Hitachi, Ltd.

Shozo Saekusa

Hidehiko Kando

Isao Shimizu

Hiroshi Saito

Akira Ikuma

Seiichi Katoh

An art for reading information from an optical recording disk by means of a light beam emitted from a semiconductor laser, particularly an optical integrated circuit type apparatus which is improved to suppress fluctuation of the focal point of the beam caused by a change in the wavelength of the laser beam. The apparatus has a substrate, the semiconductor laser beam provided on one end of the substrate and an optical waveguide provided on one side of the substrate and capable of guiding the laser beam from the semiconductor laser. The apparatus further has a first diffraction grating provided on the waveguide and capable of diffracting the guided beam to the exterior of the waveguide and a second diffraction grating disposed at a position where it is capable of receiving the light beam diffracted by the first diffraction grating. According to this arrangement, when the wavelength of the laser beam is changed, the diffraction angle of the laser beam from the first diffraction grating is changed but this change does not cause substantial change in the diffraction angle of the second diffraction grating because the second diffraction grating diffracts the beam in such a direction as to cancel the above-mentioned change in the angle of diffraction of the laser beam from the first diffraction grating. In consequence, fluctuation of the diffraction angle of the laser beam irradiated by the second diffraction grating onto the recording surface of the optical recording disk is suppressed remarkably.

Optical information reading apparatus with waveguide and diffraction

An objective lens driving apparatus has a base provided with focusing permanent magnets and tracking permanent magnets, a supporting shaft mounted on the base, a lens holder for holding an objective lens at an extension thereof, with the lens holder being rotatably and slidably fitted onto the supporting shaft at a position of the center of gravity of the lens holder and being provided with focusing coils and tracking coils. A plurality of substantially identical elastic members are stretched between the base and the lens holder in a plane substantially perpendicular to the supporting shaft and in axisymmetrical relation with respect to Y-axis line joining the supporting shaft and the objective lens and X-axis line substantially perpendicular to the Y-axis. Each of the elastic members is a spring formed by a lead wire extending to the focusing and tracking coils. The springs are secured to the base through a fiscous elastic material.

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Ibaraki, Japan

Shozo Saekusa