Measurement of optical coefficients of tissue-like solutions using a combination method of infinite and semi-infinite geometries with continuous near infrared light

Abstract

This paper proposes a, new continuous wave (CW) method to measure the optical coefficients of a tissue-like solution by using a combination of infinite and semi-infinite geometries. Previous CW methods have required a long source-detector separation distance to distinguish the effects of absorption from scattering. This long separation distance results in inaccurate optical coefficients due to a low signal-to-noise ratio (SNR). A combination method is suitable for measuring optical coefficients of tissue-like solutions while using a short source-detector distance to increase the accuracy of the CW method. The measurement geometries are switched by an optical system, and light is detected at an avalanche photo-detector (APD). The absorption and reduced scattering coefficients are calculated from the slope and intercept values of a straight line derived from the fluence rate at several source-detector distances. The combination method provides an excellent separation performance between scattering and absorption with continuous'near infrared (NIR) light.