Visible to SWIR hyperspectral imaging for produce safety and quality evaluation

Abstract

Hyperspectral imaging techniques, combining the advantages of spectroscopy and imaging, have found wider use in food quality and safety evaluation applications during the past decade. In light of the prevalent use of hyperspectral imaging techniques in the visible to near-infrared (VNIR: 400–1,000 nm) for agro-food evaluations, seldom reported are the instrument artifacts that may affect the quality of image data. Furthermore, hyperspectral-based research has focused on the development of image processing and detection aspects with minimal attention given to illustrating the underlying value of imaging with sufficient spatial resolution in the regions spanning from the visible to short-wavelength infrared (SWIR: 1,000–1,700). We have developed multiple generations of line-scan based hyperspectral imaging systems and expanded the imaging capabilities in the SWIR. With the use of our most recently developed VNIR and SWIR hyperspectral imaging systems, spectral and spatial attributes of apples with defects from 400 to 1,700 nm are presented. In addition, we characterize the second-order effect in the 800–1,000 nm range that emanates from the use of a diffraction grating in the VNIR hyperspectral imaging system. We have devised methods to perform SWIR spectral calibration and to remove the bad pixels inherent to the SWIR InGaAs focal plane array used in the imaging system. We envision that hyperspectral imaging techniques will continue to play a significant role in the agro-food sector as critical research tools, and in further applications for rapid inspection of produce safety and quality.