The field of fiber optics depends upon the total internal reflection of light rays traveling through tiny optical fibers. The fibers are so small that once the light is introduced into the fiber with an angle within the confines of the numerical aperture of the fiber, it will continue to reflect almost losslessly off the walls of the fiber and thus can travel long distances in the fiber. Bundles of such fibers can accomplish imaging of otherwise inaccessible areas.
Fiber Optic Imaging
Fiber optic imaging uses the fact that the light striking the end of an individual fiber will be transmitted to the other end of that fiber. Each fiber acts as a light pipe, transmitting the light from that part of the image along the fiber. If the arrangement of the fibers in the bundle is kept constant then the transmitted light forms a mosaic image of the light which struck the end of the bundle.