What is a Borescope?

A borescope is an optical tool used to view areas that are not visible to the naked eye. A borescope is inserted into the item being evaluated without destroying the item of interest. It is an optical instrument designed to give a visual inspection of narrow areas which are inaccessible, difficult-to-reach cavities, consisting of a rigid or flexible tube with an eyepiece or display on one end, an objective lens or camera on the other, linked together by an optical or electrical system in between. The optical system in some instances is accompanied by fiberoptic illumination to enhance brightness and contrast. Borescopes are mostly used in non-destructive 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.

It is an instrument used to inspect the inside of a structure through a small hole. The first modern borescope was invented by the American physicists Narinder Kapany and Broan O’Brien in 1960. Borescopes and inspection cameras can come in many forms. Some have a rigid arm with a fixed camera, a flexible arm, a soft bendy wire-like extension, or a mixture. Borescope accessories can extend the possibilities still further like tiny mirrors can re-direct the view sideways, while hooks and magnets can help retrieve lost items from hard-to-reach places. Rigid or flexible borescopes may be externally linked to a photography or videography device. For medical use, similar instruments are called endoscopes.

Flexible borescopes

The traditional 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 that are around a bend, such as a combustion chamber or burner can, to view the condition of the compressed air inlets, turbine blades, and seals without disassembling the engine. Image quality varies widely among different models of flexible borescopes depending on the number of fibers and construction used in the fiber image guide. Some high-end borescopes offer a visual grid on image captures to assist in evaluating the size of any area with a problem. For flexible borescopes, articulation mechanism components, range of articulation, the field of view, and angles of view of the objective lens are also important. The fiber content in the flexible relay is also critical to provide the highest possible resolution to the viewer. The minimal quantity is 10,000 pixels while the best images are obtained with higher numbers of fibers in the 15,000 to 22,000 range for the larger diameter borescopes. The ability to control the light at the end of the insertion tube allows the borescope user to make adjustments that can greatly improve the clarity of video or still images.

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 that makes it possible to capture video or still images deep within the equipment, engines, and other dark spaces. As a tool for remote visual inspection, the ability to capture video or still images for later inspection is a huge benefit. A display at the other end shows the camera view, and in some models, the viewing position can be changed via a joystick or similar control. Because a complex fiber optic waveguide in a traditional borescope is replaced with an inexpensive electrical cable, video borescopes can be much less costly and potentially have better resolution depending on the specifications of the camera.

Rigid borescopes

Rigid borescopes are similar to fiberscopes but generally provide a superior image at a lower cost compared to a flexible borescope. Rigid borescopes have the limitation that access to what is to be viewed must be in a straight line. Rigid borescopes are therefore better suited to certain tasks such as inspecting automotive cylinders, fuel injectors and hydraulic manifold bodies, and gunsmithing. The above image shows a high-resolution image transmission in a durable stainless steel insertion tube with light guide fibers for bright illumination. A wide selection is available to suit any requirements.

Borescopes uses

Borescopes are used to non-destructively inspect industrial systems and equipment for condition, manufactured parts for quality and security, and law enforcement for contraband, intelligence, and safety. Common Inspections Include internal viewing of Turbine Engines, Internal Combustion Engines, Pipes, Heat exchanger tubes, Gearboxes, Welds, Foreign Object Retrieval, Cast Parts, Manufactured or machined parts

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.

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 the 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 of large guns for defects.