  This work demonstrates a non-contact diffuse reflectance approach with a
working distance of ~1.1 meters for the potential of glucose sensing.
Non-contact diffuse reflectance over 1.1-1.3 micrometers was developed
according to a center-illumination-area-detection (CIAD) geometry. The modeled
response of diffuse reflectance in the CIAD geometry was examined with phantoms
by altering independently the size of the collection geometry and the reduced
scattering and absorption properties of the medium. When applied to aqueous
turbid medium containing glucose control solutions with the cumulative volume
varying over three orders of magnitude, a linear relationship expected for the
diffuse reflectance as a function of the medium absorption/reduced-scattering
property was observed for four conditions of the glucose-medium composition
that differed either in the effective glucose concentration or the host medium
scattering property. The cumulation of glucose up to 17.8mg/dL and 8.9mg/dL in
the host medium having the same optical properties resulted in linear
regression slopes of 0.0032 and 0.0030, respectively. The cumulation of the
glucose up to 17.8mg/dL in an aqueous host medium that differed two folds in
the reduced scattering property caused the linear regression slope to differ
between 0.0032 and 0.0019. The R^2 values of all cases were all greater than
0.987. A provisional patent (US#63/053,004) has been obtained for this work.
