[OPTICAL REVIEW Vol. 1, No. 2 (1994) 296-298]

Profile Measurement by Projecting Two Gratings with Different Pitches

Satoshi KAKUNAI,1 Koichi IWATA2 and Tohru SAKAMOTO1

1Department of Mechanical Engineering, Faculty of Engineering, Himeji Institute of Technology, Himeji, 671-22 Japan 2Department of Mechanical Engineering, College of Engineering, University of Osaka Prefecture, Osaka, 593 Japan

(Accepted September 7, 1994)

A new method for measuring objects with steps is proposed in which two gratings with different pitches are projected on the object surface. The method is demonstrated with sinusoidal gratings made of laser interference fringes and also sinusoidal gratings formed by liquid crystal controlled by computer. An object with step height of 20 mm is measured with standard variation below 3%.

Key words : profile measurement, two gratings, step height, phase-shifting technique, interference fringe, liquid crystal grating, sinusoidal grating