This research designs and implements a marker recognition system that allows detection of tangible objects on a very large tabletop system. The design of the system is challenged by constraints including minimal distinguished size, non-linear imaging of the camera and areas of blind region caused by initiative IR illumination. After iterating through several designs, the study proposes the uMarker, an image-coding paper marker. Compared to the widely used reacTIVision, it is 75.7% smaller in size and 16.7% higher in coding capacity. The marker recognition system recognizes uMarker through image processing, which achieves good performances on capacity, recognition accuracy and efficiency. Furthermore, it can distinguish between fingers and uMarker and remove duplicated markers. In conclusion, uMarker extends the tabletop system with the ability to recognize tangible objects including information about location, direction and category.