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3 pages, 183 KiB

Open AccessEditorial

Optical Sensors Technology and Applications

by Maria Lepore and Ines Delfino

Sensors 2022, 22(20), 7905; https://doi.org/10.3390/s22207905 - 17 Oct 2022

Cited by 4 | Viewed by 3115

Abstract

Optical methods are non-invasive tools, and their use in various fields, including sensing applications, is continuously increasing, which is thanks to the continuous development of innovative low-cost sources and detectors [...] Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

Research

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13 pages, 2534 KiB

Open AccessArticle

Raman Natural Gas Analyzer: Effects of Composition on Measurement Precision

by Dmitry V. Petrov, Ivan I. Matrosov, Alexey R. Zaripov and Aleksandr S. Tanichev

Sensors 2022, 22(9), 3492; https://doi.org/10.3390/s22093492 - 4 May 2022

Cited by 19 | Viewed by 2903

Abstract

Raman spectroscopy is a promising method for analyzing natural gas due to its high measurement speed and the potential to monitor all molecular components simultaneously. This paper discusses the features of measurements of samples whose composition varies over a wide range (0.005–100%). Analysis [...] Read more.

Raman spectroscopy is a promising method for analyzing natural gas due to its high measurement speed and the potential to monitor all molecular components simultaneously. This paper discusses the features of measurements of samples whose composition varies over a wide range (0.005–100%). Analysis of the concentrations obtained during three weeks of experiments showed that their variation is within the error caused by spectral noise. This result confirms that Raman gas analyzers can operate without frequent calibrations, unlike gas chromatographs. It was found that a variation in the gas composition can change the widths of the spectral lines of methane. As a result, the measurement error of oxygen concentration can reach 200 ppm. It is also shown that neglecting the measurement of pentanes and n-hexane leads to an increase in the calculated concentrations of other alkanes and to errors in the density and heating value of natural gas. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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18 pages, 6754 KiB

Open AccessArticle

Stress Detection of Conical Frustum Windows in Submersibles Based on Polarization Imaging

by Hening Li, Ran Liao, Hailong Zhang, Guoliang Ma, Zhiming Guo, Haibo Tu, Yan Chen and Hui Ma

Sensors 2022, 22(6), 2282; https://doi.org/10.3390/s22062282 - 16 Mar 2022

Cited by 4 | Viewed by 2611

Abstract

Stress detection of the conical frustum window is a very important issue to ensure the safety of deep manned submersibles. In this paper, we propose a method based on polarization imaging to evaluate the stress accumulation and recovery in the conical frustum window. [...] Read more.

Stress detection of the conical frustum window is a very important issue to ensure the safety of deep manned submersibles. In this paper, we propose a method based on polarization imaging to evaluate the stress accumulation and recovery in the conical frustum window. An experimental setup of Mueller matrix polarimetry is built, and the samples are made by referring to the typical conical frustum windows in submersibles. By pressurizing different pressures on the samples, we can find the changes of their Mueller matrix images and further derived polarization parameters. The results show that the polarization parameters can characterize the stress transfer process and the elastic–plastic transformation process of the window under different pressurization pressures. We also use a two-layered wave plate model to simulate the stress distribution in the window, which reveals different performances of the former and latter layers of the window under pressurization. Finally, we use a finite element model to simulate and understand some of the above experimental results. This proposed method is expected to provide new possibilities for monitoring the window stress and further ensure the safety of deep manned submersibles. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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14 pages, 5933 KiB

Open AccessArticle

Stokes Dynamic Polarimeter for Non-Organic and Organic Samples Characterization

by Dora-Luz Almanza-Ojeda, Daniela Rodriguez-Sotelo, Rogelio Castro-Sanchez, Rene Martinez-Celorio and Mario-Alberto Ibarra-Manzano

Sensors 2022, 22(6), 2155; https://doi.org/10.3390/s22062155 - 10 Mar 2022

Cited by 2 | Viewed by 2490

Abstract

The light polarization properties provide relevant information about linear–optical media quality and condition. The Stokes–Mueller formalism is commonly used to represent the polarization properties of the incident light over sample tests. Currently, different Stokes Polarimeters are mainly defined by resolution, acquisition rate, and [...] Read more.

