Absolute determination of a large mirror surface from spatial gradients using a coordinate measuring machine. - In: Applied Optical Metrology V, (2023), 1267205, S. 1267205-1-1267205-7
This investigation proposes a method for absolute surface determination in a coordinate measuring machine (CMM) with a planar extension of 200 x 200 mm² which is based on the measurement of two spatial gradient fields. The gradient field data was obtained by measuring a test mirror in two equidistant shifted positions along two orthogonal axes while the reference mirror stayed in a steady position. The comparison of experimental data measured in an area of 192 × 192 mm² showed a small root-mean-square deviation of 5.3 nm between the reconstruction result and a regular measurement result. For an a priori estimation of the influence of experimental error sources on the reconstruction deviation, simulations of the measurement process were carried out. Alongside determining the optimal measurement strategy, the focus was investigating positional and orientational deviations of the test surface caused by the shifting motions. While the translational deviations have a subordinate effect, the simulated results show that small orientation deviations around the motion axes cause high reconstruction deviations. To eliminate the motion-induced share of the gradient fields orientation a separation from the topography intrinsic share, which has to remain part of the data, is necessary. This is achieved by the combination of the high-precision design of the mechanical shifting stage and the implementation of an additional boundary condition in the data processing using a least square algorithm.
https://doi.org/10.1117/12.2675734
Investigation on the lithographic process of a high-precision direct laser writing system. - In: Nanoengineering: Fabrication, Properties, Optics, Thin Films, and Devices XX, (2023), 126530A, S. 126530A-1-126530A-7
The semiconductor industry is an unbelievable fast-growing field with an exponential growth in the space optimization. But also, other large industrial field are getting smaller in the structure size, for example the field of optics. On the other hand, the customer demands get more and more complex and individual. This leads to an enormous growth potential for micro- and nanofabrication with direct laser writing. Under this circumstance the idea for a micro- and nanostructuring possibility with high precision on large areas was born. A setup was developed to combine a nanopositioning and nanomeasuring machine (NMM-1) with an extremely high precision and a two-photon based illumination system to realize a high-precision direct laser writing system. Besides its high positioning resolution of 0.1 nm and its metrological traceability based on an interferometrical measurement setup, the NMM-1 offers a positioning range of 25 mm x 25 mm x 5 mm. The aim is to design a direct laser writing setup, which enables a trans-scale fabrication without any stitching or combination of different positioning systems necessary. In order to benefit from this high positional accuracy, studies have been made to investigated the two photon absoption process and reduce line widths. The presented research shows investigations, which were made with the developed laser writing setup, to invested illumination dose and the voxel position of the writing laser, in order to improve microstructuring and to reduce structure widths.
https://doi.org/10.1117/12.2677297
Modularer Aufbau für das direkte Laserschreiben für Hochpräzise Nanostrukturierung :
Modular Direct Laser Writing setup for high precision nanostructuring. - In: Technisches Messen, ISSN 2196-7113, Bd. 90 (2023), 11, S. 749-758
The increasing demand for micro- and nanofabrication and in parallel the increasing requirements on feature size and resolution is leading to an enormous growth in the field of multi-photon three-dimensional fabrication. To enable new and diverse investigations in this field and to enable high precision for nanofabrication on large areas, a high precision positioning system is combined with an ultra-short pulse laser system. The aim is a modular setup with constant adherence to the Abbe-comparator principle in order to achieve systematic improvements in the area of Direct Laser Writing. For a high-quality identification of the microstructures a measurement tool based on atomic force microscopy is used. To enable the fabrication of continuous micro- and nanostructures on large area, an extremely high positioning precision is used, where no further stitching methods are necessary. Therefore as base of the Direct Laser Writing system the nanopositioning and nanomeasuring machine (NMM-1) is used, which was developed at Technische Universität Ilmenau together with SIOS Meßtechnik GmbH, with a positioning volume of 25 mm × 25 mm × 5 mm and a positioning resolution in the sub-nanometer range. First investigations already confirmed that microfabrication with a Femtosecond Laser and the NMM-1 could be realized and showed the possibility of further developments in the field of Direct Laser Writing. Now the modular structure as a research platform is designed in such a way that the various extensions and measurement setups for large-scale investigations can always be implemented in a metrologically traceable manner. The presented work shows the development of a modular functional setup of an exposure system and NMM-1, which enables micro- and nanofabrication and an improvement in the structure size over large areas.
