Orestis Kazasidis

Orestis Kazasidis
Julius Kühn-Institut · Institute for Plant Protection in Horticulture and Forests (Münster)

Dipl.-Ing., Ph.D.

About

17
Publications
1,767
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14
Citations
Introduction
Orestis Kazasidis currently works at the Institute for Plant Protection in Horticulture and Forests of Julius Kühn-Institut Münster.

Publications

Publications (17)
Article
Full-text available
We report interferometric measurements of the temperature coefficient of the refractive index (dn/dT) and the coefficient of thermal expansion (α) of a praseodymium-doped yttrium lithium fluoride (Pr:YLF) crystal and of a fused silica reference sample. Our phase-resolved interferometric method yields a large number of data points and thus allows a...
Article
Full-text available
With a view to the next generation of large space telescopes, we investigate guide-star-free, image-based aberration correction using a unimorph deformable mirror in a plane conjugate to the primary mirror. We designed and built a high-resolution imaging testbed to evaluate control algorithms. In this paper we use an algorithm based on the heuristi...
Article
Image-sharpness metrics can be used to optimize optical systems and to control wavefront sensorless adaptive optics systems. We show that for an aberrated system, the numerical value of an image-sharpness metric can be improved by adding specific aberrations. The optimum amplitudes of the additional aberrations depend on the power spectral density...
Article
We recently presented a novel unimorph deformable mirror which allows for dynamic focus shift with an actuation rate of 2 kHz. Such mirrors suffer from hysteresis and creep. Therefore, they have to be operated in closed-loop. For this purpose, we developed a defocus sensor, based on an astigmatic detection system. In this paper, we present the sens...
Poster
Full-text available
Monitoring the abundance of rodents and the pathogen prevalence is performed by individual scientists, commonly under temporary contracts. Although processed data are shared via scientific conferences and publications, access to the raw data only rarely is an option for other scientists. A centralized database for rodent monitoring could open the w...
Conference Paper
Full-text available
With a view to future large space telescopes, we investigate image-based wavefront correction with active optics. We use an image-sharpness metric as merit function to evaluate the image quality, and the Zernike modes as control variables. In severely aberrated systems, the Zernike modes are not orthogonal to each other with respect to this merit f...
Poster
Full-text available
With a view to future large space telescopes, we investigate image-based wavefront correction with active optics. We use an image-sharpness metric as merit function to evaluate the image quality, and the Zernike modes as control variables. In severely aberrated systems, the Zernike modes are not orthogonal to each other with respect to this merit f...
Poster
Full-text available
A surface's haptic and optical characteristics are taking on an increasingly important role for the overall surface quality and functionality. For example, the interior fittings of a car are usually made of plastics, whose surfaces are designed to mimic natural materials or artificial patterns. Many optical and haptic properties are determined by t...
Conference Paper
Fast adaptive optics requires wavefront sensing to operate in closed-loop. Slower active optics correcting for static or quasi-static aberrations can use an image-sharpening metric to close the loop. A control algorithm will iteratively adapt the surface of the corrective element to maximize this metric. The performance of image-based active optics...
Conference Paper
Active optics is an enabling technology for future large space telescopes. A deformable mirror placed in a plane conjugate to the large primary mirror could correct for its surface errors. This would relax the requirements for the surface fidelity of the primary mirror and would allow for a larger aperture with increased resolution and sensitivity,...
Conference Paper
Exact values of the temperature coefficient of the refractive index (dn/dT) and the coefficient of thermal expansion (α) are necessary in order to calculate thermal lensing and design new concepts of solid state lasers. We have developed an interferometric method to measure simultaneously both coefficients of a laser crystal as a function of temper...
Thesis
An innovative interferometric method has been designed by the Photonics Laboratory of Münster University of Applied Sciences to measure thermo-optical properties of laser crystals. The method is able not only to provide accurate results concerning the thermal expansion coefficient and the thermo-optical coefficient of refractive index change (dn/dT...
Conference Paper
Full-text available
The paper presents the numerical evaluation of the electroencephalogram (EEG) electrode artifacts that are caused during exposure to electromagnetic fields (EMF), in volunteers study. The scope of the study is to differentially present the electromagnetic (EM) power absorption and local Specific Absorption Rate (SAR) distribution, with and without...
Thesis
This diploma thesis is part of the research work of the Biomedical Simulations and Imaging (BIOSIM) Unit of National Technical University of Athens (NTUA) aiming at the assessment of possible alternation in electroencephalogram (EEG) and event related potentials recordings during acoustic stimuli, due to exposure to electromagnetic signal with thir...

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Projects

Projects (2)
Archived project
We present an interferometric method to measure the temperature co- efficient of the refractive index and the coefficient of thermal expansion of laser crystals as a function of temperature in the interval from 20 ◦ C to 80 ◦ C.
Archived project
Investigate of optimal control methods for image-based control of a deformable mirror with hysteresis