Vegetation Imaging - AGRI

Color imaging combined with NIR imaging has been extensively used to estimate plant health. Healthy plants reflect more near-infrared (NIR) light and absorb more visible light, particularly in the red spectrum, due to the presence of chlorophyll. By comparing the reflectance values in the red and NIR bands, indices like the Normalized Difference Vegetation Index (NDVI) can be calculated, providing a clear indicator of plant health and vigor. This imaging technique helps detect stress, disease, and nutrient deficiencies early, enabling timely interventions for better crop management and yield. However, soil moisture levels can affect the NDVI result, as well as it is prone to saturation - large change in vegetation density results in small change in NDVI. This is were normalized difference red edge index (NDRDI) becomes helpful, which utilizes the Red Edge band (730 nm) instead of the conventional Red band (650 nm). As a result it is better at picking up changes in chlorophyll content in later crop growing stages and able to detect variation in crop health, better than NDVI when there is more canopy (penetrates deeper and lower saturation level).

Images of a number of leaves both visibly healthy and with defects were taken using a MSLED-AGRI-2-4 illuminator with four spectral channels (i) 580 nm, (ii) 660 nm (red), (iii) 735 nm (red edge), and (iv) 820 nm (NIR). Images were captured using MSC2-AGRI-1-A camera with matching spectral bands. Color images of the leaves were taken using iphone 12.

Images of each individual band reveal different spectral features of the leaves.