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Analysis and verification of air refractive index measurement method for laser interferometry
Pikálek, Tomáš ; Novák,, Jiří (referee) ; Buchta, Zdeněk (advisor)
This thesis deals with a theoretical analysis and experimental verification of a new method for the refractive index of air measurement. This method uses a combination of laser and low-coherence interferometry. The experimental setup is based on the Michelson interferometer equipped with a double-spaced glass cell. The optical path difference between the inner and outer part of the cell that is proportional to air refractivity is estimated using two low-coherence interference signals. These signals are analysed in the frequency domain which results in the dependence of the phase change caused the by air on vacuum wavelength. This dependency is fitted by a theoretical function based on Edlén's equations in order to calculate the phase difference for laser wavelength. This value is then made more accurate utilising two laser interference signals and used for the air refractive index calculation. The new method was experimentally verified and compared to two different techniques. Moreover, the measurement uncertainty was evaluated.
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Advanced Interferometric Methods of Coordinates Measurement
Holá, Miroslava ; Klapetek,, Petr (referee) ; Mrňa, Libor (referee) ; Lazar, Josef (advisor)
This thesis addresses particular topics in the field of the length metrology for nanometrology. Nanometrology deals with dimensional measurements of micro- and nanostructures with a high spatial resolution. It typically combines a microscope imaging with a precise coordinate measurement, usually capable of nanometre resolution using the state-of-art laser interferometry techniques. The development in this field is driven, among others, by emerging advanced nanotechnologies that demand to push further the capabilities and limits of the interferometric techniques to make the nanometre-level dimensional measurement of nanostructures possible. The principal limitations of current systems are the environmental conditions and especially the fluctuations in the refractive index of air. The theoretical part of this thesis aim at analysis of individual parts of laser interferometer. I oriented myself on the study of their advantages/disadvantages and further also the possibilities of their industrial applications. The second part of the thesis presents my work that focused on the influence of the refractive index of air (RIA) on the measurement uncertainty. I experimentally demonstrated an interferometric system with a self-cancellation RIA fluctuations: a transparent photodetector is used for the measurement of the standing wave along the axis of a passive resonator, where the resonator also serves as a reference for the laser wavelength stabilisation. Another optical arrangement, based on a setup of several Michelson interferometers, represents a combination of an interferometer and a refractometer into a single system. This setup was used to study the behaviour of the ambient airflow with respect to the optical path difference and physical separation of the interferometer’s and refractometer’s path. Based on the experimental results I proposed new arrangements for shape measuring interferometers, which combine length interferometry and a tracking refractometer for the direct compensation of RIA fluctuations with geometrically adjacent optical beams. The results indicate an improvement in RIA fluctuation induced uncertainty by a factor of 100. Third part describes the design and implementation of interferometric systems for specific applications. For the industrial environment I developed a compact interferometric displacement gauge which is designed to allow nanometre level measurement using a simplified interferometer construction. For coordinate measurement of the position of the sample up to six degrees of freedom, I realised a compact modular interferometric system, which represents a unique setup together with a stabilised laser source. To measure the position of the sample in an electron beam writer chamber, I designed and implemented a differential interferometer that works in the near infrared domain and uses a new detection method developed for this system. In the fourth part I describe the realisation of a high-speed interferometer with a differential arrangement, which allows evaluation of high-cycle fatigue in material engineering. This method of studying high-cycle fatigue should be beneficial for both the basic research and the engineering practice.
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Atmospheric correction unit for the laser interferometer
Kučera, Stanislav ; Drexler, Petr (referee) ; Szabó, Zoltán (advisor)
This work deals with design, realization and testing the device for suppression the effect of the fluctuation of the atmospheric conditions on the laser interferometer measurement. Parasitic and randomly changes of atmospheric conditions – temperature, pressure, relative humidity and chemical composition of the air changes his refractive index, then wavelength of the laser light in this environment. Physical properties of air are measured by ultraprecision sensors. The actual wavelength is periodically calculated from Edlén formula. The device is processing the quadrature output signals from receiver of the homodyne interferometer include the atmospheric correction in real time. The device is equipped with interface to data acquisition into the personal computer.
