An optical method for generating a reference signal for an incremental displacement measurement system is proposed. We achieved this zero reference signal by comparing two speckle patterns arriving from two symmetric diffusers, which are used as natural random codes that are identical only when the reading head is located equidistantly between the diffusers. The comparison of the speckles is obtained either by interference, as in a Michelson interferometer, or by intensity correlations.
© 2003 Optical Society of America
(030.6140) Coherence and statistical optics : Speckle
(120.3940) Instrumentation, measurement, and metrology : Metrology
(120.4640) Instrumentation, measurement, and metrology : Optical instruments
Fernando Pérez-Quintián, José Alonso, Jesús Atencia, and Eusebio Bernabeu, "Zero Reference Signal for Displacement Measuring Systems by Use of Speckle," Appl. Opt. 42, 6797-6803 (2003)