Ion-assisted deposition is suitable for the formation of epitaxial Si films at high deposition ra... more Ion-assisted deposition is suitable for the formation of epitaxial Si films at high deposition rate and low substrate temperature. We demonstrate epitaxial deposition of Si films on (100)-oriented Si wafers using deposition rates up to 0.3 μm/min at deposition temperatures in the range of 500–650 °C. Hall-effect measurements show a majority carrier mobility of 200 cm2/V s at a hole concentration of 1.4×1017 cm−3 in our films. A minority carrier diffusion length of 4.5 μm is determined from quantum efficiency measurements in the epitaxially grown Si films.
Optical metrology techniques such as fringe projection technology and phase-measuring deflectomet... more Optical metrology techniques such as fringe projection technology and phase-measuring deflectometry, which use cameras as image sensors for 3D coordinate measurement and inspection, are becoming increasingly demanding. The necessary precise and at the same time robust calibration of image sensors of these systems is offered by so called vision ray calibration. This generic approach is a model-free description of a vision ray and are determined for each imaging sensor pixel. Numerous images of the sinusoidal fringe images displayed on the active calibration target (LCD) are captured in different poses. This generates a large amount of data and consequently leads to time-consuming evaluation for the camera calibration. In this paper, we propose a new optimization method that uses “vision threads" instead of vision rays to enhance the computation efficiency associated with conventional vision ray calibration. We present MATLAB simulation results in to validate our novel approach.
Digital Holography and Three-Dimensional Imaging 2019, 2019
We present an experimental configuration for phase retrieval utilizing fast object’s depth scanni... more We present an experimental configuration for phase retrieval utilizing fast object’s depth scanning. The configuration is composesed of a digital micro-mirror device enabling fast manipulation of light-fields with binarized holograms of the transfer-function of propagation.
A method for manufacturing a crystalline semiconductor layer (26) is that on the surface of a sem... more A method for manufacturing a crystalline semiconductor layer (26) is that on the surface of a semiconductor substrate (20; 30) at least one porous layer (21; 31) is generated, the porous layer is peeled off from the semiconductor substrate and either before or after detachment is recrystallized by thermal annealing at least partially.
We present polymer-based holograms with varying structure angle for each individual micrometer-si... more We present polymer-based holograms with varying structure angle for each individual micrometer-sized pixel. The holograms are numerically calculated utilizing an iterative optimization procedure including a first-order Taylor series expansion to determine the slope of each pixel. The holograms are fabricated by 3D laser lithography. Due to the small pixel sizes and the individual slope of each pixel aliases can be avoided and the overall intensity of the desired projection is strongly increased compared to holograms consisting of larger and uniform pixels. Furthermore, the discrepancy between calculated and measured intensity distribution is strongly reduced.
We present a method for fast inspection of metallic micro parts. It is based on the combination o... more We present a method for fast inspection of metallic micro parts. It is based on the combination of twowavelength contouring and digital holographic microscopy (DHM). For fast evaluation, an autofocus algorithm to refocus the object digitally without the need for any external intervention is proposed. The method enhances the microscope objective’s depth of focus compared with imaging techniques by standard microscopy. Compared to standard DHM, an object side telecentric objective is utilized to overcome irreversible depth distortions caused by standard microscope objectives. The method is demonstrated by reconstructing the three-dimensional shape of a metallic deep drawn micro cup. Experimental results confirm the improved depth of focus of DHM.
2018 17th Workshop on Information Optics (WIO), 2018
Diffractive optical elements (DOE) are widely used for the projection of desired intensity distri... more Diffractive optical elements (DOE) are widely used for the projection of desired intensity distributions, e.g. in security or automotive applications. Diamond turning based on a nano Fast Tool Servo offers short fabrication times and low costs for small quantities. The main properties of diamond turned metal DOEs for the holographic projection are their small pixel size down to 1 μm in feed direction, high reflectivity and mechanical and thermal stability. Currently, existing methods are limited to the projection of intensity distributions in only one plane. However, more than one projection plane is highly desirable for applications as automotive lighting, laser material processing and security features. In this contribution, we introduce an approach for the optical design of diamond turned holograms (DTH) for the holographic projection of arbitrary intensity distributions in multiple reconstruction planes in the Fresnel domain. The design problem is related to the spiral path of the diamond cutting tool and to find a set of N wavefields which generate intensity distributions in different distances dn. For calculating the cutting depth profile of the DTH a combination of the Gerchberg-Saxton-Algorithm with an iterative phase retrieval algorithm is applied. The use of Fresnel propagation in the algorithm allows the generation of intensity distributions in large projection areas with low computational effort. We present the theory as well as the experimental verification of this new approach.
