Feasibility of a newlydeveloped size determination method for sub − micrQn particles using rnulti − wavelength polarized lights is investigated , experimentally . According to the Mie ' s theory the polar 正 zation ratios of scattered 監 ights are calculated nurnerically , which is a function of the part 王 cle diameter , the refraction index , and the wavelength of the incident light . Polystyrene particles are used as the test particles , which are suspended in pur 伍 ed wa 亡 er . The arithmetjc

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... ean diameters of them are varied from O. 356 to O . 77 Fm , which is measured with a centrifugal sedimentation method . In order to extend the measurement range of convestional polarization ratio methods , three kinds of He − Ne lasers , whose wavelengths are 543. 5, 594. 1, and 632. 8nm , are used . The laser beams passes through the particles , and the scattered images are acquired with a digital CCD camera set in parallel and perpendicular directions to the polarization plane of the incident light . The polarization ratios of the scattered lights are estimated from these scattered light images , and the acquired data are compared with the analytical values . It is shown that , by use of the multi − − wavelength polarization ratio method , the measurement range of the particle size can be extended up to the order of 1 FLm, and that the accuracy of the results lies from O. 1% to 7 . 6 % , when compared with the results of a centrifugal sedimentation method .