DEVELOPMENT OF AN ACOUSTO-OPTIC TUNABLE FILTER BASEDPORTABLE HYPERSPECTRAL IMAGING SYSTEM

摘要

As the spatial resolution of airborne or spaceborne hyperspectral remote sensing imagery is notrntoo high, changes in reflectance of a pixel depend on the reflectance and the ratio of thernend-members constituting the pixel. In terrestrial ecosystem researches, to estimate the ratios ofrnthese constituents in such a mixed-pixel (or mixel), linear mixture model is often used whichrnrequires the reflectance of each of the end-members such as vegetation, soil and so on.rnFurthermore, it is important to define the vegetation spectrum for distinguishing amongrnvegetation group within a mixel. However, reflectance of vegetation is affected by canopyrnstructure such as ratio of sunlit and shaded leaves. Presently, a portable hyperspectral imagerrnwhich can spatially measure this situation hardly exists. We developed a portable hyperspectralrnimager, which operate in the wavelength range of 500nm to 1000nm with an interval resolutionrnof 5nm. This hyperspectral instrument consists of three main components, namely, (1) arnAcousto-Optic Tunable Filter can (AOTF), (2) a CCD camera and (3) a PC controller. Thernsystem is light and compact, and the spectral wavelengths, intervals and acquisition time arernprogrammable using in-built PC control. The hyperspectral image of canopies taken with thernsystem showed encouraging potential in the estimation of vegetation spectrum, area ratio ofrnsunlit and shaded leaves within a specific period. The developed AOTF-based hyperspectralrnimager is expected to provide valuable data and has great potential for further investigations inrnremote sensing of canopy structure and biochemical variables.