Classification and screening of test subjects according to optical thickness of skin

The present invention relates to characterization of tissue. More particularly the invention relates to methods of classifying a live subject according to optical thickness of skin, utilizing noninvasive NIR spectroscopy techniques. A method for classifying live subjects according to optical thickness of the skin is based on noninvasive, near-infrared reflectance measurements on skin tissue. An indicator of skin optical thickness is derived through analysis of the water, fat, and protein marker bands in the near infrared spectrum. The skin thickness indicator may then be used to evaluate the suitability of the subject for calibration on a standardized set of optical probes. The optical probes in the standardized set are designed to cover a range of penetration depths by varying the distance distribution between illuminator and detector fibers on each probe tip.