Advanced achievements in holographic and speckle interferometry, physics of solid-state lasers, digital recording and image processing have created real precondistions for a rising of holographic methods of diagnostics to qualitatively new level. In the present work the general concept of universal holographic system for nondestructive researches in industrial environment is considered and results of tests of some units of this equipment are presented.
Experimental aspects of frequency-bounded vibration investigations were observed. Experimental set-up for stroboscopic holographic investigation of bounded vibration by using a continue-wave laser was described. Experimental investigations have shown that stroboscopic technique allows to separate different mode-shapes vibrating simultaneously. Pulse laser and digital holographic technique was applied to frequency-bounded vibrational investigations as well. The results of digital evaluations of separated mode-shapes were presented.
Theoretical and experimental aspects of frequency-bounded vibration investigations were discussed. It was shown that stroboscopic holography has an advantage in comparison with other ones. Digital calculation shows that the result depends on accuracy of setting the phases of strobe pulses.
The applying of stroboscopic methods in optical holographic measurements is limited due to the influence of quality of holographic arrangement on the accuracy of results. Parasitical interferometric fringes as a result of pulse duration or phase synchronization instability may be presented on a hologram and, such fringes have no relationship to real displacement or deformation. It creates a lot of troubles for researchers and, finally leads to refuse of using the stroboscopic technique. However, the troubles may be successfully overcome as if we analyze all kinds of influences on the quality of stroboscopic interferogram. This paper reports about the influence of pulse duration and phase instability. The presented results allow to realize correct stroboscopic holographic measurement. The problem of quality of applied arrangement has been discussed as well.
Victor Vorobyev, Oleg Vitrik, Mikhail Gusev, Murat Bukayev, Alexander Malov, Igor Alexeenko, Elena Kuzmina, Nataly Soboleva, Yana Vitrik, Yury Vigovsky, Vasily Levit, Nataly Qutyakova, Sergey Malov, Serge Antonyuk
The results of the mathematical calculations for the tooth bridge prostheses are discussed. Holographic interferometry with double exposition is used for verification of the model calculation results.
Theoretical and experimental aspects of frequency-bounded vibration investigations were observed. It was shown, that stroboscopic holography has an advantage in comparison with other ones. Digital calculation shows that the result depends on accuracy of setting the phases of stobe pulses. Thus, it is necessary to apply very precise driver for the creation of laser pulses in needed phases. Experimetnal set-up for stroboscopic holographic investigation of obunded vibration by using continue-wave laser was described. Experimental investigations have shown that stroboscopic technique allows to separate different mode-shapes vibrating simultaneously. Pulse laser and digital holographic technique was applied to frequency-bounded vibrational investigations as well. The results of digital evaluations of separated mode-shapes were presented.
A system based on digital holographic interferometry in combination with a rigid and a flexible endoscope is described. A Q-switched pulsed laser is used. Two digital holograms of the test object, corresponding to the two laser pulses, are captured at separate video frames of the CCD-camera, transferred in a frame grabber and further processed in a PC. If during the interval between the two laser pulses (usually in the range of 5-600 ?s) the object undergoes a vibration, a fringe pattern will result from the difference between the two holograms. This fringe pattern has the information needed to quantitatively evaluate the vibration. Two compact systems (using rigid and flexible endoscopes) have been developed to be used for many applications, both mechanical and biological, where measurements need to be performed at "hidden" surfaces or inside more or less closed objects. The quality of the results obtained by using mechanical objects is usually better, this can be easily explained by the fact that a biological surface is much more complex, in particular some parts reflects well the light and some other absorb it. Experimental results are presented.
In the introduced paper on an example of the mobile pulse holographic set-ups, designed by authors and inserted to the large industrial enterprises of Russia the requirements to the basic units of holographic measurement complex, intended for vibration analysis of large-scale objects under out-of- laboratory conditions are analyzing. It is shown the quality of obtained measurement information depends not only from coherent properties of laser and quality of interferometer, but also from the quality a control system of laser radiation. In particular, for obtaining the reliable and reproduced results of analysis of actual vibration processes (non-stationary, random, multicomponent vibrations) the system of control and synchronization play a major role. The methods of synchronization of laser radiation with the phases of investigated dynamic processes, designed by authors, are considered. The capability of the development the newest mobile holographic complex, including the powerful superstable double-pulse laser, kit of removable digital interferometers with selective sensitivity and unified computer system of control of laser radiation, recording and processing of digital interferograms are considered. The new design solutions of the main unit of a complex are discussed.
In the paper we report some factors which determine the quality of stroboscopic holography. A one-side fixed ruler is considered as a model for theoretical investigation. It is shown that by compensation of one frequency of mode-shape the viewed interferometric picture depends not only on mode-shape of a second frequency (harmonic, for example), but also from the duration of strobe-pulses and accuracy of phases of stroboscopic illumination. A parasitic system of interferometric fringes and mode-shape distortion may be observed. Computer calculations have shown that the displacement of position of interferometric fringes leads to errors in the analysis of holographic information. Experimental investigation by using the special stroboholographic system confirmed the theoretical investigation. A parasitic system of interferometric fringes is distinctly observed on the hologram when phases of strobe- pulses are set up incorrectly. A new stroboholographic arrangement where parameters of stability of strobe-pulse duration and accurate phase improved the results.
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