Abstract: A speed detection apparatus includes a storage unit configured to store time when each of first and second sensors detects an arbitrary detection mark and an address corresponding to the detection mark. The speed detection apparatus further includes a same mark detection time identification unit configured to identify, based on output information from a reference speed detection unit, time when the first and second sensors detect the same mark, based on the address and the time stored in the storage unit, and a relative speed calculation unit configured to calculate, based on output information from the same mark detection time identification unit, a speed of the first sensor and the second sensor relative to a scale member.

Abstract: 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.

Abstract: A velocity detection apparatus detects a position of a moving object at a first timing and a second timing to detect a velocity of the moving object based on a difference between the first timing and the second timing. The first timing is a timing at which an identifiable mark position of the moving object is detected by a first detector and the second timing is a timing at which the mark position is detected by a second detector. The velocity detection apparatus includes a light source and first and second detectors which detects the mark position based on light obtained by illuminating the moving object using the light source. A vertical projection position of the light source onto a plane which is parallel to a main surface of the first or second detector is located between vertical projection positions of the first and the second detector onto the plane.

Abstract: A speed detection apparatus includes a storage unit configured to store time when each of first and second sensors detects an arbitrary detection mark and an address corresponding to the detection mark. The speed detection apparatus further includes a same mark detection time identification unit configured to identify, based on output information from a reference speed detection unit, time when the first and second sensors detect the same mark, based on the address and the time stored in the storage unit, and a relative speed calculation unit configured to calculate, based on output information from the same mark detection time identification unit, a speed of the first sensor and the second sensor relative to a scale member.

Abstract: A displacement detection apparatus includes a scale 115 on which marks are disposed, first and second position detection sensors 111 and 112 detecting positions of the marks 110, and a processor 409 performing a calculation processing of an output signal from each of the first and second position detection sensors 111 and 112. The first and second position detection sensors 111 and 112 are disposed at a distance L from each other to be movable relative to the scale 115. The processor 409 calculates a correction value P? of a mark pitch P of the marks 110 using the distance L, a first time TPK required for K marks of the marks 110 to pass a detection position, and a second time TL required for a specific mark of the marks 110, which are measured at the same time of the first time TPK, to move the distance L.

Abstract: 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.

Abstract: A displacement detection apparatus includes a scale 115 on which marks are disposed, first and second position detection sensors 111 and 112 detecting positions of the marks 110, and a processor 409 performing a calculation processing of an output signal from each of the first and second position detection sensors 111 and 112. The first and second position detection sensors 111 and 112 are disposed at a distance L from each other to be movable relative to the scale 115. The processor 409 calculates a correction value P? of a mark pitch P of the marks 110 using the distance L, a first time TPK required for K marks of the marks 110 to pass a detection position, and a second time TL required for a specific mark of the marks 110, which are measured at the same time of the first time TPK, to move the distance L.

Abstract: A velocity detection apparatus detects a position of a moving object at a first timing and a second timing to detect a velocity of the moving object based on a difference between the first timing and the second timing. The first timing is a timing at which an identifiable mark position of the moving object is detected by a first detector and the second timing is a timing at which the mark position is detected by a second detector. The velocity detection apparatus includes a light source and first and second detectors which detects the mark position based on light obtained by illuminating the moving object using the light source. A vertical projection position of the light source onto a plane which is parallel to a main surface of the first or second detector is located between vertical projection positions of the first and the second detector onto the plane.

Abstract: 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.

Abstract: A multi-level information reproducing method is provided which can increase the degree of separation between distributions of cell boundary values to thereby improve the accuracy of reproduction. Specifically, in a method of reproducing multi-level information recorded on a track of an optical information recording medium by virtually providing cells at equal intervals and by varying a width of an information pit in a track direction or an area of an information pit, a cell boundary value (a value obtained by sampling a reproduced signal when a center of a light spot is located at a boundary of cells) is corrected based on cell center values of two cells adjacent to the boundary (a value obtained by sampling a reproduced signal when the center of the light spot is located at a center of a cell), and the multi-level information is reproduced based on the corrected cell boundary value.

