Patent US 8,041,536

An inclination calculation apparatus calculates an inclination of an input device operable in terms of a posture thereof. The input device includes an acceleration sensor and an imaging element. In one non-limiting example implementation, the inclination calculation apparatus computes first inclination information representing an inclination of the input device based upon a coordinate position of an imaging target in an acquired image obtained by the imaging element and an estimated coordinate position of a second imaging target not acquired by the imaging element. The inclination calculation apparatus also computes second inclination information representing an inclination of the input device solely from an acceleration detected by the acceleration sensor. The inclination calculation apparatus then calculates an inclination of the input device using the first inclination information and the second inclination information.