The light polarization properties provide relevant information about linear–optical media quality and condition. The Stokes–Mueller formalism is commonly used to represent the polarization properties of the incident light over sample tests. Currently, different Stokes Polarimeters are mainly defined by resolution, acquisition rate, and light to carry out accurate and fast measurements. This work presents the implementation of an automatic Stokes dynamic polarimeter to characterize non-biological and biological material samples. The proposed system is configured to work in the He-Ne laser beam’s reflection or transmission mode to calculate the Mueller matrix. The instrumentation stage includes two asynchronous photoelastic modulators, two nano-stepper motors, and an acquisition data card at 2% of accuracy. The Mueller matrix is numerically calculated by software using the 36 measures method without requiring image processing. Experiments show the efficiency of the proposed optical array to calculate the Mueller matrix in reflection and transmission mode for different samples. The mean squared error is calculated for each element of the obtained matrix using referenced values of the air and a mirror. A comparison with similar works in the literature validates the proposed optical array. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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16 pages, 5061 KiB

Open AccessArticle

Plasmonic Strain Sensors Based on Au-TiO₂ Thin Films on Flexible Substrates

by Marco S. Rodrigues, Joel Borges and Filipe Vaz

Sensors 2022, 22(4), 1375; https://doi.org/10.3390/s22041375 - 11 Feb 2022

Cited by 5 | Viewed by 3153

Abstract

This study aimed at introducing thin films exhibiting the localized surface plasmon resonance (LSPR) phenomenon with a reversible optical response to repeated uniaxial strain. The sensing platform was prepared by growing gold (Au) nanoparticles throughout a titanium dioxide dielectric matrix. The thin films [...] Read more.

This study aimed at introducing thin films exhibiting the localized surface plasmon resonance (LSPR) phenomenon with a reversible optical response to repeated uniaxial strain. The sensing platform was prepared by growing gold (Au) nanoparticles throughout a titanium dioxide dielectric matrix. The thin films were deposited on transparent polymeric substrates, using reactive magnetron sputtering, followed by a low temperature thermal treatment to grow the nanoparticles. The microstructural characterization of the thin films’ surface revealed Au nanoparticle with an average size of 15.9 nm, an aspect ratio of 1.29 and an average nearest neighbor nanoparticle at 16.3 nm distance. The plasmonic response of the flexible nanoplasmonic transducers was characterized with custom-made mechanical testing equipment using simultaneous optical transmittance measurements. The higher sensitivity that was obtained at a maximum strain of 6.7%, reached the values of 420 nm/ε and 110 pp/ε when measured at the wavelength or transmittance coordinates of the transmittance-LSPR band minimum, respectively. The higher transmittance gauge factor of 4.5 was obtained for a strain of 10.1%. Optical modelling, using discrete dipole approximation, seems to correlate the optical response of the strained thin film sensor to a reduction in the refractive index of the matrix surrounding the gold nanoparticles when uniaxial strain is applied. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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18 pages, 3345 KiB

Open AccessArticle

A Simple Yet Effective Preanalytical Strategy Enabling the Application of Aptamer-Conjugated Gold Nanoparticles for the Colorimetric Detection of Antibiotic Residues in Raw Milk

by Víctor Díaz-García, Braulio Contreras-Trigo, Camila Rodríguez, Pablo Coelho and Patricio Oyarzún

Sensors 2022, 22(3), 1281; https://doi.org/10.3390/s22031281 - 8 Feb 2022

Cited by 11 | Viewed by 3701

Abstract

The misuse of antibiotics in the cattle sector can lead to milk contamination, with concomitant effects on the dairy industry and human health. Biosensors can be applied in this field; however, the influence of the milk matrix on their activity has been poorly [...] Read more.

The misuse of antibiotics in the cattle sector can lead to milk contamination, with concomitant effects on the dairy industry and human health. Biosensors can be applied in this field; however, the influence of the milk matrix on their activity has been poorly studied in light of the preanalytical process. Herein, aptamer-conjugated gold nanoparticles (nanoaptasensors) were investigated for the colorimetric detection in raw milk of four antibiotics used in cattle. The effect of milk components on the colorimetric response of the nanoaptasensors was analyzed by following the selective aggregation of the nanoparticles, using the absorption ratio A₅₂₀/A₇₂₀. A preanalytical strategy was developed to apply the nanoaptasensors to antibiotic-contaminated raw milk samples, which involves a clarification step with Carrez reagents followed by the removal of cations through dilution, chelation (EDTA) or precipitation (NaHCO₃). The colorimetric signals were detected in spiked samples at concentrations of antibiotics as low as 0.25-fold the maximum residue limits (MRLs) for kanamycin (37.5 μg/L), oxytetracycline (25 μg/L), sulfadimethoxine (6.25 μg/L) and ampicillin (1 μg/L), according to European and Chilean legislation. Overall, we conclude that this methodology holds potential for the semiquantitative analysis of antibiotic residues in raw milk obtained directly from dairy farms. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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13 pages, 8489 KiB

