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document
Shao, Y. (author), Loktev, Mikhail (author), Tang, Y. (author), Bociort, F. (author), Urbach, Paul (author)
For advanced imaging systems, e.g., projection systems for optical lithography, spatially varying aberration calibration is of utmost importance to achieve uniform imaging performance over the entire field-of-view (FOV). Here we present an efficient, accurate, and robust spatially varying aberration calibration method using a pair of 2...
journal article 2019
document
Konijnenberg, A.P. (author), Coene, W.M.J.M. (author), Urbach, Paul (author)
A noise-robust extension of iterative phase retrieval algorithms that does not need to assume a noise model is proposed. It works by adapting the intensity constraints using the reconstructed object. Using a proof-of-principle ptychographic experiment with visible light and a spatial light modulator to create an object, the proposed method is...
journal article 2018
document
Konijnenberg, A.P. (author), Lu, Xingyuan (author), Liu, Leixin (author), Coene, W.M.J.M. (author), Zhao, C.L. (author), Urbach, Paul (author)
A novel non-iterative phase retrieval method is proposed and demonstrated with a
proof-of-principle experiment. The method uses a fixed specially designed mask and through-focus intensity measurements. It is demonstrated that this method is robust to spatial partial coherence in the illumination, making it suitable for coherent diffractive...
journal article 2018
document
Meng, P. (author), Pereira, S.F. (author), Urbach, Paul (author)
Rigorous vectorial focusing theory is used to study the imaging of small adjacent particles with a confocal laser scanning system. We consider radially polarized illumination with an optimized amplitude distribution and an annular lens to obtain a narrower distribution of the longitudinal component of the field in focus. A polarization...
journal article 2018
document
Strauch, M. (author), Somers, P.A.A.M. (author), Bociort, F. (author), Urbach, Paul (author)
A technique to create aspheric surface shapes on commercially available electrowetting liquid lenses is demonstrated. Based on a previously published surface oscillation model a technique using a Hankel transform is proposed and tested experimentally. An alternating actuation voltage is applied to the liquid lens to stimulate surface...
journal article 2018
document
Xu, Xiaosi (author), Konijnenberg, A.P. (author), Pereira, S.F. (author), Urbach, Paul (author)
Coherent Fourier scatterometry is an optical metrology technique that utilizes the measured intensity of the scattered optical field to reconstruct certain parameters of test structures written on a wafer with nano-scale accuracy. The intensity of the scattered field is recorded with a camera and this information is used to retrieve the...
journal article 2017
document
Li, X. (author), Wei, L. (author), Poelma, René H. (author), Vollebregt, S. (author), Wei, J. (author), Urbach, Paul (author), Sarro, P.M. (author), Zhang, G.Q. (author)
This paper presents a tuneable binary amplitude Fresnel lens produced by wafer-level microfabrication. The Fresnel lens is fabricated by encapsulating lithographically defined vertically aligned carbon nanotube (CNT) bundles inside a polydimethyl-siloxane (PDMS) layer. The composite lens material combines the excellent optical absorption...
journal article 2016
document
Nemati, M. (author), Loozen, G.B. (author), Van der Wekken, N. (author), Van de Belt, G. (author), Urbach, H.P. (author), Bhattacharya, N. (author), Kenjeres, S. (author)
A preliminary comparative measurement between particle imaging velocimetry (PIV) and laser speckle contrast analysis (LASCA) to study pulsatile flow using ventricular assist device in a patient-specific carotid artery phantom is reported. These full-field optical techniques have both been used to study flow and extract complementary parameters....
journal article 2015
document
Reyes Reyes, A. (author), Hou, Z. (author), Van Mastrigt, E. (author), Horsten, R.C. (author), De Jongste, J.C. (author), Pijnenburg, M.W. (author), Urbach, H.P. (author), Bhattacharya, N. (author)
We present a broadband quantum cascade laser-based spectroscopic system covering the region between 850 and 1250 cm?1. Its robust multipass cavity ensures a constant interaction length over the entire spectral region. The device enables the detection and identification of numerous molecules present in a complex gas mixture without any pre...
journal article 2014
document
Nemati, M. (author), Presura, C.N. (author), Urbach, H.P. (author), Bhattacharya, N. (author)
Continuous health monitoring has become a major theme of our aging society. Portable devices play an important role here. Many optical portable devices are susceptible to motion induced artifacts. We have performed an experimental study for detection of fluid pulsation based on multi-exposure speckle images, in presence of motion induced...
journal article 2014
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