Abstract: Disclosed is a method and system for making payment with discounted prices by using temporary card numbers.

Abstract: The low power image sensor includes: an image sensing unit which senses light from an object, converts the light into an electric signal, and outputs the electric signal; a comparing unit which receives an electric signal from the image sensor, compares a voltage level of the electric signal with a reference voltage, and outputs an image signal as a 1 bit signal per pixel; and an effective image adjuster which compares bit value distribution of an image signal output from the comperator with a preset effective range, and adjusts the effective image to output an effective image. Further, an optical pointing device includes: an image sensor which senses light from an object and outputs an image signal; and a motion computing unit which receives the image signal and compares before and after images to calculate a motion vector.