# AlignFreeNet: Is Cross-Modal Pre-Alignment Necessary? An End-to-End Alignment-Free Lightweight Network for Visible-Infrared Object Detection

arXiv: https://arxiv.org/abs/2507.20146 · HTML: https://mlsanity.com/paper/2507.20146/

## Key facts

- Cited by 1 papers in the map (data through 14 Oct 2026).
- Builds on 23 of its 41 references that are in the map.
- First posted on arXiv 27 Jul 2025.

## Builds on (most cited first, 23 of 23)

- [Mamba: Linear-Time Sequence Modeling with Selective State Spaces](https://mlsanity.com/paper/2312.00752/) (2023)
- [Transformers are SSMs: Generalized Models and Efficient Algorithms Through Structured State Space Duality](https://mlsanity.com/paper/2405.21060/) (2024)
- [VMamba: Visual State Space Model](https://mlsanity.com/paper/2401.10166/) (2024)
- [Object Detection in 20 Years: A Survey](https://mlsanity.com/paper/1905.05055/) (2019)
- [Target-aware Dual Adversarial Learning and a Multi-scenario Multi-Modality Benchmark to Fuse Infrared and Visible for Object Detection](https://mlsanity.com/paper/2203.16220/) (2022)
- [CMX: Cross-Modal Fusion for RGB-X Semantic Segmentation with Transformers](https://mlsanity.com/paper/2203.04838/) (2022)
- [CDDFuse: Correlation-Driven Dual-Branch Feature Decomposition for Multi-Modality Image Fusion](https://mlsanity.com/paper/2211.14461/) (2022)
- [Drone-based RGB-Infrared Cross-Modality Vehicle Detection via Uncertainty-Aware Learning](https://mlsanity.com/paper/2003.02437/) (2020)
- [Equivariant Multi-Modality Image Fusion](https://mlsanity.com/paper/2305.11443/) (2023)
- [Cross-Modality Fusion Transformer for Multispectral Object Detection](https://mlsanity.com/paper/2111.00273/) (2021)
- [ICAFusion: Iterative Cross-Attention Guided Feature Fusion for Multispectral Object Detection](https://mlsanity.com/paper/2308.07504/) (2023)
- [Fusion-Mamba for Cross-modality Object Detection](https://mlsanity.com/paper/2404.09146/) (2024)
- [C2Former: Calibrated and Complementary Transformer for RGB-Infrared Object Detection](https://mlsanity.com/paper/2306.16175/) (2023)
- [Translation, Scale and Rotation: Cross-Modal Alignment Meets RGB-Infrared Vehicle Detection](https://mlsanity.com/paper/2209.13801/) (2022)
- [SuperYOLO: Super Resolution Assisted Object Detection in Multimodal Remote Sensing Imagery](https://mlsanity.com/paper/2209.13351/) (2022)
- [Infrared and Visible Image Fusion: From Data Compatibility to Task Adaption](https://mlsanity.com/paper/2501.10761/) (2025)
- [Learning a Graph Neural Network with Cross Modality Interaction for Image Fusion](https://mlsanity.com/paper/2308.03256/) (2023)
- [DMM: Disparity-guided Multispectral Mamba for Oriented Object Detection in Remote Sensing](https://mlsanity.com/paper/2407.08132/) (2024)
- [COMO: Cross-Mamba Interaction and Offset-Guided Fusion for Multimodal Object Detection](https://mlsanity.com/paper/2412.18076/) (2024)
- [WaveMamba: Wavelet-Driven Mamba Fusion for RGB-Infrared Object Detection](https://mlsanity.com/paper/2507.18173/) (2025)
- [Guided Hybrid Quantization for Object detection in Multimodal Remote Sensing Imagery via One-to-one Self-teaching](https://mlsanity.com/paper/2301.00131/) (2022)
- [FD2-Net: Frequency-Driven Feature Decomposition Network for Infrared-Visible Object Detection](https://mlsanity.com/paper/2412.09258/) (2024)
- [HTD-Mamba: Efficient Hyperspectral Target Detection with Pyramid State Space Model](https://mlsanity.com/paper/2407.06841/) (2024)

## Built on by (most cited first, 1 of 1)

- [Bridging Multimodal Fusion and Expert Routing via Spectral Reliability Descriptors for Robust Object Detection](https://mlsanity.com/paper/2606.01173/) (2026)

## Abstract (arXiv)

Cross-modal misalignments, such as spatial offsets, resolution discrepancies, and semantic deficiencies, frequently occur in visible-infrared object detection (VI-OD). To mitigate this, existing methods are typically adapted into an alignment-based fusion paradigm, in which an explicit pixel- or feature-level alignment module is inserted before cross-modal fusion. However, pixel-level alignment struggles to cope with severe or mixed misalignments, whereas feature-level alignment often introduces undesirable noise into fused representations under such conditions, ultimately limiting detection performance. In this paper, we propose a novel alignment-free network (AlignFreeNet) for VI-OD. Differing from prior methods, AlignFreeNet abandons any explicit alignment and instead adopts an alignment-free fusion paradigm. Specifically, AlignFreeNet comprises two core modules: variation-guided cross-modal compensation (VCC) and frequency-guided cross-modal fusion (FCF). VCC adaptively feeds the compensated information derived from cross-modal discrepancies back into each modality, enhancing visible and infrared representations without the noise caused by explicit alignment. FCF achieves robust cross-modal fusion by suppressing task-irrelevant redundancy via frequency-domain gating, effectively mitigating noise introduced in the process. Moreover, VCC and FCF jointly exploit low- and high-frequency cues to preserve foreground contours in fused representations, effectively mitigating cross-modal blending caused by severe mixed misalignments. Extensive evaluations on DVTOD, M3FD, and DroneVehicle demonstrate that our AlignFreeNet achieves state-of-the-art performance under severe mixed misalignment conditions, highlighting its robustness and generalization.