Optimization of white light interferometry on rough surfaces based on error analysis

Saraç, Zehra; Groß, Reinhard; Richter, Claus Peter; Wiesner, Bernhard; Häusler, Gerd

doi:10.1078/0030-4026-00369

Cited by 27 publications

(12 citation statements)

References 8 publications

(7 reference statements)

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“…The design of the displacement sensor is similar to previous extrinsic fiber optic interferometric sensors based on the gap formed between the cleaved endfaces of two optical fibers [1,[4][5][6][7]. As shown in Figure 1, the sensor is fabricated by aligning the collimated output of a graded-index (GRIN) lens mounted on the end of an optical fiber at 90º to a reflective target surface [1].…”

Section: Measurement Principlementioning

confidence: 99%

High-G effects on optical fiber based displacement sensing for re-entry bodies

Nadler

Greene

2006

SPIE Proceedings

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Re-entry bodies are subject to extreme conditions, among them the rigorous shock, vibration, and loading characteristics that can often induce noise or loss of measurement. Restrictions by the Department of Energy on spark sources within a sealed body require the exclusive use of fiber optics for sensing. A joint effort between Los Alamos National Laboratory and Lambda Instruments has developed and evaluated a white light interferometric fiber sensor to address these concerns while measuring displacements between high explosive components in potential flight applications. The sensor offers advantages with electro-magnetic immunity, non-contact sensing elements, and high sensitivity to movement. Gap values are calculated from the extrema of the sinusoidal wavelength pattern created by the Fabry-Perot cavity between the lens and explosive surface, collected by an optical spectrum analyzer and interpreted by an external computer. This paper focuses on the interferometric concept and experimental data received from the unit in real-time during centrifuge tests. Results from single and multimode versions are presented and reported in their effectiveness for 0-2 millimeter measurements.

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Section: Measurement Principlementioning

confidence: 99%

High-G effects on optical fiber based displacement sensing for re-entry bodies

Nadler

Greene

2006

SPIE Proceedings

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“…It was found that, with increasing wavelengths, the average speckle size increases. It is known that light source selection using rough surface illumination is crucial when especially high accuracy roughness measurements are required [18]. It is therefore important to establish an extensive relationship between the wavelength, speckle size and roughness.…”

Section: Discussionmentioning

confidence: 99%

Autocorrelation analysis of spectral dependency of surface roughness speckle patterns

Kayahan

Gündoğdu

Hacizade

et al. 2009

2009 International Symposium on Optomechatronic Technologies

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When a surface is illuminated with a highly coherent light such as a laser beam, the speckle pattern of bright and dark regions is observed. It depends on the surface parameters and carries important information about the roughness of the surface. Various methods and techniques are employed for the determination of surface roughness parameters from speckle pattern properties. In this paper, an experimental approach for surface roughness evaluation based on the autocorrelation analysis of the spectral properties of speckle patterns caused by milled metal surfaces is reported. The speckles at three 633, 604 and 543 nm wavelengths of He-Ne laser were analyzed. It was found that autocorrelation analysis is very sensitive to small variations in speckle sizes, caused by spectral properties of speckle patterns such as increasing the wavelength lead to increased speckle sizes. The results are in good agreement with the results obtained from the mechanical stylus profilometer for the milled metal surfaces with roughness values R a ; 0.36µm (low roughness) and 1.98µm (high roughness). The technique reported here has a great potential for precise and non-contact optical measurements of rough surfaces.

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“…mechanical parts with sudden and very step changes in their form) and, (c) before splitting the COP, some of ones were severely corrupted with random noise in order to simulated the speckle noise produced by the surface roughness. 2 The Matlab function "randn" was used to produce the random noise. In order to simulate surface roughness, this function was applied to generate arrays of random numbers whose elements are normally distributed with mean 0 and standard deviation σ=0.2 µm.…”

Section: Evaluation Of the Aligning And Stitching Algorithmmentioning

confidence: 99%

A novel algorithm to stitch adjacent cloud of points of long cylindrical surfaces

Viotti

Albertazzi

Pont³

et al. 2007

SPIE Proceedings

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This paper presents an algorithm based on Least Absolute Method to align and stitch multiple adjacent cylindrical clouds of points measured by white light interferometry using conical mirrors. The evaluation of the aligning and stitching algorithm was initially performed by using several numerically simulated clouds of points (COP) of cylindrical surfaces with small shape errors and quite rough surfaces. In order to evaluate the algorithm, each numerically generated COP was split into two parts but always keeping an overlapping area. Numerical translations and rotations were applied in one part to simulate real misalignments. After this, the algorithm was applied to align each adjacent COP pair and to obtain a stitched COP, and the result was compared with the original one. In this way, the performance of the presented algorithm was evaluated and analyzed for several overlapped areas. Excellent results were obtained with an overlapping area of 25% of the total measured length. The differences between the stitched and original cloud of points were always far below the roughness level of the measured surface. A brief description of a modified white light interferometer to measure in cylindrical coordinates as well as early applications of the algorithm in real measurements is also presented.

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Optimization of white light interferometry on rough surfaces based on error analysis

Cited by 27 publications

References 8 publications

High-G effects on optical fiber based displacement sensing for re-entry bodies

High-G effects on optical fiber based displacement sensing for re-entry bodies

Autocorrelation analysis of spectral dependency of surface roughness speckle patterns

A novel algorithm to stitch adjacent cloud of points of long cylindrical surfaces

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