Principles of interference microscopy for the measurement of surface topography

Groot, Peter J. de

doi:10.1364/aop.7.000001

Cited by 285 publications

(179 citation statements)

References 147 publications

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“…Conversely, once we have a noise level expressed with respect to a time bandwidth, we can often adjust the data acquisition time or number of averages to reach a desired measurement precision. To illustrate the importance of including data acquisition time in an STR evaluation, Figure 2 shows the use of time averaging with sinusoidal phase shifting interferometry [19]. A 100 Hz, 1024 × 1024 pixel camera allows for five averages per second, resulting in a measurement noise level of 0.072 nm/√Hz.…”

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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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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“…computer-generated holograms [2] or optical path length variation). Commonly used methods are scanning white-light (SWLI) or phase-shifting interferometry (PSI) [3], [4]. Using SWLI, a depth scan is performed by moving a specimen along the optical axis.…”

Section: Introductionmentioning

confidence: 99%

Combination of a fast white-light interferometer with a phase shifting interferometric line sensor for form measurements of precision components

Laubach

Ehret

Riebling

et al. 2017

Optical Measurement Systems for Industrial Inspection X

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Modern industrial fabrication processes put high requirements on the quality of the surface form of precision-machined components, e.g. optical lenses or microelectromechanical systems (MEMS). Optical sensors provide high precision non-contact surface measurement to verify these quality requirements, even on fragile surfaces. The low-cost line-scanning interferometer that is presented in this contribution is based on a Michelson interferometer configuration in combination with a high-speed line-scan camera. The sensor can operate in scanning white-light or in optical path length modulation (OPLM) mode. The white-light mode is used to automatically align the sensor perpendicular in the working distance of 13 mm to the surface of the specimen. In OPLM-mode, an oscillating reference mirror and a band-pass filtered light source are used, to measure the form of a radial symmetric specimen with a diameter of up to 25.4 mm with interferometric accuracy. Several overlapping ring-shaped sub-apertures are measured iteratively in different radial positions until the whole surface is scanned. The sub-apertures are stitched together to reconstruct the complete 3D-topography, while overlapping areas can be used to correct movement errors of the scanning axes. This concept is highly adaptive and can be applied to many different specimen geometries e.g. planes, spheres or aspheric glass lenses.

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“…Reflection interference contrast microscopy (RICM) [10] was used to analyze the surface profile of stratified media for wetting studies and for membrane topography [11]. De Groot recently reviewed interference microscopy for the measurement of surface topography [12]. Surface topography should not be confused with thin film thickness measurement.…”

Section: Introductionmentioning

confidence: 99%

Super-resolved thickness maps of thin film phantoms and in vivo visualization of tear film lipid layer using OCT

Santos

Schmetterer²,

Triggs

et al. 2016

Biomed. Opt. Express

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In optical coherence tomography (OCT), the axial resolution is directly linked to the coherence length of the employed light source. It is currently unclear if OCT allows measuring thicknesses below its axial resolution value. To investigate spectral-domain OCT imaging in the super-resolution regime, we derived a signal model and compared it with the experiment. Several island thin film samples of known refractive indices and thicknesses in the range 46 − 163 nm were fabricated and imaged. Reference thickness measurements were performed using a commercial atomic force microscope. In vivo measurements of the tear film were performed in 4 healthy subjects. Our results show that quantitative super-resolved thickness measurement can be performed using OCT. In addition, we report repeatable tear film lipid layer visualization. Our results provide a novel interpretation of the OCT axial resolution limit and open a perspective to deeper extraction of the information hidden in the coherence volume.

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Principles of interference microscopy for the measurement of surface topography

Cited by 285 publications

References 147 publications

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

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

Combination of a fast white-light interferometer with a phase shifting interferometric line sensor for form measurements of precision components

Super-resolved thickness maps of thin film phantoms and in vivo visualization of tear film lipid layer using OCT

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