scholarly journals Weak-scattering static diffuser by fast pumping dispersed-nanoparticles in a long distance using microfluidic flows for efficient laser speckle reduction

2018 ◽  
Vol 26 (16) ◽  
pp. 20270 ◽  
Author(s):  
Zhaomin Tong ◽  
Wenzhi Cheng ◽  
Suotang Jia ◽  
Xuyuan Chen
Keyword(s):  
Laser Speckle ◽  
Speckle Reduction ◽  
Long Distance ◽  
Weak Scattering ◽  
Microfluidic Flows

Laser speckle reduction by a hybrid MEMS diffuser device with continuous height profile

2017 ◽  
Vol 24 (6) ◽  
pp. 2561-2568
Author(s):  
Qiaoming You ◽  
Dayong Qiao ◽  
Xiumin Song ◽  
Changfeng Xia ◽  
Yanan Zhang
Keyword(s):  
Laser Speckle ◽  
Speckle Reduction ◽  
Height Profile

scholarly journals DeepLSR: a deep learning approach for laser speckle reduction

2019 ◽  
Vol 10 (6) ◽  
pp. 2869 ◽  
Author(s):  
Taylor L. Bobrow ◽  
Faisal Mahmood ◽  
Miguel Inserni ◽  
Nicholas J. Durr
Keyword(s):  
Deep Learning ◽  
Laser Speckle ◽  
Speckle Reduction ◽  
Learning Approach

Laser speckle reduction techniques for mid-infrared microscopy and stand-off spectroscopy

2017 ◽  
Author(s):  
Robert Furstenberg ◽  
Christopher A. Kendziora ◽  
Christopher J. Breshike ◽  
Viet Nguyen ◽  
R. Andrew McGill
Keyword(s):  
Laser Speckle ◽  
Speckle Reduction ◽  
Infrared Microscopy ◽  
Mid Infrared ◽  
Reduction Techniques

Laser Speckle Reduction in Retina Imaging Illumination

2008 ◽  
Vol 28 (12) ◽  
pp. 2245-2249 ◽  
Author(s):  
李抄 Li Chao ◽  
姜宝光 Jiang Baoguang ◽  
夏明亮 Xia Mingliang ◽  
程少园 Cheng Shaoyuan ◽  
宣丽 Xuan Li
Keyword(s):  
Laser Speckle ◽  
Speckle Reduction

P‐222: Late‐News‐Poster: Mechanically‐Static Laser Speckle Reduction Solution

2020 ◽  
Vol 51 (1) ◽  
pp. 1948-1951
Author(s):  
Kai-Han Chang ◽  
Thomas Seder ◽  
John Harden ◽  
Liang-Chy Chien
Keyword(s):  
Laser Speckle ◽  
Speckle Reduction ◽  
Late News

Acoustic Speckle: Theory and Experimental Analysis

1979 ◽  
Vol 1 (4) ◽  
pp. 303-324 ◽  
Author(s):  
John G. Abbott ◽  
F. L. Thurstone
Keyword(s):  
Experimental Study ◽  
Experimental Analysis ◽  
Phased Array ◽  
Imaging System ◽  
Experimental Studies ◽  
Laser Speckle ◽  
Speckle Reduction ◽  
Multiple Images ◽  
Starting Point ◽  
Speckle Patterns

A theoretical and experimental study of speckle, as applied to ultrasonic imaging, is presented. The concept of laser speckle is briefly reviewed and is used as a starting point to explain the origin of acoustic speckle. The primary differences between these two phenomena are discussed and are confirmed by experiment. An experimental study of speckle reduction by summation of multiple images is also presented. Several techniques for generating independent speckle patterns for use in image summation schemes are proposed. A phased array, dynamically focused sector imaging system was used in all of the experimental studies reported.

A generalized Rytov approximation for accurate calculation of phase variation in strong perturbation media

2019 ◽  
Vol 219 (2) ◽  
pp. 968-974 ◽  
Author(s):  
Bo Feng ◽  
Ru-Shan Wu ◽  
Huazhong Wang
Keyword(s):  
Plane Wave ◽  
Integral Kernel ◽  
Phase Variation ◽  
Forward Scattering ◽  
Phase Changes ◽  
Long Distance ◽  
Velocity Perturbation ◽  
Scattering Angle ◽  
Rytov Approximation ◽  
Weak Scattering

SUMMARY In the case of long-range propagation of forward scattering, due to the accumulation of phase changes caused by the velocity perturbations, the validity of the Born approximation will be violated. In contrast, the phase-change accumulation can be handled by the Rytov approximation, which has been widely used for long-distance propagation with only forward scattering or small-angle scattering involved. However, the weak scattering assumption (i.e. small velocity perturbation) in the Rytov approximation limits its scope of application. To address this problem, we analyse the integral kernel of the Rytov transform using the Wentzel-Kramers-Brillouin-Jeffreys (WKBJ) approximation and we demonstrate that the integral kernel is a function of velocity perturbation and scattering angle. By applying a small scattering angle approximation, we show that the phase variation has a linear relationship with the slowness perturbation, no matter how strong the magnitude of perturbation is. Therefore, the new integral equation is then referred to as the generalized Rytov approximation (GRA) because it overcomes the weak scattering assumption of the Rytov approximation. To show the limitations of the Rytov approximation and the advantages of the proposed GRA method, first we design a two-layer model and we analytically calculate the errors introduced by the small scattering angle assumption using plane wave incidence. We show that the phase (traveltime) variations predicted by the GRA are always more accurate than the Rytov approximation. Particularly, the GRA produces accurate phase variations for the normal incident plane wave regardless of the magnitude of velocity perturbation. Numerical examples using Gaussian anomaly models demonstrate that the scattering angle has a crucial impact on the accuracy of the GRA. If the small scattering angle assumption holds, the GRA can produce an accurate phase approximation even if the velocity perturbation is very strong. On the contrary, both the first-order Rytov approximation and the GRA fail to get satisfying results when the scattering angle is large enough. The proposed GRA method has the potential to be used for traveltime modelling and inversion for large-scale strong perturbation media.

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