scholarly journals The Influence of the Speckle Structure of the Scattered Laser Radiation on the Measurement Error of the Rough Surface Vibration Displacement

2019 ◽  
Author(s):  
Илья Павлов ◽  
Il'ya Pavlov ◽  
Ирина Расковская ◽  
Irina Raskovskaya ◽  
Бронюс Ринкевичюс ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Laser Radiation ◽  
Measurement Error ◽  
Rough Surface ◽  
Laser Doppler Vibrometer ◽  
Average Intensity ◽  
Speckle Structure ◽  
Vibration Displacement ◽  
Speckle Field ◽  
Surface Vibration

The influence of the speckle structure of the scattered laser radiation on the measurement error of the rough surface vibration displacementusing laser Doppler vibrometer assembled according to a differential scheme is studied. The scheme of the experimental setup for investigation of characteristics of laser beam reflected from different surfaces is described and the obtaineed experimental images are given. It is shown that the structure of a reflected and scattered beam highly dependent on parameters of roughness of an investigated surface. Based on the results of numerical simulation, characteristic dimensions of surface irregularities are obtained, at which the beam structure is destroyed and the speckle structure is formed. It is shown that in case of a partially developed speckle structure, the error will be determined by by the relative contribution of a mirror component, a contrast and an average intensity of a speckle field. To estimate the error, a numerical simulation was performed for given parameters of a surface, beam and scatterers.

scholarly journals DEPENDENCE OF THE SPECKLE-PATTERNS SIZE AND THEIR CONTRAST ON THE BIOPHYSICAL AND STRUCTURAL PARAMETERS OF BIOLOGICAL TISSUES

2017 ◽  
Vol 8 (2) ◽  
pp. 177-187
Author(s):  
N. D. Abramovich ◽  
S. K. Dick
Keyword(s):  
Laser Radiation ◽  
Stratum Corneum ◽  
Volume Concentration ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Scattered Light ◽  
Biological Tissues ◽  
Speckle Structure ◽  
Speckle Field ◽  
Blood Capillaries

Speckle fields are widely used in optical diagnostics of biotissues and evaluation of the functional state of bioobjects. The speckle field is formed by laser radiation scattered from the object under study. It bears information about the average dimensions of the scatterers, the degree of surface roughness makes it possible to judge the structural and biophysical characteristics of individual tissue cells (particles), on the one hand, and the integral optical characteristics of the entire biological tissue. The aim of the study was – the determination of connections between the biophysical and structural characteristics of the biotissue and the light fields inside the biotissues.The model developed of the medium gives a direct relationship between the optical and biophysical parameters of the biotissue. Calculations were carried out using known solutions of the radiation transfer equation, taking into account the multilayer structure of the tissue, multiple scattering in the medium, and multiple reflection of irradiation between the layers.With the increase wavelength, the size of speckles formed by the non-scattered component (direct light) of laser radiation increases by a factor of 2 from 400 to 800 μm in the stratum corneum and 5 times from 0.6 to 3 μm for the epidermis and from 0.27 to 1.4 μm to the dermis. Typical values of sizes of speckles formed by the diffraction component of laser radiation for the stratum corneum and epidermis range from 0.02 to 0.15 μm. For the dermis typical spot sizes are up to 0.03 μm. The speckle-spot size of the diffusion component in the dermis can vary from ±10 % at 400 nm and up to ±23 % for 800 nm when the volume concentration of blood capillaries changes. Characteristic dependencies are obtained and biophysical factors associated with the volume concentration of blood and the degree of it’s oxygenation that affect the contrast of the speckle structure in the dermis are discussed.The of speckles׳ size in the layers of tissue varies from a share of micrometer to millimeter. The established dependence makes it possible to determine the depth of penetration of light into the biotissue based on the dimensions of speckles. Calculation of the contrast of the speckle structure of scattered light in visible spectral range at different depths in the biotissue made it possible to establish the dependence of the contrast value of the interference pattern on the degree of oxygenation of the blood and the volume concentration of capillaries in the dermis.

