Monitoring modal shape of miniaturized dynamic structures via laser triangulation and stroboscopy

Abstract

We present a simple, low-cost and effective method to monitor mode-shapes of dynamic structures, based on laser triangulation. Through the smart adjustment of the camera view angle, we were able to acquire the mode-shapes on two orthogonal planes, without the need to change the placement of neither the device-under-test, nor the illumination or detection optics. The presented technique was demonstrated on two different miniaturized dynamic structures for laser-scanned optical imaging both having ~ 1 cm² floor area; a 3D-printed electromagnetically-actuated laser scanner, and an orthogonally placed double piezoelectric cantilever structure for fiber scanning. Experimental findings reveal a good match with the observations made on finite-element simulations. Based on its cost advantage (only requiring 1–2 laser, a cylindrical lens, and a standard CMOS camera) and simplicity (both setup and software), the presented method is particularly appealing to characterize MEMS and similar dynamic structures on multiple planes, performing periodic motion. Moreover, the method is scalable to smaller structures having ~ 1 mm² floor area, and higher modal frequencies.