Patent ID: 7520062

Claim:
An optical device comprising: a frame; a first light generator; a first lens disposed in a first light path generated by the first light generator and defining a Cartesian (x,y,z) coordinate system, the first lens having first and second surfaces with x,y coordinates that are independent of z over at least a portion of the z direction length of the first lens, the second surface defining a multiple-radius curve in an x,y plane, the lens converting light generated by the first light generator into a first light plane that includes a light arc; and a self-leveling mechanism mounted to the frame, the self-leveling mechanism tending to orient the first light plane into a predetermined angle relative to horizontal, wherein the first lens is shaped and oriented relative to the first light path so as to direct more intense light toward distal ends of the arc than at a central portion of the arc, and wherein the first light generator and first lens are constructed and positioned to transmit light generated by the first light generator through the first and second surfaces to create the first light plane.