Measuring full displacement fields on scattering surfaces by a portable low-cost interferometer

The paper presents a device for measuring full displacement fields working on the principle of speckle interferometry. The proposed interferometer was designed with the aim of obtaining a lightweight self - contained device, easy to assemble with cheap and standard equipment. The investigated area is illuminated by three laser diodes emitting 50 mW at 660 nm , and observed by a B&W firewire CCD camera. The accuracy of the measurements is improved by means of a PZT actuator realized on purpose and driven by a control electronics able to provide a very accurate supply voltage. Furthermore by the control electronics it is possible to turn on and off the diodes and to c ontrol the single light intensity of each laser. The paper describes in details all the parts of the interferometer and the systems implemented for optimizing the working conditions of the device. Furthermore all the steps necessary for performing the meas urements are reported, and typical sets of experimental data are shown.