Electro-optical Detection System Research Articles

Small tracking error correction for moving targets of intelligent electro-optical detection systems

Small tracking error correction for moving targets of intelligent electro-optical detection systems

Optimizing Controls to Track Moving Targets in an Intelligent Electro-Optical Detection System

Electro-optical detection systems face numerous challenges due to the complexity and difficulty of targeting controls for “low, slow and tiny” moving targets. In this paper, we present an optimal model of an advanced n-step adaptive Kalman filter and gyroscope short-term integration weighting fusion (nKF-Gyro) method with targeting control. A method is put forward to improve the model by adding a spherical coordinate system to design an adaptive Kalman filter to estimate target movements. The targeting error formation is analyzed in detail to reveal the relationship between tracking controller feedback and line-of-sight position correction. Based on the establishment of a targeting control coordinate system for tracking moving targets, a dual closed-loop composite optimization control model is proposed. The outer loop is used for estimating the motion parameters and predicting the future encounter point, while the inner loop is used for compensating the targeting error of various elements in the firing trajectory. Finally, the modeling method is substituted into the disturbance simulation verification, which can monitor and compensate for the targeting error of moving targets in real time. The results show that in the optimal model incorporating the nKF-Gyro method with targeting control, the error suppression was increased by up to 36.8% compared to that of traditional KF method and was 25% better than that of the traditional nKF method.

Improved target detection method for space-based optoelectronic systems

The detection of faint and small targets by space-based surveillance systems is difficult owing to the long distances, low energies, high speeds, high false alarm rates, and low algorithmic efficiencies involved in the process. To improve space object detection and help prevent collisions with critical facilities such as satellites, this study proposes an improved method for the detection of faint and small space-based targets. The proposed method consists of two components: star atlas preprocessing and space-based target detection. The star atlas preprocessing step applies multi-exposure image pyramidal weighted fusion to the original image containing the faint and small space-based target. After obtaining the image pyramidal weighted fusion result atlas, the algorithm employs threshold segmentation to improve the overall image clarity, highlight image details, and provide additional information for target detection. The detection of targets partially relies on the local symmetry of the image. Accordingly, a diffusion function describing the local symmetry is established to precisely locate stars by measuring the symmetry factor in a small area surrounding each pixel in the star atlas. This effectively removes the background stars while retaining high-definition and high-contrast images. The efficacy of the algorithm is validated using simulated datasets consisting of space-based and real images. The results demonstrate that the proposed technique improves the applicability of the multistage hypothesis testing (MHT) method in the context of a complex space environment, thus improving the performance of the space-based electro-optical detection system to better catalogue, identify, and track space targets.

Prediction and Control of Small Deviation in the Time-Delay of the Image Tracker in an Intelligent Electro-Optical Detection System

A small deviation in the time-delay of the image tracker is essential for improving the tracking precision of an electro-optical system, and for future advances in actuator technology. The core goal of this manuscript is to address issues such as tracking the controller time-delay compensation and the precision of an electro-optical detection system using an advanced filter design, a fire control modeling, and an anti-occlusion target detection system. To address this problem, a small deviation in the time-delay prediction and control method of the image tracker is proposed based on the principle of linear motion transformation. The time-delay error formation is analyzed in detail to reveal the scientific mechanism between the tracking controller feedback and the line-of-sight position correction. An advanced N-step Kalman filtering controller model is established by combining a line-of-sight firing control judgment and a single-sample training anti-occlusion DSST target tracking strategy. Finally, an actuator platform with three degrees of freedom is used to test the optical mechatronics system. The results show that the distribution probability of the line-of-sight measuring error in a circle with a radius of 0.15 mrad is 72%. Compared with the traditional control method, the tracking precision of the optimal method is improved by 58.3%.

Terahertz Time-Domain Polarimetry for Principal Optical Axes of Anisotropic Crystals

We propose a method for measuring the terahertz properties for two principal optical axes of anisotropic crystals without optical activity using terahertz time-domain spectroscopy (THz-TDS). The method put forward in this paper utilizes the inherent polarization sensitivity of the THz-TDS electro-optic detection system. We demonstrate the practical application of the method by measuring the temperature dependence of the refractive index and the absorption coefficient of a lithium triborate crystal for three optical axes.

