Showing papers in "Opto-electronic Engineering in 2020"
TL;DR: It is proposed that multi-intelligence cooperative optoelectronic system is the key development direction in the field of optical-electric tracking in the future, and it is necessary for the system to develop multi-agent cooperative positioning, formation control and load platform integration and other precise control technologies.
Abstract: Precision control methodologies are necessary to implement high-precision optical-electric tracking performance, and depend on structural configuration, actuator drive, sensors, control algorithm and load platform. However, the optical-electric tracking system is facing with the three key technologies, disturbance rejection, target tracking and distributed intelligent coordination, both foundation platform and moving platform. In this paper, precision control methodologies aiming at the above several key technical problems are summarized, and the research results of some advanced and frontier control technologies are presented and the main ideas of the future key research directions are pointed out. In addition, the research progress and hotspot of disturbance rejection technology from three aspects of precision drive, inertial stability as well as vibration control according to the different mechanism of disturbance influence are introduced, and the integrated technology of vibration and direction based on Stewart platform is an important technical direction of space optical-electric tracking system are emphasized. The composite axis control system is still the most effective fundamental way to improve the target tracking, and the most essential technical problem is to improve the closed-loop performance of the tip-tilt mirror system in precision tracking. It has to be mentioned that observer control is especially suitable for composite axis optical-electric tracking system, especially the observer technology based solely on error, and the development of three or more advanced composite shaft systems has to pay special attention to the application of high performance motors. Eventually, it is proposed that multi-intelligence cooperative optoelectronic system is the key development direction in the field of optical-electric tracking in the future, and it is necessary for the system to develop multi-agent cooperative positioning, formation control and load platform integration and other precise control technologies.
13 citations
TL;DR: In this article, the development of laser cleaning technology both at home and abroad in recent years is reviewed, the work has provided a theoretical basis and ideal reference for the application of Laser cleaning in the petrochemical field.
Abstract: Laser cleaning is a surface engineering technology which uses the high-energy characteristic of laser to remove attachments on the substrate. It has been gradually promoted in the fields of microelectronics, mould, building, aerospace, and so on. However, as a pillar industry of national economy, there are rare reports on the application of laser cleaning technology in petrochemical industry. In this paper, the cleaning needs and technology status of petrochemical industry are introduced, the existing technology cannot fully meet the new requirements of petrochemical industry development. The development of laser cleaning technology both at home and abroad in recent years is reviewed, the work has provided a theoretical basis and ideal reference for the application of laser cleaning in the petrochemical field. And the application occasions of laser cleaning technology in petrochemical field are analyzed. In addition, the specific research directions and application prospect are pointed out.
12 citations
TL;DR: The technical characteristics of advanced (new generation) optical manufacturing are summarized, the future manufacturing strategy of large-diameter aspheric mirrors is looked forward to, and the resolution of imaging system can be increased by improving the system aperture.
Abstract: The aspheric surface can correct the system aberration and improve the image quality in the optical imaging system, in addition to that it can simplify the system structure significantly; On the other hand, the resolution of imaging system can be increased by improving the system aperture. Therefore, in the domain of basic scientific research, astronomical cosmological exploration and military defense security the large-aperture aspheric mirrors are all highly required. The manufacturing of large-aperture aspheric mirrors plays a critical role in modern optical engineering. This paper focuses on the advanced manufacturing techniques of large-aperture aspheric mirrors. The optical manufacturing technologies, especially the grinding and polishing techniques of large-aperture aspheric mirrors in the past half century and the surface shape testing methods during the grinding and polishing process, are reviewed. In particular, it summarizes the technical characteristics of advanced (new generation) optical manufacturing, and looks forward to the future manufacturing strategy of large-diameter aspheric mirrors.
11 citations
TL;DR: In this article, a brief overview of typical research cases related to the application mechanisms of OAM-based optical communication systems is presented. And three key technologies have been discussed, including OAM beam multiplexing (OAM beam demodulation), OAM shift keying, and turbulence suppression technology.
