Measurement of in-plane motions and rotations using a simple electronic speckle pattern interferometer

We describe the construction and operation of a simple electronic speckle pattern interferometer which is sensitive to in-plane motions and rotations. The interferometer is extremely simple and easy to use. It uses a commercial digital still camera for image acquisition, and a personal computer for image storage and analysis. The interferometer was used to measure very small in-plane rotations of a rough surface, and the results were found to be in good agreement with the expected values. We propose to use this system as an instrument for the measurement of small-angle rotations.