Multiple Aperture Shear-Interferometry (MArS) is a shape measurement technique that uses multi-sp... more Multiple Aperture Shear-Interferometry (MArS) is a shape measurement technique that uses multi-spot illumination to overcome the problem of a limited observation aperture of conventional interferometric techniques and thus considerably simplifies the measurement of optical aspheres and freeform surfaces. Using a shear interferometry setup, MArS measures the coherence function in order to obtain wave vector distributions created from multi-spot LED illumination reflected by the specimen. Based on the wave vectors we reconstruct the surface topography of aspheric lenses using an inverse ray tracing approach and prior knowledge about the individual source locations. We present the topographic measurement of two aspheric lenses with different global curvature radii measured with the same identical reflection setup. In addition, we examine the achievable accuracy of the wave vector measurement using a single light source to find physical limits of MArS.
We present a novel approach of phase retrieval using a 4 f-imaging system, for the specific case ... more We present a novel approach of phase retrieval using a 4 f-imaging system, for the specific case of spatially partially coherent illumination. The theoretical investigation presented in Part I is based on scalar diffraction theory in combination with a heuristic approach. We find that the intensity of the de-focused speckle fields across the image plane shows sufficient contrast for phase retrieval, as long as the radius of the point spread function of the imaging system is well below the radius of the correlation area (spatial coherence) in the object plane. We also derive a useful relation, which allows to determine the requirements towards the essential parameters of an experimental setup, such as maximum propagation distance, diameter of the source, illumination distance and the numerical aperture of the imaging system. The consecutive paper, Part II, describes shape measurement based on the present treatise.
Proceedings, annual meeting, Electron Microscopy Society of America, 1990
Defect-free silicon layers grown on insulators (SOI) are an essential component for future three-... more Defect-free silicon layers grown on insulators (SOI) are an essential component for future three-dimensional integration of semiconductor devices. Liquid phase epitaxy (LPE) has proved to be a powerful technique to grow high quality SOI structures for devices and for basic physical research. Electron microscopy is indispensable for the development of the growth technique and reveals many interesting structural properties of these materials. Transmission and scanning electron microscopy can be applied to study growth mechanisms, structural defects, and the morphology of Si and SOI layers grown from metallic solutions of various compositions.The treatment of the Si substrates prior to the epitaxial growth described here is wet chemical etching and plasma etching with NF3 ions. At a sample temperature of 20°C the ion etched surface appeared rough (Fig. 1). Plasma etching at a sample temperature of −125°C, however, yields smooth and clean Si surfaces, and, in addition, high anisotropy (...
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
We present a method for fast geometrical inspection of micro deep drawing parts. It is based on s... more We present a method for fast geometrical inspection of micro deep drawing parts. It is based on single-shot two-wavelength contouring digital holographic microscopy (DHM). Within the capturing process, spatial multiplexing is utilized in order to record the two required holograms in a single-shot. For fast evaluation, determining the locations where the object is in focus and stitching all focus object's areas together is achieved digitally without the need for any external intervention using an autofocus algorithm. Thus, the limited depth of focus of the microscope objective is improved. The autofocus algorithm is based on minimizing the total variation (TV) of phase difference residuals of the two-wavelength measurements. In contrast to standard DHM, an object side telecentric microscope objective is used for overcoming the image scaling distortions caused by a conventional microscope objective. The method is used to reconstruct the 3D geometrical shape of a cold drawing micro cup. Experimental results verify the improvement of DHM's depth of focus.
We present a new method for the form measurement of optical surfaces using the spatial coherence ... more We present a new method for the form measurement of optical surfaces using the spatial coherence function, which enables a shearing interferometer in combination with an LED multispot illumination to function as a measurement device. A new evaluation approach connects the measured data with the surface form by inverse raytracing. First measurement results with the inverse evaluation procedures are shown. We present the whole measurement in combination with the evaluation procedure. In addition, the convergence and stability of the implemented optimization task is investigated.
