Pressing makes precision aspheres faster and cheaper
Image defects such as chromatic aberration, coma, astigmatism, barrel distortion, and pincushion distortion are unavoidable consequences of spherical surfaces. In the past, designers have used a series of spherical lenses with aberrations that canceled each other. All these defects, except chromatic aberration, could be avoided by using nonspherical surfaces.
Advances in precision molding make aspheric lenses practical and affordable.
Amorphous silicon arrays promise large-area imagers