Patent ID: 6563122
Filing Date: 2003-05-13
Classification: G01N

Abstract:
Fluorescence detection assembly for determination of relevant vegetation parameters comprising an excitation source (1) consisting in a low power laser device with an excitation wavelength in the red spectral region, a beam forming optical device (2), a dichroic beam splitter (5), a basic fluorescence detector system (3) including an entrance optical device (4) receiving fluorescence emission via said dichroic beam splitter (5) and an interference filter (10) blocking out the elastic back scatter signal, an electronic detection device (7) for detecting a fluorescence signal, andy an electronic trigger and timing device (6), characterized in that said low power laser device provided in the excitation source (1) is a high repetitive pulsed laser device with several nanosecond pulse length and a preferred excitation wavelength in the red spectral region of preferable 670 nm, in that said dichroic beam splitter (5) couples the formed excitation beam co-axially to the optical axis (9) of a receiver optic and directing this formed beam without optical waveguiding to a vegetation target subject to be investigated, in that said basic fluorescence detector system (3) forms an image of the excitation spot at the sensitive detector area, in that said electronic detection device operates at the doubled pulse repetition rate of said excitation laser source (1) and samples the active fluorescence signal synchronously with the laser emission on the one hand and the passive background signal with a fixed delay in the microsecond range before or after the active signal on the other hand, recording those signals by means of a fast sample and hold circuit coupled to an analog to digital converter which enables a digital signal processing, in that said electronic detection device (7) further comprises means for determining the pure fluorescence signal by subtracting the background signal from the active fluorescence signal electronically or in a post processing procedure, and in that said electronic trigger and timing device (6) synchronizes the laser pulses with the sample intervals of said electronic detection device (7).