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.
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