ACCURATE MEASUREMENT OF SMALL DISPLACEMENT USING OPTICAL TECHNIQUES

Accurate measurement of small displacements is an important procedure in many areas of science and technology. A number of techniques are av ailable, but for a non-contact approach optical schemes offer signific ant advantages over other methods. A development with great potential for optical interferometric sensors and measurement systems is the tec hnique of white light interferometry. This approach utilizes a broadba nd light source and two interferometers coupled in series. One interfe rometer forms the measurement interferometer (the sensor) and the seco nd reconstructs the interferometric fringe pattern. The resolution of the measurement is then dictated by the resolution attainable in this second 'recovery' interferometer. Various techniques allow for sub-mic ron resolution over a large dynamic range. The technique is readily ap plicable to the accurate measurement of displacements and vibration.