Oriented FAST and Rotated BRIEF (ORB) was developed at OpenCV labs by Ethan Rublee, Vincent Rabaud, Kurt Konolige, and Gary R. Bradski in 2011, as an efficient and viable alternative to SIFT and SURF. ORB was conceived mainly because SIFT and SURF are patented algorithms. ORB, however, is free to use.
ORB performs as well as SIFT on these tasks (and better than SURF), while being almost two order of magnitude faster. ORB builds on the well-known FAST keypoint detector and the BRIEF descriptor. Both these techniques are attractive because of their good performance and low cost. ORB's main contributions are as follows:
The addition of a fast and accurate orientation component to FAST
The efficient computation of oriented BRIEF features
Analysis of variance and correlation of oriented BRIEF features
A learning method for decorrelating BRIEF features under rotational invariance, leading to better performance in nearest-neighbor applications