Pulsed holographic interferometry with photorefractive crystals. Recent advances of the european “PHIFE” project. Marc GEORGES , Philippe C. LEMAIRE , Centre Spatial de Liège, Angleur (B) Gilles PAULIAT, Gérald ROOSEN Laboratoire Charles Fabry de l ’Institut d ’Optique, Orsay (F) - PowerPoint PPT Presentation
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Pulsed holographic interferometry with Pulsed holographic interferometry with photorefractive crystals. Recent advances of the photorefractive crystals. Recent advances of the
european “PHIFE” projecteuropean “PHIFE” project
Marc GEORGESMarc GEORGES, Philippe C. LEMAIRE, Philippe C. LEMAIRE, , Centre Spatial de Liège, Angleur (B)Centre Spatial de Liège, Angleur (B)
Application to holographic interferometryApplication to holographic interferometryinterference between diffracted beam (reference object state)interference between diffracted beam (reference object state)
Developments since 1998 (CSL and LCFIO)Developments since 1998 (CSL and LCFIO)– Use Q-switch YAG laser (COHERENT Infinity)Use Q-switch YAG laser (COHERENT Infinity)
frequency doubled : 532 nm (adapted to sillenite frequency doubled : 532 nm (adapted to sillenite crystals)crystals)
pulses : 3 nspulses : 3 ns
energies : 0 to 400 mJ/pulseenergies : 0 to 400 mJ/pulse
repetition rate : 0,1 to 30 Hzrepetition rate : 0,1 to 30 Hz
– Photorefractive crystal under isotropic diffraction processPhotorefractive crystal under isotropic diffraction process
Pulsed Holographic Interferometer for the analysis of Fast Pulsed Holographic Interferometer for the analysis of Fast EventsEvents
Goal : Develop a holographic cameraGoal : Develop a holographic camera– giving high resolution results typical of PRCsgiving high resolution results typical of PRCs
– working with working with double-pulse YAG Q-switch laserdouble-pulse YAG Q-switch laser• 25 Hz repetition rate25 Hz repetition rate
• energies 800 mJ (1064 nm) and 350 mJ (532 nm)energies 800 mJ (1064 nm) and 350 mJ (532 nm)
• variable delays (down to 10 microseconds)variable delays (down to 10 microseconds)
– provides provides phase quantified dataphase quantified data
– integrated to the laser head (single box)integrated to the laser head (single box)
– adapted or adaptable to adapted or adaptable to different applicationsdifferent applications : :• solid objects (vibrations, shocks, …)solid objects (vibrations, shocks, …)
• transparent objects (aerodynamic studies in windtunels)transparent objects (aerodynamic studies in windtunels)
Development of holographic headsDevelopment of holographic heads– ““Real-time” systems based on double-pulse lasersReal-time” systems based on double-pulse lasers
• 1064 nm : CdTe/AsGa1064 nm : CdTe/AsGa
• 532 nm : Bi532 nm : Bi1212SiOSiO2020
PHIFEPHIFE
t
record
readout
CCD emptied
– Phase quantification techniquesPhase quantification techniques• obtain a processable interferogram on a single pulseobtain a processable interferogram on a single pulse
• Techniques possible :Techniques possible :– Phase-shifting (multi-camera)Phase-shifting (multi-camera)
– Centre Spatial de Liège (B)Centre Spatial de Liège (B) : : Laboratory developments (532 nm)Laboratory developments (532 nm)
– Laboratoire Charles Fabry de l ’Institut d ’Optique, Orsay (F)Laboratoire Charles Fabry de l ’Institut d ’Optique, Orsay (F) : : Laboratory developments (1064 nm)Laboratory developments (1064 nm)
– Institut für Technische Optik, Stuttgart (D)Institut für Technische Optik, Stuttgart (D)• CCD triggering system and fast frame grabberCCD triggering system and fast frame grabber
Different crystal configurations (anisotropic vs. isotropic)Different crystal configurations (anisotropic vs. isotropic)– Same object - same field - same illumination powerSame object - same field - same illumination power
FFT single frame processing with carrier fringesFFT single frame processing with carrier fringes– carrier obtained by active techniques : carrier obtained by active techniques :
• moving optical elements between pulsesmoving optical elements between pulses
• Not possible or very difficult due to short delaysNot possible or very difficult due to short delays
– carrier obtained with new patented technique (LCFIO) :carrier obtained with new patented technique (LCFIO) :• 2 orthogonal polarisations (anisotropic diffraction)2 orthogonal polarisations (anisotropic diffraction)
• Birefringent plate after the crystalBirefringent plate after the crystal
• Phase shift between two orthogonal polarisationsPhase shift between two orthogonal polarisations
• Phase shift proportional to beam transverse coordinatesPhase shift proportional to beam transverse coordinates
• Result : rectilinear fringesResult : rectilinear fringes
Prototype building : choice of best configurations/geometriesPrototype building : choice of best configurations/geometries– Modular designModular design