2017

Focal Loss for Dense Object Detection

Lin, Tsung-Yi, Goyal, Priya, Girshick, Ross et al.

Understand

The highest accuracy object detectors to date are based on a two-stage approach popularized by R-CNN, where a classifier is applied to a sparse set of candidate object locations.

  • In contrast, one-stage detectors that are applied over a regular, dense sampling of possible object locations have the potential to be faster and simpler, but have trailed the accuracy of two-stage detectors thus far.
  • In this paper, we investigate why this is the case.
  • We discover that the extreme foreground-background class imbalance encountered during training of dense detectors is the central cause.

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