5 March 2013 Inkjet printed microlens array on patterned substrate
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Micro lens arrays (MLA) can be utilized in various applications of light sensitive devices such as digital cameras or objective free microscopes, and 3D imaging because of their good light collection efficiencies. Many of the fabrication methods used today require heat or expensive equipment or molds and that is why there is a need for a simple and cost effective fabrication method for MLAs. An inkjet printing based production method for low-cost micro lenses is presented here. By pre-patterning the used substrate the printing accuracy and the shape of the lenses is improved. The surface patterning is done with photolithography to fabricate round, shallow reservoirs for the lenses to be printed in. The liquid lens material is then inkjet printed into them. The pattern edges prevent the spreading of the ink outside the wanted area increasing the tolerance for printing inaccuracy and resulting to the uniform array of micro lenses. By depositing the ink to the reservoir, the ink forms a convex surface a.k.a. a lens. The used lens material is negative photoresist, so after printing it is cured with UV-light and baked in a hot plate to solidify the lens matrix. By placing different amount of ink in a reservoir the height of the lenses changes and thus the focus of the lens can be adjusted making the proposed method versatile tool for MLA fabrication.
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P. Vilmi, P. Vilmi, R. Myllylä, R. Myllylä, T. Fabritius, T. Fabritius, "Inkjet printed microlens array on patterned substrate", Proc. SPIE 8613, Advanced Fabrication Technologies for Micro/Nano Optics and Photonics VI, 861317 (5 March 2013); doi: 10.1117/12.2001045; https://doi.org/10.1117/12.2001045

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