Polarization-multiplexed snapshot lateral shearing interferometric sensor for surface roughness measurements.

• Most simple, stable, robust lateral shearing interferometer using a polarization grating compared to other interferometers. • Based on the balanced achromatic scheme between two shearing wavefronts, any kinds of optical source, even broadband light sources such as white light can be available. • Thoroughly new concept to estimate the surface roughness. • Snapshot roughness capability opposed to other optical techniques and valuable measurement results. A compact optical roughness measurement sensor based on lateral shearing interferometry is theoretically described and experimentally verified. By adopting the advanced surface roughness parameter extraction methods based on statistical machine learning technique and the partial integration approach, the sensor using a polarization grating and a polarization camera can instantaneously obtain a surface gradient map and provide reliable surface roughness parameters. To verify the operation and the performance of the sensor, a flat mirror and roughness standard specimens were measured, and the results were compared with those of a white light scanning interferometer as the reference values. As a result, the roughness parameters were very close to the reference values with <5 nm accuracy and <0.1 nm repeatability. [ABSTRACT FROM AUTHOR]