PERFORMANCE OF A 2D SPECKLE DISPLACEMENT SENSOR WITH VARIOUS MEASUREMENT SURFACES

摘要

This paper discusses the performance of a 2 dimensional (2D) speckle displacement sensor used with measurement surfaces of various materials and characteristics. The sensor operates by projecting a collimated laser beam onto an optically rough measurement surface. Images of the resulting speckle pattern are acquired via a simple optical system and CMOS sensor. As the underlying measurement surface (and associated speckle pattern) displaces in 2D, measurement images are numerically correlated with an initial reference image to determine the 2D displacement in the plane of the measurement surface. The sensor in its present form is capable of sub-nanometerposition noise, X-Y measurements over a 250μm × 250μm measurement range, with update rates of 20-140Hz. The advantage of using a speckle sensor is that the sensor does not need a calibrated scale; the displacement of any optically rough surface may be measured. There are many possible applications for this technology, including but not limited to: monitoring stage drift, nanometer level positioning, monitoring metrology frame deflections, characterizing stage orthogonality/straightness, and (because of absolute measurements) mounting repeatability of measurement target.