Light-emitting/receiving combined unit and displacement sensors using the same

Abstract

The present invention provides a light emitting/receiving composite unit () for emitting and receiving lights, which includes a light source (), an optical splitting unit () for splitting returning lights to the composite unit () into a plurality of lights, a polarizing unit () for increasing and decreasing quantity of lights transmitted therefrom corresponding to polarization state of the returning lights, and an optical receiving unit () which has a plurality of photo-detecting elements (to) for detecting the lights transmitted through the polarizing unit (), which are unitedly integrated into one unit. Also, the present invention provides a displacement detection apparatus of grating interference type, which includes thus unitedly integrated composite unit (), and an external optical system of an objective unit having a reflection type diffraction grating RG, a reflecting unit (R, R) for reflecting lights from the composite unit () to the reflection type diffraction grating RG, a polarizing unit (WP, WP) for changing polarization state of diffracted lights from the reflection type diffraction grating RG, and a reflecting unit (R, R) for reflecting lights transmitted through the polarizing unit (WP, WP) to cause the reflected lights go backward.