Additive manufacturing that allows layer by layer shaping of complex structures is of rapidly inc... more Additive manufacturing that allows layer by layer shaping of complex structures is of rapidly increasing interest in production technology. A particularly rapid prototyping technique of additive manufacturing is laser beam melting (LBM). This 3D printing method is based on a powder bed fusion technique, using a high-powered laser to melt and consolidate metallic powders. The process needs a tightly controlled atmosphere of inert gas, which requires a confined space of a building chamber. This and more process related factors like elevated temperatures, laser radiation or the resulting light intensity caused by the melting of metals, make a closed-loop quality control very ambitious. In this paper, we propose a new in-process approach for quality control with high precision metrology based on structured light. The precise layer by layer dimensional measurement of both the printed part and the powder deposition, allows for process assessment in-or off-line.
Abstract. We present an experimental configuration that enables form measurement from a single-sh... more Abstract. We present an experimental configuration that enables form measurement from a single-shot camera exposure. It combines two-wavelength contouring with spatial multiplexing digital holography. This is achieved by simultaneously illuminating the test object from two different angles. The two illumination directions and the two-wavelength contouring result in four holograms, which are spatially multiplexed on a single camera target avoiding unwanted cross interference between them by means of coherence gating. In contrast to standard holographic contouring methods, the proposed technique reduces speckle decorrelation noise and enables single-shot form measurement. To demonstrate this technique, the shape of a microcold drawing part is determined.
Journal of the European Optical Society: Rapid Publications, 2014
Generic camera calibration is a method to characterize vision sensors by describing a line of sig... more Generic camera calibration is a method to characterize vision sensors by describing a line of sight for every single pixel. This procedure frees the calibration process from the restriction to pinhole-like optics that arises in the common photogrammetric camera models. Generic camera calibration also enables the calibration of high-frequency distortions, which is beneficial for high-precision measurement systems. The calibration process is as follows: To collect sufficient data for calculating a line of sight for each pixel, active grids are used as calibration reference rather than static markers such as corners of chessboard patterns. A common implementation of active grids are sinusoidal fringes presented on a flat TFT display. So far, the displays have always been treated as ideally flat. In this work we propose new and more sophisticated models to account for additional properties of the active grid display: The refraction of light in the glass cover is taken into account as well as a possible deviation of the top surface from absolute flatness. To examine the effectiveness of the new models, an example fringe projection measurement system is characterized with the resulting calibration methods and with the original generic camera calibration. Evaluating measurements using the different calibration methods shows that the extended display model substantially improves the uncertainty of the measurement system.
In this publication, we demonstrate that recording the mutual intensity, instead of a wavefront, ... more In this publication, we demonstrate that recording the mutual intensity, instead of a wavefront, enables interferometric measurements with multiple independent light sources at the same time. This scheme can, for example, be used to overcome the problem of a limited acceptance angle of imaging systems in interferometry. We further show that, for a finite number of light sources, measuring a subspace of the mutual intensity equals the recording of the corresponding light field, which is sparse in phase space. This recording modality offers more flexibility with respect to the trade-off between angular multiplexing and spatial resolution than the state of the art, because it is not restricted by the geometric properties of a microlens array, but rather allows arbitrary sampling of the light field.
We present a new method for the generation of a dynamic wave field with high space bandwidth prod... more We present a new method for the generation of a dynamic wave field with high space bandwidth product (SBP). The dynamic wave field is generated from several wave fields diffracted by a display which comprises multiple spatial light modulators (SLMs) each having a comparably low SBP. In contrast to similar approaches in stereoscopy, we describe how the independently generated wave fields can be coherently superposed. A major benefit of the scheme is that the display system may be extended to provide an even larger display. A compact experimental configuration which is composed of four phase-only SLMs to realize the coherent combination of independent wave fields is presented. Effects of important technical parameters of the display system on the wave field generated across the observation plane are investigated. These effects include, e.g., the tilt of the individual SLM and the gap between the active areas of multiple SLMs. As an example of application, holographic reconstruction of a 3D object with parallax effects is demonstrated.
We demonstrate a digital holographic system for fast and precise qualityinspection of the interio... more We demonstrate a digital holographic system for fast and precise qualityinspection of the interior of micro deep drawing parts using Two-Wavelength-Contouring.
