A noninvasive optical method is described which allows the measurement of the vertical component of the instantaneous displacement of a surface at one or more points. The method has been used to study the motion of a passive compliant layer responding to the random forcing of a fully developed turbulent boundary layer. However, in principle, the measurement technique described here can be used equally well with any surface capable of scattering light and to which optical access can be gained. The technique relies on the use of electro-optic position-sensitive detectors; this type of transducer produces changes in current which are linearly proportional to the displacement of a spot of light imaged onto the active area of the detector. The system can resolve displacements as small as 2 ~tm for a point 1.8 mm in diameter; the final output signal of the system is found to be linear for displacements up to 200 gm, and the overall frequency response is from DC to greater than l kHz. As an example of the use of the system, results detailing measurements obtained at both one and two points simultaneously are presented.