Compact vari-focal augmented reality display based on ultrathin, polarization-insensitive, and adaptive liquid crystal lens

Despite the recent advances in augmented reality (AR), which has shown the potential to significantly impact on our daily lives by offering a new way to manipulate and interact with virtual information, minimizing visual discomfort due to the vergence–accommodation conflict remains a challenge. Emerging AR technologies often exploit focus-tunable optics to address this problem. Although they demonstrated improved depth perception by enabling proper focus cues, a bulky form factor of focus–tunable optics prevents their use in the form of a pair of eyeglasses. Here, we propose a novel optical configuration for a compact vari-focal AR display which deliberately utilizes the zeroth and first diffraction orders of the LC lens to produce two foci: one for a real object and the other for a virtual object with addressable focal planes. The prototype AR glasses can adjust the accommodation distance of the virtual image, mitigating the vergence–accommodation conflict without substantially compromising the form factor or image quality. In addition, we describe the design, fabrication, and characterization of an ultrathin, polarization-insensitive focus-tunable liquid crystal (LC) diffractive lens with a large aperture, a low weight, and a low operating voltage. We show that the polarization dependence of the lens, which is an inherent optical property of LC lenses, can be insensitive using the trilayer birefringent materials and by aligning the optical axes of each birefringent material at a specific angle. The polarization insensitivity eliminates the need for a polarizer, thus further reducing the form factor of the optical system. This novel approach offers significantly reduced complexity for designing AR glasses with addressable focal planes. These technologies for ultrathin lens and AR display show promising potential for developing compact optical systems in various applications.