| 摘要 |
The purpose of the present invention is to suppress the reduction of the amount of light received by a light reception unit. A displacement sensor (10) has polarizing beam splitter (23), which splits detection light and reflected detection light, and polarizing beam splitter (25), which splits light irradiated onto a variable focus mirror (27) and reflected light, and is provided with a Faraday rotator (24) and a quarter-wave plate (26) for changing the polarization of the detection light and the reflected detection light. The polarization angles of the two light beams split by the polarizing beam splitters (23, 25) are set to the P-polarized light and S-polarized light of the polarizing beam splitters by the Faraday rotator (24) and quarter-wave plate (26). As a result, the polarizing beam splitters (23, 25) can split two light beams and the reduction of the amount of light split by the polarizing beam splitters (23, 25) and received by the reception unit is suppressed. |
