Performance Analysis of Surface Reconstruction Algorithms in Vertical Scanning Interferometry Based on Coherence Envelope Detection

Abstract

Optical interferometry plays an important role in the topographical surface measurement and characterization in precision/ultra-precision manufacturing. An appropriate surface reconstruction algorithm is essential in obtaining accurate topography information from the digitized interferograms. However, the performance of a surface reconstruction algorithm in interferometric measurements is influenced by environmental disturbances and system noise. This paper presents a comparative analysis of three algorithms commonly used for coherence envelope detection in vertical scanning interferometry, including the centroid method, fast Fourier transform (FFT), and Hilbert transform (HT). Numerical analysis and experimental studies were carried out to evaluate the performance of different envelope detection algorithms in terms of measurement accuracy, speed, and noise resistance. Step height standards were measured using a developed interferometer and the step profiles were reconstructed by different algorithms. The results show that the centroid method has a higher measurement speed than the FFT and HT methods, but it can only provide acceptable measurement accuracy at a low noise level. The FFT and HT methods outperform the centroid method in terms of noise immunity and measurement accuracy. Even if the FFT and HT methods provide similar measurement accuracy, the HT method has a superior measurement speed compared to the FFT method.

Development of on-machine surface profile measuring instrument based on white light interference principle

“…Online measuring instruments can be divided into contact and non-contact. The white light interference microscopy measurement technology [4] belongs to the optical interference measurement method. Its core principle is to use the interference characteristics of white light to obtain the three-dimensional shape information of the measured object by measuring and analyzing the interference fringes.…”

Carré Phase Shifting Algorithm for Wavelength Scanning Interferometry

“…The phase can be extended to be modulo 2π by examining the signs of the numerator and denominator and adjusting the phase accordingly [12]. Applying Carré analysis for continuous wavelength scanning will produce a linear phase distribution.…”

“…Takeda et al showed that a periodic fringe pattern can be evaluated by use of Fourier transform and filtering methods, a theorem that has been widely used by other researchers [7,11]. When the interference signal quality is good, the Fourier fringe analysis (FFA) method provides very accurate results, but as SNR degrades, the accuracy is significantly degraded [12]. WSI is very susceptible to environmental disturbances, and in such a case, the height or surface information estimation using the FFA produces measurement errors.…”

Surface Characterization Techniques: A Systematic Review of their Principles, Applications, and Perspectives in Corrosion Studies

“…The processing steps have been earlier discussed in detail elsewhere. 58,59 VSI offers high vertical resolution (∼0.1 nm in the z-direction) with the ability to scan large lateral areas on the order of 10 s mm 2 . 54 The advantages of VSI include: (1) accurate ability for measuring 3D surface profiles; (2) capability to manage a high vertical range of height (1 mm); (3) the utilization of an objective lens with magnifications from 10 × to 200×, VSI has the ability to produce images with large Field-Of View (FOV); 60 (4) the capability to offer better high vertical resolution (1 nm to 5 nm) over large height changes (up to 1 mm); (5) it offers a rapid, non-contact and nondestructive data acquisition.…”