Measurement Dynamic Range Research Articles

Highly sensitive Laser Photo-Acoustic SF6 Gas Analyzer with 10 decades dynamic range of concentration measurement

A highly sensitive Laser Photo-Acoustic (PA) SF6 Gas Analyzer with dynamic range of ∼10 decades (∼0.1 ppb–100% SF6) has been developed and tested. Gas analyzer is built on the base of RF-excited waveguide CO2 laser, resonant differential photo-acoustic detector (PAD), and sealed-off SF6-gas-filled Ref-cell. The resonant frequency of differential PAD is measured automatically in real time (∼1750–1780 Hz, error ± 0.1 Hz). While measuring SF6 concentration (up to 1000 ppm), normalization of PAD’s absorption signals according by Ref-cell absorption signals significantly reduce the error in PA gas analyzer readings caused by spontaneous tuning of waveguide CO2 laser wavelength near ∼10.6 μm. PA gas analyzer’s background readings was ∼0.1 ppb SF6, the standard dispersion of background signal was ∼10 ppt SF6. Minimum average power of waveguide CO2 laser radiation should be no less than ∼150 mW. Dependence of speed of sound vs gas mixture composition was used to measure SF6 concentration in 0.1–100% range. Resonant frequency of differential PAD varied from ∼1780 Hz (pure N2) to ∼690 Hz (pure SF6), which, after appropriate calibration, makes it possible to measure SF6 concentration up to 100%.

Extended-aperture Hartmann wavefront sensor with raster scanning.

In this paper, we propose an extended-aperture Hartmann wavefront sensor (HWFS) based on raster scanning. Unlike traditional HWFS, where there is a trade-off between the dynamic range and spatial resolution of wavefront measurement, our extended-aperture HWFS breaks the trade-off and thus could achieve a large dynamic range and high spatial resolution simultaneously. By applying a narrow-beam raster-scanning scheme, the detection aperture of our HWFS is extended to 40 × 40 mm2 without using the enlarging 4f relay system. The spatial resolution of our setup depends on the scanning step, the pinhole size, and the wavelength. The sensitivity and dynamic range can be adjusted flexibly by varying the axial distance between the pinhole plane and the imaging sensor plane, because our decoupled large dynamic range could be reasonable traded-off to achieve better sensitivity. Furthermore, compared with tradition HWFS, our method does not need to compute the positions of a two-dimensional spots array where complicated spots tracking algorithms are necessary to achieve high dynamic range, thus remarkably reduces the spots aliasing issue and the computational cost. It should be noted that this scheme is not only applicable for HWFS but also for Shack-Hartmann wavefront sensor (SHWFS) with microlens array to achieve higher accuracy and better power efficiency. Experiments were performed to demonstrate the capability of our method.

A capacitance measurement circuit with current injection compensation

The capacitive touch screen measurement system mainly realizes the conversion of capacitance to digital signal, but the parasitic capacitance existing on the chip IO and PCB board will seriously affect the measurement accuracy of the small inductive capacitance in the capacitance measurement circuit. To solve this problem, a capacitance measurement circuit with adjustable compensation time based on current injection is proposed.The mismatch error in the circuit is analyzed in detail, and the measurement accuracy of capacitance is further improved. The dynamic range of capacitance measurement can be effectively improved by appropriately changing the parameter value of the relevant quantity in the circuit. The circuit design is based on the SMIC 0.18 μm standard CMOS process, and the overall layout area is about 0.21 mm2. The circuit is simulated using Spectre tool, and the results show that the capacitance measurement circuit inductive capacitance of 0 ~ 1 pF in the temperature range of -40 ℃ to 125 ℃, the conversion time is about 50 μs, and the resolution can reach 1 fF, the signal to noise ratio of the converted 12 bit digital signal is 70.1 dB, the effective number of bits is 11.56 bits, the power supply voltage is 1.8 V, and the total power consumption is 0.19 mW.

