Real-time vibration amplitude and phase imaging with heterodyne interferometry and correlation image sensor

We propose a new out-of-plane vibration imaging technique for micro-structured solid-state devices such as MEMS (micro-electro mechanical systems) microphones or resonators. The technique is based on the longitudinally scanning optical interferometry and an integrated image sensor device which we call the correlation image sensor (CIS). The CIS is able to extract an arbitrary frequency, component from time-varying incident light and produce a complex correlation image including amplitude and phase ill addition to a conventional intensity image. In heterodyne interferometry of vibrating objects, the vibration information is encoded ill several frequency components generated by mutual modulation of longitudinal scan and vibration. In this paper, combination of newly, developed multi-channel CIS and the scanning heterodyne technique enable its to obtain the multiple frequency components simultaneously, and reconstruct the vibration amplitude and phase distributions in real-time. As all example, vibration modes of a MEMS acoustic sensor are shown to be reconstructed at, video rate. A theoretical possibility for the imaging of higher than GHz vibration combining other optical heterodyne techniques is also discussed.