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Temperature stabilization of semiconductor lasers for direct measurement of index of refraction of air
Matoušek, Vít
Laser interferometers are even more precise distance measurement devices with resolution in nanometer or sub-nanometer region. If interferometric measurements are carried out under atmospheric conditions (usual situation in industry), they measure optical path length of an unknown distance instead of its true geometrical value. It is caused by an index of refraction of air that introduces a multiplicative constant to measured results. If we want to obtain correct values, the knowledge of the index of refraction is necessary. Generally, the index of refraction can be measured by two ways: indirectly or directly. The first of them is based on parametric analysis of atmospheric properties as: relative humidity, pressure, temperature, concentration of CO.sub.2./sub. etc. Values of these parameters are processed then by Edlen formulas with 10.sup.-7./sup. order [1]. The direct methods are more precise then Edlen formulas (more than 10.sup.-7./sup.) but their practical implementation is more difficult. Devices that directly measure the index of refraction are called refractometers.
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Temperature stabilization of semiconductor lasers for direct measurement of index of refraction of air
Matoušek, Vít
Laser interferometers are even more precise distance measurement devices with resolution in nanometer or sub-nanometer region. If interferometric measurements are carried out under atmospheric conditions (usual situation in industry), they measure optical path length of an unknown distance instead of its true geometrical value. It is caused by an index of refraction of air that introduces a multiplicative constant to measured results. If we want to obtain correct values, the knowledge of the index of refraction is necessary. Generally, the index of refraction can be measured by two ways: indirectly or directly. The first of them is based on parametric analysis of atmospheric properties as: relative humidity, pressure, temperature, concentration of CO.sub.2./sub. etc. Values of these parameters are processed then by Edlén formulas with 10.sup.-7./sup. order [1]. The direct methods are more precise then Edlén formulas (more than 10.sup.-7./sup.) but their practical implementation is more difficult. Devices that directly measure the index of refraction are called refractometers.
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Workplace for stabilization of laser frequency
Buchta, Zdeněk
This paper describes a new appliance for demonstration of frequency stabilization of a laser diode. That is an original solution which is appointed for hands-on teaching students of optoelectronic courses. The arrangement consists of a laser diode driver, temperature controller and driver for the photodetector.
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Scanning electron microscopy with low energy electrons
Mika, Filip
A method of scanning electron microscopy (SEM) of nonconductive specimens, based on measurement and utilisation of the critical energy of electron impact, is described in detail together with examples of its application. The critical energy, at which the total electron yield curve crosses the unit level, is estimated on the base of measurement of the time development in the image signal from beginning of irradiation. The method is programmed and implemented as a module to the controlling software of the micropscope type VEGA, where it secures fast search for the critical energy value.
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Scanning electron microscopy with low energy electrons
Mika, Filip
A method of scanning electron microscopy (SEM) of nonconductive specimens, based on measurement and utilisation of the critical energy of electron impact, is described in detail together with examples of its applications. The critical energy, at which the total electron yield curve crosses the unit level, is estimated on the base of measurement of the time development in the image signal from beginning of irradiation. The method is programmed and implemented as a module to the controlling software of the microscope type VEGA, where it secures fast search for the critical energy value.
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Auger electron spectro-microscopy
Hrnčiřík, Petr
The short escape depth of Auger electrons, the high lateral resolution, the chemical information about superficial elemental composition and the possibility of measuring the indepth distribution of elements (with utilisation of the ion sputtering) are the main advantages of the Auger electron spectroscopy (AES). When combined with the scanning electron miscroscope, AES can provide with image signal suitable for spectro-micrographs showing distribution of elements over the surface, i.e. the chemical mapping. This mapping can be advantageously compared with other SEM image signals in order to faciliate their interpretation.
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Adaptation of scanning electron microscope to environmental scanning electron microscope
Neděla, Vilém
This paper deals with adaptation of the scanning electron microscope (SEM) to the environmental scanning electron microscope (ESEM). It focuses especially to the construction and assembly of the differential pumping chamber together with the detector board of the differential pumping chamber and it comments reasons of necessity of the assembly of these parts in the environmental scanning electron microscope.
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Relaxation Processes in NMR
Rychnovský, Jan
The main tendency of this paper is to bring an explanation of the relaxation times that are concur in Nuclear Magnetic Resonance (NMR). I remind primarily what is the NMR and spectroscopy. After that relaxation processes, which occur in NMR, are explained as well as their measurement.
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