Birefringence angle sensor for optical displacement measurements

A birefringence angle sensor (BAS) was proposed herein for application on a displacement measurement in a homodyne interferometer. The BAS was fabricated using a birefringence plate of potassium titanyl phosphate (KTP) immersed with glycerin liquid in a cylindrical glass container. The lateral displacement of a probe light induces a refractive angle change in the KTP through the curve interface in the glass container. According to the relationship between the displacement and the refracted angle change in the BAS, the measured phase is dependent on the angle change to further obtain actual displacements. Moreover, the flexible incident angles for a tunable sensitivity benefit the displacement measurement range determined by the proposed KTP-BAS.