Abstract: A filament inspection system is disclosed that gathers empirical data on the physical and chemical properties of filament. The illustrative embodiments need only a single video camera and two mirrors to image all of the exterior surfaces of one or more filaments simultaneously. These images can be used to analyze the physical properties of the filament. Furthermore, the illustrative embodiments need only a simple electrical network to gather empirical data on the permittivity of each segment of filament, which gives insights into the chemical properties of the filament. For example, embodiments of the present invention are particularly well suited for inspecting fiber-reinforced thermoplastic filament, and variations in the number, dispersion, wetting, and length of the fibers are all observable in variations in permittivity.