Optical pickup using split beams impinging on different photo-detector

Abstract

An optical pickup device for producing information magnetically recorded on a recording medium includes a light source for generating a light beam polarized in a predetermined direction. An object lens is provided for focusing the light beam generated from the light source onto the recording medium. A beam splitter is arranged in an optical path extending from the light source to the recording medium, the beam splitter having a reflection plane for reflecting the light beam from the light source toward the recording medium. The beam splitter simultaneously causes the reflecting light from the recording medium to pass through the reflection plane to separate the reflected light beam from the light beam irradiated toward the recording medium. The polarization state of the reflecting light beam is modulated in accordance with the recorded information. The beam splitter splits the reflected light beam passed through the reflection plane into first and second light beams both of which are polarized in directions perpendicular to each other. The beam splitter has a bi-refractive property. First and second detection circuits are also provided for detecting the first and second light beams, respectively, and for providing first and second detection outputs respectively corresponding thereto. Circuitry is also provided for differentiating the detection outputs from the first and second detection circuits to provide information signals.