Color-selective geometric-phase lenses for focusing and imaging based on liquid crystal polymer films

• Published in: Optics express Vol. 30; no. 2; pp. 2487 - 2502
• Main Authors: Li, Lingshan, Shi, Shuojia, Kim, Jihwan, Escuti, Michael J
• Format: Journal Article
• Language: English
• Published: United States 17.01.2022
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.444578

The geometric-phase lens (GPLs) with small form factor compared to traditional refractive lenses has been identified as a compelling solution in augmented-/virtual-/mixed-reality (AR/VR/MR) headsets. Formed either with liquid crystals (LCs) or metasurfaces, the GPL is a type of emerging leading technology that implements the arbitrary aspheric phase to realize low loss and minimal ghosting. However, the inherent chromatic abberation (CA) of GPLs can significantly degrade the image quality. A possible solution is the independent spectral phase implementation for RGB. In this work, we propose the design of three types of multi-twist LC based color-selective GPLs (CS-GPLs), exhibiting highly chromatic efficiency spectra with diameter 30 mm, focal length around 41.2~mm, and F -number 1.37. Through theoretical and experimental validation, each type of CS-GPL manifests high diffraction efficiency (>91%) on respective primary color of orthogonal polarization and high transmission on the complementary color of input polarization. The triplet composed by RGB CS-GPLs demonstrates relative contrast ratio and minimal ghosting. The strong color and polarization dependency of CS-GPLs not only provide a novel technique to mitigate CA but also offer more design freedom in the AR/VR/MR polarization and imaging system.