Satellite-rocket docking ring recognition method based on mathematical morphology
Author(s):
Zhiqiang Xu;
Yang Shang;
Xuan Ma
Show Abstract
Satellite-rocket docking ring recognition method based on mathematical morphology is presented in this paper, according to the geometric and grayscale characteristics of the docking ring typical structure. The docking ring used in this paper is a circle with a cross in the middle. Most of spacecrafts are transported into orbit by rocket, and they retain the connection component with the rocket. The tracing spacecraft should capture the target spacecraft first before operating the target spacecraft. The docking ring is one of the typical parts of a spacecraft, and it can be recognized automatically. Thereby we can capture the spacecraft through the information of the docking ring. Firstly a multi-step mathematical morphology processing is applied to the image of the target spacecraft with different structure element, followed by edge detection and line detection, and finally docking ring typical structure is located in the image by relative geometry analysis. The images used in this paper are taken of real satellite in lab. The docking ring can be recognized when the distance between the two spacecraft is different. The results of physical simulation experiment show that the method in this paper can recognize docking ring typical structure accurately when the tracing spacecraft is approaching the target spacecraft.
Optimized design and research of secondary microprism for dense array concentrating photovoltaic module
Author(s):
Guanghui Yang;
Bingzhen Chen;
Youqiang Liu;
Limin Guo;
Shun Yao;
Zhiyong Wang
Show Abstract
As the critical component of concentrating photovoltaic module, secondary concentrators can be effective in increasing the acceptance angle and incident light, as well as improving the energy uniformity of focal spots. This paper presents a design of transmission-type secondary microprism for dense array concentrating photovoltaic module. The 3-D model of this design is established by Solidworks and important parameters such as inclination angle and component height are optimized using Zemax. According to the design and simulation results, several secondary microprisms with different parameters are fabricated and tested in combination with Fresnel lens and multi-junction solar cell. The sun-simulator IV test results show that the combination has the highest output power when secondary microprism height is 5mm and top facet side length is 7mm. Compared with the case without secondary microprism, the output power can improve 11% after the employment of secondary microprisms, indicating the indispensability of secondary microprisms in concentrating photovoltaic module.
Optical design of temperature self-adaptive dual-field infrared system
Author(s):
Ming LI;
Li-juan Hong;
Min Jin;
Teng-peng Zhang
Show Abstract
Based on the theory of athermalization, an optical system of temperature self-adaptive dual field of view was designed in this paper, appling in 3μm~5μm medium wave infrared camera system. This system achieved the design of optical passive athermalization by reasonable selection in terms of infrared optical materials and aspheric surface. Only five lenses were applied in this optical system, meanwhile, optical materials like germanium, silicon and ZnSe were all ordinary and cost-effective. The focal distance was 50mm/100mm, with total length of 125mm and pixel size of 17μm. The MTF of the two field of view were both greater than 0.5 at 30lp/mm in -45°C~+60°C, with its optical performance approximating the diffraction limit.
A videometrics method of cooperative object pose-measurement
Author(s):
Yueqiang Zhang;
Yang Shang;
Jianliang Ou;
Xuan Ma
Show Abstract
A systematic videometrics method of cooperative object pose-measurement for RVD (rendezvous and docking) is proposed in the paper. According to the method, initial values of pose parameters are calculated from binocular images respectively, and then optimized with bundle adjustment. While a certain variation of some exterior parameters of one camera are added as systematic disturbance purposely, the correct result could be calculated theoretically as the method analysis, and then also is verified in our experiment. The correct result could be converged quickly and stably in the experiment, and accurate pose-measurement results also could be obtained while initial values are provided with some certain errors. Even some amount of disturbance has been added purposely in experiment, high-precision pose results are also obtained by the binocular and bundle adjustment way.
Research on auto-calibration technology of the image plane's center of 360-degree and all round looking camera
Author(s):
Shaojun Zhang;
Xiping Xu
Show Abstract
The 360-degree and all round looking camera, as its characteristics of suitable for automatic analysis and judgment on the ambient environment of the carrier by image recognition algorithm, is usually applied to opto-electronic radar of robots and smart cars. In order to ensure the stability and consistency of image processing results of mass production, it is necessary to make sure the centers of image planes of different cameras are coincident, which requires to calibrate the position of the image plane’s center. The traditional mechanical calibration method and electronic adjusting mode of inputting the offsets manually, both exist the problem of relying on human eyes, inefficiency and large range of error distribution. In this paper, an approach of auto- calibration of the image plane of this camera is presented. The imaging of the 360-degree and all round looking camera is a ring-shaped image consisting of two concentric circles, the center of the image is a smaller circle and the outside is a bigger circle. The realization of the technology is just to exploit the above characteristics. Recognizing the two circles through HOUGH TRANSFORM algorithm and calculating the center position, we can get the accurate center of image, that the deviation of the central location of the optic axis and image sensor. The program will set up the image sensor chip through I2C bus automatically, we can adjusting the center of the image plane automatically and accurately. The technique has been applied to practice, promotes productivity and guarantees the consistent quality of products.
Infrared zoom lens design based on target correlation recognition and tracking
Author(s):
Su Zhang;
Jin Duan;
Qiang Fu;
Wen-sheng Wang
Show Abstract
To expand the infrared (IR) target detection scope of tank, according to the requirements of real-time recognition and tracking for target with joint transform correlator (JTC) a set of infrared (IR) continuous zoom optical system with 8-12 μm long-wave-band was designed, which applied long-wave 384× 288 element uncooled thermal IR focal plane array detector. In this system, the zoom ratio is 8× , the range of the focal length is 30mm-240mm, F number is 2 and during the zoom process the relative aperture is invariant. This system used the mechanical compensation method, after designed and optimized, it can be composed of 6 spherical lenses with Ge and ZnS only. The design results show that when the cutoff frequency is 14lp/mm, in the whole range of the focal length the MTF curves are all above 0.52 which all approach to the diffraction limit curves. And the spot size is smaller than the pixel size of the receiver. It can meet the requirement of long IR target recognition and tracking in the practical application.
