Borescopes are instruments used to view or inspect inaccessible spaces found in mechanical constructs, assemblies, automotive engines, turbines, firearms, and buildings. All borescopes generally have three basic components regardless of type or purpose. These are the objective lens, the relay optics stored in either a flexible or rigid tube, or the eye piece.

The objective lens is at the end of the borescope that captures or records and illuminates the object being inspected. The relay connects the objective lens to the eye piece, which magnifies the image for the user.There are three general types of borescopes. These are flexible borescopes, video borescopes, and rigid borescopes.

Flexible borescopes are also known as fiberscopes because this type uses flexible fiber optic tubes to capture images, making them more expensive compared to the other types of borescopes. Flexible borescopes are often used to view objects or spaces found in tight bends or corners typically found in air inlets, turbines, and mechanical engines. The images produced by flexible borescopes are less clear compared to the images produced by the other types of borescopes since the images are prone to pixilation, depending on the number of fiber optics found inside the borescope. The more optical fibers used, the better the quality of the image, which are often found on larger diameter, and more expensive, flexible borescopes.

Video borescopes are similar to flexible borescopes but instead use a small camera at the end of the flexible tube. This type of borescope can use the camera to either capture still images or make a recording of the space being inspected. Most models allow the user to control and move the camera, as well as change how the images are viewed. This added flexibility and features make video borescopes more versatile compared to the other types of borescopes. Furthermore, video borescopes can capture clearer still images compared to flexible borescopes depending on the specifications of the camera.

Finally, rigid borescopes use a rigid tube to house the relay optics. As a result, this type of borescope has the most limited application since it can only view objects or spaces in a straight line. Because of this limitation, rigid borescopes are best suited to use in firearms and in tube or cylindrical assemblies such as automotive cylinders and turbines. Rigid borescopes produce the best image compared to other types of borescopes.