摘要:
An optical medium reproducing apparatus that optically reproduces an optical medium on which a plurality of tracks is formed in which a beam returning from the optical medium is divided into a first region of an outside portion and a second region of an inside region, according to the shape of the pupil of an object lens, and crosstalk between the tracks is reduced by using a first detection signal of the first region and a second detection signal of the second region.
摘要:
An optical information processing apparatus includes: a unit that radiates light onto an optical disc and detects the reflected light to output a reproduced signal; a unit that corrects spherical aberration of the light; a unit that adjusts a focus position of the light based on a focus adjustment value; and an adjustment unit that measures a characteristic of the reproduced signal at each of at least three positions on each of at least three straight lines on a plane with coordinate axes representing an amount of spherical aberration correction and focus adjustment value, obtains, from the measurements, as estimated positions, at least five positions on the plane at which the characteristic has substantially the same value, performs an ellipse approximation on the estimated positions, obtains a center of the ellipse, and determines the amount of spherical aberration correction and focus adjustment value based on the center of the ellipse.
摘要:
A focus error amplitude obtaining device is configured to obtain amplitudes of a focus error signal. An error amplitude difference calculation device is configured to calculate an error amplitude difference which is a difference between the amplitudes of the focus error signal obtained at two different positions in a moving range of a spherical aberration correction device. An appropriate position search control device is in charge of overall control of structural elements; spherical aberration correction device movement control device, focus error amplitude obtaining device, and error amplitude difference calculation device. The appropriate position search control device decides an appropriate position of the spherical aberration correction device based on the error amplitude difference.
摘要:
An optical beam shaper (10) for converting a radiation beam (5, 6, 7, 8) having an elliptical cross-section into a beam (9) having a more circular cross-section is described. This element (10) has a cylindrical entrance surface (12) and a toroidal exit surface (14) and can be arranged close to a diode laser (1) so that the risk of wavefront deviations due to defocusing is reduced. The element has a high coupling efficiency. The beam shaper is also provided with a grating for forming a sub-beam from the radiation beam.
摘要:
In an optical pickup unit including a diffraction grating for separating an incident beam from a laser diode into a main beam, first and second sub beams, the diffraction grating separates the incident beam into the first and the second sub beams so that each of the first and the second sub beams has, on an optical disc, an elliptic spot shape which becomes longer in a radial direction of the optical disc and which spans at least two tracks.
摘要:
An optical system includes a semiconductor laser for emitting a laser beam, a coupling lens for converting the laser beam a parallel beam, an optical beam shaping system for increasing the diameter of the parallel beam in a direction in which the semiconductor laser has a smaller far field pattern, and an objective lens for focusing a beam shaped by the optical beam shaping system into a spot. To make the spot substantially circular in shape and increase the light utilization efficiency, the magnification of the optical beam shaping system in a direction parallel to the junction plane of the semiconductor laser is selected to fall in a certain range.
摘要:
In an optical system for synthesizing a plurality of light beams, a first light beam of parallel light rays emitted from a laser beam source is incident on an inclined face of a right angle prism through the prism. A second light beam of parallel light rays emitted from a laser beam source is incident to the inclined face at a predetermined angle of incidence. The first light beam is emitted to the inclined face at an angle of incidence equal to a critical angle so that the first light beam is totally inflected by the inclined face and transmitted in a predetermined direction. The second light beam is refracted at an angle of refraction substantially equal to the Brewster's angle, and then transmitted in a direction which defines a predetermined angular difference with the predetermined direction of the first light beam. A multi-layered film is formed on the inclined face. The film makes the angle of refraction of the second light beam approach the critical angle, so as to reduce the angular difference from that which would exist in the absence of the film.
摘要:
The inventive system optically records information signals on a recording disc. A light source, such as a laser beam, for example, emits a light which is modulated in conformance with an information signal that is to be recorded. An optical system converts this light into a beam having a large width in the longitudinal direction of a track formed on the recording disc. There is a small beam dimension in the transverse direction of the track. A slit plate within the optical system limits the width of the light to cause a constant beam width in the transverse direction of the track. A focusing lens receiving, as incident light, such a limited light beam forms a light spot on the recording disc which is small in the longitudinal direction of the track and large in the transverse direction of the track. The light spot forms a plurality of pits in the upper surface of the recording disc. Each of these pits has a small width in the longitudinal direction of the track and a constant large width in the transverse direction of the track, thereby to record the information signal along the track on the recording disc.
摘要:
An optical information processing apparatus includes: a unit that radiates light onto an optical disc and detects the reflected light to output a reproduced signal; a unit that corrects spherical aberration of the light; a unit that adjusts a focus position of the light based on a focus adjustment value; and an adjustment unit that measures a characteristic of the reproduced signal at each of at least three positions on each of at least three straight lines on a plane with coordinate axes representing an amount of spherical aberration correction and focus adjustment value, obtains, from the measurements, as estimated positions, at least five positions on the plane at which the characteristic has substantially the same value, performs an ellipse approximation on the estimated positions, obtains a center of the ellipse, and determines the amount of spherical aberration correction and focus adjustment value based on the center of the ellipse.
摘要:
An optical pickup apparatus detects optical information by making a laser beam in a 405 nm wavelength band emitted from a semiconductor laser light source incident on an optical information recording medium and then making the laser beam reflected from the optical information recording medium incident on a photodetector. The optical pickup apparatus has a polarizing beam splitter including a polarizing beam splitting film that forms an optical path from the semiconductor laser light source to the optical information recording medium by reflecting the s-polarized component of the laser beam and that forms an optical path from the optical information recording medium to the photodetector by transmitting the p-polarized component of the laser beam; and a monitoring sensor that receives the laser beam to monitor the laser output intensity of the semiconductor laser light source. The polarizing beam splitter transmits part of the s-polarized component, and the monitoring sensor receives this part of the s-polarized component in a position where the center line of the effective light beam received by the monitoring sensor does not coincide with the principal ray of that part of the s-polarized component.