Franklin also invented such conveniences as bifocal eyeglasses. The company sells multiple types of lenses, including bifocal, progressive, and Transitions lenses. For example, the first bifocal lenses came from Rodenstock as did UV-absorbing lenses. Bifocal lenses are also available for this application. He devised methods and processes to create bifocal contact lenses for optimum performance. In particular he was interested in the bifocal contact lenses. Bifocal lenses advanced little in the first half of the 19th century. A bifocal lens could be considered a simple example. During that time he invented the cemented bifocal lens. Bifocal lens has two or more, or a graduated, focal lengths ground into the lens. The diving beetle has a unique bifocal lens which is asymmetric. This inlay works on a similar principle to bifocal glasses. Younger Optics, Torrance's 10th-largest employer, created the first seamless or "invisible" bifocal. Benjamin Franklin in the 1780s developed the bifocal. The bifocal design provides two images to the retina simultaneously.