Distance sensing using dynamic speckles formed by micro-electro-mechanical-systems deflector

We present a novel architecture of dynamic-speckles distance sensors with a micro-electro-mechanical system (MEMS) deflecting mirror for surface scanning. Since the MEMS mirror deflects the beam sinusoidally, the speed of scanning varies during the scan leading to sufficient variations in the signal frequency which is used to evaluate the distance to the object. Nevertheless, this feature does not affect the accuracy of range measurements when the distance is estimated from zero-crossing counts of the signal during a specially chosen time window within the scan. Experimental results indicate that a single 1 ms scan yields 70 μm accuracy of distance measurement. Averaging data from multiple scans of different surface areas during a 1-s measurement can provide approximately 2 mm of accuracy. Precision of the measurements can be further improved by optimization of the optical system. The compactness of the MEMS deflector and simplicity of the suggested signal processing provides a good basis for practical applications of this distance sensor.