This article presents an approach to the integration of a liquid crystal tunable filter into a monochrome video imaging system and provides a scheme for leveling the system response across wavelengths in the face of varying illumination, filtertransmittance, camera lens aperture settings, and gain response. The scheme developed here uses the filter attenuation control and the camera gain control, both of which can be controlled via software. This system was applied to the evaluation of vigor of bush bean plants grown under different nitrogen treatments (from 30 to 120 ppm N). Using plant images captured at 695 nm and 760 nm, a Normalized Difference Vegetation Index (NDVI) was computed for each plant canopy and showed a increasing trend withincreasing nitrogen treatments.
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