achromatic lens , cemented lens, Doublet.
It is used for optical imagine,with high quality
Key Specifications/Special Features:
* center thickness tolerance:±0.25
* Surface quality:60-40 stratch/dig
* surface precision:5/2~λ/2 at 546.1nm
* centration:3 arc min
An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths (typically red and blue) into focus in the same plane. An achromatic lens is usually composed of two individual lenses made from glasses with different amounts of dispersion. One element is a concave lens made of flint glass, the other element is made of crown glass.