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Optical Engineering

Inspection of birefringent media by photoelasticity: from diffuse light polariscope to laser conoscopic technique
Author(s): Luigi Montalto; Nicola Paone; Daniele Rinaldi; Lorenzo Scalise
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Paper Abstract

A reliable and noninvasive measurement method for the inspection of naturally birefringent transparent media is presented in this paper. It allows us to achieve a spatially resolved analysis of the stress state of birefringent materials. The developed system is based on photoelasticity and exploits a controlled laser conoscopy technique and a scanning system to perform local measurements in the volume dimensions of the media, which can be displaced over a grid of points. The configuration of the proposed laser conoscopic system is presented, and a dedicated algorithm, designed to perform digital analysis of the fringe patterns, is also described. The design and the realization of the system are discussed, as well as the advantages of the proposed system over the classic diffuse light polariscope technique. The method has been experimentally validated through laboratory tests on birefringent samples with known induced stress. The system has demonstrated its sensitivity to stress and its capability to achieve a spatial resolution on the order of 0.1 mm to resolve stress gradients (uncertainty on the stress amplitude of ±0.1  MPa).

Paper Details

Date Published: 26 June 2015
PDF: 9 pages
Opt. Eng. 54(8) 081210 doi: 10.1117/1.OE.54.8.081210
Published in: Optical Engineering Volume 54, Issue 8
Show Author Affiliations
Luigi Montalto, Univ. Politecnica delle Marche (Italy)
Nicola Paone, Univ. Politecnica delle Marche (Italy)
Daniele Rinaldi, Univ. Politecnica delle Marche (Italy)
Istituto Nazionale di Fisica Nucleare (Italy)
Lorenzo Scalise, Univ. Politecnica delle Marche (Italy)

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