Peter Zolliker

Peter Zolliker
Empa - Swiss Federal Laboratories for Materials Science and Technology | Empa · Laboratory for Transport at Nanoscale Interfaces

Dr sc. nat.

About

118
Publications
12,467
Reads
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2,879
Citations
Introduction
Peter Zolliker currently works at the Laboratory for Transport at Nanoscale Interfaces, Empa - Swiss Federal Laboratories for Materials Science and Technology.
Additional affiliations
January 2014 - present
Empa - Swiss Federal Laboratories for Materials Science and Technology
Position
  • Researcher
July 2003 - December 2013
Empa - Swiss Federal Laboratories for Materials Science and Technology
Position
  • Senior Researcher
June 1989 - June 2003
Gretag Imaging / Imaging Solutions
Position
  • R&D Engineer / Scientist

Publications

Publications (118)
Article
The Talbot effect has been revived in many fields of modern optics. As a key number of self-imaging, the fundamental Talbot length plays a crucial role in many applications. However, the inspection of the Talbot carpet for determining the Talbot length is applicable only if the 2D field distribution behind the grating is represented by a 1D cross s...
Article
Full-text available
There is a need for low-cost and easily accessible optical devices for THz applications. THz devices can be manufactured rapidly with 3D printing while using THz transparent materials. In this work, we optimized the parameters for high-resolution 3D printing of a THz transparent filament, cyclic olefin copolymer (TOPAS), in order to 3D print high q...
Conference Paper
Full-text available
We present the optimization of the processing parameters for high-quality 3D printing using cyclic olefin copolymer (TOPAS). These parameters were used for the 3D printing of THz waveguides.
Article
Full-text available
We present a real-time THz imaging method using a commercial fiber-coupled photo conductive antenna as the THz source and an uncooled microbolometer camera for detection. This new combination of state-of-the-art components is very adaptable due to its compact and uncooled radiation source, whose fiber coupling allows for a flexible placement. Using...
Article
Biomimetic, lamellar, and highly porous transition-metal carbide (MXene) embedded cellulose nanofiber (CNF) aerogels are assembled by a facile bidirectional freeze-drying approach. The biopolymer aerogels have large-scale, parallel-oriented micrometer-sized pores and show excellent mechanical strength and flexibility, tunable electrical properties,...
Preprint
Full-text available
We present a real-time THz imaging method using a commercial fiber coupled photo conductive antenna as the THz source and an uncooled microbolometer camera for detection. Compared to other THz imaging setups, this concept is very adaptable due to its compact and uncooled radiation source, whose fiber coupling allows for a flexible placement. Using...
Article
Full-text available
Due to their good electrical and mechanical properties, composites of epoxy and graphene-related materials (GRMs) are applied in sports equipment or gasoline containers. During the use phase, wear and tear may induce the release of composite fragments, which might have different effects on human health than pristine GRMs that have shown to increase...
Article
Full-text available
Imaging with THz radiation has proved an important tool for both fundamental science and industrial use. Here we review a class of THz imaging implementations, named coherent lensless imaging, that reconstruct the coherent response of arbitrary samples with a minimized experimental setup based only on a coherent source and a camera. After discussin...
Article
Air-coupled ultrasound (ACU) is increasingly used for non-destructive testing (NDT). With ACU, no contact or coupling agent (e.g., water, ultrasound gel) is needed between transducers and test sample, which provides high measurement reproducibility. However, for testing in production, a minimum separation is often necessary between sample and trans...
Article
In this paper we demonstrate a non-destructive, non-contact detection method for small defects in thin polymer plates using an air coupled ultrasonic (ACUS) setup. There exist many applications for such methods, e.g. quality control in the manufacturing process or failure prevention by periodical inspections during the lifetime of a product. We dem...
Conference Paper
We present a technique reconstructing the transmission function of a textile and a hidden object. It is demonstrated at terahertz wavelengths, and achieves a lateral resolution of the reconstructed hidden object of about 1.5λ.
Article
Full-text available
Imaging through scattering materials is of utmost importance, especially for security and biomedical imaging. Unlike the rest of the electromagnetic spectrum, terahertz radiation is a non-ionizing probe and allows imaging deep through non-conducting materials with sub-millimeter resolution. Here, we propose a coherent imaging technique reconstructi...
