A camera is provided that includes a dust-proofing member that has a substantially circular or polygonal plate-shape and that includes a transparent portion at an area having at least a predetermined length in a radial direction from the center thereof, and that is opposed to the front of an optical device at a predetermined interval. The method includes measuring coordinates andor speed in a basic coordinate system and an inertial coordinate system at moments of time. The device is equipped with multiple switching mechanisms. The current subtractor subtracts the first current from the second current to output a constant current regardless of the resistance variation of the first to third resistance elements. As a result, a decrease in fuel efficiency of a vehicle in which a continuously variable transmission is mounted, as well as a reduction in the durability of a belt of this continuously variable transmission, can be reduced. In addition, all communication and interaction between process components takes place through the respective interfaces of the process components.