Abstract: 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 ? 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).

Abstract: A method of adjusting spherical aberration correction and focus offset of a light beam comprises steps of: detecting a first approximate straight line 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; detecting a second approximate straight line indicating a second relationship between the spherical aberration correction and the focus offset according to a second evaluation index indicating a quality of reproduced signal; and determining a spherical aberration correction value and a focus offset value to be adjusted from an intersection of the first approximate straight line and the second approximate straight line.

Abstract: 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 ? 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).

Abstract: The object of the present invention is to realize reduction of the level jitter generated from a noise component at a signal saturation level or a waveform distortion in a portion except for signal polarity portions (rising edge and falling edge), and good error characteristics. In the present invention, a predetermined upper or lower limit value is set to reproduction signals, the reproduction signals are subjected to a limiter processing for correcting reproduction signals of the upper limit value or more, or the lower limit value or less to the level of the upper limit value or the lower limit value, respectively, the signal subjected to the limiter processing is subjected to a partial response equalizing (PR equalizing) processing, and PR reproduction is performed to improve the level jitter at PR detection time and the error rate at information reproduction time.

Abstract: Provided is a simple method of adjusting spherical aberration and a focus offset. According to the adjusting method of the present invention, focus offset adjustment and spherical aberration adjustment are performed based on the fact that the dependence of a focus offset on a spherical aberration correction value (SA) is changed between a first evaluation index indicating a track cross signal characteristic and a second evaluation index indicating a reproduction signal characteristic. A spherical aberration correction value (SA) obtained when a first focus offset and a second focus offset which are related to the first evaluation index and the second evaluation index, respectively, become optimum points is used together with a focus offset value associated with the spherical aberration correction value. Therefore, predetermined processing steps are performed to uniquely obtain an optimum spherical aberration correction value (SA) and an optimum focus offset.

Abstract: An optical information reproduction method includes the steps of detecting, in at least two adjacent virtual cells provided in a recording/reproduction area of an optical information medium, at least two cell center signal levels and a cell boundary signal level between the cell center signal levels and acquiring phase error information of a reproduction signal based on a difference between the detected cell boundary signal level and an ideal cell boundary signal level obtained in advance and on a gradient of reproduction signal levels corresponding to the detected cell center signal levels.

Abstract: A manufacturing method of a domain wall displacement type magneto-optical recording medium comprises the steps of depositing a magnetic layer on a substrate to prepare a disc, and irradiating the magnetic layer with a converged light beam while applying a magnetic field and annealing the magnetic layer a converged light beam between information tracks.

Abstract: A multi-level information reproducing method is provided which can increase the degree of separation between distributions of cell boundary values to thereby improve the accuracy of reproduction. Specifically, in a method of reproducing multi-level information recorded on a track of an optical information recording medium by virtually providing cells at equal intervals and by varying a width of an information pit in a track direction or an area of an information pit, a cell boundary value (a value obtained by sampling a reproduced signal when a center of a light spot is located at a boundary of cells) is corrected based on cell center values of two cells adjacent to the boundary (a value obtained by sampling a reproduced signal when the center of the light spot is located at a center of a cell), and the multi-level information is reproduced based on the corrected cell boundary value.

Abstract: The present invention provides a magneto-optical recording method capable of securing a sufficient phase margin, even if a recording power or medium temperature fluctuates, and obtaining a reproduction signal having a preferable quality, wherein the time phases of a laser pulse and a modulation magnetic field are set to a time phase of maximizing in which a recording power margin.

Abstract: According to the present invention, a light beam is radiated to an area between recording tracks while the intensity of a magnetic field from the outside to a magneto-optical recording medium is suppressed to 50 Oe or less, whereby magnetic anisotropy formed between the recording tracks is set to be lower than that of the magnetic layer on the recording tracks, and micro-domains, for example, having a diameter smaller than a half-width of a light beam for reproduction in a film surface direction are formed on recording tracks. Because of this method, the influence of a leakage magnetic field in the magneto-optical recording medium adopting a DWDD reproducing system is alleviated.