The use of aspheres reduces errors in imaging to a minimum. The correction of these errors would otherwise require the use of several lenses. As a rule of thumb, the following applies: If the ratio of the focal distance to the diameter aperture (f/d) is < 2 or a numerical aperture of > 0.2 is required, the use of an aspheric lens makes sense.
Typical applications for these components include the collimation of laser diodes and the focussing of a collimated beam into an optical fibre. Until recently, inexpensive aspheric plastic lenses were the lens of choice.
Available immediately is a range of aspheric glass lenses, for use in high power lasers, offer extremely high quality, and even available in large diameters.
