Abstract: An imaging fluorometer is described comprising a source of electromagnetic radiation, optical components to direct the radiation, excitation and emission filters, and an imaging device. The fluorometer is used to obtain images of the fluorescence emitted by illuminated arrays of photosynthetic components, such as those found in leaves. These fluorescence images, in turn, are used to construct an image of the photosynthetic efficiency of the array. Because efficiency in plants depends on the physiological state of the leaf, the fluorometer affords a method for the sensitive and rapid characterization of freeze damage, herbicide damage, and disease damage to plants. Moreover, the fluorometer may be used in robotic applications, as well as for remote sensing from a location distant from the plant.