Polarizing different phases of interfered light used in a method and apparatus for measuring displacement of a specimen

Abstract

In measuring the displacement of an object using the phase-shifting light interference, since three beam splitters were used for generating the four phase-shifting optical paths, an interferometer was increased in size, whereby the application objects were limited. Also, to solve an essential problem that if there is a disturbance such as a temperature distribution, a humidity distribution, an air pressure distribution, a density distribution or an air flow change on the phase-shifting optical paths, a measurement error occurs, the four phase-shifting optical paths are produced spatially in parallel by combining a four division prism with a photonic crystal λ/4 element and a photonic crystal polarizing element arranged like an array, constructing a small light interference displacement sensor in the invention, whereby the application objects are expanded, and the microscopic displacement or surface roughness of the object can be measured at a resolution of sub nanometer or less and with high reproducibility without influence of the disturbance.