Unsupervised visible-infrared person re-identification (USL-VI-ReID) aims to
match pedestrian images of the same identity from different modalities without
annotations. Existing works mainly focus on alleviating the modality gap by
aligning instance-level features of the unlabeled samples. However, the
relationships between cross-modality clusters are not well explored. To this
end, we propose a novel bilateral cluster matching-based learning framework to
reduce the modality gap by matching cross-modality clusters. Specifically, we
design a Many-to-many Bilateral Cross-Modality Cluster Matching (MBCCM)
algorithm through optimizing the maximum matching problem in a bipartite graph.
Then, the matched pairwise clusters utilize shared visible and infrared
pseudo-labels during the model training. Under such a supervisory signal, a
Modality-Specific and Modality-Agnostic (MSMA) contrastive learning framework
is proposed to align features jointly at a cluster-level. Meanwhile, the
cross-modality Consistency Constraint (CC) is proposed to explicitly reduce the
large modality discrepancy. Extensive experiments on the public SYSU-MM01 and
RegDB datasets demonstrate the effectiveness of the proposed method, surpassing
state-of-the-art approaches by a large margin of 8.76% mAP on average.

该研究提出了一种针对不同模态的行人图像进行无监督匹配的学习框架，该框架主要包括基于双向聚类匹配的跨模态簇匹配算法、模态特定和模态不可知对比学习框架以及跨模态一致性约束，实验表明该方法明显优于现有方法。