テラヘルツ分光分析の印刷分野応用の可能性 Feasibility of Terahertz Spectroscopic and Imaging Applications in Printing Industry
The technique of generation and detection of terahertz radiation using femtosecond laser as the excitation source has evolved into the "terahertz terahertz time-domain spectroscopy (THz-TDS). " Based on THz-TDS it is possible to measure complex refractive indices of various materials with an unprecedented precision. Since most of packaging materials, such as papers and plastics, are transparent to the THz radiation, non-destructive inspection of packaged products is considered as the one of the most promising applications of THz-TDS in the industry. In this review, followed by a brief explanation of the basic principle of THz-TDS, several examples of spectroscopy and imaging based on THz-TDS are presented to illustrate the feasibility of this technique for applying in the printing industries. The examples include detection of the paper fiber alignment, the see-through imaging of hand-writing impressions and an IC rail-pass, etc. A two-dimensional electro-optic sampling system, as the real-time THz imaging technique, and a fiber coupled photomixing emitter-detector system with a dual-mode semiconductor, as the cost-effective THz imaging system, are also described.
日本印刷学会誌 45(3), 130-137, 2008-06-30