| 摘要 |
PURPOSE:To optically compensate the reduction in a detection signal even with the presence of optical axis deviation by setting a reflectance of a reflecting face of a polarized prism so that the luminous quantity of the reflected light from a recording medium and the luminous quantity of the reflected light from a roof mirror are made the same. CONSTITUTION:The reflectance of the reflecting face of the polarized prism 14 provided in a moving optical system 11 is set so that the luminous quantity of the reflected light 16 from the recording medium 10 and the luminous quantity of the reflected light 16 from the roof mirror 17 are made equal to each other to provide light transmissivity and one roof mirror 17 tilted in the same plane is provided behind the polarized prism 14. Thus, the compensation light of the same state reflected in the roof mirror 17 is fed back with respect to the conventional detection light reflected in the recording medium 10 and in receiving the detected light and the compensation light by photodetectors 18a-18d, a detection signal without effect of light axis deviation is obtained. Thus, neither light axis deviation detection means nor attitude correction means is needed and simple constitution is attained. |
