Fast R-CNN

Fast R-CNN

27 Sep 2015 | Ross Girshick
This paper introduces Fast R-CNN, a method for object detection that builds on previous work to efficiently classify object proposals using deep convolutional networks. Fast R-CNN improves upon R-CNN and SPPnet by employing several innovations that enhance training and testing speed while increasing detection accuracy. Key contributions include: 1. **Training Speed**: Fast R-CNN trains a very deep VGG16 network 9× faster than R-CNN and 3× faster than SPPnet. 2. **Testing Speed**: It is 213× faster at test-time compared to R-CNN. 3. **Accuracy**: It achieves a higher mAP on PASCAL VOC 2012 compared to R-CNN and SPPnet. 4. **Single-Stage Training**: Fast R-CNN uses a single-stage training algorithm that jointly learns to classify object proposals and refine their spatial locations. 5. **Multi-Task Loss**: It employs a multi-task loss function that jointly optimizes a softmax classifier and bounding-box regressors. 6. **No Disk Storage**: It eliminates the need for disk storage of feature caching. The architecture of Fast R-CNN processes an entire image and multiple regions of interest (RoIs) through a series of convolutional and max pooling layers. Each RoI is then pooled into a fixed-length feature vector, which is fed into fully connected layers to produce softmax probability estimates and refined bounding-box positions. The method uses hierarchical sampling for mini-batch construction and backpropagation through the RoI pooling layer to efficiently compute derivatives. Experiments on PASCAL VOC datasets demonstrate that Fast R-CNN achieves state-of-the-art mAP while being significantly faster and more accurate than previous methods. The paper also explores various design choices, such as multi-task training, scale invariance, and the impact of proposal density, providing insights into the effectiveness of these techniques.This paper introduces Fast R-CNN, a method for object detection that builds on previous work to efficiently classify object proposals using deep convolutional networks. Fast R-CNN improves upon R-CNN and SPPnet by employing several innovations that enhance training and testing speed while increasing detection accuracy. Key contributions include: 1. **Training Speed**: Fast R-CNN trains a very deep VGG16 network 9× faster than R-CNN and 3× faster than SPPnet. 2. **Testing Speed**: It is 213× faster at test-time compared to R-CNN. 3. **Accuracy**: It achieves a higher mAP on PASCAL VOC 2012 compared to R-CNN and SPPnet. 4. **Single-Stage Training**: Fast R-CNN uses a single-stage training algorithm that jointly learns to classify object proposals and refine their spatial locations. 5. **Multi-Task Loss**: It employs a multi-task loss function that jointly optimizes a softmax classifier and bounding-box regressors. 6. **No Disk Storage**: It eliminates the need for disk storage of feature caching. The architecture of Fast R-CNN processes an entire image and multiple regions of interest (RoIs) through a series of convolutional and max pooling layers. Each RoI is then pooled into a fixed-length feature vector, which is fed into fully connected layers to produce softmax probability estimates and refined bounding-box positions. The method uses hierarchical sampling for mini-batch construction and backpropagation through the RoI pooling layer to efficiently compute derivatives. Experiments on PASCAL VOC datasets demonstrate that Fast R-CNN achieves state-of-the-art mAP while being significantly faster and more accurate than previous methods. The paper also explores various design choices, such as multi-task training, scale invariance, and the impact of proposal density, providing insights into the effectiveness of these techniques.
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