Optical measurement apparatus utilizing total reflection

Abstract

In optical measurement utilizing total reflection, various types of measurement are selectively performed. The invention provides an optical measurement apparatus using total reflection, including a light source, a measurement optical system, and a light detector. The measurement optical system is an infinity-corrected positive lens formed of an optical member having a planar surface orthogonal to an optical axis of the measurement optical system at a front focal position. One side of the optical axis of the measurement optical system is used as a projection optical system for radiating measurement light onto a specimen, and another side is used as a photometric optical system for acquiring reflected light from the specimen. The light source is disposed at an entrance pupil position on the projection optical system side or at a position conjugate to the entrance pupil position and moves in an entrance pupil plane or in a plane conjugate to the entrance pupil position, along a straight line orthogonal to the optical axis, while a distance from the optical axis is detected. The light detector is disposed at an exit pupil position on the photometric optical system side or at a position conjugate to the exit pupil position. The optical-measurement apparatus comprises a light-source changing unit configured to change the position or shape of the light source.