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: An information reproduction apparatus for reading information of an optical recording medium is provided with: a first detecting device which supplies a difference between respective output signals optically obtained by a pair of detectors for reading information of a first track; a second detecting device and a third detecting device which supply a difference between respective output signals optically obtained by a pair of detectors for reading information of a second track and a third track respectively, the third and second tracks being placed on opposite sides of the first track; a crosstalk extracting device which extracts crosstalk caused by the second and third tracks, which is included in a detected signal supplied from the first detecting device; and a tracking control device which executes tracking control for the first detecting device based on a balance between the crosstalks caused by the second and third tracks.

Abstract: There are disclosed an information reproduction apparatus, signal processing apparatus, and information reproduction method which can remove a crosstalk to a wobble signal, particularly a crosstalk attributed to an RF signal. The information reproduction apparatus for reading information of an optical recording medium includes a detector for outputting a difference between individual output signals optically obtained by a pair of detectors for reading the information of a first track, a detector for reading RF information of a second track adjacent to the first track, a demodulator for demodulating a detection signal outputted from the detector, and a crosstalk canceller which uses the detection signal outputted from the detector to cancel the crosstalk arising from the RF information of the track included in the detection signal outputted from the detector.

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: The invention relates to an optical disc of the next generation which is capable of recording data at a high density by using an optical system having a larger numerical aperture and a reproduce beam of light with a shorter wavelength than those used with a conventional DVD. The optical disc includes an information recording layer where information is recorded as an array of pits at a predetermined track pitch, and a light transmitting layer formed on the information recording layer and having a film thickness of 0.13 mm or less. The information recorded therein is reproduced upon irradiation of a beam of light having a wavelength ranging from 400 nm to 415 nm onto the information recording layer through the light transmitting layer from an objective lens having a numerical aperture ranging from 0.75 to 0.86. In this disc, a taper angle of the pits is 55 degrees or higher.

Abstract: An information offering apparatus for a vehicle includes: a device for setting at least one piece of vehicle information relating to fuel consumption of a vehicle, the vehicle information being output from a vehicle information detector when a predetermined time elapses after the beginning of use of the vehicle; a device for calculating a histogram of vehicle information or a standard deviation during the use of the vehicle based on the set vehicle information; a device for marking the vehicle information based on a point set in the histogram or the standard deviation; a device for calculating an evaluation result based on the point of each of the marked vehicle information; and an notifying device for notifying a driver of the evaluation result.

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: 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: An optical pickup for reading information recorded on information tracks of a recording medium by using a main light beam and a subsidiary light beam includes a diffraction device for diffracting an original light beam to generate the main light beam and the subsidiary light beam. The main light beam is applied to a reading track which is one of the information tracks on which the information to be read is recorded. The subsidiary light beam is applied to the information track adjacent to the reading track.

Abstract: An objective lens that allows spherical aberration to be suppressed during the reproduction of a CD without sacrificing reproduction characteristics of a DVD, has a first numerical aperture comprising a refracting surface that is in rotatory symmetry about an optical axis. A part of the refracting surface is displaced along the optical axis as an annular concave (or convex) portion centered on the optical axis. The annular concave (or convex) portion has a certain inner diameter r.sub.1 and a certain outer diameter r.sub.2 that reduce RMS aberration V to a value close to a minimum value. The annular portion has a certain depth (or height).

Abstract: A method and an optical pickup device for generating a focus error signal are disclosed. The device includes an irradiation optics for irradiating laser beams onto an information recording surface of an optical disc, a first and a second photodetector for receiving reflected light, and photodetection optics having an astigmatism generating element for applying astigmatism to light reflected from the information recording surface and for introducing the reflected light to the first and the second photodetectors. The device also includes first and second photodetecting circuits which generate a first and a second preliminary focus error signal. The photodetecting circuits include a first and a second diagonal adder connected to the first and the second photodetector, and a diagonal differential device connected to the first and the second diagonal adders for generating an output difference between outputs of the first and the second diagonal adders as the first and the second preliminary focus error signals.

Abstract: A method of generating a focus error signal in an optical pickup device including a photodetector including a light receiving surface for receiving the reflected light and divided into first to fourth quadrants defined in a tangential direction and in a radial direction from the center of the light receiving surface and at least four elements positioned in a centrally symmetric relationship with respect to the center of the light receiving surface within the first to fourth quadrants. A preliminary focus error signal is generated as an output difference between an addition output of one pair of the elements placed on centrally symmetric positions of the photodetector and an addition output of the other pair of the elements placed on centrally symmetric positions of the photodetector.

Abstract: Disclosed is an optical disk having rows of pits, corresponding to information signals, formed on a transparent substrate, and a reflective film formed on this substrate. The reflective film is formed of amorphous silicon (a-Si) or indium antimonide (InSb), which exhibits a third-order non-linear optical effect. Thus, the reflectance of the reflective film formed of this material increases nearly in proportion to the intensity of the irradiated beam spot. The beam spot irradiated on the optical disk has the highest intensity at the center portion and this intensity becomes weaker as a point in the spot approaches the edge. Therefore, the effective spot size of the beam spot can be reduced, making it possible to reproduce from the reflection type optical disk information signals with a spatial frequency above the cutoff spatial frequency defined by the reproducing optical system. In other words, a row of pits recorded at a high density can be reproduced.

Abstract: An information detection light intensity control apparatus in an apparatus reproducing information recorded in an optical disc in which a reflectance has a dependency on an incident light intensity, comprising a light source for emitting an information detection light which enters the optical disc and a control system for controlling an intensity of the information detection light which enters the optical disc so that a ratio of an intensity of the information detection light which enters the optical disc and an intensity of the information detection light reflected from the optical disc is set to a predetermined value.

Abstract: A reflective film is formed over a recording surface of an optical disk on which pits are formed. The reflective film is made of a non-linear optical material which, when light is incident thereon, generates second harmonics of the incident light. In a reproduction optical system for reproducing this optical disk, when a reading beam reflected by the reflective film of the optical disk impinges on a filter for filtering out the basic wave of the reading beam, the filter only transmits the second harmonics which are then incident on a light receiver. Since information signals recorded on an optical disk is reproduced by reading only second harmonics of the reflected beam, the cut-off spatial frequency of the OTF can be made twice higher as compared with a conventional reproducing apparatus. In other words, the recording density of the recording medium can be made higher.

Abstract: An optical disk having two transparent and a refelection film. The reflection film is made of a non-linear optical material in which reflectance increases according to intensity of incident light thereto. The reflection film has a multiple reflectance.

Abstract: A reflected beam from a reflective film of an optical disk exhibiting light intensity dependency is efficiently received. In the optical system, a collimator lens, a polarization beam splitter, a quarter wave plate and an objective lens are disposed in turn in an optical path between a laser and an optical disk from the laser side. A light receiver is disposed on another optical path extending from the polarization beam splitter. A light receiving aperture diameter of the objective lens for passing the reflected beam from the optical disk therethrough is made larger than an incident aperture diameter of the objective lens for impinging the reading beam on the recording medium. This structure enables information signals to be recorded at higher density on the recording medium to be reproduced.