Types Of Optical Sensors Research Articles

Effective Application of ICT in Food and Agricultural Sector — Optical Sensing is Mainly Described —

This paper gives an outline of key technologies necessary for science-based agriculture. In order to design future agriculture, present agriculture should be redesigned based on the context of smart agriculture that indicates the overall form of agriculture including a social system while the present precision agriculture shows a technical form of agriculture only. Wireless Sensor Network (WSN) and the various type of optical sensors are assumed to be a basic technology of smart agriculture which intends the harmony with the economic development and sustainable agro-ecosystem. In this paper, the current state and development for the optical sensing for environment and plant are introduced. key words: ICT, optical sensing, infrared spectroscopy, fluorescent X-ray spectroscopy, visible spectroscopy, agricultural products

A Review on Extraction of Lakes from Remotely Sensed Optical Satellite Data with a Special Focus on Cryospheric Lakes

Water on the Earth’s surface is an essential part of the hydrological cycle. Water resources include surface waters, groundwater, lakes, inland waters, rivers, coastal waters, and aquifers. Monitoring lake dynamics is critical to favor sustainable management of water resources on Earth. In cryosphere, lake ice cover is a robust indicator of local climate variability and change. Therefore, it is necessary to review recent methods, technologies, and satellite sensors employed for the extraction of lakes from satellite imagery. The present review focuses on the comprehensive evaluation of existing methods for extraction of lake or water body features from remotely sensed optical data. We summarize pixel-based, object-based, hybrid, spectral index based, target and spectral matching methods employed in extracting lake features in urban and cryospheric environments. To our knowledge, almost all of the published research studies on the extraction of surface lakes in cryospheric environments have essentially used satellite remote sensing data and geospatial methods. Satellite sensors of varying spatial, temporal and spectral resolutions have been used to extract and analyze the information regarding surface water. Multispectral remote sensing has been widely utilized in cryospheric studies and has employed a variety of electro-optical satellite sensor systems for characterization and extraction of various cryospheric features, such as glaciers, sea ice, lakes and rivers, the extent of snow and ice, and icebergs. It is apparent that the most common methods for extracting water bodies use single band-based threshold methods, spectral index ratio (SIR)-based multiband methods, image segmentation methods, spectral-matching methods, and target detection methods (unsupervised, supervised and hybrid). A Synergetic fusion of various remote sensing methods is also proposed to improve water information extraction accuracies. The methods developed so far are not generic rather they are specific to either the location or satellite imagery or to the type of the feature to be extracted. Lots of factors are responsible for leading to inaccurate results of lake-feature extraction in cryospheric regions, e.g. the mountain shadow which also appears as a dark pixel is often misclassified as an open lake. The methods which are working well in the cryospheric environment for feature extraction or landcover classification does not really guarantee that they will be working in the same manner for the urban environment. Thus, in coming years, it is expected that much of the work will be done on object-based approach or hybrid approach involving both pixel as well as object-based technology. A more accurate, versatile and robust method is necessary to be developed that would work independent of geographical location (for both urban and cryosphere) and type of optical sensor.

Experimental observation of a giant Goos-Hänchen shift in graphene using a beam splitter scanning method.

A giant Goos-Hänchen (G-H) shift in graphene has been theoretically predicted by previous research. In this Letter, we present experimental measurements of the G-H shift in graphene, in a total internal reflection condition, using a new method we have named "the beam splitter scanning method." Our results show that a focused light source undergoes significant lateral shift when the polarization of incident light changes from transverse magnetic (TM) to transverse electric (TE) mode, indicating a large G-H shift in graphene that is polarization-dependent. We also observed that the difference in the G-H shift for TM versus TE modes (S(TM)-S(TE)) increases with increasing thickness of graphene material. A maximum difference (S(TM)-S(TE)) of 31.16 μm was observed, which is a significant result. Based on this research, the ability to engineer giant G-H shifts in graphene material has now been experimentally confirmed for the first time to the best of our knowledge. We expect that this result will lead to significant new and interesting applications of graphene in various types of optical sensors, and more.

Assessment of stream ecosystem health based on oxygen metabolism: Which sensor to use?

