Meaning
Optical surface profiling using a specialized microscope objective with an integrated beam splitter and a reference mirror enables non-contact, sub-nanometer height measurement of reflective surfaces. By employing mirau interferometry, metrologists can measure the surface topography of molded polymer parts without causing physical damage. This technique is limited to surfaces with moderate slope angles that can return reflected light to the objective.
Its primary application is the high-precision metrology of micro-optics and functional polymer films.
Measurement Principle
The objective splits the incoming light into two paths, directing one toward the specimen and the other toward an internal reference mirror. When these beams recombine, they form interference patterns that translate into height data. Utilizing mirau interferometry provides the vertical resolution needed for sub-nanometer topography.
Polymer Assessment
Molded optical components require extremely smooth surfaces to prevent light scattering and maintain high clarity. Through mirau interferometry, quality control teams can evaluate the surface roughness of plastic lenses immediately after ejection. This inspection ensures that the moulding process has replicated the polished finish of the cavity.
It is a critical step for validating tooling inserts and monitoring process drift.
Surface Finish
Surface roughness on the nanometer scale affects both the optical performance and the demoulding behavior of the polymer part. High surface roughness can increase friction during ejection, causing micro-tears or deformation in the molded features. The use of mirau interferometry allows moulders to detect these micro-tearing defects early, indicating when the mold requires cleaning or a release coating.
Controlling these micro-scale defects reduces reject rates and extends tool life.
