Study On The Distribution Of Polarization Properties Of Linearly Polarized Light In Fruit Tissues

Fruit is very popular with people because of its rich nutritional value and tasty taste,and people’s daily life can not be separated from fruit.There are many optical methods for the dection of the quality of fruit,including machine vision,near infrared spectroscopy and hyperspectral imaging.These contents such as include sunburn,surface bruises,sugar,acidity,maturity,and soluble solids,are usually detected by reaearchers.However,it is difficult to use the traditional optical method to detect the diseases and insect pests in the fruit.At present,some scholars in the field of biomedicine have used the information carried by polarized light to detect the conventional invisible objects in the deep tissue.In order to carry out the detection of internal diseases and pests by polarized light imaging technology,it is of great significance to study the rule of polarization state in the propagation process of polarized light in fruit tissue and the polarization characteristics of the backward scattered light of fruit tissue.In this paper,Taking the plum as the research object,the polarization characteristics of the backscattered light on the surface of the plums and the forward scattering light of the cut plums are analyzed.In the experiment,the experimental platform for collecting backscattered light and forward scattered light respectively was built with a 650nm laser,a CCD industrial camera,a set of polarizer and bias detector.By taking pictures of light scattered form the surface of plum under various polarization directions,we offered an image processing program,and calculated the power distribution with angle,polarization degree and polarization angle of each pixel in the picture,in order to get the distribution of the whole polarization characteristics of the back-scattering light.The main research includes two aspects:on the one hand,it was studied that the polarization characteristics of scattering light distribution,and when the of incident angle and the polarization direction of the incident light changed,how the polarization characteristics of scattering light plum surface to change;on the other hand,linearly polarized light incidenced into the fruit,along the direction of propagation,how polarization characteristics of distribution was,and when the polarization direction of incident light changes,how the polarization state of forward－scattering light changes.The experimental results shows that linearly polarized light out from fruit tissue becomes partially polarized.The degree of polarization is Gauss distribution in horizontal and vertical directions.The change of the incident angle has little influence on the polarization angle of the scattered light.With the increasement of incident angle,the value of the degree of polarization becomes smaller,while the incidence angle decreases,and the value of the degree of polarization becomes larger.The polarization angle of the backscattered light on the plum surface is in inverse proportion to the polarization angle of the incident light.The polarization angle of the forward scattering light of the plum face is proportional to the polarization angle of the incident light.When the incident light is a pure P wave or a S wave,the polarization angle of the scattered light is the same as the polarization angle of the incident light.