提出新自监督方法,让模型在保持不变性的同时学会保留变换信息。
Self-Supervised Learning Based on Transformed Image Reconstruction for Equivariance-Coherent Feature Representation
- 通过重建图像旋转过程中的中间状态,学习兼具不变性和等变性的特征。
- 在合成等变性基准上显著提升性能,下游任务如分割、检测也更优。
- 可无缝接入iBOT、DINOv2等主流自监督框架,适合需要变换信息的视觉任务。
自监督学习(SSL)在构建图像表示方面取得显著进展,但通常只学习对变换具有不变性的特征,从而丢弃了某些计算机视觉任务所需的变换信息。尽管近期方法尝试通过特征空间中的线性算子学习等变特征,却引入了限制性假设,影响灵活性与泛化能力。本文提出一种更弱的图像与特征空间间变换关系定义——等变一致性(equivariance-coherence),并设计一种新的辅助任务:通过重建变换路径上的中间状态来学习等变一致性表示。例如,在30度旋转训练中,同时重建10度和20度的旋转状态。该方法要求利用增强中的变换信息进行重建,而非抑制它,从而促使特征包含变换信息。我们的方法将特征向量分解为不变部分和等变部分,分别使用标准SSL损失和重构损失进行训练。实验表明,该方法在合成等变性基准上表现显著提升,同时在需要不变性表示的下游任务(如分割、检测、深度估计、视频密集预测)中保持竞争力。该框架可无缝集成至现有SSL方法(如iBOT、DINOv2),并在多种任务中持续提升性能,为增强现有自监督方法的等变能力提供了一种实用方案。
原文摘要 · Abstract (English)
Self-supervised learning (SSL) methods have achieved remarkable success in learning image representations allowing invariances in them - but therefore discarding transformation information that some computer vision tasks actually require. While recent approaches attempt to address this limitation by learning equivariant features using linear operators in feature space, they impose restrictive assumptions that constrain flexibility and generalization. We introduce a weaker definition for the transformation relation between image and feature space denoted as equivariance-coherence. We propose a novel SSL auxiliary task that learns equivariance-coherent representations through intermediate transformation reconstruction, which can be integrated with existing joint embedding SSL methods. Our key idea is to reconstruct images at intermediate points along transformation paths, e.g. when training on 30-degree rotations, we reconstruct the 10-degree and 20-degree rotation states. Reconstructing intermediate states requires the transformation information used in augmentations, rather than suppressing it, and therefore fosters features containing the augmented transformation information. Our method decomposes feature vectors into invariant and equivariant parts, training them with standard SSL losses and reconstruction losses, respectively. We demonstrate substantial improvements on synthetic equivariance benchmarks while maintaining competitive performance on downstream tasks requiring invariant representations. The approach seamlessly integrates with existing SSL methods (iBOT, DINOv2) and consistently enhances performance across diverse tasks, including segmentation, detection, depth estimation, and video dense prediction. Our framework provides a practical way for augmenting SSL methods with equivariant capabilities while preserving invariant performance.
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