Here, we compared sensor precision and drift among four commonly used dissolved oxygen (DO) sensor types under laboratory conditions, and evaluated their accuracy of measurement of stream ecosystem metabolism (EM) and subsequent assessment of stream ecosystem health in the field. Of all tested sensor types, optical sensors had the highest precision, followed by miniaturized polarographic sensors. Traditional polarographic and pulsed polarographic sensors had a lower precision. The traditional polarographic sensors were the only ones exhibiting detectable sensor drift that had to be corrected for, prior to calculations of EM. In parallel EM measurements in two rural and two pristine tropical streams, the four compared DO sensor types estimated relatively similar gross primary production (GPP), ecosystem respiration (R) and GPP:R ratios in each stream, and classified all streams as highly heterotrophic. Nonetheless, parallel GPP and R estimates with different sensors had relative standard deviations of the mean between 6.2% and 34.9%, and between 7.9% and 16.3%, respectively. Thus, sensor accuracy can be a major source of variability in EM estimates. There were only minor differences in stream ecosystem health assessments among different DO sensors, compared to differences between different assessment methods. While all tested sensor types yielded useful ecosystem health classifications, the optical sensor type was the most accurate, and thus, the most suitable for functional impact assessment and monitoring.

An intensity-modulated optical fiber sensor with concave mirror for measurement of displacement

Two fiber intensity-modulated sensors are investigated and used in number of applications, including those in military, industry, biomedical, and aerospace. A common form of two fiber intensity-modulated optical fiber sensor performs its measurement by making use of a pair of straight optical fibers with a plane reflector. The reflected optical intensity is a function of distance between fiber tips and plane reflector as well as refractive index of the medium. This paper describes an alternative sensing structure with a concave reflector instead of a plane reflector and demonstrates the derivation of the geometric mathematical model for analyzing its sensing characteristics. The mathematical model shows that the blind region is minimized, when the plane reflector is replaced by a concave reflector. Such type of optical sensor can be used where space required for the measurement is the major limitation. Experimental results obtained confirm the model.

Refractive Index Estimation of Nanoporous Silicon in Visible and Near-Infrared Spectrum Range

In this paper, we use Bruggeman model to calculate refractive index of nanoporous silicon, which was fabricated by electrochemical etching. The calculated result shows that the refractive index of the nanoporous silicon decreases linearly with increasing porosity and etching current density. In addition, the refractive index of nanoporous silicon was also measured by spectroscopic ellipsometry in the visible light spectrum range. The measured refractive index and extinction coefficient were in agreement with the calculated data, after being modified by the refractive index modified model of heavily doped silicon. In particular, we estimate the refractive index at the optical wavelengths in visible and near-infrared spectrum ranges, which may be widely used in various types of optical sensors and optoelectronic devices for optical communication systems.

Organic–inorganic hybrid fluorescent ultrathin films and their sensor application for nitroaromatic explosives

The luminescent film materials sensitive to external stimuli are important to develop new types of optical sensors and switches. Herein we report organic–inorganic hybrid ultrathin films (UTFs) with reversible luminescence response to nitroaromatic explosive compounds by the use of layer-by-layer assembly of optical brightener BBU and Mg–Al-layered double hydroxide (LDH) nanosheets. UV-Visible absorption and fluorescence spectroscopy showed an orderly growth of the BBU/LDH films upon increasing the number of deposition cycle. XRD, AFM and SEM measurements indicated that the films feature periodic layered structure with a period of ca. 2 nm as well as uniform surface morphology. The BBU/LDH UTFs exhibit well-defined one/two-photon polarized photoemission with the anisotropy as high as 0.38. Moreover, the UTFs show a fast, selective and reversible luminescence response to different nitroaromatic explosives with the most significant luminescent red-shift occurring for picric acid; in addition, by combining suitable luminescent building blocks, the films can also be extended to other dual-color luminescence systems, which exhibit changes in both luminescence intensity and ratiometric fluorescence upon interaction with explosives, enlightening that these films can serve as new types of selective solid luminescent sensors towards nitroaromatic compounds.

