Speckle noise reduction in laser projection using a liquid crystal device with stacked microstructured electrodes

Laser speckle is a major challenge for laser projectors, and its reduction is crucial for improving laser display technologies. This study introduces a tunable multifocal liquid crystal microlens array (TMLCMA) with a triple-electrode structure and vertically aligned liquid crystals exhibiting negative dielectric anisotropy, designed to mitigate speckle noise. The TMLCMA operates in three modes: monofocal concave, multifocal concave, and multifocal convex, depending on the voltage driving scheme used. In monofocal modes, the speckle contrast decreases from 0.46 to 0.35; in multifocal modes, it is further reduced from 0.46 to 0.15. These multifocal properties effectively disrupt laser coherence, leading to a greater reduction in speckle noise compared to a conventional monofocal microlens array. Our results demonstrate that integrating the TMLCMA into the laser projection system significantly enhances image quality, underscoring its potential for improving laser display performance.