Scanning microwave ellipsometer and performing scanning microwave ellipsometry
Inventors
LONG, CHRISTIAN JOHN • Orloff, Nathan Daniel • Basta, Nina Popovic • Garboczi, Edward Joseph
Assignees
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Publication Number
US-11287366-B2
Publication Date
2022-03-29
Expiration Date
2040-05-01
Abstract
A scanning microwave ellipsometer includes: a microwave ellipsometry test head including: a polarization controller; a transmission line; and a sensor that produces sensor microwave radiation, subjects a sample to the sensor microwave radiation, receives a sample reflected microwave radiation from the sample that results from subjecting the sample with the sample reflected microwave radiation, and produces a sensor-received microwave radiation from the sample reflected microwave radiation, wherein a polarization of the sensor microwave radiation is controlled by the polarization controller; an electrical signal measurement system that produces an electrical readout signal such that a magnitude of reflection coefficient Γ and an angle of reflection coefficient Γ of the sample reflected microwave radiation is determined from the electrical readout signal; and a position controller that adjusts a relative position of the sensor and the sample.
Core Innovation
The invention is a scanning microwave ellipsometer that includes a microwave ellipsometry test head with a polarization controller, transmission line, and sensor. The polarization controller modulates the polarization of microwave radiation, which is then transmitted via the transmission line and sensor to a sample. The sample reflects microwave radiation, which is received back by the sensor and processed to produce an electrical signal. This signal's magnitude and angle of the reflection coefficient are determined to characterize the sample's properties.
The scanning microwave ellipsometer also includes an electrical signal measurement system that generates the input electrical signal, receives and processes the output signal to determine reflection characteristics, and produces control signals for a position controller. The position controller adjusts the relative position between the sensor and the sample, allowing the sensor to scan the sample surface, enabling spatially resolved measurements.
The problem solved by this invention is the failure of conventional tools to accurately characterize the alignment of short carbon fibers in composites for inline quality assurance or verification in three-dimensional parts. Conventional techniques, such as eddy-current inspection and optical imaging, have limitations in terms of frequency range, working distance, applicability to non-transparent or dense materials, and three-dimensional sample characterization. The scanning microwave ellipsometer addresses these issues by enabling non-contact, spatially resolved, anisotropic electrical conductivity measurements at microwave frequencies with flexible positioning, including three-dimensional scanning.
Claims Coverage
The patent contains three independent claims covering the scanning microwave ellipsometer apparatus, the microwave ellipsometer calibrant, and the process for performing scanning microwave ellipsometry.
Scanning microwave ellipsometer apparatus
A scanning microwave ellipsometer comprising a microwave ellipsometry test head including a polarization controller that receives an input electrical signal, produces polarization-controlled microwave radiation, receives reflected microwave radiation, and produces an output electrical signal; a transmission line that communicates with the polarization controller and processes microwave radiation received and reflected; and a sensor communicating with the transmission line to produce sensor microwave radiation, subject a sample to it, receive sample reflected microwave radiation, and produce sensor-received microwave radiation. A polarization of the sensor microwave radiation is controlled by the polarization controller. An electrical signal measurement system produces and communicates electrical signals to and from the test head, determines reflection coefficient magnitude and angle from the readout signal, and produces a position control signal. A position controller receives the position control signal, adjusts the relative position of the sensor and sample, and moves the sensor relative to the sample so the sensor scans the sample's surface.
Microwave ellipsometer calibrant
A calibrant comprising a substrate and multiple sectors disposed on it, each sector providing known material and known positional anisotropy of microwave reflection coefficient. The sectors include: a first sector with first and second materials disposed as alternating stripes to provide a first anisotropic sheet resistivity; a second sector with third and fourth materials as alternating stripes to provide a second anisotropic sheet resistivity; a third sector with a fifth material providing a first isotropic sheet resistivity; and a fourth sector with a sixth material providing a second isotropic sheet resistivity.
Process for performing scanning microwave ellipsometry
A process comprising receiving an input electrical signal by the polarization controller, producing polarization-controlled microwave radiation, receiving reflected microwave radiation, producing an output electrical signal, and transmitting microwave radiation through the transmission line and sensor to subject a sample to sensor microwave radiation and receive sample reflected microwave radiation. The electrical signal measurement system produces and communicates input and output signals, produces an electrical readout signal and position control signal. The position controller receives the position control signal, adjusts the relative position of sensor and sample, and scans the surface of the sample with sensor microwave radiation to perform scanning microwave ellipsometry.
The claims cover the scanning microwave ellipsometer apparatus with the test head, signal processing, and position control enabling scanning of the sample, a calibrant designed with anisotropic and isotropic sectors for calibration, and a detailed process for performing scanning microwave ellipsometry involving controlled polarization, signal measurement, positioning, and scanning.
Stated Advantages
Enables scanning microwave ellipsometry providing spatially resolved measurements of material properties, including anisotropic electrical conductivity.
Overcomes limitations of conventional tools for characterizing carbon fiber alignment in composites, such as eddy-current inspection and optical imaging.
Allows non-contact measurements with variable stand-off distance, suitable for planar and three-dimensional sample surfaces.
Compatible with real-time process control and quality assurance in composite manufacturing.
Offers access to high-frequency measurement ranges beyond eddy-current technique limits.
Documented Applications
Real-time process control and quality control for composite manufacturing.
Non-destructive imaging and sub-surface defect detection in composite materials.
Quantitative characterization of anisotropic electrical sheet resistance.
Evaluation of alignment and orientation of short conductive fibers in composite materials.
Large-scale imaging of material properties with spatial resolution in one, two, or three dimensions.
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