  A full-field chromatic confocal microscopy using a multispectral sensor was
developed for quasi-one-shot microscopic 3D surface measurement. An innovative
optical configuration employs a digital micromirror device (DMD) and a
multispectral sensor is used to realize chromatic confocal microscopy with
full-field area scanning. In the optical design, an area-scan type chromatic
dispersive objective is specially designed to achieve measuring specification.
Based on an 8x chromatic dispersive objective, the FOV for one shot measurement
can be reached to 1.8mm*1.3mm which is immersive to microscopic profilometry.
The spectral image captured by the multispectral sensor at each pinhole
position has a unique spectrum pattern corresponding to its conjugate measured
depth. A normalized cross-correlation (NCC) algorithm is developed to establish
a spectrum-depth response curve with its corresponding spectrum pattern sets
for accurate reconstruction of the tested 3D surface profile. With real test on
standard targets, the measurement repeatability for a single surface depth is
less than 0.6 micrometer.
