Photonics Technologies for Smart Eyewear's Display

The convergence of technology and human perception has significantly advanced our interaction with the environment through wearable devices. This review explores recent developments in Augmented Reality (AR) that enhance user interaction via smart eyewear, with Near-Eye Displays (NEDs) at the core of delivering immersive experiences. The review first examines the key figures of merit for NEDs, including Eyebox, Field of View (FoV), Eye Relief (ER), Resolution, Brightness, Contrast Ratio, Focal Distance, Modulation Transfer Function (MTF), and Form Factor, and explains the trade-offs between them. It then discusses key NED components, including the Light Engine, responsible for generating visual content, and the Optical Combiner, which integrates real and virtual worlds. The performance of various micro-display technologies, including μ-LED, μ-OLED, LCoS, DMD/DLP, and LBS, is evaluated, considering factors like brightness, resolution, and form factor. Moreover, the review analyzes how these components and features influence the overall design and performance of Smart Eyewear, highlighting the critical interdependencies between these optical parameters. By understanding these complex relationships, this review contributes to the advancement of optical design principles in AR applications, offering valuable insights for the ongoing development of next-generation Smart Eyewear technologies.