Optical Lenses

Optical lenses are transparent components made from optical-quality materials and curved to converge or diverge transmitted rays from an object. These rays then form a real or virtual image of the object. There are many types of optical lenses. Achromats or achromatic lenses consist of two or more elements, usually of crown and flint glass, which have been corrected for chromatic aberration with respect to two selected wavelengths. Aspheric lenses compensate for spherical aberrations and are used primarily for their light-gathering ability. Ball lenses provide short focal lengths for use with collimated light and fiber coupling applications. Cylindrical lenses have at least one cylindrical surface and are used to correct or produce astigmatisms. Fresnel lenses resemble a planoconvex or planoconcave lens cut into narrow rings and flattened. If the steps are narrow, the surface of each step is generally conical and not spherical. Gradient index (GRIN) lenses focus light through a precisely controlled radial variation of the lens material's index of refraction from the optical axis to the edge of the lens. Meniscus lenses can increase the numerical aperture of a positive lens assembly without an undue increase in the number of aberrations. Spherical lenses or singlets are transparent optical components that consist of one or more pieces of curved optical glass.