Cover Image, Volume 6, Issue 4

The cover of this issue, known as the Abbe diagram, depicts one of the most fundamental optical characterizations of glass, namely, the variation of index of refraction with optical wavelength for a number of glasses manufactured by Schott. Often referred to as dispersion, it is discussed extensively in an article found in this issue by Nathan Carlie: “Instantaneous Dispersion: a Window into Property Relationships for Optical Glass.” Permission from Schott to use this diagram for the cover of this issue is gratefully acknowledged image