Abstract: Orbital angular momentum (OAM) carried by the vortex beam provides a new dimension resource in the spatial domain of light waves, which attracting more and more researching attentions. Since the vortex beams with different OAM mode values are orthogonal to each other, the OAM mode is introduced into the field of traditional optical communication, and two new application mechanisms are derived: OAM shift keying (OAM-SK) and OAM division multiplexing (OAM-DM), which provides a potential solution for future high-speed, high-capacity and high-spectrum efficiency optical communication technologies. Based on the basic concepts and theories of OAM beam types and their generation methods, this paper will give a brief overview of typical research cases related to the application mechanisms of these two communication systems. Three key technologies have been discussed, including OAM beam multiplexing technology, OAM beam demodulation technology, and turbulence suppression technology of OAM-based optical communication. Finally, the future developing trends and prospects of OAM-based optical communication technology are analyzed and forecasted.
11 citations
TL;DR: In this article, the principle and realization method of asymmetric photon spin-orbit interactions was introduced, and representative applications and characteristics of asymmetrical photon-spinorbit interactions were discussed.
Abstract: Photonic spin-orbit interaction is an important phenomenon ignored by classical optics. In recent years, studies have found that this phenomenon can be significantly enhanced by artificial subwavelength structures and adjusted on demand. Traditional metasurfaces only support symmetric photon spin-orbit interactions, and there are limitations in conjugate symmetry, which makes it difficult to use different spin states for multifunctional integration, complex optical field regulation, information encryption, and storage. The asymmetric photon spin-orbit interaction can decouple left and right circularly polarized light, which brings new opportunities for breaking the above-mentioned theoretical and application limitations. This article first introduces the principle and realization method of asymmetric photon spin-orbit interactions, secondly introduces the representative applications and characteristics of asymmetric photon-spin-orbit interactions, and finally outlines the challenges and prospects of asymmetric photon spin-orbit interactions for future research directions.
10 citations
TL;DR: Terahertz radiation is an electromagnetic wave whose frequency is in the range of 0.1 THz~10 THz as discussed by the authors, and it has many potential applications in biomedical field, especially in tumor detection.
Abstract: Terahertz radiation is an electromagnetic wave whose frequency is in the range of 0.1 THz~10 THz. With its many features such as non-ionizing and resonance to many biomolecules, THz wave has great potential applications in biomedical field, especially in tumor detection. Terahertz imaging technology, as a new imaging technology in biomedical field, is studied by many research groups around the world. In this paper, we listed and analyzed many terahertz imaging methods in tumor detection, including terahertz scanning imaging, terahertz tomography, terahertz holography, and terahertz near-field imaging. We introduced the basic principle of these imaging methods and the works done by different groups worldwide. At last, we presented the prospect of terahertz imaging technology applied in biomedical field.
8 citations
TL;DR: In this article, a moisture-proof seal fiber connector is proposed to solve the problem of water mist condensation on the fiber end face in a high-power fiber laser system.
Abstract: Aiming at the problem of water mist condensation on the fiber end face in a high-power fiber laser system, the most important factor causing this problem is that the traditional optical fiber connector does not have the mois-ture-proof sealing performance. The connector structure assembly and use process are analyzed in-depth, and the causes of the moisture-proof seal defects are pointed out. Through technological innovation and process improvement, a moisture-proof seal fiber connector is designed and completed. The principle and structure of the moisture-proof seal of the new connector are introduced. The main performances of the new connector are tested comprehensively, including immersion test, constant damp heat test, online application test. The experimental results show that the new connector has a better moisture-proof seal with IL less than 0.2 dB.
8 citations
TL;DR: In this article, a review summarizes the recent critical progress in manufacturing of large-aperture optics in high-power laser facility and emphasizes the technologies such as single point diamond fly-cutting, and aspheric ultra-precision grinding, as well as deterministic polishing, based on the deterministic ultraprecision process manufacturing method.
Abstract: The construction of high-power solid-state laser facility for inertial confinement fusion requires to precisely control the full-spatial frequency error, and realize efficient mass-manufacturing of large-aperture optics. This review summarizes the recent critical progress in manufacturing of large-aperture optics in high-power laser facility. It also emphasizes the technologies such as single point diamond fly-cutting, and aspheric ultra-precision grinding, as well as deterministic polishing, based on the deterministic ultra-precision process manufacturing method. In addition, the application status of these key technologies in the mass-manufacturing chain was stated specifically.
