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Diffractive optics are structured optical surfaces that manipulate light based on the principles of interference and diffraction. By carefully designing the diffractive optical elements, the amplitude, phase, direction, and polarization of the transmitted and reflected light can be controlled. It is well-known that the propagation of light through diffractive optics is sensitive to changes in their structural parameters. In this study, a numerical analysis is conducted to evaluate the capabilities of slanted-wire diffraction gratings to function opto-mechanically in the infrared spectral range. The slanted wire array is designed such that it is compatible with fabrication by two-photon polymerization, a direct laser-writing approach. The modeled optical and mechanical capabilities of the diffraction grating are presented. The numerical results demonstrate a high sensitivity of the diffracted light to changes in the slant angle of the wires. The compressive force by which desired slant angles may be achieved as a function of the number of wires in the grating is investigated. The ability to fabricate the presented design using two-photon polymerization is supported by the development of a prototype. The results of this study suggest that slanted-wire gratings fabricated using two-photon polymerization may be effective in applications such as tunable beam splitting and micro-mechanical sensing.
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Computational Watermark Enhancement in Leonardo’s Codex Leicester
A better understanding of the inner structural features (watermarks and chain line/wire intervals) of the manuscript papers of Leonardo da Vinci (1452-1519) can provide valuable information regarding chronology, geographic origins, and studio practice. For valid conclusions, however, clear representations of watermarks and chain line/wires are required. While the easient way to capture these unique physical characteristics of paper is via transmitted light, they can be difficult to decipher when writing and other surface marks found on the recto (front/obverse) and the verso (back/reverse) of the sheet obscure them. Using Leonardo's Codex Leicester (Bill Gates Collection), complied circa 1508-1510, as a case study, a computational approach was designed to minimize surface writing to enhance the watermarks and chain lines/wires detectable in the paper, by subtracting out diffuse specular (normal) light images of the recto and verso sides from the transmitted light image. This is accomplished by posing the problem as a mathematical optimization problem, and solving for the optimal weights is fast and robust.
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- Award ID(s):
- 1822007
- PAR ID:
- 10137970
- Date Published:
- Journal Name:
- Journal of the American Institute for Conservation
- ISSN:
- 0197-1360
- Page Range / eLocation ID:
- 1 to 10
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1080/01971360.2019.1703483
