 Pulse oximetry is a non-invasive clinical technique that utilizes collimated light transmission in order to measure oxygen saturation.Two wavelengths are passed through a thin piece of tissue (earlobe or fingertip) and a photodetector on the other side detects the transmission at each wavelength.Due to the changing absorbance at varying wavelengths, it is possible to derive the absorbances due to arterial blood and exclude absorbances due to venous blood, skin, etc.