Spatial Resolution Enhancement of Fiber-Optic Scanning White-Light Interferometer by Use of a Vernier Principle

A Vernier principle is employed to improve the spatial resolution of a fiber-optic white-light interferometer to the accuracy of 0.2 (mu)m. The Vernier principle is implemented by combination of interference fringes itself and a virtual fringe that is generated by means of software tracing the scanning mirror. Two rulers are read with respect to each other. This design is insensitive to intensity fluctuation of the interference fringe. The applications, submicrometer estimation for the quadrature-locking selection and the tolerance of the relative measurement, demonstrate its effectiveness.