Patent ID: 6639888
Filing Date: 2003-10-28
Classification: G11B

Abstract:
An optical information reading and recording device comprising;a semiconductor laser used as light source; a condensing lens for condensing a beam of light sent from the semiconductor laser so as to irradiate on an optical recording medium; a diffraction optical element for diffracting a signal of the optical recording medium, arranged on an optical path between the semiconductor laser and the condensing lens; in the diffraction optical element, the time when diffraction efficiency is maximum and transmission efficiency is minimum and the time when diffraction efficiency is minimum and transmission efficiency is maximum being determined by the direction of polarization of light; a signal detection optical system for detecting beams of light diffracted by the diffraction optical element, and a polarization light changeover element arranged between the semiconductor laser and the diffraction optical element in an optical axis, wherein a polarization direction of light is changed so that, in order to change servo light intensity between a forth path and a back path, the transmission efficiency of the diffraction optical element is maximum in the case of recording conducted to the recording medium by laser beams to increase the light intensity when recording, and the diffraction efficiency of the diffraction optical element is maximum to increase the optical intensity for servo detecting in the case of reading conducted on the recording medium by laser beams and the transmission efficiency is different from the diffraction efficiency.