When
July 29, 2026, 2 – 5 p.m.
Where
Meinel 821
Title:
Ray Trace Based Modeling of X-ray DPC Imaging System
Abstract:
Optical imaging is traditionally performed by illuminating an object with electromagnetic radiation and measuring the resulting intensity after interaction. This intensity is interpreted as a measure of attenuation, primarily absorption, along each ray path, which can lead to ambiguity when materials of similar attenuation but different refractive properties are imaged. Phase-sensitive imaging, which records variations in optical path length rather than intensity alone, offers a more quantitative alternative. Although phase imaging is well established in the visible spectrum, the 2π periodic nature of the measured phase can produce wrapping artifacts when the optical path difference exceeds one wavelength.
X-ray phase-contrast imaging exploits the much smaller refractive-index decrements at X-ray wavelengths, enabling detection of features invisible in conventional absorption radiography. Originally proposed for medical applications, the technique is equally promising for security screening. Although a full 360° tomographic acquisition remains necessary for three-dimensional reconstruction regardless of the imaging modality, grating-based differential phase-contrast (DPC) methods—particularly the Talbot-Lau interferometer—provide substantially higher sensitivity to weakly absorbing materials than absorption-only techniques.
A principal practical obstacle of conventional three-grating X-ray interferometers is the fabrication and alignment of the high-aspect-ratio gold analyzer grating (G2). This dissertation addresses that limitation by developing a photonic-channeled X-ray detector array (PcXDA) that replaces the third amplitude grating entirely. By integrating a scintillator, microlens arrays, a custom phase plate, and a patterned mask, the PcXDA converts the fine X-ray interference fringe into a detectable optical signal without mechanical phase stepping or extreme-aspect-ratio structures. A hybrid physical-optics / ray-trace simulation framework is developed to model both traditional three-grating systems and the proposed single-grating architecture with high fidelity. The same system is further discussed as a potential approach for precision metrology of surfaces with slopes exceeding 45°, a regime that remains challenging for conventional optical profilometry.
Committee:
Dr. Yuzuru Takashima (Chair)
Dr. Brandon Chalifoux
Dr. Travis Sawyer
Please email Sunglin (slwang@arizona.edu) or graduate student advisor Jini Kandyil (jini@optics.arizona.edu) for the Zoom link.