the present invention concerns an optical based pulse oximetry device comprising : first , second and third light emitting means , for placement on the skin surface of a body part to inject light in a tissue of said part , the wavelengths of the light emitted by said second and third means being different from each other light detecting means located at a relatively short distance from said first light emitting means and at relatively long distance from said second light emitting means and said third light emitting means , for collecting at the skin surface light of said emitting means having travelled through said tissue , first computing means for denoising the output signals of said long distance light detecting means from the output signals of said short distance light detecting means , and second computing means for deriving oximetry measurements from the denoised output signals of said long distance light detecting means .