Ion-assisted deposition is suitable for the formation of epitaxial Si films at high deposition ra... more Ion-assisted deposition is suitable for the formation of epitaxial Si films at high deposition rate and low substrate temperature. We demonstrate epitaxial deposition of Si films on (100)-oriented Si wafers using deposition rates up to 0.3 μm/min at deposition temperatures in the range of 500–650 °C. Hall-effect measurements show a majority carrier mobility of 200 cm2/V s at a hole concentration of 1.4×1017 cm−3 in our films. A minority carrier diffusion length of 4.5 μm is determined from quantum efficiency measurements in the epitaxially grown Si films.
Optical metrology techniques such as fringe projection technology and phase-measuring deflectomet... more Optical metrology techniques such as fringe projection technology and phase-measuring deflectometry, which use cameras as image sensors for 3D coordinate measurement and inspection, are becoming increasingly demanding. The necessary precise and at the same time robust calibration of image sensors of these systems is offered by so called vision ray calibration. This generic approach is a model-free description of a vision ray and are determined for each imaging sensor pixel. Numerous images of the sinusoidal fringe images displayed on the active calibration target (LCD) are captured in different poses. This generates a large amount of data and consequently leads to time-consuming evaluation for the camera calibration. In this paper, we propose a new optimization method that uses “vision threads" instead of vision rays to enhance the computation efficiency associated with conventional vision ray calibration. We present MATLAB simulation results in to validate our novel approach.
Digital Holography and Three-Dimensional Imaging 2019, 2019
We present an experimental configuration for phase retrieval utilizing fast object’s depth scanni... more We present an experimental configuration for phase retrieval utilizing fast object’s depth scanning. The configuration is composesed of a digital micro-mirror device enabling fast manipulation of light-fields with binarized holograms of the transfer-function of propagation.
A method for manufacturing a crystalline semiconductor layer (26) is that on the surface of a sem... more A method for manufacturing a crystalline semiconductor layer (26) is that on the surface of a semiconductor substrate (20; 30) at least one porous layer (21; 31) is generated, the porous layer is peeled off from the semiconductor substrate and either before or after detachment is recrystallized by thermal annealing at least partially.
We present polymer-based holograms with varying structure angle for each individual micrometer-si... more We present polymer-based holograms with varying structure angle for each individual micrometer-sized pixel. The holograms are numerically calculated utilizing an iterative optimization procedure including a first-order Taylor series expansion to determine the slope of each pixel. The holograms are fabricated by 3D laser lithography. Due to the small pixel sizes and the individual slope of each pixel aliases can be avoided and the overall intensity of the desired projection is strongly increased compared to holograms consisting of larger and uniform pixels. Furthermore, the discrepancy between calculated and measured intensity distribution is strongly reduced.
We present a method for fast inspection of metallic micro parts. It is based on the combination o... more We present a method for fast inspection of metallic micro parts. It is based on the combination of twowavelength contouring and digital holographic microscopy (DHM). For fast evaluation, an autofocus algorithm to refocus the object digitally without the need for any external intervention is proposed. The method enhances the microscope objective’s depth of focus compared with imaging techniques by standard microscopy. Compared to standard DHM, an object side telecentric objective is utilized to overcome irreversible depth distortions caused by standard microscope objectives. The method is demonstrated by reconstructing the three-dimensional shape of a metallic deep drawn micro cup. Experimental results confirm the improved depth of focus of DHM.
2018 17th Workshop on Information Optics (WIO), 2018
Diffractive optical elements (DOE) are widely used for the projection of desired intensity distri... more Diffractive optical elements (DOE) are widely used for the projection of desired intensity distributions, e.g. in security or automotive applications. Diamond turning based on a nano Fast Tool Servo offers short fabrication times and low costs for small quantities. The main properties of diamond turned metal DOEs for the holographic projection are their small pixel size down to 1 μm in feed direction, high reflectivity and mechanical and thermal stability. Currently, existing methods are limited to the projection of intensity distributions in only one plane. However, more than one projection plane is highly desirable for applications as automotive lighting, laser material processing and security features. In this contribution, we introduce an approach for the optical design of diamond turned holograms (DTH) for the holographic projection of arbitrary intensity distributions in multiple reconstruction planes in the Fresnel domain. The design problem is related to the spiral path of the diamond cutting tool and to find a set of N wavefields which generate intensity distributions in different distances dn. For calculating the cutting depth profile of the DTH a combination of the Gerchberg-Saxton-Algorithm with an iterative phase retrieval algorithm is applied. The use of Fresnel propagation in the algorithm allows the generation of intensity distributions in large projection areas with low computational effort. We present the theory as well as the experimental verification of this new approach.
