Patent ID: 6868285

Claim:
A method for the non-invasive determination of a concentration of a substance in a body fluid in a body tissue by Raman spectroscopy comprising the steps: a) irradiating monochromatic primary light of a first wavelength into the body tissue, b) recording secondary light that is back scattered by the body tissue and storing the intensity of the secondary light in a first memory according to its wavelength as a first Raman spectral signal for the first primary wavelength, c) irradiating monochromatic primary light of a second wavelength into the body tissue, d) recording secondary light that is back scattered by the body tissue and storing the intensity of the secondary light in a second memory according to its wavelength as a second Raman spectral signal for the second primary wavelength, e) comparing the first Raman spectral signal in the first memory with the second Raman spectral signal in the second memory and generating a compare signal in which spectral structures caused by the body tissue are substantially eliminated, f) determining an intensity of the compare signal at at least one sample wavelength for which the intensity corresponds to the concentration of the substance in the body fluid, wherein the primary light of the first and second wavelength is irradiated with a preset irradiation frequency and each Raman spectral signal is recorded with said irradiation frequency.