Electro-optical Sensors Research Articles

Use of an electro-optical sensor and phage antibodies for immunodetection of Herbaspirillum

A sheep single-chain antibody-fragment library (Griffin.1, UK) was used to obtain miniantibodies to the lipopolysaccharide of Herbaspirillum seropedicae Z78. Using electro-optical analysis and electron microscopy, we recorded a biospecific interaction of antigenic determinants on the cell surface with phage antibodies against the LPS of H. seropedicae Z78 (mini-AbsLPS). Control experiments were run to rule out nonspecific binding of the mini-AbsLPS to cells of Azospirillum brasilense Sp245. Use of the highly specific mini-AbsLPS enabled the lipopolysaccharide of H. seropedicae Z78 to be detected in a mixture of bacterial cells by electro-optical means (analysis time, ∼5 min). This report is the first to show the possibility of rapid detection of Herbaspirillum on the basis of electro-optical analysis coupled with the use of mini-AbsLPS. The results are promising for the development of biosensor-based methods to detect potentially human-harmful prokaryotes whose structures either have not been studied or are absent from commercial databases.

Efficient Embedded Hardware Architecture for Stabilised Tracking Sighting System of Armoured Fighting Vehicles

A line-of-sight stabilised sighting system, capable of target tracking and video stabilisation is a prime requirement of any armoured fighting tank vehicle for military surveillance and weapon firing. Typically, such sighting systems have three prime electro-optical sensors i.e. day camera for viewing in day conditions, thermal camera for night viewing and eye-safe laser range finder for obtaining the target range. For laser guided missile firing, additional laser target designator may be a part of sighting system. This sighting system provides necessary parameters for the fire control computer to compute ballistic offsets to fire conventional ammunition or fire missile. System demands simultaneous interactions with electro-optical sensors, servo sensors, actuators, multi-function display for man-machine interface, fire control computer, logic controller and other sub-systems of tank. Therefore, a complex embedded electronics hardware is needed to respond in real time for such system. An efficient electronics embedded hardware architecture is presented here for the development of this type of sighting system. This hardware has been developed around SHARC 21369 processor and FPGA. A performance evaluation scheme is also presented for this sighting system based on the developed hardware.

Live electrooptic imaging with a low-coherence optical LO signal source for suppression of interference noises.

Reported in this paper is the first application, to our knowledge, of a low-coherence optical local oscillator signal source to the live electrooptic imaging (LEI) scheme, where high frequency electric field (EF) distributions are visualized in real time. A fiber-optic super luminescent diode (SLD) in conjunction with a LiNbO3 Mach-Zehnder modulator (MZM) was found to work well for the real-time imaging of gigahertz-range EF distributions with high suppression of interference pattern image noises (IPINs), which have long been a problem to be solved. While the SLD-based LEI system works up to the MZM bandwidth (10GHz), IPINs caused by microscopic defects in an electrooptic sensor appear, suggesting a limitation given by the SLD coherence length.

Near earth space object detection using parallax as multi-hypothesis test criterion.

The US Strategic Command (USSTRATCOM) operated Space Surveillance Network (SSN) is tasked with Space Situational Awareness (SSA) for the U.S. military. This system is made up of Electro-Optic sensors, such as the Ground-based Electro-Optical Deep Space Surveillance (GEODSS) and RADAR based sensors, such as the Space Fence Gaps. They remain in the tracking of Resident Space Objects (RSO's) in Geosynchronous Orbits (GEO), due to limitations of SST and GEODSS system implementation. This research explores a reliable, ground-based technique used to quickly determine an RSO's altitude from a single or limited set of observations. Implementation of such sensors into the SSN would mitigate GEO SSA performance gaps. The research entails a method used to distinguish between the point spread function (PSF) observed by a star and the PSF observed from an RSO by using Multi-Hypothesis Testing with parallax as a test criterion. Parallax is the effect that an observed object will appear to shift when viewed from different positions. This effect is explored by generating PSFs from telescope observations of space objects at different baselines. The research has shown the PSF of an RSO can be distinguished from that of a star using single, simultaneous observations from reference and parallax sensing telescopes. This report validates these techniques with both simulations and experimental data from the SST and Naval Observatory sensors.

Diffusion-based cooperative space object tracking

We propose the diffusion-based enhanced covariance intersection cooperative space object tracking (DeCiSpOT) filter. The main advantage of the proposed DeCiSpOT algorithm is that it can balance the computational complexity and communication requirements between different sensors as well as improve track accuracy when measurements do not exist or are of low accuracy. Instead of using the standard covariance intersection in the diffusion step, the enhanced diffusion strategy integrates the 0-1 weighting covariance intersection strategy and the iterative covariance intersection strategy. The proposed DeCiSpOT algorithm also uses the global nearest neighbor and probabilistic data association for multiple space object tracking. Two typical scenarios including cooperative single and multiple space object tracking are used to demonstrate the performance of the proposed DeCiSpOT filter. Using simulated ground-based electro-optical (EO) measurements for multiple resident space objects and multiple distributed EO sensors, the DeCiSpOT archived results comparable to an optimal centralized approach. The results demonstrate that the DeCiSpOT is effective for space object tracking problem with results close to the optimal centralized cubature Kalman filter.

