Designation of optical glass types
Design of Optical Glass Types
In the course of Ohara’s long history, many types of optical glasses have been developed. In this catalog, you will find over 130 glasses which we have selected as our “recommended glass types”. Each optical glass has its own properties which are closely connected with the key chemical element it contains.
With this in mind, we have developed a new glass type designation system and the new names are used in this catalog. On the nd/vd diagram, located on the Optical Catalog webpage, you will see we have divided our glasses into groups. For each glass type, we have selected on or two chemical elements contained which are considered the most important and have used the atomic symbols of these for the first two letters of the glass type designation. The third letter of the glass type designation refers to the refractive index of each glass type within its glass group: H, M, or L for high, middle, or low. Lastly we assign a one or two digit number to each glass type within a given glass family. Thus each glass type is represented by the above-mentioned three letters plus a one or two digit number.
We are also adding the prefix “S-“ to indicate which of the glass types are ECO optical glasses and environmentally “Safe”. These glass types do not contain any lead or arsenic.
For example, the glass type designation for S-BSL7 is composed as follows:
S- stands for environmentally Safe
B represents Boron, one of the key compositional elements
S represents Silicon, one of the key compositional elements
L indicates a Low index within the BS group
7 indicates this is the 7th glass within this glass family
Along with Ohara’s glass type designation, the technical data sheets will show the six-digit code for each glass type. In the six-digit code the first three digits represent the refractive index at the helium line (nd) and the last three digits represent the Abbe number (vd). These six-digit codes are internationally recognized within the optical community.