Figure 3. a) Snapshots of the stimulated occlusion experiment where a white stationary square is obstructed by a moving red square. b) VOC responses with time of the four OHL pixels 11, 12, 13, 14 (pixel position according to Figure 1c) of our proof-of-concept 20-pixel OHL sensor perceiving a white 2 x 2 pixel square being temporarily blocked by a red square of the same size moving from right to left, as depicted by the image frames 1-5 in a). The corresponding  moments of occlusion numbered 2, 3, and 4 in a) are indicated by the green and blue dashed frames as seen by pixel pairs 11, 12 and 13, 14, respectively. The red curve depicts the OHL pixel’s VOC response to red light exposure time. c) VOC response with time of our proof-of-concept 6 x 4 pixel OHL sensor detecting the letter E being temporarily occluded by a black rectangle (indicated by the dashed red frame) to the letter L. The inset depicts the percent changes in the OHL pixels’ VOC values upon this occlusion event (values highlighted by the blue frames are the pixels perceiving the occluded parts of the letter E). The yellow curves represent the not occluded pixels, whereas the blue curves reflect the letter E’s pixels masked by the black rectangle. The two red dashed vertical lines outline the time frame within which occlusion occurs. d) VOC response of OHL pixel with illumination time upon sudden increase in light intensity, starting from 4.9 Lux and e) 8.8 Lux. Respective tables (insets) depict percent changes in pixel VOC upon the corresponding light intensity growth. f) Absolute VOC values of the 4 x 6 OHL pixel sensor corresponding to Figure 3c. Blue frames mark those pixels affected by occlusion.