https://doi.org/10.1515/teme-2023-0025
Double-pass modulated differential confocal microscopy for closed-loop axial control of direct laser writing. - In: Optical Measurement Systems for Industrial Inspection XIII, (2023), 126180R, S. 126180R-1-126180R-11
Direct laser writing is a popular method for mask-less lithography that already achieved commercial grade. However, it is still challenging to realize homogeneously exposed structures on 3D-shaped substrates. A common source of the variation in exposure is a changing distance of the substrate surface with the photoresist towards the plane of the narrowest waist of the exposure beam. To tackle this issue, we propose a differential confocal probe that employs a spatially modulated pinhole. This phase-modulated lock-in principle enables highly resolved depth sensing without ambiguity about the direction of the deviation from the focal plane. However, the modulation contrast must be high enough to achieve this, which is why the measuring beam passes the pinhole twice. This probe is integrated into the nanopositioning and nanomeasuring machine via a position-based controller. We demonstrate the capability to follow 10◦ inclined substrates.
https://doi.org/10.1117/12.2673874
Development of microinterferometers based with fiber coupling :
Entwicklung von Mikrointerferometern mit Faserkopplung. - In: Technisches Messen, ISSN 2196-7113, Bd. 90 (2023), S. S108-S113
Die Einsatzmöglichkeiten von konventionellen Interferometersystemen sind oft aufgrund ihrer Baugröße eingeschränkt. Weiterhin stellen sie noch immer preisintensive, manuell gefertigte Präzisionsbaugruppen dar. Ihr Einsatz ist daher ökonomisch nur für Nischenanwendungen in der Hochtechnologie gerechtfertigt. Aus diesem Grund wird ein neues kompaktes Mikrointerferometer entwickelt, welches auf dem Michelson-Prinzip basiert. Die gesamte Baugröße dieses Mikrointerferometer beträgt 40 mm x 20 mm x 15 mm. Als Strahlteiler wird eine Strahlteilerplatte verwendet, der nicht auf beiden Seiten parallel ist, sondern einen Keilwinkel hat. Dadurch wird der Interferenzwinkel erzeugt. Außerdem sind beide Seiten mit Polarisationsbeschichtung und Entspiegelungsbeschichtung versehen. Zukünftig können die Beschichtungen auf eine große Platte vorbereitet werden und dann ist eine Massenfertigung für die Strahlteilerplatten möglich, sodass die Herstellungskosten dieser Strahlteilerplatten reduziert werden.
https://doi.org/10.1515/teme-2023-0073
Development of a nephrological optical measuring method for determining particle concentrations in gases and liquids behind light-scattering plastic walls :
Entwicklung eines nephrologisch optischen Messverfahrens zur Bestimmung von Partikelkonzentrationen in Gasen und Flüssigkeiten hinter lichtstreuenden Kunststoffwandungen. - In: Technisches Messen, ISSN 2196-7113, Bd. 90 (2023), S. S37-S42
Ziel dieser Arbeit ist die Entwicklung eines optischen Messverfahrens mit dessen Hilfe kleine Objekte, die sich hinter lichtstreuenden Schichten befinden, als scharfe Abbildung reproduziert werden können. Ein praktisches Anwendungsbeispiel ist die zahlenmäßige Erfassung von Leukozyten, die sich im Dialysat innerhalb von Kunststoffschläuchen befinden. Der wesentliche Teil der Arbeit war Entwicklung und Test eines maschinellen Lernalgorithmus, mit dem Ziel die Bilder ohne Anwendung aufwändiger optischer Maßnahmen zu rekonstruieren. Die Ergebnisse der angewandten künstlichen Intelligenz (KI) zeigten die Robustheit des Ansatzes bei der Erkennung verschiedener Objekte mit hoher Geschwindigkeit. Als Endergebnis wurde die Nutzbarkeit der eingebetteten KI mit hoher Genauigkeit bestätigt. Der KI-Rekonstruktionsalgorithmus dieser Studie unterscheidet sich in vielen Punkten von früheren Forschungen.