Software system for numerical simulation of broadband laser gas analysis of the atmosphere

2018 ◽  
pp. 66-73 ◽  
Author(s):  
S. A. Sadovnikov
Keyword(s):  
Numerical Simulation ◽  
Laser Radiation ◽  
Gas Analysis ◽  
Modular System ◽  
Software System ◽  
Transmission Spectra ◽  
Molecular Absorption ◽  
Molecular Scattering ◽  
Atmospheric Transmission ◽  
Wide Range

Introduction: Successful monitoring of environmental parameters requires the development of flexible software complexes with evolvable calculation functionality. Purpose: Developing a modular system for numerical simulation of atmospheric laser gas analysis. Results: Based on differential absorption method, a software system has been developed which provides the calculation of molecular absorption cross-sections, molecular absorption coefficients, atmospheric transmission spectra, and lidar signals. Absorption line contours are calculated using the Voigt profile. The prior information sources are HITRAN spectroscopic databases and statistical models of the distribution of temperature, pressure and gas components in the atmosphere. For modeling lidar signals, software blocks of calculating the molecular scattering coefficient and aerosol absorption/scattering coefficients were developed. For testing the applicability of various laser sources in the problems of environmental monitoring of the atmosphere, a concentration reconstruction error calculation block was developed for the atmospheric gas components, ignoring the interfering absorption of laser radiation by foreign gases. To verify the correct functioning of the software, a program block was developed for comparing the results of the modeling of atmospheric absorption and transmission spectra by using the standard SPECTRA information system. The discrepancy between the calculation of the atmospheric transmission spectra obtained using the developed system as compared to the SPECTRA results is less than 1%. Thus, a set of the presented program blocks allows you to carry out complex modeling of remote atmospheric gas analysis. Practical relevance: The software complex allows you to rapidly assess the possibilities of using a wide range of laser radiation sources for the problems of remote gas analysis.

scholarly journals Numerical simulation of changes in the electric properties of biological tissues under local heating by laser radiation

2021 ◽  
Vol 2090 (1) ◽  
pp. 012049
Author(s):  
N V Kovalenko ◽  
A V Smirnov ◽  
O A Ryabushkin
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Laser Radiation ◽  
Optical Radiation ◽  
Local Heating ◽  
Biological Tissues ◽  
Electric Properties ◽  
Reliable Tool ◽  
The Mathematical Model

Abstract The mathematical model that describes the local heating of biological tissues by optical radiation is introduced. Changes of the electric properties of biological tissues in such process can be used as a reliable tool for analyzing heating and damage degrees of tissues.

Numerical Simulation of Rough Surface with Crossed Texture

2013 ◽  
Vol 321-324 ◽  
pp. 196-200 ◽  
Author(s):  
Ming Wei Chui ◽  
You Qian Feng ◽  
Wei Wang ◽  
Pei Lin Li ◽  
Zheng Chao Li
Keyword(s):  
Numerical Simulation ◽  
Rough Surface ◽  
Autocorrelation Function ◽  
Reference System ◽  
Surface Engineering ◽  
Rough Surfaces ◽  
Periodic Fluctuation ◽  
Simulated Surface ◽  
Simulation Results

To meet the demands for rough surfaces data in the research of surface engineering, contacts characteristic and so on, a new numerical simulation of rough surface is proposed. Based on FFT method, rough surface with single direction texture is simulated with circular cosine-exponent autocorrelation function (ACF), and the generated surface is rotated of different given angles respectively by rotation of reference system, then the rough surface with multi-direction texture is created by synthesizing the rotated surfaces. The simulation results show that, the ACF curves of generated surface is periodic fluctuation decay, and has a good fitting result with the predetermined ACF. The contrast result between simulated surface and measured surface shows the available of the proposed method.

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