Proposed use lightweight generic random ferns (LGRF), a fast keypoint classifier designed for multi-target augmented reality (AR) on mobile devices. LGRF uses binary features of image patches for both object recognition and keypoint matching of multiple objects, and stores probabilities in a single bit representation to reduce memory requirements. As a result, LGRF can perform simultaneous object recognition and keypoint matching in real time with low memory consumption, making it suitable for multi-target AR on mobile devices.Introduction: A core challenge in augmented reality (AR) is the efficient calculation of positions for virtual objects on real-world images. In this regard, keypoints have proven to be more useful than other image features, because of their robustness under viewpoint variation and partial occlusion. As keypoint recognition has become more commonplace, two major approaches have emerged.The first approach relies on local descriptors that are meant to be invariant, or at least robust, over affine deformations. Of these, the SIFT descriptor proposed in [1] has performed remarkably well and become a benchmark for other techniques. Unfortunately, like these other techniques, SIFT incurs a high computational cost at runtime, and is not yet suitable for real-time applications.The second approach recasts keypoint recognition as a classification problem. In short, the set of all possible appearances of each keypoint is considered a class, and is used to train a classifier. By shifting the computational burden from runtime to an offline training phase, this approach can achieve real-time keypoint recognition. In [2, 3], randomised trees (RT) and random ferns (RF) proved fast enough for frame-rate performance at high rates of recognition, making them suitable for AR applications. Unfortunately, these methods require significant memory at runtime (all the more when applied to multiple targets), and are further limited by their serialisation of object recognition and keypoint matching. For these reasons, they are ill suited to current mobile hardware.In this Letter, we propose a new extension of RF called lightweight generic random ferns (LGRF). This method directly addresses the memory and performance problems of RT/RF, and is very well suited to current mobile hardware.