Digital holography for mechanical vibration measurements in rigid body displacement: elimination of the latter by means of a variable focal length adjustment

Carlos Pérez-López; Fernando Mendoza Santoyo; David Asael Gutiérrez Hernández; Silvino Muñoz Solis

doi:10.1117/12.803005

17 June 2008 Digital holography for mechanical vibration measurements in rigid body displacement: elimination of the latter by means of a variable focal length adjustment

Carlos Pérez-López, Fernando Mendoza Santoyo, David Asael Gutiérrez Hernández, Silvino Muñoz Solis

Author Affiliations +

Proceedings Volume 7098, Eighth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications; 70980N (2008) https://doi.org/10.1117/12.803005
Event: Eighth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, 2008, Ancona, Italy

Abstract

We present our investigation on the separation of mechanical vibrations from rigid body displacements. Pairs of digital holograms acquired between two consecutive time intervals from this type of events produce phase maps that contain both the vibration and rigid body motion information, or even further fully decorrelated phase maps after computer processing. In order to compensate for body displacements, a conjugate object-image experimental arrangement for digital holography is used to measure the mechanical vibrations in a rectangular flat plate. This is achieved by including an extra lens with variable focal length adjustments in front of the typical lens-aperture combination used in the optical head of a digital holographic set up. Out of plane data is obtained from a framed metal plate subjected to a known modal vibration that is also allowed to move perpendicularly to its surface. We will demonstrate that due to the power adjustment of the added lens the angular phase change in the digital hologram from the known object motion allows the separation of the vibration mode at the image plane. The proposed lens addition into a new optical head arrangement in digital holography combined with an a priori knowledge of the rigid body displacement is able to accurately separate the mechanical vibrations making it a promising method in experiments performed under noisy environments. This research suggests the inclusion of adaptive lenses to control the effective focal length when there is a need to separate two distinctive motion types, i.e., vibration from rigid body motion.

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Carlos Pérez-López, Fernando Mendoza Santoyo, David Asael Gutiérrez Hernández, and Silvino Muñoz Solis "Digital holography for mechanical vibration measurements in rigid body displacement: elimination of the latter by means of a variable focal length adjustment", Proc. SPIE 7098, Eighth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, 70980N (17 June 2008); https://doi.org/10.1117/12.803005

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KEYWORDS

Digital holography

Holograms

Holography

Head

Vibrometry

Cameras

Digital imaging

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