Measurement of the optical intensity distribution at the far field

Tato diplomová práce se zabývá energetickým proměřováním optického svazku ve vzdá-lené zóně. Objasněny jsou veličiny: optická intenzita a optický výkon. V práci je diskutováno řešení vlnové rovnice. Popsány jsou rovinná vlna, sférická vlna a Gaussův svazek. Práce ob-sahuje popis jevů, které nastávají na celé trasy laserového svazku, od vysílací laserové diody po přijímací fotodiodu PIN. Jedním z řešených problémů je difrakce na objímce čočky. Byla sestavena základní aparatura pro prozkoumání jevu difrakce, v níž byla použita vysílací dioda, clonka s kruhovými otvory a detektor. V závěrečné části se práce zabývá problematikou de-tekce výkonu v optickém svazku. Rozebrány jsou jednotlivé druhy fotodiod a uvedeny jsou jejich základní charakteristiky.The topic of this master’s thesis is energy measurement of the optical intensity distribu-tion at the far field. Properties of the optical intensity and the optical power are described. In this thesis solution of wave equation is done. The plane wave, spherical wave and Gaussian beam are described. In this thesis, optical trace of laser beam from transmitter laser diode to receiver PIN photodiode is described. One of the solved problems is diffraction on the lens socket. The basic configuration for diffraction investigation on lens socket was created. There were transmitting laser diode, stop with circular apertures and PIN photodiode used in the experiment. In the other part, thesis deals with measuring and detection of the optical beam. Sorts of photodiodes and their characteristics were analysed.

Effect of selected luminescent layers on CCT, CRI, and response times

Phosphors have been used as wavelength converters in illumination for many years. When it is excited with blue light, the frequently used yttrium aluminium garnet doped with cerium (YAG:Ce) phosphor converts a part of blue light to a wideband yellow light, resulting in the generated light having a white color. By combining an appropriate concentration of the YAG:Ce phosphor and blue excitant light, white light of a desired correlated color temperature (CCT) can be obtained. However, this type of illumination has a lower color rendering index value (CRI). In an attempt to improve the CRI value, we mixed the YAG:Ce phosphor with europium-doped calcium sulfide phosphor (CaS:Eu), which resulted in a considerably increased CRI value. This article examines an experiment with luminescent layers consisting of a mixture of selected phosphors and polydimethylsiloxane (PDMS). Different thicknesses in these layers were achieved by changing the speed of rotation during their accumulation onto laboratory glass using the method of spin coating. The spectral characteristics of these luminescent layers as they were excited with blue light emitting diode (LED) and laser diode (LD) were then determined. A suitable combination of the YAG:Ce phosphor with a phosphor containing europium, as it was excited with a blue LED, yielded a source of white light with a CRI value of greater than 85. The response time in the tested luminescent layers to a rectangular excitant impulse (generated by a signal generator and transmitted by LD) was also measured in order to examine their potential use in visible light communications (VLC).Web of Science1213art. no. 209

Výzkum zářivých zdrojů pro současné působení v optických komunikacích a osvětlování

Import 19/05/2014Tato dizertační práce se zabývá optickým vysílačem pro vnitřní optické bezvláknové sítě, jenž může poskytovat komunikaci a osvětlování zároveň. Optický vysílač má nově a origiálně řešenou spektrální charakteristiku vyzařovaného světla. Základem vysílače je bílé světlo, které slouží k osvětlování. Úzká spektrální část tohoto bílého světla je záměrně potlačena optickým filtrem. Potlačená část bílého světla je nahrazena světlem z jiného zářivého zdroje a vytváří původní bílé světlo. Náhradní zářivý zdroj bude modulován a bude tím vysílat užitečná data, čímž bude zajištěna také druhá funkce vysílače, tj. funkce komunikační. Na datovém přenosuse tedy bude podílet pouze část spektra bílého světla. Díky tomuto řešení budou odstraněny nedostatky komunikace bílým světlem. Mezi ně patří rychlé spínání vysokého napájecího proudu v řádech stovek mA a setrvačnost fosforu při vytváření bílého světla. Práce řeší jak spektrální, tak geometrické uspořádání zářivých zdrojů. Výsledkem jsou dvě konstrukční řešení optického vysílače. Tato řešení byla nejdříve simulována v programu LightTools. Poté byly optické vysílače zkonstruovány v laboratoři a byly proměřeny jejich vlastnosti. Obě dvě řešení optického vysílače mohou současně poskytovat obě požadované funkce, což bylo cílem dizertační práce.This dissertation thesis deals with an optical transmitter for indoor free space optical networks, which can provide communication and illumination at the same time. The optical transmitter has a new and original solution of spectral characteristics of the emitted light. The basis of the transmitter is white light, which provides illumination. A narrow spectral part of this white light is purposely suppressed by an optical filter. The suppressed spectral part is then replaced by light from another radiant source and it forms the original white light. The compensatory radiant source will be modulated and due to this it will transmit some useful data. This solution will also provide the other function of the transmitter, i.e. the communication function. The data will be transmitted by one part of the white light spectrum only. Thanks to this solution the disadvantages of the visible light communication will be removed. They include quick switching of the forward current in orders of hundreds of mA and the phosphor persistence on white light creation. The thesis solves the spectral and the geometrical arrangement of the radiant sources. The results are two designs of the optical transmitter. These designs were first tested in LightTools software. The optical transmitters were then constructed in a laboratory and their features were measured. Both designs of the optical transmitter can provide both required functions at the same time, which was the objective of the dissertation thesis.Prezenční440 - Katedra telekomunikační technikyvyhově

