Electro-optical System Research Articles

Weighted Kernel Filter Based Anti-Air Object Tracking for Thermal Infrared Systems.

Visual object tracking is an important component of surveillance systems and many high-performance methods have been developed. However, these tracking methods tend to be optimized for the Red/Green/Blue (RGB) domain and are thus not suitable for use with the infrared (IR) domain. To overcome this disadvantage, many researchers have constructed datasets for IR analysis, including those developed for The Thermal Infrared Visual Object Tracking (VOT-TIR) challenges. As a consequence, many state-of-the-art trackers for the IR domain have been proposed, but there remains a need for reliable IR-based trackers for anti-air surveillance systems, including the construction of a new IR dataset for this purpose. In this paper, we collect various anti-air thermal-wave IR (TIR) images from an electro-optical surveillance system to create a new dataset. We also present a framework based on an end-to-end convolutional neural network that learns object tracking in the IR domain for anti-air targets such as unmanned aerial vehicles (UAVs) and drones. More specifically, we adopt a Siamese network for feature extraction and three region proposal networks for the classification and regression branches. In the inference phase, the proposed network is formulated as a detection-by-tracking method, and kernel filters for the template branch that are continuously updated for every frame are introduced. The proposed network is able to learn robust structural information for the targets during offline training, and the kernel filters can robustly track the targets, demonstrating enhanced performance. Experimental results from the new IR dataset reveal that the proposed method achieves outstanding performance, with a real-time processing speed of 40 frames per second.

Коррекция смаза изображения в оптико-электронных сканирующих системах на борту космического аппарата

The authors analyze the existing ways of blurring elimination. It determines the technique and problem solving procedure of blurring correction in electro-optical scanning systems on board a spacecraft. The proposed technique is implemented at the initial stages of the survey and is based on the optimization of CCD matrix sampling rate according to the maximum of parameters dispersion of brightness image fields. In contrast to the known approaches, brightness differences of adjacent lines of survey route are values to be measured. The results of testing the technique on conditional frames of lines with different degrees of blurring obtained by distorting the signals of a real space image are presented. The authors’ new approach based on the established functional relationship between the level of blurring, survey parameters and errors of their determination was applied for the blurring simulation. The obtained results prove the possibility of reducing the initial blurring of images being formed on board a spacecraft to the magnitude of tenths of a pixel.

Aperiodic electro-optic time lens for spectral manipulation of single-photon pulses

Electro-optic time lenses are promising experimental components for photonic spectral-temporal processing of quantum information. We report a stable method to realize an electro-optic time lens, which relies on the amplification of an electronic response of a fast photodiode. The method does not require a repetitive clock and may be applied to aperiodic optical signals. We experimentally demonstrate the approach using single-photon pulses, and directly verify its aperiodicity. The approach will enable the construction of complex electro-optic temporal optical systems.

A Mathematical Model of the Detection Probability of the Point Target by the Operator of the Payload Electro-Optical System for Unmanned Aerial Vehicle

The paper deals with a mathematical model of the probability of detection of a point target by the operator of the payload of an optoelectronic device installed on an unmanned aerial vehicle, based on the use of the Johnson criterion and the binomial law of repeated tests

Background-suppressed SRS fingerprint imaging with a fully integrated system using a single optical parametric oscillator.

Stimulated Raman Scattering (SRS) imaging can be hampered by non-resonant parasitic signals that lead to imaging artifacts and eventually overwhelm the Raman signal of interest. Stimulated Raman gain opposite loss detection (SRGOLD) is a three-beam excitation scheme capable of suppressing this nonlinear background while enhancing the resonant Raman signal. We present here a compact electro-optical system for SRGOLD excitation which conveniently exploits the idler beam generated by an optical parametric oscillator (OPO). We demonstrate its successful application for background suppressed SRS imaging in the fingerprint region. This system constitutes a simple and valuable add-on for standard coherent Raman laser sources since it enables flexible excitation and background suppression in SRS imaging.

