Real-time sensing of micrometer in-plane motion with a measurement rate of 25 kHz

Abstract

This paper presents a laser speckle-based line sensor for real-time measurements of translational in-plane displacements along one degree of freedom (DOF) at measurement rates of several ten kHz. The sensor architecture includes a high-speed CMOS line camera combined with an field-programmable gate array (FPGA), facilitating efficient data acquisition and processing with low latency. Laser-induced speckle serve as temporal surface markers for in-plane displacement measurements on non-structured surfaces. With cross-correlation and sub-pixel interpolation algorithms being implemented on an FPGA, measurement of in-plane displacement with single micrometer resolution is achieved. Experimental results demonstrate that the developed speckle sensor can effectively measure in-plane displacements at a measurement rate of 25 kHz over a range of 100 μm, and a resolution of 3.5 μm. With a latency of 81 μs, the ability to efficiently process data in real-time is successfully demonstrated, which enables the speckle sensor to be used for high-bandwidth feedback control loops.