Borescopes have many uses that range from looking at the inside surface of a rifle to photographing the private lives of insects in their homes. The basic components of a borescope are a light source, fiber optics for introducing light and displaying images for your eye or camera, and optics for the transmittance of the image from the remote end to the outer end of the scope. High power LED light sources work well as a light source. The remote end optics is available from the manufacturer or you can possibly use the view piece of an old telescope.
Acquire the basic fiber optic bundle you can use to transmit the light and retrieve the image. Many sources have fiber optic bundles available for this purpose. If you can find an old endoscope or bronchia scope, you can salvage the fiber end section of the scope to serve your purposes. Most of these devices are flexible and can be rotated and bent as required to view the target.
Setup a basic light source using a high-intensity flashlight beam or high output LED to deliver light through one of the tails of the double end of a bifurcated fiber optic cable. Many standard circuits are available to drive the high output LED. If necessary, mount a mini flashlight at the end of the cable tail. Activate the light source by turning the flashlight on or off.
Attach an optical eyepiece to the other tail of the bifurcated fiber optic cable. You can use the optical eyepiece from an old endoscope or bronchia scope to allow viewing of the region at the other end of the borescope. An alternative eyepiece for viewing is the view piece of an old telescope. The optics package will display the image captured from the other end of the fiber optic cable. To use the borescope for photography, you will need to provide an attachment for your camera. Most endoscopes and bronchia scopes accept a video coupler using a C-mount to adapt the eyepiece to a camera.