Special Firestone glass
Special Firestone glass is referred to as TF glass. It is a type of special dispersion colorless optical glass. Generally, the relative dispersion deviation Δpxy of flint glass in the short-wave area is close to zero or positive, while TF glass has a larger negative value, that is, the dispersion in the short-wave area is small, so this feature can be used to eliminate the secondary spectrum in the optical system error . According to the composition characteristics, it can be divided into two categories: ①Borosarsenate glass with Sb2O3 and As2O3 as the main components (but As2O3 is highly toxic and not commonly used), it also has different names such as short flint, antimony flint, telescope flint glass, etc.; ② The glass mainly based on PbO-B2O3 system has larger refractive index and dispersion than the former. There are also ultra-short flint glass and boron flint glass abroad. Mainly used as a material for optical parts in high-quality optical systems.
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-TF3L.
