Sometimes called the fiberscope, the endoscope is an optical instrument that allows doctors to view the inner workings of the human body without having to perform surgery. The endoscope is a flexible narrow tube containing several bundles of hair-thin glass fibers that are covered with a reflective coating. A highly intense light source, usually a halogen lamp, is used to transmit light along one bundle of fibers toward the target area inside the body. Another bundle of fibers carries an image of the target area back up the tube where it is viewed through an eyepiece.

Endoscopes are primarily used in the health care field, but they may also be used for industrial purposes examining such inaccessible places as the inside of fuel tanks and nuclear reactors. Crude versions of the endoscope were used as early as the nineteenth century and included long, rigid tubes illuminated by candles...