Performance Of Optical Sensor Research Articles

Image Quality Assessment of a CMOS/Gd2O2S:Pr,Ce,F X-Ray Sensor

The aim of the present study was to examine the image quality performance of a CMOS digital imaging optical sensor coupled to custom made gadolinium oxysulfide powder scintillators, doped with praseodymium, cerium, and fluorine (Gd2O2S:Pr,Ce,F). The screens, with coating thicknesses 35.7 and 71.2 mg/cm2, were prepared in our laboratory from Gd2O2S:Pr,Ce,F powder (Phosphor Technology, Ltd.) by sedimentation on silica substrates and were placed in direct contact with the optical sensor. Image quality was determined through single index (information capacity, IC) and spatial frequency dependent parameters, by assessing the Modulation Transfer Function (MTF) and the Normalized Noise Power Spectrum (NNPS). The MTF was measured using the slanted-edge method. The CMOS sensor/Gd2O2S:Pr,Ce,F screens combinations were irradiated under the RQA-5 (IEC 62220-1) beam quality. The detector response function was linear for the exposure range under investigation. Under the general radiography conditions, both Gd2O2S:Pr,Ce,F screen/CMOS combinations exhibited moderate imaging properties, in terms of IC, with previously published scintillators, such as CsI:Tl, Gd2O2S:Tb, and Gd2O2S:Eu.

Enhancing performance of optical sensor through the introduction of polystyrene and porous structures

ABSTRACTSimple and promising approaches for developing high‐performance Fe3+ sensors were proposed. Polyvinyl chloride (PVC) membrane containing pyrene as a fluorescent indicator was prepared via solvent‐cast method. Upon immersion into 1.0 mM Fe3+ solution, the fluorescence emission of the membrane decreased with the ratio of fluorescence intensities before and after (F0/F) immersion of 1.25. The sensitivity enhancement was achieved through the introduction of polystyrene (PS) onto PVC and the introduction of porous structures. Polyvinyl chloride‐graft‐polystyrene copolymers (PVC‐g‐PS) were synthesized via Atom Transfer Radical Polymerization using PVC as macroinitiator. The grafting percentages of PS on PVC calculated from Nuclear Magnetic Resonance Spectroscopy were 17 and 41. The membrane prepared from low molecular weight copolymer showed higher sensing ability than that from PVC with the F0/F value of 1.39. The increase in PS chain length did not significantly affect the fluorescence quenching. A Stern–Volmer quenching relationship was found with Ksv of 3.96 × 102 M−1. The effect of porous structures on fluorescence quenching was studied by introducing Triton X‐100 as a porogen to PVC/pyrene solution. Attenuated total reflection Fourier transform infrared spectroscopy and Scanning Electron Microscopy analyses confirmed a complete removal of Triton X‐100 after 3 days of immersion in water. The porous membrane demonstrated an enhanced sensing performance with the F0/F value of 1.46. PVC‐g‐PS/pyrene membrane exhibited highly sensitive and selective responses toward Fe3+ over Cu2+, Mg2+, Co2+, Zn2+, Ni2+, and Ag+. In addition, a good reversibility after five cycles of quenching and regeneration was obtained. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41759.

Switchable plasmon-induced transparency in gold nanoarrays on vanadium dioxide film

A proof-of-concept demonstration of switchable plasmon-induced transparency is presented in gold (Au) dolmen structures on a vanadium dioxide (VO2) thin film. The dolmen structures were made by a combination of high-resolution electron-beam lithography on VO2 films deposited by electron-beam evaporation. A 100 nm (160 meV) modulation of the plasmon resonance of the dolmen structure due to the phase transition of the vanadium dioxide is observed. The plasmon resonance width is a factor 2–3 narrower than what was observed for Au nanodisks on a VO2 film in previous studies, due to the interference between the bright and dark modes of the plasmon structure. This experiment shows how one can combine a phase-change material with multielement plasmonic nanostructures to optimize the performance of optical switches and sensors based on metamaterial structures.