Article
This study reports on the effect of neutron irradiation at different fluences on the properties of VO2 thin films. The irradiations were performed at NUR research reactor, Algiers at a temperature of about 40 °C, with fast neutron fluence (En > 1 MeV) up to 1.9 × 10¹⁸ n.cm⁻². The induced defects have been investigated using structural, optical and...
Article
Ultrasonic, non-contact defect detection for polymer pipes can provide an easy and reliable method to establish on site quality control without destructive mechanical testing and finally may help to prevent damage from leaking pipes. The target is to inspect thin walled polymer pipes made of PVDF and PP with small defects in the pipe wall. Air coup...
Article
Zusammenfassung Bildgebung mit Terahertzstrahlung basiert bislang auf Abscannen eines Objekts mit einem Detektor. Mikrobolometer‐Kameras ermöglichen nun eine Bildgebung wie bei einer normalen Kameratechnik. Das erlaubt auch den Einsatz holografischer Methoden. Bei ausreichend Platz, um einen Referenzstrahl seitlich in die Kamera einzustrahlen, ist...
Conference Paper
Full-text available
We present a study on the resolution limits and resolution factors of terahertz (THz) ptychography. Simulations of a binary amplitude object show that ptychography shares the same intrinsic resolution factors with digital holography, i.e. it is diffraction-limited. Reconstructions of amplitude and phase objects obtained from holographic and ptychog...
Conference Paper
Off-axis digital holography is a powerful tool to measure the phase and amplitude of the wave field diffracted by an object. In THz holography the wavelength is larger than the pixel size of the micro-bolometer detector, allowing large off-axis angles for the reference beam to be applied in the registration of the hologram. The phase field is then...
Article
Full-text available
We realized a phase retrieval technique using terahertz (THz) radiation as an alternative to THz digital hologra-phy, named THz ptychography. Ptychography has been used in x-ray imaging as a groundbreaking improvement of conventional coherent diffraction imaging. Here we show that ptychography can be performed at THz frequencies too. We reconstruct...
Article
Full-text available
Transmission terahertz (THz) spectroscopy on heterogeneous materials often shows structured spectra due to interference of waves passing through the object along different optical paths. Of special interest is wood with its strong birefringence and pronounced orientation-dependent structure. In this paper, we show that at specific polarization angl...
Conference Paper
Full-text available
We report on the first steps towards THz imaging of biomechanical interfaces. A THz digital holography setup in reflection is used with synthetic aperture techniques to reconstruct the profile of a fingertip replica with a lateral resolution of 200 μm and a depth resolution of 20 μm. A method for the reconstruction of the profile of a sample hidden...
Article
Full-text available
We present a method for the separation of the signal scattered from an object hidden behind a THz-transparent sample in the framework of THz digital holography in reflection. It combines three images of different interference patterns to retrieve the amplitude and phase distribution of the object beam. Comparison of simulated with experimental imag...
Article
Full-text available
A terahertz laser, combined with an uncooled microbolometer camera, is used in a digital holography method to provide improved resolution of skin profiles.
Conference Paper
Wood exhibits a strong birefringence at Terahertz frequencies. In this paper we show that at specific polarization angles the THz transmission spectra show distinct frequency gaps. We present results for spruce and beech wood with different sample thickness and orientations. We demonstrate that the main effect can be modeled with appropriate values...
Conference Paper
Full-text available
The profile of a fingertip imprint is reconstructed with a combination of optical fringe projection and THz digital holography. A powerful far-infrared laser and an uncooled microbolometer array detector are used in an off-axis holographic setup in reflection. Holographic reconstructions are obtained through a phase stepping algorithm and a synthet...
Article
Full-text available
In terahertz (THz) materials science, imaging by scanning prevails when low power THz sources are used. However, the application of array detectors operating with high power THz sources is increasingly reported. We compare the imaging properties of four different array detectors that are able to record THz radiation directly. Two micro-bolometer ar...
Conference Paper
We describe a setup for digital Terahertz holography based on a high-power THz gas laser and a high-resolution uncooled micro-bolometer array detector. Amplitude and phase of the diffraction pattern of test objects in transmission is obtained from phase-stepped digital holograms. The object thickness profile is reconstructed using numerical Fourier...
Article
We demonstrate a digital holographic setup for Terahertz imaging of surfaces in reflection. The set-up is based on a high-power continuous wave (CW) THz laser and a high-resolution (640×480 pixel) bolometer detector array. Wave propagation to non-parallel planes is used to reconstruct the object surface that is rotated relative to the detector plan...
