5:45 PM - 6:00 PM
[20p-H116-18] Spectral imagery measurement of chlorophyll fluorescence using oxygen A band: application to rice field
Keywords:chlorophyll fluorescence,oxygen A band,solar radiation
We report on a stand-off system that enables the observation of vegetation fluorescence under both laboartaory and field conditions. For field applications, the system enables the spectral measurement using a CCD spectrometer, together with the two-dimensional measurement of the fluorescence intensity distribution by means of a cooled CCD camera. A narrow-band optical filter centered at 760 nm, the wavelength of the oxygen A-band, is employed with the CCD camera to exploit the “solar blind” wavelength for the florescence measurement under daylight conditions. The most difficult aspect of the fluorescence detection is the quantitative separation between the fluorescence signal around 740 nm and the large reflection signal of vegetation leaves in the near infrared (NIR) spectral region. For realizing this separation, we have developed a LED-based light source, which is mostly free from the NIR radiation by utilizing a cyan filter. Under laboratory or night-time outdoor situations, this novel light source makes it possible to observe pure vegetation fluorescence without hinderance from large NIR reflection. In addition, the laser-induced fluorescence methodology is employed for obtaining the spectral shapes of fluorescence signals. The elimination of visible part of radiation, on the other hand, can lead to the measurement of the “pure” reflectance signal free from the effect of fluorescence. The combination of these spectral information makes it possible to implement the detailed analysis of solar radiation induced fluorescence signals. We describe the application of the system to rice field monitoring recently performed in the framework of CEReS joint research.