Effects of mechanical and geometric properties of adhesive layer on performance of metal-coated optical fiber sensors

The concept underlying metal-coated optical fiber sensors (MCOFSs) is to evaluate the maximum strains previously experienced by host structures from the residual strains induced by an elasto-plastic metal coating. The performances of MCOFSs are altered by the selection of an adhesive as well as the geometric parameters of the adhesive layer. To investigate their effects on sensor performance, a finite element (FE) model was proposed and verified by experiments involving three different adhesives using metal-coated fiber Bragg grating (FBG) sensors. The strain transfer coefficients, the residual strains, and the sensitivity coefficients for the strain level were calculated to examine the influence of the parameters through a finite element analysis (FEA). We found that the nonlinear and plastic properties of the adhesive should be considered to achieve accurate estimation when evaluating the maximum host strains from the residual strains. Moreover, small underlying adhesive thickness and short bonding length are favorable for a MCOFS with 10mm gauge length. Finally, we presented a relationship (among the residual strain, bonding length of MCOFSs, and the maximum host strains) that helps to quantitatively evaluate the maximum host strains from the residual strains.

Towards more accurate microcavity sensors: maximum likelihood estimation applied to a combination of quality factor and wavelength shifts

Optical microcavities are widely used for biological and chemical sensing applications. In these devices, a sensing event is estimated by measuring the shift in the resonant wavelength, or in the quality factor of the microcavity. However, all published works to date only use one of these measures to estimate the sensing event. Here, we show that the estimation accuracy of a sensing event can be improved by employing a combination of both the quality factor and the resonant wavelength measurements in a microcavity sensor. We further demonstrate an experimental application of this model by introducing a refractive index change for a microtoroidal cavity sensor immersed in a liquid. By further using the finite element method simulations in conjunction with the estimator model, we show the existence of three distinct measurement regimes as a function of the quality factor of the microcavity. Finally, the estimator model is extended to develop a sensing metric to compare performance of optical or non-optical sensors.

Comparison of optical fiber Bragg grating hydrogen sensors with Pd-based thin films and sol–gel WO3 coatings

Pd-based thin films and sol–gel WO3 coatings are two kinds of hydrogen sensitive elements used in hydrogen concentration sensing and detection. Optical fiber hydrogen sensors are very promising solutions for flammable hydrogen detection, when the sensitive materials are integrated with optical fiber sensors. This paper reviews the sensing performance of optical fiber hydrogen sensors with these two sensitive materials, which are developed at the National Engineering Laboratory for Optical Fiber Sensing Technologies in Wuhan University of Technology.

Investigation of the performance of an SPR-based optical fiber sensor using finite-difference time domain

Finite-difference time domain (FDTD) method was used to investigate the performance of surface plasmon resonance (SPR)-based optical fiber sensors. The results show that the performance of the fiber sensor can be optimized by choosing a proper combination of metal layer thickness of 40–60 nm and residual cladding thickness of 400–500 nm. Furthermore, the roughness effect of the gold surface layering the fiber sensor is significant in rough surfaces when sigma rms is greater than 5 nm or correlation length is lower than 100 nm.

Efficient Optical Pattern Detection for Microcavity Sensors Based Lab-on-a-Chip

A framework of optical lab-on-a-chip using porous silicon microcavity membrane is presented in this paper. With measured results of the membrane, reflectance spectra detection is designed and implemented on FPGA. We manage to detect the shift of the resonant dip to distinguish target molecule solution of different concentration. To evaluate the feasibility of lab-on-a-chip, we further model the cost and performance of on-chip optical sensors and data processing system. The novel optical lab-on-a-chip will enable detection of biological samples at a much higher sensitivity than classic electrochemical methods. The efficient detecting algorithm will ensure the speed of pattern detection even when the lab-on-a-chip system has to deal with data from multiple channels.

Performances of different metals in optical fibre-based surface plasmon resonance sensor

The capability of various metals used in optical fibre-based surface plasmon resonance (SPR) sensing is studied theoretically. Four metals, gold (Au), silver (Ag), copper (Cu) and aluminium (Al) are considered for the present study. The performance of the optical fibre-based SPR sensor with four different metals is obtained numerically and compared in detail. The performance of optical fibre-based SPR sensor has been analysed in terms of sensitivity, signal-to-noise (SNR) ratio and quality parameter. It is found that the performance of optical fibre-based SPR sensor with Au metal is better than that of the other three metals. The sensitivity of the optical fibre-based SPR sensor with 50 nm thick and 10 mm long Au metal film of exposed sensing region is 2.373 μm/RIU with good linearity, SNR is 0.724 and quality parameter is 48.281 RIU − 1. The thickness of the metal film and the length of the exposed sensing region of the optical fibre-based SPR sensor for each metal are also optimized.

