Olympus Optical Company, Ltd.

Toru Musha

Hiroshi Miyajima

Akihiko Yoshizawa

Hiroyuki Imabayashi

Takeshi Yamazaki

Kenichi Ito

Kenichi Oinoue

Shunpei Tanaka

Takashi Hamaoka

An optical pick-up head for reading writing information from on a magneto-optical record medium including a semiconductor laser, a multi-image plane parallel plate for separating an incident light beam emitted by the semiconductor laser from a return light beam reflected by the optical record medium and dividing the return beam transmitted through and refracted by the multi-image plane parallel plate into a plurality of return light beams, and a signal detecting photodetector receiving a plurality of return light beams, wherein the multi-image plane parallel plate is formed by first and second prisms made of birefringent material and is arranged such that major and minor axes of astigmatism introduced by the plane parallel plate are inclined by 45.degree. with respect to an information track. An optic axis of the first prism is set such that the return beam is separated into ordinary and extraordinary light beams having identical intensities and an optic axis of the second prism is rotated with respect to the optic axis of the first prism. The optical elements are positioned and mounted on a mounting substrate having guide walls formed by a photolithography.

Optical pick-up head and integrated type optical unit for use in optical

A focus error detecting apparatus in which a light emitting and receiving element including a light emitting portion and light receiving portions all of which are formed in a common semiconductor substrate, a hologram element diffracts a light beam reflected by an object to generate plus and minus first-order diffraction light beams and to introduce an astigmatism into the plus and minus first-order diffraction light beams such that shapes of spots of the diffraction light beams formed on the light receiving portions of the light emitting and receiving element vary into substantially reverse directions to each other, and a focusing condition is detected in accordance with outputs of the light receiving portions. Therefore, in this apparatus, positioning adjustment of the light receiving portions with respect to the light emitting portion is not necessary, and thus a number of the adjusting process can be remarkably decreased and the cost for manufacturing the apparatus can be reduced. Furthermore, the focusing condition can be detected with high accuracy.

Focus error detecting apparatus

A tracking error of a light spot focused on an optical record disc by means of an objective lens with respect to an information track recorded on the disc is detected by processing outputs from a light detector arranged in a far field of the track and having four light receiving regions on which a light reflected by the disc is incident. A tracking error signal of a differential detection system, i.e. a difference between two sums of outputs from two pairs of two regions aligned in a direction tangential to the track is derived, and a push-pull signal, i.e. a difference between two sums of outputs of two pairs of two light receiving regions aligned in a radial direction is also obtained. Zero crossings of the push-pull signal are detected to produce sampling pulses and the tracking error signal of differential system is sampled by the sampling pulses to derive a tracking error signal which is substantially free from disturbance due to a possible shift of the light impinging upon the light detector with respect to the optical axis of objective lens.

Method and apparatus for detecting tracking error

An apparatus for driving an objective lens which projects a light spot onto an information track or tracks recorded spirally or concentrically on a disc-shaped record medium to read out information, in order to correct a tracking error, comprises a pair of leaf springs for supporting the objective lens movably in a tracking direction perpendicular to the optical axis of objective lens as well as to the track direction, a movable member made of magnetic material and being coupled with the movable member to move in the tracking direction in conjunction with the objective lens, first and second magnetic members made of magnetic material and arranged in such a manner that the movable member is interposed between the first and second magnetic members at their one end portions via gaps, a third magnetic member made of magnetic material for coupling the first and second magnetic members at their other end portions, first and second coils wound on the one end portions of the first and second magnetic members, respectively, and magnetic flux producing means such as a permanent magnet and an electromagnet for producing a constant magnetic flux through the first, second and third magnetic members and the movable member. The gaps may be filled with magnetic fluids.

Apparatus for driving objective lens in tracking direction

An objective lens driving device useable in an information reading-out apparatus for projecting a light spot onto a record medium which has been spirally or concentrically recorded with one or more information tracks and for reading-out the information, which drives the objective lens in a direction perpendicular to its optical axis and the information track, thereby correcting relative positional error, i.e. tracking error, between the information track and the light spot. It comprises at least one set of objective lens driving means, each set including a movable member movable together with the objective lens, a coil wound around a stationary yoke, and an objective lens supporting means for movably supporting the objective lens in a direction perpendicular to the optical axis of the objective lens and information track, said coil being supplied with an electric current corresponding to a tracking error signal representing the relative positional error so as to displace the movable member and objective lens and information track and thereby to correct the tracking error.

Objective lens driving device for tracking and focus corrections

In a method for detecting a focussing error signal of an objective lens with respect to a video disc on which a light beam emitted from a laser light source is to be focussed as a light spot by the objective lens, a light flux reflected by the video disc is made incident upon a detection prism surface which is set substantially at a critical angle with respect to a central light ray in the reflected light flux, and two light fluxes which situate on respective sides of a boundary plane including the central light ray and perpendicular to a plane of incidence, and are reflected by the reflection surface are separately received by two light receiving regions which are divided along a boundary plane including the central light ray reflected by the reflection surface and perpendicular to the plane of incidence. The focussing error signal is derived as a difference between output signals from the two light receiving regions.

Method and apparatus for detecting focussing error signal of objective

An objective lens driving device for driving an objective lens and correcting a relative positional error, i.e. a tracking error between one or more information tracks recorded spirally or concentrically on a disc-shaped record medium and a light spot projected onto the record medium by means of the objective lens, comprising a supporting means for movably supporting the objective lens or its holding means in a direction perpendicular to an optical axis of the objective lens as well as the information track, first and second magnetic members arranged at both sides of the objective lens or its holding means as viewed in a direction perpendicular to the moving direction of the objective lens or its holding means and made integral therewith, first, second, third and fourth yokes each including one portion opposed through an air gap to one of the two ends of the magnetic member, first, second, third and fourth coils each wound around that portion of the yoke which is opposed to the magnetic member, and a magnetic field generation means for producing a closed loop of magnetic field passing through the first, second, third and fourth yokes as well as the first and second magnetic members.

Objective lens driving device

An optical information reading-out apparatus which makes use of a focusing and tracking mechanism including first and second leaf springs for connecting an objective lens supporting body to first and second supporting members, respectively, and adapted to be moved in tracking and focusing directions when subjected to a magnetic force or to the action of piezoelectric elements.

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Hachioji, Japan

Toru Musha