Spectral line discriminator for passive detection of fluorescence
AssigneeAerodyne Research, Inc.
InventorPaul L. Kebabian
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Abstract
A method and apparatus for detecting fluorescence from sunlit plants is based on spectral line discrimination using the A-band and B-band absorption of atmospheric oxygen. Light from a plant including scattered sunlight and the fluorescence from chlorophyll is passed through a chopper into a cell containing low-pressure, high-purity oxygen. A-band or B-band wavelengths present in the light are absorbed by the oxygen in the cell. When the chopper is closed, the absorbed light is remitted as fluorescence into a detector. The intensity of the fluorescence from the oxygen is proportional to the intensity of fluorescence from the plant.
Claims30
A method of detecting fluorescence in the A-band or the B-band from a sunlit target, the method comprising the steps of:
- A. passing light comprising the A-band or B-band fluorescence into a cavity containing oxygen gas,
- B. periodically interrupting passage of the light into the cavity;
- and
- C. detecting fluorescence by the oxygen gas while the passage of the light into the cavity is interrupted so as to provide an output indicative of the fluorescence in said A-band or, B-band.
An apparatus for detecting fluorescence in the A-band or the B-band from a sunlit target, the apparatus, comprising:
- A. a cavity containing oxygen gas
- B. means for directing light from the target into the cavity;
- C. means for periodically interrupting light into the cavity;
- and
- D. a light detector positioned to sense fluorescence by the oxygen gas and there by provide an output indicative of the fluorescence in said A-band or B-band.
Dependencies are inferred from the claim text.