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In the article, an in-situ 3-D microscopic surface profilometer employing novel lateral confocal scanning principle, also
called V-scan lateral confocal microscopy (VLCM), was developed to achieve in-field measurement with an effective
vibration-resistance capability. The developed methodology combines digital structured fringe projection, lateral
confocal scanning, shape from focus (SFF) and anti-vibration technique to perform lateral scanning for in-situ 3-D
surface measurement. For microstructures having low reflectivity and high-slope surfaces to be measured within in-field
process environment, it has been recognized as a great challenge for achieving accurate 3-D surface inspection. To
overcome this, the presented method employing a new lateral confocal scanning strategy in combining a Z-axis vertical
scanning with a horizontal X-axis scanning simultaneously, in which the scan pattern is similar to a V-shape. Meanwhile,
to detect potential environmental vibration, a laser fiber interferometric positioning sensor based on heterodyne
interferometry is employed to detect potential vibratory displacement between the optical probe and a tested surface for
minimizing environment disturbance encountered in a real factory. A depth response curve is constructed by a series of
images detected from successive depths during the V-scan lateral scanning. Potential vibration errors can be effectively
detected by a fiber optic interometric positioning sensor and compensated simultaneously. A standard step-height target
and several industrial V-groove microstructures have been measured to attest the measurement accuracy and feasibility
of the developed approach. From the experimental results, it is confirmed that the depth resolution can reach 0.1 μm and
the maximum measurement error can be controlled within 3% of the overall measuring height.
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