https://doi.org/10.1515/teme-2023-0070
In-situ calibration method for thermocouples in accelerating rate calorimeter based on multiple fixed-points and Joule heat. - In: Thermochimica acta, Bd. 726 (2023), 179559, S. 1-11
To solve the problem of temperature drift of thermocouples in accelerating rate calorimeter caused by long-term operation, an in-situ calibration method based on multiple fixed-points and Joule heat is proposed in this article. Firstly, the heat transfer model of the calorimeter is established, and the validity of the method is verified by numerical simulation. Secondly, a multiple fixed-points graphite calibrator and a cylindrical electronic resistance element are designed. Finally, the in-situ calibration is carried out. The calibration results show that the maximum permissible measurement error of the sample thermocouple after calibration is better than 0.220 ˚C and that the bias of consistency in-situ calibration method is smaller than 0.110 ˚C. In addition, a di-tert-butyl peroxide in toluene solution with a mass percent of 20% is selected as the experimental sample. The sample experiment results show that the kinetic and thermodynamic parameters are closer to the reference values after thermocouples calibration.
https://doi.org/10.1016/j.tca.2023.179559
Comparison of fiber interferometric sensor with a commercial interferometer for a Kibble balance velocity calibration. - In: Measurement science and technology, ISSN 1361-6501, Bd. 34 (2023), 12, 125017, S. 1-10
This article presents a fiber interferometric sensor (FIS) for measuring the velocity amplitude of an oscillatory vibrating object, with a focus on velocity mode measurement in applications using the Kibble balance principle. The sensor uses the range-resolved interferometry method to measure the displacement of the moving object and employs a multi-harmonic sine-fit algorithm to estimate the displacement amplitude and frequency, thereby determining the velocity amplitude. This article provides a comprehensive explanation of the experimental setup and the measurement techniques employed, as well as a detailed analysis of the uncertainty budget, with the performance validation of the FIS benchmarked against a commercial interferometer within a Kibble balance setup. The velocity amplitude of a coil of the Kibble balance, oscillating with an approx. amplitude of 20 μm and a frequency of 0.25 Hz, was measured using the sensor and found to be 31.282 31 μm s^−1 with a relative deviation of −1.9 ppm compared to a commercial interferometer. The high performance of the FIS, especially with regard to non-linearity errors, and the small size of the measuring head enable universality of integration into a wide variety of measurement systems, also including the use as general-purpose vibration and displacement sensor.
https://doi.org/10.1088/1361-6501/acf2b7
Improved peak-to-peak method for cavity length measurement of a Fabry-Perot etalon using a mode-locked femtosecond laser. - In: Optics express, ISSN 1094-4087, Bd. 31 (2023), 16, S. 25797-25814
Differing from the conventional peak-to-peak method using two neighboring spectral peaks in the frequency-domain fringe spectrum of the spectral response of a Fabry-Perot etalon to a femtosecond laser, which contains N spectral peaks equally spaced with a spacing of the etalon free spectral range (FSR), the proposed method employs a pair of spectral peaks with a spacing of an integer multiple k (k ≫ 1) of FSR for measurement of the etalon cavity length d with a reduced measurement error. Under the constrain of the total N spectral peaks obtainable in the finite spectral range of the femtosecond laser, the optimized k is identified to be N/2 in consideration of an averaging operation using N - k samples of d to achieve the minimum measurement error. The feasibility of the proposed method is demonstrated by experimental results with an uncertainty analysis based on "Guides to the Expression of Uncertainty in Measurement".
https://doi.org/10.1364/OE.493507
Improved calibration capabilities for infrared radiation thermometers and thermal imagers in the range from -60 ˚C to 960 ˚C at the Physikalisch-Technische Bundesanstalt. - In: SMSI 2023 Conference - Sensor and Measurement Science International, (2023), S. 398-399
At the Physikalisch-Technische Bundesanstalt (PTB), the national metrology institute of Germany, the calibration facility for thermal imager, infrared calibrators, and radiation thermometers has been up-dated to improve the calibration service. An additional cesium-heatpipe blackbody was installed to close the temperature gap from 270 ˚C to 500 ˚C and a new sodium-heatpipe blackbody was taken into operation. In addition, the precision of the positioning of the devices under test was improved and the new blackbodies were characterized and tested. The calibration facility now marks the state-of-the-art in terms of achievable uncertainties and automatization.
https://doi.org/10.5162/SMSI2023/P61