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Proceedings Paper

ESPI with holographically stored waves and other innovative ESPI methods used for real-time monitoring of dynamic thermal deformations in a practical industrial environment
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Paper Abstract

Electronic speckle pattern interferometry (ESPI) is a rapidly developing optoelectronic method of nondestructive laser metrology supported with computer evaluations. It permits measurement of deformations in the micrometer and submicrometer ranges produced by an electrical signal, heating, mechanical stress or another load. Though the method seems very friendly for industrial checks it has several drawbacks which prevent its application in real industrial environment: complexity, bulkiness and high costs of optical setups, difficulties in aligning of the optical elements. There are problems in working outside the laboratory especially due to high sensitivity of ESPI devices against environmental vibrations and daylight. The method of ESPI with holographically stored waves was introduced by these authors in 1995. It permitted to avoid all drawbacks mentioned above and to build an elegant, portable ESPI device with 2 optical components only: a HOE and a plane mirror. The device works very well with different test specimens subjected to deformations and vibrations. It was found that the method and the device also suit well for quasi-real time monitoring of dynamic thermal deformations. Such a novel possibility of ESPI to monitor temporal development of deformations due to electrical heating of electronic components populating a printed circuit board (PCB) and to locate a component subjected to excessive heating is presented in this work for the first time. Temporal development of deformations of the same PCB were monitored in quasi-real time in other innovative ESPI devices also originating from our laboratory. These portable, compact devices utilize alternative physical principles for combining of object and reference ESPI waves and guiding them to the sensor of the CCD camera. Such novel devices also ensure proper acquisition and documentation of temporal development of deformations and dynamics of propagation of thermal waves. Vast experimental data properly illustrating the possibilities of the novel methods are presented.

Paper Details

Date Published: 21 September 1999
PDF: 12 pages
Proc. SPIE 3824, Optical Measurement Systems for Industrial Inspection, (21 September 1999); doi: 10.1117/12.364277
Show Author Affiliations
Valery Petrov, Fachhochschule Ulm (Germany)
Bernhard Lau, Fachhochschule Ulm (Germany)

Published in SPIE Proceedings Vol. 3824:
Optical Measurement Systems for Industrial Inspection
Malgorzata Kujawinska; Wolfgang Osten, Editor(s)

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