Evaluation of interlaminar shear of laminate by 3D digital holography

基于三维数字全息的复合材料层间剪切强度评估

Optics and Lasers in Engineering, Volume 92, May 2017, Pages 57-62

Karray Mayssa, Poilane Christophe, Gargouri Mohamed, Picart Pascal

Abstract: In this paper, we propose a three-color holographic interferometer devoted to the 3D displacement field analysis of a composite material. The method in applied to analyze cracks during a short beam shear test. The tested materials are a glass/epoxy composite, a flax/carbon/epoxy composite and a flax/epoxy composite. Such an evaluation provides a pertinent parameter to detect premature cracks in the structure, long before it becomes visible on the real time stress/strain curve, or with a classical microscope. Moreover, the mechanical proprieties of flax/carbon/epoxy composite and flax/epoxy composite are compared.

Experimental study of the effects of the ratio of intensities of the reference and object waves on the performance of off-axis digital holography

参考波与物波强度比率对离轴数字全息特性影响的实验研究

Optik - International Journal for Light and Electron Optics, Volume 132, March 2017, Pages 274-283

Raul Castañeda, Diego Hincapie, Jorge Garcia-Sucerquia

Abstract:In this paper we present an experimental study of the effects of the ratio of the intensities of the reference and object waves on the performance off-axis digital holography operating in tight diffraction-limited regimen. The analysis is focused on the comparison of the information contained in the hologram before and after performing the spatial filtering of the zero diffraction order and the twin image. We show that in the Fourier transform of the recorded hologram the information of the object is preserved regardless the ratio of intensities of the object and reference waves. This fact allows the right spatial filtering of the +1 or −1 diffraction order leading to similar reconstructed images for holograms recorded with very different ratios of the intensities of the reference and object waves. The results show that the usual rule of thumb of 1:1 ratio for seeking maximum fringe contrast is not really required. Experimental results of a regular die are utilized for validating the claims.

Optimized setup for integral refractive index direct determination applying digital holographic microscopy by reflection and transmission

基于数字全息显微术反射与传输全息图的积分折射率指数直接测定优化技术

Optics Communications, Volume 387, 15 March 2017, Pages 252-256

M. Frómeta, G. Moreno, J. Ricardo, Y. Arias, M. Muramatsu, L.F. Gomes, G. Palácios, F. Palácios, H. Velázquez, J.L. Valin, L. Ramirez Q

Abstract:In this paper the integral refractive index of a microscopic sample was directly measured by applying Digital Holographic Microscopy (DHM) capturing transmission and reflection holograms simultaneously, of the same sample's region, using Mach-Zehnder and Michelson micro interferometers for transmission and reflection holograms capture and modeling the 3D sample in a medium of known refractive index image. The system was calibrated using standard polystyrene sphere immersed in water with known diameter and refractive index, and the method was applied for erythrocyte integral refractive index determination. The results are in accordance with predicted, the measurements error of the order of image in absolute values.

Digital in-line holography for the characterization of flowing particles in astigmatic optical systems

数字同轴全息在散光系统流粒特征化中的应用

Optics and Lasers in Engineering, Volume 88, January 2017, Pages 184-196

Matthias P.L. Sentis, Laurent Bruel, Sophie Charton, Fabrice R.A. Onofri, Fabrice Lamadie

Abstract:An extended Generalized Fresnel Transform (GFT) is proposed to account for the astigmatism introduced by optical elements described, in the paraxial approximation, with a ray transfer matrix analysis. Generalized impulse response and generalized Fresnel transfer function propagators as well as sampling conditions are derived to properly implement this transformation. As a test case, the near-field diffraction patterns and in-line holograms produced by droplets flowing in a tube with cylindrical interfaces have been simulated. A best fitting approach is introduced to retrieve, from the propagated holograms, the 3D position and size of the droplets. Several hologram focusing indicators based on the analysis of droplets focus region are also proposed to further improve the estimation of the droplets position along the optical axis. Numerical simulations and experimental results confirm the applicability and accuracy of the proposed methods.