Field quantification of plant chlorophyll content using Google Glass

Quantification of plant health is crucial for agriculture and can even be used to monitor environmental factors and climate related changes. Plant health is known to be directly related to the chlorophyll content of leaves, which correlates with the capacity of the leaves to transmit or absorb light. The gold-standard method for measuring the chlorophyll concentration of a leaf is based on chemical extraction, which is complex, destructive and time-consuming. As an alternative, here we present a field-portable, cost-effective, and colorimetric method to quantify the chlorophyll content of leaves using Google Glass. For this purpose, we created a custom designed handheld device which is battery-powered and 3D-printed to separately provide uniform illumination of a selected region of interest on the leaf surface using red and white light-emitting-diodes (LEDs). The design of this device minimizes the interference of ambient light conditions to our chlorophyll measurements performed through the Glass camera. We tested this platform by using fifteen randomly selected plant species from UCLA Botanical Garden and imaging fully-grown leaves of these species using Glass. An image-processing algorithm was developed to process the acquired images and obtain the chlorophyll concentration information using the red channel intensities in our region-of-interest for both the white and red LED illumination conditions. The results obtained by this algorithm are in good agreement with the SPAD indices measured for each plant, demonstrating that Google Glass, in combination with our custom-designed illumination platform, can expand its functionality to be used as a chlorophyll meter in field-settings.