A Hybrid Space Model for Misaligned Multi-modality Image Fusion

Infrared and visible image fusion aims to integrate complementary information, such as thermal saliency from infrared imagery and fine-grained texture details from visible imagery. However, real-world multi-modal misalignment and geometric deformation often introduce severe artifacts. Most existing methods focus on feature extraction within Euclidean space, thereby neglecting the inherent hierarchical structures embedded in multimodal representations. While Euclidean space excels at preserving local structural details and supporting efficient computation, hyperbolic space is naturally suited for modeling hierarchical relationships due to its geometric properties. Building upon these observations, this paper proposes a unified framework that jointly optimizes image registration and fusion through a dual-space architecture. This architecture synergistically combines the local fidelity of Euclidean geometry with the hierarchical modeling capability of hyperbolic geometry to enhance multimodal representation learning. Specifically, this paper introduces Hyperbolic Coupled Contrastive Learning Optimization (HCCLO), which aligns and optimizes the hierarchical structures of infrared and visible embeddings in hyperbolic space. Moreover, this paper designs a task-adaptive dual-space features fusion mechanism, which dynamically balances and fuses Euclidean local features with hyperbolic hierarchical representations, thereby improving adaptability for downstream tasks. Extensive experiments on misaligned multimodal datasets demonstrate that our method achieves state-of-the-art performance, while effectively capturing both spatial dependencies and hierarchical semantics.