Despite advanced technology and the most sophisticated manufacturing techniques, lenses can still differ considerably in quality. Lens testing equipment is used for inspecting properties of lenses such as flatness, surface roughness, distortion, and depth of focus, which can give a direct and quantitative measure of image quality. Additionally, lens testing equipment allows users to identify the surface quality of a lens, such as if it has any defects like scratches or pits. This technology ensures that optical systems including cameras, contact lenses, video systems, fax machines, and copiers perform at a predetermined level of image integrity.