Open AccessArticle

Study of Intra-Chamber Processes in Solid Rocket Motors by Fiber Optic Sensors

by Andrey A. Zhirnov, Konstantin V. Stepanov, Stanislav G. Sazonkin, Tatyana V. Choban, Kirill I. Koshelev, Anton O. Chernutsky, Alexey B. Pnev, Alexey O. Novikov and Dmitriy A. Yagodnikov

Sensors 2021, 21(23), 7836; https://doi.org/10.3390/s21237836 - 25 Nov 2021

Cited by 17 | Viewed by 2650

Abstract

In this study, an experimental study of the burning rate of solid fuel in a model solid propellant rocket motor (SRM) E-5-0 was conducted using a non-invasive control method with fiber-optic sensors (FOSs). Three sensors based on the Mach–Zehnder interferometer (MZI), fixed on [...] Read more.

In this study, an experimental study of the burning rate of solid fuel in a model solid propellant rocket motor (SRM) E-5-0 was conducted using a non-invasive control method with fiber-optic sensors (FOSs). Three sensors based on the Mach–Zehnder interferometer (MZI), fixed on the SRM E-5-0, recorded the vibration signal during the entire cycle of solid fuel burning. The results showed that, when using MZI sensors, the non-invasive control of solid fuel burnout is made possible both by recording the time of arrival of the combustion front to the sensor and by analyzing the peaks on the spectrogram of the recorded FOS signal. The main mode of acoustic vibrations of the chamber of the model SRM is longitudinal, and it changes with time, depending on the chamber length. Longitudinal modes of the combustion chamber were detected by MZI only after the combustion front passed its fixing point, and the microphone was unable to register them at all. The results showed that the combustion rate was practically constant after the first second, which was confirmed by the graph of the pressure versus time at the nozzle exit. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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17 pages, 7120 KiB

Open AccessArticle

A Self-Calibration Stitching Method for Pitch Deviation Evaluation of a Long-Range Linear Scale by Using a Fizeau Interferometer

by Xin Xiong, Yuki Shimizu, Hiraku Matsukuma and Wei Gao

Sensors 2021, 21(21), 7412; https://doi.org/10.3390/s21217412 - 8 Nov 2021

Cited by 5 | Viewed by 2684

Abstract

An interferometric self-calibration method for the evaluation of the pitch deviation of scale grating has been extended to evaluate the pitch deviation of the long-range type linear scale by utilizing the stitching interferometry technique. Following the previous work, in which the interferometric self-calibration [...] Read more.

An interferometric self-calibration method for the evaluation of the pitch deviation of scale grating has been extended to evaluate the pitch deviation of the long-range type linear scale by utilizing the stitching interferometry technique. Following the previous work, in which the interferometric self-calibration method was proposed to assess the pitch deviation of the scale grating by combing the first-order diffracted beams from the grating, a stitching calibration method is proposed to enlarge the measurement range. Theoretical analysis is performed to realize the X-directional pitch deviation calibration of the long-range linear scale while reducing the second-order accumulation effect by canceling the influence of the reference flat error in the sub-apertures’ measurements. In this paper, the stitching interferometry theory is briefly reviewed, and theoretical equations of the X-directional pitch deviation stitching are derived for evaluation of the pitch deviation of the long-range linear scale. Followed by the simulation verification, some experiments with a linear scale of 105 mm length from a commercial interferential scanning-type optical encoder are conducted to verify the feasibility of the self-calibration stitching method for the calibration of the X-directional pitch deviation of the linear scale over its whole area. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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15 pages, 2208 KiB

Open AccessArticle

Optimized Classification of Suspended Particles in Seawater by Dense Sampling of Polarized Light Pulses

by Zhiming Guo, Hanbo Deng, Jiajin Li, Ran Liao and Hui Ma

Sensors 2021, 21(21), 7344; https://doi.org/10.3390/s21217344 - 4 Nov 2021

Cited by 4 | Viewed by 2297

Abstract

Suspended particles affect the state and vitality of the marine ecosystem. In situ probing and accurately classifying the suspended particles in seawater have an important impact on ecological research and environmental monitoring. Individual measurement of the optical polarization parameters scattered by the suspended [...] Read more.

