Abstract: An initial location of a light pen (150) placed on the surface of an ac plasma panel (100) is determined by scanning the panel with a two-step finder mode. In the first step, the display sites of every seventh row of display sites of the panel are caused to flash in groups of sixteen until the pen signals that it has detected a flash. The sites in a 60-by-60 site region (306) of the panel are then caused to flash individually to determine the precise pen location (302). A second pen location (312) is determined by scanning the sites of a 32-by-32 scanning patch (311) centered around the initial pen location. Subsequent pen locations are then predicted based on the most recent and second most recent pen locations. Each predicted location (317) is used to determine where a subsequent 32-by-32 scanning patch (316) is to be positioned. The direction in which the pen is moving determines the order in which the sites of each patch are scanned.