Borescope is a tool that works like a telescope, microscope or camera. This allows people to explore areas that are too small, too far or out of reach. It has a lens on the top that attaches to the insertion tube which can be rigid or flexible.
When the borescope insertion tube is directed through a hole, it takes a lens and a light source for what needs to be checked. At the end of the tube are two lenses, light source, nozzles and other openings.