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ESPI
Tue, 2012-04-24 16:46 - deepak_karanth
Anybody working on fringe analysis using ESPI (Electronic Speckle Pattern Interferometry)?
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Yes
We have developed device and sofware for determination of residual stresses using hole-drilling technique and ESPI. The software includes implementation of algorithms for fringe- speckle patterns processing.
ESPI
Its good to hear from you. We are working on dynamics using MicroMap 5010 (Commertially available device). But we are not happy with the software provided with it. Is there any possibility for us to develop software for such a set-up?
ESPI software
What do you want to measure and what conditions you have (inplane or out of plane deformation, frequency, area ..) ?
What do you want to improve in the software? Do you use phase-shifting or some other technique for fringe analysis?
ESPI software
We are doing out-of-plane measurement by vibrating the object. The frequency resolution is ~0.1Hz, phase-shifting interms of milliseconds and speckle averaging. We need to get atleast a resolution of 0.01Hz and clarity of fringes. We are using Optonor Micromap 5010 model.
ESPI hardware
I think you have hardware limitation. Maybe framerate is unsufficient.
I'm not familiar with Optonor software. If you have camera with 40 fps and you use a phase-shifting algorithm, you need about 0,1s to record images. During this time displacements of the tested objects must be less then lambda/10 (lambda is a laser wavelength).
You can try to make smaller ROI to increase framerate of images grabbing.
Another problem could be if inplane displacements are significantly bigger than out-of-plane displacements. This can lead to decreasing or vanishing of a fringe contrast.
You can record fringe patterns without phase-shifting algorithm to avoid averaging. It is requires manually calculation of fringes and computation of deformation using simple formula, but this is hard and time consuming job.
ESPI hardware
Did you mean with the 40fps camera and 0.1s ,the displacements must be less than lambda/10?