An achromatic lens, also known as a doublet lens, is a composite lens cemented from two types of optical glass with different dispersion properties (crown glass + flint glass). Its core function is to focus light rays of two key wavelengths, red and blue, onto the same plane, significantly reducing chromatic aberration while optimizing spherical aberration and coma. Compared with single lenses, it can produce smaller light spots and sharper imaging, making it a core component of precision optical systems.
