Joseph Maubach - Academia.edu (original) (raw)
Papers by Joseph Maubach
Optical Engineering, 2011
[Optical Engineering 50, 103201 (2011)]. Maria E. Rudnaya, Robert MM Mattheij, Joseph ML Maubach,... more [Optical Engineering 50, 103201 (2011)]. Maria E. Rudnaya, Robert MM Mattheij, Joseph ML Maubach, Hennie G. ter Morsche. Abstract. ... MTPostek and AEVladar, ???Image sharpness measurement in scanning electron microscopy-Part I,??? Scanning 20, 1???9 (1998). ...
Engineering Fracture Mechanics, 2010
A simultaneous autofocus and two-fold astigmatism correction method for electron microscopy is de... more A simultaneous autofocus and two-fold astigmatism correction method for electron microscopy is described. The method uses derivative-free optimization in order to find a global optimum of an image variance, which is an image quality measure. The Nelder-Mead simplex method and the Powell interpolation-based trust-region method are discussed and compared for an application running on a scanning transmission electron microscope.
Microscopy and Microanalysis, 2011
Most autofocus methods are based on a sharpness function which delivers a real-valued estimate of... more Most autofocus methods are based on a sharpness function which delivers a real-valued estimate of an image quality. In this paper we study an L2−norm gradient-based sharpness function for two-dimensional images (2-D setting). Within this setting we are able to take into account the asymmetry of the optical device objective lens (astigmatism aberration). This study provides a useful extension of the analytical observations for one-dimensional images (1-D setting) that have been done before. The gradient-based autofocus method is implemented and demonstrated for the real-world application running in the FEI scanning transmission electron microscope prototype.
Microscopy and Microanalysis, 2009
Journal of the Optical Society of America A, 2011
The Fourier modal method (FMM) is a method for efficiently solving Maxwell's equations with perio... more The Fourier modal method (FMM) is a method for efficiently solving Maxwell's equations with periodic boundary conditions. In order to apply the FMM to nonperiodic structures, perfectly matched layers need to be placed at the periodic boundaries, and the Maxwell equations have to be formulated in terms of a contrast (scattered) field. This reformulation modifies the structure of the resulting linear systems and makes the direct application of available stable recursion algorithms impossible. We adapt the well-known S-matrix algorithm for use with the aperiodic FMM in contrast-field formulation. To this end, stable recursive relations are derived for linear systems with nonhomogeneous structure. The stability of the algorithm is confirmed by numerical results.
Journal of Microscopy, 2010
Fast and reliable autofocus techniques are an important topic for automated scanning electron mic... more Fast and reliable autofocus techniques are an important topic for automated scanning electron microscopy. In this paper, different autofocus techniques are discussed and applied to a variety of experimental through-focus series of scanning electron microscopy images with different geometries. The procedure of quality evaluation is described, and for a variety of scanning electron microscope samples it is demonstrated that techniques based on image derivatives and Fourier transforms are in general better than statistical, intensity and histogrambased techniques. Further, it is shown that varying of an extra parameter can dramatically increase quality of an autofocus technique.
Journal of Mathematical Imaging and Vision, 2012
Most automatic focusing methods are based on a sharpness function, which delivers a real-valued e... more Most automatic focusing methods are based on a sharpness function, which delivers a real-valued estimate of an image quality. In this paper, we study an L 2-norm derivative-based sharpness function, which has been used before based on heuristic consideration. We give a more solid mathematical foundation for this function and get a better insight into its analytical properties. Moreover an
Journal of Computational Physics, 2012
The aperiodic Fourier modal method in contrast-field formulation is a numerical discretization an... more The aperiodic Fourier modal method in contrast-field formulation is a numerical discretization and solution technique for solving scattering problems in electromagnetics. Typically, spectral discretization is used in the finite periodic direction and spatial discretization in the orthogonal direction. In the light of the fact that the structures of interest often have a large width-to-height ratio and that the two discretization approaches have different computational complexities, we propose exchanging the directions for spatial and spectral discretization. Moreover, if the scatterer has repeating patterns, swapping the discretization directions facilitates the reuse of previous computations. Therefore, the new method is suited for scattering from objects with a finite number of periods, such as gratings, memory arrays, metamaterials, etc. Numerical experiments demonstrate a considerable reduction of the computational costs in terms of time and memory. For a specific test case considered in this paper, the new method (based on alternative discretization) is 40 times faster and requires 100 times less memory than the method based on classical discretization.
