Lanthanum Crown Glass
Lanthanum Crown Glass is referred to as LaK glass or lanthanum glass. Located in the upper left corner of the nd-v diagram. Lanthanum glass from CLZ Precision Optics has the optical characteristics of high refraction and low dispersion, so it is often called high refractive index and low dispersion optical glass together with lanthanum flint and heavy lanthanum flint glass. LaK glass is developed by adding La2O3, ThO2, etc. on the basis of heavy crown glass, and the refractive index has been greatly improved. Therefore, it is also called super heavy crown glass. It is divided by v>50 and lanthanum flint phase. The low nd part is based on the RO-La2O3-B2O3 system. R can be divided into Ca, Si, Zn, Cd, etc., substituting part of SiO2 for B2O3 can improve the chemical stability of the glass. The part with high nd is based on La2O3-ThO2-B2O3 system, adding ZrO2 can improve chemical stability. Due to the pollution problem of cadmium raw materials, thorium has weak radioactivity and its use has been restricted. In order to obtain the same optical constants, it can be replaced by oxides of other rare elements such as yttrium, gadolinium, zirconium or hafnium. LaK glass is of great significance to the design of high-quality photographic objectives. Mainly used as a material for optical parts in optical lenses, such as Spherical Lenses, Cylindrical lenses.
By modifying the glass formula, the optical glass without lead, arsenic and cadmium and other radioactive elements is expressed by a prefix "H-" indicating its envioronment-friendly characteristics, for example: H-LaK1
