SBIR-STTR Award

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 signalV 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 1, 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 2, we will finalize the hardware design and develop a complete instrument for thin-film X measurement and display. The end result of the proposed work is a highly capable sensor suitable for commercialization.Commercial Applications:Compact, rugged, reliable, and low-cost vibration sensors are expected to find uses in fault detection, vibration mode surveys, and :wear monitoring/detection of shafts, gears, and bearings. The proposed sensor is expected to find uses in many areas where ; measurements are limited due to a high instrumentation acquisition cost at present.

In Phase 1 we demonstrated that highly sensitive vibration measurements can be carried out using an extremely simple optical technique based upon a semiconductor diode laser. Vibrations and resonances were sensed over the frequency range from 500 Hz to 154 kHz, with vibration amplitudes as small as 0.2 nanometers. Based upon the highly successful Phase 1 work, we propose to develop a full-scale prototype vibration sensor in Phase 2. The primary goal of the system is measurement and characterization of vibrations in the 500 Hz - 200 kHz frequency range, with vibration amplitudes in the range of a few picometer to several hundred nm. This system is targeted as a stand-alone sensor primarily for characterizing the mechanical frequency spectrum of small objects. The system can easily be attached to commercial microscopes. Hardware and software necessary for performing measurements at lower frequencies and with larger vibration amplitudes will also be identified and implemented. The simplicity of the technique points to sensor systems with an order of magnitude less cost than current optical systems. Further development of the technique beyond Phase 2 will enable mass production of vibration sensors at potential unit costs on the order of $100. Commercial applications:A number of applications of the proposed self-contained vibration sensor exist. In the short term these include characterization of small objects, such as audio equipment, and hearing aids. In the longer term very low cost devices can be embedded into machinery for wear indicators and other "health" monitoring purposes.