Spectrophotometric apparatus for the non-invasive determination of glucose in body tissues

Claim 1

Apparatus for carrying out the method of transcutaneous non-invasive determination of the substance glucose in subject by measuring the optical near infra red absorption of the substance in regions of the spectrum where the typical absorption bands of the substance exist, and comparing the measured values with reference values from regions of the spectrum where the substance has insignificant or no absorption, the apparatus comprising a light source (1, 3, 5, 8) for applying a light beam (9) to a portion of a subject's body, said light having a spectral composition such that it can penetrate through the skin to a region where the substance concentration, is measured, a reflected light collecting means (13, 24) and detector means (15, 26) for detecting and converting the collected light into electrical signals, and computing means (30, 31,32,33, 35) to transform the electrical signals into an absorbance difference from which readouts representative of the substance concentration are obtained, characterized in comprising means (21) for varying continuously or stepwise the incidence angle of said beam (9, 22) or light relative to the body, said variation resulting in a consequent variation of the depth of said region under the skin surface of interest wherefrom the light (28g) is collected after absorption.