Characterization and optimization of an integrating sphere based detector for the estimation of tissue optical properties

An integrating sphere system has been developed to non-invasively study the optical properties of biological tissues over a broad spectral range. Using the integrating sphere as both a diffuse illumination source and a detector provides a technically simple measurement apparatus with numerous advantages. A primary advantage is the reduction of the effect of spatial inhomogeneities on the determination of optical properties, afforded by the increased area of detection through the port-opening of the sphere, which challenges many fibre-based, spatially-resolved measurements. Through a single measurement of total diffuse reflectance, an estimation of the transport albedo of homogeneous, liquid phantoms can be made for those cases where scattering is greater than a determined threshold. Further estimations can be made to describe the absorption environment. The effects of the sphere geometry, particularly port-opening size, on the accuracy of the estimated optical properties will be discussed. These results will be used to modify the design of the integrating sphere as an efficient illuminator and light collector, in order to optimize its use in determining the optical properties of biological tissues. © 2007 SPIE-OSA.