What is RPN in Faster R-CNN?

RPN (Region Proposal Network) in Faster R-CNN is a neural network that generates region proposals (areas of interest) in an image where objects are likely to be found. It replaces traditional proposal generation methods (such as Selective Search), making the process faster and more integrated.

Key features of RPN:

• Operates as a convolutional layer on top of features extracted from the backbone network.
• Predicts multiple anchors with different scales and aspect ratios for each position on the feature map.
• For each anchor, predicts the probability of containing an object and adjusts the bounding box coordinates.

Thus, RPN generates a set of candidate object regions, which are then passed to the next stage of Faster R-CNN for classification and refinement.