Inter-satellite laser-ranging based on intradyne coherent detection

With the development of laser communication networking, laser-ranging technology is becoming more and more applicable. In this paper, high-accuracy ranging is implemented based on intradyne coherent detection at a communication rate of 1048.576 Mbps. The ranging accuracy is affected by clock phase calculation error and code loop track error. Parallel clock phase difference calculation, frame head correlation, and ranging ambiguity region handle are combined with the ranging calibration method, realizing millimeter-level corrected distance measurement. Dynamic range measurement above 1 m is proven to be continuous through the ranging ambiguity region handle. In addition, high-precision clock frequency deviation between two asynchronous terminals can be obtained through derivation of one-way distance at static ranging or by derivative of distance difference at bidirectional ranging. The methods proposed in this paper are verified by inter-satellite laser-ranging on orbit, and the results are analyzed.

High-dynamic-range 3D measurement for E-beam fusion additive manufacturing based on SVM intelligent fringe projection system

Electron Beam Metal Additive Manufacturing (EBAM) has been developed over recent years because of its advantages in manufacturing internal features and complex structures with relatively high productivity. The process proceeds by layer by layer melting and re-solidification of metal powder utilising an electron beam energy source. Following solidification of the build layer, the surface becomes ‘shiny’ with high reflectivity which makes in-process inspection of the surface of the build layer using fringe projection, difficult. To address this issue, a novel intelligent fringe projection technique using a support-vector-machine (SVM) algorithm is proposed to measure the 3D topography of high dynamic range surfaces on a layer by layer basis within the EBAM machine. To facilitate the SVM implementation a range of EBAM manufactured surfaces are utilised as samples for training and classification. The training measurements are based on different exposure times and saturated pixels are utilised as feature vectors to predict tested samples categories. Training errors are evaluated, and the correct recognition rate is 91%, which indicates the proposed training method can effectively predict the categories of the surfaces. Examples of melting edge swelling and powder bed inspections during a part build are used to demonstrate the system capability for inspection high dynamic range measurement within the EBAM machine. The whole inspection process lasts less than 5 s with two measurements which minimises the time penalty for the manufacturing process. Experimental results showed that the powder and the melting surface defects could be efficiently inspected using the proposed technology and the measurement result could be fed back to the build process to improve the processing quality.

Physics-based universal outlier detector for flow statistics

Outlier detection for PIV velocity fields is still nowadays an active field of research. In the last decades, several image pre-processing and processing algorithms have been developed aiming at increasing the dynamic velocity range of PIV measurements and reducing the measurement uncertainty. Nevertheless, PIV velocity fields are still often characterised by the presence of outliers, which potentially hamper the correct interpretation of the flow physics and negatively affect the evaluation of the flow statistics. The outlier detection strategies presented in literature are mainly based on the statistical analysis of the velocity vector with its immediate neighbour. Most of these algorithms have been demonstrated to be effective for instantaneous flow fields, where the errors associated with the outliers are order of magnitude larger than the expected measurement uncertainty. However, these approaches are not as effective for the flow statistics, where the outliers yield errors of the same order of the measurement uncertainty. To overcome this limitation, this paper proposed an outlier detection approach based on the agreement of the flow statistics to the constitutive equations, more specifically to the turbulent kinetic energy (TKE) transport equation. The focus is posed on the ratio between the local advection terms of TKE and a robust estimation of the TKE production along the local streamline. It is demonstrated that, in presence of outliers, the proposed principle yields a clear separation between the correct and the erroneous vectors. In order to assess the performance of the proposed principle, three different test cases are considered. For all of them, the results are compared with a reference outlier detection methodology, namely the universal outlier detection method proposed by Westerweel and Scarano (2005). The proposed turbulence transport-based approach exhibits higher performance in terms of percentage of outliers correctly identified in the flow statistics.