Three-photon upconversion and optical thermometry characterization of Er3+:Yb3+ co-doped yttrium silicate powders

The effect of the presence of ytterbium (Yb3+) on the upconversion (UC) emission of erbium (Er3+) in yttrium silicate crystalline ceramic powders prepared by combustion synthesis was investigated under continuous wave (cw) near-infrared (λ=975nm) laser excitation. UC emission bands centered at ∼380, ∼410, ∼480, ∼530, ∼555 and ∼660nm were identified, respectively, as 4f–4f transitions from Er3+ excited states 4G11/2, 2H9/2, 4F7/2, 2H11/2, 4S3/2 and 4F9/2. Aiming to photonics applications, the optical temperature sensor performance of this material was also investigated by measurements of the fluorescence intensity ratio of the signals at 530 and 555nm in the temperature range of 300–600K. The maximum sensor sensitivity found was ∼56×10−4K−1. We observed that the maximum sensor sensitivity increased to ∼70×10−4K−1 when the cw laser excitation was replaced by a pulsed (∼5ns) laser excitation. The change in sensor sensitivity is attributed to optical heating of the sample that occurs under cw excitation.

A methodology for identification and localization of partial discharge sources using optical sensors

The present work represents a methodology to detect the location of single as well as multiple Partial Discharge (PD) sources by optical method and to investigate the performance of optical sensors for this purpose. An experimental setup has been arranged in the laboratory for generation of PDs, optical sensing and analysis of the recorded signals obtained from multiple optical sensors. The analysis results prove the effectiveness of the methodology using optical sensors to find whether PD is occurring at single location or multiple locations. For identification of PD locations pattern recognition technique has been utilized by considering the received optical energy as a feature. For feature selection and classification two techniques have been evaluated, viz. Gaussian Mixture Model (GMM) and Support Vector Machine (SVM), and both have shown promising performance. SVM in regression mode was used for identification of unknown PD location/locations. In this case average accuracy obtained was 92.6% when PD is occurring at one location and 80.1% when PD is occurring at two locations. The obtained results indicate that, the proposed methodology can be used to locate partial discharges in high voltage equipment where the optical signals due to discharges find a path to get radiated towards the outer surface.

辐射对光纤传感器性能影响的研究进展

辐射对光纤传感器性能影响的研究进展

Micro/nanofiber optical sensors

This chapter considers applications of MNFs and photonic devices that can be fabricated from or using MNFs as sensors that detect changes in the ambient medium by monitoring changes in the transmission power of light propagation through MNFs. The changes in the medium may be caused by variation in temperature, radiation, concentration of chemical or biological species, microparticles, etc. As has been described in Chapter 2, an electromagnetic field mode supported by an MNF has an evanescent part, which is distributed outside the MNF. The evanescent part may include a significant part of the propagating mode and, therefore, can be very sensitive to changes which take place at or near the surface of the MNF. Fig. 6.1 illustrates the principle of optical MNF sensor performance. An MNF either directly performs sensing (Figs. 6.1(a) — (f)) or serves as a waveguide, which connects a photonic sensor to the source and the detector of light (Figs. 6.1(c) and (g) — (k)). Fig. 6.1(a) depicts the simplest uncoated MNF sensor, whose thickness is usually less than the radiation wavelength. For this sensor it is assumed that a significant fraction of the fundamental mode of radiation propagates in the ambient medium. Transmission power of this sensor changes with its optical properties, which depend on the properties of the ambient medium. The sensor illustrated in Fig. 6.1(b) is an MNF, which is coated with chemical or biological reagents. The reagents are supposed to be sensitive to selective chemical or biological species. Fig. 6.1(c) illustrates a generic photonic sensor having MNF input and output. Figs. 6.1(d) — (j) depict the straight MNF sensor[1-8], the MNF loop sensor[9-12], the MNF coil sensor[12-18], the MNF/microsphere sensor[19-30], the MNF/microdisk sensor[31-34], the MNF/microcylinder sensor[4], and the MNF/microcapillary sensor[35-39], respectively. Fig. 6.1(k) illustrates the possible assembly of several MNF-based sensors. The performance of sensors shown in Fig. 6.1 can either be dependent or independent of the interaction of the ambient medium with the evanescent field. The sensors of the first group are devices whose transmission characteristics vary due to changes in optical and/or geometrical properties of the MNF itself and/or of the mode propagating along the MNF. Changes of this kind can be caused by incident radiation, variation of temperature, mechanical vibration, etc. For example, an MNF loop resonator illustrated in Fig. 6.1(e) has been demonstrated as a fast temperature sensor and infrared radiation sensor[9]. The simplest sensor of the second group is a single MNF shown in Fig. 6.1(b), which can detect changes caused by proximity of chemical/biological species and microparticles at the MNF surface. This sensor was demonstrated for silica MNFs[1-7] and polymer MNFs[8].

