Dr. Lena Nault Profile

Dr. Lena Nault

at Covestro AG

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Publications (2)

Proceedings Article | 13 March 2024 Presentation + Paper

A standardized NIR sensitized Bayfol HX film

Friedrich-Karl Bruder, Johannes Frank, Sven Hansen, Mira Holzheimer, Alexander Lorenz, Christel Manecke, Jack Mills, Lena Nault, Igor Pochorovski, Thomas Rölle

Proceedings Volume 12910, 129100B (2024) https://doi.org/10.1117/12.3001715

KEYWORDS: Near infrared, Dyes, Holography, Holograms, Glasses, Eye tracking, RGB color model, Polymerization, Film thickness, Heads up displays

Read Abstract +

Bayfol® HX photopolymer films prove themselves as easy-to-process recording materials for volume holographic optical elements (vHOEs) and are available in customized grade at industrial scale. Their full-color (RGB) recording and replay capabilities are two of their major advantages. Moreover, the adjustable diffraction efficiency, tunable angular and spectral selectivity of vHOEs recorded into Bayfol® HX as well as their unmatched optical clarity enables superior invisible “off Bragg” optical functionality. As a film product, the replication of vHOEs in Bayfol® HX can be carried out in a highly cost-efficient and purely photonic roll-to-roll (R2R) process. Utilizing thermoplastic substrates, Bayfol® HX was demonstrated to be compatible to state-of-the-art plastic processing techniques like thermoforming, film insert molding and casting, which opened up using a variety of industry-proven integration technologies for vHOEs. Therefore, Bayfol® HX makes its way in applications in the field of augmented reality such as Head-up-Displays (HUD) and Head-mounted-Displays (HMD), in free-space combiners, in plastic optical waveguides, and in transparent screens. Also, vHOEs made from Bayfol® HX are utilized in highly sophisticated spectrometers in astronomy as well as in narrow band notch filters for eyeglasses against laser strikes and retail optics. See through applications such as, HMD and HUD, have demanding performance requirements on combiner and imaging technologies such as efficiency, optical function, and clarity. The properties of Bayfol® HX make it principally well suited to solve these challenges in primary display, and near-infrared imaging applications such as eye-tracking. Based on a customizable and available toolbox, Bayfol® HX can be adopted for a variety of such applications. To serve further sensing applications we recently extended our chemical toolbox to address the photo sensitization beyond RGB into the Near Infrared Region (NIR), and reported already on various demonstration examples. On our way to generate a standardized Bayfol® HX film sensitized in the NIR - comparable to Bayfol® HX200 sensitized for RGB - we investigated the initiation mechanism in greater detail for this tailored NIR photoinitiation system and report on the performance characteristics of the envisaged standardized NIR sensitized Bayfol® HX film fabricated on the production coating line.

Proceedings Article | 12 March 2024 Presentation + Paper

Fabricating a complete set of Bayfol HX vHOE’s with applications in see through displays using free space recording techniques

Friedrich-Karl Bruder, Johannes Frank, Sven Hansen, Mira Holzheimer, Alexander Lorenz, Christel Manecke, Jack Mills, Lena Nault, Igor Pochorovski, Thomas Rölle, Brita Wewer

Proceedings Volume 12913, 129130U (2024) https://doi.org/10.1117/12.3001728

KEYWORDS: Free space, Waveguides, Glasses, Bragg wavelengths, Diffraction, Film thickness, Beam combiners, Near infrared, Holography

Read Abstract +

Bayfol® HX photopolymer films prove themselves as easy-to-process recording materials for volume holographic gratings (VHGs) and are available in customized grade at industrial scale. Their full-color (RGB) recording and replay capabilities are two of their major advantages. Moreover, the adjustable diffraction efficiency, tunable angular and spectral selectivity of VHGs recorded into Bayfol^® HX as well as their unmatched optical clarity enables superior invisible “Off-Bragg” optical functionality. As a film product, the replication of VHGs in Bayfol^® HX can be carried out in a highly cost-efficient and purely photonic roll-to-roll (R2R) process. Utilizing thermoplastic substrates, Bayfol^® HX was demonstrated to be compatible to state-of-the-art plastic processing techniques like thermoforming, film insert molding and casting, which opened up using a variety of industry-proven integration technologies for VHGs. Therefore, Bayfol^® HX makes its way in applications in the field of augmented reality such as Head-up-Displays (HUD) and Head-mounted-Displays (HMD), in free-space combiners, in plastic optical waveguides, and in transparent screens. Also, VHGs made from Bayfol^® HX are utilized in highly sophisticated spectrometers in astronomy as well as in narrow band notch filters for eyeglasses against laser strikes and retail optics. See through applications such as, HMD and HUD, have demanding performance requirements on combiner and imaging technologies such as efficiency, optical function, and clarity. The properties of Bayfol^® HX make it well suited to solve these challenges in primary display, and near-infrared imaging applications such as eye-tracking, while maintaining the requirements on optical performance. Using our novel free space Bragg matching technique introduced two years ago we demonstrate the recording of a complete set of grating couplers to achieve a 2-D eye-box expansion in a representative waveguide based near-eye display. In addition, using our novel NIR sensitized Bayfol^® HX grade, we demonstrate a free space holographic grating combiner working at 940 nm but exposed at 850 nm.

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