Ms. Anja Schöneberg Profile

Anja Schöneberg

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Proceedings Article | 17 June 2024 Presentation + Paper

Performance of UV-molded versus injection molded maskless microlens arrays for multi-aperture projection

R. Kundu, D. Michaelis, D. Stefanidi, P. Schreiber, A. Schöneberg, R. Leitel, F. Prass, B. Schaller

Proceedings Volume 13021, 130210J (2024) https://doi.org/10.1117/12.3016164

KEYWORDS: Stray light, Lens arrays, Projection systems, Modeling, Injection molding, Monte Carlo methods, Microlens array, Light emitting diodes, Grayscale lithography, Illumination engineering, Freeform optics, Diffusers

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Maskless microlens arrays (MLA) for multi-aperture projection offer high transmission due to absence of buried absorbing mask structures for shaping the pattern. Arbitrary shaped lenslets arranged in a high fill-factor array form the entrance MLA, the apertures of each entrance lenslet are projected towards the far-field by regularly shaped lenslets of the exit array. Resulting tandem MLA is arranged in a fly’s eye homogenizer (FEH) configuration. Such MLAs are mastered by grayscale photolithography and replicated as UV-molded polymer-on-glass (POG) elements. Furthermore, such maskless projectors can be realized using alternative replication technologies, primarily - injection molding (IM), which offers low cost for large area replication. MLA designed for POG replication can be adapted for IM replication by adjustment of certain parameters, e.g., thickness due to material substitution. Since the shape of the lenslets remain same for both processes, the same MLA masters can be used to generate the tooling molds necessary for IM replication. However, unlike POG replication, IM technology lacks active alignment of the entrance and exit arrays which makes IM replicated MLAs more vulnerable to crosstalk and stray light. Hence, a trade-off between ease of manufacturing (low costs) and projected image quality (sharpness, contrast, stray light) should be considered when dealing with IM replication. In this work we describe an exemplary IM replicated maskless MLA, based on masters of a previously realized POG replicated MLA for an automotive projected blinker. We discuss the design adaptation to IM and present profilometric and photometric characterization of the IM replicated MLA. We also compare the characterization results of the IM MLA samples with that of ‘gold-standard’ POG replicated MLA and discuss performance, quality of projection and limitations of IM technology.

Proceedings Article | 2 October 2023 Presentation + Paper

Multi-aperture pattern projection using arbitrary shaped microlenslets

R. Kundu, D. Michaelis, P. Schreiber, P. Schleicher, A. Schöneberg, R. Leitel, A. Tünnermann, U. Breyer

Proceedings Volume 12666, 1266608 (2023) https://doi.org/10.1117/12.2675559

KEYWORDS: Stray light, Lens arrays, Projection systems, Light emitting diodes, Light sources and illumination, Design and modelling, Collimation, Crosstalk, Micro optics

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Micro-optical projectors consist of a double-sided, aligned microlens array (MLA) with an absorptive slide mask array buried under the entrance condenser lenslets. While the exit lenslets project the slides, the condenser lenslets realize Kohler illumination of the multiple projector channels. To achieve high system transmission, the condenser lenslets have to be positioned in a space-filling arrangement. For arbitrary projected shapes, the slide further reduces the effective fill-factor of a channel. We propose to increase fill-factor and simplify architecture of the MLA by replacing the buried slides by condenser lenslets with certain elementary shapes, building an irregular entrance array with space-filling parqueting. The condenser lenslets´ apertures are imaged by the projector lenslets towards certain positions in the far-field, controlled by the decentration between condenser contour and projector vertex. This enables for optional ‘jigsawing’ of the intended pattern from elementary images. Any residual MLA regions, that cannot be covered by condenser lenslet apertures, can be excluded from projection by patterning with diffusor structures, which scatter away incident light under large angles. Now, that we have excluded the buried mask array, such double-sided MLA can be replicated not only as precise polymer-on-glass elements (POG), but also by cheaper high-volume techniques like injection molding (IM), making the latter attractive for the automotive industry. An automotive projecting chase light blinker based on this concept, employing controlled channel crosstalk, replicated as POG is presented. IM replication of MLA is currently underway. We evaluate the performance and present a brief outlook of mask-less, multi-aperture microoptics.

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