Two kinds of material for common use of precision polishing aspherical lens: N-BK7 and S-LAH64, which has higher transmittance in visible and near infrared wave band, and S-LAH64 has higher refractive index than N-BK7. therefore, it is usually used to make lenses with high numerical aperture and short focal length.
Compared with the ordinary spherical lens, the aspheric lens has larger numerical aperture and lower f/# , smaller spherical aberration, higher diffraction limit, better optical performance and fewer components, thus simplifies the system design.
These precision polished aspherical lenses are more suitable for small field of view applications such as fiber collimation, coupling and imaging. Compared with the molded aspherical focusing lens, the precision polishing has better surface quality and beam quality.
In order to ensure the best performance, the beam incident on the flat side of the lens is used for point source collimation, and the beam incident on the more curvature side is used for collimating beam focusing.