Patent ID: 7468522

Claim:
A system for locating a position of a rod wherein the rod has a length defined between a first end and a second end and further wherein the rod has an exterior surface connecting the first end and the second end, the system comprising: exterior walls defining an interior wherein the exterior walls have a length defined between a first end and a second end wherein the rod is insertable into the interior; an aperture formed within the exterior walls wherein the aperture is located between the first end and the second end of the exterior walls wherein light projects through the aperture into the interior of the exterior walls wherein the light has a color; a mark displayed on the exterior surface of the rod between the first end and the second end wherein a color of the mark corresponds to the color of the light wherein the mark is substantially co-planar with the rod so that the mark does not project from the rod wherein the mark has a color; and a light detector connected to the exterior walls wherein the light detector is adjacent to the aperture within the exterior walls wherein the light detector detects an intensity of light within the interior of the exterior walls wherein the intensity of the light corresponds to an amount of light that is absorbed by the mark wherein the intensity of light detected by the light detector corresponds to a position of the mark within the interior of the exterior walls.