Granular Structure:
None
Striations
In all three dimensions free from striations, i.e. better than
grade A, MIL-G-174-B.
Index Homogeneity
Specified across 90% of diameter or sidelength for machined parts, respectively 80% for raw formed ingots.
In all three dimensions guaranteed total ∆n ≤ 5 • 10-6;
with power subtracted ∆n (p.s.) ≤ 2 • 10-6;
on special request total ∆n ≤ 2 • 10-6.
(Maximum weight ca. 10 kg; larger pieces available on request).
∆n (p.s.) (power subtracted) is calculated by subtracting from a measured ∆n distribution the proportion that gives an exactly spherical aberration of an originally plane optical phasefront. This subtraction procedure is built into most modern interferometer software as an option.