Simulating Ptychographic Scans

PROJECT NUMBER: 90

AUTHOR: Meghan Kinnischtzke, Physics | MENTOR: Daniel Adams, Physics

ABSTRACT

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Ptychography is a method of microscopic imaging that involves processing multiple diffraction patterns of light that has passed through a specimen. Ptychography involves the use of sophisticated algorithms that separate and decode these patterns, then reconstruct the phase and amplitude of the specimen based on the information contained in its diffraction data. Ptychography has capabilities far beyond those of objective-based microscopy because it inherently produces images with simultaneous phase and amplitude contrast. An existing computer simulation was used to mimic the behavior of a ptychographic scan when imaging an arbitrary sample. Using the same virtual specimen for all tests, multiple different scenarios were simulated and the error margins and general behavior of the simulation were catalogued. The simulation was initialized with two probes of slightly different wavelengths and made to run for 4000 iterations. In each trial, the relative power assigned to each probe (50%/50%, 25%/75%, etc.) was varied. It was found that the simulation behaved most ideally when the first probe was given the larger relative strength (75%/25% as opposed to 25%/75%). The simulation’s error increased as the difference between the two relative probe powers increased. When the probes were fed the same relative power (50%/50%), the simulation’s average error was 4.01E-06. When the discrepancy in relative powers was increased to 99.99%/0.01%, the simulation’s average error increased to 1.14E-05. When these powers were reversed (0.01%/99.99%), the average error increased again to 1.74E-05. The simulation’s error plot can be categorized into three general shapes, which occur arbitrarily, but the probability of each general shape’s occurrence can be loosely predicted based on the relative powers entered for each probe.

VISUAL PRESENTATION

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AUTHOR BIOGRAPHY

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Meghan Kinnischtzke is a junior student in the Engineering Physics department at the Colorado School of Mines. She is currently involved in research with the Applied Optics group and works under Dr. Daniel Adams on a ptychography project. Meghan plans to complete her senior design project in the optics group and hopes to pursue a PhD in either Optical Physics or Physics Education Research upon graduation from Mines.

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