Near-infrared Imaging and Spectroscopy

Abstract

In the electromagnetic spectrum, near infrared (NIR) region covers between 780 nm to 2500 nm. The developments of new NIR techniques like NIR imaging (NIR cameras, NIR hyperspectral imaging systems), Fourier Transform (FT)-NIR spectroscopy, NIR microscopes, and NIR thermal cameras have extended the application of near infrared band dramatically in the last 3 decades, because some of these techniques give spectral as well as spatial data which help to analyze chemical constituents as well as physical and textural parameters of a sample. When an object is illuminated with light, it absorbs, reflects and transmits light at various proportions based on the physical and chemical properties of object. In near infrared imaging systems, this absorbed, transmitted or reflected radiation only at NIR waveband is captured using a NIR detector or sensor. In NIR hyperspectral imaging technique, the object is imaged over a large number of spectral bands and complete reflectance spectrum with spatial (imaging) data are collected. NIR spectroscopy techniques yields only spectral data, and in Fourier transform-near infrared, Fourier transform is applied to convert the raw data into original spectrum. Nowadays, near-infrared imaging and spectroscopy techniques are commercially used for measurement of moisture and other chemical constituents of the cereal grains and oilseeds in grain industry. Meat industry has also started using NIR techniques for non-destructive quality monitoring. The development of multispectral imaging systems based on the indented use, and developments in analysis techniques will help the agricultural and food industry in implementing the NIR imaging and spectroscopy systems for rapid and in-line quality monitoring applications like foreign material detection, discrimination of agricultural and food products based on quality attributes and detection of defects, diseases, and food adulteration.