Abstract: The present invention relates to an optical pick-up apparatus having a laser beam source and an objective lens to converge the luminous flux from the laser beam source onto the information recording surface of an optical information recording medium through a transparent substrate of the optical information recording medium such as CDs or DVDs, and specifically relates to a technology to move a divergence degree changing means such as a collimator lens or the like, in the direction of the optical axis, and/or to a technology to move the laser beam source in the direction of the optical axis, corresponding to the thickness of the transparent substrate of the optical information recording medium, in order to read information from plural types of optical information recording mediums having different transparent substrate thickness.

Abstract: An apparatus for recording or reproducing information on an information recording surface of an optical information recording medium having a transparent substrate, includes a laser source to emit a light beam having a wavelength of .lambda. nm; and an objective lens to converge the light beam emitted from the laser source on the information recording surface of the optical information recording medium through the transparent substrate. When the light beam is converged through the transparent substrate of the optical information recording medium, a wavefront aberration of the objective lens has a curve which has a step at a numerical aperture (NA), and the following conditions are satisfied,W.sub.1 -W.sub.2 =m.lambda.-.delta.,0<.delta.<0.34.lambda.where W.sub.1 represents a wavefront aberration at a point of the step when the curve is traced from a periphery toward an axis of the lens, W.sub.

Abstract: An optical pickup apparatus includes: a laser source for emitting a laser light beam; a converging optical system for converging the light beam emitted from the laser source onto an information recording surface through a transparent substrate of an optical information recording medium, the converging optical system including a lens surface so that a spherical aberration is discontinuous in a third numerical aperture (NA3) on a side of the optical information recording medium, and the third numerical aperture (NA3) is satisfied the following condition,NA1>NA3.gtoreq.

Abstract: An optical pickup apparatus includes: a laser light source; a light converging optical system for converging a light beam emitted from the laser light source onto a first information recording surface of a first optical information recording medium having a thickness t1 of a transparent substrate, or a second information recording surface of a second optical information recording medium having a thickness t2 of a transparent substrate. The light converging optical system has a best fit wavefront aberration of 0.07 .lambda. rms or less at a numerical aperture of NA1 when the thickness t1 of the transparent substrate is used, and has a best fit wavefront aberration of 0.07 .lambda.

Abstract: The present invention relates to an optical pick-up apparatus having a laser beam source and an objective lens to converge the luminous flux from the laser beam source onto the information recording surface of an optical information recording medium through a transparent substrate of the optical information recording medium such as CDs or DVDs, and specifically relates to a technology to move a divergence degree changing means such as a collimator lens or the like, in the direction of the optical axis, and/or to a technology to move the laser beam source in the direction of the optical axis, corresponding to the thickness of the transparent substrate of the optical information recording medium, in order to read information from plural types of optical information recording mediums having different transparent substrate thickness.

Abstract: An magneto-optical head that detects information recorded magneto-optically in accordance with changes in polarization conditions of light reflected from a magneto-optical recording medium on which convergent light is projected, includes a birefringent polarizer having a plane of incidence on which a polarization-separation coating is formed and a plane of emergence that is substantially in parallel with the plane of incidence. The birefringent polarizer composed of at least two crystallines is arranged to be inclined to an optical path along which the reflected light advances toward a photo-detector as a convergent light. A chief ray of reflected light from a recording medium enters the plane of incidence of the birefringent polarizer with an incident angle between 55.degree. and 70.degree..

Abstract: Disclosed is an optical pickup device for use in an optical disk unit, which comprises a moving optical system and a fixed optical system. The moving optical system has a focussing lens confronting a disk-shaped information-recording medium and moves linearly in the radial direction of the information-recording medium. On the fixed optical system are disposed a beam-deflecting lens as tracking means and a relay lens for conjugating the position of the principal point of this beam-deflecting lens with the position of the focal point on the beam-incident side of the object lens when the moving optical system is present at an intermediate position within the moving range of the moving optical system. In the optical pickup device having this structure, track offset can be diminished over the entire reproduction region, and since no tracking means is disposed in the moving optical system, high-speed excess can be easily performed.