FPGA Based Processing of Speckle Affected Self-Mixing Interferometric Signals

Abstract

Hardware implementation of a signal processing method based on Hilbert Transform is achieved in order to ensure robust detection of fringes contained in a Self-Mixing (SM) interferometric signal provided by a laser diode based SM sensor. The signal processing is based on obtaining the analytical signal from output optical power of LD by using Hilbert Transform. Then, this analytical signal provides instantaneous phase which is unaffected by the amplitude variations caused by speckle. This instantaneous phase is used for correct detection of fringes. Once SM fringes are correctly detected, then any phase unwrapping method can be used to retrieve the metric information contained in the SM signal. We implemented and tested our design on a Xilinx ZYBO Zynq 7000 development board. Results show that our design is capable of operating at 267 MHZ frequency, while consuming 15k slice registers and 12k LUTs. Our design draws 0.712 watts of onboard power.