7 citations
TL;DR: In this paper, a gauge measurement method based on the relative transverse movement of wheel and rail is designed, where two sets of laser source and camera combinations are used to dynamically collect the image of the inner straight line part of the rail head in the method.
Abstract: Aiming at the complexity of the traditional gauge detection method, high requirements for the installation and large amount of data analysis, a gauge measurement method based on the relative transverse movement of wheel and rail is designed in this paper. Two sets of laser source and camera combinations are used to dynamically collect the image of the inner straight line part of the rail head in the method. According to the rail parameters, the Hough detection and perspective transformation are used to rectify the image from the same acquisition distance. Compared to datum moment, the variation of vertical displacement of the center point of the laser is computed. And through the geometrical relation of the variation previously described and the lateral relative displacements of the two wheels, the relative transverse displacement of the two wheels is calculated. The relative initial time gauge change is gained by the difference, which realizes the indirect measurement of the track gauge. The experimental results show that the method has the characteristics of simple hardware structure, small data calculation, high measurement precision, and can realize non-contact dynamic measurement of gauge parameters.
7 citations
TL;DR: In this article, Gaussian function is used to fit the distribution of the fiber core in optical fiber core, and the real edge of fiber core and cladding can be obtained from the Gaussian functions after fitting.
Abstract: The geometry parameters of optical fiber affect the optical transmission and mechanical properties, which are the important indexes to measure the quality of fiber. Near-field light distribution method is recommended in GB15972.20-2008 for the measurement of geometry parameters. In order to distinguish the boundary between fiber core and cladding, the method needs to illuminate the fiber. The end face of the fiber core is a bright spot with unclear edge, so the true edge of the core and cladding cannot be accurately judged. In this paper, the distribution of mode field in optical fiber is analyzed. Theoretically, the solution of electromagnetic vector of mode field satisfies Bessel function, but Gaussian function can also be used under approximate conditions. Therefore, Gaussian function is used to fit the distribution of the fiber core in this paper, and the real edge of the fiber core and cladding can be obtained from the Gaussian function after fitting. This method is a further improvement on the measurement method of GB15972.20-2008. The experimental results show that when the cutting effect of the fiber is not good or the imaging quality is poor, the Gaussian function method fitting with mode distribution can still ensure the repeatability of the measurement and the stability of the measured data.
7 citations
TL;DR: In this paper, a dynamic correction method for laser pointing based on bias tracking is proposed, which keeps the target always at the center of the laser beam and keeps the laser ranging position consistent with the theodolite tracking and locking position.
Abstract: The distance between the laser optical axis and the tracking optical axis of the theodolite (axis shift) and the parallelism error of the optical axis cause the tracking position of the theodolite to be inconsistent with the laser pointing position.The analysis of the influence of off-axis and parallelism errors shows that a large amount of shift and parallelism errors will lead to inconsistencies between the laser pointing and the theodolite tracking pointing, which in turn leads to an increase in the blind zone of the laser ranging, a decrease in the operating distance and the accuracy of target positioning. A dynamic correction method for laser pointing based on bias tracking is proposed. By keeping the target always at the center of the laser beam and keeping the laser ranging position consistent with the theodolite tracking and locking position, it effectively solves the effect of laser edge energy drop on the operating distance. For a certain type of theodolite, the blind spot of the target can be reduced from 1 km to 82 m. At the same time, in view of the problem that the bias tracking algorithm needs the initial distance of the target to start the bias tracking, a one-dimensional search method for the target with unknown initial distance is proposed, which greatly improves the search efficiency of the target with unknown initial distance. The method in this paper solves the problem of the consistency between the tracking position of the theodolite and the pointing position of the laser, and greatly reduces the limitation on the shift and parallelism of the laser optical axis and the theodolite tracking optical axis
TL;DR: It is concluded that the key technologies in urgent need of breakthrough for nuclear robots are radiation reinforcement, communication method, photoelectric detection, intelligent control technology, etc.
Abstract: To introduce and analyze the development history and research status of operating robots for nuclear environment at home and abroad, the common system structure and classification based on main functions for operating robots for nuclear environment are summarized. Based on the application requirements of operating robots for nuclear environment, it is concluded that the key technologies in urgent need of breakthrough for nuclear robots are radiation reinforcement, communication method, photoelectric detection, intelligent control technology, etc. Finally, with the increasing scale of China's nuclear industry and the increasing demand for safety assurance, the application scenarios of operating robots for nuclear environment are condensed, and the future development trend of operating robots for nuclear environment is predicted.
