arXiv Computer Vision By Julien Combes (SVH, Michelin), Jean-Fran\c{c}ois Coeurjolly (SVH), Alexandre Derville (Michelin)

Active Learning under Simulated Class Imbalance and Label Shift in Binary Semantic Segmentation

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The paper investigates how class imbalance and label shift—common in machine vision due to abundant defect‑free images and limited storage—affect active learning for binary semantic segmentation. It introduces a reproducible simulation protocol that independently varies these two imbalance factors using two open‑source datasets. Four active‑learning strategies (random, entropy‑based, core‑set, and galaxy sampling) are compared, showing that entropy‑based and core‑set methods generally outperform random sampling even under severe imbalance, while quantifying efficiency loss under strong label shift.

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arXiv Computer Vision
Sep 18

Distance to Class Prototypes: Active Learning for Object Detection

The paper introduces a new active learning signal for object detection that relies on a supervised contrastive term added to the training objective. This term shapes an embedding space where distance reflects class membership, allowing an unlabeled detection to be scored by its distance from the predicted category’s region weighted by confidence—all from a single forward pass of one network. Experiments on PASCAL VOC and MS‑COCO show that this criterion outperforms the standard posterior and remains competitive with ensemble‑based methods while incurring only a modest 8.3% increase in parameters.

By Licheng Zhang, Zheng Gong