School of Energy and Environment, Southeast University

The rainbow technology is widely used for liquid parameter measurement. However there are few studies on liquid absorbance at present. A novel technique based on the geometrical optics, Mie theory and Bouguer law for measuring refractive index, radius and absorbance simultaneously was presented. A charge-coupled device(CCD) camera was used to detect the scattering intensity distribution arising from the liquid column illuminated by a laser beam. The frequency of Ripple bows, position and intensity of the maximum peak were used for multi-parameter calculation. Stable liquid column at the capillary export was chosen for experimental research to avoid the measurement error from nonsphericity of the falling droplets. The result shows that the frequency of Ripple bows couldn’t be determined correctly when the Ripple bows are thoroughly destroyed by noise. Therefore the radius result has large error. On the contrary, accuracy result can be obtained when the signal to noise ratio of Ripple bows is high. A linear relationship between volume concentration of red ink and the absorbance is illustrated. And the lower detection limit of absorbance is as low as 10-5.