Fiberscopes arrived on the market about 35 years ago with the development of fiber optics, which are extremely thin strands of glass. Fiberscopes bundle together anywhere from 3,000 to perhaps 30,000 or more fiber strands. A fiberscope uses these fibers to transmit an image from the lens closest to the object being viewed through the bundle to a relay lens. The image captured by the lens can be viewed directly through an eyepiece, or the eyepiece can be attached to a camera that displays the image on a monitor.
One of the main advantages of fiberscopes over rigid borescopes is that fiberscopes are flexible and can be used for inspections in which straight-line access is not available. While some fiberscopes are also classified as “semi-rigid”, fiberscopes are also available with articulation. Articulation in a borescope means that the distal two inches or so of the scope’s insertion tube can be pointed in any direction, usually by means of control knobs located at the proximal end. In other words, the first few inches of the inspection tool that get inserted into the object are steerable or “controllable” by mechanisms on the unit that is closest to the inspection technician.
Articulating fiberscopes are the closest option to video borescopes in terms of quality and aptitude. However, there are some downsides to fiberscopes. Many of the low-cost fiberscopes, carried by auto parts stores, for example, use elastic fibers instead of glass fibers. The image quality for these scopes varies among different models depending on the number of fibers. For fiberscopes, transparency of the fibers directly relates to image quality. IE: Looking through a plastic drinking glass would be more difficult than looking through a glass one.
Another disadvantage of fiberscopes is that if any of the fiber strands break from rough articulation or simple overuse, the image will suffer from pixelation; the viewing screen and photos will display tiny black dots caused by the broken pixels. Once the strands start to break down, there is no repairing them and the entire unit will have to be replaced.