NBN ISO 14997:2021

This document specifies the physical principles and practical means for the implementation of methods
for evaluating surface imperfections.
For imperfections specified using the visibility method, two inspection methods are described. The first
is visual evaluation of the surface without any comparison standard (IVV). The second is a visibility
assessment of a surface imperfection when compared to an artefact of known brightness (ISV).
For imperfections specified using the dimensional method, three methods are described. The first is
visual evaluation of the surface without any comparison standard (IVD). The second is a dimensional
assessment of a surface imperfection when compared to an artefact of known size (ISD). The third is
the dimensional measurement of a surface imperfection using magnification and either a comparison
artefact of known size or a reticle or ruler (IMD).
Instruments exist that allow objective measurement of brightness (digital scatterometry) or size
(digital microscopy). While these instruments can be used for evaluation of surface imperfections, they
are beyond the scope of this document.
This document applies to optical surfaces of components or assemblies such as doublets or triplets.
This document can be applied to optical plastic components; however, attention is drawn to the fact
that impact damage to plastic materials often looks very different from that on harder materials as it
does not always result in the removal of material but instead can displace material, causing ripples in
the surface. Consequently, visual comparisons of scratch and dig damage to plastic with those on glass
or crystalline materials can give very different results.