A transparent optical component consisting of one or more pieces of optical glass with curved surfaces (usually spherical) that they serve to converge or diverge the transmitted rays from an object, thus forming a real or virtual image of that object. JH Optek provides these lenses with the material of BK7, fused silica, sapphire, CaF 2 and MgF 2 as standard.Other materials lenses are available upon requirement.