Figure 4. a) Simultaneous VOC responses of all 20 OHL pixels exposed to a 2 x 2 pixel white square travelling from left to right at a uniform speed of 50 ms per image frame, encountering no occlusion. Pixel numbering follows Figure 1c. The black arrows (only a few shown as examples) indicate the instances in which the object has passed the corresponding OHL pixel, leading to a change in registered light intensity (from bright to dark in this case). This occurs at the corresponding pixel’s peak VOC. b) VOC response of all 20 OHL pixels exposed to a 2 x 2 pixel white square travelling from left to right and occluded by a crossing 2 x 1 red vertical strip, both moving at the same uniform speed as in a). c) Image frame of a square moving from left to right, right before occlusion by a thin red strip takes place. d) e) Image frames during occlusion by a thin red strip. f) Image frame after the occlusion event.