Boroscope

A Borescope is an optical instrument designed to assist visual inspection of narrow, difficult-to-reach cavities. 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 target area is inaccessible by other means, or where accessibility may require destructive, time consuming and/or expensive dismounting activities. Borescopes are mostly used in nondestructive testing techniques for recognizing defects or imperfections.