The certification for all SRM neutral density filters expires after two years. We maintain a program to recertify such filters produced by us. Filters returned for recertification are measured in the "as received" condition, taken apart and carefully cleaned, and then a final recertification measurement is made. The filters are returned to the customer with a "Report of Recertification" that serves as a replacement for the original certificate. The report contains the "as received" data as well as the new certification data, to permit the customer to evaluate the performance of the filters during the prior certification period.
Send your filters to:
NIST 100 Bureau Drive
Building 301, Receiving
Gaithersburg, MD 20899
Attention: 227/B212 Optical Filters Program