We separated the component spatial patterns of frequency-dependent absorption in chemicals and frequency-independent components such as plastic, paper, and measurement noise in terahertz (THz) spectroscopic images, using known spectral curves. Our measurement system, which uses a widely tunable coherent THz-wave parametric oscillator source, can image at a specific frequency in the range 1–2 THz. The component patterns of chemicals can easily be extracted by use of the frequency-independent components. This method could be successfully used for nondestructive inspection for the detection of illegal drugs and devices of bioterrorism concealed, e.g., inside mail and packages.
© 2003 Optical Society of America
Yuuki Watanabe, Kodo Kawase, Tomofumi Ikari, Hiromasa Ito, Youichi Ishikawa, and Hiroaki Minamide, "Spatial Pattern Separation of Chemicals and Frequency-Independent Components by Terahertz Spectroscopic Imaging," Appl. Opt. 42, 5744-5748 (2003)