In applications that require large acceptance angles, such as light gathering for illumination, spherical lenses are unsuitable due to spherical aberration, or the effect of refractive power of a spherical surface becoming greater with increasing aperture. Aspheric lenses maintain constant focal length or very high NA, avoiding the need for multiple elements to correct spherical aberration. This simplifies system design by reducing weight and component count. It also results in less transmission loss, and less ghosting due to having fewer surfaces. The primary drawback of aspheric lenses is off-axis performance is poor. This is not a problem for coupling to and from optical fibers or collimating light sources, but aspheric lenses are not usable over a wide field of view.

These Geltech lenses are made from Corning C0550 glass, which features low dispersion (Vd=50.40). Typical applications include fiber coupling, laser diodes, medical lasers, optical data storage, and barcode scanners. The lenses are available in both unmounted and mounted versions.

These mounted Geltech lenses feature a stainless steel 304 holder with a threaded exterior, M9x0.5 or M12x0.5. The numerical aperture is the same as the corresponding unmounted lens, but the working distance is slightly different. Aspherical Lens Adapters UPA1-AS9 and UPA1-AS12 are available to mount them into standard 1 in. optical mounts.