Lab-in-a-Phone: A lightweight oblique incidence reflectometer based on smartphone

Abstract

In this letter, we present a compact and low cost smartphone based oblique incidence reflectometer (OIR) for the measurement of tissue optical properties in vitro. The proposed lightweight OIR system obliquely delivers a narrow laser light by the attached inexpensive laser diode onto the surface of the matter under test. The incident laser light produces a spatial distribution of diffuse reflectance which is not centered at the point of incidence. The built-in CMOS image sensor in the smartphone samples the relative profile of diffuse reflectance. The profile is rapidly and efficiently processed through a custom-developed smart application running on the phone for calculating the absorption coefficient and the reduced scattering coefficient. Phantom experiments have demonstrated the proposed OIR can achieve a measurement error less than 5% benchmarked with the bulky and expensive laboratory setup. Measurement results can either be stored locally for real-time application or sent to cloud, providing remote diagnosis opportunities even in the field settings.