Real-Time Measurement of Nanometer Displacement Distribution by Integrated Phase-Shifting Method

Phase-shifting methods are advantageous for analyzing phases of fringe patterns obtained by interferometry. Conventional phase-shifting methods usually use three or four images obtained by phase-shifting. If only one camera is used for three or four images, the fringe images are recorded with phase-shifting disruption so that the brightness does not change during the camera exposure time. The stopping procedure obstructs the speed of the measurement system. We proposed a new method that takes four images for phase analysis without disrupting phase-shifting. The method is called the integrated phase-shifting method (IPSM), and is suitable for real-time phase analysis. In this method, four images are recorded continuously with full-exposure time during phase-shifting. In this paper, the development of a real-time phase analysis circuit using this theory and an application to nanometer-order displacement distribution measurement of a micro-accelerometer manufactured by micro-machining techniques are shown.