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SMV-2017-22: Development of a multiaxis interferometric system of coordinate measurement
Holá, Miroslava ; Lazar, Josef ; Hucl, Václav ; Čížek, Martin
The aim of the project of the contractual research was development of a multiaxis interferometric system for coordinate measurement. This system make possible to contactless measurement of displacement in axis x, y with compensation refractive index of air. The emphasis was placed on with high accuracy and repeatability measurement on nanometre level for wavelength 633 nm. Part of the contractual research was development and realization driving system for detection of signals. We used homodyne detection system. The measurement system was tested in laboratory and then was installed in the aim system.
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Advanced Interferometric Methods of Coordinates Measurement
Holá, Miroslava ; Klapetek,, Petr (referee) ; Mrňa, Libor (referee) ; Lazar, Josef (advisor)
This thesis addresses particular topics in the field of the length metrology for nanometrology. Nanometrology deals with dimensional measurements of micro- and nanostructures with a high spatial resolution. It typically combines a microscope imaging with a precise coordinate measurement, usually capable of nanometre resolution using the state-of-art laser interferometry techniques. The development in this field is driven, among others, by emerging advanced nanotechnologies that demand to push further the capabilities and limits of the interferometric techniques to make the nanometre-level dimensional measurement of nanostructures possible. The principal limitations of current systems are the environmental conditions and especially the fluctuations in the refractive index of air. The theoretical part of this thesis aim at analysis of individual parts of laser interferometer. I oriented myself on the study of their advantages/disadvantages and further also the possibilities of their industrial applications. The second part of the thesis presents my work that focused on the influence of the refractive index of air (RIA) on the measurement uncertainty. I experimentally demonstrated an interferometric system with a self-cancellation RIA fluctuations: a transparent photodetector is used for the measurement of the standing wave along the axis of a passive resonator, where the resonator also serves as a reference for the laser wavelength stabilisation. Another optical arrangement, based on a setup of several Michelson interferometers, represents a combination of an interferometer and a refractometer into a single system. This setup was used to study the behaviour of the ambient airflow with respect to the optical path difference and physical separation of the interferometer’s and refractometer’s path. Based on the experimental results I proposed new arrangements for shape measuring interferometers, which combine length interferometry and a tracking refractometer for the direct compensation of RIA fluctuations with geometrically adjacent optical beams. The results indicate an improvement in RIA fluctuation induced uncertainty by a factor of 100. Third part describes the design and implementation of interferometric systems for specific applications. For the industrial environment I developed a compact interferometric displacement gauge which is designed to allow nanometre level measurement using a simplified interferometer construction. For coordinate measurement of the position of the sample up to six degrees of freedom, I realised a compact modular interferometric system, which represents a unique setup together with a stabilised laser source. To measure the position of the sample in an electron beam writer chamber, I designed and implemented a differential interferometer that works in the near infrared domain and uses a new detection method developed for this system. In the fourth part I describe the realisation of a high-speed interferometer with a differential arrangement, which allows evaluation of high-cycle fatigue in material engineering. This method of studying high-cycle fatigue should be beneficial for both the basic research and the engineering practice.
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Atmospheric correction unit for the laser interferometer
Kučera, Stanislav ; Drexler, Petr (referee) ; Szabó, Zoltán (advisor)
This work deals with design, realization and testing the device for suppression the effect of the fluctuation of the atmospheric conditions on the laser interferometer measurement. Parasitic and randomly changes of atmospheric conditions – temperature, pressure, relative humidity and chemical composition of the air changes his refractive index, then wavelength of the laser light in this environment. Physical properties of air are measured by ultraprecision sensors. The actual wavelength is periodically calculated from Edlén formula. The device is processing the quadrature output signals from receiver of the homodyne interferometer include the atmospheric correction in real time. The device is equipped with interface to data acquisition into the personal computer.
