Borescopes are used as a form of Non-Destructive Testing(NDT). They are built to visually inspect areas that would otherwise need to be dissasembled before proper inspection. In order to visually inspect, borescopes commonly use a relay lens system, a rod lens system, a fiber optic image guide, or a CCD or CMOS Camera Chip. The most common borescopes have two types of probes: Rigid and Flexible. Rigid borescopes are made of a stainless steel probe and do not bend or fold in the probe because they use lens, or fibers to relay an optical view to the camera or eye piece. Flexible borescopes typically include a metal weave that protects the insides of the probe that contain either fiber optics, or electrical cable to relay the information; additionally, if it has articulation, the articulation wires will also be fed through the length of the probe to where the articulation controls are. The articulation wires are very thin metal wires similar to piano wires, that push and pull in order to move the head of the scope one direction or another. Borescopes also need a light source for many applications that will allow the view from the probe to be well lit enough to see. Rigid and fiber scopes necessitate a light source to be shot through the body of the probe through fiber optics; however, many of the flexible video probes do not use fiber optics, instead they use LED's that are electronically installed on the tip of the probe, next to the lens.
It is important to understand what kind of borescope you will need. First, figure out what kind of borescope you need: a rigid, or a flexible probe.