Theoretical Modeling and Wave-Optical Analysis of Diffraction Effects in Risley-Prism Multi-Beam Scanners: Towards Ultimate Resolution and Field-of-View Limits

Current analysis of Risley-prism beam steering systems is dominated by geometric optical models, which neglect critical physical effects—including diffraction, wavefront distortion, and coherence—especially in multi-beam, wide-angle steering scenarios. This omission creates a significant theoretical gap in predicting ultimate performance limits. To address this, we present a novel theoretical framework: a wave-optical propagation model that rigorously integrates vector diffraction theory with the refractive transformations of prisms. Through comprehensive simulations, this model predicts fundamental wave-optical limitations, including effective beam waist broadening, generation of structured side-lobes, and field-dependent degradation of the modulation transfer function (MTF) across the field of regard (FOR). These effects define the ultimate resolution and scan fidelity boundaries of such systems. Finally, based on these insights, we propose novel non-mechanical tuning strategies—currently at the theoretical exploration stage—to mitigate these performance limits, paving the way for next-generation high-precision scanners for LiDAR and freespace optical communication applications.