Measuring High-Slope and Super-Smooth Optics with High-Dynamic-Range Coherence Scanning Interferometry

Fay, Martin; Lega, Xavier Colonna de; Groot, Peter J. de

doi:10.1364/oft.2014.ow1b.3

Cited by 21 publications

(27 citation statements)

References 5 publications

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“…This method is sometimes referred to as signal oversampling. 10,19 The signal oversampling leads to a dynamic noise reduction. In principle, the noise level is inversely proportional to the square root of the data acquisition time.…”

Section: Signal Oversamplingmentioning

confidence: 99%

“…10 Recent innovations in CSI technology have increased the baseline sensitivity of a measurement. This improved sensitivity increases the capability of CSI instruments to measure surface features with high slopes or low reflectance, 19 making CSI a potentially valuable tool for process development and quality control of metal AM parts. In 2010, a good practice guide for CSI measurement of rough surfaces was published, 20 but the addition of new techniques further expands the range of measurement parameters beyond those outlined in this guide.…”

Section: Introductionmentioning

confidence: 99%

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Optimization of surface measurement for metal additive manufacturing using coherence scanning interferometry

Gómez

Thompson

et al. 2017

Opt. Eng

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Abstract. Surface topography measurement for metal additive manufacturing (AM) is a challenging task for contact and noncontact methods. We present an experimental investigation of the use of coherence scanning interferometry (CSI) for measuring AM surfaces. Our approach takes advantage of recent technical enhancements in CSI, including high dynamic range for light level and adjustable data acquisition rates for noise reduction. The investigation covers several typical metal AM surfaces made from different materials and AM processes. Recommendations for measurement optimization balance three aspects: data coverage, measurement area, and measurement time. This study also presents insight into areas of interest for future rigorous examination, such as measuring noise and further development of guidelines for measuring metal AM surfaces.

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Section: Signal Oversamplingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optimization of surface measurement for metal additive manufacturing using coherence scanning interferometry

Gómez

Thompson

et al. 2017

Opt. Eng

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“…A 100 Hz, 1024 × 1024 pixel camera allows for five averages per second, resulting in a measurement noise level of 0.072 nm/ √ Hz. Another approach to reducing noise is to more densely sample the signal, which can trade a longer acquisition time for lower noise levels without averaging individual measurements [20].…”

Section: Instrument Noisementioning

confidence: 99%

The Meaning and Measure of Vertical Resolution in Optical Surface Topography Measurement

Groot

2017

Applied Sciences

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Vertical resolution is the most widely quoted and most frequently misunderstood performance specification for equipment that measures surface topography. Here I propose to use internationally standardized terms and definitions for measurement noise and surface topography repeatability as more meaningful quantifiers for measurement performance. A specific example is an interference microscope operating with a 100 Hz, 1 k × 1 k pixel camera, and a sinusoidal phase modulation to convert intensity data to a height map. The measurement noise is found experimentally to be 0.072 nm for a 1 s data acquisition using a surface topography repeatability test, which determines the random height-equivalent noise level for an individual pixel in the areal surface topography map. Under ideal conditions, the measured noise is equivalent to the instrument noise that may be published in a performance specification in place of the more common, but poorly defined, vertical resolution specification.

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“…This is the typical case where a sample is having high reflection and low reflection regions, requiring different light illumination levels to deal against the dynamic range of the imaging camera. Several strategies are adopted here, like doing two vertical scans at different light levels [5], using HDR cameras, or even coating the sample with fluorescence polymers to increase the scattered signal on high slope regions [6].…”

Section: Surface Metrology Data Fusionmentioning

confidence: 99%

Three-dimensional measurements with a novel technique combination of confocal and focus variation with a simultaneous scan

et al. 2016

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The most common optical measurement technologies used today for the three dimensional measurement of technical surfaces are Coherence Scanning Interferometry (CSI), Imaging Confocal Microscopy (IC), and Focus Variation (FV). Each one has its benefits and its drawbacks. FV will be the ideal technology for the measurement of those regions where the slopes are high and where the surface is very rough, while CSI and IC will provide better results for smoother and flatter surface regions. In this work we investigated the benefits and drawbacks of combining Interferometry, Confocal and focus variation to get better measurement of technical surfaces. We investigated a way of using Microdisplay Scanning type of Confocal Microscope to acquire on a simultaneous scan confocal and focus Variation information to reconstruct a three dimensional measurement. Several methods are presented to fuse the optical sectioning properties of both techniques as well as the topographical information. This work shows the benefit of this combination technique on several industrial samples where neither confocal nor focus variation is able to provide optimal results.

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Measuring High-Slope and Super-Smooth Optics with High-Dynamic-Range Coherence Scanning Interferometry

Cited by 21 publications

References 5 publications

Optimization of surface measurement for metal additive manufacturing using coherence scanning interferometry

Optimization of surface measurement for metal additive manufacturing using coherence scanning interferometry

The Meaning and Measure of Vertical Resolution in Optical Surface Topography Measurement

Three-dimensional measurements with a novel technique combination of confocal and focus variation with a simultaneous scan

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