Double-integrating-sphere system to measure the optical properties of turbid samples

We have assembled a double-integrating-sphere system to measure the absorption (μ_a) and reduced scattering (μ'_s) coefficients of materials with high turbidity. We have employed the Inverse Adding-Doubling (IAD) algorithm to access these optical properties. The experimental system is a homemade setup assembled with broadband sources and 3D printed spheres, equipped with an optical fiber bundle for excitation and a spectrometer for detection. We have used a reference phantom (polyurethane plus Titanium Dioxide) with known optical properties at 633 nm (μ_a= 0.0019 mm^-1 and μ'_s= 0.477 mm^-1 ) to validate the system. The system can reliably measure the optical properties of turbid samples from 400 to 950 nm with one of the experimental setups and from 950 to 1650 nm with a second experimental setup.