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Micromachines 2018, 9(7), 355;

Injection Compression Molded Microlens Arrays for Hyperspectral Imaging

Hahn-Schickard, Allmandring 9B, 70569 Stuttgart, Germany
Institute for Micro Integration (IFM), University of Stuttgart, Allmandring 9B, 70569 Stuttgart, Germany
Balluff GmbH, Schurwaldstraße 9, 73765 Neuhausen auf den Fildern, Germany
Author to whom correspondence should be addressed.
Received: 25 June 2018 / Revised: 12 July 2018 / Accepted: 17 July 2018 / Published: 18 July 2018
(This article belongs to the Section A:Physics)
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In this work, a polymer microlens array (MLA) for a hyperspectral imaging (HSI) system is produced by means of ultraprecision milling (UP-milling) and injection compression molding. Due to the large number of over 12,000 microlenses on less than 2 cm², the fabrication process is challenging and requires full process control. The study evaluates the process chain and optimizes the single process steps to achieve high quality polymer MLAs. Furthermore, design elements like mounting features are included to facilitate the integration into the final HSI system. The mold insert was produced using ultraprecision milling with a diamond cutting tool. The machining time was optimized to avoid temperature drifts and enable high accuracy. Therefore, single immersions of the diamond tool at a defined angle was used to fabricate each microlens. The MLAs were replicated using injection compression molding. For this process, an injection compression molding tool with moveable frame plate was designed and fabricated. The structured mold insert was used to generate the compression movement, resulting in a homogeneous pressure distribution. The characterization of the MLAs showed high form accuracy of the microlenses and the mounting features. The functionality of the molded optical part could be demonstrated in an HIS system by focusing light spectrums onto a CCD image sensor. View Full-Text
Keywords: microlens array; ultraprecision milling; injection compression molding; microstructures; polymer optics; hyperspectral imaging microlens array; ultraprecision milling; injection compression molding; microstructures; polymer optics; hyperspectral imaging

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Roeder, M.; Drexler, M.; Rothermel, T.; Meissner, T.; Guenther, T.; Zimmermann, A. Injection Compression Molded Microlens Arrays for Hyperspectral Imaging. Micromachines 2018, 9, 355.

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