Development of ELISA formats for polymyxin B monitoring in serum of critically ill patients

Treating infections in critically ill patients often requires the use of last-line antibacterial drugs such as polymyxins with a narrow therapeutic window and high toxicity. In critically ill patients, the drug pharmacokinetics changes significantly, and as a result, the antibiotic concentrations in blood and infection foci become suboptimal, which leads to therapeutic failures or toxic manifestations. For timely dosage adjustments, a competitive ELISA-based method using antibodies to polymyxin В (PMB) was developed. Among the several considered assays, a direct antibody-coated format was selected for its short duration (1.5 h) and the best agreement with the LC–MS/MS data (R2 = 98 %). The assay dynamic measurement range (IC20-IC80) could be substantially shifted by changing the ratio of immunoreagents. To conveniently measure the therapeutic range of PMB concentrations, it was adjusted to 5.0–192 ng/mL, allowing the samples to be analyzed after a simple 100-fold dilution with the assay buffer. The ELISA sensitivity expressed in half-inhibition concentration (IC50) and the limit of detection were 30.6 and 1.8 ng/mL, respectively. The assay cross-reactivity towards the related analogue colistin (COL) was 95 %, and this compound could also be adequately quantified by the same assay. The PMB and COL recovery from the spiked serum samples was similar and constituted 98–109 %. The trial drug monitoring was carried out in 3 patients with Gram-negative sepsis, and the established pharmacokinetic profiles of PMB revealed the necessity for individual dosage adjustment.

High Dynamic Range Nanowire Resonators.

Dynamic range quantifies the linear operation regime available in nanomechanical resonators. Nonlinearities dominate the response of flexural beams in the limit of very high aspect ratio and very small diameter, which leads to expectation of low dynamic range for nanowire resonators in general. However, the highest achievable dynamic range for nanowire resonators with practical dimensions remains to be determined. We report dynamic range measurements on singly clamped silicon nanowire resonators reaching remarkably high values of up to 90 dB obtained with a simple harmonic actuation scheme. We explain these measurements by a comprehensive theoretical examination of dynamic range in singly clamped flexural beams including the effect of tapering, a usual feature of semiconductor nanowires. Our analysis reveals the nanowire characteristics required for broad linear operation, and given the relationship between dynamic range and mass sensing performance, it also enables analytical determination of mass detection limits, reaching atomic-scale resolution for feasible nanowires.

Correct measurement methodology spatial-energy characteristics of laser beams

A methodology for correct measurements of the spatial and energy characteristics of a laser beam is considered, based on the determination of the initial moments of the spatial intensity distribution in the beam cross section. The classification of radiation fields participating in the measuring process is given: emitted, measured and measured. It is shown that ISO 11146:2005 “Lasers and laser-related equipment. Test methods for laser beam widths, divergence angles and beam propagation ratios, Part 1-3” for measuring the spatial and energy characteristics of laser beams leads to incorrect measurements. This is due to the fact that the recommendations for the application of ISO 11146:2005 do not take into account the dynamic range of the used matrix radiation detectors, and the characteristics of the emitted field of interest to the user turn out to be diverging, which violates the uniformity of measurements. Moreover, the conditions ensuring the convergence of the results are practically impracticable. To solve these problems, it is proposed to establish and regulate the lower level of the dynamic range of measurements of the intensity of the used matrix receivers and to consider the spatial and energy characteristics of the emitted field of interest to the user, depending on the set value of the lower level. It is shown that measurements with this methodology become correct and make it possible to compare the characteristics of laser beams obtained by different array detectors. Formulas are given that take into account the effect of the lower level of the dynamic range of the matrix radiation detectors on the measurement result. These formulas should be recommended for inclusion in the updated edition of the national standard GOST R ISO 11146-2008 “Lasers and laser installations (systems). Methods for measuring widths, divergence angles and propagation coefficients of laser beams. Parts 1-3”.

Low-Frequency Vibronic Mixing Modulates the Excitation Energy Flow in Bacterial Light-Harvesting Complex II.

