Existing approaches towards anomaly detection~(AD) often rely on a substantial amount of anomaly-free data to train representation and density models. However, large anomaly-free datasets may not always be available before the inference stage; in which case an anomaly detection model must be trained with only a handful of normal samples, a.k.a. few-shot anomaly detection (FSAD). In this paper, we propose a novel methodology to address the challenge of FSAD which incorporates two important techniques. Firstly, we employ a model pre-trained on a large source dataset to initialize model weights. Secondly, to ameliorate the covariate shift between source and target domains, we adopt contrastive training to fine-tune on the few-shot target domain data. To learn suitable representations for the downstream AD task, we additionally incorporate cross-instance positive pairs to encourage a tight cluster of the normal samples, and negative pairs for better separation between normal and synthesized negative samples. We evaluate few-shot anomaly detection on on 3 controlled AD tasks and 4 real-world AD tasks to demonstrate the effectiveness of the proposed method.

在本研究中，我们提出了一种新的方法来解决少样本异常检测（FSAD）的挑战，该方法包括使用预先训练的模型初始化权重，采用对比性训练来优化少样本领域数据，以及使用正样本对齐和负样本分离等技术来学习适合于异常检测的表示。我们对3个受控异常检测任务和4个真实世界异常检测任务进行了评估，以展示所提方法的有效性。

COFT-AD：对少样本异常检测的对比微调