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Special Issue "Optical Sensors Technology and Applications"

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Optical Sensors".

Deadline for manuscript submissions: 15 December 2021.

Special Issue Editors

Dr. Maria Lepore
E-Mail Website
Guest Editor
Department of Experimental Medicine, University of Campania Luigi Vanvitelli, 80138 Napoli, Italy
Interests: fluorescence optical methods; vibrational spectroscopies; enzymatic optical biosensing; two-photon microscopy; optical properties of turbid media; biomedical applications
Special Issues, Collections and Topics in MDPI journals
Dr. Ines Delfino
E-Mail Website
Guest Editor
Dipartimento di Scienze Ecologiche e Biologiche, Università della Tuscia, 01100 Viterbo, Italy
Interests: ultrafast optical spectroscopy; Raman and SERS techniques; light scattering methods; multivariate data analysis; optical biosensing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Optical methods are non-invasive tools, and their use in sensing applications is continuously increasing. New optical technologies enable the development of new sensing schemes and devices characterized by superior working parameters (very low detection limit, high specificity and sensitivity) and innovative applicative approaches for quantitatively and qualitatively determining the components of analytes of interest in many fields of application, including pharmaceutical research, medical diagnostics, environmental monitoring, agriculture, industry, food safety, and security. The aim of this Special Issue is to offer an overview of recent advances in optical sensor technology and applications, including source and detection technologies, sensor architectures, sensor performance, and processing approaches and applications. With this aim, original research papers, as well as review articles, will be published to show the diversity of the new developments in these areas and their wide dissemination in these fields. If you require clarifications or wish to discuss your submission in advance, we encourage you to contact us. We look forward to and welcome your participation in this Special Issue.

Prof. Maria Lepore
Prof. Ines Delfino
Guest Editors

Keywords

  • SLS, DLS, and DWS sensing
  • Raman and SERS sensing
  • SEIRA sensing
  • Sensors based on colorimetry, evanescent wave, and infrared spectroscopies
  • Fluorescence
  • Luminescence
  • Absorption
  • Fiber interferometers
  • Microstructured waveguide
  • Grating coupled interferometry (GCI)
  • Resonant waveguide grating (RWG)
  • Surface plasmon resonance (SPR)
  • Localized surface plasmon resonance (LSPR).

Published Papers (8 papers)

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Research

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Article
Study of Intra-Chamber Processes in Solid Rocket Motors by Fiber Optic Sensors
Sensors 2021, 21(23), 7836; https://doi.org/10.3390/s21237836 - 25 Nov 2021
Viewed by 199
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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Article
A Self-Calibration Stitching Method for Pitch Deviation Evaluation of a Long-Range Linear Scale by Using a Fizeau Interferometer
Sensors 2021, 21(21), 7412; https://doi.org/10.3390/s21217412 - 08 Nov 2021
Viewed by 270
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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Article
Optimized Classification of Suspended Particles in Seawater by Dense Sampling of Polarized Light Pulses
Sensors 2021, 21(21), 7344; https://doi.org/10.3390/s21217344 - 04 Nov 2021
Viewed by 338
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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Article
Discrimination of Different Breast Cell Lines on Glass Substrate by Means of Fourier Transform Infrared Spectroscopy
Sensors 2021, 21(21), 6992; https://doi.org/10.3390/s21216992 - 21 Oct 2021
Viewed by 260
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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Article
A New Pattern Quality Assessment Criterion and Defocusing Degree Determination of Laser Speckle Correlation Method
Sensors 2021, 21(14), 4728; https://doi.org/10.3390/s21144728 - 10 Jul 2021
Viewed by 584
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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Article
A Fringe Phase Extraction Method Based on Neural Network
Sensors 2021, 21(5), 1664; https://doi.org/10.3390/s21051664 - 28 Feb 2021
Viewed by 784
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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Review
Advanced Optical Sensing of Phenolic Compounds for Environmental Applications
Sensors 2021, 21(22), 7563; https://doi.org/10.3390/s21227563 - 14 Nov 2021
Viewed by 285
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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Review
Continuous In-Line Chromium Coating Thickness Measurement Methodologies: An Investigation of Current and Potential Technology
Sensors 2021, 21(10), 3340; https://doi.org/10.3390/s21103340 - 11 May 2021
Viewed by 776
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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