Simple Optical Vibration Sensor for Small Objects

A very simple and low-cost optical sensor for measuring vibrations of mechanically supported thin films and other small objects will be developed. Such measurements are useful in characterizing elastic materials properties. The sensor is based upon the so-called self-mixing effect in lasers, which enables the assembly of velocimeters containing nothing more than a diode laser, a lens, and a signla processor. The sensor combines high sensitivity and a very low parts count with a PC-based signal processor, to produce an instrument capable of measuring vibrations of specimens as small as tens of micrometers. It can easily be fitted to a microscope for real-time specimen observation during testing. A prototype velocity sensor has been assembled and tested using equipment purchased for less than $500. During Phase I, we propose to extend the demonstrated linear velocity sensing capability to sensing of vibrations of small objects, and to carry out a baseline design of a low-cost signal processor/display prototype. During Phase II, we will finalize the hardware design and develop a complete instrument for thin-film measurement and display. The end result of the proposed work is a highly capable sensor suitable for commercialization.