Enabling Precise 2-D In-Plane Displacement Sensing With Low Latency for Motion Tracking Applications

This article presents a sensor designed for real-time measurements of 2-D in-plane displacements. Utilizing laser speckle, the sensor comprises a high-speed camera and an field-programmable gate array (FPGA) to process data with low latency. Based on a 2-D cross-correlation algorithm implemented on the FPGA in the frequency domain, the sample in-plane displacement is measured. The camera captures images at rates of up to 8200 frames/s, with the FPGA processing the acquired images with a latency of 121  $\mu $ s for a region of interest (ROI) of $8\times 8$ pixels. Experimental results demonstrate that the developed in-plane sensor effectively processes data in real-time, making it suitable for feedback control systems operating at frequencies up to several hundred hertz. The results also reveal a fundamental tradeoff between measurement range and frame rate/latency that can be exploited to match different application requirements.