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15 November 2011Full-field chromatic confocal surface profilometry employing DMD
correspondence for minimizing lateral cross talks
In the research, full-field chromatic confocal surface profilometry employing digital micro-mirror device (DMD) for
spatial correspondence is proposed to minimize lateral cross talks between individual detection sensors. Although fullfield
chromatic confocal profilometry is capable of enhancing measurement efficiency by completely removing timeconsuming
vertical scanning operation, its vertical measurement resolution and accuracy are still severely affected by the
potential sensor cross talk problem. To overcome this critical bottleneck, a DMD-based chromatic confocal method is
developed by employing a specially-designed objective for chromatic light dispersion and a DMD for lateral pixel
correspondence and scanning. Using the chromatic objective, the incident light is dispersed according to a pre-designed
detection range from a few micrometers to several millimeters and a full-field reflected light is captured by a three-chip
color camera for multi color detection. Using this method, the full width half maximum (FWHM) of the depth response
curve can be significantly sharpened, thus improving the vertical measurement resolution and repeatability of the depth
detection. From our preliminary experimental evaluation, it is verified that the ±3σ repeatability of the height
measurement can be kept within 2% of the overall measurement range.