In-situ lateral confocal microscopic surface profilometry with vibration-resistance capability
Journal
Proceedings of SPIE - The International Society for Optical Engineering
Journal Volume
7544
Date Issued
2010
Author(s)
Abstract
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.
Type
conference paper