The effect of light losses in double integrating spheres on opticalproperties estimation

摘要

The double integrating sphere setup (DIS) measures diffusenreflectance, diffuse transmittance and collimated transmittance, fromnwhich the optical properties of tissue (the absorption coefficient Μna, the scattering coefficient Μs and thenanisotropy of scattering g) are estimated. The effect of light losses innthe DIS and optical thickness on optical properties estimation by theninverse adding doubling algorithm (IAD) and uniqueness of measurementnhave been investigated using a Monte Carlo method. Results were obtainednfor optical properties in turbid tissues (0.80⩽albedo⩽0.99,n0.80⩽anisotropy⩽ 0.99, 1.5⩽optical thickness⩽7.5)nsandwiched between glass slides. At optical thickness=6.0 the loss ofnlight through the glass slides is ranging from 13%±0.5% (atnalbedo=0.80) to 15%±0.5% (at albedo=0.98) of the incident power.nThe loss of light at the exit port in the transmittance sphere isnincreasing up to 50% of the incident power at highly forward scattering.nThese losses result in a dependency on optical thickness of the opticalnproperties estimation by the IAD algorithm. Furthermore, because ofnthese losses, the DIS setup measurement is found to be fundamentallynnonunique, when simultaneously measuring the diffuse reflectance,ndiffuse transmittance and collimated transmittance