Achromatic lens are basically two or more lens fixed in relation to one another by either mounting or cementing. Manufactured from crown glass and flint glass, other materials like fused silica and bk7 positive glass may be used. Achromatic lenses function effectively within infrared, visible, or ultraviolet wavelength ranges, optimized for three wavelengths 486.1, 587.6 and 656.3nm. Chromatic lens are often treated with anti reflective coating to reduce increased transmission of light at the lens-air interface. This coating is often made of a multi layer of broadband dielectric material. Achromatic lens are widely used today in achromatic telescope, microscopes, and photographic lens. Doublets and triplets are two types of achromatic lens used in ccd imaging lenses for near infrared , focusing and expanding of nir lasers and focussing and collimating lenses for fiber optics and led's.
