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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 nd>1.60and an vd>50, as well as an nd<1.60and an vd>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.

  Glass Type
SCHOTT
HOYA  
  Fluor Crown FK FC  
  Phosphate Crown PK PC  
  Borosilicate Crown
BK BSC  
  Light Barium Crown
BaLK BaCL  
  Crown K C  
  Zinc Crown
ZK ZnC
 
  Barium Crown
BaK BaC  
  Dense Barium Crown
SK BaCD  
  Lanthanum Crown
LaK LaC  
  Crown Flint
KF CF  
  Antimony Flint
KzF SbF  
  Light Barium Flint
BaLF BaFL  
  Extra Light Flint LLF FEL  
  Barium Flint
BaF BaF  
  Light Flint
LF FL  
  Flint
F F  
  Dense Flint
SF FD  
  Dense Barium Flint
BaSF BaFD  
  Fluor Flint
TiF FF  
  Lanthanum Flint
LaF LaF  
  Table 1: Typical Glass designation  

A more uniform method of identifying optical glass types is to use a six-digit code. The first three digits represent the nd after the decimal point, and the last three digits indicate the vd. 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 nd is 1.51680, the vd is 64.17, which yields 517642.

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