ZhiQiang LIU, Katsuyuki OKADA, Toshio HONDA and Jumpei TSUJIUCHI

Department of Image Science, Chiba University, 1-33, Yayoi, Inage-ku, Chiba, 263 Japan

(Accepted October 27, 1994)

A new technique to measure the radius of a concave mirror is proposed, in which the radius is calculated from the difference of the two interferograms obtained before and after shifting the sample perpendicular to or along the optical axis. By comparison of these two shifting directions, it is shown that since the amount of shift can be measured accurately and the result is insensitive to the tilt during the shifting, better accuracy can be obtained by shifting the sample along the optical axis.

Key words : interferometry, differential, Newton gauge, zone plate interferometer, radius measurement