An image capturing apparatus comprises a solid image pickup element having pixels for outputting signals, which are logarithmically varied with respect to an incident light intensity, and a voltage controller. The magnetic plate has at least one pair of N and S magnetic poles. The second LA is characterized by a LA center and a LA size, both determined by optimizing them in a sense that a mean total location-management cost is minimized without restricting the LA center to be fixed at the initial position. The mobile device then captures the representation of the key from the local device, for example using an image capture device or audio capture device, and extracts the key by decoding the representation of the key. The peak-to-peak ripple in the charge pump output is thereby reduced to about 400 mV or less.