Fluid Mechanics and Acoustics Laboratory - UMR 5509

LMFA - UMR 5509
Laboratoire de Mécanique des Fluides et d’Acoustique
Lyon
France


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Home > Research Support > Scientific instrumentation > Techniques > Digital holography

Digital holography

The digital holography is an optical technique which gives the advantage to record a three-dimensional information of an object on a bidimensional support. It allows to know the size, the shape and the position in space or even the three velocity components of objects in the flow. The 3D informations of the lit particles are recorded on a 2D sensor and are then reconstructed thanks to the coherence properties of the used light source. To have a good spatial coherence, the source must be a point. The time coherence is related to the monochromaticity of the source. The classically used laser sources (continuous or pulsed) verify these coherence properties.

The experimental setup can be very simple such as the in-line holography case.

More complex setups such as multiple arms ones give a higher measurement precision in depth, can handle a bigger object density and can measure smaller objects.

The hologram restitution is based on the numerical simulation of the diffraction.


Measurements tools:
- Several double cavity pulsed Nd:Yag lasers (see PIV section)
- A double cavity pulsed Nd:YLF laser (see TR-PIV section)
- Several continuous wave argon or diode-pumped lasers, from 2 W to 5 W
- Several double frames CCD cameras (see PIV section)
- Several CMOS fast cameras (see TR-PIV section)
- Holograms restitution sofwares: one internally developed and one developed by C. Fournier (Laboratoire Hubert Curien - Université Jean Monnet)