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International Society for Industrial Process Tomography

5th World Congress on Industrial Process Tomography

Feasibility Study of NIR Diffuse Optical Tomography on Agricultural Produce

E.K. Kemsley1, H.S. Tapp1, R. Binns 3, R.O. Mackin3 and A.J. Peyton2

1 Institute of Food Research, Norwich Research Park, Colney, Norwich, NR4 7UA, UK

2 University of Manchester, School of Electrical & Electronic Engineering, Manchester, M60 1QD, UK

3 Lancaster University, Engineering Department, LA1 4YR, UK Email:


Background: Monitoring the quality of fresh fruit and vegetables benefits both the producer, by offering a competitive advantage, and consumers, by improving consistency and hence encouraging a more healthy and varied diet. Near infrared (NIR) spectroscopy is a candidate technology for monitoring agricultural produce quality. Here there has been a recent trend toward transmission- based geometries which interrogates deeper into the sample. NIR tomography is the natural progression of this, offering the possibility of detecting internal defects.

Objective: To evaluate a NIR tomograph built from relatively low-cost components.

Design: The tomograph comprised a stabilised VIS/NIR broadband source; a diode-array NIR spectrometer and a sample turn-table. The angular positions of the detector and turn-table could be moved independently of each other using two stepper motors under computer control. An experimental approach was adopted to generate a linear ‘difference image’ reconstruction matrix using 47 mm diameter potato cores and a 10 mm diameter black rod acting as an absorbing perturbation. The reconstruction matrix was generated using multiple linear regression and evaluated for the case of two perturbing rods.

Results: It was possible to produce images of a comparable quality to other soft-field tomographic techniques.

Conclusions: Although conducted under highly simplified conditions, the results suggest NIR tomography has potential for monitoring internal defects in agricultural produce.

Keywords Quality Control, Near-infrared, Food, Optical Tomography, Difference Imaging

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