We discuss the uncertainty limit in distance sensing by laser triangulation. The uncertainty in distance measurement of laser triangulation sensors and other coherent sensors is limited by speckle noise. Speckle arises because of the coherent illumination in combination with rough surfaces. A minimum limit on the distance uncertainty is derived through speckle statistics. This uncertainty is a function of wavelength, observation aperture, and speckle contrast in the spot image. Surprisingly, it is the same distance uncertainty that we obtained from a single-photon experiment and from Heisenberg’s uncertainty principle. Experiments confirm the theory. An uncertainty principle connecting lateral resolution and distance uncertainty is introduced. Design criteria for a sensor with minimum distance uncertainty are determined: small temporal coherence, small spatial coherence, a large observation aperture.
© 1994 Optical Society of America
Original Manuscript: October 26, 1992
Revised Manuscript: May 11, 1993
Published: March 1, 1994
Rainer G. Dorsch, Gerd Häusler, and Jürgen M. Herrmann, "Laser triangulation: fundamental uncertainty in distance measurement," Appl. Opt. 33, 1306-1314 (1994)