Achromatic lenses are normally made of BK7, fused silica and CaF2. Special focusing systems can be designed by Photonchinaâ??s engineer team. Sizes from smallest diameter of 3mm to biggest of over 100mm are all available. Normal Achromatic Lens Super Small Achromatic Lens Super small Achromatic Lenses for your specific application provide excellent wavefront quality, super small spot size and improved modulation transfer function (MTF). Feature Small diameter size up to 3mm Short focal length, such as 5mm Strict quality control, excellent quality AR-coating, mounts services