Orthogonally polarized terahertz wave imaging with real-time capability for food inspection

A terahertz imaging system operating at 0.3 THz has been developed for the purpose of detecting foreign substances in foods conveyed at a velocity of higher than 20 m/min. The imaging system has two Schottky barrier diode arrays which detect horizontally and vertically polarized terahertz waves independently and simultaneously. Experiments have shown that the imaging system can successfully obtain THz images with a diffraction limited resolution of 1 mm. It has also been shown that addition or subtraction of two images taken with perpendicularly polarized waves is effective to enhance the contrast of terahertz images.