läätse

Läätse is an optical element used to bend light and form images. In standard Estonian, the common term is lääts, and läätse is a historical or dialectal variant sometimes found in texts referring to lenses. A lens is typically made of transparent material such as glass or plastic and has one or more curved surfaces that refract light according to Snell's law.

Most lenses are designed to converge (positive focal length) or diverge (negative focal length) light. Common shapes include bi-convex, bi-concave, plano-convex, and plano-concave lenses. Planar-convex lenses have one flat surface and one convex surface; bi-convex lenses are curved on both sides; concave lenses diverge light. Lenses are characterized by focal length, diameter, thickness, and the refractive index of the material.

Manufacture involves selecting material, shaping the surfaces to precise curves, and finishing with polishing and coatings to reduce reflections. Anti-reflective coatings minimize glare, and polarized or tinted coatings are used for specialized applications.

Applications include eyeglasses, contact lenses, cameras, microscopes, telescopes, projectors, and various scientific instruments. In ophthalmology, lenses correct refractive errors by altering the eye’s focal power, improving vision clarity for people with short-sightedness, far-sightedness, or astigmatism.

See also: optics, refraction, lens design, optical coatings.