FPGA Implementation of a Digital Sequential Phase-Shift Stroboscope for In-Plane Vibration Measurements With Subpixel Accuracy

This paper describes a sequential phase-shift stroboscope and a subpixel imaging system that is able to measure with high resolution weak in-plane harmonic motions, such as those of microelectromechanical systems (MEMS). The synchronization of both MEMS stimulus and light strobe can be obtained by either using the camera output frame signal or driving the external trigger of the camera, depending on the operation principle of the camera. Experimental results concern a small silicon cantilever resonator excited in its first and second vibration modes and a quartz tuning fork. Two optical configurations have been developed. The first one is based on the use of a macroobjective for large fields of view with micrometer resolution displacement measurement, and the second is based on an optical microscope for weak amplitude vibration measurements with a resolution down to a few nanometers. The whole logic unit of the stroboscopic signal generator is implemented into a low-cost field-programmable gate array, thus offering high flexibility.