Chromatic depth encoded microscopy for 3D surface measurement

Abstract

This study investigates the integration of chromatic confocal microscopy with a tuneable light source for advanced 3D surface metrology. The objective was to design and evaluate an optical setup capable of performing chromatic depth encoding, followed by 3D data reconstruction. A chromatic confocal microscope is a type of confocal microscope that includes an optical component which add longitudinal chromatic aberration. With this we can determine the height of the sample. In our experimental setup we achieved a precision of 0.51µm and 1.22µm in accuracy using a 5x/0.15NA objective. In a second part of this study, we designed a tuneable light source, capable of generating inputs with arbitrary spectra, in a versatile manner. The tuneable light source is based on a micromirror device (DMD) which can generate custom spectral patterns. The aim is that, such tuneable light source can be used in our chromatic confocal microscope to perform the required wavelength scan without requiring any spectrometer. The study concludes that the obtained results are promising whereas the selected equipment based on a LED, there is no sufficient light for combining the tuneable light source with the chromatic confocal microscope.