Multifocal displays:review and prospect

Conventional stereoscopic three-dimensional displays suffer from vergenceaccommodation conflict because the stimulus to accommodation is fixed by the display panel and viewing optics,but that to vergence changes with image contents.With the recent rapid development of head-mounted displays,several methods have been proposed to offer the accommodation cues,among which multifocal display technology is an effective and practical solution.The first two decades of this century has witnessed the fast growth of multifocal displays from basic concept to mature implementations.This review systematically presents the state-of-the-art multifocal display design and development.Firstly,a comprehensive classification of numerous potential optical architectures to provide the multiplanar functionality is introduced,based on how the information is multiplexed and how the focal planes are generated.Next,the strengths and obstacles of reported or potential designs in each category are analyzed and compared with each other.In addition to enabling optics,the image rendering approaches for the multifocal planes are also described.This review presents a sufficient collection of past designs and is expected to offer a roadmap for future research and development of multifocal displays.

Advanced liquid crystal devices for augmented reality and virtual reality displays:principles and applications

Liquid crystal displays(LCDs)and photonic devices play a pivotal role to augmented reality(AR)and virtual reality(VR).The recently emerging high-dynamic-range(HDR)mini-LED backlit LCDs significantly boost the image quality and brightness and reduce the power consumption for VR displays.Such a light engine is particularly attractive for compensating the optical loss of pancake structure to achieve compact and lightweight VR headsets.On the other hand,high-resolution-density,and high-brightness liquid-crystal-on-siilicon(LCoS)is a promising image source for the see-through AR displays,especially under high ambient lighting conditions.Meanwhile,the high-speed LCoS spatial light modulators open a new door for holographic displays and focal surface displays.Finally,the ultrathin planar diffractive LC optical elements,such as geometric phase LC grating and lens,have found useful applications in AR and VR for enhancing resolution,widening fiield-of-view,suppressing chromatic aberrations,creating multiplanes to overcome the vergence-accommodation conflict,and dynamic pupil steering to achieve gaze-matched Maxwellian displays,just to name a few.The operation principles,potential applications,and future challenges of these advanced LC devices will be discussed.