Using Superimposed Waves to Extract Information
Interferometry is a technique in which waves are superimposed to cause the phenomenon of interference, which is used to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy (and its applications to chemistry), quantum mechanics, nuclear and particle physics, plasma physics, remote sensing, biomolecular interactions, surface profiling, microfluidics, mechanical stress/strain measurement, velocimetry, optometry, and making holograms.
Optics. a device that separates a beam of light into two ray beams, usually by means of reflection, and that brings the rays together to produce interference, used to measure wavelength, index of refraction, and astronomical distances.
Talbot Grating Interferometry as a new phase-contrast imaging method simultaneously provides four different contrast modes, that is, absorption, differential phase, phase, and dark-field contrast. Meanwhile, it relaxes beam requirements on monochromaticity and coherence, as a white beam with spatial coherence of a few micrometers can be used.
Interferometers are devices that extract information from interference. They are widely used in science and industry for the measurement of microscopic displacements, refractive index changes, and surface irregularities. In the case with most interferometers, light from a single source is split into two beams that travel in different optical paths, which are then combined again to produce interference; two incoherent sources can also be made to interfere under some circumstances though. The resulting interference fringes give information about the difference in optical path lengths. In analytical science, interferometers are used to measure lengths and the shape of optical components with nanometer precision; they are the highest precision length measuring instruments in existence. In Fourier transform spectroscopy they are used to analyze light containing features of absorption or emission associated with a substance or mixture. An astronomical interferometer consists of two or more separate telescopes that combine their signals, offering a resolution equivalent to that of a telescope of diameter equal to the largest separation between its individual elements.
Gratings, whether fabricated for X-ray or neutron interferometry and their unique characteristics (compositions, periods, aspect ratio) are the backbone of Refined Imaging’s research and development technology. Since the discovery of X-rays in 1895 by Wilhelm Röntgen, all industrial and medical imaging has used only the absorption imaging modality. In comparison, visible light microscopy has developed absorption, phase contrast, and dark-field imaging modalities. In 2006, researchers in Switzerland and Japan employed microfabricated gratings of gold on silicon wafers to create an X-ray interferometry imaging system. Now, the advantages of phase-contrast and dark-field imaging can be applied to industrial and medical applications. The benefits to society are improved images in soft tissue such as diseased lungs and complex structures such as additive manufacturing (hip cups and cranial implants).
Gratings can be fabricated by multiple mechanisms; lithography/LIGA (LIGA, a German acronym for “Lithographie, Galvanoformen, Abformung” meaning “lithography electroplating, molding”), 3D printed, micro-milled, laser milled, Deep Reactive Ion Etching (DRIE), MacEtch, are some of the fabrication techniques. Gratings are also fabricated using various materials, at differing periods (spacing), to create both absorption and phase gratings. Refined Imaging is using several conventional methods as well as some proprietary techniques to fabricate gratings. Refined Imaging will continue to explore different manufacturing techniques and mathematically align the gratings to achieve the maximum image resolution.
Since the invention of grating-based X-ray interferometry in 2006, three algorithms have been used to process the images. The vectorized least squares method of processing interferometry images has become the industry standard. This process was invented and patented by the RI team (2018 patent).
Reﬁned Imaging is developing intellectual property, patents, and trade secrets. Refined Imaging has the exclusive license agreement with LSU for the following patents and technology disclosures.
US patent 10,117,629 “Process for More Effective Performance of X-Ray Grating Interferometry at High Energy” with co-inventors Les Butler, Kyungmin Ham, and Warren Johnson, November 6, 2018. RI has an exclusive license agreement for the use of this patent from LSU.
US patent 10,872,708 “Phase Contrast X-ray Interferometry”, with co-inventors J. Dey, N. Bhusal, L. Butler, K. Ham, J. Dowling, V. Singh, December 22, 2020.
LSU technology disclosure Interferometry, additive manufacturing, and blockchain to eliminate counterfeit AM components in manufacturing/maintenance workﬂow. Patent development work funded by Louisiana Board of Regents grant to Drs. Butler (PI) and Maasberg (consultant), 6/20-5/22.
LSU technology disclosure Mitigation of interferometer vibrations with a concept derived from the gravity wave instrument at LIGO. Reﬁned Imaging is working with LSU to include this potential patent into the current exclusive license agreement.
Provisional Patent – “Counterfeit Detection and Provenance with Grating Interferometry, Blockchain, and Smart Contracts”, with co-inventors Leslie G. Butler, Michele L. Maasberg, Ian Taylor, Charles C. Hartman, November 2021
To detect small deflections, optics are inserted between radiation source and detector, as shown in this animation.
One optics strategy is the use of slit optics, where the slit dimension combined with the distance between source and detector enables detection of very small angular deflections of the X-ray or neutron.