A lens manipulates light through refraction, either concentrating or dispersing it. Unlike a prism that refracts without focusing, a lens concentrates light to create an image. Typically crafted from glass or plastic, lenses can also be fashioned from liquids, mimicking the focusing mechanism of the human eye. Glass lenses are meticulously shaped through grinding and polishing. In contrast, plastic lenses are formed through molding.
Simple lenses are categorized into eight types based on the curvature of their two optical surfaces.