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).

Analysis of Factors Affecting the Efficiency of Electro-Optical Systems

According to present knowledge thermal imaging electro-optical surveillance systems with object detection are widely used in various fields of human activity. Thermal imagers use infrared radiation emitted by objects and people, so it makes possible to take a sight in complete darkness and miscellaneous weather conditions. Typical applications of this technology are security and surveillance systems, along with autonomous navigation industries in aircraft and ground vehicle. The aim of the work is to determine the necessary condition for an accurate parameter estimation of the electro-optical systems allowing for adverse externalities.First of all, the various infrared spectrum ranges will be considered and corresponding wavelengths will be pointed for each of the following. Thermal imaging cameras are capable of receiving emission from an object in the infrared spectral ranges, which have an atmospheric transparency window, i.e. MWIR and LWIR.<p >Then the structural diagram of the phased generation process of infrared images in thermal imaging systems will be discussed. It appears that, the image formation chain includes such components as irradiation source, optics, imaging sensor, read-out electronics, processing electronics, compression and transmission of data, decoding, search & track engine, display and finally human observer.The next chapter will describe the probability method of detecting objects based on the effective resolution of the depicted object. There will be resulted the table of visual perception levels, namely orientation, recognition, identification. And relative levels of perception will be provided the corresponding resolution of the image.The next section will analyze the factors affecting the objects identification. Before the radiation from the object reaches the thermal imaging sensor optics, it must go through many obstacles, which include atmospheric factors such as precipitation and air condition (humidity, temperature), solar radiation, etc. Various equations and models will be carried out to take into account the above factors. For example, Johnson's criterion, and a more advanced Target Task Performance recognition model.This paper considers the main criteria for detecting objects using electro-optical systems in the infrared range. The robust analysis of literature sources will be conduct and describe the basics of visualization and the infrared imaging in thermal systems. Then Johnson criteria, which is considering for calculating the efficiency of electro-optical systems, will be evaluated for validity using in real-world environment. Also, it will be pointed out, that the greatest negative contribution on visualization is made by weather and atmospheric conditions, clutter effects and density, motion-blur and defocusing, along with target properties – aspect ratio and viewing angle. Finally, it will be suggested prediction models and software packages that will help determine the real characteristics of the elaborate device and identify the weak link of the system.

Robust chaotic-shift-keying scheme based on electro-optical hybrid feedback system.

A chaotic-shift-keying (CSK) scheme is designed based on a chaos system with electro-optical hybrid time delayed feedback structure. By switching the time delay parameter as a message feeding method, the generated chaotic signal is no longer suffered from return map attack, which is an innate vulnerability of traditional CSK. When the coupling of the seed electrical chaotic system and the nonlinear optical time delay feedback loop is carefully weighed, this CSK scheme shows a good robustness in terms of handling noise for transmitting digital signals. By demodulating the digital signals with the chaotic coherent detection method, a bit error rate of 6×10-4 is achieved at the signal-to-noise ratio of 10dB in the simulation. The proposed method has a promising application prospect in some harsh environments.

Performance Improvement of Electro Optic Search and Track System for Maritime Surveillance

Surveillance of maritime domain is absolutely vital to ensure an appropriate response against any adverse situation relating to maritime safety or security. Electro-optic search and track (EOST) system plays a vital role by providing independent search and track of potential targets in marine environment. EOST provides real-time images of objects with details, required to neutralise threats. At long range, detection and tracking capability of EOST degrades due to uncertainty in target signatures under cluttered scenario. Image quality can be improved by using suitable sensors and enhancement using the target/background signature knowledge. Robust tracking of object can be achieved by optimising the performance parameters of tracker. In the present work, improvement in the performance of EOST subsystems such as sensor, video processor and video tracker are discussed. To improve EOST performance in terms of detection and tracking, sensor selection criterion and various real time image processing techniques and their selection criteria for maritime applications have been also discussed. Resultant improvement in the quality of image recorded under marine environment has been presented.

