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Chlorophyll bearing plant tissue has a very unique spectral reflectance in the visible and near infrared (NIR) wavelengths. Attempts to use reflected sunlight, passing through optical filters in an attempt to distinguish between plants and other objects has proven inconsistent at best. Recently, equipment has been developed using an approach which provides discrimination equally well in bright sunlight, in shadows or in total darkness. It generates its own light from solid state light emitters which are modulated to isolate them from the sunlight. Problems associated with earlier attempts to accurately detect the presence of small amounts of plant tissue using spectral reflectance have thus been eliminated.