According to the position and glass composition of refractive index (nd) and dispersion coefficient (υd) in nd-υd domain diagram, optical glass types are classified into the 17 groups shown in table 1.
Dense Barium Flint
Dense Lanthanum Flint
Each optical glass type is designated by its glass group code and a number. In addition to our glass type designation, a six-digit code is used in this catalog. The first three digits indicate the first three numbers after the decimal point of nd while the last three digits represent the Abbe-number. For example, F4 with nd=1.62005 and υd=36.35 is indicated by its six-digit code 620-364.
Glass types which exclude lead, arsenic, cadmium and radioactive elements from their compositions are distinguished by the prefix, ＂H＂, for example, H-F4.
Low softening point glass types that are used for mould pressing are distinguished by the prefix ＂D＂, for example, D-ZK3.
High transmittance optical glass types are distinguished by the postfix “HT”, for example, H-ZF52HT.