New three-dimensional fiber probe for multisensor coordinate measurement

Increasing manufacturing accuracy requirements enforce the development of innovative and highly sensitive measuring tools. Especially for measurement with submicrometer accuracy, the sensor principle has to be chosen appropriately for each measurement surface. Modern multisensor coordinate measurement systems allow automatic selection of different sensor heads to measure different areas or properties of a sample. As an example, different types of optical sensors as well as tactile sensors can be used within the same measuring system. I describe different principles of optical sensors used in multisensor coordinate measurement systems as well as a new approach for tactile measurement with submicrometer accuracy. A special fiber probe has been developed. The tip of the fiber probe is formed as a sphere. The lateral position of this sphere is observed by a microscope objective and can be determined within a fraction of a micrometer. Additionally, a novel optical setup now allows the determination of the z-position of the fiber tip with submicrometer accuracy. For this purpose, an interferometer setup is used. The laser light is coupled into the optical fiber. The light exiting the fiber tip is collected by the microscope objective and superposed with a reference wave, generated directly from the laser. The result is an interference signal that is recorded by the camera and processed by a computer. With this setup, the z-displacement of the fiber sphere can be measured with an accuracy of a fraction of the laser wavelength used.

Liquid sensing capability of rolled-up tubular optical microcavities: a theoretical study

Rolled-up tubular optical microcavities are a novel type of optical sensor for identifying different liquids and monitoring single cells. Based on a Mie scattering method, we systematically study the optical resonances and liquid sensing capability of microtubes. Analytical formulas are presented to calculate the resonant wavelengths λ(r), Q factors, sensitivities S and figures of merit QS. Both ideal and rolled-up microtubes are considered for different optical materials in tube walls (refractive indices ranging from 1.5 to 2.5) and for three setups: tube-in-liquid, hollow-tube-in-liquid and liquid-in-tube. It is found that for rolled-up microtubes, the highest QS can be achieved by using the liquid-in-tube setup and very thin wall thicknesses. A maximal sensitivity is found in the case of the liquid cylinder. Our theory well explains a recent experiment under the setup of tube-in-liquid. It is also found that, although it describes the case of tube-in-liquid well, the waveguide approximation approach is not suitable for the case of liquid-in-tube. The results could be useful to design better optofluidic devices based on rolled-up microtubes.

Optical fiber sensors embedded in concrete for measurement of temperature in a real fire test

We present the results of a real fire test using optical fiber sensors embedded in concrete samples. The temperature curve used in this experiment is described in the Spanish/European standard UNE-EN 1363-1 temperature profile for normalized concrete resistance to real fire tests, reaching temperatures of more than 1000°C inside the fire chamber and up to 600°C inside the concrete samples. Three types of optical sensors have been embedded in concrete: 1. standard fiber Bragg gratings inscribed in photosensitive germanium-boron co-doped fiber, 2. regenerated fiber Bragg grating (RFGB) inscribed in germanium doped fiber, and 3. RFBG inscribed in germanium-boron co-doped fiber.

A novel in situ probe for oxygen uptake rate measurement in mammalian cell cultures

The newly developed in situ oxygen uptake rate (in situ OUR) probe presented in this article is based on the in situ microscope technology platform. It is designed to measure the oxygen uptake rate (OUR) of mammalian cells, an important parameter for metabolic flux analysis, inside a reactor (in situ) and in real-time. The system isolates a known volume of cell culture from the bulk inside the bioreactor, monitors the oxygen consumption over time, and releases the sample again. The sample is mixed during the measurement with a new agitation system to keep the cells in suspension and prevent oxygen concentration gradients. The OUR measurement system also doubles as a standard dissolved oxygen (DO) probe for process monitoring when it is not performing OUR measurements. It can be equipped with two different types of optical sensors (i.e., DO, pH) simultaneously or a conventional polarographic DO-probe (Clark type). This new probe was successfully tested in baby hamster kidney perfusion cell cultures.

