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Speckle imaging
About: Speckle imaging is a research topic. Over the lifetime, 3730 publications have been published within this topic receiving 62354 citations.
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TL;DR: This work experimentally demonstrates that given a known target, or even a light point-source, the other unknown object beyond the ME can be determined with only a single-shot camera image, even if the information of targets are mixed in the speckle pattern.
49 citations
49 citations
TL;DR: This work discusses the development of the digital holographic interferometer and the results obtained on a representative space reflector, first in the laboratory and then during vacuum cryogenic test.
Abstract: Digital holographic interferometry in the long-wave infrared domain has been developed by combining a CO2 laser and a microbolometer array The long wavelength allows large deformation measurements, which are of interest in the case of large space reflectors undergoing thermal changes when in orbit We review holography at such wavelengths and present some specific aspects related to this spectral range on our measurements For the design of our digital holographic interferometer, we studied the possibility of illuminating specular objects by a reflective diffuser We discuss the development of the interferometer and the results obtained on a representative space reflector, first in the laboratory and then during vacuum cryogenic test
49 citations
TL;DR: In this paper, two new techniques for spatial phase stepping using a computer-generated holographic optical element (HOE) are described, and implemented with electronic speckle pattern interferom- etry, although they could be applied to other optical metrology methods.
Abstract: We describe two new techniques for spatial phase stepping using a computer-generated holographic optical element (HOE). The techniques are implemented with electronic speckle pattern interferom- etry, although they could be applied to other optical metrology methods. The first technique uses an HOE that introduces a known phase step between the 61 diffracted orders, without being translated. The interfer- ence phase corresponding to object deformation can be calculated from a single TV frame, and the technique is therefore suitable for the mea- surement of transient deformations. We apply the technique to measure the phase changes caused by refractive index variations in an evolving thermal plume. The second technique requires the HOE to be used in conjunction with a phase grating. In this technique, the HOE and the phase grating are used sequentially for the two exposures required in speckle interferometry (made before and after object deformation) and is therefore suitable for making dynamic deformation measurements with a double-pulsed interferometer. A root mean square (rms) precision of 2p/20 rad for the phase measurements is obtained. © 1999 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(99)00712-6)
49 citations
TL;DR: A quantitative relation between the decorrelation of the scattered light fields and the rate of corrosion is established in a theoretical model, based on the statistics of phase and reflectivity changes of point scatterers at the surface.
Abstract: The changes in the microtopography of a metal surface during a corrosion process are measured by decorrelation of the scattered speckle fields under coherent illumination. For that purpose a quantitative relation between the decorrelation of the scattered light fields and the rate of corrosion is established in a theoretical model, based on the statistics of phase and reflectivity changes of point scatterers at the surface. The speckle fields are recorded by a CCD camera and processed numerically in a computer, yielding the standard deviation of the topography changes with nanometer sensitivity. From the analysis of a series of images taken at equal time intervals during the corrosion process, the degree of interrelation among subsequent topography changes is calculated.
48 citations