Strain Measurement Using Phase-shifting Digital Holography with Two Cameras

¹ Department of Opto-mechatronics, Faculty of Systems Engineering, Wakayama University, Sakaedani 930, Wakayama, Japan
² Graduate School of Systems Engineering, Wakayama University, Sakaedani 930, Wakayama, Japan
³ Moire Institute Inc., Hagurazaki 2-1-4-804, Izumisano, Osaka, Japan

^a e-mail: fujigaki@sys.wakayama-u.ac.jp

Abstract

Phase-shifting digital holography is a convenient method to measure displacement and strain distributions. Development of compact and conventional strain distribution measurement equipment for practical use is required for inspection of health monitoring and life lengthening of infrastructures such as steel bridges. In this paper, we propose an off-axis reconstruction method for displacement and strain distribution measurement with a phase-shifting digital holography. In the case of off-axis optical setup, the pitch of the fringe appearing on the image sensor becomes smaller than a pixel size. However, the phase-shifting digital hologram can be obtained even if the off-axis setup and effective results can be obtained using a Windowed-PSDHI. The principle and the experimental result of strain distribution measurement was performed with this method using two cameras.