Borescope

A borescope (occasionally called a boroscope, though this spelling is nonstandard) 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.

Rigid or flexible borescopes may be fitted with an imaging or video device. For medical use, similar instruments are called endoscopes.

Borescopes are used for visual inspection work where the area to be inspected is inaccessible by other means, or where accessibility may require destructive, time consuming and/or expensive dismounting activities. Similar devices for use inside the human body are referred to as endoscopes. Borescopes are mostly used in nondestructive testing techniques for recognizing defects or imperfections.

Borescopes are commonly used in the visual inspection of aircraft engines, aeroderivative industrial gas turbines, steam turbines, diesel engines, and automotive and truck engines. 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. Other common uses include forensic applications in law enforcement and building inspection, and in gunsmithing for inspecting the interior bore of a firearm. In World War II, primitive rigid borescopes were used to examine the interior bores (hence "bore" scope) of large guns for defects.

A flexible borescope includes a bundle of optical fibers which divide the image into pixels. It is also known as a fiberscope and can be used to access cavities which are around a bend, such as a combustion chamber or "burner can", in order to view the condition of the compressed air inlets, turbine blades and seals without disassembling the engine.

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