Design, simulation and testing of the OOK NRZ modulation format for free space optic communication in a simulation box

This article deals with the construction of a modulator and demodulator for Free-Space Optical (FSO) communication. In FSO optics, the modulated optical signal is propagated in the constantly changing environment (atmosphere). The optical signal is strongly influenced by the actual composition of air, which is directly linked to the change in refractive index in the turbulent cells. This article examines primarily the appropriate modulation format for FSO. For this purpose, one type of an OOK-NRZ modulator and one type of a demodulator were designed. This article also describes the construction of two types of photo detectors (the high impedance and the transimpedance ones). All electronic constructions were tested in the MicroCap simulator and they were experimentally measured as well. For the OOK NRZ modulation the, maximum transmission speed achieved the value of 160~Mbps. Measuring the quality of the modulation formats was carried out under mechanical and thermal turbulences. The last part of this work gives the results of the measurements of fog influences

Restoration of optical spectrum

This article deals with research of luminous sources which could be applied in indoor Free Space Optic (FSO) networks. Indoor FSO networks have potential to replace standard IEEE 802.11 in the future. Suitable selection and configuration of optical radiation sources can at the same time provide communication and lighting in indoor spaces. This article is engaged in spectral mergence of optical sources, willful suppression of part of emitted visible spectrum and consequential restoration of this optical spectrum

Simple and universal current modulator circuit for indoor mobile free-space-optical communications testing

The use of LED for illumination and communication together is more and more interesting with the increasing deployment of LEDs to our homes and industrial buildings. Modulation of this kind of light sources is difficult because of high voltage and current demands. Since the LED configurations and values of current and voltage are different, our universal modulator has to be able to operate even under these circumstances. This paper proposes simple and universal current modulator for LED lighting modulation for frequencies around 1MHz. Main objective is to allow initial testing of different types of High Power LEDs and different photodetector configurations and circuits in diffusive based Free-Space-Optical networks. In the experimental part we also compare results for some different types of LED light sources

VLC transmitter with plastic optical fibers for indoor free space optic networks

This article deals with the construction design of optical transmitter for indoor Free Space Optic (FSO) networks. This optical transmitter will be able to provide the lighting and communication at the same time. Thanks to special solution in spectral characteristic of transmitted light it is necessary to use two LEDs radiation sources. The light beams of these LEDs have to be spatially overlapped in crisscross direction and then the transmitter can realize both functions. There is described a construction of optical transmitter with plastic optical fibers which merges two LED beams together and provide lighting and communication at the same time

Investment activity of Škoda Auto a.s.

Diplomová práce je zaměřena na hodnocení investičního projektu ve vybrané společnosti. Teoretická část práce se zabývá problematikou investic, členěním investic a zdrojů jejich financování. Je popsán proces přípravy investice a stanovení diskontní míry po teoretické stránce. V neposlední řadě jsou vymezeny metody používané při hodnocení efektivnosti investičních projektů. Praktická část se zaměřuje na konkrétní investiční projekt realizovaný ve společnosti Škoda Auto a.s. Tento investiční projekt je důkladně analyzován a je provedeno jeho vyhodnocení, porovnání v rámci různých úrovní diskontní míry. Dále je navržena jeho možná úprava, která by mohla vést ke zvýšení ekonomického přínosu dané investice. Na základě zjištěných skutečností jsou definovány konkrétní závěry pro společnost Škoda Auto a.s.The diploma thesis deals with the evaluation of the investment project in the selected company. The theoretical part of the diploma thesis is focused on investment issues, types investment and sources of financing. The process of preparing the investment and discount rate is described. Last but not least, there are described evalution's methods of investment projects. Practical part is focused on concrete investment project in Škoda Auto a.s. Investment project is thoroughly described and an analysis of evaluation, comparsion and suggestion of possible improvement with economic benefit is performed. Based on the findings, specific conclusions for Škoda Auto a.s. are made

WWW prezentace Sborníku vědeckých prací

Import 21/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta elektrotechniky a informatiky. Katedra (456) informatik