Photon-noise limited distance resolution of optical metrology methods

Peter Seitz

doi:10.1117/12.732040

18 June 2007 Photon-noise limited distance resolution of optical metrology methods

Peter Seitz

Proceedings Volume 6616, Optical Measurement Systems for Industrial Inspection V; 66160D (2007) https://doi.org/10.1117/12.732040
Event: Optical Metrology, 2007, Munich, Germany

Abstract

Optical metrology methods are classified into three fundamental techniques: Triangulation makes use of different positions of cameras and/or light projectors; interferometry employs standing light wave patterns; time-of-flight uses temporal light modulation. Using the unifying framework of linear shift-invariant system theory, it is shown that in all three cases the phase delay of a harmonic function must be determined. Since the precision of such phase measurements is photon noise limited, the distance resolution and the dynamic range are governed by the same functional relationship for the three fundamental optical metrology methods. This equation is derived under the assumption of Gaussian noise in the photogenerated charges in the photodetector; this assumption is a very valid one for almost all light sources, optical elements and photosensors. The equation for the precision of all types of optical distance measurement techniques contains the method's experimental parameters in a single factor, from which the optimum distance range of each of the three fundamental techniques can be deduced. For interferometry this range is 1 nm - 1 &mgr;m, for triangulation it is 1 &mgr;m - 10 m, and for time-of-flight ranging it is > 0.1 m, if visible or near infrared light is used.

Citation Download Citation

Peter Seitz "Photon-noise limited distance resolution of optical metrology methods", Proc. SPIE 6616, Optical Measurement Systems for Industrial Inspection V, 66160D (18 June 2007); https://doi.org/10.1117/12.732040

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