Fig. 3.

Schematic illustration of the proposed method with combined use of the multidistance optode arrangement and the short-circuited light elimination method. For eliminating short-circuited light from the source to detector optodes at S-D pairs of 15 mm distance, polarizers P1 and P2 were arranged in orthogonal directions with each other. $r_s^{30}(t)$ and $r_s^{15}(t)$, transmittances of optode–scalp gaps at source optodes of 30 mm and 15 mm distance from the detector optode, respectively; $R^{30}(t)$ and $R^{15}(t)$, transmittances of head tissues when S-D pairs of 30 mm and 15 mm were used, respectively; $r_d(t)$, transmittance between the detector optode and scalp surface; $\Delta A^{30}(t)$ and $\Delta A^{15}(t)$, absorbance changes when S-D pairs of 30 mm and 15 mm were used, respectively.