The use of higher-order surfaces in optical systems to enhance performance has been discussed for several decades, with parabolic mirrors being used for centuries. The craftsmanship of making spherical lenses has a long tradition, leading to innovations like stepper objectives in microlithography for manufacturing modern electronic devices. In contrast, producing aspheres in large quantities and with sufficient quality for optical systems began about 25 years ago. Around the same time, the concept of freeform surfaces emerged, with significant advancements in the last decade.

Aspheric surfaces offer several advantages, including smaller packaging, larger fields of view (FOV), and increased numerical aperture (NA).

Today, aspheres can be manufactured with the same precision as spherical surfaces, achieving surface roughness below 1nm RMS and form deviations well under 10nm RMS. However, freeform surfaces present additional challenges due to their lack of symmetry, requiring specialized manufacturing techniques and precise metrology equipment to measure them at the same level as aspheres. The main advantage of freeform surfaces lies in significant space savings, as they can compensate for non-symmetric aberrations, allowing for more compact optical designs.

Many examples of realised optical systems will show the current state of the art and the creative solutions that are now possible with aspheres and free-form optical surfaces.