Patent ID: 8145286

Claim:
A device for optically measuring a test substance in blood by using a nail as an optical window which comprises: (i) a nail plate evaporation device, which partly removes a nail plate by evaporating the nail plate for creating an optical window in the nail, which comprises (a) a light generator generating a coherent light, (b) an evaporation depth monitor having a light detector detecting fluorescence emitted from the nail plate and the dermis for monitoring evaporation depth of the nail plate, and a controller which processes the detected fluorescence to determine evaporation depth information of the nail plate for controlling the light generator; (ii) an irradiator configured to apply light within a wavelength range for measuring absorption by the test substance through the optical window; (iii) a detector configured to detect light diffused/reflected from or transmitted through the body of a subject; (iv) a processor configured to process a signal obtained by the detector to convert the signal into a concentration of the test substance; (v) a monitor configured to monitor a water content and a keratin content of the nail by using light within a wavelength range for measuring absorption by water in the nail and light within a wavelength range for measuring absorption by keratin in the nail to correct or eliminate optical characteristics of the nail plate in the detected light.