Depth expansion of a light-field head-mounted display using dual-focal lens array

Light-field head-mounted displays (HMDs) can reconstruct focus-adjustable three-dimensional (3D) images, thereby reducing vergence-accommodation conflict. However, the narrow depth of field (DOF), which dictates the range within which a 3D image can be clearly displayed, poses significant challenges. We propose a light-field HMD equipped with an expanded DOF using a dual-focal lens array comprising microlenses of different focal lengths arranged in a checkerboard pattern. Simulation analysis revealed that the proposed light-field HMD has two depth-dependent peaks in the modulation transfer function. Furthermore, we developed a monocular optical bench prototype and confirmed that the DOF was expanded by using two different peaks corresponding to the 3D image depth.