Journal of the Optical Society of America A, 2010
This paper extends the area of application of the Fourier modal method (FMM) from periodic struct... more This paper extends the area of application of the Fourier modal method (FMM) from periodic structures to aperiodic ones, in particular for plane-wave illumination at arbitrary angles. This is achieved by placing perfectly matched layers at the lateral sides of the computational domain and reformulating the governing equations in terms of a contrast field that does not contain the incoming field. As a result of the reformulation, the homogeneous system of second-order ordinary differential equations from the original FMM becomes nonhomogeneous. Its solution is derived analytically and used in the established FMM framework. The technique is demonstrated on a simple problem of planar scattering of TE-polarized light by a single rectangular line.
Optical Modelling and Design, 2010
This paper extends the area of application of the Fourier modal method from periodic structures t... more This paper extends the area of application of the Fourier modal method from periodic structures to aperiodic ones, in particular for plane-wave illumination at arbitrary angles. This is achieved by placing perfectly matched layers at the lateral sides of the computational domain and reformulating the governing equations in terms of a contrast field which does not contain the incoming field.
The growing release of scientific computational software does not seem to aid the implementation ... more The growing release of scientific computational software does not seem to aid the implementation of complex numerical algorithms. Released libraries lack a common standard interface with regard to for instance finite element, difference or volume discretizations. And, libraries written in standard languages such as FORTRAN or c++ need not even contain the information required for combining different libraries in a safe manner. This paper introduces a small standard interface, to adorn existing libraries with. The interface aims at the -automated -implementation of complex algorithms for numerics and visualization. First, we derive a requirement list for the interface: it must be identical for different libraries and numerical disciplines, support interpreted, compiled and visual programming, must be implemented using standard tools and languages, and adorn libraries in the absence of source code. Next, we show the benefits of its implementation in a mature (visual) programming environment [1], [2] and [3]), where it adorns both public domain and commercial libraries. The last part of this paper describes the interface itself. For an example, the implementational details are worked out.
Optical Engineering, 2011
[Optical Engineering 50, 103201 (2011)]. Maria E. Rudnaya, Robert MM Mattheij, Joseph ML Maubach,... more [Optical Engineering 50, 103201 (2011)]. Maria E. Rudnaya, Robert MM Mattheij, Joseph ML Maubach, Hennie G. ter Morsche. Abstract. ... MTPostek and AEVladar, ???Image sharpness measurement in scanning electron microscopy-Part I,??? Scanning 20, 1???9 (1998). ...
Engineering Fracture Mechanics, 2010
A simultaneous autofocus and two-fold astigmatism correction method for electron microscopy is de... more A simultaneous autofocus and two-fold astigmatism correction method for electron microscopy is described. The method uses derivative-free optimization in order to find a global optimum of an image variance, which is an image quality measure. The Nelder-Mead simplex method and the Powell interpolation-based trust-region method are discussed and compared for an application running on a scanning transmission electron microscope.
Microscopy and Microanalysis, 2011
Most autofocus methods are based on a sharpness function which delivers a real-valued estimate of... more Most autofocus methods are based on a sharpness function which delivers a real-valued estimate of an image quality. In this paper we study an L2−norm gradient-based sharpness function for two-dimensional images (2-D setting). Within this setting we are able to take into account the asymmetry of the optical device objective lens (astigmatism aberration). This study provides a useful extension of the analytical observations for one-dimensional images (1-D setting) that have been done before. The gradient-based autofocus method is implemented and demonstrated for the real-world application running in the FEI scanning transmission electron microscope prototype.
Microscopy and Microanalysis, 2009
Journal of the Optical Society of America A, 2011
The Fourier modal method (FMM) is a method for efficiently solving Maxwell's equations with perio... more The Fourier modal method (FMM) is a method for efficiently solving Maxwell's equations with periodic boundary conditions. In order to apply the FMM to nonperiodic structures, perfectly matched layers need to be placed at the periodic boundaries, and the Maxwell equations have to be formulated in terms of a contrast (scattered) field. This reformulation modifies the structure of the resulting linear systems and makes the direct application of available stable recursion algorithms impossible. We adapt the well-known S-matrix algorithm for use with the aperiodic FMM in contrast-field formulation. To this end, stable recursive relations are derived for linear systems with nonhomogeneous structure. The stability of the algorithm is confirmed by numerical results.
