Achieving a minimal latency within augmented reality (AR) systems is one of the most important factors to achieve a convincing visual impression. It is even more crucial for non-video augmentations such as dynamic projection mappings because, in that case, the superimposed imagery has to exactly match the dynamic real surface, which obviously cannot be directly influenced or delayed in its movement. In those cases, the inevitable latency is usually compensated for using prediction and extrapolation operations, which require accurate information about the occurring overall latency to exactly predict to the right time frame for the augmentation. Different strategies have been applied to accurately compute this latency. Since some of these AR systems operate within different spectral bands for input and output, it is not possible to apply latency measurement methods encoding time stamps directly into the presented output images as these might not be sensed by used input device. We present a generic latency measurement device which can be used to accurately measure the overall end-to-end latency of camera-based AR systems with an accuracy below one millisecond. It comprises a LED-based time stamp generator displaying the time as a gray code on spatially and spectrally multiple locations. It is controlled by a micro-controller and sensed by an external camera device observing the output display as well as the LED device at the same time.
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