E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Special Issue "Optical Sensing and Imaging, from UV to THz Range"

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

Deadline for manuscript submissions: closed (31 January 2019)

Special Issue Editors

Guest Editor
Prof. Dr. Vincenzo Spagnolo

PolySense Lab—Department of Physics, Politecnico di Bari, Via Amendola 173, 70126 Bari, Italy
Website | E-Mail
Phone: +39 0805442237
Fax: +39 0805442219
Interests: optoacoustic gas sensing; Quantum Cascade lasers; spectroscopic techniques for real-time device monitoring; thermal modeling of optoelectronic devices
Guest Editor
Dr. Dragan Indjin

Reader (Associate Professor) in Optoelectronics and Nanoscale Electronics, Pollard Institute, School of Electronic and Electrical Engineering, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
Website | E-Mail
Interests: optical absorption; semiconductor lasers; mid-infrared and terahertz lasers and detectors; quantum-cascade lasers; infrared and terahertz sensing and imaging
Guest Editor
Prof. Dr. Weidong Chen

Laboratoire de Physico-Chimie de l'Atmosphère, Université du Littoral Côte d'Opale, 189A, Avenue Maurice Schumann 59140 Dunkerque, France
Website | E-Mail
Interests: developments of photonic instrumentation involving high-sensitivity spectroscopic techniques for applied spectroscopy; Optical metrology of key atmospheric species (trace gases and aerosols) for applications in atmospheric and environmental sciences; Optical parametric laser source generation by frequency conversion and its applications to applied spectroscopy

Special Issue Information

Dear Colleagues,

The recent advance in optical sources and detectors has opened up new opportunities for sensing and imaging techniques and applications. This 2018 Special Issue of the journal, Sensors, entitled “Optical Sensing and Imaging, from UV to THz Range” will focus on all aspects of the research and development related to these areas. Original research papers that focus on the optical sources developments for sensing, the design and experimental verification of new sensors and imaging systems, as well as papers that focus on their field-testing and campaign measurement, are welcome. Both reviews and original research articles will be published. Reviews should provide an up-to-date well-balanced overview of the current state of the art in a particular field and include main results from other groups. We look forward to and welcome your participation in this Special Issue.

Prof. Dr. Vincenzo Spagnolo
Prof. Dr. Dragan Indjin
Prof. Dr. Weidong Chen
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Optical sources for sensing
  • Sensing mechanisms
  • Gas and liquid sensors
  • Fiber optic sensors
  • Chemical sensors
  • Bio-medical sensors
  • Physical sensors
  • Imaging
  • Spectral imaging
  • Multispectral imaging
  • Chemical imaging
  • Imaging spectroscopy

Published Papers (12 papers)

View options order results:
result details:
Displaying articles 1-12
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle Quartz Enhanced Photoacoustic Spectroscopy Based on a Custom Quartz Tuning Fork
Sensors 2019, 19(6), 1362; https://doi.org/10.3390/s19061362
Received: 14 February 2019 / Revised: 14 March 2019 / Accepted: 14 March 2019 / Published: 19 March 2019
PDF Full-text (2747 KB) | HTML Full-text | XML Full-text
Abstract
We have designed and fabricated a custom quartz tuning fork (QTF) with a reduced fundamental frequency; a larger gap between the prongs; and the best quality factor in air at atmospheric conditions ever reported, to our knowledge. Acoustic microresonators have been added to [...] Read more.
We have designed and fabricated a custom quartz tuning fork (QTF) with a reduced fundamental frequency; a larger gap between the prongs; and the best quality factor in air at atmospheric conditions ever reported, to our knowledge. Acoustic microresonators have been added to the QTF in order to enhance the sensor sensitivity. We demonstrate a normalized noise equivalent absorption (NNEA) of 3.7 × 10−9 W.cm−1.Hz−1/2 for CO2 detection at atmospheric pressure. The influence of the inner diameter and length of the microresonators has been studied, as well as the penetration depth between the QTF’s prongs. We investigated the acoustic isolation of our system and measured the Allan deviation of the sensor. Full article
(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)
Figures

