an apparatus and method for measuring the surface deformation or displacement in objects . in one embodiment the apparatus includes an interference pattern generator which projects an interference pattern onto a detector mounted to the surface which is to be measured . as the surface deforms , the detector moves and sweeps across the interference pattern . by noting the changes in the light intensity , the deformation or displacement in the surface at the detector may be determined . in another embodiment , both the detector and the interference pattern generator are located on the surface and as the surface deforms , the relative change in the surface at the detector and the relative deformation or displacement of the surface at the interference pattern generator may be determined . in another embodiment a plurality of detectors and interference pattern generators are positioned to map the deformation or displacement of the surface at many locations on the surface .