Biconic lenses have two different radii on one surface. It is possible to make a biconic lens with spherical curves or aspheric curves, depending on the application and need to eliminate aberrations. Biconic lenses are used to produce an elliptically shaped focus or line focus. These lenses are also used in anamorphic beam expanders to reduce astigmatism in the laser beam. Many waveguide-type lasers produce astigmatic beams. Since most laser applications require symmetric Gaussian beams, astigmatic beams must be corrected.
The usual type of optic used in anamorphic beam expanders and elliptical focus lenses is the cylinder lens. For the beam expander application and some focusing applications, it is necessary to use two cylinders, resulting in difficult alignment procedures. The biconic lens can reduce the number of elements used in this application and, more importantly, reduce alignment headaches.