an achromats. Different lens materials may also be used to minimise chromatic aberration, such as specialised coatings or lenses made from the crystal fluorite. This naturally occurring substance has the highest known Abbe number, indicating that the material has low dispersion.Other types of aberration[සංස්කරණය]Other kinds of aberration include field curvature, barrel  and pincushion distortion, and astigmatism.Aperture diffraction[සංස්කරණය]Even if a lens is designed to minimize or eliminate the aberrations described above, the image quality is still limited by the diffraction of light passing through the lens' finite aperture. A diffraction-limited lens is one in which aberrations have been reduced to the point where the image quality is primarily limited by diffraction under the design conditions.සංයුක්ත කාච[සංස්කරණය]සරල කාච භාවිත කරන විට ඉහත සාකච්ඡා  කළ පරිදි ආලෝකය අප්‍රේරණයකට ලක්වේ. බොහෝ අවස්ථාවලදී මෙම අප්‍රේරණයේ අවම කරගැනීම සඳහා එකිනෙකට අනුපූරක අප්‍රේරණ සහිත සරල කාච ස