Chromatic confocal surface profilometry employing signal recovering methodology for simultaneously resolving lateral and axial cross talk problems

In this research, novel deconvolution methodology is proposed to resolve the lateral and axial cross-talk problems encountered in line-scanning chromatic confocal surface profilometry. The strategy integrates chromatic confocal principle, infinitive microscopic optics and deconvolution theory to resolve the entangled cross-talk problem in microscopic confocal measurement, so the measuring resolution can be greatly enhanced from the level of the traditional line-scanning up to the one achieved by generally traditional point-type confocal measurement. To overcome the problem, this research analyzes the physical phenomenon of optical near field using photonic spectrum analyses for establishing relationship between the light expansion and propagation depth, as well as light wavelength. In the confocal image, acquired spectrum intensity can be regarded as the convolution between the ideal signal from objects and the point spread function (PSF) of incident light. By employing spectrum analyses, important calibrated characteristics of the PSF along both of the lateral and depth directions can be carefully established. By using the individual PSF for its corresponding wavelength detected at its matching focal depth, the proposed deconvolution method has been proved effective theoretically and experimentally in greatly minimizing the full width half maximum (FWHM) of the depth response curve by more than 25 times, thus significantly improving the accuracy and repeatability of microscopic surface profilometry.