Multi-step surface functionalization of polyimide based evanescent wave photonic biosensors and application for DNA hybridization by Mach-Zehnder interferometer

The process of surface functionalization involving silanization, biotinylation and streptavidin bonding as platform for biospecific ligand immobilization was optimized for thin film polyimide spin-coated silicon wafers, of which the polyimide film serves as a wave guiding layer in evanescent wave photonic biosensors. This type of optical sensors make great demands on the materials involved as well as on the layer properties, such as the optical quality, the layer thickness and the surface roughness. In this work we realized the binding of a 3-mercaptopropyl trimethoxysilane on an oxygen plasma activated polyimide surface followed by subsequent derivatization of the reactive thiol groups with maleimide-PEG 2-biotin and immobilization of streptavidin. The progress of the functionalization was monitored by using different fluorescence labels for optimization of the chemical derivatization steps. Further, X-ray photoelectron spectroscopy and atomic force microscopy were utilized for the characterization of the modified surface. These established analytical methods allowed to derive information like chemical composition of the surface, surface coverage with immobilized streptavidin, as well as parameters of the surface roughness. The proposed functionalization protocol furnished a surface density of 144 fmol mm −2 streptavidin with good reproducibility (13.9% RSD, n = 10) and without inflicted damage to the surface. This surface modification was applied to polyimide based Mach-Zehnder interferometer sensors to realize a real-time measurement of streptavidin binding validating the functionality of the MZI biosensor. Subsequently, this streptavidin surface was employed to immobilize biotinylated single-stranded DNA and utilized for monitoring of selective DNA hybridization. These proved the usability of polyimide based evanescent photonic devices for biosensing application.

Pressure Pulse Measurements Using Optical Hydrophone Principles

Pressure pulses are used in extracorporeal lithotripsy, pain therapy and other medical applications. Typical lithotripter pulses reach positive pressure amplitudes of ca. 20 to more than 100 MPa and negative pressures of -5 to more than -20 MPa, depending on the focusing properties and energy settings of the source. The IEC standard 61846, which defines the acoustic parameters of pressure pulse fields, describes the properties of "Focus-" and "Field-" type hydrophones, which were originally specified as PVDF sensors.During recent years, two types of optical sensors were developed, which are based on the principle of measuring reflection changes of a laser beam at a glass-water surface: The fiber optic sensor using bare optical fibers and the "light spot" sensor using a thick glass block. Measurements with both hydrophone types were made with a low pressure transducer (p+max=3 MPa), and two electromagnetic lithotripter sources with the same total acoustic energy (E5MPa=90mJ), one with a wide focus (FWHM = 11 mm, p+max = 30 MPa) and the other with a small focus (FWHM = 3,5 mm, p+max = 83 MPa). The results show that both optical sensor types provide high pressure-time signal fidelity comparable to PVDF membrane sensors. Both optical hydrophones can serve as "Focus-" and "Field-" hydrophones as defined in the lithotripsy measurement standard IEC 61846.

The Influence of the Rotational Speed of the Polymer SU8 on the Thickness of the Waveguide Layer

The paper presents results of investigations concerning the measurement of the refractive index and thickness of planar waveguide structures, obtained by the photopolymerization of polymer SU8. Sodium-calcium glass was used as the substrate. As the knowledge of the quoted parameters is from the viewpoint of the structure of various types of optical sensors of crucial importance, the way of their determination has been presented. The paper deals also with the method of constructing planar polymer waveguides, taking into account problems connected with their adhesion to glass substrates.

Luminescent Sensing of Oxygen Using a Quenchable Probe and Upconverting Nanoparticles

Turned off by oxygen: Luminescent upconverting nanoparticles (UCNPs) of the type NaYF4:Yb,Tm are employed in an entirely new type of optical sensor for oxygen (see picture). Upon laser excitation at 980 nm, these UCNPs act as nanolamps, the blue emission of which is used to photoexcite an iridium complex dissolved in ethyl cellulose. Its green emission, in turn, is dynamically and fully reversibly quenched by molecular oxygen.

ChemInform Abstract: Monodispersed Colloidal Spheres: Old Materials with New Applications

This article presents an overview of current research activities that center on monodispersed colloidal spheres whose diameter falls anywhere in the range of 10 nm to 1 μm. It is organized into three parts: The first part briefly discusses several useful methods that have been developed for producing monodispersed colloidal spheres with tightly controlled sizes and well-defined properties (both surface and bulk). The second part surveys some techniques that have been demonstrated for organizing these colloidal spheres into two- and three-dimensionally ordered lattices. The third part highlights a number of unique applications of these crystalline assemblies, such as their uses as photonic bandgap (PBG) crystals; as removable templates to fabricate macroporous materials with highly ordered and three-dimensionally interconnected porous structures; as physical masks in lithographic patterning; and as diffractive elements to fabricate new types of optical sensors. Finally, we conclude with some personal perspectives on the directions towards which future research in this area might be directed.

