F3Net: Adaptive Frequency Feature Filtering Network for Multimodal Remote Sensing Image Registration

Multimodal remote sensing image registration is crucial for multimodal information fusion and applications. The significant nonlinear appearance difference between multimodal images caused by the various imaging mechanisms dramatically increases the challenge of image registration. This article proposes an adaptive frequency feature filtering network (F3Net) for cross-modal remote sensing image registration. On the one hand, F3Net explicitly explores the useful frequency components across modal images based on multilevel deep features. On the other hand, F3Net can take advantage of the nonlocal receptive fields by frequency modulation for feature learning and boosting image registration performances. F3Net inserts frequency feature filtering (F3) modules in multilevel deep features. Specifically, F3Net first performs the fast Fourier transform (FFT) for deep features. Then, F3Net designs a frequency attention (FA) module to adaptive enhance the shared and discriminative frequency features between multimodal images while suppressing the frequency components that hinder the cross-modal image registration. In addition, F3Net adopts multiscale frequency filtering fusion to facilitate discriminative feature learning, including global frequency feature filtering (GF3) based on the global image spectrum and local frequency feature filtering (LF3) based on the spectrum of stacked image regions. Experimental results on many remote sensing images have demonstrated the efficiency of the F3Net on multimodal image registration.