Oscillatory features observed in two-dimensional electronic spectroscopy (2DES) manifest coherent vibrational and electronic dynamics and even the interplay of them. Recently, we developed a 2DES technique utilizing a pair of synchronized repetition-frequency-stabilized lasers, which enables the wide dynamic range measurements of 2DES signals rapidly. Here, we apply this dual-laser 2DES technique to investigate the electronic energy transfer (EET) process in bacterial light-harvesting complex II consisting of B800 and B850 circular aggregates at ambient temperature, and the coherent vibrational wavepakcet associated with the EET between the two aggregates are measured. Examining the principal component analysis of the time-resolved 2DES signal, we found that the EET from B800 to low-lying B850 states is modulated by a low-frequency (156 cm-1) vibrational mode of the exciton donor (B800). This observation suggests that the donor transition density is modulated by this vibration, which, in turn, modulates the energy transfer dynamics.

PM Level and Large Dynamic Range Glucose Detection Based on a Sandwich Type Plasmonic Fiber Sensor

A sandwich type titled fiber Bragg grating (TFBG) plasmonic sensor based on self-assembled p-mercaptophenylboronic acid (PMBA) monolayer and Au nanoparticles (AuNPs), has been demonstrated and successfully applied for sensitive and stable low-concentration glucose detection. The sensor was immobilized with PMBA monolayer acting as the highly sensitive and stable glucose recognition molecule instead of a traditional unstable enzyme. In the experiments, the high sensitivity for glucose detection is achieved, establishing a competitive limit of detection (LOD) of 295 pM and large dynamic measurement range from 1 nM to 10 mM simultaneously. Moreover, due to the unique two-set diol configurations of glucose, the combination of TFBG-SPR with AuNPs and PMBA exhibit a good selectivity over fructose and galactose, which both possess only one set of diol configurations. Non-invasive saliva glucose detection, as a better alternative to blood, has emerged and attracted many researchers' attention. Therefore, the practicality of this method was successfully validated by detecting glucose in a simulated human saliva sample. We believe that this method represents an appealing solution for flexible, temperature-insensitive, high-sensitivity, and high-stability detection of ultra-low concentration glucose in modern non-invasive point-of-care testing as well as tumor micro-environment (TME) related cancer research.

Fast structured illumination microscopy with a large dynamic measurement range.

Fast structured illumination microscopy plays an important role in micro-nano detection due to the features of high accuracy, high efficiency, and excellent adaptability. The existing method utilizes the linear region of the axial modulation response curve (AMR), and by building the relationship between the modulation and the real height, achieves topography recovery. However, the traditional method is limited to narrow dynamic measurement range due to the linear region of the AMR being very short. In this paper, a double-differential fast structured illumination microscopy (DDFSIM) is proposed. By introducing two additional detectable branches for building the double-differential axial modulation response curve (DDAMR), the proposed method can obtain a large dynamic measurement range. In the measurement, three charge-coupled devices are respectively placed in and behind and before the focal plane to generate three axial modulation response curves. Three AMRs are used to set up the DDAMR, which has a large dynamic measurement range. Through simulation and experimental verification, the measurement range of DDFSIM is twice that of the conventional method under the same system parameters.

Sensing element for the formation fluid refractometer on the basis of total internal reflection

When developing oil fields, there is an urgent task to quickly determine the type of pumped formation fluid, which includes formation gas, formation oil and formation water. In this paper, we propose a new type of a sensor element designed for flow refractometry of formation fluid based on the effect of total internal reflection. The sensor element is a taper tip of a conical shape made of sapphire and is 20 mm in length and 20 mm in diameter. The original shape of the sensor element is determined by a modified ray tracing method, taking into account analytical relations that determine the conditions for providing a larger dynamic range of measurements under specified physical, technological and design constraints. The conversion dependence of the tip is obtained for the wavelengths of 405 nm, 1064 nm and 3300 nm and allows determining the type of formation fluid (gas/water/oil). The proposed method enables the development of conical sensor elements based on the total internal reflection for downhole monitoring systems and optical threshold sensors of the refractive index.

