Speckle imaging

About: Speckle imaging is a research topic. Over the lifetime, 3730 publications have been published within this topic receiving 62354 citations.

Speckle interferometry at finite spectral bandwidths and exposure times

Abstract: The effects of wavelength, spectral bandpass, and exposure time on the speckle lens-atmosphere modulation transfer function have been measured using bright stellar sources.

Stellar Optical Interferometry in the 1990s

Abstract: The unaided eye has an angular resolution of about 1 arcminute. From the invention of the telescope in the 17th century to the middle of the 1970s, astronomers improved on this resolution by two orders of magnitude by building bigger telescopes and putting them at good sites. Even at good sites, however, atmospheric turbulence limits the resolution at visible and infrared wavelengths to 1 arcsec or a little better. In the past 20 years, a further factor‐of‐ten improvement has come with two developments that deal with the atmosphere: “speckle interferometry,” in which the blurred image is frozen in a short exposure and the image is reconstructed from many exposures, and adaptive optics, in which the effects of the atmosphere are sensed, then corrected with a defbrmable mirror, before the image is recorded. (See Laird A. Thompson's article in PHYSICS TODAY, December 1994, page 24.)

Impact of speckle on laser range-gated shortwave infrared imaging system target identification performance

Abstract: The U.S. Army and the U.S. Air Force are investigating laser range-gated shortwave infrared (LRG-SWIR) imaging systems for use in target identification. When coupled to an electron-bombarded CCD, the imaging system can obtain high- resolution images at long ranges. Speckle, an image artifact inherent in laser illuminated imaging systems, results from interference patterns caused by the coherent illumination. Laser speckle degrades target identification performance but can be reduced by averaging successive LRG-SWIR images. This research is a first attempt at quantifying target identification performance degradation associated with laser speckle. The research begins with a laboratory experiment to verify a speckle model that includes power spectral density and intensity probability density functions. An LRG-SWIR sensor simulation is developed that includes coherent illumination resulting in speckle target images. A field demonstration is performed to verify the fidelity of the simulation. The simulation is then applied to the NVESD target identification set with various levels of image averaging and blur. Observer performance results are analyzed in terms of target identification probability and the effects of various levels of blur and speckle are characterized.

Compressive fluorescence imaging using a multi-core fiber and spatially dependent scattering.

Abstract: We demonstrate imaging using a multi-core fiber with a scattering distal tip and compressed sensing signal acquisition. We illuminate objects with randomly structured speckle patterns generated by a coherent light source separately coupled through each fiber core to a ground glass diffuser at the distal end. Using the characterized speckle patterns and the total light collected from the object, we computationally recover pixelation-free object images with up to a seven times higher space-bandwidth product than the number of cores. The proposed imaging system is insensitive to bending of the fiber and extremely compact, making it suitable for minimally invasive endomicroscopy.

Laser speckle imaging based on intensity fluctuation modulation

Abstract: We present a method, intensity fluctuation modulation (IFM), to obtain a full-field laser speckle microvessel image. Different from laser speckle contrast analysis, IFM imaging is insensitive to flow velocity and can be used to reconstruct microvessel images with higher spatial resolution and SNR. An in vivo animal experiment on a mouse pinna is conducted to demonstrate that IFM imaging is capable of achieving laser speckle microangiography.