Globally Optimal Contrast Maximisation for Event-based Motion Estimation

Abstract

Contrast maximisation estimates the motion captured in an event stream by maximising the sharpness of the motion compensated event image. To carry out contrast maximisation, many previous works employ iterative optimisation algorithms, such as conjugate gradient, which require good initialisation to avoid converging to bad local minima. To alleviate this weakness, we propose a new globally optimal event-based motion estimation algorithm. Based on branch-and-bound (BnB), our method solves rotational (3DoF) motion estimation on event streams, which supports practical applications such as video stabilisation and attitude estimation. Underpinning our method are novel bounding functions for contrast maximisation, whose theoretical validity is rigorously established. We show concrete examples from public datasets where globally optimal solutions are vital to the success of contrast maximisation. Despite its exact nature, our algorithm is currently able to process a 50,000 event input in 300 seconds (a locally optimal solver takes 30 seconds on the same input), and has the potential to be further speeded-up using GPUs.

15 pages, 8 figures

References in corpus (5)

• EV-FlowNet: Self-Supervised Optical Flow Estimation for Event-based Cameras
• Event-based, 6-DOF Camera Tracking from Photometric Depth Maps
• Event-Based Motion Segmentation by Motion Compensation
• Focus Is All You Need: Loss Functions For Event-based Vision
• Event-based Star Tracking via Multiresolution Progressive Hough Transforms