scholarly journals A New Pattern Quality Assessment Criterion and Defocusing Degree Determination of Laser Speckle Correlation Method

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4728
Author(s):  
Wenxin Hu ◽  
Zhipeng Sheng ◽  
Keyu Yan ◽  
Hong Miao ◽  
Yu Fu
Keyword(s):  
Quality Assessment ◽  
Speckle Pattern ◽  
Correlation Method ◽  
Quality Criterion ◽  
Laser Speckle ◽  
Widespread Application ◽  
Speckle Correlation ◽  
Speckle Patterns ◽  
Speckle Size

The laser speckle correlation method has found widespread application for obtaining information from vibrating objects. However, the resolution and accuracy of the laser speckle correlation method as they relate to the defocusing degree have not been analyzed sufficiently. Furthermore, the possible methods for speckle pattern quality assessment and enhancement have not been studied. In this study, the resolution and accuracy of the laser speckle correlation method are analyzed, and it is found that they are affected by the defocusing degree and speckle pattern quality, respectively. A new speckle pattern quality criterion combining the mean intensity gradient and frequency spectrum was proposed, called CMZ. The quality of the speckle pattern is higher when the CMZ is closer to zero. The proposed criterion was verified by simulated speckle patterns and real speckle patterns with different speckle sizes, densities, and gray contrasts. In the experimental setup stage, a suitable defocusing degree can be selected based on the resolution requirement and optimal speckle size, and other experimental parameters can be determined according to the CMZ criterion. Rotation and vibration experiments verified the effectiveness of the laser speckle correlation method and confirmed the reliability of the experiment preparation based on proposed CMZ criterion.

scholarly journals A Simulation Analysis of an Extension of One-Dimensional Speckle Correlation Method for Detection of General In-Plane Translation

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Ivana Hamarová ◽  
Petr Šmíd ◽  
Pavel Horváth ◽  
Miroslav Hrabovský
Keyword(s):  
Simulation Analysis ◽  
Speckle Pattern ◽  
Correlation Method ◽  
Object Plane ◽  
Speckle Field ◽  
Geometrical Arrangement ◽  
One Dimensional ◽  
Speckle Correlation ◽  
Speckle Patterns

The purpose of the study is to show a proposal of an extension of a one-dimensional speckle correlation method, which is primarily intended for determination of one-dimensional object's translation, for detection of general in-plane object's translation. In that view, a numerical simulation of a displacement of the speckle field as a consequence of general in-plane object's translation is presented. The translation componentsaxandayrepresenting the projections of a vectoraof the object's displacement onto bothx- andy-axes in the object plane(x,y)are evaluated separately by means of the extended one-dimensional speckle correlation method. Moreover, one can perform a distinct optimization of the method by reduction of intensity values representing detected speckle patterns. The theoretical relations between the translation componentsaxandayof the object and the displacement of the speckle pattern for selected geometrical arrangement are mentioned and used for the testifying of the proposed method's rightness.

scholarly journals A Portable Compact System for Laser Speckle Correlation Imaging of Artworks Using Projected Speckle Pattern

2020 ◽  
Vol 6 (11) ◽  
pp. 119
Author(s):  
Claudia Daffara ◽  
Elisa Marini
Keyword(s):  
Surface Deformation ◽  
Short Pulse ◽  
Speckle Pattern ◽  
Laser Speckle ◽  
Image Correlation ◽  
Thermal Stimulus ◽  
Intensity Pattern ◽  
Speckle Correlation ◽  
Speckle Size ◽  
Subsurface Defects

Artworks have a layered structure subjected to alterations caused by various factors. The monitoring of defects at sub-millimeter scale may be performed by laser interferometric techniques. The aim of this work was to develop a compact system to perform laser speckle imaging in situ for effective mapping of subsurface defects in paintings. The device was designed to be versatile with the possibility of optimizing the performance by easy parameters adjustment. The system exploits a laser speckle pattern generated through an optical diffuser and projected onto the artworks and image correlation techniques for the analysis of the speckle intensity pattern. A protocol for the optimal measurement was suggested, based on calibration curves for tuning the mean speckle size in the acquired intensity pattern. The system was validated in the analysis of detachments in an ancient painting model using a short pulse thermal stimulus to induce a surface deformation field and standard decorrelation algorithms for speckle pattern matching. The device is equipped with a compact thermal camera for preventing any overheating effects during the phase of the stimulus. The developed system represents a valuable nondestructive tool for artwork diagnostics, allowing the monitoring of subsurface defects in paintings in out-of-laboratory environment.

scholarly journals Methods for Determination of Mean Speckle Size in Simulated Speckle Pattern

2014 ◽  
Vol 14 (3) ◽  
pp. 177-182 ◽  
Author(s):  
I. Hamarová ◽  
P. Šmíd ◽  
P. Horváth ◽  
M. Hrabovský
Keyword(s):  
Gaussian Beam ◽  
Speckle Pattern ◽  
Two Dimensional ◽  
One Dimensional ◽  
Theoretical Predictions ◽  
Speckle Patterns ◽  
Speckle Size ◽  
The Mean ◽  
The One

Abstract This paper deals with computation of mean speckle size in a speckle pattern generated through a numerical simulation of speckle after reflection of a Gaussian beam off a rough object’s surface. Within this simulation various speckle patterns are obtained by means of change in a parameter of the Gaussian beam. The mean speckle size is computed through two approaches using both the two-dimensional and the one-dimensional normalized autocorrelation function in intensity. Additionally, we propose a distinct optimization of the determination of the mean speckle size by reduction of intensity values representing detected speckle patterns. Results of the determination of the mean speckle size are compared with theoretical predictions

scholarly journals A new simulation method for laser speckle imaging to investigate hemodynamics

2019 ◽  
Vol 128 ◽  
pp. 02001
Author(s):  
X Sang ◽  
D Li ◽  
B Chen
Keyword(s):  
Speckle Pattern ◽  
Simulation Method ◽  
Laser Speckle ◽  
Contrast Imaging ◽  
Laser Speckle Imaging ◽  
Speckle Imaging ◽  
Dynamic Speckle ◽  
Speckle Size ◽  
The One

Speckle simulation is a powerful protocol to investigate the properties of speckle and evaluate image processing method. However, only static speckle images can be simulated by available methods without considering time-integrated effect of CCD. A time–integrated dynamic speckle simulation method basedon coherent imaging was developed. Through the new simulation method, the effect of speckle size on LSCI was investigated. The smaller the speckle size is, the higher the spatial resolution become.But the one-dimensional speckle size should exceed two pixels to sample the speckle pattern. The characteristics of existing speckle contrast imaging methods were studied based on spatial statistics, and optimal parameters are given to obtain accurate and less noisy image. In general, the new simulation method for laser speckle imaging is a powerful tool to monitor blood flow in vivo and lay a solid foundation for the study of hemodynamics.

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