A pathlength corrected spectrophotometer for tissue examination includes an oscillator for generating a carrier waveform of a selected frequency, an LED light source for generating light of a selected wavelength that is intensity modulated at the selected frequency introduced to a subject, and a photodiode...http://www.google.com.au/patents/US5564417?utm_source=gb-gplus-sharePatent US5564417 - Pathlength corrected oximeter and the like
