Holographic Projection Display Enlargement via Polarization-Grating Beam Steering with Fast-Response Liquid Crystal Pi-Cells.

This paper presents a holographic display architecture that integrates polarization gratings with fast-response nematic liquid crystal (LC) pi-cells to achieve fast switching and the simultaneous visual perception of multiple high-quality discrete beam-steering positions, enabling visual enlargement of holographic projected images through spatiotemporal tiling, thereby overcoming the limited projection coverage achieved using a single spatial light modulator (SLM). The system integrates voltage-controlled nematic LC pi-cell phase shifters that dynamically modulate the polarization state to achieve precise beam steering in a selected diffraction order with 80% optical transmittance and a rapid response (<3 ms). By synchronizing the voltage driving waveforms applied to the nematic LC pi-cells with the refresh rate of the SLM, the reconstructed holographic images in the replay field can be steered among multiple spatial locations in real time. Under low-frequency driving, individual holographic subframes are sequentially displayed at distinct spatial positions. At higher driving frequencies, multiple holographic projected images are visually perceived as being displayed at the same time, creating the impression of an enlarged holographic projection display area, corresponding to a 4-fold increase in the effective display area compared with a conventional holographic projection display using a single SLM at the same far-field distance. Experimental results demonstrate beam steering among four discrete positions with millisecond-scale response time, forming either a linear array (1D) or a two-by-two spatial configuration (2D). Overall, this approach provides a scalable route toward high-speed, wide-angle, and visually large-area holographic displays through the integration of polarization gratings with fast-response nematic LC devices.