement, to a reproducing layer increased in temperature. The magneto-optical recording medium further includes a calibration area that has a calibration magnetic domain recorded in a predetermined pattern in the recording layer. In a reproducing apparatus, a laser beam of an optical head is adjusted in output depending upon a reproduced signal obtained by reproducing the calibration magnetic domain.