Figure 1

Open AccessArticle Dual-Gas Sensor of CH4/C2H6 Based on Wavelength Modulation Spectroscopy Coupled to a Home-Made Compact Dense-Pattern Multipass Cell
Sensors 2019, 19(4), 820; https://doi.org/10.3390/s19040820
Received: 10 January 2019 / Revised: 2 February 2019 / Accepted: 14 February 2019 / Published: 17 February 2019
PDF Full-text (4108 KB) | HTML Full-text | XML Full-text
Abstract
A sensitive dual-gas sensor for the detection of CH4 and C2H6 is demonstrated. Two tunable semiconductor lasers operating at 1.653 μm (for CH4 monitoring) and 1.684 μm (for C2H6) were used as the light [...] Read more.
A sensitive dual-gas sensor for the detection of CH4 and C2H6 is demonstrated. Two tunable semiconductor lasers operating at 1.653 μm (for CH4 monitoring) and 1.684 μm (for C2H6) were used as the light source for spectroscopic measurements of CH4 and C2H6. Long-path absorption in a home-made compact dense-pattern multipass cell (Leff = 29.37 m) was employed, combined with wavelength modulation and second harmonic detection. Simultaneous detection of CH4 and C2H6 was achieved by separated wavelength modulations of the two lasers. Modulation frequencies and amplitudes were optimized for sensitivity detection of CH4 and C2H6 simultaneously. The dual-gas sensor exhibits 1σ detection limits of 1.5 ppbv for CH4 in 140 s averaging time and 100 ppbv for C2H6 in 200 s. Full article
(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)
Figures

Figure 1

Open AccessArticle SWIR AOTF Imaging Spectrometer Based on Single-pixel Imaging
Sensors 2019, 19(2), 390; https://doi.org/10.3390/s19020390
Received: 26 December 2018 / Revised: 15 January 2019 / Accepted: 15 January 2019 / Published: 18 January 2019
PDF Full-text (5538 KB) | HTML Full-text | XML Full-text
Abstract
An acousto-optic tunable filter (AOTF) is a new type of mono-wavelength generator, and an AOTF imaging spectrometer can obtain spectral images of interest. However, due to the limitation of AOTF aperture and acceptance angle, the light passing through the AOTF imaging spectrometer is [...] Read more.
An acousto-optic tunable filter (AOTF) is a new type of mono-wavelength generator, and an AOTF imaging spectrometer can obtain spectral images of interest. However, due to the limitation of AOTF aperture and acceptance angle, the light passing through the AOTF imaging spectrometer is weak, especially in the short-wave infrared (SWIR) region. In weak light conditions, the noise of a non-deep cooling mercury cadmium telluride (MCT) detector is high compared to the camera response. Thus, effective spectral images cannot be obtained. In this study, the single-pixel imaging (SPI) technique was applied to the AOTF imaging spectrometer, which can obtain spectral images due to the short-focus lens that collects light into a small area. In our experiment, we proved that the irradiance of a short-focus system is much higher than that of a long-focus system in relation to the AOTF imaging spectrometer. Then, an SPI experimental setup was built to obtain spectral images in which traditional systems cannot obtain. This work provides an efficient way to detect spectral images from 1000 to 2200 nm. Full article
(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)
Figures

Figure 1

Open AccessArticle An Optical Fiber Sensor Based on La2O2S:Eu Scintillator for Detecting Ultraviolet Radiation in Real-Time
Sensors 2018, 18(11), 3754; https://doi.org/10.3390/s18113754
Received: 4 September 2018 / Revised: 26 October 2018 / Accepted: 28 October 2018 / Published: 2 November 2018
PDF Full-text (3807 KB) | HTML Full-text | XML Full-text
Abstract
A novel ultraviolet (UV) optical fiber sensor (UVOFS) based on the scintillating material La2O2S:Eu has been designed, tested, and its performance compared with other scintillating materials and other conventional UV detectors. The UVOFS is based on PMMA (polymethyl methacrylate) [...] Read more.
A novel ultraviolet (UV) optical fiber sensor (UVOFS) based on the scintillating material La2O2S:Eu has been designed, tested, and its performance compared with other scintillating materials and other conventional UV detectors. The UVOFS is based on PMMA (polymethyl methacrylate) optical fiber which includes a scintillating material. Scintillating materials provide a unique opportunity to measure UV light intensity even in the presence of strong electromagnetic interference. Five scintillating materials were compared in order to select the most appropriate one for the UVOFS. The characteristics of the sensor are reported, including a highly linear response to radiation intensity, reproducibility, temperature response, and response time (to pulsed light) based on emission from a UV source (UV fluorescence tube) centered on a wavelength of 308 nm. A direct comparison with the commercially available semiconductor-based UV sensor proves the UVOFS of this investigation shows superior performance in terms of accuracy, long-term reliability, response time and linearity. Full article
(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)
Figures

