JK
J.P. Kappelhof
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5 records found
1
Industry-wide there is an interest in chemical composition sensing of materials, which requires no sample preparation and can be implemented in real-time. Laser-Induced Breakdown Spectroscopy, or LIBS, is a measurement tool able to achieve this by exciting material, creating an analytical plasma followed by observing its atomic emission of light. Wavelengths characteristic for the elements present in the material can be identified and used for quantitative measurements. This thesis focuses on how an instrument utilizing LIBS can be designed such that deformations of the instrument due to environmental loads do not influence the creation, and especially, the observation of the plasma. Experiments done showed the calibrated algorithm to misestimate the chemical composition if the plasma is partly observed. The proposed design of the instrument is realized and put to the test for thermal and mechanical loads individually, which verified its performance to stably create and observe the analytical plasma while enduring these.
...
Industry-wide there is an interest in chemical composition sensing of materials, which requires no sample preparation and can be implemented in real-time. Laser-Induced Breakdown Spectroscopy, or LIBS, is a measurement tool able to achieve this by exciting material, creating an analytical plasma followed by observing its atomic emission of light. Wavelengths characteristic for the elements present in the material can be identified and used for quantitative measurements. This thesis focuses on how an instrument utilizing LIBS can be designed such that deformations of the instrument due to environmental loads do not influence the creation, and especially, the observation of the plasma. Experiments done showed the calibrated algorithm to misestimate the chemical composition if the plasma is partly observed. The proposed design of the instrument is realized and put to the test for thermal and mechanical loads individually, which verified its performance to stably create and observe the analytical plasma while enduring these.
Master thesis
(2021)
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Parth Deshpande, N. Bhattacharya, L.A. Cacace, P.J. Botma, J.W. Spronck, J.P. Kappelhof
Use of earth observation satellites have grown at a very high rate over the past few decades. On a closer observation of things around, most of them uses satellites, directly or indirectly. Satellites are being used in the day-to-day life without being aware of its application. Satellites are used for small things like weather report, communication to very large things like internet of things (IOT) and earth observation. Some CubeSats are also used for interplanetary missions. For the purpose of earth observation missions, the satellites are installed with an optical payload which is a camera. The cameras used for space are different from the regular camera and have special specifications in terms of the materials, components and the design which make them suitable for space missions. The optical payload which is to be launched has to be made sure that it can survive the launch and in orbit environment. This research focuses on the testing of these CubeSats and check if they are suitable for launch. The research starts with reviewing the testing procedure that is followed before the satellite is launched. A setup is provided for checking the performance of the camera mounted on the CubeSat and its suitability for launch. To investigate the performance of the camera, MTF and correlation techniques are used on different images to come to a conclusion.
...
Use of earth observation satellites have grown at a very high rate over the past few decades. On a closer observation of things around, most of them uses satellites, directly or indirectly. Satellites are being used in the day-to-day life without being aware of its application. Satellites are used for small things like weather report, communication to very large things like internet of things (IOT) and earth observation. Some CubeSats are also used for interplanetary missions. For the purpose of earth observation missions, the satellites are installed with an optical payload which is a camera. The cameras used for space are different from the regular camera and have special specifications in terms of the materials, components and the design which make them suitable for space missions. The optical payload which is to be launched has to be made sure that it can survive the launch and in orbit environment. This research focuses on the testing of these CubeSats and check if they are suitable for launch. The research starts with reviewing the testing procedure that is followed before the satellite is launched. A setup is provided for checking the performance of the camera mounted on the CubeSat and its suitability for launch. To investigate the performance of the camera, MTF and correlation techniques are used on different images to come to a conclusion.
Master thesis
(2020)
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Lars Musters, J.P. Kappelhof, N. Bhattacharya, L.A. Cacace, P. Kruit, J.L. Herder
The manufacturer of an electron beam lithography machine pushes a better understanding and higher performance of the optical column to provide a better product with each iteration. At the heart of the column is the source of electrons: the gun lens. It holds the field emitter from which the electrons originate and accelerates the beam to a first crossover. The main work in this thesis was concerned with development of a new and better gun lens design. Consideration of several physical phenomena is required in order for the gun lens to be more robust and with a more stable beam. It was found that the heating transient plays a large role in the operation of the gun lens. By defining the requirements clearly including by ray-tracing the optical geometry to find optical sensitivities, the main challenges of the project became evident. A new concept design is presented where the heat transport inside the gun lens is improved and thermal drift is greatly diminished. By using the ceramic insulators as flexures the short- and long-term stability of the lenses are improved and the thermal transient settling time is reduced from 26 hours to below 6 hours. By opening up the geometry inside the gun lens the local vacuum at the emitter is much better, which increases its lifetime. The electrostatic fields are made much more robust by burying the triple junction, which required using a new insulator shape. The final result is a gun lens concept design which improves in all aspects while remaining simple in construction.
...
