Normality Prior Guided Multi-Semantic Fusion Network for Unsupervised Image Anomaly Detection

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Main Authors: Xu, Muhao, Zhou, Xueying, Gao, Xizhan, Song, Weiye, Feng, Guang, Niu, Sijie
Format: Preprint
Published: 2025
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_version_ 1866911019033427968
author Xu, Muhao
Zhou, Xueying
Gao, Xizhan
Song, Weiye
Feng, Guang
Niu, Sijie
author_facet Xu, Muhao
Zhou, Xueying
Gao, Xizhan
Song, Weiye
Feng, Guang
Niu, Sijie
contents Recently, detecting logical anomalies is becoming a more challenging task compared to detecting structural ones. Existing encoder decoder based methods typically compress inputs into low-dimensional bottlenecks on the assumption that the compression process can effectively suppress the transmission of logical anomalies to the decoder. However, logical anomalies present a particular difficulty because, while their local features often resemble normal semantics, their global semantics deviate significantly from normal patterns. Thanks to the generalisation capabilities inherent in neural networks, these abnormal semantic features can propagate through low-dimensional bottlenecks. This ultimately allows the decoder to reconstruct anomalous images with misleading fidelity. To tackle the above challenge, we propose a novel normality prior guided multi-semantic fusion network for unsupervised anomaly detection. Instead of feeding the compressed bottlenecks to the decoder directly, we introduce the multi-semantic features of normal samples into the reconstruction process. To this end, we first extract abstract global semantics of normal cases by a pre-trained vision-language network, then the learnable semantic codebooks are constructed to store representative feature vectors of normal samples by vector quantisation. Finally, the above multi-semantic features are fused and employed as input to the decoder to guide the reconstruction of anomalies to approximate normality. Extensive experiments are conducted to validate the effectiveness of our proposed method, and it achieves the SOTA performance on the MVTec LOCO AD dataset with improvements of 5.7% in pixel-sPRO and 2.6% in image-AUROC. The source code is available at https://github.com/Xmh-L/NPGMF.
format Preprint
id arxiv_https___arxiv_org_abs_2506_18544
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Normality Prior Guided Multi-Semantic Fusion Network for Unsupervised Image Anomaly Detection
Xu, Muhao
Zhou, Xueying
Gao, Xizhan
Song, Weiye
Feng, Guang
Niu, Sijie
Computer Vision and Pattern Recognition
Recently, detecting logical anomalies is becoming a more challenging task compared to detecting structural ones. Existing encoder decoder based methods typically compress inputs into low-dimensional bottlenecks on the assumption that the compression process can effectively suppress the transmission of logical anomalies to the decoder. However, logical anomalies present a particular difficulty because, while their local features often resemble normal semantics, their global semantics deviate significantly from normal patterns. Thanks to the generalisation capabilities inherent in neural networks, these abnormal semantic features can propagate through low-dimensional bottlenecks. This ultimately allows the decoder to reconstruct anomalous images with misleading fidelity. To tackle the above challenge, we propose a novel normality prior guided multi-semantic fusion network for unsupervised anomaly detection. Instead of feeding the compressed bottlenecks to the decoder directly, we introduce the multi-semantic features of normal samples into the reconstruction process. To this end, we first extract abstract global semantics of normal cases by a pre-trained vision-language network, then the learnable semantic codebooks are constructed to store representative feature vectors of normal samples by vector quantisation. Finally, the above multi-semantic features are fused and employed as input to the decoder to guide the reconstruction of anomalies to approximate normality. Extensive experiments are conducted to validate the effectiveness of our proposed method, and it achieves the SOTA performance on the MVTec LOCO AD dataset with improvements of 5.7% in pixel-sPRO and 2.6% in image-AUROC. The source code is available at https://github.com/Xmh-L/NPGMF.
title Normality Prior Guided Multi-Semantic Fusion Network for Unsupervised Image Anomaly Detection
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2506.18544