Latency of closed-loop control schemes
For effective closed-loop control, the latency between the imaging of the sample and resulting light projection should be minimised. For the DOME, latency can be described as the time period between subsequent camera frames being obtained, since a new frame is captured only after the imaging module has sent data to the projection module and received confirmation of its receipt. The system latency will vary between applications and depends on camera settings, and the amount of image processing required per frame. To characterise the baseline latency of the DOME, an experiment was run with no image processing where the projector was switched between an on (white) and off (black) state after every camera frame received. We found that the primary source of latency was the time needed by the camera to capture an image, which is also dependent on the capture resolution. The algorithm was therefore run over a range of resolution settings. Each time measurement was taken as a mean average over 100 frames, running at a shutter speed of 100 milliseconds. Measurements were taken at 63 different resolution settings, starting at 640 × 480 pixels and increasing in increments of 32 × 32 pixels until maximum camera resolution was reached at 2646 × 2464 pixels.