Defocus measurement using speckle correlation

摘要

A technique using correlation fringes is presented to estimate the out-of-plane displacement of the image plane. The width of the fringe is estimated using autocorrelation of the Young's fringes and the visibility of the autocorrelation of these fringes are used as an estimator of the focusing error. This technique allows us to estimate focusing errors of the order of few tens of microns. [References: 4]