[OPTICAL REVIEW Vol. 5, No. 3 (1998) 191-195]

Position Sensing Grating Interferometer for a Specular Object

Masayuki MINO

Faculty of Engineering, Tokushima Bunri University, Shido-cho, Okawa-gun, Kagawa, 769-2193 Japan

(Received September 9, 1997; Accepted March 31, 1998)

A position sensing interferometer is described which is able to sense the position of a specular object from a normal distance. The interferometer consists basically of a diffraction grating, a focusing lens and two plane mirrors. The grating acts as a tool to divide the incident beam and also to combine the reflected beams from an object so that they interfere with each other. An experiment was carried out to verify the principle. Interference fringe patterns caused by variation in the object position were obtained. The sensitivity obtained theoretically was confirmed by measuring the width of the fringes. As a result of theoretical comparison with conventional techniques, it was determined that this interferometric method has the advantage of the high sensitivity and the wide dynamic range being compatible with each other. The setting for sensing is simple and the analysis of the fringe patterns is easy.

Key words : interferometer, diffraction grating, position sensing, focus, profile measurement