Multiple Aperture Shear-Interferometry (MArS) is a shape measurement technique that uses multi-sp... more Multiple Aperture Shear-Interferometry (MArS) is a shape measurement technique that uses multi-spot illumination to overcome the problem of a limited observation aperture of conventional interferometric techniques and thus considerably simplifies the measurement of optical aspheres and freeform surfaces. Using a shear interferometry setup, MArS measures the coherence function in order to obtain wave vector distributions created from multi-spot LED illumination reflected by the specimen. Based on the wave vectors we reconstruct the surface topography of aspheric lenses using an inverse ray tracing approach and prior knowledge about the individual source locations. We present the topographic measurement of two aspheric lenses with different global curvature radii measured with the same identical reflection setup. In addition, we examine the achievable accuracy of the wave vector measurement using a single light source to find physical limits of MArS.
We present a novel approach of phase retrieval using a 4 f-imaging system, for the specific case ... more We present a novel approach of phase retrieval using a 4 f-imaging system, for the specific case of spatially partially coherent illumination. The theoretical investigation presented in Part I is based on scalar diffraction theory in combination with a heuristic approach. We find that the intensity of the de-focused speckle fields across the image plane shows sufficient contrast for phase retrieval, as long as the radius of the point spread function of the imaging system is well below the radius of the correlation area (spatial coherence) in the object plane. We also derive a useful relation, which allows to determine the requirements towards the essential parameters of an experimental setup, such as maximum propagation distance, diameter of the source, illumination distance and the numerical aperture of the imaging system. The consecutive paper, Part II, describes shape measurement based on the present treatise.
Proceedings, annual meeting, Electron Microscopy Society of America, 1990
Defect-free silicon layers grown on insulators (SOI) are an essential component for future three-... more Defect-free silicon layers grown on insulators (SOI) are an essential component for future three-dimensional integration of semiconductor devices. Liquid phase epitaxy (LPE) has proved to be a powerful technique to grow high quality SOI structures for devices and for basic physical research. Electron microscopy is indispensable for the development of the growth technique and reveals many interesting structural properties of these materials. Transmission and scanning electron microscopy can be applied to study growth mechanisms, structural defects, and the morphology of Si and SOI layers grown from metallic solutions of various compositions.The treatment of the Si substrates prior to the epitaxial growth described here is wet chemical etching and plasma etching with NF3 ions. At a sample temperature of 20°C the ion etched surface appeared rough (Fig. 1). Plasma etching at a sample temperature of −125°C, however, yields smooth and clean Si surfaces, and, in addition, high anisotropy (...
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
We present a method for fast geometrical inspection of micro deep drawing parts. It is based on s... more We present a method for fast geometrical inspection of micro deep drawing parts. It is based on single-shot two-wavelength contouring digital holographic microscopy (DHM). Within the capturing process, spatial multiplexing is utilized in order to record the two required holograms in a single-shot. For fast evaluation, determining the locations where the object is in focus and stitching all focus object's areas together is achieved digitally without the need for any external intervention using an autofocus algorithm. Thus, the limited depth of focus of the microscope objective is improved. The autofocus algorithm is based on minimizing the total variation (TV) of phase difference residuals of the two-wavelength measurements. In contrast to standard DHM, an object side telecentric microscope objective is used for overcoming the image scaling distortions caused by a conventional microscope objective. The method is used to reconstruct the 3D geometrical shape of a cold drawing micro cup. Experimental results verify the improvement of DHM's depth of focus.
We present a new method for the form measurement of optical surfaces using the spatial coherence ... more We present a new method for the form measurement of optical surfaces using the spatial coherence function, which enables a shearing interferometer in combination with an LED multispot illumination to function as a measurement device. A new evaluation approach connects the measured data with the surface form by inverse raytracing. First measurement results with the inverse evaluation procedures are shown. We present the whole measurement in combination with the evaluation procedure. In addition, the convergence and stability of the implemented optimization task is investigated.