Starlight emergence angle error analysis of star simulator
Author(s):
Jian Zhang;
Guo-yu Zhang
Show Abstract
With continuous development of the key technologies of star sensor, the precision of star simulator have been to be further improved, for it directly affects the accuracy of star sensor laboratory calibration. For improving the accuracy level of the star simulator, a theoretical accuracy analysis model need to be proposed. According the ideal imaging model of star simulator, the theoretical accuracy analysis model can be established. Based on theoretically analyzing the theoretical accuracy analysis model we can get that the starlight emergent angle deviation is primarily affected by star position deviation, main point position deviation, focal length deviation, distortion deviation and object plane tilt deviation. Based on the above affecting factors, a comprehensive deviation model can be established. According to the model, the formula of each factors deviation model separately and the comprehensive deviation model can be summarized and concluded out. By analyzing the properties of each factors deviation model and the comprehensive deviation model formula, concluding the characteristics of each factors respectively and the weight relationship among them. According the result of analysis of the comprehensive deviation model, a reasonable designing indexes can be given by considering the star simulator optical system requirements and the precision of machining and adjustment. So, starlight emergence angle error analysis of star simulator is very significant to guide the direction of determining and demonstrating the index of star simulator, analyzing and compensating the error of star simulator for improving the accuracy of star simulator and establishing a theoretical basis for further improving the starlight angle precision of the star simulator can effectively solve the problem.
The measurement of pointing accuracy of two-dimensional scan mirror
Author(s):
Hui Xing;
Chao An;
Junru Song;
Xuhua He
Show Abstract
The observation accuracy of space camera targeted on ground objects is directly affected by the pointing deviation of the two dimensional scan mirror. A plane model of the scan mirror’s normal trajectory is established when scan mirror is rotating along the rolling axis while the pitching axis remains still. The pointing accuracy of scan mirror cross the track direction is measured with the plane model. A cone model of the scan mirror’s normal trajectory is established when scan mirror is rotating along the pitching axis while the rolling axis remains still. The pointing accuracy of scan mirror along the track direction is measured with the plane model. The nonorthogonality of shafting of the rolling axis and the pitching axis is measured with the two models. Data processing results are feedback to pointing controller to correct the input signal of resolver, until the pointing accuracy of scan mirror meets the requirement. The experimental results indicate that the models of measuring the pointing accuracy of scan mirror are accurate and the data processing algorithm is feasible. The testing precision reached 10-3 second.
Magnetically tunable multi-way splitters based on unidirectional properties of magnetic metamaterials
Author(s):
Wenyao Liang;
Yuxia Zhang;
Wuhe Chen;
Huangzhong Yu
Show Abstract
We theoretically study the properties of unidirectional edge modes in a magnetic metamaterial waveguide and their applications in tunable multi-way splitters. These edge modes can only be excited at the surface to propagate along a single direction with nearly perfect transmittance of 100%. The physical origin is attributed to the combined action of magnetic resonance and time-reversal symmetry breaking under external magnetic fields. Moreover, the propagation direction can be controlled by reversing the direction of the external magnetic field. Further study reveals that a perfect electric conductor defect scarcely affects the transmittance but has sensitive influence on the phase delay and pattern distribution of the unidirectional edge modes. These properties hold promise for designing various unidirectional photonic devices. As an example, we design a tunable multi-way splitter with the advantages of high transmission contrast and convenient pathway control simultaneously.
Sensor fault diagnosis for fast steering mirror system based on Kalman filter
Author(s):
Hongju Wang;
Qiliang Bao;
Haifeng Yang;
Sunjie Tao
Show Abstract
In this paper, to improve the reliability of a two-axis fast steering mirror system with minimum hardware consumption, a fault diagnosis method based on Kalman filter was developed. The dynamics model of the two-axis FSM was established firstly, and then the state-space form of the FSM was adopted. A bank of Kalman filters for fault detection was designed based on the state-space form. The effects of the sensor faults on the innovation sequence were investigated, and a decision approach called weighted sum-squared residual (WSSR) was adopted to isolate the sensor faults. Sensor faults could be detected and isolated when the decision statistics changed. Experimental studies on a prototype system show that the faulty sensor can be isolated timely and accurately. Meanwhile, the mathematical model of FSM system was used to design fault diagnosis scheme in the proposed method, thus the consumption of the hardware and space is decreased.
Spectral calibration of programmable imaging spectrometer
Author(s):
Guojun Du;
Zhibo Liao;
Wenchun Jiao;
Xiaoying Zong;
Xuhua He;
Haichao Wang
Show Abstract
Programmable imager spectrometer can provide flexible data by changing the spectrum section number, central wavelength, spectral width and spatial resolution in orbit. Spectral calibration of imaging spectrometer plays an important role for acquiring accurate spectrum, two spectral calibration types are in essence: wavelength calibration and Full-width-half-maximum (FWHM). Base on the character of programmable imager spectrometer, designed a set of spectral calibration system. Wavelength calibration realized by utilizing the Monochromatic light of high precision monochromator, during the test, changed output parameters of monochromator according to the spectral bandwidth of imager spectrometer. The FWHM is constructed by a set of variable narrow spectrum lines that is output by tunable laser. Gaussian fitting algorithm is used to determine center wavelength and the FWHM of the characteristic spectrum line, