What does FPN in SSD MobileNet V2 FPNLite 320x320 stand for?

Question

I was looking at the TensorFlow 2.0 Detection Zoo recently and found the SSD MobileNet V2 FPNLite 320x320 pre-trained model and was wondering what the FPN part in "FPNLite" means/stands for.

Answer 1

It stands for Feature Pyramid Network. Its a subnetwork which outputs feature maps of different resolutions. An explanation of FPN using detectron2 as an example is here: https://medium.com/@hirotoschwert/digging-into-detectron-2-part-2-dd6e8b0526e

Answer 2

A Feature Pyramid Network, or FPN, is a feature extractor that takes a single-scale image of an arbitrary size as input, and outputs proportionally sized feature maps at multiple levels, in a fully convolutional fashion. This process is independent of the backbone convolutional architectures.