An aspheric lens or asphere is a lens whose surface profiles are not portions of a sphere or cylinder. It has a radius of curvature that varies from the center to the edge of the lens.
Compared to a simple lens, the asphere's more complex surface profile can reduce or eliminate spherical aberration and also reduce other optical aberrations such as astigmatism. A single aspheric lens can often replace a much more complex multi-lens system. The resulting device is smaller and lighter, and sometimes cheaper than the multi-lens design.
Aspheric elements are used in the design of multi-element wide-angle and fast normal lenses to reduce aberrations. They are also used in combination with reflective elements (catadioptric systems) such as the aspherical Schmidt corrector plate used in the Schmidt cameras and the Schmidt-Cassegrain telescopes. Small molded aspheres are often used for collimating diode lasers.
| ATTRIBUTE | COMMERCIAL | PRECISION | HIGH PRECISION |
| DIAMETER TOLERANCE | ±0.05 | ±0.015 | ±0.01 |
| TC TOLERANCE | ±0.05 | ±0.02 | ±0.01 |
| CENTRATION | 7um | 5um | 2um |
| FLATNESS(PV) D<Φ3 | 1um | 0.5um | 0.3um |
| FLATNESS(PV) D<Φ6 | 1.5um | 1um | 0.5um |
| FLATNESS(PV) D<Φ12 | 2um | 1.2um | 0.65um |
| FLATNESS(PV) D<Φ20 | 3um | 1.5um | 0.8um |
| SURFACE QUALITY | 80/50 | 60/40 | 40/20 |
| DIMENSION | Φ1.0～Φ50 | Φ1.0～Φ50 | Φ1.0～Φ50 |
| MATERIAL | From CDGM,SUMITA, OHARA, HOYA, etc. |
Figure: Spherical aberration in a Spherical Lens (left) vs an Aspheric Lens (right)
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