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Date: 07/04 (Thu)
Time: 14:45-16:30
Place: Cosmo Studio
Speaker: Begzsuren Tumendemberel


Title:

The current status of fully automatic goniometer development and Spectro-Polarimetric BRF measurement of leaves

 

Abstract:

The reflectance of the leaf consists not only of its intensity but also of polarization, and the polarization techniques are generally used for separating specular reflectance from diffuse reflectance. The internal diffuse component of the spectral reflectance contains the details of the biochemical properties of the plant, an activity of photosynthesis, an expected amount of harvest, and water condition. Specular reflectance of the leaf strongly depends on a combination of the angle of incidence of the light source and the angle of observation view. The leaves look shiny at the shallow angle, where most of this reflection is polarized from the surface of leaves. Although the leaf spectral reflectance which is a point of convergence for many types of research, the study of spectral measurement with polarization in a individual leaf is largely unexplored. This study aims to connect the polarization techniques and the leaf Bidirectional Reflectance Distribution Function (BRDF) by separating specular and diffuse reflectance.

There are thousands of combinations of incident light and observation direction, due to this reason we built the automatic goniometer with Liquid Crystal Tunable Filter (LCTF) camera starting from the summer of 2016 in Hokkaido University. The laboratory half automatic goniometer is made at next room of 208, Graduate school of Science, HU and that room’s window is closed by dark curtains, which means the room is almost entirely dark. The laboratory and its equipment, including goniometer, control units, and sensor instruments covered with black absorbing materials to minimize diffuse irradiance scattering. The control system programmed the geometrical precision and the angular positioning accuracy of the goniometer and taken into account in the experimental design. Room temperature and humidity are monitored during BRDF data acquisition. Data acquisitions are software-based and automated to reduce operator-related errors. The imaging with the multispectral LCTF camera has a great advantage in measuring a selected leaf area with an arbitrary size of the field of view. 

Before 2019, our measurement tools were not fully automated, and additional development was required. Starting from this semester, we plan to do that all structure parts become metal and make it fully automatic in cooperation with Japanese Dream Factory (JDF), which is a metal parts manufacturing company. New spectro-polarimetric goniometer measures the 3D reflection of the target fully automatically. Now everything works really well with high accuracy.
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