A lens with a focal length close to the human viewing angle is called a “standard lens,” while a lens with a focal length closer than that of a standard lens is called a “wide-angle lens”. Wide-angle lenses are used in all kinds of optical systems, including cameras, because they can capture a wider range of images than standard lenses.
On the other hand, one of the requirements for wide-angle lenses is “low distortion”. Distortion and volume deformation are typical distortions in wide-angle lenses. This is a result of wide-angle lenses being convex lenses. When you use a wide-angle lens to obtain information over a wide area, distortion is an issue that is bound to occur, no matter how small or large the level.
Here are some tips on how to eliminate this distortion.