Immobilization of Bioengineered Portal Protein Within a Solid-State Nanopore for Molecular Sensing

Site-specific, reproducible, and uniform-orientation protein immobilization on an inorganic surface while preserving protein conformation and activity is of wide interest for applications in biosensing, protein microarrays, and enzymology, among others. Successful immobilization requires understanding of material's surface chemistry, protein properties, and nature of their interaction to eliminate non-specific binding. Portal protein is a naturally occurring pore (biological nanopore) and part of the bacteriophage packaging machine that pumps the viral genome inside its capsid. In this work, we have explored different approaches to immobilize G20c portal protein from double-stranded bacteriophage G20c into a thin (∼30 nm) silicon nitride (SiNx) membrane embedded in a silicon chip. Desired orientation of the immobilized protein is achieved by maintaining a voltage bias across the membrane to electrokinetically drive a single protein into the synthetic nanopore. The nanopore geometry dictates a predominant favorable protein orientation while the portal preserves its conformation, as indicated by ion current measurements through the “hybrid nanopore”. Application of nanopores (both synthetic and biological) as label-free, single-molecule biosensors for electrical and/or optical probing of structural features in biomolecules have been widely explored. Confirmed by our single-molecule electrical sensing results, our hybrid nanopore system provides mechanically robust and chemically compatible synthetic protein framework, superior to its natural counterparts such as organic membranes (lipid bilayer, for example), and exploits tunable and engineerable characteristics of thermostable G20c portal protein rendering an active, high-resolution biomolecule sensing platform. We demonstrate here through chemical functionalization of synthetic nanopores and/or engineering G20c portal protein assemblies, a protein nanopore chemically linked to a synthetic nanopore, rendering considerably improved protein stability, sensing lifetime, and signal-to-noise ratio compared to our previous hybrid system. This development will be widely applicable to coupled nanopore sensor arrangements such as electro-optical and electro-pressure systems.

Experimental Investigation of the Spatial and Temporal Evolution of the Tangential and Normal E-Field Components along the Stress Grading System of a Real Stator Bar

This paper presents results based on direct experimental measurements of tangential (Et) and normal (En) E-field components along the stress grading system (SGS) of a real stator bar (Roebel type) for different AC 60 Hz applied voltages. These measurements were made with a new electro-optic system allowing for the study of both spatial distributions of two E-field components along the bar and their temporal evolution at critical points. The results obtained allowed us to calculate the correlation between the distribution of En and Et along the SGS. In particular, it was demonstrated that the En distribution presents a characteristic minimum, which can be used to identify the zone of partial discharge inception. Moreover, it was possible to observe an enlargement of the Et component distribution followed by a saturation in magnitude with the applied voltage increase. Moreover, the results have demonstrated that the waveform of the En component is mostly affected by the SG material used, producing a greater distortion in its waveform than those obtained for the Et component. The more significant distortion was obtained at the end of the outer corona protection (OCP) material, corresponding to the first maximum of the En component and characterized by the appearance of a third harmonic of large amplitude.

Global Motion-Aware Robust Visual Object Tracking for Electro Optical Targeting Systems.

Although recently developed trackers have shown excellent performance even when tracking fast moving and shape changing objects with variable scale and orientation, the trackers for the electro-optical targeting systems (EOTS) still suffer from abrupt scene changes due to frequent and fast camera motions by pan-tilt motor control or dynamic distortions in field environments. Conventional context aware (CA) and deep learning based trackers have been studied to tackle these problems, but they have the drawbacks of not fully overcoming the problems and dealing with their computational burden. In this paper, a global motion aware method is proposed to address the fast camera motion issue. The proposed method consists of two modules: (i) a motion detection module, which is based on the change in image entropy value, and (ii) a background tracking module, used to track a set of features in consecutive images to find correspondences between them and estimate global camera movement. A series of experiments is conducted on thermal infrared images, and the results show that the proposed method can significantly improve the robustness of all trackers with a minimal computational overhead. We show that the proposed method can be easily integrated into any visual tracking framework and can be applied to improve the performance of EOTS applications.

