Systems and methods for determining a location of a stylus on a planar surface are provided. In one example, a system includes a first optical source, a second optical source, a stylus, and electrical circuitry. The optical sources are at source locations and configured to rotationally sweep optical beams along the planar surface. The optical beams include encoded data sequences that vary with time. The stylus contains at least one optical receiver and is configured to receive the optical beams. The stylus is also configured to detect the data sequences from the optical beams. The electrical circuitry is configured to determine angular relationships between the stylus and the source locations based on the detected encoded data sequences. The electrical circuitry is also configured to calculate coordinates of the stylus on the planar surface based on the angular relationships and the source locations.