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

This paper presents a sensor designed for real-time measurements of two-dimensional 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 2D 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 8,200 frames per second, with the FPGA processing the acquired images with a latency of 121 μs for a region of interest of 8 x 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 Hz. The results also reveal a fundamental trade-off between measurement range and frame rate/latency that can be exploited to match different application requirements.