Adaptive position calibration technique for an optical micro-scanning thermal microscope imaging system

In order to improve the spatial resolution of an optical micro-scanning thermal microscope system, the micro-scanning position must be accurately calibrated. An adaptive calibration method based on image registration and plane coordinate system is proposed. The meaning of calibration is given, and the principle and method of point calibration are introduced in detail and experiments using the real system were done. Different reconstruction methods were applied to reconstruct the visible light image and the real thermal microscope image, and the evaluation scores are given. Results of simulation and real thermal imaging processing show that the method can successfully calibrate the micro-scanning position. The method can significantly improve the oversampled reconstructed image quality, thus enhancing the spatial resolution of the system. This method can also be used in other electro-optical imaging systems.

Objective evaluation method for advance thermal imagers based on minimum resolvable temperature difference

Advancement in thermal imaging technology has improved the day and night surveillance capability of electro-optical system. Thermal imager detects the object of interest by sensing the temperature difference. The performance evaluation of these thermal imagers plays a vital role prior to effective deployment. Key performance parameter of thermal imaging system is minimum resolvable temperature difference (MRTD), as it is able to determine the overall system performance involving a human operator. MRTD is capable of defining the minimum temperature difference required to resolve the bar target pattern of defined spatial frequencies and provides the true estimate of the range performance of a thermal imaging system. In conventional methods, 4-bar target of defined resolution is exposed to the minimum resolvable condition to compute MRTD values. Presently, subjective MRTD measurement employs an operator to observe the minimum resolvable condition, and therefore, measurement suffers from poor repeatability. During large volume production, this practice becomes a tedious procedure to evaluate large numbers of thermal imaging sights. To ease the performance evaluation procedure, an objective MRTD measurement method for the evaluation of the thermal imaging system has been presented. In the present work, objective MRTD measurement method for advance thermal imager by computing the modulation transfer function and noise equivalent temperature difference has been presented. Experiments have been conducted to measure subjective and objective MRTDs. Results for both subjective and objective MRTD measurements have been compared and presented. It is found that the proposed method is able to produce very close result within accuracy of more than 95% than that of conventional methods.

Modulaciona funkcija prenosa u analizi performansi elektrooptičkih sistema

Introduction/purpose: The Modulation Transfer Function (MTF) is a useful tool for an imaging system performance analysis. It is used in Electro-Optical (EO) system design, verification of targeted system parameters, but also in optimization tasks for systems under test. This methodology based on the linear systems theory allows the performance analysis of complicated EO systems to be divided into subsystems. In this paper, the MTF methodology will be presented and explained, followed by the measurements performed in the electro-optical laboratory. The MTF measurements were performed on three types of cameras spectral bands, after which the results were compared to in different the model expectations and theoretical limits for the imaging system. For one of the sensors, the limiting frequency was also measured using the USAF 1951 test target which allowed the comparison between the methods. Methods: Laboratory measurements and theoretical mathematical calculations. Results: Based on the laboratory and theoretical results, the measurement results were further analyzed. Conclusion: The measurements have proven that the calculated cutoff frequency and the MTF curve represent the limit for the real measured system performance. Therefore, this study has confirmed that the MTF can be convenient for finding system limitations and bottlenecks and for increasing the overall performance of the system.

