レーザー誘起蛍光ライダーによる植物蛍光のスペクトルおよび寿命のリモートセンシング

抄録

We have developed two types of laser-induced fluorescence lidar, which are LIFS (laser-induced fluorescence spectrum) lidar and LIFL (laser-induced fluorescence lifetime) lidar. The LIFS lidar consisted of a pulse 355-nm laser for excitation of plant leaf pigments, a spectrometer covered the entire range of plant fluorescence from 300nm to 800nm and a gated intensified CCD array for detection. The synchronous detection was applied to detect the weak fluorescence even in daytime. The LIFL lidar was for measurement of the fast lifetime of chlorophyll a fluorescence in the order of nano-second and under. A 40 pico-second 532-nm laser was prepared for short time excitation. A detection system was especially designed to accommodate for the fast lifetime measurement using MCP-photomultiplier tubes and other fast-rise time equipments. Rise time of the LIFL lidar was estimated to be 196ps. For data analysis, convolution integration technique was applied to the lidar observation data. Their performance tests were done for trees naturally growing in outside. The LIFS lidar observation of zelkova tree leaves 20m away from the lidar showed change of the fluorescence spectra depending on the growth/senescence period which turned to growth information about production, accumulation, and disorganization of molecular pigments occurring inside the leaves. The LIFL lidar observation showed that the lifetime of chlorophyll a fluorescence of plane tree leaves 30m away from the lidar at sun-shined position decreased gradually from the morning to noon and had the lowest at 13:00, and increased in the evening. Variation of photosynthetic activity during one day might be able to be monitored. These results will offer a new technique and novel data for vegetation remote sensing.