Far-infrared spectroscopic device, and far-infrared spectroscopic method

A far-infrared spectroscopic apparatus comprising:

• a holding mechanism configured to be capable of holding a specimen in moist air;
• a detector configured to detect light obtained by emitting far-infrared light onto the specimen;
• and
• a signal processing unit configured to compute an absorption spectrum of the specimen f from the detector,
• characterized in that
• the signal processing unit
• acquires
• a first spectrum detected by the detector when the far-infrared light is emitted along a measurement optical path while a wavelength of the far-infrared light is changed, without the specimen being on the measurement optical path, and
• a second spectrum detected by the detector when the far-infrared light is emitted along the measurement optical path while the wavelength of the far-infrared light is changed, with the specimen being on the measurement optical path,
• calculates a difference in any of the first spectrum, the second spectrum, or a spectrum obtained based on the first spectrum and the second spectrum, at frequency intervals determined in accordance with a width of absorption peaks due to water vapor,
• selects frequencies of the absorption peaks due to water vapor in accordance with comparison between the difference and a threshold value, and
• executes data elimination for a signal of the first spectrum, the second spectrum, or the spectrum obtained based on the first spectrum and the second spectrum, based on the frequencies selected.