TL;DR: In view of the problem of large target size span existing in FLIR dataset, the SPP module is added with reference to the idea of the spatial pyramid to enrich the expression ability of feature map, expand the receptive field of feature maps, and further improve the accuracy of target detection.
Abstract: The mainstream target detection network has outstanding target detection capability in high quality RGB images, but for infrared images with poor resolution, the target detection performance decreases significantly. In order to improve the performance of infrared target detection in complex scene, the following measures are adopted in this paper: Firstly, by referring to the field adaption and adopting the appropriate infrared image preprocessing means, the infrared image is closer to the RGB image, so that the mainstream target detection network can further improve the detection accuracy. Secondly, based on the one-stage target detection network YOLOv3, the algorithm replaces the original MSE loss function with the GIOU loss function. It is verified by experiments that the detection accuracy on the open infrared data set the FLIR is significantly improved. Thirdly, in view of the problem of large target size span existing in FLIR dataset, the SPP module is added with reference to the idea of the spatial pyramid to enrich the expression ability of feature map, expand the receptive field of feature map, and further improve the accuracy of target detection.
TL;DR: In this paper, the Laguerre-Gaussian vortex beam and Rayleigh diffraction theory were used to study the variation of rotating coherence function of vortex beam propagating in atmospheric turbulence.
Abstract: Starting from the expression of Laguerre-Gaussian vortex beam and based on Rayleigh diffraction theory, the variation of rotating coherence function of vortex beam propagating in atmospheric turbulence is studied. The crosstalk between the angular momentum of each orbital angular momentum when the vortex beam propagates in atmospheric turbulence is summarized. The topological charge detection probability is used to describe the crosstalk law, and the analytical expression of the topological charge detection probability is derived. The distribution of topological charge number of vortex beam passing through turbulence is studied, and the results are compared with the numerical simulation results of vortex beam passing through atmospheric random phase screen. The relationship between the detection probability of the theoretical and simulated topological charge numbers with the turbulence intensity and the topological charge number of the initial vortex beam is compared, and the correctness of the analytical expression of the topological charge number detection probability is verified. Through this expression, the interaction between atmospheric turbulence and vortex beam can be further studied, which can affect the essence of angular momentum scattering of vortex beam, and the suitable topological charge number interval can be selected for the space optical communication of vortex beam. It also provides a theoretical basis for selecting the appropriate beam waist size under different turbulence intensities to reduce the bit error rate (BER) caused by crosstalk.
TL;DR: In this article, the authors summarized the principles, measurement precisions and application scenarios of these residual stress measurement methods are summarized in this overview, and correlations between them are analyzed in detail.
Abstract: Residual stress is an important performance indicator of optics, which is of great significance to the fabrications and applications of optical components. Residual stress measurement methods of optics can be summed up into two categories: methods based on the strain measurement and on the stress induced birefringence measurement, respectively. The strain based methods, which are built upon crystal dynamics and elastic mechanics, including X-ray diffraction (XRD), Stoney curvature method, and micro-Raman spectroscopic method, are well developed and widely used. Methods based on the measurements of birefringence phase retardation induced by residual stress, including digital photoelasticity method, photoelasticitic modulator (PEM) method and polarization-dependent cavity ring-down method, show a higher precision. The principles, measurement precisions and application scenarios of these residual stress measurement methods are summarized in this overview. Comparisons between the performances of these methods are performed and correlations between them are analyzed in detail.
TL;DR: The improved method in this paper can distinguish line Mura defect on the mobile phone screen more accurately and quickly and is based on the principle of mean filter to smooth the picture and down-sampling.
