Self-mixing Sensor for Real-time Measurement of Harmonic and Arbitrary Displacements

A real-time self-mixing laser displacement sensor is presented that uses a fast consecutive-samples based unwrapping algorithm. The processing is achieved at a rate of 125KHz by an integrated micro-converter (ADuC7020) embedded on the SM sensor. Arbitrary and harmonic displacements have been measured in real-time with lambda /10 precision as compared with the reference built-in capacitive feedback sensor of the target, where. is the laser wavelength. The algorithm does not require any parameter estimation or huge memory and corrects possible false fringe detections. This results in a compact, integrated, precise and self-aligned laser sensor that costs less than 40 $.