A Handheld Multispectral Sensor for the Separation of Scattering and Absorption Properties

Abstract

Optical measurements are influenced by both the effects of light absorption and scattering. In this research, spatially resolved spectroscopy (SRS) was used in combination with a metamodel approach to separate scattering and absorption information in a non-destructive way. To this end, a cost-efficient, portable and robust multispectral sensor was designed. Four laser modules at carefully selected wavelengths (533.3 nm, 674 nm, 800.7 nm and 981.1 nm) were mounted on four sides of a CCD camera, while a light-weight lithium-ion battery was used as power supply. Using this sensor, 49 liquid optical phantoms, based on Naphthol Blue Black and Intralipid, were measured. As a reference, the bulk optical properties (BOP) were measured accurately using a double integrating spheres (DIS) setup. Combining these reference optical properties with the corresponding SRS measurements, a metamodel was built and validated on a separate test set of 7 liquid phantoms. The bulk absorption coefficient µa and the reduced scattering coefficient µs’ were successfully estimated based on SRS measurements, with R2V values of 0.97 and 0.94 for respectively µa and µs’. This type of portable sensor could be used for on-field or on-site measurements in the agro-food sector to measure the absorption and scattering properties and extract information on the physical and chemical product properties.status: accepte