White-light fringe detection based on a novel light source and colour CCD camera

Abstract

We describe in this paper a pilot experiment of optimization of a white-light source for a low-coherence interferometry. The white-light source combines the light beams generated with colour LEDs. By modelling the white-light spectra, the contrast of a white-light interference fringe could be changed and set to the maximal value. The second part of this paper is a description of a white-light fringe analysis ensured with a low-cost colour CCD camera. The used detection technique employs a phase-crossing algorithm which identifies a zero optical path difference as the point where the phase difference between the red, green and blue parts of the white-light interference fringe becomes equal to zero. The optimized white-light source is designed to be a crucial part of an experimental setup for the surface diagnostics and automatic calibration of gauge blocks.

Coherence Correlation Interferometry in Surface Topography Measurements

“…In order to obtain high accuracy and performance out of CCI and PSI techniques, many algorithms have been proposed (Ailing et al, 2008;Buchta et al, 2011;Kim et al, 2008). Among those algorithms analyzed were: phase-shifting, phase-crossing (Pawłowski et al, 2006), zero-crossing and Fourier-transform techniques.…”

Single Shot White Light Interference Microscopy for 3D Surface Profilometry Using Single Chip Color Camera

“…In the case of white light, interference occurs only when the optical path difference (OPD) between the objective and reference beams is nearly the same (within the coherence length of the light source) so by varying one of the arms we can measure the surface roughness, small height variations and thickness of the microstructures. various schemes in WLI, such as, vertical scanning interferometry (VSI) [16,17], phase shifting interferometry (PSI) [18][19][20][21][22], fringe projection method [23][24][25][26][27], Fourier profilometry [27,28], confocal microscope [29]. In the aforementioned methods Linnik, Michelson and Mirau type interferometric objectives are used [12][13][14].…”

Frequency Noise Properties of Lasers for Interferometry in Nanometrology

“…Low-coherent or white-light interferometry exploits this effect. The center of a white-light fringe gives the information about balance between the two optical paths [41,42]. This is valid also for Michelson interferometer designed for measurement of displacement with a highly coherent laser source subject to optical frequency noise.…”