Eliminating chromatic aberrations of diffractive lenses in varifocal virtual reality displays

Virtual reality (VR) is regarded as the next-generation display platform for immersive human-computer interaction. To solve the long-existing problem of vergence accommodation conflict in VR, varifocal displays based on the diffractive Pancharatnam–Berry lens (PBL) are considered as one of the most promising approaches with great compatibility to current display architectures. However, the diffractive nature of PBL leads to serious chromatic aberrations in optical systems, which deteriorates the image quality and discourages its actual usage. In this article, the solution to the inherent chromatic aberration of diffractive optics is proposed. Two varifocal PBLs are configured in the VR optical system for focus adjustment and elimination of chromatic aberrations. A simple analytical model is presented to illustrate the concept. Then, the simulation of an actual pancake optical system is performed, demonstrating ∼42 times of chromatic aberration suppression. The experimental results further confirm the chromatic aberration correction and image quality improvement. The proposed method solves the fundamental problem of chromatic dispersion in diffractive optics. It is expected to have widespread applications in the fields of imaging and displays where the thin form and versatility of diffractive optics are favored.