Journal of Microscopy, 2010
Fast and reliable autofocus techniques are an important topic for automated scanning electron mic... more Fast and reliable autofocus techniques are an important topic for automated scanning electron microscopy. In this paper, different autofocus techniques are discussed and applied to a variety of experimental through-focus series of scanning electron microscopy images with different geometries. The procedure of quality evaluation is described, and for a variety of scanning electron microscope samples it is demonstrated that techniques based on image derivatives and Fourier transforms are in general better than statistical, intensity and histogrambased techniques. Further, it is shown that varying of an extra parameter can dramatically increase quality of an autofocus technique.
Journal of Mathematical Imaging and Vision, 2012
Most automatic focusing methods are based on a sharpness function, which delivers a real-valued e... more Most automatic focusing methods are based on a sharpness function, which delivers a real-valued estimate of an image quality. In this paper, we study an L 2-norm derivative-based sharpness function, which has been used before based on heuristic consideration. We give a more solid mathematical foundation for this function and get a better insight into its analytical properties. Moreover an
Journal of Computational Physics, 2012
The aperiodic Fourier modal method in contrast-field formulation is a numerical discretization an... more The aperiodic Fourier modal method in contrast-field formulation is a numerical discretization and solution technique for solving scattering problems in electromagnetics. Typically, spectral discretization is used in the finite periodic direction and spatial discretization in the orthogonal direction. In the light of the fact that the structures of interest often have a large width-to-height ratio and that the two discretization approaches have different computational complexities, we propose exchanging the directions for spatial and spectral discretization. Moreover, if the scatterer has repeating patterns, swapping the discretization directions facilitates the reuse of previous computations. Therefore, the new method is suited for scattering from objects with a finite number of periods, such as gratings, memory arrays, metamaterials, etc. Numerical experiments demonstrate a considerable reduction of the computational costs in terms of time and memory. For a specific test case considered in this paper, the new method (based on alternative discretization) is 40 times faster and requires 100 times less memory than the method based on classical discretization.
Journal of the Optical Society of America A, 2010
This paper extends the area of application of the Fourier modal method (FMM) from periodic struct... more This paper extends the area of application of the Fourier modal method (FMM) from periodic structures to aperiodic ones, in particular for plane-wave illumination at arbitrary angles. This is achieved by placing perfectly matched layers at the lateral sides of the computational domain and reformulating the governing equations in terms of a contrast field that does not contain the incoming field. As a result of the reformulation, the homogeneous system of second-order ordinary differential equations from the original FMM becomes nonhomogeneous. Its solution is derived analytically and used in the established FMM framework. The technique is demonstrated on a simple problem of planar scattering of TE-polarized light by a single rectangular line.
Optical Modelling and Design, 2010
This paper extends the area of application of the Fourier modal method from periodic structures t... more This paper extends the area of application of the Fourier modal method from periodic structures to aperiodic ones, in particular for plane-wave illumination at arbitrary angles. This is achieved by placing perfectly matched layers at the lateral sides of the computational domain and reformulating the governing equations in terms of a contrast field which does not contain the incoming field.
The growing release of scientific computational software does not seem to aid the implementation ... more The growing release of scientific computational software does not seem to aid the implementation of complex numerical algorithms. Released libraries lack a common standard interface with regard to for instance finite element, difference or volume discretizations. And, libraries written in standard languages such as FORTRAN or c++ need not even contain the information required for combining different libraries in a safe manner. This paper introduces a small standard interface, to adorn existing libraries with. The interface aims at the -automated -implementation of complex algorithms for numerics and visualization. First, we derive a requirement list for the interface: it must be identical for different libraries and numerical disciplines, support interpreted, compiled and visual programming, must be implemented using standard tools and languages, and adorn libraries in the absence of source code. Next, we show the benefits of its implementation in a mature (visual) programming environment [1], [2] and [3]), where it adorns both public domain and commercial libraries. The last part of this paper describes the interface itself. For an example, the implementational details are worked out.