Electro-optical dust sensors calibration by aerosol image analysis

The paper describes the process of data obtaining for designing electro-optical sensors using a television aerosol particles image analyzer. Using simulation based on Mie theory, the process of calibration of simple electro-optical aerosol (dust) sensor is carried out. In the paper the main dependences for sensor calibration are shown. The proper calibration allows power saving by selection certain laser beam power level.

Transient Voltage Measurements for Overhead Transmission Lines and Substations by Metal-Free and Contactless Integrated Electro-Optic Field Sensors

Measuring the transient voltages, including lightning or switching impulse overvoltage, is helpful for accident analysis of power system and insulation design. In this paper, a contactless transient voltage measuring system based on a metal-free integrated electro-optic electric field sensor was proposed, implemented and tested. The lightning and switching impulse transients are proportional to the electric field they generate and vice versa, enabling measurement of the transient voltage by measuring the associated electric field. The proposed method uses an electric field sensor to directly measure the field generated by the voltage without any capacitive coupling. In addition, a method to decouple the multiphase coupling was proposed. The performances of the measuring system were tested by simulation experiments and compared with that of a standard divider. The field data of the transient overvoltage on a 220 kV bus during the process of putting a capacitor voltage transformer into operation were given. The measurement results were found to coincide with the related physical process.

Uncooperative Spacecraft Relative Navigation With LIDAR-Based Unscented Kalman Filter

Autonomous relative navigation is a critical functionality which needs to be developed to enable safe maneuvers of a servicing spacecraft (chaser) in close-proximity with respect to an uncooperative space target, in the frame of future On-Orbit Servicing or Active Debris Removal missions. Due to the uncooperative nature of the target, in these scenarios, relative navigation is carried out exploiting active or passive Electro-Optical sensors mounted on board the chaser. The focus here is placed on active systems, e.g., LIDARs. In this paper, an original loosely-coupled relative navigation architecture which integrates pose determination algorithms designed to process raw LIDAR data (i.e., 3D point clouds) within a Kalman filtering scheme is presented. Pose determination algorithms play a twofold role being used to initialize the filter state and covariance as well as in the update phase of the Kalman filter. The proposed filtering scheme is an Unscented Kalman Filter designed to use, as measurements for the update phase, relative position, attitude and angular velocity estimates. Performance assessment is carried out within a simulation environment realistically reproducing the operation of a scanning LIDAR and the relative motion between two spacecraft during a target monitoring maneuver. The numerical simulation campaign demonstrates robustness of the proposed approach even when dealing with challenging conditions (e.g., low range measurement accuracy, low update rate and high point-cloud sparseness) determined by the LIDAR noise level and operational parameters.

MIMO multi-channels for simultaneous electro-optic distributed sensors

Abstract The distributed optical sensors using the multi-input light sources have been designed and simulated. It consists of 6 sensor nodes coupled to the main ring resonator, which is an optical circulator operation. It is a micro-scale device that can be fabricated by the current technology. The three distance light sources are simultaneously fed and the cross-connected signals combined in the circulator. By using the suitable parameters, the whispering gallery modes (WGMs) are generated at the center nodes from which the channel spacing signals can be obtained and used for distributed sensors. The analytical details and the simulation using the selected parameters are presented. The channel spacing of the cross-connected outputs of 1.2 µm is achieved. The simultaneous sensor sensitivity in the terms of ( Δ λ / λ ) of approximately 1.28 is obtained.

Impact of electric propulsion technology and mission requirements on the performance of VTOL UAVs

One of the engineering challenges in aviation is the design of transitioning vertical take-off and landing (VTOL) aircraft. Thrust-borne flight implies a higher mass fraction of the propulsion system, as well as much increased energy consumption in the take-off and landing phases. This mass increase is typically higher for aircraft with a separate lift propulsion system than for aircraft that use the cruise propulsion system to support a dedicated lift system. However, for a cost–benefit trade study, it is necessary to quantify the impact the VTOL requirement and propulsion configuration has on aircraft mass and size. For this reason, sizing studies are conducted. This paper explores the impact of considering a supplemental electric propulsion system for achieving hovering flight. Key variables in this study, apart from the lift system configuration, are the rotor disk loading and hover flight time, as well as the electrical systems technology level for both batteries and motors. Payload and endurance are typically used as the measures of merit for unmanned aircraft that carry electro-optical sensors, and therefore the analysis focuses on these particular parameters.

