Spherical Lenses

Achromats consist of two or more elements, usually of crown and flint glass, that have been corrected for chromatic aberration with respect to two selected wavelengths.  They are also known as achromatic lenses.  This area includes micro achromats as well.

Cylindrical lens have at least one surface that is formed in the shape of a cylinder. Cylindrical lenses are used to correct astigmatism in the eye, and, in rangefinders, to produce astigmatism, stretching a point of light into a line.  This area includes micro cylindrical lenses as well.

Fresnel lenses resemble a planoconvex or planoconcave lens that is cut into narrow rings and flattened. If the steps are narrow, the surface of each step is generally made 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.

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.  This area includes micro lenses.