The Basics of Object Detection: YOLO, SSD, R-CNN

Overview of how object detection works, and where to get started

Photo by Henry Dick on Unsplash

Note: This assumes you have a general idea of what convolutional neural networks are. If you need a refresher, this IBM post is excellent.

You know how convolutional neural networks (or CNNs) detect and classify images. But you can expand on that CNN to detect objects within that image.

How is object detection different from image recognition?

You have an image of 4 cows. Image recognition detects the image as a whole. It says the image is classified as a cow.

However, image recognition can’t tell where in the image the cow is. Furthermore, it won’t be able to tell that there are 4 cows instead of 1.

On a side note, object detection is NOT meant for counting. There are other computer vision techniques like density estimation and extracting patches that are meant for counting. Object detection just detects if there are multiple objects in the same image.

Why do I need to learn this? How is this useful in the real world?

There are a lot of scammers. Some get by with using fake cashier’s checks or dollar bills. Image detection can only say whether the fake replica looks like a…