Speckle noise reduction in single-shot holographic two-wavelength contouring

Agour, Mostafa; Klattenhoff, Reiner; Falldorf, Claas; Bergmann, Ralf B.

doi:10.1117/12.2264971

Cited by 6 publications

(4 citation statements)

References 18 publications

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“…Low spatial or temporal coherent source method [77][78][79][80][81][82][83][84][85][86][87][88][89][90] Recording one hologram Increasing the adjustment difficulty of light configuration OSH method [91][92][93][94] Higher signal-to-noise ratio Complicated setup and slower recording speed FINCH method [95][96][97][98] Higher signal-to-noise ratio and dynamic measurement…”

Section: Methods Advantage Limitationmentioning

confidence: 99%

“…At the same time, the low temporal coherent source was also applied as an illumination to reduce the source coherence. For example, the femtosecond pulse laser used by Massatsch et al [83] in 2005, the Ti-sapphire pulsed laser selected by Shin et al in 2015 [84], the white light source employed by Ding et al [85] in 2010, Bhaduri et al [86] in 2012 and Bhaduri et al in 2013 [87], the light-emitting diode (LED) adopted by León-Rodríguez et al [88] in 2012, Garcia-Sucerquia [89] in 2013, and Agour et al [90] in 2017, respectively, have offered immense contributions. These kinds of methods may reduce focal depth and strictly demand the optical path difference between the object and reference beams, thus increasing the adjustment difficulty of the light configuration.…”

Section: Coherent Noise Suppressionmentioning

confidence: 99%

See 1 more Smart Citation

Recent Progress on Aberration Compensation and Coherent Noise Suppression in Digital Holography

Liu

Wang

2018

Applied Sciences

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Digital holographic microscopy (DHM) is a topographic measurement technique that permits full-field, nondestructive, dynamic, quantitative amplitude, and phase-contrast imaging. The technique may realize the lateral resolution with submicron scale and the longitudinal resolution with subnanometer scale, respectively. Improving imaging quality has always been the research focus in DHM since it has a direct effect on the precise topographic measurement. In this paper, the recent progress on phase aberration compensation and coherent noise suppression is reviewed. Included in this review are the hologram spectrum's centering judgment methods of side band in tilt phase error compensation, the physical and numerical compensation methods in phase aberration compensation, and the single-shot digital process methods in coherent noise suppression. The summaries and analyses for these approaches can contribute to improving the imaging quality and reducing the measurement error of DHM, which will further promote the wider applications of DHM in the topographic measurement fields, such as biology and micro-electro mechanical systems.

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Section: Methods Advantage Limitationmentioning

confidence: 99%

Section: Coherent Noise Suppressionmentioning

confidence: 99%

Recent Progress on Aberration Compensation and Coherent Noise Suppression in Digital Holography

Liu

Wang

2018

Applied Sciences

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“…Processes like micro cold forming, however, allow for production rates of multiple parts per second [Flo14]. Presently, no solutions exist that are fast, precise and suitable for in-process measurements at the same time [Ago17b]. Actually, most industrial quality inspection processes of micro parts rely on manual sampling using confocal microscopy.…”

Section: Introductionmentioning

confidence: 99%

Quality Control and Characterization

Maaß

Piotrowska-Kurczewski

Agour

et al. 2019

Lecture Notes in Production Engineering

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Quality inspection is an essential tool for quality assurance during production. In the microscopic domain, where the manufactured objects have a size of less than 1 mm in at least two dimensions, very often mass production takes place with high demands regarding the failure rate, as micro components generally form the basis for larger assemblies. Especially when it comes to safety-relevant parts, e.g. in the automobile or medical industry, a 100% quality inspection is mandatory. Here, we present a robust and precise metrology method comprised of a holographic contouring system with fast algorithms for geometric evaluation and surface defect detection that paves the way for inspecting cold formed micro parts in less than a second. Using a telecentric lens instead of a standard microscope objective, we compensate scaling effects and wave field curvature, which distort the reconstruction in digital holographic microscopy. To enhance the limited depth of focus of the microscope objective, depth information from different object layers is stitched together to yield 3D data of its complete geometry. The 3D data map is converted into a point cloud and processed by geometry and surface inspection. Thereby, the resulting point cloud data are automatically decomposed into geometric primitives in order to analyze geometric deviations. Additionally, the surface itself is checked for scratches and other defects by the use of convolutional neural networks. The developed machine learning algorithm makes it possible not only to distinguish between good and failed parts but also to show the defect area pixel-wise. The methods are demonstrated by quality inspection of cold formed micro cups. Defects larger than 2 lm laterally and 5 lm axially can be detected.

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“…Digital holographic two-wavelength profilometry is a very efficient technique for the measurement of surface shapes [1][2][3][4][5][6]. Due to the surface roughness, the phase extracted from each numerically reconstructed image is speckled.…”

Section: Introductionmentioning

confidence: 99%