Bk7&Fs Optical Achromatic Lens for Imaging

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.

The most common type of achromat is the achromatic doublet, which is composed of two individual lenses made from glasses with different amounts of dispersion. Typically, one element is a negative (concave) element made out of flint glass such as F2, which has relatively high dispersion, and the other is a positive (convex) element made of crown glass such as BK7, which has lower dispersion. The lens elements are mounted next to each other, often cemented together, and shaped so that the chromatic aberration of one is counterbalanced by that of the other.

In the most common type (shown), the positive power of the crown lens element is not quite equalled by the negative power of the flint lens element. Together they form a weak positive lens that will bring two different wavelengths of light to a common focus. Negative doublets, in which the negative-power element predominates, are also made.

Achromatic lenses are computer optimized to correct for on-axis spherical and chromatic aberrations. They consist of two optical components of different refractive index cemented together to form an achromatic doublet. These lenses are useful in axial imaging applications where a small spot size is required and for broadband imaging covering the visible spectrum. 

They are uncoated but many types of anti-reflection coating may be applied on request. Please contact the Star Optic's sales team for more coating information.

An achromatic doublet brings red and blue light to the same 

focus, and is the earliest example of an achromatic lens.

Specifications: 

Standard products: