We propose and demonstrate a novel technique, which we term bifocal optical coherence refractometry, for the rapid determination of the refractive index of a turbid medium. The technique is based on the simultaneous creation of two closely spaced confocal gates in a sample. The optical path-length difference between the gates is measured by means of low-coherence interferometry and used to determine the refractive index. We present experimental results for the refractive indices of milk solutions and of human skin <i>in vivo</i>. As the axial scan rate determines the acquisition time, which is potentially of the order of tens of milliseconds, the technique has potential for <i>in vivo</i> refractive-index measurements of turbid biological media under dynamic conditions.
© 2003 Optical Society of America
(120.5710) Instrumentation, measurement, and metrology : Refraction
(170.4580) Medical optics and biotechnology : Optical diagnostics for medicine
(170.7050) Medical optics and biotechnology : Turbid media
(180.1790) Microscopy : Confocal microscopy
(180.3170) Microscopy : Interference microscopy
Sergey A. Alexandrov, Andrei V. Zvyagin, K. K. M. B. Dilusha Silva, and David D. Sampson, "Bifocal optical coherenc refractometry of turbid media," Opt. Lett. 28, 117-119 (2003)