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Scanning Microwave Ellipsometer And Performing Scanning Microwave Ellipsometry

Patent Number: 11,287,366 B2


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.

patent description

This invention is scanning microwave ellipsometry. It contains a test head that rotates the electric microwave field relative to the sample without rotating the sample; a test head mounted onto a 6-axis robotic arm; and an algorithm that fits the microwave ellipsometry data. This a new tool and method to characterize carbon fiber alignment and measure materials for inline quality assurance or for verification of alignment in 3D parts. This implementation uses a polarized electric microwave field and measures the reflection of that field off a sample under test as a function of angle. The resulting reflected power plotted versus measured angle on a polar plot can have an elliptical shape. Leveraging this idea, we designed a test head that rotates the electric microwave field relative to the sample without rotating the sample. To raster the test head over a sample, we placed the test-head on a 6-axis robotic arm. To use this implementation, we wrote an algorithm that fit the microwave ellipsometry data. The algorithm produces four discrete measurands that can be plotted as a function of position in three-, two-, or one-dimensions. The measurands are the maximum value, the minimum value, the alignment value, and the orientation value.


Current practice is to image the material on a light table. Light table imaging does not provide quantitative data for analysis, only relative information. Image processing techniques average over the image or segment the image. Light table imaging fails when the host matrix is not optically transparent or if the material is too dense.

Created August 23, 2022, Updated December 15, 2023