Pointing error compensation of electro-optical detection systems using Gaussian process regression

Pointing accuracy is an important indicator for electro-optical detection systems, as it significantly affects the system performance. However, as a result of misalignment, nonperpendicularity in the manufacturing and assembly processes, as well as the sensor errors such as camera distortion and angular sensor error, the pointing accuracy is significantly affected. These errors should be compensated before using the system. Parametric models are firstly proposed to compensate for the errors, whilst the semi-parametric models with the nonlinearity added are also put forward. Both methods should analyse the parametric part first, which is a complicated and inaccurate process. This paper presents a nonparametric model, without any prior information about mechanical dimensions, etc. It depends only on the test data. Gaussian Process regression is used to represent the relationship between data and predict the compensated output. The test results have shown that the regression variances have decreased by more than an order of magnitude, and the means have also been significantly reduced, with the pointing error well improved. The nonparametric model based on Gaussian Process is thus demonstrated to be an effective and powerful tool for the pointing error compensation.

Compact single-shot electro-optic detection system for THz pulses with femtosecond time resolution at MHz repetition rates.

Electro-optical detection has proven to be a valuable technique to study temporal profiles of THz pulses with pulse durations down to femtoseconds. As the Coulomb field around a relativistic electron bunch resembles the current profile, electro-optical detection can be exploited for non-invasive bunch length measurements at accelerators. We have developed a very compact and robust electro-optical detection system based on spectral decoding for single-shot longitudinal bunch profile monitoring at the European X-ray Free Electron Laser (XFEL) for electron bunch lengths down to 200 fs (rms). Apart from the GaP crystal and the corresponding laser optics at the electron beamline, all components are housed in 19 in. chassis for rack mount and remote operation inside the accelerator tunnel. An advanced laser synchronization scheme based on radio-frequency down-conversion has been developed for locking a custom-made Yb-fiber laser to the radio-frequency of the European XFEL accelerator. In order to cope with the high bunch repetition rate of the superconducting accelerator, a novel linear array detector has been employed for spectral measurements of the Yb-fiber laser pulses at frame rates of up to 2.26 MHz. In this paper, we describe all sub-systems of the electro-optical detection system as well as the measurement procedure in detail and discuss the first measurement results of longitudinal bunch profiles of around 400 fs (rms) with an arrival-time jitter of 35 fs (rms).

Acute ethanol effect on erythrocytes in vitro: a new approach to differential diagnostics of fatty liver disease

The aim of the work is to study the differences in changes in the viscoelastic parameters of erythrocytes (amplitude of deformation, summarized viscosity and summarized rigidity) in the dynamics of interaction with ethanol in vitro in patients with non-alcoholic (NAFLD) and alcoholic (AFLD) fatty liver disease for use in differential diagnostics. Materials and methods. 50 men were examined, 24 - with NAFLD (46.5±1.5 years), 26 - with AFLD (48.6±1.2 years). The study of viscoelastic parameters of erythrocytes was carried out by dielectrophoresis with an electro-optical cell detection system. The levels of erythrocytes were evaluated before and after in vitro exposure for 300 s with 10 μl of a 0.02% ethanol solution in the dynamics of the experiment. Results. In erythrocytes of patients with NAFLD after exposure with ethanol, a decrease in strain amplitude was revealed against the background of an increase in summarized viscosity and summarized rigidity, on the contrary, in erythrocytes in patients with AFLD, an increase in the ability to deform was observed with a decrease in generalized viscosity and rigidity (p <0.01-0.05). Inverse reaction of cells to ethanol exposure allowed to distinguish patients with fatty liver disease of various origins with sensitivity of 87.5%, specificity of 96.2%, predictive value of positive - 95.4% and negative - 89.3%, as well as an accuracy of 92%. The proposed method for distinguishing fatty liver disease of various origins is promising due to its simplicity, high throughput and low cost.

