Abstract
Our aim is to introduce middle-infrared spectroscopy into such daily life environments as smart toilets or
non-invasive glucose sensors. For this purpose, we proposed ultrasonic-assisted middle-infrared
spectroscopy to avoid strong water absorptions. By attaching an ultrasonic transducer to liquid cells,
ultrasonic standing waves (longitudinal waves) generate an internal reflection plane near the sample
surfaces. If we use an ultrasonic transducer whose frequency is 10 MHz, the depth of a generated
reflection plane from the sample surfaces is around 100 μm. We can easily make thin film samples inside
of moisture samples that are less than 100 μm thick. We also proposed a beam size (φ 6 mm × 20 mm)
for a middle-infrared spectrometer that is a kind of spatial phase-shift interferometer. Because we can
introduce a low-resolution middle-infrared camera (80×80 pixels) by maintaining wavelength
resolutions, we can achieve reasonably-priced sensors for commodities around 100,000 JPY.
