| 摘要 |
PURPOSE:To decrease the number of parts in a magneto-optical detecting optical system and a servo optical system by arranging an optical element to have a diffracting surface, with which a reflected light beam from an optical information recording medium is specified on an optical path to pass through a polarizing beam splitter. CONSTITUTION:An incident light to be made incident on a diffracting surface 21 in a left side is separated into a diffracted light beam KL and a transmitted light beam TR by a diffraction grating 25. An incident light to be made incident on a diffracting surface 22 in a right side is also separated into a diffracted light KR and a transmitted light beam TR by a diffraction grating 25. When the incident light beam is in a condition (A) which is same as the emitting light beam of a semiconductor laser 1, the polarizing angle of the incoming light beams, which are mode incident on the diffraction gratings 24 and 25, keeps the condition of alpha=45 deg.. Then, the diffracted light beam KL and transmitted light beam TL in the left side and the diffracted light beam KR and transmitted light beam TR in the right side are wholly made equal. However, the polarizing angle alpha is changed according to the condition of a magneto-optical disk and a polarizing direction is changed for a case that a signal is '1' (a condition B) and a case that the signal is '0' (a condition C). Thus, a signal condition on the magneto-optical disk can be detected. On the other hand, a light beam to pass through a central emitting surface 23 can be used as a signal for servo. |
