Characteristic of Glass Materials

The glass materials used by Sigma Koki can be roughly classified into one of two groups, depending on their intended use: glass for total reflection and glass for transmission. Since optical materials for total reflection applications use only their surfaces and do not demand special materials, they are selected for convenience in polishing and thermal stability of the polished surfaces. In contrast, optical materials for light transmission applications use both the surfaces and the interior, making characteristics such as transmittance, homogeneity, and presence or absence of internal bubbles important, in addition to properties of total reflectance glass material. The refractive index of glass is a major consideration for lenses that refract light, while both light dispersion and refractive index are important for prisms and combination lenses. Glass for light transmission applications is carefully selected from several hundreds types of optical glass, after considering optical characteristics, as well as characteristics such as cost and chemical and physical properties.

Typically of higher quality than ordinary glass, optical glass has specific refractive indices and must meet certain requirements for striae, bubbles, and other characteristics.