Terahertz microscopy assisted by semiconductor nonlinearities.

Terahertz (THz) imaging is currently based on linear effects, but there is great interest on how nonlinear effects induced by terahertz radiation could be exploited to provide extra information that is unobtainable by conventional imaging schemes. In particular, at field strengths on the order of 100 kV cm-1 to 1 MV cm-1, transmission properties inside semiconductor materials are largely affected at the picosecond time-scale, which raise the prospect of interesting nonlinear imaging applications at THz frequencies. Here, we experimentally investigate a method to map the two-dimensional nonlinear near-field distribution of an intense THz pulse passing through a thin film-doped semiconductor. By inserting a metamaterial structure between the electro-optic sensor and the doped film, the nonlinear near-field dynamics shows a different and enhanced contrast of the sample when compared to its linear counterpart.

Method of the horizon detection from electro-optical sensors under maritime environment

Method of the horizon detection from electro-optical sensors under maritime environment

Improved Laplace Earth Satellite Orbit Determination Using Line-of-Sight Projective Coordinates

This study aimed to improve the accuracy, efficiency, range of applicability, and numerical stability of the classical Laplace method for preliminary orbit determination when the observing sensor and the observed object are both in idealized Keplerian geocentric elliptical orbits. The improvements that were made flow largely from representing the line of sight by stabilized projective rather than angular coordinates, such as declination and right ascension or local azimuth and elevation. The Laplace classical method determines the orbital position and velocity of an object in space from three line-of-sight unit vectors pointing from the observing sensor to the observed object and the corresponding sensor inertial positions and velocities at the three observation times. The performance improvement of the modernized algorithm on a set of two orbit test cases is shown, in which the observing electro-optical sensor is carried aboard a geostationary satellite. Moreover, this paper shows how to solve the problem of choosing the right orbit from the two feasible candidates that correspond to the two roots of the classical deflated seventh degree polynomial with a single additional line-of-sight observation.

Wideband Multi-Arm Bowtie Antenna for Millimeter Wave Electro-Optic Sensors and Receivers

We propose and demonstrate a novel design of a multi-arm bowtie antenna (MABA) able to provide wideband field enhancement (FE). The FE is a looked-for parameter of antennas in an integrated electro-optic (EO) communication and sensing applications. In the proposed MABA, the paralleled arms with different lengths and flare angles provide multiple resonance frequencies. By tailoring these resonance frequencies adequately close to each other, a wide range of frequencies with high FE is achieved and the intrinsic limitation of conventional bowtie antennas (BAs) in this regard is overcome. The proposed MABA is designed at the center frequency of 66.2 GHz and fabricated on a silicon-on-insulator substrate with 1.69 mm × 0.21 mm dimensions. Simulation and measurement results show about 40° beamwidth and 63.4-dB FE peak with 27 GHz bandwidth, which is three times larger than the bandwidth of a conventional BA, as the most commonly used antenna for this application, on the same substrate. A figure of merit (FoM) is proposed to study the performance of antennas for integrated EO applications approximately independent from the effects of substrate, operating frequency, and optical parts. The FoM is calculated and a comparison is presented for different state-of-the-art antennas in literature showing more than 2 times better performance of the proposed MABA.

High speed CMOS acquisition system based on FPGA embedded image processing for electro-optical measurements

Electro-optical measurements, i.e., optical waveguides and plasmonic based electrochemical impedance spectroscopy (P-EIS), are based on the sensitive dependence of refractive index of electro-optical sensors on surface charge density, modulated by an AC electrical field applied to the sensor surface. Recently, P-EIS has emerged as a new analytical tool that can resolve local impedance with high, optical spatial resolution, without using microelectrodes. This study describes a high speed image acquisition and processing system for electro-optical measurements, based on a high speed complementary metal-oxide semiconductor (CMOS) sensor and a field-programmable gate array (FPGA) board. The FPGA is used to configure CMOS parameters, as well as to receive and locally process the acquired images by performing Fourier analysis for each pixel, deriving the real and imaginary parts of the Fourier coefficients for the AC field frequencies. An AC field generator, for single or multi-sine signals, is synchronized with the high speed acquisition system for phase measurements. The system was successfully used for real-time angle-resolved electro-plasmonic measurements from 30 Hz up to 10 kHz, providing results consistent to ones obtained by a conventional electrical impedance approach. The system was able to detect amplitude variations with a relative variation of ±1%, even for rather low sampling rates per period (i.e., 8 samples per period). The PC (personal computer) acquisition and control software allows synchronized acquisition for multiple FPGA boards, making it also suitable for simultaneous angle-resolved P-EIS imaging.

