Use of specklegrams background terms for speckle photography combined with phase-shifting electronic speckle pattern interferometry

Abstract

Downloaded From: http://opticalengineering.spiedigitallibrary.org/ on 08/23/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspxAbstract. Electronic speckle pattern interferometry (ESPI) is combined with digital speckle photography (DSP) to measure out-of-plane deformation in the presence of large in-plane translation or rotation. ESPI is used to measure out-of-plane displacements smaller than the speckle diameter. In-plane displacements larger than the speckle size are obtained by DSP using artifacts images computed from the phase-stepped specklegrams. Previous works use the specklegram modulation for that purpose, but we show that this can lead to errors in the case of low modulation. In order to avoid this, a simple averaging of phase-stepped specklegrams allows obtaining the average irradiance, which contains information on the speckled object image. The latter can be used more efficiently than the modulation in DSP and is simpler to compute. We also perform a numerical simulation of specklegrams, which show that the use of background terms is much more stable against some error sources as compared to modulation. We show experimental evidence of this in various experiments combining out-of-plane ESPI measurements with in-plane translations or rotations obtained by our DSP method. The latter has been used efficiently to restore phase loss in out-of-plane ESPI measurements due to large in-plane displacements.

Fully automated extraction of the fringe skeletons in dynamic electronic speckle pattern interferometry using a U-Net convolutional neural network

“…Fully automated extraction of the fringe skeletons in dynamic electronic speckle pattern interferometry using a U-Net convolutional neural network 1 Introduction Electronic speckle pattern interferometry (ESPI) as a wellknown optical metrology technique has been extensively investigated and widely used in numerous fields. [1][2][3] It is well known that accurate extraction of phase terms is of fundamental importance for the successful application of ESPI. Compared with the static measurement, the extraction of phase terms in real-time and dynamic ESPI measurement is a more challenging problem.…”