REGISTRATION OF OPTICAL IMAGES OF A VACUUM ARC DISCHARGE WITH AN ELECTRON-OPTICAL CONVERTER WITH NANOSECOND TIME RESOLUTION

Abstract—The process of switching a short vacuum gap by an auxiliary discharge over the dielectric surface was studied via recording of images of discharge plasma radiating in the optical spectral range. A two-channel electro-optical (EO) image-recording system based on an EO converter (EOC) was used. Each channel contained a unit for generating an EOC-photocathode gating pulse, a transposing objective lens, and an EOC, which was joined to a digital CCD (charge-coupled device) camera for reading information from the EOC screen. Based on the analysis of the obtained experimental data, it was suggested that the radiation of a cathode spot and a cathode flame in the UV range play a significant role in the formation of a current channel in the discharge.

Physical foundation of requirements for developing advanced information processing algorithms in television links of electrooptical systems

Physical foundation of requirements for developing advanced information processing algorithms in television links of electrooptical systems

전자광학시스템의 비행체 움직임 보상을 위한 시선유지 알고리즘에 관한 연구

본 논문은 비행체 자세 변화를 보상하기 위한 전자광학시스템의 시선유지 알고리즘을 제안한다. 오일러각을 이용하여 비행체-전자광학시스템 좌표축과 회전 관계를 정의하고 전자광학시스템의 시선 벡터를 산출했다. 정의한 수식을 이용하여 전자광학시스템 구동 각도에 대해서 정리한 수학적 모델을 만들어서 비행체 자세 변화가 없는 초기 상태의 시선 벡터를 기준으로 외부 요인으로 인해서 변화된 롤, 피치, 요 방향의 비행체 자세를 대입하여 시선 유지를 위한 전자광학시스템의 구동각도 명령을 생성했다. 롤, 피치, 요 방향으로 비행체 자세 변화를 모사한 시뮬레이션을 통해 시선유지 알고리즘을 적용한 시선유지 결과와 적용하지 않은 시선유지 결과를 비교하여 제안한 알고리즘을 검증했다. 시선유지 알고리즘을 적용한 결과는 롤, 피치, 요 방향의 비행체 자세 변화에 따라서 전자광학시스템의 구동 각도를 생성했고, 비행체 움직임이 발생한 상태에서 생성된 구동 각도를 입력한 시선과 초기 시선이 일치함을 확인했다.

Realization of an Analog Computing Circuit for Simulating a Chaotic Electro Optic System and Validation of Model using Lyapunov Exponent

Chaotic optical communication is attractive for its security because in such type of communication optical signal is encrypted using the optical chaos and decrypted at the receiver side with identical chaotic key. Chaotic signals are created using nonlinear optical systems with sensitive dependence in initial condition. In our work we have chosen an Electro Optic modulator based nonlinear optical system for producing optical chaos. However the optical devices are costly and not easily accessible. Hence to overcome this difficulty we have created a nonlinear analog computing circuit capable of producing chaotic signals as those of nonlinear Electro Optic or Acusto Optic system. Extensive numerical experiments have been conducted on this electronic system for studying its chaotic behaviour and it has been found that our electronic simulator is able to mimic the actual Electro Optic system up to a large extent.

Progress and opportunities in the development of nonmechanical beam steering for electro-optical systems

We discuss over three decades of progress in nonmechanical beam steering, provide a comparison of approaches being developed, and comment on promising approaches not yet fully developed. Most of the work in nonmechanical beam steering has been for narrowband optical systems, but a brief discussion is provided of broadband. The majority of the nonmechanical approaches to beam steering create a tilted optical path delay (OPD) to change the wavefront, but some directly create a phase delay. OPD-based approaches may be true time delay, with no resets or modulo 2π n optical phased arrays that have resets. Most of the nonmechanical optical beam steering approaches tilt an existing wavefront and are called space fed approaches, because the beam is already formed when the wavefront is tilted. For the majority of radar nonmechanical beam steering, the tilted wavefront is formed by individual transmit/receive modules. Periodic structures (gratings) spread different wavelengths of light in angle, thus steering light, and are also used for nonmechanical steering. Our paper is derived from a conference paper presented at Photonics West in February 2019.