High-precision polarized dual low-coherence scanning interferometry for rapid step height measurements.

In this investigation, we propose a polarized dual low-coherence scanning interferometer. The spatial phase-shifting technique and the concept of the dual low coherence are adopted to overcome the scanning conditions of typical low-coherence scanning interferometers and reduce the measurement time. In the proposed interferometer, the scanning interval is not critical because the visibility and the phase are immediately obtained during a scanning procedure, and the whole scanning distance can be significantly reduced by the dual low coherence. To verify the system performance, the surface profiles of a plane mirror and a step height specimen were measured, and it was confirmed that the whole scanning distance was reduced 10 times without any scanning conditions.