Abstract: An optical pickup device includes an irradiating optical system for converging a light beam to form a spot on a recording surface via a light-transmitting layer of an optical recording medium, and a photodetection optical system for converging return light reflected and returned from the spot on a photodetector. The device detects wave aberration and focal error of the light beam. A diffractive optical element is disposed on the optical axis of return light in the photodetection optical system and provided with an annulus. The diffractive optical element annularly extracts, from return light, ray components in the vicinity of a predetermined radius on a pupil on the emitting pupil surface of the irradiating optical system, which is affected by the wave aberration generated in the optical system.

Abstract: A tilt angle detection device and method which generates, as a first push-pull signal, a difference between light reception signals corresponding to two light receiving surfaces of one side of a photodetector, which are divided along the track tangent direction; generates, as a second push-pull signal, a difference between the light reception signals corresponding to two light receiving surfaces of the other side of the photodetector; and generates a tilt signal that indicates a tilt angle defined by a normal on the recording surface of the optical recording medium at a position of irradiation of the laser beam and the optical axis of the laser beam in accordance to a difference between amplitudes of the first and second push-pull signals.

Abstract: An optical disc includes an information recording layer having a record of information as a pit train with a predetermined track pitch and a light-transmissive layer formed on the information recording layer so that the information can be reproduced by a beam of light illuminated through the light-transmissive layer to the information recording layer by an objective lens. The optical disc includes a feature in that a relationship of 0.194(?/NA)2?TP ×Tmin?0.264(?/NA)2 is satisfied, provided that the track pitch is TP, a pit shortest length is Tmin, a wavelength of the light beam is ? and a numerical aperture of the objective lens is NA. The optical disc also includes a feature in that a pit width is 120 nm or smaller in a range of a track pitch of 0.280 to 0.325 ?m.

Abstract: A focus servo device is for focusing a light irradiated from a light source onto a recording medium surface via an objective lens. Assuming that a wavelength of the light is ?, a numerical aperture of the objective lens is NA, an average run length period of the recording medium standardized with ?/NA is RL, the track pitch standardized with ?/NA is TP, and the capture range of said focus servo device is CR [?m], the following equation applies: 0.114/(RL?0.72)+0.84?CR?18000(TP?0.69)5+3.13.

Abstract: An objective lens for converging light onto an information recording medium includes a refracting interface for converging an incident light into a convergent light, and a refractive index varying member disposed between the refracting interface and the information recording medium, and having a refractive index that is varied according to an externally applied voltage.

Abstract: It is an object to provide a recorded information reproducing apparatus that allows to eliminate crosstalk from an adjacent track correctly, even from a recording medium having both a recorded area in which information data are recorded and an unrecorded area. In order to detect a crosstalk component from an adjacent track based on a correlation between a main read signal read from a main track and a sub read signal read from an adjacent track, the relative phase between the sub read signal and the main read signal is shifted.

Abstract: The object of the present invention is to provide a data recording method and optic recording medium that is capable of reproducing address data accurately by reducing the correlation of address data between adjacent tracks, reducing the effect of cross-talk between adjacent tracks on the recording clock and by making it possible to apply a cross-talk canceller to the wobble signal. The data-recording method of recording data while controlling the correlation between a first data string and a second data string that are contained in recording data, and is provided with a selecting process of selecting inversion/no inversion of first data string such that the correlation between first data string and second data string is reduced; and a recording process of recording first data string according to selected inversion/no inversion polarity, and recording control code that indicates whether inversion/no inversion was selected for first data string.

Abstract: A focus servo device is for focusing a light irradiated from a light source onto a recording medium surface via an objective lens. Assuming that a wavelength of the light is ?, a numerical aperture of the objective lens is NA, an average run length period of the recording medium standardized with ?/NA is RL, the track pitch standardized with ?/NA is TP, and the capture range of said focus servo device is CR [?m], the following equation applies: 0.114/(RL?0.72)+0.84?CR?18000(TP?0.69)5+3.13.

Abstract: An information playback apparatus of the present invention is provided with: a first detecting unit for supplying a difference between respective output signals optically obtained by a pair of detectors for reading the information of the first track; a second detecting unit for supplying a difference between respective output signals optically obtained by a pair of detectors for reading the information of the second track adjacent to the first track; a first demodulating unit for demodulating a detected signal supplied from the first detecting unit, a second demodulating unit for demodulating a detected signal supplied from the second detecting unit. A coefficient controlling unit extracts the crosstalk caused by the second track, which is included in a demodulation signal obtained by the first demodulating unit, from the same signal and controls a coefficient based on the extracted crosstalk, and cancels the crosstalk by the calculated coefficient.

Abstract: An optical pickup apparatus includes a photodetector for receiving a diffracted light reflected from the recording medium; and a tilt detector for detecting a tilt amount of the recording medium on the basis of a light intensity within an interference region of a 0th-order diffraction light and at least one diffraction light other than the 0th-order diffraction light of the reflected light received by the photodetector.

