Phase Modulation Homodyne Displacement Measuring Interferometer using Tunable Laser Diode as Light Source

—1^st Report : Development of Elementary Techniques—

Abstract

Since an ultra precision technology, e.g. a lithography, have been progressing rapidly, displacement measuring methods with resolution of sub-nanometer or less are required. Displacement measuring interferometers are widely utilized in precision engineering industries. However, they suffer from problems of an imperfect interpolation error of nanometer order and an air refractive index fluctuation. In this paper, we propose and discuss a displacement measurement method with no interpolation error by combining a phase modulation homodyne interferometer with a tunable laser diode and the null method. We also discuss the capability to measure the air refractive index fluctuation.