Speckle imaging

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

Sub-Rayleigh imaging via speckle illumination.

Abstract: We demonstrate sub-Rayleigh limit imaging of an object via speckle illumination. Imaging beyond the conventional Rayleigh limit is achieved by illuminating the object with pseudothermal light that exhibits a random speckle pattern. An object image is reconstructed from the second-order correlation measurement and the resolution of the image, which exceeds the Rayleigh limit, is shown to be related to the size of the speckle pattern that is tied to the lateral coherence length of the pseudothermal light.

Speckle interferometry at SOAR in 2012 and 2013

Abstract: We report the results of speckle runs at the 4.1 m Southern Astronomical Research telescope in 2012 and 2013. A total of 586 objects were observed. We give 699 measurements of 487 resolved binaries and upper detection limits for 112 unresolved stars. Eleven pairs (including one triple) were resolved for the first time. Orbital elements have been determined for the first time for 13 pairs; orbits of another 45 binaries are revised or updated.

Electronic speckle pattern interferometric system based on a speckle reference beam

Abstract: A new electronic speckle pattern interferometric (ESPI) technique is introduced. The technique is based on a reference beam combined with a large aperture optical system. The basic principles are described and compared with conventional ESPI setups. The new interferometer is easy to adjust, it is invulnerable to dust and scratches on the optical components, and is very compact. It is well-suited for practical engineering applications. Light sensitivity and fringe quality are comparable with the conventional ESPI features. Superior fringe pattern can be obtained by use of a new speckle reduction technique to be described.

Laser speckle microstrain measurement in vascular tissue

Abstract: Changes in the ultrastructure of vascular tissue due to pathologies such as atherosclerosis may be manifested as subtle changes in the mechanical properties of the arterial wall. The ability to detect these changes is considered to be important in the early diagnosis of atherosclerosis. In order to evaluate the subtle viscoelastic properties of the arterial wall, a highly sensitive means of evaluating mechanical strain in the tissue is required. Herein we will present a novel laser speckle strain gauge for evaluating mechanical microstrains in perfused and superfused vessel segments. The strain gauge relies upon 2D frequency transforms of stacked speckle histories, which are time sequences of one dimensional views of the backscattered light stacked into a 2D array such that time is along the vertical axis and space is along the horizontal axis. The gauge can be made sensitive only to in-plane strains. Sensitivity of the gauge is on the order of single microstrain. By mechanically straining the vessel segments in a custom microtensile testing machine fitted with a high sensitivity load cell, mechanical constants of the vessel wall can be derived and changes in the mechanical behavior due to disease can be evaluated.

Noncontacting strain measurements at high temperatures by the digital laser speckle technique

Abstract: This paper presents a newly developed laser-based noncontacting strain sensor suitable for temperatures up to 1200°C, which was adapted to a commercial tensile testing machine equipped with an electrical furnace. The principle of the strain sensor is based on tracking laser speckles through a digital correlation technique. Furthermore, the description of the signal processing and the optical arrangement is presented. Based on the experimental data, it can be show that this simple, laser-based strain sensor can be used successfully for the determination of mechanical and thermal strains up to temperatures of about 1200°C. Using a special data-processing procedure, it was feasible to minimize decorrelation effects caused by changes in the specimen surface due to, for example, slipband and microcrack formation, surface oxidation and phase transformation and, thus, measure large mechanical strains. The strain resolution for the selected setup was about 20 microstrains depending on the testing parameters.