| 摘要 |
THz waves 4 on two different wavelengths are generated within a frequency range of about 0.5 to 3 THz, and a subject matter 10 is irradiated with the THz waves on two wavelengths to measure their transmittances, and thus the presence of a target having wavelength dependence on the absorption of the THz wave is detected from a difference of their transmittances. Furthermore, a surface of the subject. matter is scanned two-dimensionally with each of the THz waves on two different wavelengths, and an image of a position where the transmittances of the two wavelengths differ is displayed two-dimensionally.
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