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Analysis and verification of air refractive index measurement method for laser interferometry
Pikálek, Tomáš ; Novák,, Jiří (referee) ; Buchta, Zdeněk (advisor)
This thesis deals with a theoretical analysis and experimental verification of a new method for the refractive index of air measurement. This method uses a combination of laser and low-coherence interferometry. The experimental setup is based on the Michelson interferometer equipped with a double-spaced glass cell. The optical path difference between the inner and outer part of the cell that is proportional to air refractivity is estimated using two low-coherence interference signals. These signals are analysed in the frequency domain which results in the dependence of the phase change caused the by air on vacuum wavelength. This dependency is fitted by a theoretical function based on Edlén's equations in order to calculate the phase difference for laser wavelength. This value is then made more accurate utilising two laser interference signals and used for the air refractive index calculation. The new method was experimentally verified and compared to two different techniques. Moreover, the measurement uncertainty was evaluated.
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Study of behavior of the refractive index fluctuations to the lenght noise in displacement interferometry
Holá, Miroslava
Nanoscale measurement became one of the key challenges in the field of metrology in last ten years. The international project launched called “Nanotrace” where renowned EU laboratories including the proposer of this project were trying to break the limits of resolution in interferometry. Techniques investigated here have proven that there are chances to achieve significant improvements in resolution of laser interferometry. Measurement of position within a limited range is typical for coordinate measuring system such as nanometrology standards combining scanning probe microscopy (SPM) with precise positioning. In this contribution we evaluate the level of uncertainty associated with spatial shift of two measuring beams and spatial shift of one measuring beam (change of length the measuring beam). Consequently the nature of the fluctuations of the refractive index of air in laser interferometry is investigated anddiscussed with the focus on potential applications in coordinate measuring systems and long-range metrological scanning pro microscopy systems.
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Detection standing wave within Fabry-Perot Cavity
Holá, Miroslava
This contribution follows up with project Interferometry with compensation of the refractive index of air. This inteferometric technique was based on differential interferometry setup for measurement in the subnanometer scale in atmospheric conditions. One of the important limiting factor in any optical measurement are fluctuations of the refractive index of air representing a source of uncertainty on the 10-6 level when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of overdetermined interferometric setup where the reference length is derived from a mechanical frame made from a material with very low thermal coefficient on the 1*E-8 level (Zerodur - Schott). The optical setup consists of three interferometers sharing the same beam path where two measurement differentially the displacement while the third evaluates the changes in the measuring range acting as a tracking refractometer. The concept of stabilization of wavelength against the mechanical reference is realized within passive Fabry-Perot cavity. The link between the wavelength and mechanical reference here is in principle simple, the laser optical frequency has to be locked to the resonance of the passive cavity either through tracking the transmission maximum or reflection minimum. The key component for position sensing inside of a passive Fabry-Perot cavity is low-loss transparent photodetector. The transparent photodetector made in cooperation with Institute of Physics of the ASCR - Department of Thin Films and Nanostructures (work group A. Fejfar). Transparent photodetector is made of fused silica substrate, active photo resistive silicon layer with side titanium electrode and a set of antireflection coatings optimized for minimum reflectivity. Optimized AR coating for 532 nm.
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The smart electronic unit for precise measurement of refractive index of air in a nano-positioning stage for scanning probe microscopy (SPM)
Hucl, Václav ; Čížek, Martin ; Buchta, Zdeněk ; Mikel, Břetislav ; Lazar, Josef ; Číp, Ondřej
When the traceable measurement of dimensions of samples in scanning probe microscopy is needed the position of the probe tip has to be monitored by a set of laser interferometers. The measurement is done very often during standard atmospheric conditions so the changes of the refractive index of air have an influence to measured values of the length with 1.0exp(-4) relatively. Thus the measurement of the refractive index of air and application of the instantaneous value of the index to all of measurement interferometric axes is necessary. In the work we developed new concept of electronic unit which is able to monitor the refractive index of air on basis of measurement of weather conditions: temperature, humidity and pressure of the air. The unit uses modified Edlen formula for calculation of the refractive index. The next step of the work is verification of accuracy of the measuring capability of the unit. We tested the accuracy with reference unit which measure the refractive index of air by a set of etalon sensors. The expected accuracy of the smart electronic unit falls to the 4.1exp(-7) relatively. The important advantage of the unit is very low power consumption of electronics so the unit causes very small temperature effects to the measuring process.
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