29th Jan 2021
Automated Inspection of Surface Quality
The surface quality of optics is specified and measured in many ways. Many applications require a particular surface shape, or form, whether this be for a lens or an optical flat. Additionally, surface finish / texture / roughness can be important, especially for high power laser applications. Optical technicians use a variety of instruments, commonly based around interferometry, to precisely inspect these parameters to nanometre precision.
Alongside this measurement of form and finish, there are various standards categorising the general quality of optical polish, identifying the level of local imperfections – or scratch-dig. The industry specification for this imposes limits on either the feature size (ISO 10110-7) or the magnitude of apparent scatter (MIL13838B) from an imperfection and, given the associated ‘accumulation rules’ is a much more elusive parameter to tie-down.