US Patent 11405531 Data processing

Data processing apparatus includes a camera to capture successive images according to an image capture period; an optically detectable indicator having multiple optically detectable states and configured to transition between the multiple optically detectable states according to a transition pattern having interspersed periods in the multiple optically detectable states; the transition pattern including a reference period and two or more second periods which are shorter than the image capture period and which are separated by a separation period different to the image capture period; and a processor to detect timing information from images captured by the camera of the optically detectable indicator.