Investigation Of Light Scattering Technique And Miniature Optical Sensor For The Measurement Of Airborne Particle

Light scattering measuring technique of airborne particle based on the principle of light scattering by individual particles is developed, i.e the flux scattered from the particle which is illuminated under definitely intensity incident beam in the air is proportional to the particle diameter. It is typically used to measure in real time the size and number of aerosol particles contained in a unit volume of air (i.e., cleanliness) and verification of cleanliness classin of clean environments , It is widely applied in electronic industry, pharmaceutical workplace, environment protection , inspection burean and science research department. After intruducing the application and development of OPC (Optical Particles' Counter) in this paper. Based on classical Mie's theory ,analysis the effect of particle diameters, index of refraction and incident wavelength on the the light scattered light intensity and provides the formula to calculate the scattered light flux in solid-angle,according to the formula of calculating scattered light intensity by single particle which is illuminated by a linearly polarized light. Results are compared with the condition illuminated by a unpolarized light.Illuminated by the different light source that has the equal light intensity,the scattered light flux collected by the two different scattered light collecting systems,which are often used in the airborne particle counter, is calculated. The result shows that their fluxes are equal on using the near-forward scattered light collecting system.On the contrary ,using right angle scattered light collecting system,they are not equal and illuminated by a lineary polarized light ,the collected light flux is connected with the angle between the center of detector and polarization. Calculating results ,based on MATLAB and worked out by the computer, indicate that the collected scattering light flux has extreme.when the angle is 90°or 270°between the center of detector and polarization. The results of experiment are consistent with the theoretical curve . Lastly ,miniature optical sensor, combined the near-forward and large aperture scattered light collecting system is designed .it has the advantages of a small volume light weight simple structure ,high resolution in particle diameter and high counting efficicency.