Dart game apparatus

A dart game apparatus that provides a dart game in which one player successively throws n number of (n=3 or 4) darts at a dart board, the apparatus comprising:

• light sources that are disposed around the dart board and emit lights along a board face of the dart board, wherein the dart board has a board thickness in a board thickness direction, and wherein the board thickness direction is perpendicular to the board face;
• a plurality of photo-sensors that are disposed around the dart board at approximately the same height from the dart board in the board thickness direction, and detect brightness of lights emitted from the light sources;
• a processor that calculates a hit position of a dart on the dart board based on the brightness of the lights detected by the plurality of photo-sensors;
• and
• a retro-reflector disposed around the dart board, wherein the retro-reflector includes two reflectors, wherein the reflectors are parallel to each other, wherein the reflectors are spaced apart from each other in the board thickness direction, and wherein the reflectors extend in a circumferential direction of the dart board, and
• wherein a number of photo-sensors is n×2,
• wherein the photo-sensors detect the brightness of the lights along a plurality of optical axes which pass from the dart board at different heights in the board thickness direction, and the processor calculates the inclination of the dart with respect to the dart board based on the brightness of the lights along the plurality of optical axes respectively, and calculates the hit position of the dart based on the calculated inclination, and
• wherein in the case where a new dart hits the dart board successively from a previous dart, and a photo-sensor detects a plurality of the brightnesses of lights based on the previous dart and the new dart in one optical axis, the processor specifies a brightness of a current light of the previous dart after the new dart hits the dart board from the plurality of the brightnesses of lights, based on a past brightness of the previous dart before the new dart hits the dart board, and calculates an inclination of the new dart based on a brightness of light other than the specified brightness of the current light of the previous dart.