Borescope

An instrument used to examine the inside of a structure through a very small hole. The inside of a turbine engine and the inside of the cylinder of a reciprocating engine, for example, can be examined by inserting the probe of the borescope through a small inspection hole or through a spark plug hole. A borescope furnishes its own light, and some borescopes have different ranges of magnification. Some borescopes are fitted to a camera to photograph the inside of the structure. A modern trend in borescopes is to place a video pickup on the borescope tube and display the results on a small television screen.