Fully Rotation-Equivariant Spectral-Spatial Learning for Multispectral Object Detection

2026-07-06

AI Summary

Existing multispectral object detection methods are limited by discrete spectral modeling, unstable cross-scale spectral-spatial feature fusion, and a lack of rotational equivariance for arbitrarily oriented objects. This work proposes FressDet, the first fully rotation-equivariant framework for multispectral detection. It achieves continuous spectral modeling through implicit resampling that preserves spectral ordering, introduces a rotation-equivariant consistency weighting mechanism for robust multiscale feature fusion, and incorporates an orientation-aware detection head without parameter duplication. Evaluated on three public benchmarks, FressDet attains state-of-the-art performance with 93% fewer parameters, significantly enhancing robustness to rotational perturbations and generalization capability.

Abstract

Existing multispectral detectors are limited by discrete spectral processing, a scale-dependent shift in the relative reliability of spectral and spatial cues across pyramid levels, and the lack of explicit rotation-equivariant geometric priors for arbitrarily oriented objects. To tackle these limitations, we propose FressDet, a fully rotation-equivariant spectral-spatial learning framework for multispectral object detection, capable of capturing the continuous, ordered nature of spectral structure and enabling reliable spectral-spatial fusion across pyramid levels under arbitrary in-plane rotations. FressDet integrates three complementary components. Spectral Implicit Warp (SpeIW) enables query-based spectral resampling via a coordinate-conditioned implicit field, yielding a monotone, order-preserving warp. Rotation-Equivariant Consistency Weighting (ReCoW) adaptively fuses spectral and spatial branches based on branch reliability, reinforcing informative cues while suppressing noise across pyramid levels. The oriented-aware head exploits group-indexed features to stably predict oriented objects without parameter replication. Taken together, FressDet learns more discriminative and robust spectral-spatial representations even under rotational perturbations. By achieving state-of-the-art performance with 93% fewer parameters on three public benchmarks, FressDet demonstrates its effectiveness and generalizability.

Problem

• multispectral object detection
• rotation equivariance
• spectral-spatial fusion
• oriented objects
• feature pyramid

Innovation

• rotation-equivariant
• spectral-spatial fusion
• implicit spectral resampling
• multispectral object detection
• feature pyramid