Nobuyuki SHIGEI,¹ Toshiro MATSUMOTO,² Nobuaki TESHIMA,³ Akira ASANO³ and Shunsuke YOKOZEKI³

¹Department of Electrical Engineering and Computer Science, Osaka Prefectural College of Technology, 26-12, Saiwai-cho, Neyagawa, Osaka, 572 Japan, ²Department of Intelligent Mechanics, Faculty of Biology-Oriented Science and Technology, Kinki University, 930,Nishimitani, Uchita-cho, Naga-gun, Wakayama, 646-64 Japan, ³Department of Mechanical System Engineering, Faculty of Computer Science and Systems Engineering, KyushuInstitute of Technology, 680-4, Kawazu, Iizuka, Fukuoka, 820 Japan

(Accepted October 19, 1994)

It is reported that the first partial derivative of the phase distribution for a transparent object can be measured automatically by a personal computer with an image processor. The moire pattern is formed by superimposing the Fourier image distorted by the transparent object on the master grating. But if only the moire patterns are observed, it is not shown if the fringe order numbers increase or decrease. The fringe scanning method is presented to overcome the fringe order numbers. The four-step method is used to calculate the first partial derivative. By a simple experiment, the first partial derivative can be shown in the three dimensional graphics.

Key words : Talbot effect, moire fringe, automated Talbot interferometer, four-step method, fringe scanning, phase unwrapping, contour moire fringe