Sharp Kabushiki Kaisha Corporation

Tomio Mashiyama

Nobuo Ogata

Yasuo Nakata

Yukio Watanabe

Tetsuo Ueyama

Osamu Miyazaki

Hiroshi Katayama

Kenji Ikeda

An optical pickup device has a semiconductor laser emitting light which is in turn branched via a diffraction grating into at least three beams of light including a main beam and two sub beams which are in turn condensed via an objective lens on an optical disk at a guide groove and reflected by the optical disk to provide three reflections of light which are in turn received by detectors, each divided into two regions, respectively, to generate a tracking error signal. The diffraction grating is divided into three regions including a first region, a second region and a third region located intermediate therebetween, each having a periodical structure out of phase, the periodical structure having grating grooves in a direction determined depending on the phase of the second region to incline relative to a direction perpendicular to the guide groove of the optical disk.

Optical pickup device recording and/or reproducing information on and/or from a plurality of kinds of recording media

A light radiated from a light source is divided by a grating into a main beam for detecting information signals and sub-beams for tracking, and thus irradiates a mini disk. The beams reflected by the mini disk are converged through a concave cylindrical mirror on a second light detector composed of adjacently disposed divided light receiving elements H (light receiving parts A and B) and J (light receiving parts C and D) and light receiving elements E1, F1, E2 and F2. The concave cylindrical mirror shapes the reflected beams so that spots of the reflected beams converged on the second light detector take elliptic shapes that are flattened in a direction in which the main beam for detecting the information signals and the sub-beams for tracking are arranged. In this manner, reliability of an optical head can be improved without increasing the size of the light receiving elements and without causing interference between a main spot and sub-spots.

Optical head

Growing community of inventors

Hiroshima, Japan

Tomio Mashiyama