K-vector microscope: high-resolution testing technique for freeform holographic optical elements

This is the authors' abstract. We don't add key points for this paper.

High freeform holographic optical elements (HOEs) offer significant advantages for augmented reality (AR) displays due to their high freeform design, thin structure, and high +1st-order diffraction efficiency. Traditional optical performance measurement methods fail to meet the demands of high freeform HOEs due to limited spatial resolution and prolonged measurement time. This paper introduces what we believe to be a novel K-vector microscope (KVM) based on the geometric theory of the Bragg Condition and Coupled Wave Theory (CWT). The method provides high spatial resolution (below 50 µm) and enables rapid spatial mapping of three-dimensional k-vectors and refractive index modulation (RIM) distributions. Results on the defective reflective grating and off-axis holographic lenses demonstrate its high-precision rapid measurement capability and powerful mapping functionality. The proposed KVM effectively integrates manufacturing and testing process of freeform HOEs, thereby enabling large-scale production and practical implementation in diverse optical systems.