Inline dual-phase modulation method for a compact lensless holographic display

This study presents an innovative inline dual-phase modulation technique for compact lensless holographic displays. By utilizing a single spatial light modulator (SLM) and employing two-phase components derived from double-phase holography symmetrically positioned in the upper and lower halves of the SLM, we achieve a holographic display through the superposition of a digital phase grating. This approach eliminated the need for bulky 4-F systems, resulting in a compact optical setup. Numerical simulations demonstrate that the proposed method provides high-precision image reconstruction using a single SLM, and the experimental results confirm its efficacy in achieving image reconstruction with minimal speckle noise compared to the conventional iterative random phase method. Additionally, incorporating an initial random phase reduces artifacts in practical experimental settings, producing less speckle noise than the conventional iterative random phase method. Moreover, based on the proposed method, a beam splitter was used for further coupling in the reconstruction plane, resulting in an expanded display area while maintaining a compact system. The proposed method can simplify various holographic display systems, including projection, near-eye, and 3D displays.