Using near infrared measurement of water content as a cue for detecting biological materials

Abstract

This paper uses the spectral characteristics of water as a cue to detect biological materials in a scene. The spectra of a wide variety of materials were measured; most of the biological materials showed a spectral feature corresponding to the absorption peak of water at 962 nm. A machine vision system that used two narrowband near infrared light sources and a conventional CCD camera is described. The ability of the system to detect biological material is demonstrated in a series of examples. Water content is not an infallible indicator that a material is biological-wet inanimate surfaces will give a false positive, and some tissues are surrounded by highly scattering, impermeable layers that conceal internal water. Nonetheless, in this paper, we will show that many tissues do give a strong response to this feature and dry, nonbiological materials do not.