Design, characterization, and implementation of Diffuse Reflectance Integrating Ellipsoids (DRIE) for spectroscopic analysis

Abstract

Integrating ellipsoids in diffuse reflectance spectroscopy is unusual; few are constructed in just one piece. In diffuse reflectance spectroscopy, integrating spheres are used to determine the optical properties of biological tissues in diagnosis or disease detection. The disadvantages of using integrating spheres in the biological field lie in the dimensions of their apertures, which, being small, prevent the analysis of a complete biological tissue or organ. In this work, we propose the construction, calibration, and use of diffuse reflecting integrating ellipsoid (DRIE) for spectral analysis, elaborated as a body without couplings, not implemented so far for clinical diagnosis. A hyperboloid calibrator was designed and coupled to the ellipsoid to measure the volumetric spectra of samples instead of thin samples with small surfaces to measure whole organs or samples with larger sizes than habitual. We developed a radiometric theory for the ellipsoid using the shape factor to calculate its flux or radiant energy. With spectra acquired by the device from different chicken tissues (brain, bone, muscle, digestive tract, and skin) and with support vector machines (SVM), spectra of the tissues were classified for dimensions from 19.14 mm2 to 4600 mm2, resulting in a correlation (0.98), demonstrating the high sensitivity and low noise of our device to classify.