Patent ID: 7263394

Claim:
A method for optically measuring a glucose level of a subject, comprising: guiding optical radiation in both a first propagation mode and a second, different propagation mode through a common optical waveguide towards a skin of a subject under test; reflecting radiation in the second propagation mode away from the skin without reaching the skin at a first location; directing radiation in the first propagation mode to interact with the skin to produce returned radiation from the interaction; overlapping the radiation in the second propagation mode and the returned radiation in the first propagation mode at the first location to co-propagate with each other; adjusting a relative delay between the returned radiation in the first propagation mode and the radiation in the second propagation mode to allow a portion of the returned radiation in the first propagation mode that is produced at or near an interface between the epidermis and dermis of the skin to optically interfere with the radiation in the second propagation mode to obtain a first optical measurement; adjusting a relative delay between the returned radiation in the first propagation mode and the radiation in the second propagation mode to allow a portion of the returned radiation in the first propagation mode that is produced at or near an interface between the dermis and the subcutaneous layer of the skin to optically interfere with the radiation in the second propagation mode to obtain a second optical measurement; and using a ratio between the first and the second optical measurements to obtain a measurement of the glucose level in the dermis.