Improved common-path spectral interferometer for single-shot terahertz detection

To seek high signal-to-noise ratio (SNR) is critical but challenging for single-shot intense terahertz (THz) coherent detection. This paper presents an improved common-path spectral interferometer for single-shot THz detection with a single chirped pulse as the probe for THz electro-optic (EO) sampling. Here, the spectral interference occurs between the two orthogonal polarization components with a required relative time delay generated with only a birefringent plate after the EO sensor. Our experiments show that this interferometer can effectively suppress the noise usually suffered in a non-common-path interferometer. The measured single-shot SNR is up to 88.85, and the measured THz waveforms are independent of the orientation of the used ZnTe EO sensor, so it is easy to operate and the results are more reliable. These features mean that the interferometer is quite qualified for applications where strong THz pulses, usually with single-shot or low repetition rate, are indispensable.

Towards optically responsive smart materials: electronic interactions between polymeric semiconductor and photochromic molecule

Electronic interactions between π-conjugated poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and photochromic 6-nitro-1′,3′,3′-trimethylspiro[2H-1-benzopyran-2,2′-indoline] (SP) were studied using the optical spectroscopy. The observed fluorescence quenching of MDMO-PPV by the open merocyanine form of the SP was explained as a photoinduced charge transfer. This opens the possibility to reversibly switch between low and high photoconductive states which can be used for the construction of electro-optical bi-stable devices or sensors.

Design of relative trajectories for in orbit proximity operations

This paper presents an innovative approach to design relative trajectories suitable for close-proximity operations in orbit, by assigning high-level constraints regarding their stability, shape and orientation. Specifically, this work is relevant to space mission scenarios, e.g. formation flying, on-orbit servicing, and active debris removal, which involve either the presence of two spacecraft carrying out coordinated maneuvers, or a servicing/recovery spacecraft (chaser) performing monitoring, rendezvous and docking with respect to another space object (target). In the above-mentioned scenarios, an important aspect is the capability of reducing collision risks and of providing robust and accurate relative navigation solutions. To this aim, the proposed approach exploits a relative motion model relevant to two-satellite formations, and developed in mean orbit parameters, which takes the perturbation effect due to secular Earth oblateness, as well as the motion of the target along a small-eccentricity orbit, into account. This model is used to design trajectories which ensure safe relative motion, to minimize collision risks and relax control requirements, providing at the same time favorable conditions, in terms of target-chaser relative observation geometry for pose determination and relative navigation with passive or active electro-optical sensors on board the chaser. Specifically, three design strategies are proposed in the context of a space target monitoring scenario, considering as design cases both operational spacecraft and debris, characterized by highly variable shape, size and absolute rotational dynamics. The effectiveness of the proposed design approach in providing favorable observation conditions for target-chaser relative pose estimation is demonstrated within a simulation environment which reproduces the designed target-chaser relative trajectory, the operation of an active LIDAR installed on board the chaser, and pose estimation algorithms.

Phase-Stabilized W-Band Planar Imaging System for Near-to-Far-Field Projection Based on Photonic Sensors

This letter presents a highly stabilized planar near-field imaging system for millimeter-wave antenna characterization based on dual electrooptic sensors. The issue of system instability, which often occurs in millimeter-wave sensing, is effectively eliminated by employing error correction techniques with field-calibrated probes. This technique compensates for the phase vibration of a radio frequency source by using an additional reference probe. Detailed stabilization techniques for the phase drift are discussed. A probe is also field-calibrated on the W-band so as to provide electric field imaging with the absolute value. W-band horn antenna characterization at 95 GHz is conducted, and the absolute field distribution is compared using the proposed system and a conventional electrical near-field system. A simulation is also conducted. The radiation far-field pattern and gain, calculated from the near-field measurements, are in good agreement with each other according to a comparison of these outcomes. Moreover, a back-projection algorithm with a far electric field as input is utilized to reconstruct the aperture fields of a horn antenna. Finally, a comparison between the measured and reconstructed near-field data with different distances between the probe and the horn antenna is made.

Electro optic sensor for high precision absolute distance measurement using multiwavelength interferometry.

A prototype multi-wavelength interferometric, phase shifting distance sensor based on linear electro optic effect has been demonstrated in this work to improve the measurement speed of a commercial four-wavelength interferometer. Experimental results revealed the phase modulation ability of the sensor, preserving equivalent efficiency for nanometer-scale absolute distance measurement similar to present piezoelectricity driven mechanical phase modulation. The electro optic sensor working under free beam propagation can significantly overcome the limitations experienced by mechanical phase modulation technique such as the restricted value for the modulating frequency and as well the high driving voltage requirement.