Fast surface measurement using wavelength scanning interferometry with compensation of environmental noise

Abstract

We introduce a new optical interferometry system for fast areal surface measurement of microscale and nanoscale surfaces that are immune to environmental noise. Wavelength scanning interferometry together with an acousto-optic tunable filtering technique is used to measure surfaces with large step heights. An active servo control system serves as a phase-compensating mechanism to eliminate the effects of environmental noise. The system can be used for online or in-process measurement on a shop floor. Measurement results from two step height standard samples and a structured surface of a semiconductor daughterboard are presented. In comparison with standard step height specimens, the system achieved nanometer measurement accuracy. The measurement results of the semiconductor daughterboard, under mechanical disturbance, showed that the system can withstand environmental noise.

Implementation of in Process Surface Metrology for R2R Flexible PV Barrier Films

“…The WSI shown in Fig. 3 can take areal measurements without mechanical movement by simply changing the wavelength of a broadband light source in the interferometer setup [8]. This wavelength scanning process can ensure a phase shifting operation faster than conventional mechanical scanning methods.…”

“…The noise cancellation can ensure the fringe stabilization before the wavelength scanning measurement process is carried out [8]. As such, any alteration to the optical path (vertical) will be considered as a noise source and can be compensated by the active control loop if the noise range is within the stabilization bandwidth.…”

A method for inspecting near-right-angle V-groove surfaces based on dual-probe wavelength scanning interferometry

“…The method relies on wavelength scanning interferometry (WSI) [14][15][16] which can achieve measurement with axial resolutions approaching the nanometre [17] without the requirement for the mechanical scanning of either the sample or optics, unlike comparable techniques such as CSI. This lack of mechanical scanning opens up the possibility of using a dual-probe optics system to provide simultaneous measurement with two adjacent fields of view.…”

Correction of Scanning Steps to Improve Accuracy in Interferometric Profilometer

“…In present time a lot of attention is paid to improvement of interference measurement accuracy [1][2][3][4]. The presence of noise in interferograms and non-linearity of the scanning system leads to distortion of the correlogram functions and error in the measurement results.…”