An analysis of the knife-edge method for on-orbit MTF estimation of optical sensors

Modulation Transfer Function (MTF) is a widely used parameter to assess the on-orbit performance of satellite optical sensors. As one of the most widely used on-orbit MTF estimation methods, the target of knife-edge method is relatively easy to deploy or select, and its data processing is straightforward and can achieve reasonable estimation results. Unfortunately, its estimation accuracy is greatly influenced by many factors and not enough emphasis has been placed on the quantitative analysis of their influences, which limits the creditability and application of estimation result. Therefore, this paper focuses on the implementation and accuracy analysis of the knife-edge method. It begins with a discussion on the necessity and importance of carrying out on-orbit MTF estimation, and the advantages and unresolved problems of the knife-edge method are also analysed. Secondly, the principle, requirements of target and basic data processing steps of the knife-edge method are presented. Thirdly, the influences of major factors affecting the accuracy of MTF estimation result based on the knife-edge method is emphasized using theory analysis and simulation experiments. The analysed factors include atmosphere, the incline angle of target, the contrast and random noise of target, the edge detection accuracy, and the Edge Response Function (ERF) curve-fitting model. The analysis results can provide pivotal guidelines to implement on-orbit MTF estimation based on the knife-edge method. The overall accuracy of on-orbit MTF estimation based on the knife-edge method is also explored using simulation experiments, which provide statistics about the accuracy of MTF estimation results. Finally, an experiment using three knife-edge targets in SPOT-5/Pan image of Dalian airport with different contrasts, signal-to-noise ratios and incline angles is carried out, and its relatively consistent results strongly support the validity of the knife-edge method.

Use of fibre sensors for temperature measurement in subsea infrastructure to monitor flow-loop cool-down

The interest in using optical sensors as replacements for typical electrical sensors in the oil and gas industry has increased as the potential benefits and reliability of such technologies become more established. Presented here are the results from initial tests using optical temperature sensors to monitor the effectiveness of subsea tree insulation to retain heat within the flow-loops of a Christmas Tree to prevent hydrate formation during system cool-down. Initial tests were carried out to compare the optical fibre sensor performance with traditional electrical thermocouples. Suggestions for further development and future tests are also presented and discussed.

Acoustic data fusion devoted to underwater vegetation mapping

This paper presents research tasks conducted by SEMANTIC TS, in collaboration with GESMA, aimed to develop a mapping method for underwater vegetation lying on seabed. First stage is to develop a method for detecting and characterizing vegetation on the seabed using the acoustic response from a conventional single beam echo sounder. This new method is then operated simultaneously with multibeam sonar producing micro-relief information and side scan sonar providing gray scale levels associated with bottom reflectivity. Then fusion of these three data is processed. We show efficiency of these multisensor data fusion concept to get very precise seabed vegetation mapping in a way reducing truth control (video and diving investigations). Sensors and method accuracy allow obtaining, like in biomedical field, real 3D scan pictures of seabed vegetation. This study is first applied to posidonia and cymodocea, which play a key role in Mediterranean's echosystem. Then, extension of the method is investigated to address laminaria which may significantly affect the performance of acoustic and optical sensors used for sea-mines detection and this paper presents results of data fusion mapping on an Atlantic sea area covered by luminaria, studied and well known by the CEVA.

