Patent attributes
When a light beam shot from a light gun hits a target plate mounted on a target device, the light beam is detected by a beam detected position detecting unit, which generates a current based on the shot impact position of the light beam on the target plate. An extraneous light detecting unit generates a current based on extraneous light applied to the target device. The current generated by the beam detected position detecting unit or a voltage based on the current, and the current generated by the extraneous light detecting unit or a voltage based on the current are supplied to a subtractor, which subtracts the current generated by the extraneous light detecting unit or the voltage based on the current from the current generated by the beam detected position detecting unit or the voltage based on the current, and outputs a differential current or voltage value. Thus, an extraneous light component is removed from the current generated by the beam detected position detecting unit. Thereafter, a position calculating unit recognizes the light beam shot from the light gun and detects the shot impact position of the light beam on the target plate based on the differential current or voltage value.
