A borescope is an optical device consisting of a rigid or flexible tube with an eyepiece on one end, an objective lens on the other linked together by a relay optical system in between. The optical system in some instances is surrounded by optical fibers used for illumination of the remote object. An internal image of the illuminated object is formed by the objective lens and magnified by the eyepiece which presents it to the viewer's eye.

Borescopes are used for visual inspection work where the area to be inspected is inaccessible by other means. Borescopes are mostly used in non destructive testing techniques for recognizing defects or imperfections.

Borescopes are commonly used in the visual inspection of industrial gas turbines, steam turbines Gas and steam turbines require particular attention because of safety and maintenance requirements. Borescope inspection of engines can be used to prevent unnecessary maintenance, which can become extremely costly for large turbines. They are also used in manufacturing of machined or cast parts to inspect critical interior surfaces for burrs, surface finish or complete through-holes.

A video borescope or "inspection camera" is similar to the flexible borescope but uses a miniature video camera at the end of the flexible tube. The end of the insertion tube includes a light which makes it possible to capture video or still images deep within equipment, engines and other dark spaces. As a tool for remote visual inspection the ability to capture video or still images for later inspection