Assertion: absolute flatness | /r/HasProperty | determined
Facets:
value: by performing an interferometer test
type: MANNER
Source sentences:
text: Because the flatness of an optical flat is relative to the flatness of the original test flat, the true (absolute) flatness at the time of manufacture can only be determined by performing an interferometer test using a liquid flat, or by performing a "three flat test", in which the interference patterns produced by three flats are computer-analyzed.