Non-linear joint transform correlator for micro-displacement measurement using speckle patterns

Valdivieso González, Luis G.; Guerrero Bermúdez, Jáder E.; Rodríguez, Eduardo Tepichín
September 2013
Revista Facultad de Ingenieria Universidad de Antioquia;sep2013, Issue 68, p20
Academic Journal
This work presents a procedure for measuring displacements of tens micrometer, in one and two dimensions, based on the correlation between two speckle patterns. For this purpose, two objective speckle patterns are recorded by a digital camera one before and one after the object has been moved and placed in the input plane of nonlinear joint transform correlator. Nonlinear transformation of the joint power spectrum allows a sharper correlation peak and a high signal to noise ratio. The autocorrelation peak coordinates of the first pattern are set as a reference for measuring shifts of the successive cross-correlation peak. One criterion for reliable measure is proposed. Results related with different distances sample-sensor and illuminating wavelengths at 632.8 nm and 543.5 nm are presented.


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