Figure 1

Open AccessArticle Sub-Diffraction Visible Imaging Using Macroscopic Fourier Ptychography and Regularization by Denoising
Sensors 2018, 18(9), 3154; https://doi.org/10.3390/s18093154
Received: 17 August 2018 / Revised: 9 September 2018 / Accepted: 16 September 2018 / Published: 18 September 2018
PDF Full-text (3177 KB) | HTML Full-text | XML Full-text
Abstract
Imaging past the diffraction limit is of significance to an optical system. Fourier ptychography (FP) is a novel coherent imaging technique that can achieve this goal and it is widely used in microscopic imaging. Most phase retrieval algorithms for FP reconstruction are based [...] Read more.
Imaging past the diffraction limit is of significance to an optical system. Fourier ptychography (FP) is a novel coherent imaging technique that can achieve this goal and it is widely used in microscopic imaging. Most phase retrieval algorithms for FP reconstruction are based on Gaussian measurements which cannot extend straightforwardly to long range, sub-diffraction imaging setup because of laser speckle noise corruption. In this work, a new FP reconstruction framework is proposed for macroscopic visible imaging. When compared with existing research, the reweighted amplitude flow algorithm is adopted for better signal modeling, and the Regularization by Denoising (RED) scheme is introduced to reduce the effects of speckle. Experiments demonstrate that the proposed method can obtain state-of-the-art recovered results on both visual and quantitative metrics without increasing computation cost, and it is flexible for real imaging applications. Full article
(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)
Figures

Figure 1

Open AccessArticle New Digital Plug and Imaging Sensor for a Proton Therapy Monitoring System Based on Positron Emission Tomography
Sensors 2018, 18(9), 3006; https://doi.org/10.3390/s18093006
Received: 27 July 2018 / Revised: 1 September 2018 / Accepted: 2 September 2018 / Published: 8 September 2018
PDF Full-text (10933 KB) | HTML Full-text | XML Full-text
Abstract
One of the most challenging areas of sensor development for nuclear medicine is the design of proton therapy monitoring systems. Sensors are operated in a high detection rate regime in beam-on conditions. We realized a prototype of a monitoring system for proton therapy [...] Read more.
One of the most challenging areas of sensor development for nuclear medicine is the design of proton therapy monitoring systems. Sensors are operated in a high detection rate regime in beam-on conditions. We realized a prototype of a monitoring system for proton therapy based on the technique of positron emission tomography. We used the Plug and Imaging (P&I) technology in this application. This sensing system includes LYSO/silicon photomultiplier (SiPM) detection elements, fast digital multi voltage threshold (MVT) readout electronics and dedicated image reconstruction algorithms. In this paper, we show that the P&I sensor system has a uniform response and is controllable in the experimental conditions of the proton therapy room. The prototype of PET monitoring device based on the P&I sensor system has an intrinsic experimental spatial resolution of approximately 3 mm (FWHM), obtained operating the prototype both during the beam irradiation and right after it. The count-rate performance of the P&I sensor approaches 5 Mcps and allows the collection of relevant statistics for the nuclide analysis. The measurement of both the half life and the relative abundance of the positron emitters generated in the target volume through irradiation of 10 10 protons in approximately 15 s is performed with 0.5% and 5 % accuracy, respectively. Full article
(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)
Figures

Figure 1

Open AccessArticle Quartz-Enhanced Photoacoustic Spectroscopy Sensor with a Small-Gap Quartz Tuning Fork
Sensors 2018, 18(7), 2047; https://doi.org/10.3390/s18072047
Received: 10 May 2018 / Revised: 24 June 2018 / Accepted: 25 June 2018 / Published: 27 June 2018
Cited by 3 | PDF Full-text (3293 KB) | HTML Full-text | XML Full-text
Abstract
A highly sensitive quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor based on a custom quartz tuning fork (QTF) with a small-gap of 200 μm was demonstrated. With the help of the finite element modeling (FEM) simulation software COMSOL, the change tendency of the QEPAS signal [...] Read more.
A highly sensitive quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor based on a custom quartz tuning fork (QTF) with a small-gap of 200 μm was demonstrated. With the help of the finite element modeling (FEM) simulation software COMSOL, the change tendency of the QEPAS signal under the influence of the laser beam vertical position and the length of the micro-resonator (mR) were calculated theoretically. Water vapor (H2O) was selected as the target analyte. The experimental results agreed well with those of the simulation, which verified the correctness of the theoretical model. An 11-fold signal enhancement was achieved with the addition of an mR with an optimal length of 5 mm in comparison to the bare QTF. Finally, the H2O-QEPAS sensor, which was based on a small-gap QTF, achieved a minimum detection limit (MDL) of 1.3 ppm, indicating an improvement of the sensor performance when compared to the standard QTF that has a gap of 300 μm. Full article
(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)
Figures