Abstract: Automatic identification and location of Mura defect in various screens plays an important role in improving the quality of screens. It is one of the most important technologies that need to be developed urgently. Aiming at the features of low contrast and lack of obvious edge of Mura defect, this paper proposes a method of Mura detec-tion based on image gray curve and its improved method. This improved method is based on the principle of mean filter to smooth the picture and down-sampling. By studying the information about peak and trough of the gray curve on sampling lines, the BP neural network is used to construct an automatic detection and location algorithm for line Mura. The experimental results show that, compared with the existing Mura detection methods, the improved method in this paper can distinguish line Mura defect on the mobile phone screen more accurately and quickly. The accuracy rate is 98.33%, and no parameter needs to be adjusted during the detection process, realizing automatic detection, and positioning of line Mura.
TL;DR: A cylindrical image mosaic method based on fast camera calibration in multi-scene is proposed to solve the problems of scene limitation and complex calibration process in image mosaic using camera calibration parameter.
Abstract: A cylindrical image mosaic method based on fast camera calibration in multi-scene is proposed to solve the problems of scene limitation and complex calibration process in image mosaic using camera calibration parameter. Firstly, the accurate corner feature of checkerboard calibration board is used to make it in the overlapping field of view of two adjacent images. Then, the image sequence is pre-processed by corner extraction, precision and matching, so that the registration parameters between the images to be stitched can be solved accurately and quickly. After that, the cylindrical projection is used to maintain the visual consistency of the images, and the multi-band fusion is used to retain the details of the images. Subsequently, the images are stitched using registration parameters obtained by calibration. Finally, the whole system is built on a low-power embedded platform to accomplish fast calibration and mosaic process based on calibration parameters in multi-scene. The experiment results show that the proposed method can accomplish camera calibration quickly and accurately in indoor and tunnel scenarios, and the image mosaic process is time-consuming. Meanwhile, it can ensure better stitching accuracy and imaging effect, and has strong robustness.
TL;DR: In this paper, the lateral support structure with a mercury band and central shaft was investigated, and the impact of the mercury band parameters on the surface error was analyzed, and it was shown that the designed lateral structure has small size and improves the surface quality of the mirror.
Abstract: The main function of the laser communication large-caliber ground optical transceiver is to establish a communication link with the satellite to realize data transmission between the satellite and the ground station. The 600 mm microcrystalline primary mirror of one laser communication station is heavy, and its working angle changes constantly. In order to decrease the mirror surface error, the support system not only has a 9-pose axial support structure but also simultaneously balances the radial component of gravity of the primary mirror at its working angle by using a radial support structure. Flexible lateral support structures have large size and stress, so it is not suit for the mirror that works in a wide range of rotation. The paper researches the lateral support structure with a mercury band and central shaft, and analyses the impact of mercury band parameters on the surface error. The designed lateral structure has small size and improves the surface quality of the mirror. The measured values of PV and RMS are smaller than λ/5 and λ/37, respectively. These result shows that the designed lateral support structure reaches the design purpose and satisfies the requirements.
TL;DR: In this paper, a variable-inclination Mach-Zehnder interferometer was proposed to measure the transmission wavefront of laser rods and to improve the edge diffraction effect of small-aperture laser rods measured by Tayman or Fizeau interferometers.
Abstract: In order to measure the transmission wavefront of laser rods and to improve the edge diffraction effect of small-aperture laser rods measured by Tayman or Fizeau interferometer, a variable-inclination Mach-Zehnder interferometer was proposed. The incident angle was changed by adjusting the tilting attitude of the phase shifting reflector, then the optical path difference was changed that the phase shift was introduced to the coherent light and the phase shifting interferometry was realized. The transmission wavefront of a laser rod (Nd:YAG) with the diameter of 6 mm and the length of 60 mm was measured by this interferometer, the peak-valley (PV) and root mean square (RMS) of the wavefront were 0.391λ and 0.056λ. The same laser rod was measured by ZYGO GPI XP interferometer, the peak-valley (PV) and root mean square (RMS) were 0.370λ and 0.064λ. The comparison results show that the interferometer can achieve high-precision detection of transmission wavefront of laser robs. The variable-inclination Mach-Zehnder interferometer has high phase-shifting precision and wide phase-shifting range, and the beam in the system can pass through the laser rod only once, which can suppress the multi-beam interference and improve the edge diffraction effect of the small-aperture laser rods.
TL;DR: In this article, the effects of different types of clouds on laser energy attenuation, signal-to-noise ratio (SNR), maximum symbol transmission rate and bit error rate are simulated and analyzed.
