Synergy of nanocomposite force myography and optical fiber-based wrist angle sensing for ambiguous sign classification. - In: Engineering for a changing world, (2023), 5.2.142, S. 1-2
This paper aims at understanding the capabilities and limitation of combining Nanocomposite Force myography sensors (FMG) and optical fiber sensors in standalone systems and their synergy influence on the classification of ambiguous hand gestures. A set of 10 highly similar hand signs from the fingerspelling of the American sign language is adopted in this study. Force myography (FMG) signals are collected from one healthy subject performing the selected set of gestures with 40 repetitions for each gesture. The K-Tournament Grasshopper Extreme Learner (KTGEL) classifier has been implemented to perform an automated feature selection and hand sign classification with an efficient network size and a high accuracy.
https://doi.org/10.22032/dbt.58941
Resolution enhancement in Fabry-Perot interferometers through evaluation of multiple reflection using range-resolved interferometry. - In: Engineering for a changing world, (2023), 1.1.104, S. 1-8
This work presents a novel approach for improving interferometer resolution with a relatively simple setup by combining the use of range-resolved interferometry and a high-finesse Fabry-Perot setup utilizing multiple reflections in the cavity to gradually increase the resolution. This approach could enable the measurement of small displacements with a potentially much higher resolution than current interferometry methods. A simple proof-of concept setup demonstrated the evaluation of up to four Fabry-Perot passes, while theoretically much higher sensitivity improvement factors should be possible.
https://doi.org/10.22032/dbt.58695
A novel point-to-point length measurement concept based on range-resolved interferometry. - In: Engineering for a changing world, (2023), 1.1.099, S. 1-6
In many fields of research and high-value industry, the estimation of distances and displacements is crucial. Due to their extremely high spatial resolution and flexible application possibilities interferometers are cross-sectorally used in measurement practice. However, classical length measuring interferometers are subject to two residual restrictions. On the one hand, only displacements that are exactly aligned to the interferometer optical axis can be measured. On the other hand, deviating refractive indices in the measuring and reference arm due to different atmospheric conditions represent an accuracy-limiting disturbance. In this paper, a new interferometric concept for length measurement is presented. The concept is based on the range-resolved interferometry technology which enables the simultaneous readout and evaluation of two symmetrical interferometric signals which result from the superposition of two non-collimated spherical wavefronts. This allows a point-to-point measurement between two optical fiber ends and the separation of undesired changes of the optical path length outside the measurement cavity and within the measurement cavity.
https://doi.org/10.22032/dbt.58680
Long-term wavelength stabilisation of widely modulated lasers. - In: Optical Measurement Systems for Industrial Inspection XIII, (2023), 1261816, S. 1261816-1-1261816-8
In this paper, we present a novel technique for stabilisation of widely wavelength modulated lasers (>100pm) over long time scales, where modulation depths exceed the spectral width of standard reference features, such as gas absorption lines, by over an order of magnitude. The technique operates by controlling the temporal separation between successive appearances of a gas absorption line on the up and down sweeps of a sinusoidal laser wavelength modulation waveform. The influence of the signal distortions introduced by the laser intensity modulation that are associated with laser diode injection current modulation are also addressed. The technique is applied to a range-resolved interferometric system interrogating a Mach-Zehnder interferometer operating in thermally stable conditions, using an absorption feature from a fibre-coupled gas cell as a reference. Proof-of-principle measurement results achieved using this technique are presented, demonstrating a notional fractional stability of 3.9×10−7 without further correction.
https://doi.org/10.1117/12.2673684
A fibre optic angle sensing tape for applications in robotics and automation. - In: Optical Measurement Systems for Industrial Inspection XIII, (2023), 126180D, S. 126180D-1-126180D-6
A dual-fibre single-plane angle-sensing tape that utilizes optical Fibre Segment Interferometry and Range- Resolved Interferometry (RRI) for angle sensing is presented. The sensing tape facilitates the multiplexing of an array of angle sensors along its length and can be retrofitted into small robots and construction equipment. We demonstrate its application on three non-rotational joints of a small five-axis robot, describing the design, construction, measurement principle, and presenting measurement results. Preliminary data shows that the angles measured by the sensing tape exhibited agreement within a range of ±0.005˚ with the manufacturer-installed angle encoder of the robot.
https://doi.org/10.1117/12.2673185
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
Fiber-interferometric sensor for velocity measurement in the Planck-Balance. - In: SMSI 2023 Conference - Sensor and Measurement Science International, (2023), S. 127-128
This work describes the use of a compact fiber-interferometric sensor for velocity measurements for the Kibble balance method. Our fiber-interferometric sensor was compared within a Planck-balance setup with a commercial reference interferometer. Results show that the fiber-interferometric sensor is capable of high accuracy velocity measurement comparable with the reference interferometer. High performance and compactness of the sensor head allow it to be integrated into small-size systems, where the use of the conventional interferometer systems is limited or not possible.
https://doi.org/10.5162/SMSI2023/B6.2
Multiplexing interferometers to provide novel capabilities for nanometrology. - In: SMSI 2023 Conference - Sensor and Measurement Science International, (2023), S. 239-240
Multiplexing interferometers within a single beam, based on their optical path difference, using laser wavelength-modulated signal processing techniques such as the range-resolved interferometry method, allows for interesting new capabilities in precision interferometry. For example, these include single-beam differential interferometry or position encoders with multiple degrees-of-freedoms using only a single fibre-coupled access port.
https://doi.org/10.5162/SMSI2023/D6.1
The use of range-resolved interferometry for multi-parameter sensing in a wind tunnel. - In: European Workshop on Optical Fibre Sensors (EWOFS 2023), (2023), 1264303, S. 1264303-1-1264303-4
The work presented demonstrates that key parameters in aerodynamic structural characterisation of pressure, strain, and structural dynamics, can be all measured via optical fibre sensors interrogated using the principles of range-resolved interferometry (RRI). When used to interrogate sensors simultaneously deployed on a high lift wind in a wind tunnel, the approach yielded resolutions of 31 μPa/ &worte; Hz and 1 nε/ &worte; Hz at a bandwidth of 1526 Hz for pressure and strain, respectively, demonstrating the accuracy and versatility of the RRI signal processing technique.
https://doi.org/10.1117/12.2679414
Multipurpose active scanning probe cantilevers for near-field spectroscopy, scanning tunnel imaging, and atomic-resolution lithography. - In: Journal of vacuum science & technology, ISSN 2166-2754, Bd. 41 (2023), 4, S. 042601-1-042601-9
In this work, we report progress on developing a multipurpose scanning probe cantilever applying gallium nitride nanowires as the probe tip. Gallium nitride nanowires possess high potential as probes due to their straight profile, tunable electrical and optical properties, high Young’s Modulus, durability, and high-yield fabrication process. Their wide bandgap enables them to be pumped to emit ultraviolet pulses which can be used for optical imaging and spectroscopy. They can be doped during growth to be electrically conductive, and their sharp tips obtained during epitaxial growth enable confinement of a high electric field at tip-sample interface. Their sharp tips are obtained during fabrication by their epitaxial growth which eliminates the need for postprocess sharpening that is typically required for standard STM tips. We present results of using gallium nitride nanowires for scanning tunnel microscopy applications of atomic-resolution imaging and lithography, and atomic force microscopy applications of imaging and lithography in vacuum and atmospheric environments.
https://doi.org/10.1116/6.0002486