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Sensors Journal, IEEE

Issue 1 • Date Jan. 2009

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Displaying Results 1 - 17 of 17
  • [Front cover]

    Page(s): C1
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  • IEEE Sensors Journal publication information

    Page(s): C2
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  • Table of contents

    Page(s): 1 - 2
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  • Analysis of Pulsed THz Imaging Using Optical Character Recognition

    Page(s): 3 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1725 KB) |  | HTML iconHTML  

    Using a reflection-based pulsed THz imaging system built upon our ErAs:GaAs photoconductive switch and a gated receiver, we quantify image quality at different detection bands (centered at 100, 400, and 600 GHz). Zero-bias Schottky diode detectors mounted in various waveguide sizes are used to tune the operational frequency bands of the imaging system, while the rest of the imaging system remains unchanged. The image quality is quantified by applying an optical character recognition (OCR) algorithm on THz images of 8-by-10 mm copper letters on a fiberglass substrate. Using the OCR success rate as a metric, we see a fivefold improvement in image quality from a 400 GHz to a 600 GHz imaging system, while our 100 GHz images do not produce any correct OCR results. In a comparison experiment performed at 600 GHz, the image signal-to-noise ratio (SNR) is degraded by placing increasing numbers of denim sheets (5.4 dB decrease in signal per layer) into the beam path. We find that the OCR success rate is roughly constant from one sheet to four sheets of denim (33-25 dB SNR) and then drops off sharply starting at five denim sheets. View full abstract»

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  • Hydrogen Sensor Made of Porous Silicon and Covered by TiO _{2-{\rm x}} or ZnO \langle Al \rangle Thin Film

    Page(s): 9 - 12
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (463 KB) |  | HTML iconHTML  

    Hydrogen sensor working at room and 40degC temperatures made of porous silicon covered by the TiO2-x or ZnO(Al) thin film was realized. Porous silicon layer was formed by electrochemical anodization on a p- and n-type Si surface. Thereafter, n-type TiO2-x and ZnO(Al) thin films were deposited onto the porous silicon surface by electron-beam evaporation and magnetron sputtering, respectively. Platinum catalytic layer and Au electric contacts were for further measurements deposited onto obtained structures by ion-beam sputtering. The sensitivity of manufactured structures to 1000-5000 ppm of hydrogen, propane-butane mixture, and humidity was studied. Sensitivity of obtained structures was determined as ratio of the resistivity of structures in the presence of investigated gas to that in air. Results of sensitivity measurements showed that it is possible to realize a hydrogen nanosensor, resistivity of which can be decreased up to 2.5 times at room temperature and four times at 40degC for the Pt/TiO2-x/PS structure, as well as two times for the Pt/ZnO(Al)/PS structure at 40degC at 5000 ppm hydrogen concentration, respectively. Both structures have the recovery and response time of approximately 20 s and rather high durability and selectivity to hydrogen gas. View full abstract»

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  • Planar Optical Waveguide Evanescent Wave {\rm CO}_{2} Sensor Based on a Clad of Alstonia Scholaris Leaf Extract

    Page(s): 13 - 19
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1591 KB) |  | HTML iconHTML  

    An evanescent wave biosensor is designed and developed using a single mode planar optical waveguide based on a spin coated clad of leaf extract of Alstonia Scholaris. The fabricated sensor showed CO2 concentration dependent response. The specialty of this sensor is that it can be used when stored at room temperature (25degC) up to a maximum of 25-30 days with 90% retention of original sensitivity. These CO2 sensing biochips showed good operational efficiency for 10 cycles. The planar optical waveguide is versatile, easy to fabricate and can be used for ppm level CO2 measurement with good sensitivity. Cross sensitivity with respect to humidity is studied. The sensor exhibited a short response time of 4-5 s and recovery time of 25 s with good repeatability and reproducibility. View full abstract»

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  • A CMOS Image Sensor With In-Pixel ADC, Timestamp, and Sparse Readout

    Page(s): 20 - 28
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1129 KB) |  | HTML iconHTML  

