Abstract: An objective lens having a doublet structure and a number of apertures of 0.7 or more and an optical pickup apparatus having the objective lens to be adaptable to a optical recording medium having a high information recording density, the objective lens being structured such that at least one side is formed into a aspheric surface and the lens elements are made of low-diffusion glass having an Abbe's number of 40 or greater.

Abstract: This invention intends to provide an optical pickup of which it is possible to limit aberrations within a tolerable limit without incorporating a special device for that purpose even if errors arise in thickness of component lenses of a two-lens system constituting an element of the pickup. This object is achieved by providing an optical pickup incorporating a two-lens system with first and second lenses 13 and 14 being arranged in the following manner: the first lens has a first surface 15 to receive a laser beam radiated from a semiconductor laser and a second surface 16 to direct the laser beam transmitted from the first surface 15 towards the second lens 14; the second lens 14 has a third surface 17 to receive the light flux transmitted from the second surface 16 and a fourth surface 18 to direct the light flux transmitted from the third surface 17 towards an optical disc placed opposite thereto; and the first and fourth surfaces are used as a reference during positioning.

Abstract: An optical disc recording/reproduction apparatus for recording and/or reproducing a data by applying a beam from an optical head unit through a substrate onto/from a recording layer of the optical disc through, wherein the substrate of the optical disc is 0.3 mm or below; the optical head unit comprises: an objective lens for converging an incident beam and emitting the beam toward the optical disc; a forward lens for converging the beam introduced through the objective lens and applying the beam to the optical disc; a lens holder where the objective lens and the forward lens are fixed; and an actuator for driving the objective lens and the forward lens as a unitary block and controlling at least focusing, the objective lens and the forward lens having a total numerical aperture of 0.8 or above.

Abstract: An optical recording medium recording and reproducing apparatus for recording information on an optical recording medium and/or reproducing information therefrom by irradiating the optical recording medium with laser light by the use of a two-group objective lens composed of at least first and second lenses. This apparatus is provided with: a light source for emitting laser light; a first lens for converging laser light emitted from the light source; a second lens interposed between the first lens and the optical recording medium; a detecting unit for detecting a kind of the recording medium; and a movement unit for changing the distance in the direction of an optical axis between the first and second lenses by causing a relative movement between the first and second lenses. Further, the distance between the first and second lenses is changed by the movement unit, which causes the second lens to move, according to a result of a detection, which is performed by the detecting unit.

Abstract: A method for designing an objective lens apparatus formed by at least two lenses, a first lens and a second lens, which includes the steps of: measuring aberration which occurs when a light beam is converged by the first lens; setting the first lens is set such that the aberration occurring in the first lens satisfies Marechal's criterion, in accordance with the measurement results; measuring aberration which occurs when a light beam is converged by the first lens and the second lens; and setting the second lens such that the aberrations occurring in the first lens and the second lens satisfy Marechal's criterion, in accordance with the measurement results. Accordingly, an objective lens apparatus with a small aberration and a large numerical aperture NA can be designed by this method.

Abstract: An optical pickup device for condensing the light from a light source on a signal recording surface of an optical recording medium, such as an optical disc. A semi-spherical lens of the optical pickup device has a surface 9b facing an optical disc 20 and has a pre-set refractive index. The optical pickup device also has a slider 12 adapted for securing the lens 9 and for being in sliding contact with an optical disc 20, and a spring plate 13 adapted for thrusting and supporting the slider in sliding contact with the optical disc 20. With the optical pickup device, high density reproduction may be realized, while the tolerance value for warping during disc molding or the tolerance value for warping due to moisture absorption may be increased. In addition, the production yield and the degree of freedom in selecting the disc materials may be improved.

Abstract: An optical pickup device for condensing the light from a light source on a signal recording surface of an optical recording medium, such as an optical disc. A semi-spherical lens of the optical pickup device has a surface 9b facing an optical disc 20 and has a pre-set refractive index. The optical pickup device also has a slider 12 adapted for securing the lens 9 and for being in sliding contact with an optical disc 20, and a spring plate 13 adapted for thrusting and supporting the slider in sliding contact with the optical disc 20. With the optical pickup device, high density reproduction may be realized, while the tolerance value for warping during disc molding or the tolerance value for warping due to moisture absorption may be increased. In addition, the production yield and the degree of freedom in selecting the disc materials may be improved.

Abstract: An optical pickup apparatus is constructed of an objective lens for condensing a light beam emitted from a light source toward an optical recording medium, and a convex lens arranged between the optical recording medium and the objective lens in which a surface thereof upon which the luminous flux projected from the objective lens is incident is a convex spherical surface with a radius of curvature which is a predetermined value, and another surface thereof which is located near and opposite to a surface portion of the optical recording medium which is a plane. With this arrangement, a tolerance with respect to decentering of the convex lens in connection with the optical axis of the objective lens is increased, so that an occurrence of aberration is reduced.

Abstract: There is provided an optical pick-up device capable of eliminating a spherical aberration due to a thickness error of an optical disc. The optical pick-up device includes a convex lens having a flat surface opposed to a surface of an optical recording medium, and having a predetermined refractive index, and an objective lens disposed such that the convex lens is interposed between said optical recording medium and the objective lens. A position-detecting means detects a position relation between the light-incident surface of the optical recording medium and the flat surface of the convex lens, based on first and second detection signals.

Abstract: A method for the optical axis of an optical pickup apparatus includes the step of adjusting the optical axis of a beam expander for enlarging the diameter of a light beam outgoing from a laser light beam radiating device into coincidence with the optical axis of the light beam radiated from the laser light beam radiating device. The laser light beam radiating device includes a non-linear optical crystal element and is adapted for radiating a second harmonic laser light beam. The method also includes the step of mounting the beam expander having adjusted its optical axis, and a step of adjusting, with the beam expander mounted on the laser light radiating device, the optical axis of an optical system converging the laser light beam radiated from the laser light beam radiating device so that the optical axis is brought into coincidence with the optical axis of the laser beam radiated from the laser light beam radiating device.

Abstract: The present invention is directed to a magneto-optical recording apparatus in which a rotating device for the recording magnet is composed of a drive coil and a yoke. Therefore, the efficiency of the rotating device can be increased to thereby reduce the power consumption. Also, since the recording magnet is attracted to the yoke, the settle position of the recording magnet can be stabilized satisfactorily.