摘要:
A magnetooptical recording/reproducing apparatus is provided with a device for determinating a power of a light beam which is emitted from a light source. In the apparatus, the light beam is irradiated on a magnetooptical recording medium while a magnetic field modulated according to a recording signal is applied to a portion on which the light beam is being irradiated. Light reflected from the medium upon the irradiation of the light beam thereto is detected by a detector, the output from which is used to reproduce the recording signal. The amplitude of the recording signal is detected from the reproduction signal. The power of the light beam to be emitted from the light source is determined on the basis of the detected amplitude of the recording signal.
摘要:
Disclosed is a method of recording information on a magnetooptical recording medium, which medium includes a first magnetic layer and a second magnetic layer having a lower Curie temperature and a higher coercive force at room temperature than those of the first magnetic layer. The second magnetic layer is exchange-coupled to the first magnetic layer. The first magnetic layer has a higher compensation temperature than the Curie temperature of the second magnetic layer. The method of recording information includes applying a magnetic field, which is modified in accordance with information from a magnetic head, to the medium to record information on the first magnetic layer and scanning the medium with a light beam to heat the medium to a temperature at least near the Curie temperature of the second magnetic layer so as to transfer the information recorded on the first magnetic layer to the second magnetic layer.
摘要:
A displacement measuring apparatus including: a first light detector including a first emitter illuminating optically identifiable marks disposed on a moving body, and a first light receiver detecting light through the marks; a second light detector including a second emitter illuminating the marks and a second light receiver detecting light through the marks, wherein the second light detector is arranged at a predetermined interval from the first light detector in a moving direction of the moving body; an identical point detecting unit detecting a first timing at which the first and second light detector detecting an identical mark among the marks, and a second timing; a velocity calculating unit calculating a velocity of the moving body by using the first and second timing determined by the identical point detecting unit; and a time-sharing light emitting unit allowing the first and second emitter to emit the light in a time-sharing manner.
摘要:
A method of adjusting spherical aberration correction and focus offset of a light beam. A first approximate straight line is detected indicating a first relationship between the spherical aberration correction and the focus offset according to a first evaluation index indicating a quality of cross-track signal. A second approximate straight line is detected indicating a second relationship between the spherical aberration correction and the focus offset according to a second evaluation index indicating a quality of a reproduced signal. A spherical aberration correction value and a focus offset value, to be adjusted, are determined from an intersection of the first approximate straight line and the second approximate straight line.
摘要:
To provide a regenerative signal evaluation method in which the transition of polarity of a regenerative signal, or the change of polarity in a record mark sequence, is dealt with employing an index in correlation with an error ratio of binarization result by a maximum likelihood decoding. The method comprises detecting a recording series on a state transition path having a certain Euclid distance by the maximum likelihood decoding corresponding to a change of polarity of record code in the recording series, acquiring a likelihood difference between the most probable state transition path and the secondly probable state transition path from branch of state transition paths to merge of state transition paths in the detected recording series, and conducting a statistical processing for the likelihood difference individually corresponding to the change of polarity in the recording series to evaluate the quality of reproducing signal.
摘要:
Disclosed herein is a testing process for recording for presetting optimum recording power for a domain wall displacement type magneto-optical medium, the process comprising the steps of: recording a first record pattern on an Nth track on the magneto-optical medium; separately recording a second record pattern on an (N−1)th track and an (N+1)th track adjacent to both sides of the Nth track with varied recording power; reproducing the Nth track to detect a change in the pulse width of a reproduction signal; detecting recording power, at which cross writing occurs, on the basis of the detected result; and presetting optimum recording power on the basis of the recording power at which cross writing occurs.
摘要:
A method for reproducing information on a magneto-optical medium comprises causing temperature distribution on the magneto-optical medium by projection of a light beam and displacing domain walls by the temperature gradient, wherein a detected reproduction signal is corrected by subtraction therefrom of a signal derived by delaying the detected reproduction signal by a prescribed time .beta. and multiplying the delayed signal by an amplitude gain .alpha.. An apparatus for reproducing information on a magneto-optical medium with regard to the above method comprises a first circuit for generating reproduced signals from reflection of the light beam, a second circuit for generating a modified signal derived by delaying the reproduction signal by a prescribed delay time .beta. and multiplying an amplitude gain .alpha., and a third circuit for subtracting the modified signal from the reproduced signal.
摘要:
A recording power row P(i) is selected and a signal is recorded in a recording test region of an optical disk, while shifting a recording power, to detect a reproduced signal amplitude row m(i) that corresponds to the recording power row P(i). The relation of the recording power row P(i) and the row of multiplication products P(i)×m(i) is linearly approximated and the intersection of the linear approximation straight line and the recording power axis is computationally determined as recording threshold power Pthr, for at least three recording power rows Pj(i) that are centered at Pf(j) in the recording power row P(i) within a defined range. Then, the recording power Pt(j) is computed as a multiplication product of the recording threshold power Pthr(j) and a factor κ contained in the disk information, for each recording power row Pj(i). Finally, the optimum recording power Pwopt is computationally determined according to the at least three recording powers Pt(j).
摘要:
The present invention provides a domain wall displacement-type magnetooptical recording medium effective for decreasing jitter, in which a conventional herringbone recording mark can be changed to a linear mark. The magnetooptical recording medium of the present invention includes a substrate having lands and grooves, and a magnetic layer deposited on the substrate so as to be magnetically interrupted between the lands and the grooves, wherein the magnetic film deposited on each of the lands has a section having a flat bottom, and a substantially flat top in the central portion of each of the lands, either side having a thickness decreasing in the direction to the side end.
摘要:
A displacement measuring apparatus including: a first light detector including a first emitter illuminating optically identifiable marks disposed on a moving body, and a first light receiver detecting light through the marks; a second light detector including a second emitter illuminating the marks and a second light receiver detecting light through the marks, wherein the second light detector is arranged at a predetermined interval from the first light detector in a moving direction of the moving body; an identical point detecting unit detecting a first timing at which the first and second light detector detecting an identical mark among the marks, and a second timing; a velocity calculating unit calculating a velocity of the moving body by using the first and second timing determined by the identical point detecting unit; and a time-sharing light emitting unit allowing the first and second emitter to emit the light in a time-sharing manner.