    Recent developments in CMOS image sensors have focused on the advancement of digital pixel sensors (DPS). A novel DPS aiming to combine multiple functionalities on the imaging plane has been designed and tested: The on pixel intelligent CMOS (OPIC) sensor was manufactured in a 0.25 mum logic process with 5 metal layers, and 8 mum epitaxial layers. The sensor comprises three 2 x 2 mm test arrays of 30 mum pixels. Two of the test arrays are named "advanced" and include two 8-bit DRAM cells, one 8-bit ROM cell, and one 1-bit DRAM cell per pixel. The 8-bit DRAM cells can record both ADC and "time-to-threshold" data, while the ROM hard codes the pixel address within the array. The 1-bit DRAM acts as a "hit flag" enabling automatic sparsification of the image data based on an external threshold. Results of the device simulation, design and electro-optical testing are presented. The OPIC sensor is shown to have ~50 e-read noise, 105 ke- full well capacity, 10% fill factor, and a measured power consumption of 230 mW when operated at 1000 fps. A 79% reduction in frame size is achieved when imaging a point-like object in sparse mode. Capacitive coupling from digital signal lines was observed in certain modes of operation of the sensor. An alternative coding scheme was devised to quantify this and the effect was found to be most evident at ADC units of less than 2.5 mV. A number of applications are proposed for the functionality available on OPIC. The test structure is demonstrated in a high-speed tracking application and shown to have a 100 ns resolution. This device holds promise for tracking applications where a high position and time accuracy is required. View full abstract»

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  • Tactile Sensing Using Force Sensing Resistors and a Super-Resolution Algorithm

    Page(s): 29 - 35
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1136 KB) |  | HTML iconHTML  

    This paper presents a tactile sensor consisting of an array of force sensing resistors (FSRs). The tactile sensing array can be seen as a coordinated system of touch sensors. The low spatial resolution measured with the FSRs compared to other force or pressure sensors required the use of a super-resolution algorithm. Super-resolution algorithms are often used in digital image processing to enhance the resolution of images. Multiple images taken from slightly different orientations are superimposed in such a way that a single higher-resolution image is obtained. Different touch sensors are briefly discussed and the use of FSRs is motivated. Image-registration techniques are discussed and the super-resolution algorithm developed for the application is presented. Some tests performed using the tactile sensor in a neck palpation device and the results of these tests are also presented. View full abstract»

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  • Reshaping of a Divergent Elliptical Gaussian Laser Beam Into a Circular, Collimated, and Uniform Beam With Aspherical Lens Design

    Page(s): 36 - 44
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1595 KB) |  | HTML iconHTML  

    In this paper, we present a specific optical system of two aspherical lenses designed to circularize, collimate, and expand an edge-emitting semiconductor laser beam and transform its irradiance distribution from Gaussian to a uniform-square distribution for possible application in light detection and ranging sensors. It is verified that the diffraction effects are negligible so that geometrical ray optics is used to design this optical system. To accomplish the design, the source beam profile is decoupled into two independent beam profiles represented in two transverse directions. Analytical equations specific to this lens system are derived and MATLAB is used to solve these equations and simulate a design example. Results are presented for a specific example. View full abstract»

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  • Composite Magnetoelectric Transducer of Terfenol-D and Pb(Zr,Ti)O _{3} Plates Bonded on an Elastic Substrate

    Page(s): 45 - 50
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (405 KB) |  | HTML iconHTML  

    The megnetoelectric (ME) effect of magnetostrictive Terfenol-D (Tb1 - xDyxFe2 - y) and piezoelectric Pb(Zr,Ti)O3 plates bonded on a beryllium bronze substrate is reported. The substrate severs as a frequency determining element and dominates the quality factor (Q m) of the oscillator. The device can be regarded as a driven damped system. Its resonance occurs at multimodes where the Terfenol-D plate oscillates at frequencies near the allowed frequencies of the substrate, producing a much greater response to finite AC magnetic field input. The theoretical analysis demonstrates that the ME voltage coefficient (alphaME) is directly proportional to the factor of gamma = Q m k eff 2/(1 - k eff 2), where k eff is the effective electromechanical coupling factor. The experimental results show that: (i) there are multiple ME response peaks; (ii) the alphaME and Qm are higher than those of the previous reported laminate composites of Terfenol-D and Pb(Zr,Ti)O3 plates only; and (iii) the factor of gamma is enhanced by the introduction of elastic substrate and the enhancement of alphaME is originated from the increase of the factor of gamma . View full abstract»

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  • X-Ray Detection Using a Two-Transistor Active Pixel Sensor Array Coupled to an a-Se X-Ray Photoconductor

    Page(s): 51 - 56
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (755 KB) |  | HTML iconHTML  

