Experimental And Monte Carlo Simulation Of Laser Side Scattering In Turbid Media

The scattering properties of laser in the media are the basis of many optical measurement techniques.By measuring the intensity of scattering light in the turbid media,information such as the size,shape and concentration of the scattering particles can be obtained.The Monte Carlo method has been widely used in the research of particle transmission,and the improvement of related codes has always been an active research area.In order to explore the multiple scattering of laser in the media,this paper investigate side scattering of laser in the turbid medium by experimental,using charge-coupled device(CCD)as the receiving device.Based on the experiment,we establish a Monte Carlo simulation model and get Two-dimensional side scattering light intensity which distribution consistent with experimental results.The specific research content is as follows:(1)First,this paper introduces three parameters of extinction,scattering and absorption efficiency required to characterize light scattering of particles.Combining with the recurrence formula of Mie scattering theory,the corresponding calculation methods of these parameters are given.The analysis points out that the factors affecting the scattering and absorption efficiency of the media are the refractive index and the scale parameters,which provide the necessary theoretical support for configuring the turbid medium required for experimental research.In addition,according to Mie scattering,the scattering phase function of particles with different sizes is also given.The forward scattering of particles with larger particle size is stronger.Then the Monte Carlo method is introduced.The commonly used H-G scattering phase function in simulation is discussed in detail and compared with the calculated value of Mie scattering theory.(2)Using a laser with a wavelength of 532 nm as the light source and a lens-equipped CCD camera as the receiver,an experimental device was built to study the multiple scattering of laser light in turbid media.According to the corresponding light scattering theory,configuring turbid media with different optical parameters for experiments by using polystyrene particles.By changing the number concentration of polystyrene particles to control the optical depth of the media equaling to 2,5 and 8.The scattering phase function for individual medium particles is varied by using different particle with a diameter of 5?m and 10?m respectively.The experimental result image and the normalized light intensity value show that the side scattering light intensity of laser in the turbid media increases along with the increase of the optical depth,and the attenuation of the scattering light intensity is also stronger in the larger optical depth.The width of the scattering beam increases along with the optical depth.Under the same optical depth,the side scattering light intensity of laser in 5?m particle media is stronger than that of 10 ?m,which is consistent with the scattering phase function calculated by Mie scattering theory.(3)According to the initial optical parameters given in the experiment,a Monte Carlo simulation model for laser transmission in turbid media is established.In order to solve the problem of low accuracy of the H-G scattering phase function,the scattering angle is obtained by interpolating the cumulative probability density of the Mie scattering phase function.The simulation has obtained a high-resolution two-dimensional distribution of side scattering light intensity.For each media configuration,the rule of image changing obtained by the simulation and experimental has a good consistency.Then the experimental and simulation light intensity of 16.7 mm×8.8 mm near the incident end is compared by quantity.Under the same medium conditions,the ratio of the maximum scattering light intensity to the incident light intensity is the same order of magnitude,and the percentage difference of scattering light intensity attenuation is less than 16%.The trend of the scattering light intensity curve is basically the same.The simulation model can provide the distribution of light intensity varying with the scattering orders.The scattering order distribution is determined by the optical depth of the media and independent to the particle size.This shows that the Monte Carlo simulation we established can analyze the effect of multiple scattering accurately.