Abstract: When the airborne laser transmitter is located above or in the center of the cloud, the cloud will reduce the laser communication performance. In order to solve this problem, the effects of different types of clouds on laser energy attenuation, signal-to-noise ratio (SNR), maximum symbol transmission rate and bit error rate are simulated and analyzed. It is concluded that the cloud mainly causes laser energy attenuation, which affects maximum transmission rate and bit error rate, but has little effect on SNR. For communication systems with link margin greater than 18.9 dB, 4 km cloud cover is allowed on the link. The effect of cloud on the maximum communication rate and bit error rate is mainly caused by inter-symbol crosstalk caused by time extension. Cirrus has little effect on communication performance, cumulus has a great impact on communication performance, and stratus, stratocumulus, and cumulonimbus have a greater influence on the communication performance, but the differences between the three types of clouds are small and could be not be distinguished. Altostratus cloud and nimbostratus have greatest influence on communication performance, of which nimbostratus has greater influence than altostratus cloud.
TL;DR: In this article, a review of the fabrication advancement of X-ray reflect mirror fabrication in terms of technical requirements, fabrication and metrology development is presented, where the fabrication of such mirrors requires highly specialized equipment and technology that only a few foreign optic manufacturers possess, whereas manufacturers in China is laggard in this area.
Abstract: This article reviews on the fabrication advancement of X-ray reflect mirror fabrication in terms of technical requirements, fabrication and metrology development. Synchrotron radiation source, as a revolutionary light source, provides one of the most high-performance X-ray for scientific research, where reflect mirror plays an essential role in X-ray beam focusing. The short wavelength of X-ray demands reflecting photons only at a grazing angle of incidence on the extremely high-precision and smooth surface. Fabrication of such mirrors requires highly specialized equipment and technology that only a few foreign optic manufacturers possess, whereas manufacturers in China is laggard in this area. It is imperative to develop fabrication capability domestically as two synchrotron radiation facilities are under construction and several more projects are about to launch in the near future in China.
TL;DR: In this article, the development trend of large-size space mirrors was discussed from the angles of material and fabrication technology. And the 1.0 m aperture technical validation brazed mirror was performed environmental tests including thermal-vacuum test, vibration test and anti-radiation test.
Abstract: With the space technologies progress rapidly, demand of large-size mirrors is intensively growing. In this paper, the developing trend of large-size space mirrors was discussed from the angles of material and fabrication technology. Taking 1.0 m aperture technical validation brazed mirror as an example, the design and fabrication of segments, joining and optic machining were analyzed. In addition, the 1.0 m aperture technical validation brazed mirror was performed environmental tests including thermal-vacuum test, vibration test and anti-radiation test in order to evaluate its engineering applicability. The experimental results show that the surface figure of the 1.0 m aperture technical validation brazed mirror changed from 0.038λ (λ=632.8 nm) to 0.037λ and 0.036λ after thermo-vacuum test and vibration test. Additionally, reflectivity of the brazed mirror basically kept stable after 60Co γ-ray radiation test, indicating a brilliant application prospect.
TL;DR: In this paper, a structural optimization design of a lightweight rectangular reflective mirror of an off-axis three-reflection optical system is performed, where a lightweight structure based on the center support of SiC materials is proposed.
Abstract: In order to solve the problem that the mass and the surface figure accuracy of the space reflective mirror are often contradictory in the lightweight design process, a structural optimization design of a lightweight rectangular reflective mirror of an off-axis three-reflection optical system is performed. In this study, a lightweight structure based on the center support of SiC materials is proposed. At the same time, a multi-objective optimization method is introduced. With the RMS value and Mass as the optimization targets at the same time, a mirror optimal structure model is obtained with a mass of 2.32 kg. Compared with the solid mirror, the lightweight ratio is 73.8%. Then the mirror subassembly is designed and the integrated performance of it is simulated. It shows that the RMS value of the mirror reaches respectively 2.5 nm, 2.2 nm and 7.3 nm when gravity load is applied in the directions of X, Y and Z axes. Furthermore, the RMS value is 3.2 nm when the mirror subassembly is under the load condition of uniform temperature rise of 4 ℃, which is far less than the requirement of RMS≤λ/50(λ=632.8 nm). Therefore the data meets the design requirements.