    A direct-conversion X-ray sensor array using amorphous silicon (a-Si) thin-film transistor (TFT) based active pixel sensor (APS) readout circuit coupled with a stabilized amorphous selenium (a-Se) photoconductor for large-area digital imaging applications is presented. The pixel readout circuit employs a novel two-transistor (2T) active/passive pixel architecture that enables a compact pixel circuit for high-resolution sensor arrays with high large-area fabrication reliability. The X-ray detector consists of an in-house fabricated 150 mum pixel pitch 2-TFT pixel coated with an 80 mum thick a-Se photoconductor. A detector dark current of 110 pA/cm2 at 10 V/mum electric field, and a controllable pixel conversion gain up to 8.4 nA/mR with a quantum efficiency of 60% was measured. Capabilities such as voltage programmable gain and dynamic range control, as well as nondestructive readout during X-ray exposure are demonstrated. The detector in this work represents a highly promising technology for high-resolution X-ray digital imaging, adaptable to a wide range of applications owing to its gain and dynamic range programmability. View full abstract»

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  • Probability of Detection and Optimal Sensor Placement for Threshold Based Detection Systems

    Page(s): 57 - 60
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (678 KB) |  | HTML iconHTML  

    This paper provides a probabilistic analysis of simple detection systems which are based on thresholding feature values extracted from a sensor signal. For such systems, this paper explains how to calculate the probability of detection as a function of range from the sensor to the object of interest. This function is important in that it enables optimal positioning of a group of sensors, either maximizing detection rates for a given number of sensors or informing the minimum number of sensors necessary to achieve a desired probability of detection throughout an area. An example case study is presented, based on a novel approach to passive acoustic diver detection in noisy environments. View full abstract»

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  • Fully Automated E-Field Measurement System Using Pigtailed Electro-Optic Sensors for Temperature-Dependent-Free Measurements of Microwave Signals in Outdoors Conditions

    Page(s): 61 - 68
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1719 KB) |  | HTML iconHTML  

    We present, in this paper, pigtailed electro-optic sensors dedicated to the measurement of high-power microwave signals in outdoors conditions. We give results on high-power microwave single-shot pulses obtained with long fiber links (> 20 m) in hard environmental conditions (temperature variations up to 30degC). In these awkward outdoors conditions, we obtain very stable measurements with rms signal fluctuations lower than 0.2 dB. We focus here especially on the design of the temperature-dependent-free system. View full abstract»

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  • Implementation of Spreader Pose Control Using Dual-Electric Compasses

    Page(s): 69 - 1
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    A spreader pose control system based on the skew angle of the spreader has been implemented by using dual-electric compasses. In the conventional spreader pose control, researchers most often use CCD cameras, laser sensors or tilt sensors to measure the skew angle. However, those sensors are not only sensitive to the weather and disturbances but are also expensive to build a stable system. To overcome these shortcomings, an inexpensive and efficient system to control the spreader pose has been implemented by using dual-magnetic compasses. Note that since the spreader iron-structure itself is a noise source to the magnetic compass, it is not considered prudent to use the magnetic compass to measure the orientation of the spreader. An algorithm to eliminate the interferences of metal structure to the dual compasses has been developed in this paper. To show the effectiveness of the dual-magnetic compasses proposed in this study, a 10:1 reduction model of a spreader control system is implemented and real pose control data are analyzed. View full abstract»

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  • Textile-Based Capacitive Sensors for Respiration Monitoring

    Page(s): 71 - 78
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    Respiration monitoring in everyday life enables the early detection of the diseases and disorders that can suddenly manifest in a life threatening episode. Long-term monitoring can extend the capabilities of healthcare providers if reliability can be achieved economically. In this paper, the potential for using capacitive sensing to serve as an inexpensive method for long-term respiration sensing is explored. This paper proposes new designs of capacitive sensors for respiration sensing and describes the design and fabrication of a prototype textile-based capacitive-sensor respiration belt. Two capacitive sensors were designed and fabricated for detecting chest or abdominal circumference changes of up to 60 mm. These sensors gave good linearity, and the respiration measurements obtained with these new sensors show that they are capable of measuring respiration rate, and possibly lung function parameters. View full abstract»

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  • IEEE copyright form

    Page(s): 79 - 80
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  • IEEE Sensors Council Information

    Page(s): C3
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Aims & Scope

The IEEE Sensors Journal is a peer-reviewed, monthly online/print  journal devoted to sensors and sensing phenomena

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Meet Our Editors

Editor-in-Chief
Krikor Ozanyan
University of Manchester
Manchester, M13 9PL, U.K.