Blood Optical Properties' Dependance on Temperature

The optical properties of a material (including the coefficient of absorption, the coefficient of scattering, and anisotropy) are dependent on numerous factors including temperature. We are developing a system to measure the effects of blood component concentrations on these coefficients for human blood. Since our blood samples are exposed to a wider range of temperatures than those which occur in the body, this requires understanding of the relationship between temperature and optical properties. Our experiment design has included infrared light passing through an aperture, collimator, chopper, optical linear variable filter, and finally into a double integrating sphere with a sample inserted between the two spheres. Reflection and transmission magnitudes are collected using photodiodes and lock-in amplifiers to measure changes in transmission and reflection. Focusing on 1250nm light, we have found a 3% increase in transmission as the blood temperature increases from 14˚C to 35˚C. No change in reflection has been detected. Future plans include ensuring accuracy of the temperature reading of the blood as it is hit by the beam, performing scans using a wider range of wavelengths, as well as incorporating a second branch of our optical setup which will allow for two samples (at different temperatures) to be measured simultaneously.