Phase measurement of surface-bearing holographic optical elements

Holographic optical elements (HOEs) manipulate light via refractive index modulation and are widely used in imaging, display, and extended reality systems. However, accurate phase characterization remains challenging due to the coupling of surface figure and internal refractive index effects. In this Letter, we present a phase measurement method based on four-step phase-shifting interferometry that separately measures the total and surface phase distributions of HOEs by leveraging their angular selectivity. The internal phase component, induced by refractive index modulation, is decoded from the total phase to eliminate the surface effect. A phase compensation experiment is conducted to validate the accuracy of the measured phase, demonstrating the effectiveness and practicality of the proposed method for HOEs phase characterization and correction.