Researchers develop a miniaturized holography instrument that is being used on drones
ADELPHI, Md. -- An Army researcher along with university partners developed a miniaturized holography instrument that is being used on unmanned aerial vehicles to safely and efficiently capture images for the detection and characterization of aerosols, contributing to the situational awareness and lethality of Soldiers.
The instrument, called the holographic aerosol particle imager, or HAPI, has the unique ability to image multiple particles freely entering its sensing volume from any direction via a single measurement. Using digital holography, the instrument obtains the images in a non-contact manner, resolving particles larger than ten micrometers in size in a sensing volume of approximately three cubic centimeters.
The construction of HAPI consists of 3D printed polymer structures that enable a sufficiently low size and weight that it may be flown on a commercial-grade UAV.
This research originated at the U.S. Army Combat Capabilities Development Command’s Army Research Laboratory about 10 years ago, with current CCDC ARL researcher and fellow Dr. Gorden Videen and the then postdoctoral student Dr. Matthew Berg, now a professor at Kansas State University.
“This was a novel idea at the time,” Videen said. “Gaining information about aerosols is hard because they don’t sit still, so they are difficult to image because the focal plane of cameras is so narrow. Holography circumvents this problem because the focusing can be done by processing in a computer after the hologram is formed.”
Videen and Berg continued collaborating on this project when Berg was hired at Mississippi State University and later at KSU. Other collaborators include Dr. Osku Kemppinen from the University of Maryland, College Park, Dr. Jesse Laning from the University of Central Florida and Dr. Ryan Mersmann from KSU.
There are some innovative and convenient features of this system, Videen said. It is light and primarily constructed using a 3D printer with some tweaks at the end, and it can be done so inexpensively as the researchers are using visible light and cost-effective components.
The device has been tested and is currently being used to characterize aerosols, primarily dust and pollen.
The unique and recently updated features of the system, detailed in the paper “Imaging atmospheric aerosol particles from a UAV with digital holography and featured in Nature Scientific Reports are the construction and the use of a UAV device to collect actual data in situ.
With additional onboard processing, images can be captured in real-time and sent to a computer or even a phone using Wi-Fi or Bluetooth.
“HAPI provides a completely different means of characterizing aerosol particles in situ,” Videen said. “Previous methods have relied on either capturing aerosols onto a substrate, taking them in to the lab and analyzing them, which is a time-consuming process, or of measuring their diffraction patterns, which only gives size information or measuring their fluorescence or Raman signal, which provides chemical information.”
This method, he said, provides timely information and aerosol shapes that can further characterize aerosols and is complementary to other techniques. It can be used in conjunction with other techniques, can be done rapidly in situ, and doesn’t destroy the aerosol so that it can be further analyzed.
“This research is unique because it uses holography to characterize aerosol particles by capturing images of their physical shape,” Videen said. “This has not been done before and other researchers have not yet ventured in to this territory. This update is the latest step to miniaturize the instrument, put it onto a drone and fly it around to capture these images in situ. This is a major step and was implemented in a relatively short amount of time.”
According to Videen, characterizing aerosols contributes to situational awareness, which ultimately increases Soldier lethality, an Army Modernization Priority.
“One of our goals is to identify threat aerosols, like biological warfare agents,” Videen said. “In order to do this, we need to develop new techniques that can rapidly detect and characterize aerosols. This technology provides a new type of aerosol information that can be incorporated into detectors. We have demonstrated that this technology can be miniaturized and incorporated into a drone.”
Aerosol holography is one piece of the puzzle that Videen believes will be incorporated into future detector systems to provide Soldier protection and increase survivability.
The next step for this research is to increase the resolution of the holography system so that the researchers can image and characterize smaller particles, which are the real threat aerosols.
CCDC Army Research Laboratory is an element of the U.S. Army Combat Capabilities Development Command. As the Army’s corporate research laboratory, ARL is operationalizing science to achieve transformational overmatch. Through collaboration across the command’s core technical competencies, CCDC leads in the discovery, development and delivery of the technology-based capabilities required to make Soldiers more successful at winning the nation’s wars and come home safely. CCDC is a major subordinate command of the Army Futures Command.