Dual-focal display through polarization-directed birefringence for compact virtual reality

A compact dual-focal virtual reality display is presented to provide discrete accommodation cues for mitigating the vergence-accommodation conflict. The architecture combines a folded-pancake optical path with an electrically switchable liquid-crystal polarization modulator and a YVO₄ birefringent doublet, enabling two steady-state focal states within a 15-mm total track length. A monocular prototype was fabricated and experimentally characterized, achieving diagonal fields of view of 43.61° and 46.03° at nominal -4 D and -0.2 D, respectively. Through-focus measurements yielded mean focal positions of -3.99 D and -0.19 D over three repeated scans. Peak spatial ghost-image intensity ratios were 2.2% and 2.3%, respectively. An idealized binary-weighted model further examines multi-focal scaling and associated practical constraints.