Abstract: A focus error detecting apparatus and a focus error detecting method of an optical pickup in which the system is not easily influenced by track transversal noises and an optical disc thickness error and which can be used together with a 3-beam system or a DPD system. The return light from an optical disc is divided to a first optical path and a second optical path by a hologram device, a predetermined astigmatism is applied to the light on each divided optical path, the light is received and detected by a first detector and a second detector, and a focusing error signal is obtained by predetermined arithmetic operations.

Abstract: An information reproducing apparatus(100) is provided with: a focusing device(11a) which makes a signal-reading probe light converge onto an optical recording medium(10); a focus servo device(12) which maintains a focus on a recording layer of the optical recording medium(10) by controlling the focusing device(11a); an offset providing device(14) which provides a predetermined offset to a target value used by the focus servo device(12); and a spherical aberration detecting device(17) which detects a signal indicative of spherical aberration contained in the probe light on the basis of an intensity of a signal reproduced based on a plurality of target values obtained by the offset providing device(14) generated on at least one signal of at least one predetermined spatial frequency recorded on the optical recording medium(10).

Abstract: A tilt angle detection device and method which generates, as a first push-pull signal, a difference between light reception signals corresponding to two light receiving surfaces of one side of a photodetector, which are divided along the track tangent direction; generates, as a second push-pull signal, a difference between the light reception signals corresponding to two light receiving surfaces of the other side of the photodetector; and generates a tilt signal that indicates a tilt angle defined by a normal on the recording surface of the optical recording medium at a position of irradiation of the laser beam and the optical axis of the laser beam in accordance to a difference between amplitudes of the first and second push-pull signals.

Abstract: An objective lens for converging light onto an information recording medium includes a refracting interface for converging an incident light into a convergent light, and a refractive index varying member disposed between the refracting interface and the information recording medium, and having a refractive index that is varied according to an externally applied voltage.

Abstract: It is an object to provide a recorded information reproducing apparatus that allows to eliminate crosstalk from an adjacent track correctly, even from a recording medium having both a recorded area in which information data are recorded and an unrecorded area. In order to detect a crosstalk component from an adjacent track based on a correlation between a main read signal read from a main track and a sub read signal read from an adjacent track, the relative phase between the sub read signal and the main read signal is shifted.

Abstract: An optical disk has a recording layer recording information as a row of marks and non-marks alternately appearing in a groove formed at a track pitch of 0.280 &mgr;m or greater and a light transmissive layer formed over the recording layer, to reproduce information due to a light beam having a wavelength in a range of 375 nm to 415 nm and illuminated by an objective lens having a numerical aperture NA in a range of 0.80 to 0.90 through the light transmissive layer to the recording layer. The groove has a depth in a range of 18 nm to 32 nm.

Abstract: A recorded information reproducing apparatus has a crosstalk canceler to ensure fast convergence of the values of filter coefficients of an adaptive digital filter and stable operation. The recorded information reproducing apparatus comprises a reading unit for reading recorded information from one track on a recording medium to acquire a first read signal, and for reading recorded information from at least one track adjacent to the one track to acquire a second read signal; an operating unit for operating at least one coefficient on the second read signal; a subtracter for subtracting an output of the operating unit from the first read signal; and a coefficient setting unit for setting the at least one coefficient and for restricting the at least one coefficient in such a way that the at least one coefficient becomes greater than a first predetermined value or smaller than a second predetermined value.

Abstract: An optical disc comprises an information recording layer having a record of information as a pit train with a predetermined track pitch and a light-transmissive layer formed on the information recording layer so that the information can be reproduced by a beam of light illuminated through the light-transmissive layer to the information recording layer by an objective lens. The optical disc is characterized in that a relationship of 0.194 (/NA)2 TP×Tmin 0.264 (/NA)2 is satisfied, provided that the track pitch is >TP, a pit shortest length is Tmin, a wavelength of the light beam is and a numerical aperture of the objective lens is NA. The optical disc is characterized in that a pit width is 120 nm or smaller in a range of a track pitch of 0.280 to 0.325 m.

Abstract: A disc has a physical factor changing a shape or a reflection coefficient in a tangential direction of a record track.

Abstract: The object of the present invention is to provide a data recording method and optic recording medium that is capable of reproducing address data accurately by reducing the correlation of address data between adjacent tracks, reducing the effect of cross-talk between adjacent tracks on the recording clock and by making it possible to apply a cross-talk canceller to the wobble signal. The data-recording method of recording data while controlling the correlation between a first data string and a second data string that are contained in recording data, and is provided with a selecting process of selecting inversion/no inversion of first data string such that the correlation between first data string and second data string is reduced; and a recording process of recording first data string according to selected inversion/no inversion polarity, and recording control code that indicates whether inversion/no inversion was selected for first data string.