&lt;title&gt;Absolute shape control of microcomponents using digital holography and multiwavelength contouring&lt;/title&gt;

Seebacher, Soenke; Baumbach, Torsten; Jueptner, Werner P. O.

doi:10.1117/12.429350

Cited by 17 publications

(14 citation statements)

References 11 publications

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“…3,4 Both algorithms utilize a set of synthetic wavelengths. The first measurement, used as reference, is calculated at Λ 1 and delivers the raw phase data P 1 .…”

Section: Hierarchical Approachmentioning

confidence: 99%

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ESPI for contouring of surfaces with discontinuities

Purde¹,

Werth²,

Meixner³

et al. 2005

SPIE Proceedings

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Electronic speckle pattern interferometry (ESPI) can provide accurate contour measurement in the micron range and short measurement times far below one second. An advantage of this method is that illumination axis and observation axis can be identical in contrast to e.g. triangulation. Therefore ESPI represents an interesting alternative to other optical measurement principles used for surface profiling. Typical surfaces in industrial applications often show discontinuities, like steps or holes. An unambiguous measurement of such surfaces is only possible if the synthetic wavelength is chosen larger than the largest surface step. Since the noise level introduced to the measurement increases proportional to the synthetic wavelength, unambiguous measurements suffer from a loss of accuracy. The solution for this problem is the combination of two or more synthetic wavelengths. In contrast to other publications (hierarchical, pixel-wise approach or temporal phase unwrapping) our novel area-based approach uses only two synthetic wavelengths minimizing measurement time and device complexity. The use of areas instead of pixels allows a lower signal to noise ratio and a smaller number of synthetic wavelengths (in our case only two) respectively, compared to the hierarchical pixel based approach. In this paper we present the steps required during pre-processing (laser tilt and wave front compensation) and the opportunities and drawbacks of different algorithms used for the fusion of the two images gained from different synthetic wavelengths.

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“…3,4 Both algorithms utilize a set of synthetic wavelengths. The first measurement, used as reference, is calculated at Λ 1 and delivers the raw phase data P 1 .…”

Section: Hierarchical Approachmentioning

confidence: 99%

“…The task is to find a method to ideally combine the phase images P i calculated at different synthetic wavelengths Λ i . Figure 1 and equation (4) illustrate the problem of data fusion (data fusion = find N i ).…”

Section: Introductionmentioning

confidence: 99%

ESPI for contouring of surfaces with discontinuities

Purde¹,

Werth²,

Meixner³

et al. 2005

SPIE Proceedings

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“…In addition, as interferometric method, DH provides a non-destructive, non-contact approach for fragile objects joined with flexibility and high sensitivity to geometrical quantities such as thickness and deformation. [10][11][12]. This review paper focuses the attention on the DH procedures developed in the last years for metrological analysis of MEMS surfaces describing some numerical solutions to characterize the MEMS.…”

Section: Introductionmentioning

confidence: 99%

Digital holographic microscopy for the characterization of microelectromechanical systems

2016

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Digital holography (DH) in microscopy became an important interferometric tool in optical metrology since when camera sensors reached a higher pixel number with smaller size allowing to acquire more defined images and high-speed computers became able to process such data. Consequently, it was possible the investigation of engineered surfaces on microscale, such as microelectromechanical systems (MEMS) that are microdevices composed by mechanical elements, electronics, sensors and actuators built in a small volume, realized using different material layers superimposed in various process steps, usually starting from a silicon substrate. In DH is necessary to perform the reconstruction of the wave field by means of numerical tools. This entails a computational burden but offers the possibility of retrieving not only the intensity of the acquired wavefield, but also the phase distribution. This work describes the principles of DH and shows some interesting numerical tools suitable to process the holographic images in the field of MEMS. The use of different numerical tools is discussed and illustrated with examples taken from the literature.

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“…In common the period from one fringe system is divided by a factor of 2 by simplicity. However, this is not the optimum as shown by Osten [8]: The next smaller period must be chosen with regard to the noise. Taking this into account the spatial frequency may be increased by a factor a between two sequential fringe systems, Fig.4 This means that any additional fringe system in this sequence reduces the noise by a factor of a.…”

Section: Hierarchical Phase Shiftingmentioning

confidence: 99%

“…Δϕ/2π is the smallest resolvable phase change. Taking these relations into account results in equation for the height resolution Δz as a function of the camera pixel size pixel, the aperture k and the phase resolution Δϕ/2π: (8) There are three parameters in this equation that influence the resolution:…”

Section: Geometrical Model and Evaluationmentioning

confidence: 99%