Open AccessComparison of three focus sensors for optical topography measurement of rough surfaces
Author(s) -
Martin Šarbort,
Miroslava Holá,
Jan Pavelka,
P. Schovánek,
Šimon Řeřucha,
Jindřich Oulehla,
Tomáš Fořt,
Josef Lazar
Publication year - 2019
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.27.033459
Subject(s) - optics , speckle pattern , focus (optics) , monochromatic color , materials science , laser , axicon , surface roughness , root mean square , light intensity , physics , laser beams , composite material , quantum mechanics
The study compares three variants of focus sensors designed for the optical topography measurement of rough surface specimens with submicron accuracy. We present a theoretical analysis of the focus sensor principles and the experimental measurements with a single point laser probe. A low coherent illumination beam was provided by a monochromatic laser source and a rotating diffuser, which reduced the speckles generated by the rough surface. The reflected beam was modulated by three specific optical elements (axicon, double wedge prism, four spherical lenses) realized by a spatial light modulator. A digital camera detected the output intensity patterns that were evaluated by the intensity centroid method. The results showed a good coincidence of the surface profiles obtained by the three sensor variants with the root-mean-square deviations below one micron. We discuss the results obtained for several specimens with various surface roughness and compare the differences between the three focus sensor variants.