Reynolds stress tensor measurements using magnetic resonance velocimetry: expansion of the dynamic measurement range and analysis of systematic measurement errors

This study presents magnetic resonance velocimetry (MRV) Reynolds Stress measurements in a periodic hill channel with a hill Reynolds number of Re = 29,500. The velocity encoding scheme is based on the ICOSA6 method with six icosahedral encoding directions and multiple encoding values are measured to increase the dynamic range. The full Reynolds stress tensor is obtained from a voxel-wise three-dimensional Gaussian fit using the magnitude data of all acquisitions. The MRV results are compared to a wall-resolved large eddy simulation and laser Doppler velocimetry measurements conducted in the same channel. It is shown that the MRV Reynolds stress data have excellent precision and agree qualitatively with the reference data. However, there are apparent systematic deviations. One of the most prominent error contributions is the signal attenuation caused by higher orders of motion, which leads to an overestimation of the turbulence level. Another fundamental error is identified in the assumption that the turbulence is Gaussian distributed. With the presented reconstruction technique, the MRV data are fitted to a statistical model, and depending on the examined flow setup, the Gaussian model can lead to considerable errors. Possible ways of how to reduce all identified errors are presented. In summary, this technique enables Reynolds stress tensor measurements in complex internal flows with high dynamic range and excellent precision. However, several issues need to be resolved to make the turbulence quantification more accurate.Graphic abstract

Enlarging Dynamic Strain Range in UWFBG Array-Based Φ-OTDR Assisted With Polarization Signal

Phase-sensitive optical time-domain reflectometry ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Phi $ </tex-math></inline-formula> -OTDR) measures the dynamic strain by extracting the phase of the scattering signal. However, the dynamic strain measurement range in conventional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Phi $ </tex-math></inline-formula> -OTDR is restricted by the phase unwrapping algorithm. In this letter, a new phase unwrapping algorithm, combining the phase and polarization information, is proposed and demonstrated to enlarge the dynamic strain measurement range in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Phi $ </tex-math></inline-formula> -OTDR based on ultra-weak fiber Bragg grating (UWFBG) array. By correcting the phase signal with the assistance of polarization signal, the large dynamic strain can be recovered. In experiments, the dynamic strain measurement range is demonstrated to increase by about three times, which cannot be achieved by the conventional unwrapping algorithm. Further, the proposed method has the potential to achieve a large amplitude range determined by polarization signal and a good sensitivity determined by phase signal at the same time.

Utilizing a Terrestrial Laser Scanner for 3D Luminance Measurement of Indoor Environments.

We aim to present a method to measure 3D luminance point clouds by applying the integrated high dynamic range (HDR) panoramic camera system of a terrestrial laser scanning (TLS) instrument for performing luminance measurements simultaneously with laser scanning. We present the luminance calibration of a laser scanner and assess the accuracy, color measurement properties, and dynamic range of luminance measurement achieved in the laboratory environment. In addition, we demonstrate the 3D luminance measuring process through a case study with a luminance-calibrated laser scanner. The presented method can be utilized directly as the luminance data source. A terrestrial laser scanner can be prepared, characterized, and calibrated to apply it to the simultaneous measurement of both geometry and luminance. We discuss the state and limitations of contemporary TLS technology for luminance measuring.

Long-range multicore optical fiber displacement sensor.

In this Letter, a long-range optical fiber displacement sensor based on an extrinsic Fabry-Perot interferometer (EFPI) built with a strongly coupled multicore fiber (SCMCF) is proposed and demonstrated. To fabricate the device, 9.2 mm of SCMCF was spliced to a conventional single-mode fiber (SMF). The sensor reflection spectrum is affected by super-mode interference in the SCMCF and the interference produced by the EFPI. Displacement of the SMF-SCMCF tip with respect to a reflecting surface produces quantifiable changes in the amplitude and period of the interference pattern in the reflection spectrum. Since the multicore fiber is an efficient light collecting area, sufficient signal intensity can be obtained for displacements of several centimeters. By analyzing the interference pattern in the Fourier domain, it was possible to measure displacements up to 50 mm with a resolution of approximately 500 nm. To our knowledge, this is the first time that a multicore fiber has been used to build a displacement sensor. The dynamic measurement range is at least seven times larger than that achieved with an EFPI built with a conventional SMF. Moreover, the SMF-SCMCF tip is robust and easy to fabricate and replicate.

