Journal article
Apratim Majumder, Monjurul Meem, R. Stewart, R. Menon
Optics Express, 2021
Optics Express, 2021
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APA
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Majumder, A., Meem, M., Stewart, R., & Menon, R. (2021). Broadband point-spread function engineering via a freeform diffractive microlens array. Optics Express.
Chicago/Turabian
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Majumder, Apratim, Monjurul Meem, R. Stewart, and R. Menon. “Broadband Point-Spread Function Engineering via a Freeform Diffractive Microlens Array.” Optics Express (2021).
MLA
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Majumder, Apratim, et al. “Broadband Point-Spread Function Engineering via a Freeform Diffractive Microlens Array.” Optics Express, 2021.
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@article{apratim2021a,
title = {Broadband point-spread function engineering via a freeform diffractive microlens array.},
year = {2021},
journal = {Optics Express},
author = {Majumder, Apratim and Meem, Monjurul and Stewart, R. and Menon, R.}
}
Abstract
We utilized inverse design to engineer the point-spread function (PSF) of a low-f-number, freeform diffractive microlens in an array, so as to enable extended depth of focus (DOF). Each square microlens of side 69 µm and focal length 40 µm (in a polymer film, n∼1.47) generated a square PSF of side ∼10 µm that was achromatic over the visible band (450 to 750 nm), and also exhibited an extended DOF of ∼ ± 2 µm. The microlens has a geometric f/# (focal length divided by aperture size) of 0.58 in the polymer material (0.39 in air). Since each microlens is a square, the microlens array (MLA) can achieve 100% fill factor. By placing this microlens array (MLA) directly on a high-resolution print, we demonstrated integral imaging with applications in physical security. The extended DOF preserves the optical effects even with expected film-thickness variations, thereby increasing robustness in practical applications. Since these multi-level diffractive MLAs are fabricated using UV-nanoimprint lithography, they have the potential for low-cost large volume manufacturing.