Compact Fluorosensor for Close-Range Remote-Sensing Characterization of Fruits

The ripeness of fruits is commonly assessed by the visual appearance, but this method is not very accurate and there can be a large variability. We have developed a hand-held sensor based on laser-induced fluorescence to provide more objective guidance. The instrument incorporates a 412 nm continuous wave semiconductor laser and a miniature spectrometer. It was used for monitoring of tropical fruits growing on the tree, and high-quality spectra could be recorded at ranges of 1-2 meters. The spectra feature characteristic dual-peaked emission peaks in the near-IR region due to chlorophyll, as well as blue-green signals due to further pigments. Further, natural waters were studied and showed strong differentiation effects.