Probabilistic Undirected Graph Based Denoising Method for Dynamic Vision Sensor

Abstract

Dynamic Vision Sensor (DVS) is a new type of neuromorphic event-based sensor, which has an innate advantage in capturing fast-moving objects. Due to the interference of DVS hardware itself and many external factors, noise is unavoidable in the output of DVS. Different from frame/image with structural data, the output of DVS is in the form of address-event representation (AER), which means that the traditional denoising methods cannot be used for the output (i.e., event stream) of the DVS. In this paper, we propose a novel event stream denoising method based on probabilistic undirected graph model (PUGM). The motion of objects always shows a certain regularity/trajectory in space and time, which reflects the spatio-temporal correlation between effective events in the stream. Meanwhile, the event stream of DVS is composed by the effective events and random noise. Thus, a probabilistic undirected graph model is constructed to describe such priori knowledge (i.e., spatio-temporal correlation). The undirected graph model is factorized into the product of the cliques energy function, and the energy function is defined to obtain the complete expression of the joint probability distribution. Better denoising effect means a higher probability (lower energy), which means the denoising problem can be transfered into energy optimization problem. Thus, the iterated conditional modes (ICM) algorithm is used to optimize the model to remove the noise. Experimental results on denoising show that the proposed algorithm can effectively remove noise events. Moreover, with the preprocessing of the proposed algorithm, the recognition accuracy on AER data can be remarkably promoted.