Patent ID: 8619268

Claim:
An apparatus for detecting a change in thickness of an opaque strip of material, the strip of material having a first face and a second face opposite of the first face, the apparatus comprising: a light source configured for outputting light toward the first and second face of the strip of material; a light detector configured for receiving at least a portion of light from the light source reflected off of the first and second face of the strip of material; at least one sending cable having at least one first end and at least one second end and being configured and positioned for receiving light from the light source and transmitting a first portion of light toward the first face of the strip of material and a second portion of light toward the second face of the strip of material; and at least one receiving cable having at least one first end and at least one second end and being configured and positioned for transmitting the portion of light from the light source reflected off of the first and second faces of the strip of material to the light detector; a housing configured for fixing portions of the sending and receiving cables in said positions and for limiting movement of the strip of material toward and away from the sending and receiving cables in the direction of the thickness of the strip of material such that a total amount of light reflected off of the strip of material into the receiving cable and received by the light detector is inversely proportional to the thickness of the strip of material; and an indicator communicably coupled with the light detector and configured for indicating when a change in thickness of the material is detected based on the total amount of light received by the light detector, wherein the sending and receiving cables further comprise a plurality of optical fibers, wherein ends of at least a portion of optical fibers of the sending cable are fixed by the housing in spaced, side-by-side relationship and alternating succession with ends of at least a portion of optical fibers of the receiving cable, wherein the optical fibers of the sending cables are all configured to receive light from the light source and the optical fibers of the receiving cables are all configured to send light to the light detector, wherein the optical fibers of the sending cable are divided into a first subset and a second subset and the optical fibers of the receiving cable are divided into a first subset and a second subset, wherein the optical fibers of the first subset of the sending cable are arranged in alternating succession with the optical fibers of the first subset of the receiving cable and are configured to direct light onto the first face of the strip of material, wherein the optical fibers of the second subset of the sending cable are arranged in alternating succession with the optical fibers of the second subset of the receiving cable and are configured to direct light onto the second face of the strip of material.