地盤変形観測のためのPE 管光ファイバセンサの開発

The optical fiber sensing methods have been utilized for observation of ground deformation. In this study, performance of a new PE-Pipe optical fiber sensor, developed to increase sensing accuracy, was verified. Firstly, a heat fusion method to connect optical fibers to PE-pipe surface firmly was developed. Next, measurement sensitivity of the PE-pipe optical fiber sensor was verified by comparing pipe strains obtained by strain gages and those by optical fibers through PE-pipe bending experiment. Finally, it is ensured that the PE-pipe optical fiber sensor is applicable for investigation of small range ground deformation through an uneven ground settlement experiment for the PE-pipe sensor.

On the performance quantification of resonant refractive index sensors

Refractive index (RI) sensors based on optical resonance techniques are receiving a high degree of attention because of the need to develop simple, low-cost, high-throughput detection technologies for a number of applications. While the sensing mechanism of most of the reported RI sensors is similar, the construction is quite different from technique to technique. It is desirable to have a uniform mechanism for comparing the various RI sensing techniques, but to date there exists a degree of variation as to how the sensing performance is quantified. Here we set forth a rigorous definition for the detection limit of resonant RI sensors that accounts for all parameters that affect the detection performance. Our work will enable a standard approach for quantifying and comparing the performance of optical resonance-based RI sensors. Additionally, it will lead to design strategies for performance improvement of RI sensors.

Comparisons of optical pH and dissolved oxygen sensors with traditional electrochemical probes during mammalian cell culture

Small-scale upstream bioprocess development often occurs in flasks and multi-well plates. These culturing platforms are often not equipped to accurately monitor and control critical process parameters; thus they may not yield conditions representative of manufacturing. In response, we and others have developed optical sensors that enable small-scale process monitoring. Here we have compared two parameters critical to control in industrial cell culture, pH and dissolved oxygen (DO), measured with our optical sensors versus industrially accepted electrochemical probes. For both optical sensors, agreement with the corresponding electrochemical probe was excellent. The Pearson Correlations between the optical sensors and electrochemical probes were 98.7% and 99.7%, for DO and pH, respectively. Also, we have compared optical pH sensor performance in regular (320 mOsm/kg) and high-osmolality (450 mOsm/kg) cell culture media to simulate the increase in osmolality in pH-controlled cultures. Over a pH range of 6.38-7.98 the average difference in pH readings in the two media was 0.04 pH units. In summary, we have demonstrated that these optical sensors agree well with standard electrochemical probes. The accuracy of the optical probes demonstrates their ability to detect potential parameter drift that could have significant impact on growth, production kinetics, and protein product quality. We have also shown that an increase in osmolality that could result from controlling pH or operating the reactor in fed-batch mode has an insignificant impact on the functionality of the pH patches.

Sensitivity Analysis of a Proposed Novel Opto-Nano-Mechanical Photodetector for Improving the Performance of LIDAR and Local Optical Sensors

We propose a novel approach to the development of a new generation of optical sensors with enhanced detection sensitivity for chemical species. The novelty comes from combining an extremely high Q cantilever sensor with an already well established very sensitive technique, frequency modulation (FM) spectroscopy. In existing implementations, this inherent sensitivity is limited by the inadequacy of current state-of-the-art electronic filters to differentiate the weak amplitude modulated (AM)signal from the inevitable high-frequency laser noise, a consequence of the deterioration in the quality factor with increasing frequency exhibited by these filters. Our approach combines FM techniques with the rapidly advancing technology of nano-mechanical resonator (cantilever) development. Here a cantilever functions as both a sensitive photodetector and a high-quality spectral or temporal filter. These ultra-low mass devices enable detection of the photon momentum rather than conventional detection by photon energy. At least one order of magnitude enhancement appears feasible with existing cantilever technology.