Capillary-based micro-optofluidic viscometer

In this study, a capillary-based micro-optofluidic viscometer, which is capable of measuring dynamic viscosity in a range of with only a small volume of liquid (26 µl) in just a few seconds (less than 15 s for most of the samples used) with an acceptable accuracy (99.56%), has been designed, fabricated, and tested. This device consists of two different parts, namely a poly(methyl methacrylate) (PMMA) microfluidic chip and an electro-optical detection system. The viscometer determines viscosity by measuring the time that the liquid travels between two specific points of a rectangular microchannel. The microchannel has been micro-milled on a PMMA substrate, which has been bonded to another PMMA sheet. The fluid flow inside the microfluidic chip has been created by the capillary driven flow; hence, there is no need for any external devices to generate fluid flow. The resolution of this microviscometer is approximately 0.001 mPa s. An ADC circuit has been added to the electro-optical detection system, which is an optically-activated stopwatch circuit, to enhance accuracy, sensitivity, resolution, and to make this viscosity measurement device applicable and efficient for a wide range of applications. This integrated microviscometer automatically notices entry of liquid and completion of the experiment, and finally gives the result. In this study, only Newtonian fluids were tested via this microviscometer, but this device is also capable of measuring non-Newtonian liquids. This portable microviscometer has applications in different fields such as point-of-care diagnosis, chemical and food industries, pharmaceutical industries, research laboratories, etc.

Wireless Data Transmission Method Using Pulsed THz Sliced Spectral Supercontinuum

A method of ultrafast wireless information transmission using spectrum-sliced supercontinuum (SC) along the THz frequency range is presented in this letter. The THz spectrum-sliced SC was formed by femtosecond optical pulses doubled in a Michelson interferometer before being input onto a MgO:LiNbO3-THz generator. Two THz pulses generated by femtosecond pulses within a MgO:LiNbO3-crystal provided the spectrum-sliced SC in the spectral domain, which was recorded by an electro-optical detection system. The transmission rate in this method is determined by the bandwidth of the THz spectrum, the number of spectral lines in the SC, and the pulse repetition rate. We have demonstrated an SC containing 31 spectral lines with 23-GHz spacing within the range from 0.04 to 0.75 THz. The signal with encoded information was successfully transmitted over 2.4 m in free-space.

Underwater Wide-Area Layered Light Field for Underwater Detection

In underwater electro-optic detection, image quality can be degraded by the backscattering of light from the illuminated water volume. In practical systems, we tend to simultaneously require a high level of detection distance (DD), field of view (FOV), and depth of field (DOF), but these factors influence each other by the media scattering. To eliminate this restriction, we propose to explore the underwater wide-area layered light field (UWLLF), which classifies the underwater detection area by the DD and distribution characteristics of the light field, to minimize the scattering influence on target detection. Based on the UWLLF, an underwater electro-optic detection system is designed that can achieve the specifications of a 70° FOV and 7.9-fold attenuation length (for the attenuation coefficient 1.43 /m of 532 nm) DD. In addition, with the spatial separation of light energy, the non-detection zone at short ranges is eliminated, yielding an almost full DOF. With these three factors simultaneously improved, the ability of underwater exploration for object detection is enhanced.

Combination of fluorescence spectroscopy and electrochemical technique as a novel and sensitive electro-optical detection system for gaseous and dissolved oxygen detection using nitrogen-doped quantum dots through the amperomric reduction of oxygen

A novel dissolved and gaseous oxygen electro-optical sensor was fabricated based on the dependency of the fluorescence intensity of a synthesized nitrogen-doped carbon nanodots (N-CDots) during the amperometric reduction of O2 at potential of −0.55V (vs. Ag/AgCl) for about 20s using a three-electrode system including gold rod as worker electrode, platinum rod as counter electrode and Ag/AgCl (3.0molL−1 Cl−) as reference electrode, followed by measuring the fluorescence intensity at excitation wavelength of 350nm. Under optimized condition, i.e. 5.0μgmL−1 of N-CDots, ionic strength of 0.5molL−1 and room temperature, the linear range for the dissolved oxygen was estimated to between 0.11 and 22μgmL−1 with detection limit of 0.07μgmL−1 (n=4). For gaseous oxygen the linear dynamic range was between 3.0 and 48.0% with the limit of detection of 0.95% (n=4). The response time (t90) of the sensor was estimated to be 20s. No interfering effect was observed during analysis of at least 200-fold excess (vs. 2.0μgmL−1 dissolved oxygen) of organic and inorganic species such as, K2SO4, KNO3, MgCl2, MnCl2, NaClO4, NaF, NH4Cl, CaCl2 and Na3PO4, except NO2− and HCO3− which interfered for respectively 12-fold and 75-fold excess. The reliability of the method was also evaluated via analyses of waste and industrial samples.