Conference Paper
Resolution limits of Terahertz holography are studied using a non-monochromatic THz Quantum Cascade Laser and a micro-bolometer array detector in a beam-splitter free holographic set-up. We discuss the dependence of object reconstruction quality on object distance, detector array, spectral spread, and phase map retrieval using the Fourier transform...
Article
A non-monochromatic THz Quantum Cascade Laser and an uncooled micro-bolometer array detector with VGA resolution are used in a beam-splitter free holographic set-up to measure amplitude and phase objects in transmission. Phase maps of the diffraction pattern are retrieved using the Fourier transform carrier fringe method; while a Fresnel-Kirchhoff...
Article
Full-text available
Rendering materials on displays becomes ubiquitous in industrial design, architecture, and visualization. Yet the experience of the material from other modes of perception is missing in that representation. This forces observers to rely on visual cues only while judging material properties. In the present study, we compare judgments of rough and gl...
Conference Paper
High dynamic range imaging (HDRi) is a technology concerned with representing a range of luminances larger than state of the art displays and closer to luminance ranges occuring in natural scenes. We investigate whether the approach of evaluating a dynamic range by the number of just noticeable differences contained within does make sense in a HDRi...
Article
Color technology needs specifications to which extent physical differences of stimuli correspond to differences in perception. Generalized linear models (GLMs) have proved successful to provide such specifications from choice-based experiments. However, the use of GLMs imposes practical restrictions on the experiment and stimulus parameters. We pro...
Conference Paper
Full-text available
Rendering materials on displays becomes ubiquitous in industrial design, architecture and visualisation. Previous studies measured the influence of disparity, motion and colour on the perception of gloss in renderings [Nishida et Shinya, 1998, Jour. Opt. Soc. Am. A, 12 2951--2965] [Wendt et al., 2010, Journal of Vision 10(9):7 1--17] . Observers p...
Article
Full-text available
Existing image-difference measures show excellent accuracy in predicting distortions, such as lossy compression, noise, and blur. Their performance on certain other distortions could be improved; one example of this is gamut mapping. This is partly because they either do not interpret chromatic information correctly or they ignore it entirely. We p...
Conference Paper
Full-text available
Image similarity describes the quality of an image relative to a reference. Image difference measures are calculated in order to quantify the perceived difference. The concept is also applicable to model where two colour images differ. Existing measures for image similarity focus on high spatial frequency distortions, best visible in the luminance...
Conference Paper
Full-text available
We discuss a few selected hypotheses on how the visual system judges differences of color images. We then derive five image-difference features from these hypotheses and address their relation to the visual processing. Three models are proposed to combine these features for the prediction of perceived image differences. The parameters of the image-...
Conference Paper
Full-text available
We present a corpus of experimental data from psychometric studies on gamut mapping and demonstrate its use to develop image similarity measures. We investigate whether similarity measures based on luminance (SSIM) can be improved when features based on chroma and hue are added. Image similarity measures can be applied to automatically select a goo...
Conference Paper
In this paper we study a local, image dependent approach to the gamut mapping problem. A structural image quality measure is used to pick an optimal mapping algorithm for image patches from a given class of algorithms. The optimally mapped patches are then fused into a single mapping of the image. We discuss and compare two image fusion methods tha...
Conference Paper
Full-text available
We quantify the effects of background on perception of contrast. For this, we compare pairs of colour differences using the method of constant stimuli. The influence of room illumination is quantitatively measured and discussed.
Article
Full-text available
Conjoint analysis is a family of techniques that originated in psychology and later became popular in market research. The main objective of conjoint analysis is to measure an individual's or a population's preferences on a class of options that can be described by parameters and their levels. We consider preference data obtained in choice-based co...
Chapter
Gamut mapping regarded as a color transformation from the color capacity of one device to another has reached a satisfying degree of maturity is discussed. Colorimetry is the branch of color science, which quantifies and describes physically human color perception specifying numerically the colors of physically defined visual stimuli in fixed viewi...
Conference Paper
The use of LCD displays as a test platform for the evaluation for perceived color differences is examined. The setup and verification of an accurate color reproduction workflow is presented. As a first application we compare a monitor based color difference test with a corresponding already existing test based on printed samples. In view of the res...
