Patent ID: 8488413

Claim:
An indicated position detecting apparatus which detects an indicated position to a display screen, the apparatus comprising: a plurality of microphones arranged at an outer peripheral portion of the display screen to be apart from each other, and configured to constitute three sets of microphones and detect an indicator sound emitted from an arbitrary position above the display screen; a time difference acquisition unit configured to acquire each of arrival time differences of the indicator sound between the microphones in each of the three sets of microphones; and a positional information acquisition unit configured to acquire positional information indicating an emission position of the indicator sound in a three-dimensional space, as indicator position information indicating an indicated position to the display screen, based on the arrival time differences between the microphones in each of the sets acquired by the time difference acquisition unit; wherein: the positional information acquisition unit acquires positional information indicating a specific position corresponding to an intersection of a first hyperbola having the microphones in a first set as focal points, a second hyperbola having the microphones in a second set as focal points, and a third hyperbola having the microphones in a third set as focal points, respectively, specified by distance differences to the emission position of the indicator sound at the microphones in each of the sets represented by the arrival time differences, as the positional information indicating the emission position of the indicator sound in the three-dimensional space; and the positional information acquisition unit uses as a discriminant an equation in which a coordinate indicating a point in the three-dimensional space is used as an unknown number and a specific value is obtained by substituting a coordinate indicating the intersection of the first hyperbola, the second hyperbola, and the third hyperbola into the coordinate, and acquires a coordinate closest to the specific value as obtained by substituting a coordinate indicating each point in the three-dimensional space within a predetermined range above the display screen into the coordinate which is used as the unknown number in the discriminant, as the positional information indicating the emission position of the indicator sound in the three-dimensional space.