Integration of volume holographic optical elements (vHOE) made with Bayfol® HX into plastic optical parts

Abstract

See-through optical components are being intensively studied in applications such as Head-Up-Displays (HUD) and Head-Mounted-Displays (HMD). In particular, volume holographic optical elements (vHOE) have received a lot of attention due to their unique optical (angular and spectral selectivity) and mechanical (lightweight and thin) characteristics which make them perfectly suitable for use in integrated optical components like spectacle lenses and car windshields. Bayfol® HX photopolymer films prove themselves as easy to process recording materials for vHOEs. The Bayfol® HX instant developing holographic photopolymer film provides full color capability and adjustable diffraction efficiency as well as an unprecedented optical clarity when compared to classical volume holographic recording materials like silver halide emulsions (AgX) or dichromated gelatin (DCG). Besides the recording step, no pre- or postprocessing is necessary and easy mass production of vHOEs in a completely dry roll to roll process is possible. The layout of a typical Bayfol® HX film consists of a light-sensitive photopolymer layer coated onto a transparent thermoplastic substrate. This substrate is particularly beneficial, not only for easy handling of the film during holographic recording, but also for further mechanical processing steps which are required to embed the film into a finished optical component. Once holograms have been recorded and the film has been bleached with incoherent light, the Bayfol® HX film becomes inert and can be further processed in normal daylight. Moreover, the presence of a thermoplastic substrate makes the film attractive for use in manufacturing processes such as injection molding, thermoforming, casting, etc…, typically used to fabricate parts for the automotive, eyewear and ID-card industry. Being compatible with these industrial processes is an essential feature for the widespread of immersive Augmented Reality displays based on volume holographic optical elements recorded into Bayfol® HX films. In this paper we investigated the compatibility of holograms made with Bayfol® HX film with some of the integration processes typically used in the plastic and optical components industry and which are necessary for embedding the holographic films into a finished product.