Hyperspectral cameras designed to improve agricultural practices

A Duke University researcher is working on developing a small, inexpensive hyperspectral camera to enable worldwide precision agricultural practices thanks to a recently-awarded fellowship.

By Ken Kingery October 27, 2019

Maiken Mikkelsen wants to change the world by developing a small, inexpensive hyperspectral camera to enable worldwide precision farming practices that would significantly reduce water, energy, fertilizer and pesticide use while simultaneously increasing yields. While that goal sounds like a tall task for a simple camera, it’s been greenlighted by a 2019 Moore Inventor Fellowship.

“The Moore Inventor Fellowship is opening a new avenue of research to me,” said Mikkelsen, the James N. and Elizabeth H. Barton Associate Professor of Electrical and Computer Engineering at Duke University. “It is enabling me to explore new applications for my technology that could benefit the environment and mankind in a profound way.”

An artistic rendering of a new type of hyperspectral imaging detector. Depending on their size and spacing, nanocubes sitting on top of a thin layer of gold trap specific frequencies of light, which heats up the materials beneath to create an electronic signal. Courtesy: Jon Stewart, Duke University[/caption]

Mikkelsen and her team fashioned silver cubes 100 nm wide and placed them only a few nm above a thin layer of gold. When incoming light strikes the surface of a nanocube, it excites the silver’s electrons, trapping the light’s energy—but only at a certain frequency.

The size of the silver nanocubes and their distance from the base layer of gold determines that frequency, while controlling the spacing between the nanoparticles allows tuning the strength of the absorption. By precisely tailoring these spacings, researchers can make the system respond to any electromagnetic frequency they want.

To harness this fundamental physical phenomenon for a commercial camera, Mikkelsen and her colleagues have demonstrated a sort of “superpixel” – a pixel made from a grid of nine individual detectors each tuned to a different frequency of light. When any spot on the pixel’s grid captures its specific frequency, it heats up, which in turn creates an electric voltage in a layer of pyroelectric material sitting directly below it. That voltage is then read by a bottom layer of a silicon semiconductor contact, which transmits the signal to a computer to analyze.

A new type of lightweight, inexpensive hyperspectral camera could enable precision agriculture. This graphic shows how different pixels can be tuned to specific frequencies of light that indicate the various needs of a crop field. Courtesy: Maiken Mikkelsen and Jon Stewart, Duke University[/caption]

It is estimated that the process currently used to produce fertilizer accounts for up to two percent of the global energy consumption and up to three percent of global carbon dioxide emissions. At the same time, researchers estimate that 50 to 60% of fertilizer produced is wasted. Accounting for fertilizer alone, precision agriculture holds an enormous potential for energy savings and greenhouse gas reduction, not to mention the estimated $8.5 billion in savings each year, according to the United States Department of Agriculture.

Several companies are already pursuing these types of projects. For example, IBM is piloting a project in India using satellite imagery to assess crops in this manner. This approach, however, is very expensive and limiting, which is why Mikkelsen envisions a cheap, handheld detector that could image crop fields from the ground or from inexpensive drones.

“Imagine the impact not only in the United States, but also in low- and middle-income countries where there are often shortages of fertilizer, pesticides and water,” Mikkelsen said. “By knowing where to apply those sparse resources, we could increase crop yield significantly and help reduce starvation.”

Duke University


– Edited by Chris Vavra, production editor, Control Engineering, CFE Media, cvavra@cfemedia.com. See more Control Engineering discrete sensor and vision stories.

Author Bio: Ken Kingery, senior science communications specialist, Duke University