NASA Langley Research Center’s Electric Field Imaging (EFI) system is the only noncontact method capable of quantitatively measuring the magnitude and direction of electrostatic fields in near- and far-field applications. Based on low-cost, commercially available components, the EFI system uses measurement of very-low-current, human-safe electric fields to construct a three-dimensional image of objects and people based on their dielectric properties. This platform technology, originally developed for measurement of the efficacy of electrical shielding around cables, could be optimized for a variety of applications, including medical imaging, security and detection, weather and natural disaster prediction, and nondestructive evaluation of composites and insulators. The EFI system has the potential to offer a lower-cost, portable, and safer alternative to the imaging systems currently used in these applications.
The EFI imaging platform consists of a sensor array, processing equipment, and an output device. By registering voltage differences at multiple points within the sensor array, the EFI system can calculate the electrical potential at points removed from the sensor. Using techniques similar to computed tomography, the electrical potential data can be assembled into a three-dimensional map of the magnitude and direction of electric fields. Objects interact with electric fields differently based on their shape and dielectric properties, so this electric field data can then be used to understand shape, internal structure, and dielectric properties (e.g., impedance, resistance) of objects in three dimensions.
The EFI sensor can be used on its own to see electric fields or image electric field-emitting objects near the sensor (e.g., to evaluate leakage from poorly shielded wires or casings). For evaluation of objects that do not produce an electric field, NASA has developed a generator that emits a low-current, human-safe electrostatic field for snapshot evaluation of objects. Additionally, an alternative EFI system optimized to evaluate electric fields at significant distances (greater than 1 mile) is being developed for weather-related applications.
This technology can be optimized for localized or remote applications, and has the potential for near-real-time imaging with GHz data sampling rates. In addition, it does not require exposure to radiation, magnetic fields, heat, or light; can distinguish between nonconductive materials with high precision (potential capability to detect 0.01% change in dielectric properties between measurements); and has point-and-scan workflow design.
The EFI system can be used in medical applications for remote respiratory and vascular system monitoring, brain imaging, cancer detection, and cardiac polarization wave imaging; nondestructive evaluation applications for flaw detection in composites, evaluation of electrical properties of insulators, and electrical shielding evaluation; security applications for baggage and personnel screening, personnel detection, and intrusion detection; crime scene applications for forensic evaluation of the history of events (what was touched with or without gloves, and where people walked); and meteorology applications for lightning strike detection or lightning protection designs.