Video-rate laser Doppler vibrometry by heterodyne holography

We report a demonstration video-rate heterodyne holography in off-axis configuration. Reconstruction and display of 1 Megapixel holograms is achieved at 24 frames per second, with a graphics processing unit. Our claims are validated with real-time screening of steady-state vibration amplitudes in a wide-field, non-contact vibrometry experiment.Comment: Optics Letters (2011) 00

Imaging of a vibrating object by Sideband Digital Holography

We obtain quantitative measurements of the oscillation amplitude of vibrating objects by using sideband digital holography. The frequency sidebands on the light scattered by the object, shifted by n times the vibration frequency, are selectively detected by heterodyne holography, and images of the object are calculated for different orders n. Orders up to n=120 have been observed, allowing the measurement of amplitudes of oscillation that are significantly larger than the optical wavelength. Using the positions of the zeros of intensity for each value of n, we reconstruct the shape of vibration the object.Comment: 6 page

Sensitivity of synthetic aperture laser optical feedback imaging

In this paper we compare the sensitivity of two imaging configurations both based on Laser Optical Feedback Imaging (LOFI). The first one is direct imaging, which uses conventional optical focalisation on target and the second one is made by Synthetic Aperture (SA) Laser, which uses numerical focalisation. We show that SA configuration allows to obtain good resolutions with high working distance and that the drawback of SA imagery is that it has a worse photometric balance in comparison to conventional microscope. This drawback is partially compensated by the important sensitivity of LOFI. Another interest of SA relies on the capacity of getting a 3D information in a single x-y scan

Limitations of synthetic aperture laser optical feedback imaging

In this paper we study the origin and the effect of amplitude and phase noise on Laser Optical Feedback Imaging (LOFI) associated with Synthetic Aperture (SA) imaging system. Amplitude noise corresponds to photon noise and acts as an additive noise, it can be reduced by increasing the global measurement time. Phase noise can be divided in three families: random, sinusoidal and drift phase noise; we show that it acts as a multiplicative noise. We explain how we can reduce phase noise by making oversampling or multiple measurements depending on its type. This work can easily be extended to all SA systems (Radar, Laser or Terahertz), especially when raw holograms are acquired point by point

Synthetic aperture laser optical feedback imaging using a translational scanning with galvanometric mirrors

In this paper we present an experimental setup based on Laser Optical Feedback Imaging (LOFI) and on Synthetic Aperture (SA) with translational scanning by galvanometric mirrors for the purpose of making deep and resolved images through scattering media. We provide real 2D optical synthetic-aperture image of a fixed scattering target with a moving aperture and an isotropic resolution. We demonstrate theoretically and experimentally that we can keep microscope resolution beyond the working distance. A photometric balance is made and we show that the number of photons participating in the final image decreases with the square of the reconstruction distance. This degradation is partially compensated by the high sensitivity of LOFI