This innovation is an electric field “illumination” system that is a companion component to the e-Sensor. This generator, when combined with the e-Sensor, enables a new, nondestructive inspection technology called electric field imaging (EFI) by producing spatially uniform, large-magnitude, quasi-static electric fields with human-safe currents (supporting only microampere currents) over large areas or large distances. These fields “illuminate” the objects to be inspected, and enable the EFI method to quantify the distortion of the applied electric field of the invention to detect, locate, and characterize materials present (liquid, solid, insulating, semiconducting, conducting, metallic, non-metallic, polymer, ceramic, composite, etc.), material variations, material damage, material age, and to identify hidden structures.
The generator is comprised of a dipole electrostatic element that generates a variable-magnitude electric dipole field by establishing an electrostatic potential difference that may exceed 200,000 V between two conducting electrodes. The dipole provides the large-magnitude electric fields needed for inspections. Much larger voltage differences are also usable. The dipole element is supported by a non-conducting and triboelectrically neutral rotation shaft. This shaft allows the dipole electric field generated to be undisturbed by its supporting elements, and the rotation provides for operation in the quasi-static regime described previously. Electrically insulating components are used to support the positive and negative electrodes of the dipole element. The electrically insulating electrode supports prohibit current flow directly between the electrodes, and allows for buildup of electrical charges on the electrodes.
The dipole element is contained in a non-conducting and triboelectrically neutral support casing that covers all sides except one. The casing allows the dipole electric fields to be established without additional distortion. One side of the casing is an electrically insulated conducting surface that serves as an electrically floating equipotential surface that establishes a uniform electric field external to the casing and adjacent to the conducting surface that is serving as an approximation of an infinitely large conducting surface.
The invention may be used without a conducting surface to produce a more complex static electric field pattern, and other surfaces with different electromagnetic properties and shapes may be used. A rotational bearing support and a rotational stage drive system are used to provide the controlled rotation of the dipole to operate the quasi-static regime. Although non-conducting and triboelectrically neutral bearing and stage rotational components allow the dipole electric field to develop undistorted, metal bearings and drive stage are used in this implementation depending on the electric field requirements. A wide variety of triboelectric materials may be used to generate the dipole electric field.
This invention has been used to uniformly illuminate a 3-ft (≈0.9-m) 192-element e-Sensor array. In normal operation, various equipotential surfaces are included in the invention to provide a wide variety of illumination configurations to include uniform, radially symmetric, cylindrically symmetric, and an unlimited number of complex, non-symmetric electric field profiles. The demonstration configuration of the invention is large enough to accommodate inspection of aerospace components, containers, baggage, materials, and personnel. A small system, the size of a deck of cards or even smaller, is producible.
This work was done by Edward R. Generazio of Langley Research Center. For further information, contact