http://www.zemax.com/kb en-us N/A support@zemax.com Thu, 15 May 2008 22:31:10 PDT 20 http://www.zemax.com/kb/articles/158/1/Take-Care-With-Exact-Equivalent-Glasses/Page1.html A few years ago the manufacturers of optical glasses started the process of reformulating their glasses to remove arsenic and lead. At first glance, most of these glasses appear to be the exact equivalents of the original glasses. However, examining the indices in the near UV and the NIR shows that the indices can differ in the 3rd decimal place.

Further more, many other properties of the glasses differ significantly: the new formula glasses absorb earlier at each end of the spectrum, and there can be massive differences in the thermal properties between the old and new formulations.

This article discusses these topics, and shows some traps it is easy to fall into with 'Exact Equivalent' glasses.

This article is also available in Japanese.

]]> no@spam.com (Eddie Judd) http://www.zemax.com/kb/articles/158/1/Take-Care-With-Exact-Equivalent-Glasses/Page1.html