TL;DR: The results show that the dual-frame decentralized fusion scan proposed in this paper can accurately adjust the luminance of microLED/OLED and improve the brightness of the image observed by human eyes.
Abstract: When the microLED is in the forward working direction, it is difficult to precisely adjust its voltage to obtain different brightness. Moreover, when the microLED/OLED is turned on, they will be in a closed state for a long time, causing the image display brightness to be deteriorated by the human eye. In order to solve these problems, this paper proposes a dual-frame decentralized fusion scanning strategy to achieve different brightness by adjusting the microLED/OLED on-time. Firstly, the method de-weights the data bits and inserts their on-times into the closed time. Then the data bit weights are double-frame fused after decentralization. Finally, the scanning order of the data bits is redefined. According to the proposed scanning strategy, we designed a scanning controller to drive digital on-silicon microdisplay. The results show that the dual-frame decentralized fusion scan proposed in this paper can accurately adjust the luminance of microLED/OLED and improve the brightness of the image observed by human eyes. Compared with other scanning strategies, the scanning strategy improves the scanning efficiency to 93.75%, the field frequency is increased to 2040 Hz, the scanning clock frequency is 102.36 MHz, and the scanning data bandwidth is reduced. The feasibility of the scan controller is proved by testing at last.
TL;DR: The dynamic test on the Boston head tracking database proves that the face detection algorithm can effectively solve the problem of rotation-invariant face detection, and the window jitter problem in the video is well solved.
Abstract: In the unconstrained open-space, face detection is still a challenging task due to the facial posture changes, complex background environment, and motion blur. The rotation-invariant algorithm based on cascaded network and pyramid optical flow is proposed. Firstly, the cascading progressive convolutional neural network is adopted to locate the face position and facial landmark of the previous frame in the video stream. Secondly, the independent facial landmark detection network is used to reposition the current frame, and the optical flow mapping displacement of the facial landmark between the two frames is calculated afterwards. Finally, the detected face is corrected by the mapping relationship between the optical flow displacement of the facial landmark and the bounding box, thereby completing the rotation-invariant face detection. The experiment was tested on the FDDB public datasets, which proved that the method is more accurate. Moreover, the dynamic test on the Boston head tracking database proves that the face detection algorithm can effectively solve the problem of rotation-invariant face detection. Compared with other detection algorithms, the detection speed of the proposed algorithm has a great advantage, and the window jitter problem in the video is well solved.
TL;DR: The application of the deformable mirror in the inertial confinement fusion (ICF) system of China is introduced and the typical multi-channel deformable Mirror technology and application results in the field of astronomical optical observation is also described.
Abstract: Deformable mirror is the core component of the adaptive optics system and the primary research object for the research of adaptive optics technology. In this review, the research history of adaptive optics technology, especially the deformable mirror technologies of IOE is reviewed and the early development of our deformable mirror technology is briefly described. The application of the deformable mirror in the inertial confinement fusion (ICF) system of China is introduced and the typical multi-channel deformable mirror technology and application results in the field of astronomical optical observation is also described. Then we introduce the application of compact deformable mirror in biomedical research. At last, some new research directions of deformable mirror technology are revealed.
TL;DR: In this paper, a computer aided adjustment method of two-step sensitivity matrix model was proposed to adjust the position of the secondary mirror of Cassegrain telescope with large field of view.
Abstract: In order to adjust the position of the secondary mirror of Cassegrain telescope with large field of view, a computer aided adjustment method of two-step sensitivity matrix model was proposed. Based on the analysis of the shortcomings of the traditional sensitivity matrix method of the two order model, a fine tuning step was added based on the characteristics of the sensitivity matrix and the traditional sensitivity matrix method was improved. For the Cassegrain system, the relationship between the Zernike coefficients and the misalignment was analyzed, and the calibration simulation of Cassegrain system with 300 mm aperture and 0.6° field of view was carried out. The simulation results show that after correction by traditional sensitivity matrix method, the mean values of offset along x, y, z axes and tilt around x, y axes are -0.0684 mm, -0.0892 mm, 0.0015 mm, 0.0498° and -0.0444°, respectively, and the full field wavefront aberration RMS is less than 0.1λ(λ=632.8 nm). After correction by two step sensitivity matrix correction method, the mean values are -0.0018 mm, -0.0012 mm, 0.0002 mm, 0.0008° and -0.0012°, respectively, and the full field wavefront aberration RMS is less than 0.03λ, which is obviously superior to the traditional sensitivity matrix method.
