Noncontact 2-D In-Plane Speckle Velocimeter

In this paper, the authors present a noncontact 2-D speckle velocimeter, which is realized by means of a compact setup and based on an improved binary correlation algorithm for image processing. Starting from the results obtained in our previous work, where we demonstrated the feasibility of the method for the assessment of the surface velocity for one direction, we have extended the study to a 2-D velocity and displacement sensor by overcoming the previously encountered limits. In addition, the configuration is further simplified by introducing a low-coherence source and a simpler electronic circuit. Sensor performance is compared with that measured using a triangulation laser sensor. The main advantages of the proposed sensor, as compared with those of the traditional velocimeters, are the simplicity of the optical setup, the easily controlled device, and the small dimension of the sensor. The velocity of frame acquisition (15.6 frames/s) is the principal limiting factor of the sensor bandwidth (BW = 3.5 Hz). Such a noncontact optical sensor is suitable for small 2-D in-plane vibration measurements and allows one to overcome the limits of the classical Doppler velocimeters affected by speckle noise in this range of displacement.