Figure 1

Open AccessArticle Flash Smelting Copper Concentrates Spectral Emission Measurements
Sensors 2018, 18(7), 2009; https://doi.org/10.3390/s18072009
Received: 15 May 2018 / Revised: 14 June 2018 / Accepted: 14 June 2018 / Published: 22 June 2018
PDF Full-text (4402 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we report on spectral features emitted by a reaction shaft occurring in flash smelting of copper concentrates containing sulfide copper minerals such as chalcopyrite (CuFeS2), bornite (Cu5FeS4) and pyrite (FeS2). Different combustion [...] Read more.
In this paper, we report on spectral features emitted by a reaction shaft occurring in flash smelting of copper concentrates containing sulfide copper minerals such as chalcopyrite (CuFeS2), bornite (Cu5FeS4) and pyrite (FeS2). Different combustion conditions are addressed, such as sulfur-copper ratio and oxygen excess. Temperature and spectral emissivity features are estimated for each case by using the two wavelength method and radiometric models. The most relevant results have shown an increasing intensity behavior for higher sulfur-copper ratios and oxygen contents, where emissivity is almost constant along the visible spectrum range for all cases, which validates the gray body assumption. CuO and FeO emission line features along the visible spectrum appear to be a sensing alternative for describing the combustion reactions. Full article
(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)
Figures

Figure 1

Open AccessArticle Filter Selection for Optimizing the Spectral Sensitivity of Broadband Multispectral Cameras Based on Maximum Linear Independence
Sensors 2018, 18(5), 1455; https://doi.org/10.3390/s18051455
Received: 26 February 2018 / Revised: 1 May 2018 / Accepted: 4 May 2018 / Published: 7 May 2018
PDF Full-text (4734 KB) | HTML Full-text | XML Full-text
Abstract
Previous research has shown that the effectiveness of selecting filter sets from among a large set of commercial broadband filters by a vector analysis method based on maximum linear independence (MLI). However, the traditional MLI approach is suboptimal due to the need to [...] Read more.
Previous research has shown that the effectiveness of selecting filter sets from among a large set of commercial broadband filters by a vector analysis method based on maximum linear independence (MLI). However, the traditional MLI approach is suboptimal due to the need to predefine the first filter of the selected filter set to be the maximum ℓ2 norm among all available filters. An exhaustive imaging simulation with every single filter serving as the first filter is conducted to investigate the features of the most competent filter set. From the simulation, the characteristics of the most competent filter set are discovered. Besides minimization of the condition number, the geometric features of the best-performed filter set comprise a distinct transmittance peak along the wavelength axis of the first filter, a generally uniform distribution for the peaks of the filters and substantial overlaps of the transmittance curves of the adjacent filters. Therefore, the best-performed filter sets can be recognized intuitively by simple vector analysis and just a few experimental verifications. A practical two-step framework for selecting optimal filter set is recommended, which guarantees a significant enhancement of the performance of the systems. This work should be useful for optimizing the spectral sensitivity of broadband multispectral imaging sensors. Full article
(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)
Figures

Figure 1

Open AccessArticle Classification and Discrimination of Different Fungal Diseases of Three Infection Levels on Peaches Using Hyperspectral Reflectance Imaging Analysis
Sensors 2018, 18(4), 1295; https://doi.org/10.3390/s18041295
Received: 6 March 2018 / Revised: 8 April 2018 / Accepted: 12 April 2018 / Published: 23 April 2018
Cited by 1 | PDF Full-text (960 KB) | HTML Full-text | XML Full-text
Abstract
Peaches are susceptible to infection from several postharvest diseases. In order to control disease and avoid potential health risks, it is important to identify suitable treatments for each disease type. In this study, the spectral and imaging information from hyperspectral reflectance (400~1000 nm) [...] Read more.
Peaches are susceptible to infection from several postharvest diseases. In order to control disease and avoid potential health risks, it is important to identify suitable treatments for each disease type. In this study, the spectral and imaging information from hyperspectral reflectance (400~1000 nm) was used to evaluate and classify three kinds of common peach disease. To reduce the large dimensionality of the hyperspectral imaging, principal component analysis (PCA) was applied to analyse each wavelength image as a whole, and the first principal component was selected to extract the imaging features. A total of 54 parameters were extracted as imaging features for one sample. Three decayed stages (slight, moderate and severe decayed peaches) were considered for classification by deep belief network (DBN) and partial least squares discriminant analysis (PLSDA) in this study. The results showed that the DBN model has better classification results than the classification accuracy of the PLSDA model. The DBN model based on integrated information (494 features) showed the highest classification results for the three diseases, with accuracies of 82.5%, 92.5%, and 100% for slightly-decayed, moderately-decayed and severely-decayed samples, respectively. The successive projections algorithm (SPA) was used to select the optimal features from the integrated information; then, six optimal features were selected from a total of 494 features to establish the simple model. The SPA-PLSDA model showed better results which were more feasible for industrial application. The results showed that the hyperspectral reflectance imaging technique is feasible for detecting different kinds of diseased peaches, especially at the moderately- and severely-decayed levels. Full article
(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)
Figures