Improved High Dynamic Range for 3D Shape Measurement based on Saturation of the Coloured Fringe

Phase-shifting fringe projection methods have been developed for three-dimensional scanning (Zuo et al., 2018). However, the 3-Dimensional (3D) scanning of objects with a high dynamic reflectivity range based on structured light is a challenging task to achieve (Feng et al., 2018). The incorrect intensities captured will cause phase and measurement errors. Thus, this paper proposes a method that improves the current High Dynamic Range (HDR) (Jiang et al., 2016)) method to increase the dynamic range. The camera and projector have 3 channels, red, green, and blue, which can absorb and project these lights independently. This paper proposes a method that makes use of this by controlling the intensity of each projected for the camera. Each image can be split into 3 channels and provide 3 images which contain different intensities, then it will be used to compute the 3D information. In general, this is done by controlling the projection of red, green and blue (RGB) channel and apply the Jiang’s algorithm (Jiang et al., 2016). The results are compared and analysed with current HDR (Jiang’s method) and the regular three-step phase-shifting methods. From the experimental results, it has shown that our proposed method outperforms the current HDR and the regular three-step phase-shifting methods. Specifically, the proposed method manages to increase the dynamic range of the reflective property of objects. Additionally, our proposed method has also significantly reduced the times of 3D object measurements.

Small All-Range Lidar for Asteroid and Comet Core Missions

We report the development of a new type of space lidar specifically designed for missions to small planetary bodies for both topographic mapping and support of sample collection or landing. The instrument is designed to have a wide dynamic range with several operation modes for different mission phases. The laser transmitter consists of a fiber laser that is intensity modulated with a return-to-zero pseudo-noise (RZPN) code. The receiver detects the coded pulse-train by correlating the detected signal with the RZPN kernel. Unlike regular pseudo noise (PN) lidars, the RZPN kernel is set to zero outside laser firing windows, which removes most of the background noise over the receiver integration time. This technique enables the use of low peak-power but high pulse-rate lasers, such as fiber lasers, for long-distance ranging without aliasing. The laser power and the internal gain of the detector can both be adjusted to give a wide measurement dynamic range. The laser modulation code pattern can also be reconfigured in orbit to optimize measurements to different measurement environments. The receiver uses a multi-pixel linear mode photon-counting HgCdTe avalanche photodiode (APD) array with near quantum limited sensitivity at near to mid infrared wavelengths where many fiber lasers and diode lasers operate. The instrument is modular and versatile and can be built mostly with components developed by the optical communication industry.

Numerical Modelling of the Optical Properties of Plasmonic and Latex Nanoparticles to Improve the Detection Limit of Immuno-Turbidimetric Assays.

Turbidimetric assays with latex nanoparticles are widely applied for the detection of biological analytes, because of their rapidity, low cost, reproducibility, and automatization. However, the detection limit can be lowered only at the price of a reduced dynamic range, due to the rapid saturation of the light scattering signal at high analyte concentration. Here, we use numerical calculations to investigate the possibility of increasing the performance of immuno-turbidimetric assays without compromising the measurement dynamic range, by combining plasmonic (gold, silver) and latex nanoparticles. Our modelling results show that plasmonic nanoparticles are compatible with a large signal change even when small aggregates are formed, i.e., at low analyte concentration. The working principle relies on the remarkable modification of the surface plasmon band when noble metal nanoparticles form oligomers, and also when latex particles are included in the aggregate. At high analyte concentration, when larger aggregates form, the latex particles can provide the required linear response of standard immuno-turbidimetric assays. Thus, the combination of the two components can be a successful strategy to improve the detection limit and the dynamic range, while maintaining all the advantages of the homogeneous immuno-turbidimetric assays.