Surface profilometry with composite interferometer

Self-referenced Surface Profilometry

INTRODUCTION In optical surface metrology the reference surface is usually self-calibrated against the part under test because the errors in the reference are of the same order as those in the part under test. The self-calibration, or “absolute test”, is typically done by making three interferometric measurements, an initial measurement and then two more with the part under test shifted lateral...

Heterodyne moiré surface profilometry.

In this study, a novel moiré fringe analysis technique is proposed for measuring the surface profile of an object. After applying a relative displacement between two gratings at a constant velocity, every pixel of CMOS camera can capture a heterodyne moiré signal. The precise phase distribution of the moiré fringes can be extracted using a one-dimensional fast Fourier transform (FFT) analysis o...

O-ring Surface Inspection With 3D Profilometry

Longitudinal spatial coherence applied for surface profilometry.

A method of optical coherence profilometry, believed to be new, is demonstrated. This method is based on the spatial, rather than the temporal, coherence phenomenon. Therefore the proposed interferometric system is illuminated by a quasi-monochromatic spatial incoherent source instead of a broadband light source. The surface profile is measured by means of shifting the spatial degree of coheren...

A single-shot line-scanning spatially dispersed short coherence interferometer using Fourier transform profilometry

Single-shot inspection at nanoscale resolution is a problematic challenge for providing on-line inspection of manufacturing techniques such as roll-to-roll processes where the measurand is constantly moving. An example of such a measurement challenge is defect detection on vapor barrier films formed by depositing an aluminum oxide layer several tens of nanometres thick on a flexible polymer sub...