A system was designed to optically measure the physical motion induced by a microwave pulse on a rat eye lens immersed in saline. After consideration of several possible techniques, a Michelson interferometer using a HeNe laser and normal reflection from the lens surface was constructed. The system uses wavefronts matched to the curved lens surface, a vibrating reference mirror for calibration and signal discrimination, a sample chamber mechanically isolated from the microwave waveguide, and a fast photodetector and signal averager. A rotatable half‐wave plate and two polarizers were used to smoothly vary the intensity of the reference beam while maintaining the spatial integrity of its wavefronts. The system was able to measure motion down to 2 nm and performed successfully in the microwave pulse exposure experiments.