In this paper, we present our investigation into the prevention of blue-light leakage in phosphor-converted white LEDs through a passive approach. Our study primarily focuses on the application and optimization of a specific thermochromic material known as Crystal Nano Cellulose (CNC). We integrated CNC within the epoxy lens of white LEDs. Importantly, under normal operating conditions, CNC minimally affects the optical properties of the emitted white light. However, in instances of overheating where blue-light leakage occurs, the temperature rise induces a darkening effect in CNC. By incorporating CNC as a responsive material in the design of white LEDs, our study offers a practical and efficient solution to address the adverse effects of blue-light leakage resulting from overheating. This enhancement not only improves the safety and comfort for users but also serves as an early warning mechanism for the aging of phosphor-converted white LEDs.
The CGH technique is crucial for MR displays, resolving the VAC issue with three-dimensional image generation. However, drawbacks include excessive device volume and speckle noise from coherent light. The lightguides with VHOE couplers and LED light source are employed to address these issues. In this study, we employed an LED as the light source to reduce the speckle noise. The volume holographic optical elements (VHOEs) as the in-coupler and out-coupler are designed as bandpass filters. The VHOEs filtered the CGH display's effective wavelength to inhibit image degradation caused by dispersion. Furthermore, the aberration caused by the lightguide was analyzed and compensated in this study. The design method, simulation results, and experimental results are discussed in this work.
In this presentation, we will delve into the evolution of volume holographic optical elements (VHOEs), discussing their development alongside calculation models such as the VOHIL model. We will unveil a novel visualization scheme rooted in this model, aimed at elucidating Bragg diffraction within intricate volume holograms. Lastly, we will showcase the latest advancements in the application of VHOEs, particularly in the realm of lightguide-based Augmented Reality (AR) and Mixed Reality (MR) glasses.
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