Article
In this article the authors show that image quality measures can be successfully used to develop image-individualized gamut mapping algorithms. First the authors compare different image quality measures for the gamut mapping problem and then validate them using psychovisual data from four recent gamut mapping studies. The scoring function used to v...
Article
This chapter provides an overview of research on image-dependent gamut mapping. A color gamut includes all colors that can be rendered by a device or are contained in an image. Mapping the colors from one color gamut into another one is called gamut mapping. To understand the objectives and problems of gamut mapping several aspects need to be cover...
Article
We show that conjoint analysis, a popular multi-attribute preference assessment technique used in market research, is a well suited tool to evaluate a multitude of gamut mapping algorithms simultaneously. Our analysis is based on data from psycho-visual tests assessed in a laboratory and in a web environment. Conjoint analysis allows us to quantify...
Conference Paper
Full-text available
In the graphic arts industry, there is a need to convert colorimetric readings taken on one backing (usually white) to values that would have been measured with a different backing (usually black). We describe and compare different models for such a conversion. Starting from published models using linear scaling, we developed a new nonlinear model...
Conference Paper
In this paper we compare different image quality measures for the gamut mapping problem, and validate them using psycho-visual data from four recent gamut mapping studies. The psycho-visual data are choice data of the form: given an original image and two images obtained by applying different gamut mapping algorithms, an observer chooses the one th...
Conference Paper
Full-text available
Conjoint analysis is family of techniques that originated in psychology and later became popular in market research. The main ob- jective of conjoint analysis is to measure an individual's or a population's preferences on a class options that can be described by parameters and their levels. We consider preference data obtained in choice based con-...
Conference Paper
An accurate characterization of the substrate is a prerequisite of color management in print. The use of standard ICC profiles in prepress leaves it to the printer to match the fixed substrate characteristics contained in these profiles. This triggers the interest in methods to predict, if a given ink, press and paper combination complies with a gi...
Article
Full-text available
The measurement of image quality requires the judgement by the human visual system. This paper describes a psycho-visual test technique that uses the internet as a test platform to identify image quality in a more time-effective manner, comparing the visual response data with the results from the same test in a lab-based environment and estimate th...
Article
Full-text available
Professional designers and artists are quite cognizant of the rules that guide the design of effective color palettes, from both aesthetic and attention-guiding points of view. In the field of visualization, however, the use of systematic rules embracing these aspects has received less attention. The situation is further complicated by the fact tha...
Conference Paper
Full-text available
Export Date: 10 April 2012, Source: Scopus
Article
Full-text available
We explore the potential of image-dependent gamut mapping as a constrained optimization problem. The performance of our new approach is compared to standard reference gamut mapping algorithms in psycho-visual tests.
Article
Full-text available
Visualization algorithms can have a large number of parameters, making the space of possible rendering results rather high-dimensional. Only a systematic analysis of the perceived quality can truly reveal the optimal setting for each such parameter. However, an exhaustive search in which all possible parameter permutations are presented to each use...
Article
Full-text available
Our topic is the potential of combining global gamut mapping with spatial methods to retain the percepted local image information in gamut mapping algorithms. The main goal is to recover the original local contrast between neighboring pixels in addition to the usual optimization of preserving lightness, saturation, and global contrast. Special emph...
Conference Paper
This paper deals with the potential of spatial gamut mapping methods as a complement to global gamut mapping algorithms. The main goal is to recover the original local contrast between neighboring pixels in addition to the usual optimization of preserving lightness, saturation and global contrast. As a typical representative for such a spatial mapp...
Article
We treat image-to-device gamut mapping as a multi-criteria optimization problem. Our approach leads to a parameterized mathematical optimization problem that allows to constrain the degree to which objectives like contrast preservation, line preservation, saturation preservation and the continuity of the mapping can be violated while maximizing the...
Article
The design of a gamut mapping algorithm (GMA) is always a compromise between preserving different competing aspects such as color, contrast and lightness. A natural requirement to a GMA is that the algorithmic treatment of this competition has to avoid any additional artefacts such as discontinuities or loss of contrast. In this paper several commo...
Conference Paper
We present a kernel based method to associate an image gamut given as a point cloud in three-dimensional Euclidean space with a continuous shape. The shape we compute is implicitly given as the zero-set of a smooth function that we compute from the point cloud using an efcient optimization method. The feasibility of our approach is demonstrated on...