Static pointing error analysis of electro-optical detection systems

Electro-optical detection systems have been widely utilized in many applications. The pointing accuracy is often seriously affected by static geometric errors. This article analyses the contributions of integrant geometric error sources by means of quaternions, and a parametric model is hence established. As to nonlinear errors, this article further proposes a semi-parametric model that is based on least squares collocation method. Test results demonstrate that both models can improve the pointing accuracy effectively, with latter offering better performance. The estimation variances in azimuth and elevation validation test have been reduced to 0.0014(°)2 and 0.0009 (°)2 from 0.0258(°)2 and 0.0017(°)2, respectively.

Calibration error analysis of electro-optical detection systems

We present detailed analysis of calibration process error for electro-optical detection systems, which can be simplified as the plane rotation around a non-orthogonal axis. By means of octonions it firstly proves that the plane rotation around a non-orthogonal axis can be decomposed into rotations around two perpendicular axes. The rotation is further divided into three steps, and the calibration error is hence discussed and obtained. The simulation and test results indicate that there are large calibration errors in calibration process. The pointing error can be effectively improved after separating error components, which provides a more accurate set data for further compensation.

Laser pointing angle and time of measurement verification of the ICESat laser altimeter using a ground-based electro-optical detection system

The Ice, Cloud, and land Elevation Satellite (ICESat) will begin science operations in 2003 with an emphasis on determination of the ice sheet temporal variations in the Arctic and Antarctic regions. The ICESat bus will serve as the transport for an instrument called the Geoscience Laser Altimeter System (GLAS). GLAS will provide altimetry and lidar measurements with a high level of accuracy. For altimetry, the GLAS data will enable determination of the laser pointing angle to within 1.5 arcsec and the laser pulse time of arrival on the ground to within 100 sec. Both of these data products contribute to the determination of the measured altitude vector from the spacecraft to the ice surface. Verification of both the laser pointing angle and the timing can be achieved by using a unique experimental technique designed to ‘capture’ an altimeter pulse on the surface of the Earth. The capture of the laser pulse is accomplished by covering the illuminated area with devices designed to detect the arrival of energy within the altimeter footprint. This ground-based technique will supply an independent, unambiguous determination of the laser footprint geolocation and the epoch time associated with the arrival of the pulse on the surface. Knowledge of the laser footprint centroid on the ground will infer the laser pointing direction in the geocentric reference frame. This in situ measurement of the footprint geolocation and time of arrival will be compared to the corresponding data products provided by GLAS. The comparison of the GLAS laser pointing and the timing data with an independent measurement will verify the accuracy and/or will indicate the existence of any biases or errors in the generation of the GLAS altimetry data products. The detectors have been designed and tested in the laboratory and analyzed for energy level thresholds, system stability, temperature response and overall performance. Timing hardware has been tested and software has been written to achieve event detection within the desired accuracy.

Single-shot spatiotemporal terahertz field imaging

Using an optically chirped pulse in an electro-optic detection system, we image the spatiotemporal distribution of a terahertz (THz) pulse. We demonstrate single-shot THz field imaging of photoconductive emitters.

Characteristics of a multichannel electrooptical detection system and its application to the analysis of large molecules by fast atom bombardment mass spectrometry

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCharacteristics of a multichannel electrooptical detection system and its application to the analysis of large molecules by fast atom bombardment mass spectrometryJohn S. Cottrell and Syd. EvansCite this: Anal. Chem. 1987, 59, 15, 1990–1995Publication Date (Print):August 1, 1987Publication History Published online1 May 2002Published inissue 1 August 1987https://doi.org/10.1021/ac00142a021RIGHTS & PERMISSIONSArticle Views83Altmetric-Citations87LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

A novel comparator for the location of holes in plates

The paper describes a novel method of determining the positions of circular holes in small flat plates. A prototype has been built using the method and experiments show that good accuracy and speed can be obtained. These are of the order of +or-0.003 mm and 0.5 s per hole respectively. The method uses an electro-optical error detection system, and is a null system which compares plates with a similar reference plate. The results are thus available as comparative measurements among a number of similar plates.