Reduction of NIRS near-surface sensitivity using two detectors

A 1-source and 1-detector system commonly used in NIRS (near infrared spectroscopy) has considerable sensitivity in the near-surface region, which makes the measurement sensitive to skin blood flow and the thickness of the intervening tissue. This report proposes a 1-source and 2-detectors system in which logarithmic output of the 2-detectors are subtracted, giving the suppressed sensitivity in the near-surface region.