14 February 2005 Vibration measurements by pulsed digital holographic endoscopy
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Proceedings Volume 5776, Eighth International Symposium on Laser Metrology; (2005) https://doi.org/10.1117/12.611745
Event: Eighth International Conference on Laser Metrology, 2005, Merida, Mexico
Digital holographic interferometry in combination with a flexible fiber endoscope allows high precision measurements of deformations on hidden objects surfaces, inside cavities and objects with small access apertures. A digital holographic endoscopy system is described with a frequency-doubled, twin oscillator Q-switched pulsed Nd:YAG laser as light source. A sequence of digital hologram pairs are recorded with a maximum repetition rate of 260 ms. Each digital hologram is captured at separate video frames of a CCD-camera. The time separation between the laser pulses from each cavity can be set in the range from 50 to 500 μs. The digital holograms are transferred to a PC via a frame grabber and evaluated quantitatively by the Fourier transform method. The resulting phase fringe pattern has the information needed to evaluate quantitatively the amount of the deformation. Experimental results of vibration measurements of hidden mechanical and biological object surfaces are presented. The quality of the results obtained by mechanical object surfaces is usually higher than for biological surfaces. This can be explained easily by the fact that a biological surface is much more complex than a mechanical surface in the sense that some parts of the surface may reflect the light well whereas other parts may absorb the light. Also, biological surfaces are translucent, which means that part of the light may enter inside the sample where it may be absorbed or reflected.
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Staffan Schedin, Staffan Schedin, Giancarlo Pedrini, Giancarlo Pedrini, Carlos Perez-Lopez, Carlos Perez-Lopez, Fernando Mendoza Santoyo, Fernando Mendoza Santoyo, } "Vibration measurements by pulsed digital holographic endoscopy", Proc. SPIE 5776, Eighth International Symposium on Laser Metrology, (14 February 2005); doi: 10.1117/12.611745; https://doi.org/10.1117/12.611745

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