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| Projects |
| Pulsed Digital Holography and Shearography |
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Prototype of the
measuring system with its compact pulsed ESPI camera (Dr.
Ettemeyer GmbH & Co., Neu-Ulm, Germany)
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Result obtained on a
vibrating car door
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Motivation
Pulsed holography is the only technique to provide
an instantaneous and complete map of the vibration amplitude on
any object without the necessity of time consuming scanning processes.
Therefore, this technique has been widely used, e.g. in automotive
design and engineering to investigate noise and vibration problems.
Adaptation of this technique is limited by the tedium and difficulty of
manual image analysis. To date, interferograms are recorded onto
holographic film, which has to be developed chemically, reconstructed in
an optical system, and converted into digital computer data by a camera
and framestore.
Description
The goal of this European research project is to replace this laborious
image recording and analysis technique by a reliable, fast and
industrial system. The images are recorded directly by a CCD camera and
fed into a computer. Owing to the software developed in this project,
the measurement result appears on the screen within a few seconds.
In the project consortium, aerospace, car and
nuclear industries define the end-user requirements. Universities and
research institutes take care of research and basic developments. The
commercial product is developed and marketed by a manufacturer of
optical measurement systems.
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Course of the project |
The project course shown above aims, on one hand,
at ensuring that the project goals are reached, on the other hand, at
chosing the most adequate techniques by parallel development and
comparison of different ideas.
The project goal of ETH is the adaption of the so-called "direct
shearography" to the application of a pulsed laser and a CCD-camera
for quantitative measurements. Such a system allows for dynamic
measurements in an environment which is affected by vibrations and
noise, where conventional methods would fail. Apart from this main issue
we participate in different development tasks, using our know-how in
optical metrology, image processing, mechanical modelling, computation,
and product design.
Current state:
In May 98, Dr. Ettemeyer GmbH & Co. demonstrated the measuring
system prototype. Preliminary tests were performed on a car door excited
by a shaker at various frequencies. A prototype, capable of making
simultaneous three dimensional measurements (3D system), is expected to
be ready in October 98. In the following months, software integration
and verification of the prototype will be priority tasks.
Partners
Related Publications
 | G. Pedrini, H. J. Tiziani, "Digital
double-pulse holographic interferometry using Fresnel and image
plane holograms", Measurement, Vol. 15 (1995), No. 4, pp. 251 -
260
| G. Pedrini, H. J. Tiziani, "Double
Pulse-Electronic Speckle Interferometry", VDI Berichte Nr.
1118, IMEKO-Symposium: Laser Metrology for precision measurement and
inspection in industry, March 21 - 22 1994, Heidelberg, pp. 57 - 62
| O. Petillon, "New Developments of Pulsed
Holography for Industrial Applications", 7th European
Conference on Non-destructive Testing, Copenhagen 26-29 May 1998 (Abstract) |
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Links
Contact
Stephan Waldner, Institut für Konstruktion und
Bauweisen, Tannenstrasse 3, 8092 Zürich, Switzerland
+41-1-632 7172 // waldner@ikb.mavt.ethz.ch
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