The manufacturer of an electron beam lithography machine pushes a better understanding and higher performance of the optical column to provide a better product with each iteration. At the heart of the column is the source of electrons: the gun lens. It holds the field emitter from which the electrons originate and accelerates the beam to a first crossover. The main work in this thesis was concerned with development of a new and better gun lens design. Consideration of several physical phenomena is required in order for the gun lens to be more robust and with a more stable beam. It was found that the heating transient plays a large role in the operation of the gun lens. By defining the requirements clearly including by ray-tracing the optical geometry to find optical sensitivities, the main challenges of the project became evident. A new concept design is presented where the heat transport inside the gun lens is improved and thermal drift is greatly diminished. By using the ceramic insulators as flexures the short- and long-term stability of the lenses are improved and the thermal transient settling time is reduced from 26 hours to below 6 hours. By opening up the geometry inside the gun lens the local vacuum at the emitter is much better, which increases its lifetime. The electrostatic fields are made much more robust by burying the triple junction, which required using a new insulator shape. The final result is a gun lens concept design which improves in all aspects while remaining simple in construction.
Master thesis
(2020)
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Vilius Čechanavičius, J.P. Kappelhof, S.H. Hossein Nia Kani, N. Bhattacharya, Erik van Dijk
EasyScan is a scanning system, which images the retina. The condition of the retina can help identify various diseases, such as glaucoma, diabetic retinopathy, cataract, macular degeneration and others. It is a commercially successful device that has sold thousands of units worldwide. However, the scanner is facing lifetime issues, as the scanner mirrors will become obsolete in the foreseeable future. Possible ways of improving the optical system by reducing the required scan amplitude were investigated. Optical tests with fine pitch lenticular lenses, diffractive optical elements, and linear diffuser were conducted. No optical improvement was achieved; therefore, the scanner design was based on the functional requirements of the original system. Actuation methods and guiding mechanisms for low cost, low volume applications were studied. The proposed design for both the low frequency (LF) and high frequency (HF) scanners is a compact reluctance force actuated scanner mirror. However, design issues for the LF scanner guiding mechanism were encountered, that could not be solved in time. Nonetheless, a prototype of the HF scanner was finalized and managed to achieve the required $\pm$\SI{3}{\milli\radian} amplitude at a frequency of \SI{4650}{\hertz}. The scanner was validated on an actual EasyScan optical module. However, reliability issues still need to be solved before making the scanner production ready, for which possible solutions are discussed.
...
EasyScan is a scanning system, which images the retina. The condition of the retina can help identify various diseases, such as glaucoma, diabetic retinopathy, cataract, macular degeneration and others. It is a commercially successful device that has sold thousands of units worldwide. However, the scanner is facing lifetime issues, as the scanner mirrors will become obsolete in the foreseeable future. Possible ways of improving the optical system by reducing the required scan amplitude were investigated. Optical tests with fine pitch lenticular lenses, diffractive optical elements, and linear diffuser were conducted. No optical improvement was achieved; therefore, the scanner design was based on the functional requirements of the original system. Actuation methods and guiding mechanisms for low cost, low volume applications were studied. The proposed design for both the low frequency (LF) and high frequency (HF) scanners is a compact reluctance force actuated scanner mirror. However, design issues for the LF scanner guiding mechanism were encountered, that could not be solved in time. Nonetheless, a prototype of the HF scanner was finalized and managed to achieve the required $\pm$\SI{3}{\milli\radian} amplitude at a frequency of \SI{4650}{\hertz}. The scanner was validated on an actual EasyScan optical module. However, reliability issues still need to be solved before making the scanner production ready, for which possible solutions are discussed.
Scanning mirror is a widely used device in many optical systems to position reflected beam. Existing products include galvanometer and resonant scanner. They are intended for accurate positioning at low frequency range and fast scanning at the specified high frequency respectively. However, when a wide frequency range is involved, they might not be able to fulfill the requirement. To solve this generic issue, Hittech starts to research new alternatives. In this paper, a novel solution is proposed, by tuning resonant frequency and exciting higher order modes to cover the intended frequency range 500 - 5k Hz. A flexure mechanism is designed, where the scanner contains a cantilever as resonator, and a cut-leafspring as hinge guiding to achieve 1 DoF resonant scan. Resonant frequency is tuned by clamping different positions of the cantilever by two surfaces with large radius of curvature, and sliding could be enabled by DLC coating. Concept and detailed design are evaluated by finite element modelling and a prototype is built. The test results show a good match with the simulation. The intended frequency range could be covered and the reflected beam could achieve a scanning angle of 1mrad. Unwanted motions of mirror are verified and limited within requirement with large margins, and hence could be negligible for operation.
...
Scanning mirror is a widely used device in many optical systems to position reflected beam. Existing products include galvanometer and resonant scanner. They are intended for accurate positioning at low frequency range and fast scanning at the specified high frequency respectively. However, when a wide frequency range is involved, they might not be able to fulfill the requirement. To solve this generic issue, Hittech starts to research new alternatives. In this paper, a novel solution is proposed, by tuning resonant frequency and exciting higher order modes to cover the intended frequency range 500 - 5k Hz. A flexure mechanism is designed, where the scanner contains a cantilever as resonator, and a cut-leafspring as hinge guiding to achieve 1 DoF resonant scan. Resonant frequency is tuned by clamping different positions of the cantilever by two surfaces with large radius of curvature, and sliding could be enabled by DLC coating. Concept and detailed design are evaluated by finite element modelling and a prototype is built. The test results show a good match with the simulation. The intended frequency range could be covered and the reflected beam could achieve a scanning angle of 1mrad. Unwanted motions of mirror are verified and limited within requirement with large margins, and hence could be negligible for operation.