Figure 2.

(A) Absorptivity data for oxy- and deoxy-hemoglobin (downloaded from https://omlc.org/spectra/hemoglobin/); the inset shows two diffuse reflection spectra of fingertip and forearm skin as measured with a fiber optic probe. (B) Spectra of hemoglobin at different oxygenation rates; included is the absorbance spectrum of water at 10 mm pathlength. Also shown is the illumination irradiance (intensity normalized) for four LEDs with indicated halfwidths from Hamamatsu Catalog¹⁸ at selected center wavelengths, as mentioned by Segman.¹⁰