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R. Paris, M. Melik-Merkumians, G. Schitter:
"Probabilistic absolute position sensor based on objective laser speckles, IEEE Transactions on Instrumentation and Measurement";
IEEE Transactions on Instrumentation and Measurement, 65 (2016), 5; 1188 - 1196.

This paper presents a vision-based probabilistic
absolute position sensor, which is able to operate on spacious
technical surfaces without the modification of the surface. Instead
of using artificial surface markings, the surface structure itself
is used to generate objective laser speckle patterns (OLSPs),
which are observable on most technical surfaces. This allows the
extraction of features on surfaces, which might be too smooth for
image processing under white light observation. In addition, the
uniqueness of the individually observed laser speckle patterns
enables a determination of the absolute position even after a
sudden power loss of the sensor system. Experiments confirm the
applicability of such OLSPs within a feature-based probabilistic
framework on a smooth stainless steel rod and compare the
results to images taken under white light illumination. The
proposed sensor system successfully recovers from unknown
initial states and measures the position with a peak-to-peak error
of 22.1 μm and an rms error of 5.6 μm over a measurement range
of 100 mm.

Optical position measurement, particle filters (PFs), position measurement, sensor systems, speckle.

http://dx.doi.org/10.1109/TIM.2016.2526741

https://publik.tuwien.ac.at/files/publik_251540.pdf