Distribution of maxima, minima, and saddle points of the intensity of laser speckle patterns

1982 ◽  
Vol 26 (3) ◽  
pp. 1362-1368 ◽  
Author(s):  
Abel Weinrib ◽  
B. I. Halperin
Keyword(s):  
Saddle Points ◽  
Laser Speckle ◽  
Speckle Patterns

scholarly journals Fourier transforms for fast and quantitative Laser Speckle Imaging

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
J. Buijs ◽  
J. van der Gucht ◽  
J. Sprakel
Keyword(s):  
Quantitative Data ◽  
Fourier Transforms ◽  
Imaging Technique ◽  
Laser Speckle ◽  
Frequency Range ◽  
Laser Speckle Imaging ◽  
Speckle Imaging ◽  
New Approach ◽  
Speckle Patterns ◽  
New Processing

Abstract Laser speckle imaging is a powerful imaging technique that visualizes microscopic motion within turbid materials. At current two methods are widely used to analyze speckle data: one is fast but qualitative, the other quantitative but computationally expensive. We have developed a new processing algorithm based on the fast Fourier transform, which converts raw speckle patterns into maps of microscopic motion and is both fast and quantitative, providing a dynamnic spectrum of the material over a frequency range spanning several decades. In this article we show how to apply this algorithm and how to measure a diffusion coefficient with it. We show that this method is quantitative and several orders of magnitude faster than the existing quantitative method. Finally we harness the potential of this new approach by constructing a portable laser speckle imaging setup that performs quantitative data processing in real-time on a tablet.

An artifact-metrics which utilizes laser speckle patterns for plastic ID card surface

2010 ◽  
Author(s):  
Manabu Yamakoshi ◽  
Xiaoying Rong ◽  
Tsutomu Matsumoto
Keyword(s):  
Laser Speckle ◽  
Speckle Patterns

Image synthesis from nonimaged laser-speckle patterns

1987 ◽  
Vol 12 (11) ◽  
pp. 858 ◽  
Author(s):  
Paul S. Idell ◽  
J. R. Fienup ◽  
Ron S. Goodman
Keyword(s):  
Image Synthesis ◽  
Laser Speckle ◽  
Speckle Patterns

scholarly journals Gradient Correlation Functions in Digital Image Correlation

2019 ◽  
Vol 9 (10) ◽  
pp. 2127 ◽  
Author(s):  
Mikael Sjödahl
Keyword(s):  
Correlation Function ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Correlation Functions ◽  
Laser Speckle ◽  
Image Correlation ◽  
Intensity Correlation ◽  
Intensity Correlation Function ◽  
Speckle Patterns ◽  
The Difference

The performance of seven different correlation functions applied in Digital Image Correlation has been investigated using simulated and experimentally acquired laser speckle patterns. The correlation functions were constructed as combinations of the pure intensity correlation function, the gradient correlation function and the Hessian correlation function, respectively. It was found that the correlation function that was constructed as the product of all three pure correlation functions performed best for the small speckle sizes and large correlation values, respectively. The difference between the different functions disappeared as the speckle size increased and the correlation value dropped. On average, the random error of the combined correlation function was half that of the traditional intensity correlation function within the optimum region.

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.

Velocities of Starch Particles in ER Fluids Measured with Laser Speckle

2011 ◽  
Vol 287-290 ◽  
pp. 2781-2784
Author(s):  
Ji Jun Fan ◽  
Nan Hui Yu
Keyword(s):  
Electric Field ◽  
High Speed ◽  
Ccd Camera ◽  
Laser Speckle ◽  
Time Intervals ◽  
Sample Concentration ◽  
Speckle Patterns ◽  
The Mean ◽  
Er Fluids ◽  
Short Time

In this paper, the principle of measuring infinitesimal displacement by laser speckle is proposed to measure the velocities of particles in ER fluids. It is verified that speckles can be formed by illuminating laser beam on the starch ER fluids. The speckle patterns was recorded with high speed CCD camera, and the speckle patterns sequences with short time intervals was obtained by intercepting laser speckle video. Displacements parallel to the direction of electric field and that perpendicular to the direction of electric field were obtained by processing the two consecutive speckle patterns. The experimental results showed that the velocities of particles decreased oscillatorily with time. There is a critical electric field and a critical sample concentration, when lower than this critical electric field (concentration), the mean particle velocity increased; otherwise, it decreased.

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