Suspended particles affect the state and vitality of the marine ecosystem. In situ probing and accurately classifying the suspended particles in seawater have an important impact on ecological research and environmental monitoring. Individual measurement of the optical polarization parameters scattered by the suspended particles has been proven to be a powerful tool to classify the particulate compositions in seawater. In previous works, the temporal polarized light pulses are sampled and averaged to evaluate the polarization parameters. In this paper, a method based on dense sampling of polarized light pulses is proposed and the experimental setup is built. The experimental results show that the dense sampling method optimizes the classification and increases the average accuracy by at least 16% than the average method. We demonstrate the feasibility of dense sampling method by classifying the multiple types of particles in mixed suspensions and show its excellent generalization ability by multi-classification of the particles. Additional analysis indicates that the dense sampling method basically takes advantage of the high-quality polarization parameters to optimize the classification performance. The above results suggest that the proposed dense sampling method has the potential to probe the suspended particles in seawater in red-tide early warning, as well as sediment and microplastics monitoring. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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10 pages, 2664 KiB

Open AccessArticle

Discrimination of Different Breast Cell Lines on Glass Substrate by Means of Fourier Transform Infrared Spectroscopy

by Maria Lasalvia, Vito Capozzi and Giuseppe Perna

Sensors 2021, 21(21), 6992; https://doi.org/10.3390/s21216992 - 21 Oct 2021

Cited by 6 | Viewed by 1881

Abstract

Fourier transform infrared (FTIR) micro-spectroscopy has been attracting the interest of many cytologists and histopathologists for several years. This is related to the possibility of FTIR translation in the clinical diagnostic field. In fact, FTIR spectra are able to detect changes in biochemical [...] Read more.

Fourier transform infrared (FTIR) micro-spectroscopy has been attracting the interest of many cytologists and histopathologists for several years. This is related to the possibility of FTIR translation in the clinical diagnostic field. In fact, FTIR spectra are able to detect changes in biochemical cellular components occurring when the cells pass to a pathological state. Recently, this interest has increased because it has been shown that FTIR spectra carried out just in the high wavenumber spectral range (2500–4000 cm⁻¹), where information mainly relating to lipids and proteins can be obtained, are able to discriminate cell lines related to different tissues. This possibility allows to perform IR absorption measurements of cellular samples deposited onto microscopy glass slides (widely used in the medical environment) which are transparent to IR radiation only for wavenumber values larger than 2000 cm⁻¹. For these reasons, we show that FTIR spectra in the 2800–3000 cm⁻¹ spectral range can discriminate three different cell lines from breast tissue: a non-malignant cell line (MCF10A), a non-metastatic adenocarcinoma cell line (MCF7) and a metastatic adenocarcinoma cell line (MDA). All the cells were grown onto glass slides. The spectra were discriminated by means of a principal component analysis, according to the PC1 component, whose values have the opposite sign in the pairwise score plots. This result supports the wide studies that are being carried out to promote the translation of the FTIR technique in medical practice, as a complementary diagnostic tool. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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19 pages, 8499 KiB

Open AccessArticle

A New Pattern Quality Assessment Criterion and Defocusing Degree Determination of Laser Speckle Correlation Method

by Wenxin Hu, Zhipeng Sheng, Keyu Yan, Hong Miao and Yu Fu

Sensors 2021, 21(14), 4728; https://doi.org/10.3390/s21144728 - 10 Jul 2021

Cited by 10 | Viewed by 3356

Abstract

The laser speckle correlation method has found widespread application for obtaining information from vibrating objects. However, the resolution and accuracy of the laser speckle correlation method as they relate to the defocusing degree have not been analyzed sufficiently. Furthermore, the possible methods for [...] Read more.

The laser speckle correlation method has found widespread application for obtaining information from vibrating objects. However, the resolution and accuracy of the laser speckle correlation method as they relate to the defocusing degree have not been analyzed sufficiently. Furthermore, the possible methods for speckle pattern quality assessment and enhancement have not been studied. In this study, the resolution and accuracy of the laser speckle correlation method are analyzed, and it is found that they are affected by the defocusing degree and speckle pattern quality, respectively. A new speckle pattern quality criterion combining the mean intensity gradient and frequency spectrum was proposed, called CMZ. The quality of the speckle pattern is higher when the CMZ is closer to zero. The proposed criterion was verified by simulated speckle patterns and real speckle patterns with different speckle sizes, densities, and gray contrasts. In the experimental setup stage, a suitable defocusing degree can be selected based on the resolution requirement and optimal speckle size, and other experimental parameters can be determined according to the CMZ criterion. Rotation and vibration experiments verified the effectiveness of the laser speckle correlation method and confirmed the reliability of the experiment preparation based on proposed CMZ criterion. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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15 pages, 5363 KiB

Open AccessArticle

A Fringe Phase Extraction Method Based on Neural Network

by Wenxin Hu, Hong Miao, Keyu Yan and Yu Fu

Sensors 2021, 21(5), 1664; https://doi.org/10.3390/s21051664 - 28 Feb 2021

Cited by 14 | Viewed by 3016

Abstract

In optical metrology, the output is usually in the form of a fringe pattern, from which a phase map can be generated and phase information can be converted into the desired parameters. This paper proposes an end-to-end method of fringe phase extraction based [...] Read more.