Figure 1

Review

Jump to: Research

Open AccessReview Acoustic Detection Module Design of a Quartz-Enhanced Photoacoustic Sensor
Sensors 2019, 19(5), 1093; https://doi.org/10.3390/s19051093
Received: 26 January 2019 / Revised: 17 February 2019 / Accepted: 23 February 2019 / Published: 4 March 2019
PDF Full-text (2033 KB) | HTML Full-text | XML Full-text
Abstract
This review aims to discuss the latest advancements of an acoustic detection module (ADM) based on quartz-enhanced photoacoustic spectroscopy (QEPAS). Starting from guidelines for the design of an ADM, the ADM design philosophy is described. This is followed by a review of the [...] Read more.
This review aims to discuss the latest advancements of an acoustic detection module (ADM) based on quartz-enhanced photoacoustic spectroscopy (QEPAS). Starting from guidelines for the design of an ADM, the ADM design philosophy is described. This is followed by a review of the earliest standard quartz tuning fork (QTF)-based ADM for laboratory applications. Subsequently, the design of industrial fiber-coupled and free-space ADMs based on a standard QTF for near-infrared and mid-infrared laser sources respectively are described. Furthermore, an overview of the latest development of a QEPAS ADM employing a custom QTF is reported. Numerous application examples of four QEPAS ADMs are described in order to demonstrate their reliability and robustness. Full article
(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)
Figures

Figure 1

Open AccessReview Recent Applications of Multispectral Imaging in Seed Phenotyping and Quality Monitoring—An Overview
Sensors 2019, 19(5), 1090; https://doi.org/10.3390/s19051090
Received: 21 January 2019 / Revised: 17 February 2019 / Accepted: 22 February 2019 / Published: 4 March 2019
PDF Full-text (3516 KB) | HTML Full-text | XML Full-text
Abstract
As a synergistic integration between spectroscopy and imaging technologies, spectral imaging modalities have been emerged to tackle quality evaluation dilemmas by proposing different designs with effective and practical applications in food and agriculture. With the advantage of acquiring spatio-spectral data across a wide [...] Read more.
As a synergistic integration between spectroscopy and imaging technologies, spectral imaging modalities have been emerged to tackle quality evaluation dilemmas by proposing different designs with effective and practical applications in food and agriculture. With the advantage of acquiring spatio-spectral data across a wide range of the electromagnetic spectrum, the state-of-the-art multispectral imaging in tandem with different multivariate chemometric analysis scenarios has been successfully implemented not only for food quality and safety control purposes, but also in dealing with critical research challenges in seed science and technology. This paper will shed some light on the fundamental configuration of the systems and give a birds-eye view of all recent approaches in the acquisition, processing and reproduction of multispectral images for various applications in seed quality assessment and seed phenotyping issues. This review article continues from where earlier review papers stopped but it only focused on fully-operated multispectral imaging systems for quality assessment of different sorts of seeds. Thence, the review comprehensively highlights research attempts devoted to real implementations of only fully-operated multispectral imaging systems and does not consider those ones that just utilized some key wavelengths extracted from hyperspectral data analyses without building independent multispectral imaging systems. This makes this article the first attempt in briefing all published papers in multispectral imaging applications in seed phenotyping and quality monitoring by providing some examples and research results in characterizing physicochemical quality traits, predicting physiological parameters, detection of defect, pest infestation and seed health. Full article
(This article belongs to the Special Issue Optical Sensing and Imaging, from UV to THz Range)
Figures

Figure 1

Sensors EISSN 1424-8220 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top