TL;DR: The experimental results show that the detection method in this paper can adaptively correct the image brightness, and the uneven brightness of the image is significantly improved.
Abstract: In view of the problem about uneven image acquisition and inaccurate edge extraction in pipeline detection process, a pipeline robot defect inspection method based on adaptive image enhancement is proposed. Firstly, a single-scale Retinex adaptive image enhancement algorithm is designed, which uses the guided filter to estimate the illumination component of the Value component of the image, and gets the illumination equilibrium image by adaptive Gamma correction, so as to realize the image enhancement. Then, the traditional Canny edge detection method is improved, using bilateral filtering to smooth the image. Besides, the defect images are segmented by the iterative threshold method, and the edge connection is carried out according to the edge pixel similarity. Therefore, the defect contour of the pipe-wall is extracted effectively. Thirdly, a pipeline robot defect detection system based on adaptive image enhancement is built, and a crawler car equipped with the pan-tilt-zoom camera conducts all-round visual inspection of the defects in the pipeline inner wall. The experimental results show that the detection method in this paper can adaptively correct the image brightness, and the uneven brightness of the image is significantly improved. Compared with the sub-optimal algorithm, the information entropy of the image is increased by 2.4%, the average gradient of the image is increased by 2.3%, and the peak signal to noise ratio is increased by 4.4%, and the pipeline defect edges are extracted effectively with the detection accuracy up to 97%.
TL;DR: It is confirmed that the FSO-OFDM system has a strong ability to resist multipath interference and frequency selective fading, as well as good bit error rate (BER) performance and has a very broad application prospect and using value.
Abstract: Based on the analysis of the two main problems of atmospheric channel in free space optics (FSO), aiming at the problem of laser atmospheric channel especially the problems of frequency selective fading and multipath effect in complex turbulent environment, the suppression method is proposed based on OFDM turbulence effect, the FSO-OFDM system is built, the baseband model of this system and the signal of multi-carrier modulation and demodulation method are studied. First of all, this article systematically analyzes the mechanism of turbulence effect of atmospheric channel, and discusses the model of plane wave laser communication system under the influence of atmospheric turbulence, the space optical communication system model of Gaussian beam of a logarithmic normal turbulent channel is established under the influence of atmospheric turbulence, the probability density function of light intensity is deduced, the methods for analyzing the effects of various atmospheric turbulence effects on system performance using the signal-to-noise ratio probability density function; the OFDM multi-carrier modulation scheme of FSO-OFDM system is designed, the baseband mode model of FSO-OFDM system is constructed, and the modulation and demodulation principle of its signal is studied using this model. Finally, FSO-OFDM system is realized by using MATLAB, and the FSO communication system under the multipath interference is simulated, experiments on bit error rate characteristics under different guard intervals are performed. It is confirmed that the FSO-OFDM system has a strong ability to resist multipath interference and frequency selective fading, as well as good bit error rate (BER) performance. It can effectively solve the problem of intersymbol interference and the reliable link, and has a very broad application prospect and using value.
TL;DR: The image sparse prior is applied to the restoration of single-frame atmospheric turbulence degraded images, showing that compared with total variation priori, sparse priori is better at kernel estimation, producing sharp edges and removal of ringing, etc., which reducing the kernel estimation error and improving restoration quality.
Abstract: Blind image deconvolution is one method of restoring both kernel and real sharp image only from degraded images, due to its illness, image priors are necessarily applied to constrain the solution. Given the fact that traditional image gradient l2 and l1 norm priors cannot describe the gradient distribution of natural images, in this paper, the image sparse prior is applied to the restoration of single-frame atmospheric turbulence degraded images. Kernel estimation is performed first, followed by non-blind restoration and the split Bregman algorithm is used to solve the non-convex cost function. Simulation results show that compared with total variation priori, sparse priori is better at kernel estimation, producing sharp edges and removal of ringing, etc., which reducing the kernel estimation error and improving restoration quality. Finally, the real turbulence-degraded images are restored.