In optical metrology, the output is usually in the form of a fringe pattern, from which a phase map can be generated and phase information can be converted into the desired parameters. This paper proposes an end-to-end method of fringe phase extraction based on the neural network. This method uses the U-net neural network to directly learn the correspondence between the gray level of a fringe pattern and the wrapped phase map, which is simpler than the exist deep learning methods. The results of simulation and experimental fringe patterns verify the accuracy and the robustness of this method. While it yields the same accuracy, the proposed method features easier operation and a simpler principle than the traditional phase-shifting method and has a faster speed than wavelet transform method. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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Review

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25 pages, 55389 KiB

Open AccessReview

Advanced Optical Sensing of Phenolic Compounds for Environmental Applications

by Ines Delfino, Nadia Diano and Maria Lepore

Sensors 2021, 21(22), 7563; https://doi.org/10.3390/s21227563 - 14 Nov 2021

Cited by 11 | Viewed by 3787

Abstract

Phenolic compounds are particularly dangerous due to their ability to remain in the environment for a long period of time and their toxic effects. They enter in the environment in different ways, such as waste from paper manufacturing, agriculture (pesticides, insecticides, herbicides), pharmaceuticals, [...] Read more.

Phenolic compounds are particularly dangerous due to their ability to remain in the environment for a long period of time and their toxic effects. They enter in the environment in different ways, such as waste from paper manufacturing, agriculture (pesticides, insecticides, herbicides), pharmaceuticals, the petrochemical industry, and coal processing. Conventional methods for phenolic compounds detection present some disadvantages, such as cumbersome sample preparation, complex and time-consuming procedures, and need of expensive equipment. Therefore, there is a very large interest in developing sensors and new sensing schemes for fast and easy-to-use methods for detecting and monitoring the phenolic compound concentration in the environment, with special attention to water. Good analytical properties, reliability, and adaptability are required for the developed sensors. The present paper aims at revising the most generally used optical methods for designing and fabricating biosensors and sensors for phenolic compounds. Some selected examples of the most interesting applications of these techniques are also proposed. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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22 pages, 12017 KiB

Open AccessReview

Continuous In-Line Chromium Coating Thickness Measurement Methodologies: An Investigation of Current and Potential Technology

by Adam Jones, Leshan Uggalla, Kang Li, Yuanlong Fan, Ashley Willow, Christopher A. Mills and Nigel Copner

Sensors 2021, 21(10), 3340; https://doi.org/10.3390/s21103340 - 11 May 2021

Cited by 6 | Viewed by 5378

Abstract

Coatings or films are applied to a substrate for several applications, such as waterproofing, corrosion resistance, adhesion performance, cosmetic effects, and optical coatings. When applying a coating to a substrate, it is vital to monitor the coating thickness during the coating process to [...] Read more.

Coatings or films are applied to a substrate for several applications, such as waterproofing, corrosion resistance, adhesion performance, cosmetic effects, and optical coatings. When applying a coating to a substrate, it is vital to monitor the coating thickness during the coating process to achieve a product to the desired specification via real time production control. There are several different coating thickness measurement methods that can be used, either in-line or off-line, which can determine the coating thickness relative to the material of the coating and the substrate. In-line coating thickness measurement methods are often very difficult to design and implement due to the nature of the harsh environmental conditions of typical production processes and the speed at which the process is run. This paper addresses the current and novel coating thickness methodologies for application to chromium coatings on a ferro-magnetic steel substrate with their advantages and limitations regarding in-line measurement. The most common in-line coating thickness measurement method utilized within the steel packaging industry is the X-ray Fluorescence (XRF) method, but these systems can become costly when implemented for a wide packaging product and pose health and safety concerns due to its ionizing radiation. As technology advances, nanometer-scale coatings are becoming more common, and here three methods are highlighted, which have been used extensively in other industries (with several variants in their design) which can potentially measure coatings of nanometer thickness in a production line, precisely, safely, and do so in a non-contact and non-destructive manner. These methods are optical reflectometry, ellipsometry and interferometry. Full article

(This article belongs to the Special Issue Optical Sensors Technology and Applications)

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