OPTICAL SENSOR HAVING A SELECTABLE SAMPLING DISTANCE FOR DETERMINATION OF ANALYTES

摘要

A method and apparatus for the measurement of trans-cutaneous diffuse reflectance at a single sampling distance for determining the concentration of an analyte in a biological sample, such as, for example, human tissue. The determination of the concentration of the analyte has been found to depend o n the sampling distance and reaches an optimal result at a defined sampling distance for a given analyte and a given sample. The method involves measuri ng the light re-emitted from the sample at a distance from a light introduction site and correlating the intensity of the re-emitted light to the concentration of an analyte. For a given sample, the distance between the light collection site and a light introduction site (i.e., the sampling distance) corresponds to the depth from the surface into the sample at which scattering and absorption events significantly affect the intensity of re- emitted light (i.e., the sampling depth). Prior knowledge about the sample determines the optimal sampling depth for performing a measurement for a specific analyte and the corresponding sampling distance needed to reach tha t optimal sampling depth. Optimization of the sampling distance, as well as th e correlation relationship, can be established in a calibration procedure.