Development of a sensor system for traffic data collection

AbstractAlthough many types of traffic sensors are currently in use, all have some drawbacks, and widespread deployment of such sensor systems has been difficult due to high costs. Due to these deficiencies, there is a need to design and evaluate a low cost sensor system that measures both vehicle speed and counts. Fulfilling this need is the primary objective of this research. Compared to the many existing infrared‐based concepts that have been developed for traffic data collection, the proposed method uses a transmission‐based type of optical sensor rather than a reflection‐based type. Vehicles passing between sensors block transmission of the infrared signal, thus indicating the presence of a vehicle. Vehicle speeds are then determined using the known distance between multiple pairs of sensors. A prototype of the sensor system, which uses laser diode and photo detector pairs with the laser directly projected onto the photo detector, was first developed and tested in the laboratory. Subsequently this experimental prototype was implemented for field testing. The traffic flow data collected were compared to manually collected vehicle speed and traffic counts and a statistical analysis was done to evaluate the accuracy of the sensor system. The analysis found no significant difference between the data generated by the sensor system and the data collected manually at a 95% confidence interval. However, the testing scenarios were limited and so further analysis is necessary to determine the applicability in more congested urban areas. The proposed sensor system, with its simple technology and low cost, will be suitable for saturated deployment to form a densely distributed sensor network and can provide unique support for efficient traffic incident management. Additionally, because it may be quickly installed in the field without the need of elaborate fixtures, it may be deployed for use in temporary traffic management applications such as traffic management in road work zones or during special events.

Improved position sensitive detectors using high resistivity substrates

Position sensitive detectors (PSDs) have the advantage of being single continuous devices with no dead zones unlike other types of optical sensors that must be arrayed to produce large area devices. An important aspect of using PSDs is the simplicity of implementing the devices in most applications, i.e. there is no requirement for additional electronics to read electronic output or for obtaining information over large areas. To this end it is advantageous for devices to produce large sensitivities and which can be fabricated using simple, reproducible techniques. This paper will report on a series of Schottky barrier crystalline silicon devices which display markedly higher sensitivities compared with those studied in most other research work now being concentrated on PECVD amorphous silicon structures. In this work, results from devices fabricated from substrates with a range of resistivities and various Schottky metals are presented. Some of the sensitivity measurements obtained were better than 25 mV mm−1, among some of the best sensitivities reported for Schottky barrier crystalline PSDs. These results were obtained alongside excellent linearities. Devices were also tested under a range of light beams including very low light levels of broadband white light ranging from 0.1 up to 10 mW.

A MONITORING METHOD FOR POLLUTANT LOAD IN RIVERS BY USING ARTIFICIAL NEURAL NETWORK

This paper proposes a new method for continuous measurement of pollutant load in rivers without much cost. The basic idea is making the most of “empirical correlations which exist in the target” in order to relate what we can measure to what we want to know. In a field experiment presented here, signals from two types of optical sensors were used to estimate the loads of chemical oxygen demand (COD), total nitrogen (T-N) and total phosphorus (T-P), and artificial neural network (ANN) models were trained to fix “the empirical correlations” among them. The field data were collected in seven rivers located in the watershed of Lake Kasumigaura. The experimental results showed that the three items of water quality were stably estimated with good accuracy for rather long time without too much training data.

Sensor element for a metal–insulator–semiconductor camera system (MISCam)

We discuss the operation of a new type of optical sensor (MISCam) based on a metal–insulator–semiconductor (MIS) structure. The operation principle relies on light-induced changes of the band bending and barrier height at the interface between semiconductor and insulator. An image is obtained from the quenching of the ac signal in analogy to the principle of the laser-scanned photodiode (LSP). Lateral resolution depends on the semiconductor material chosen. We have characterised the MIS structures by C– V, I– V, and spectral response measurements testing different types of insulators like a-Si 3N 4, SiO 2, and AlN. The presence of slow interface charges allows for image memory. Colour sensors can be realised by controlling sign and magnitude of the electric fields in the base and the interface region.