Additive manufacturing that allows layer by layer shaping of complex structures is of rapidly inc... more Additive manufacturing that allows layer by layer shaping of complex structures is of rapidly increasing interest in production technology. A particularly rapid prototyping technique of additive manufacturing is laser beam melting (LBM). This 3D printing method is based on a powder bed fusion technique, using a high-powered laser to melt and consolidate metallic powders. The process needs a tightly controlled atmosphere of inert gas, which requires a confined space of a building chamber. This and more process related factors like elevated temperatures, laser radiation or the resulting light intensity caused by the melting of metals, make a closed-loop quality control very ambitious. In this paper, we propose a new in-process approach for quality control with high precision metrology based on structured light. The precise layer by layer dimensional measurement of both the printed part and the powder deposition, allows for process assessment in-or off-line.
Abstract. We present an experimental configuration that enables form measurement from a single-sh... more Abstract. We present an experimental configuration that enables form measurement from a single-shot camera exposure. It combines two-wavelength contouring with spatial multiplexing digital holography. This is achieved by simultaneously illuminating the test object from two different angles. The two illumination directions and the two-wavelength contouring result in four holograms, which are spatially multiplexed on a single camera target avoiding unwanted cross interference between them by means of coherence gating. In contrast to standard holographic contouring methods, the proposed technique reduces speckle decorrelation noise and enables single-shot form measurement. To demonstrate this technique, the shape of a microcold drawing part is determined.
Journal of the European Optical Society: Rapid Publications, 2014
Generic camera calibration is a method to characterize vision sensors by describing a line of sig... more Generic camera calibration is a method to characterize vision sensors by describing a line of sight for every single pixel. This procedure frees the calibration process from the restriction to pinhole-like optics that arises in the common photogrammetric camera models. Generic camera calibration also enables the calibration of high-frequency distortions, which is beneficial for high-precision measurement systems. The calibration process is as follows: To collect sufficient data for calculating a line of sight for each pixel, active grids are used as calibration reference rather than static markers such as corners of chessboard patterns. A common implementation of active grids are sinusoidal fringes presented on a flat TFT display. So far, the displays have always been treated as ideally flat. In this work we propose new and more sophisticated models to account for additional properties of the active grid display: The refraction of light in the glass cover is taken into account as well as a possible deviation of the top surface from absolute flatness. To examine the effectiveness of the new models, an example fringe projection measurement system is characterized with the resulting calibration methods and with the original generic camera calibration. Evaluating measurements using the different calibration methods shows that the extended display model substantially improves the uncertainty of the measurement system.
In this publication, we demonstrate that recording the mutual intensity, instead of a wavefront, ... more In this publication, we demonstrate that recording the mutual intensity, instead of a wavefront, enables interferometric measurements with multiple independent light sources at the same time. This scheme can, for example, be used to overcome the problem of a limited acceptance angle of imaging systems in interferometry. We further show that, for a finite number of light sources, measuring a subspace of the mutual intensity equals the recording of the corresponding light field, which is sparse in phase space. This recording modality offers more flexibility with respect to the trade-off between angular multiplexing and spatial resolution than the state of the art, because it is not restricted by the geometric properties of a microlens array, but rather allows arbitrary sampling of the light field.
We present a new method for the generation of a dynamic wave field with high space bandwidth prod... more We present a new method for the generation of a dynamic wave field with high space bandwidth product (SBP). The dynamic wave field is generated from several wave fields diffracted by a display which comprises multiple spatial light modulators (SLMs) each having a comparably low SBP. In contrast to similar approaches in stereoscopy, we describe how the independently generated wave fields can be coherently superposed. A major benefit of the scheme is that the display system may be extended to provide an even larger display. A compact experimental configuration which is composed of four phase-only SLMs to realize the coherent combination of independent wave fields is presented. Effects of important technical parameters of the display system on the wave field generated across the observation plane are investigated. These effects include, e.g., the tilt of the individual SLM and the gap between the active areas of multiple SLMs. As an example of application, holographic reconstruction of a 3D object with parallax effects is demonstrated.
We demonstrate a digital holographic system for fast and precise qualityinspection of the interio... more We demonstrate a digital holographic system for fast and precise qualityinspection of the interior of micro deep drawing parts using Two-Wavelength-Contouring.
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Papers by Ralf Bergmann