Abstract: An optical data recording and reproducing apparatus includes a laser source, a collimating lens made of a single lens having a positive power to collimate the divergent laser beams emitted from the laser source, and an objective lens which is to converge the collimated light onto a data recording surface of a data recording medium. The chromatic aberration of the objective lens is corrected to reduce the back focal distance thereof as the wavelength increases to cancel the chromatic aberration of the collimating lens.

Abstract: A chromatic aberration correcting element that is a simple lens having at least one aspheric surface the radius of curvature of which increases from the optical axis toward the periphery, at least either one of the surfaces being formed as a diffraction lens surface that consists of annular segments in steps that are shifted discretely in a direction in which the lens thickness increases as a function of the distance from the optical axis. Also, a chromatic aberration correcting device having annular segments formed in steps on either a light entrance face or a light exit face or both, the annular segments being composed of planes perpendicular to and concentric with the optical axis.

Abstract: An objective lens system used in an optical system of an optical disk device. The objective lens system includes at least one lens element and converges light emitted from a light source onto a reflecting layer of an optical disk. The lens element has an offense against the sine condition OSC, and the optical disk has a substrate thickness T and a refractive index n. A ray of light exits the lens element and intersects an optical axis of the lens element at an angle .alpha.. The values of OSC, .alpha., n and T satisfy the following relationship for light rays that are incident on the objective lens system at distances from the optical axis of the objective lens system which are least equal to a predetermined percentage of an effective height of an aperture of the objective lens: ##EQU1## Accordingly, a spherical aberration of the optical system is corrected.

Abstract: A device including a polarizing beam splitter by which an incident luminous flux is split into a first luminous flux radiated onto a first photo sensor and a second luminous flux radiated onto a second photo sensor, and an adjusting mechanism provided for adjusting a position of one of the first and second luminous fluxes. The optical axis of the first luminous flux is coincident with that of the incident luminous flux. The optical axis of the second luminous flux is not parallel to the first luminous flux. By moving the beam splitter along the optical axis of the first luminous flux, the beam receiving position of the second photo sensor, onto which the second luminous flux is radiated, is changed.

Abstract: A zoom lens including at least two lens groups which move relative to one another in an optical axis direction to change the focal length of the zoom lens, wherein during the zooming operation in which the relative movement of the lens groups occurs to move the lens system in the telephoto direction, the lens group that is located closest to the image side of the zoom lens is advanced towards an object side, and a deflector which is provided closer to the image side than the lens group closest to the image side is externally driven to deflect a light flux of the zoom lens.

Abstract: An objective lens is corrected for spherical aberration at both an operating wavelength and a measurement wavelength, such that the amount of spherical aberration to develop at the operating wavelength is substantially equal to the amount of spherical aberration to develop at a measuring wavelength. The method of lens performance measurement then uses a light source emitting at a wavelength different from the operating wavelength.

Abstract: A collimating lens system comprises a chromatic aberration correction element and a converging lens which has both surfaces formed of a convex aspherical surface. The converging lens has no aberrations except chromatic aberration. The chromatic aberration correction element has small refractive power adapted to correct a chromatic aberration of the converging lens, and the element is constructed of positive and negative lenses cemented to each other. The positive lens and the negative lens have almost the same refractive index, and have different dispersion.

Abstract: An optical system of an optical disc apparatus is disclosed for converging and projecting a bundle of rays emitted from a light source onto an optical disc. The optical system includes a collimating lens which collimates the bundle of rays emitted from the light source, two anamorphic prisms for shaping the cross section of the collimated bundle of rays transmitted through the collimating lens, and an objective lens which converges the bundle of rays shaped by the anamorphic prisms onto the optical disc. At least one of the anamorphic prisms is detachably mounted to an immovable body portion of the optical system.

Abstract: An optical recording and reproducing apparatus is provided with a light source that emits a beam of light, a rotatable head including a deflector that deflects the beam in a predetermined direction and an objective lens group which forms an image of the beam on an optical recording medium. The rotatable head rotates about an optical axis of the beam which is incident upon the rotatable head. A movable lens group, provided in an optical path of the beam between the light source and the rotatable head, is movable in at least an optical axis direction.

