Abstract
We have developed a detection method of the state of water using near-infrared light-absorption. In this paper, a new evaluation index of the frozen state of water is proposed. In this case, we focused on the light-absorption characteristics of water. The experimental results showed that the absorption peak shifts to longer wavelength when the water state changes into ice state. To remove the affect of the scattering by bubbles generated in the freezing process and the thickness of the water layer, we have proposed a new evaluation index based on absorbed light intensity ratio at two wavelengths. The index is constant even when the layer thickness changes from 1mm to 3mm and is not also affected by light scattering. This result indicates that the proposed evaluation index can be used as a criterion to detect the liquid phase (water state) or the solid phase (ice state). It has been confirmed that the method using the index is effective for monitoring the water freezing process with supercooling by the experiment.
