In-plane, out-of-plane, and time-average speckle interferometry experiments with a digital photocamera

M. Vannoni; G. Molesini

doi:10.1117/12.597052

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8 June 2005 In-plane, out-of-plane, and time-average speckle interferometry experiments with a digital photocamera

M. Vannoni, G. Molesini

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Proceedings Volume 5827, Opto-Ireland 2005: Photonic Engineering; (2005) https://doi.org/10.1117/12.597052
Event: OPTO-Ireland, 2005, Dublin, Ireland

Abstract

We discuss classical experiments in the field of laser speckle interferometry. The typical optical setup consists of a laser diode and off-the-shelf optical elements, like a lens to expand the beam and plane mirrors to deflect it. A low-cost commercial CCD photocamera is used to acquire the speckle images. Items investigated are diffusing objects, illuminated with the laser diode and imaged on the CCD under appropriate experimental conditions. Pictures are taken both with the object at rest and under stress. The pictures are subtracted from one another with a standard software, pixel by pixel; the subtraction reveals fringes of the deformation occurred between the two exposures. With interferograms obtained in this way, we can study mechanical systems with an accuracy of the order of the wavelength of the light source used. Changing the optical setup, the measurement becomes sensitive to stresses along the camera optical axis direction (out-of-plane) or in the perpendicular plane (in-plane). Making long-time exposures it is also possible to study vibrational modes of suitable items (time-average). Three different setups are investigated and examples of measurement are reported.

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M. Vannoni and G. Molesini "In-plane, out-of-plane, and time-average speckle interferometry experiments with a digital photocamera", Proc. SPIE 5827, Opto-Ireland 2005: Photonic Engineering, (8 June 2005); https://doi.org/10.1117/12.597052

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