US Patent 8122798 Power cutting tool with proximity sensing system

A power cutting tool includes a cutting surface, a conductive structure, and first electrode matrix comprising an array of electrical conductors. A moveable blade used to cut an object is located on the cutting surface. When at least one electrical conductor of the first electrode matrix is energized relative to the conductive structure, an electric field extends between the at least one electrical conductor and the conductive matrix to detect the presence of an object in proximity to the electric field.