According to ISO 10110, there are protective and functional coatings. Protective coatings are used to ensure safety of optical surfaces such as use in rough environments. Functional coatings provide necessary refractive or reflective coefficient. An optical engineer defines optical coating requirements not only for efficiency but also based on their assessment of the influence of light reflected from the lens surface onto an image or sensor. Reflected or scattered light can destroy an image quality or signal to noise ratios.