Special Section on Digital Photoelasticity: Advancements and Applications

Inspection of birefringent media by photoelasticity: from diffuse light polariscope to laser conoscopic technique

[+] Author Affiliations
Luigi Montalto

Università Politecnica delle Marche, Dipartimento di Ingegneria Industriale e Scienze Matematiche, 12 Via Brecce Bianche, Ancona 60131, Italy

Università Politecnica delle Marche, Dipartimento di Scienze Ingegneria della Materia, dell’Ambiente ed Urbanistica, 12 Via Brecce Bianche, Ancona 60131, Italy

Nicola Paone, Lorenzo Scalise

Università Politecnica delle Marche, Dipartimento di Ingegneria Industriale e Scienze Matematiche, 12 Via Brecce Bianche, Ancona 60131, Italy

Daniele Rinaldi

Università Politecnica delle Marche, Dipartimento di Scienze Ingegneria della Materia, dell’Ambiente ed Urbanistica, 12 Via Brecce Bianche, Ancona 60131, Italy

Istituto Nazionale di Fisica Nucleare–Sezione di Perugia, Via A. Pascoli, Perugia 06123, Italy

Opt. Eng. 54(8), 081210 (Jun 26, 2015). doi:10.1117/1.OE.54.8.081210
History: Received February 5, 2015; Accepted June 2, 2015
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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 ±0.1MPa).

© 2015 Society of Photo-Optical Instrumentation Engineers

Citation

Luigi Montalto ; Nicola Paone ; Daniele Rinaldi and Lorenzo Scalise
"Inspection of birefringent media by photoelasticity: from diffuse light polariscope to laser conoscopic technique", Opt. Eng. 54(8), 081210 (Jun 26, 2015). ; http://dx.doi.org/10.1117/1.OE.54.8.081210


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