Abstract: An image stabilizing apparatus is disclosed comprising an imaging optical system for forming an image of a subject onto an imaging surface. A deflector has first and second liquid prisms disposed with a movable transparent plate therebetween, and a controller changes vertex angles of the respective prisms by inclining the movable transparent plate in order to correct for a displacement of the image on the imaging surface.

Abstract: A telephoto zoom lens system is disclosed in which the wide-angle end starts with the middle telephoto range and in which focusing is done by means of a lighter focusing lens group than what is used in the method of focusing by advancing the front lens component and that only small aberrational variations occur even if zooming is done up to the closest focusing distance. The telephoto zoom lens system includes a front lens component and a rear lens component, said front lens component comprising a front lens group and having, in order from the object side, a positive first sub-group 1a and a positive second sub-group 1b and having an overall positive power.

Abstract: The optical disk apparatus of this invention is provided with a memory for memorizing a track offset signal corresponding to an angle of a galvanic mirror, or a photodetector having two pairs of photodetecting regions to detect different tracking error signals to each other, or two galvanic mirrors which are adjusted so as to prevent the track offset signal.

Abstract: A compound prism including a plurality of unit prisms which have reflective interfaces defined by outer and/or inner surfaces thereof and which are arranged so that light is reflected by an inner surface of the interface of one of the unit prisms and by an outer surface of the interface of another unit prism.

Abstract: A device in which an offset is added to a focusing error signal to control an objective lens and thereby reduce the generation of cross-talk when a beam spot that is converged on an optical disk crosses over a wall of a groove of a track of the disk. By adding the offset to the focusing error signal, the objective lens is moved out of focus with the disk. Thus, the shape of a beam spot formed on a photo sensor is changed from a circle to an ellipse. A condenser lens provided for forming the beam spot is moved along the optical axis thereof in such a manner that an output of a recorded signal of the disk is at a maximum value. As a result, the objective lens is brought into focus on the disk. Thereafter, the objective lens is focused on the disk in accordance with the focusing error signal to which the offset is added, while maintaining the beam spot in the shape of an ellipse.

Abstract: An optical axis adjusting apparatus is provided and includes a laser beam source, a beam shaping prism for shaping a laser beam of elliptical flux emitted from the laser beam source into a laser beam of circular flux, and an angle adjusting device which adjusts the angular direction of the outgoing laser beam emitted from the shaping prism.

Abstract: An optical axis adjusting apparatus is provided and includes a laser beam source, a beam shaping prism for shaping a laser beam of elliptical flux emitted from the laser beam source into a laser beam of circular flux, a parallel shift mechanism which shifts the light rays of the laser beam in a parallel fashion, and a rotation adjusting mechanism for rotatably adjusting a parallel plate.

Abstract: An optical system of an optical information recording/reproducing apparatus including a light source for emitting a generally parallel luminous flux; an objective optical system for converging the luminous flux emitted from the light source onto a medium; a beam splitter for splitting the luminous flux reflected by the medium from a light path directed to the light source and guiding the same to a light receiving system; a chromatic aberration correcting element having almost no power disposed between the objective lens and the beam splitter and adapted to correct a chromatic aberration of the objective lens; and means for independently actuating the objective lens at least in an optical axis direction thereof.

Abstract: In the magneto-optic recording/reproduction apparatus, a light beam from a semiconductor laser that can be used with two wavelengths, for recording and reproduction is converged by an objective lens on a magneto-optic disk, a predetermined offset is added to this focusing error signal by an offset adjusting circuit, and the objective lens is driven in the direction of the optical axis based on the focusing error signal to which an offset was added.

Abstract: An image stabilizing apparatus is disclosed comprising an imaging optical system for forming an image of a subject onto an imaging surface. A deflector has first and second liquid prisms disposed with a movable transparent plate therebetween, and a controller changes vertex angles of the respective prisms by inclining the movable transparent plate in order to correct for a displacement of the image on the imaging surface.

Abstract: An optical system of an optical disk apparatus having plural optical elements characterized in that the optical element having aberration which can counterbalance the wave front aberration of the whole optical system is disposed, or a direction of aberration of each existing optical element is adjusted in order to correct the wave front aberration.