A simple accurate algorithm for the critical angle refractometer

Junwei Ye; Luo Tao; Kecheng Yang; Min Xia; Wei Li; Wenping Guo; Hao Liu

doi:10.1117/12.2034666

19 September 2013 A simple accurate algorithm for the critical angle refractometer

Junwei Ye, Luo Tao, Kecheng Yang, Min Xia, Wei Li, Wenping Guo, Hao Liu

Proceedings Volume 8905, International Symposium on Photoelectronic Detection and Imaging 2013: Laser Sensing and Imaging and Applications; 89051U (2013) https://doi.org/10.1117/12.2034666
Event: ISPDI 2013 - Fifth International Symposium on Photoelectronic Detection and Imaging, 2013, Beijing, China

Abstract

We present a fast, simple, sub-pixel algorithm on the critical angle refractometer to measure the refractive index of the liquid sample by determining the centroid of the light intensity of the relative reflective curve. The centroid algorithm utilizes a divergent fiber-coupled royal blue LED source to irradiate on the dielectric surface between the prism and the media, which generates the light intensity distribution of the reflectance facula. Instead of the critical angle pixel as the differential algorithm and the threshold algorithm, the sub pixel centroid algorithm is based on calculating the centroid value of the light intensity of the relative reflective curve. In some moderate turbid solutions, the centroid algorithm is less sensitive to the scattering and absorption than the differential algorithm and the threshold algorithm. It is possible to utilize the centroid point of the relative reflective curve to determine the refractive index. Supported by the theoretical analysis and experimental results on saline solutions, we can conclude that the proposed algorithm is effective to get the super resolution and meaningful to the refractive index measurement of the liquid. The critical angle refractometer with this centroid method is potential to be a high-accuracy, high-resolution, and reliable automatic refractometer.

Citation Download Citation

Junwei Ye, Luo Tao, Kecheng Yang, Min Xia, Wei Li, Wenping Guo, and Hao Liu "A simple accurate algorithm for the critical angle refractometer", Proc. SPIE 8905, International Symposium on Photoelectronic Detection and Imaging 2013: Laser Sensing and Imaging and Applications, 89051U (19 September 2013); https://doi.org/10.1117/12.2034666

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KEYWORDS

Reflectivity

Liquids

Algorithms

Refractive index

CCD cameras

Prisms

Absorption

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