Apparatus for electromagnetic characterisation of internal features of an object and a process for producing the apparatus
Inventors
REZAEIEH, Sasan Ahdi • DARVAZEHBAN, Amin • KHOSRAVI-FARSANI, Mojtaba • ABBOSH, Amin M.
Assignees
Publication Number
US-12164117-B2
Publication Date
2024-12-10
Expiration Date
2041-07-23
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Abstract
An apparatus for electromagnetic characterisation of internal features of an object, including a lens for placement between a source of electromagnetic energy and the object, the lens being composed of a first material having a first permittivity with openings therein containing or configured to receive one or more second materials having respective second permittivities different to the first permittivity, the openings being configured such that, when the openings contain the one or more second materials, the lens has a graded refractive index wherein an electromagnetic wave generated by the source and incident upon a first surface of the lens as a spherical wave exits a second surface of the lens in contact with a receiving surface of the object substantially as a plane wave, and a refractive index of the lens at the second surface of the lens substantially matches a refractive index of the object at the receiving surface to increase penetration of the plane wave into the object.
Core Innovation
The invention relates to an apparatus and a process for electromagnetic characterisation of internal features of an object. The apparatus includes a lens positioned between a source of electromagnetic energy and the object. This lens is composed of a first material with a first permittivity and contains openings. These openings hold one or more second materials with second permittivities different from the first. The configuration of the openings and the materials within them forms a graded refractive index lens. This lens transforms an electromagnetic wave from a spherical wave incident on a first surface into a plane wave exiting the second surface in contact with the object. The refractive index at the second surface matches that of the object to improve penetration of the plane wave into the object.
The problem addressed by the invention is the limitations of existing non-destructive testing (NDT) methods, such as ultrasonic testing (UT) and electromagnetic medical imaging. These methods suffer from issues including the need for matching media, limited penetration due to impedance mismatches, the requirement to switch probe heads, and difficulty in handling objects with curved surfaces. Existing antennas often have compact apertures or require high power signals that are impractical or unsafe in certain applications. The invention seeks to provide a structure that bridges the gap between the antenna and the object without complicating the test setup or limiting detection capabilities, thereby overcoming and alleviating these difficulties.
The invention proposes the use of graded index (GRIN) lenses formed by a first material with openings filled with second materials of differing permittivity, enabling a gradual transition of permittivity from air to the object. This design collimates spherical waves into plane waves that match the object's refractive index, increasing electromagnetic wave penetration and reducing reflections without the need for matching media. The lens can be formed using 3D printing with adjustable openings arranged in layers, which can be filled dynamically or statically with fluids or other materials to control wave direction, intensity, and conform to non-planar object surfaces.
Claims Coverage
The patent contains two main independent claims covering the apparatus and the process for producing it, respectively, with multiple inventive features centered on the graded refractive index lens and its properties.
Apparatus with graded refractive index lens for electromagnetic characterisation
An apparatus including a lens for placement between a source of electromagnetic energy and the object, constructed from a first material with openings containing or configured to receive one or more second materials having different permittivities. The lens forms a graded refractive index such that a spherical electromagnetic wave incident on one surface exits the other surface in contact with the object as a plane wave, with the refractive index at the exit surface matching that of the object to increase wave penetration.
Process for producing the apparatus with graded refractive index lens
A process involving forming a body of a first material with openings configured such that when containing predetermined second materials of differing permittivities, a graded refractive index lens is formed. This lens converts a spherical electromagnetic wave incident on one surface into a plane wave exiting the other surface, matching the refractive index of the object’s receiving surface to eliminate the need for a matching medium.
The independent claims focus on the novel composition and configuration of the lens to produce a graded refractive index that transforms spherical waves into plane waves and matches the refractive index at the interface to the object. The apparatus claim covers the physical lens assembly and its electromagnetic functionality, while the process claim covers the method of forming such a lens including potential dynamic control of materials within the openings.
Stated Advantages
Increased penetration depth of electromagnetic waves into objects without the need for any refractive index matching medium.
Improved signal-to-noise ratio due to increased intensity and collimation of the electric field inside the target medium.
Reduced or eliminated reflection at the air/object interface through gradual permittivity transition.
Customizable and optimized designs for various applications by adjusting the permittivity gradient via openings size, arrangement, and fillings.
Ability to conform the lens to non-planar object surfaces, improving practical usage and measurement accuracy.
Capability to steer the electromagnetic beam direction statically or dynamically by selectively filling openings with different materials.
Cost-effective and flexible fabrication using 3D printing technology, facilitating maintenance and replacement.
Documented Applications
Non-destructive testing of industrial materials such as concrete slabs to detect internal defects (e.g., cracks).
Steering and focusing electromagnetic waves to analyze different directions and regions within an object like sandy soil.
Biomedical electromagnetic imaging and diagnostic applications, including imaging of human body parts like the torso and potentially for medical diagnostics requiring safe low power and high penetration.
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