What is it?
The specifications of most laser mirror surfaces involve sub micrometer dimensions, too small to measure mechanically. Interferometry uses laser light to generate interference patterns that can be interpreted to measure the flatness, radius of curvature, or angle of a laser optic as well as other properties.
For the majority of our mirrors we use a phase shifting interferometer for quality assurance. With software analysis of the interference pattern a hard copy of the results is available to our customers. This demonstrates that surface form specifications such as power and irregularity have been met.
This measurement of the spacing and curvature of the black and white lines (or fringe pattern) can be used to interpret the optical flatness of the laser mirror.
What is it used for?
It is also useful to measure and align optical assemblies such as reflective beam expanders or collimators, with an interferometer.
Of great interest to us has been investigating the mounting of optics and observing the deformation that can occur to mirrors from poorly designed mounts or excessive mechanical force. We can supply mirrors complete with mounts and internal water cooling, proven by interferometry that the assembled mirror has not been deformed.
We also use interferometry to measure the wedge of flat laser mirrors to ensure parallelism.
Results can be reported in many different forms, such as ISO 10110, Zernike polynomials or graphically.
As part of the company’s commitment to innovation and growth we have invested in a new 3D optical profiler (Filmetrics Profilm 3D). It uses state-of-the-art white-light interferometry to enable us to measure surface roughness from sub-nanometer to millimetre scale – something that is essential for some of our customers where surface finish is vitally important. Reports are easily generated and can be supplied upon request by customers.