Glass Designation

The most common types of glasses used in optics are classified into crown glasses and flint glasses with designations based on their refractive indices and dispersions. Crown glasses have a bigger Abbe value with an n_d>1.60and an v_d>50, as well as an n_d<1.60and an v_d>55. In SCHOTT designation, Crown glasses have a designation letter K, while flint glasses have a designation letter F. To differentiate the various types of optical glasses, a letter/letters and number designation are used. The letter identifies the basic chemical composition, while the number is to further differentiate glass types within a group. Table 1 gives an overview of optical glasses from SCHOTT and HOYA.

A more uniform method of identifying optical glass types is to use a six-digit code. The first three digits represent the n_d after the decimal point, and the last three digits indicate the v_d. If the fourth digit is bigger than 4, 1 is added to the first three digits. For example, N-BK7, the most widely used optical glass, the n_d is 1.51680, the v_d is 64.17, which yields 517642.

Properties:  

• Refractive Index, Abbe Value and Dispersion Formula
• Transmittance
• Temperature Coefficient of Refractive Index (dn/dT) (Source: SCHOTT North America, Inc.)
• Glass Designations
• Thermal Properties
• Chemical properties (Source: SCHOTT North America, Inc.)
• Mechanical Properties (Source: SCHOTT North America, Inc.)
• Abbe Diagram (n_d-v_d) Graphic (Source: SCHOTT North America, Inc.)
• N-BK7 Datasheet (Source: SCHOTT North America, Inc.)