Measurement of Steep Surfaces Using White Light Interferometry

Coupland, John N.; Lobera, Julia

doi:10.1111/j.1475-1305.2008.00595.x

Cited by 30 publications

(14 citation statements)

References 8 publications

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“…Let us take the expression of the intensity given in equation (1) and apply the Fourier transform. For Fourier analysis, we use = 2 (optical path difference) and = 1 = 2 (wave number) as variables.…”

Section: Spectral Analysis Of the Interferometric Signalmentioning

confidence: 99%

“…Coherence scanning interferometry (CSI) is a measurement method based on the acquisition of an image sequence of interference patterns resulting from the superposition of the light from the object to be measured and the light reflected from a reference mirror [1][2][3] . The measurement make use of these series of white light fringes superimposed on the image of the sample.…”

Section: Introductionmentioning

confidence: 99%

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Local reflectance spectra measurements of surfaces using coherence scanning interferometry

Claveau¹,

Montgomery²,

Flury³

et al. 2016

SPIE Proceedings

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Interference microscopy is a widely used technique in optical metrology for the characterization of materials and in particular for measuring the micro and nanotopography of surfaces. Depending on the processing applied to the interference signal, either topographic analysis of the sample can be carried out by identifying the envelope peak of the fringe signal, which leads to 3D surface imaging, or spectral analysis may be performed which gives spectroscopic measurements. By applying a Fourier transform to the interference fringes, information about the source spectrum, the spectral response of the optical system, and the reflectance spectrum of the surface at the origin of the interferogram can be obtained. By using a sample of known reflectivity for calibration, it is possible to extract the spectral signature of the entire system and therefore to deduce that of the surface of interest. In this paper, we first explain theoretically how to retrieve the reflectance information of a surface from the interferometric signal. Then, we present some results obtained by this means with a white light scanning Linnik interferometer on different kinds of samples (silicon, tin oxide (SnO 2 ), indium tin oxide (ITO)). The initial results were slightly different from those obtained with a conventional optical spectrometer until averaged temporally and were improved even further when averaged spatially. We show that the reflectance of the surface can be calculated over the given wavelength range of the effective spectrum, which is defined as the source spectrum multiplied by the spectral response of the camera and the spectral transmissivity of the optical system. We thus demonstrate that local spectroscopic measurements can be carried out with an interference microscope and that they match well with those measured with an optical spectrometer model Lambda19 UV-VIS-NIR from Perkin Elmer. A simulation study is also presented in order to validate the method and to help identify the potential sources of errors in the spectroscopic analysis.

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Section: Spectral Analysis Of the Interferometric Signalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Local reflectance spectra measurements of surfaces using coherence scanning interferometry

Claveau¹,

Montgomery²,

Flury³

et al. 2016

SPIE Proceedings

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“…A powerful microscope configuration for high-resolution optical coherence tomography applications is based on a Linnik interference microscope with high-numerical-aperture objectives 1 . The full-field OCT (FF-OCT) technique is based on whole field imaging and white-light scanning interference microscopy (WLSI), also known as coherence scanning interferometry (CSI) [2][3][4] . This technique is typically used to measure the thickness and internal structures of transparent and diffusing layers by the detection of multiple fringe envelope signals.…”

Section: Introductionmentioning

confidence: 99%

High-resolution full-field optical coherence tomography using high dynamic range image processing

Leong-Hoï¹,

Claveau²,

Montgomery³

et al. 2016

SPIE Proceedings

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Full-field optical coherence tomography (FF-OCT) based on white-light interference microscopy, is an emerging noninvasive imaging technique for characterizing biological tissue or optical scattering media with micrometer resolution. Tomographic images can be obtained by analyzing a sequence of interferograms acquired with a camera. This is achieved by scanning an interferometric microscope objectives along the optical axis and performing appropriate signal processing for fringe envelope extraction, leading to three-dimensional imaging over depth. However, noise contained in the images can hide some important details or induce errors in the size of these details. To firstly reduce temporal and spatial noise from the camera, it is possible to apply basic image post processing methods such as image averaging, dark frame subtraction or flat field division. It has been demonstrate that this can improve the quality of microscopy images by enhancing the signal to noise ratio. In addition, the dynamic range of images can be enhanced to improve the contrast by combining images acquired with different exposure times or light intensity. This can be made possible by applying a hybrid high dynamic range (HDR) technique, which is proposed in this paper. High resolution tomographic analysis is thus performed using a combination of the above-mentioned image processing techniques. As a result, the lateral resolution of the system can be improved so as to approach the diffraction limit of the microscope as well as to increase the power of detection, thus enabling new sub-diffraction sized structures contained in a transparent layer, initially hidden by the noise, to be detected.

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“…26 Despite the mitigating effect of a finite spatial frequency bandwidth, the effect of multiple scattering and loss of diffraction orders cannot be neglected and remains a problem for surfaces that are rough at the optical scale, or when coherent features such as vee-grooves or sharp edges are present. 32,33 For such complex surfaces, the CSI measurement process is fundamentally nonlinear, and consequently the linear reconstruction methods cannot reconstruct accurate surface topographies. Only an advanced reconstruction method that accounts for these effects could provide an accurate surface topography estimate for these surfaces, and such a method must be based on a rigorous scattering model.…”

Section: Introductionmentioning

confidence: 99%

“…One possible approach is outlined in Ref. 33: with some a priori information about a surface, iterative improvement of the surface topography through minimization of the differences between measured and modeled CSI images can provide accurate surface topography, even in regions typically not measured. Another application of this model is to build a virtual CSI instrument, allowing for the prediction of measurement uncertainty.…”

Section: Introductionmentioning

confidence: 99%

Modeling of interference microscopy beyond the linear regime

Thomas

Nikolaev

et al. 2020

Opt. Eng.

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Coherence scanning interferometry (CSI), a type of interference microscopy, has found broad applications in the advanced manufacturing industry, providing high-accuracy surface topography measurement. Enhancement of the metrological capability of CSI for complex surfaces, such as those featuring high slopes and spatial frequencies and high aspect-ratio structures, requires advances in modeling of CSI. However, current linear CSI models relying on approximate surface scattering models cannot accurately predict the instrument response for surfaces with complex geometries that cause multiple scattering. A boundary elements method is used as a rigorous scattering model to calculate the scattered field at a distant boundary. Then, the CSI signal is calculated by considering the holographic recording and reconstruction of the scattered field. Through this approach, the optical response of a CSI system can be predicted for almost any arbitrary surface geometry. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Measurement of Steep Surfaces Using White Light Interferometry

Cited by 30 publications

References 8 publications

Local reflectance spectra measurements of surfaces using coherence scanning interferometry

Local reflectance spectra measurements of surfaces using coherence scanning interferometry

High-resolution full-field optical coherence tomography using high dynamic range image processing

Modeling of interference microscopy beyond the linear regime

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