Triple Bandpass Filters Improve Crop Health Monitoring

Triple Bandpass Filters are tools that allow users to go above and beyond traditional Normalized Difference Vegetation Index (NDVI) indicators to reinvent the way crop health is monitored and to collect more information than ever before. Traditionally, true NDVI was used to determine plant health, which incorporates a camera with a red and (near-infrared) NIR filter and the equation NDVI = (NIR – Red) / (NIR + Red).

While this is a great tool, scientific advances have found that modifying this calculation can provide even more details about crop and field health. Similarly to red light, healthy plants also absorb visible blue light. And in addition to NIR light, healthy plants also reflect some visible green light.

With this knowledge, MidOpt designed two new Triple Bandpass Filters, which allow one camera to gather data results at all three wavelengths, making them an affordable, lightweight alternative to aerial surveillance applications that otherwise might require three or more cameras or sensors.

TB550/660/850 GREEN + RED + NIR
The TB550/660/850 filter takes traditional red and NIR measurements to a new level by adding green. Green + Red + NIR wavelengths are used for applications where Chlorophyll Vegetation Index (CVI), Normalized Green (NG) and other vegetative index monitoring is needed. Two of the calculations used are as follows:

CVI = (NIR x Red) / (Green ^ 2)
NG = Green / (NIR + Red + Green)

TB475/550/850 BLUE + GREEN + NIR
Using Blue + Green + NIR light instead of the red-based method is recognized as the Enhanced Normalized Difference Vegetation Index (ENDVI), a technique that can provide more detailed information. ENDVI may better isolate plant health indicators and can generate results and false color mapping to indicate values as far down as the pixel level. The ENDVI formula is as follows:

ENDVI = ((NIR + Green) – (2 x Blue)) / ((NIR + Green) + (2 x Blue))