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Date: 11/14 (Thu)
Time: 14:45-16:30
Place: 8-1-03
Speaker: Begzsuren Tumendemberel

Title: Optical property of leaves and study of Spectro-Polarimetric leaf BRDF

Abstract:

  Leaves are a provider of the most fundamental needs of life on earth. Techniques of vegetation canopy identification are now well developed based on multispectral imaging which allows determining various things from space such as their positioning, density of plant biomass, invasive vegetation, mapping of deforestation, and the health of the plant. These applications based on a property of the leaf spectral reflectance which is a point of convergence for many types of research. The main part of this study is the individual (single) leaves, and it needs to know optical properties. This EOU seminar will present more on what is the fundamentals of an optical property of leaves, and it introduces what kind of research is progressing related to directional spectral and polarization properties.

The reflectance of the leaf can describe not only regarding its intensity but also in terms of its polarization and polarization techniques are generally used for separating specular reflectance from plant's biochemical properties, the amount of harvest, dry matter, and water. 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 both. The leaves look shiny at the shallow angle, 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 the single leaf is largely unexplored. This work aims to connect polarization techniques and directional relations of the leaf Bidirectional Reflectance Distribution Function (BRDF) by differentiating specular and diffuse reflectance. To do this, individual several leaves were captured by and Liquid Crystal Tunable Filter (LCTF) camera in the wavelength range of 460-780 nm with a linear polarizer. The advantage of using an image of the multispectral LCTF camera able to crop surface area of a leaf that means it can select an arbitrary size of the field of view and to identify leaf area. There are thousands of combinations of incident light and observation direction in single leaf BRF measurement, due for this reason we have been building the automatic goniometer with LCTF camera in a laboratory.

For experimental physic or experimental science, cutting edge technologies and accurate measurement technologies have always been new scientific discoveries and the beginning of new things. We used the spaceborne hyperspectral camera with LCTF to measure the bidirectional reflectance factors of an individual leaf in a laboratory using an automatic goniometer system. Although using LCTF camera was a great advantage of this work, the automatic goniometer system we are using needs more development. Furthermore, it is necessary to measure the spectro-polarimetric property of other surfaces such as soil, rock, sand, snow, ice, and so on.

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