Llentes

Llentes are optical elements designed to transmit and shape light. They are used in devices that form images or correct vision, including eyeglasses, contact lenses, cameras, microscopes, and projectors. The term encompasses a broad range of products, from corrective lenses to precision components in imaging systems.

In eyewear, llentes can be corrective (single-vision, bifocal, or progressive), sun or tinted, and may include UV protection, anti-reflective coatings, or photochromic effects. Contact lenses are thin lenses worn on the cornea, made from hydrogel or silicone hydrogel polymers, with various wear schedules. In cameras and projectors, as well as scientific instruments, lenses are described by focal length, aperture, coatings and optical design to control magnification and field of view. Lens shapes include convex (converging) and concave (diverging).

Materials range from glass to plastics such as CR-39, polycarbonate, and high-index polymers. Common coatings improve transmission and durability, including anti-reflective, scratch resistance, UV protection, and hydrophobic layers. Some photographic lenses use specialized coatings, while high-end eyeglass lenses may use aspheric designs to correct aberrations.

Manufacture involves grinding, polishing, surfacing and coating; plastic lenses are often molded or cast. Care varies by type: eyeglass lenses are cleaned with lint-free cloths and appropriate cleaners; contact lenses require hygienic handling and regular replacement; camera lenses require dust-free storage and occasional calibration.

Historically, lenses have evolved from simple glass pieces to complex multi-element systems. Eyeglasses emerged in the 13th century in Europe, and modern coatings and high-index materials appeared in the 20th century. International standards exist to regulate lens quality, safety, and performance, such as ISO optical lens standards and ANSI guidelines for eyewear.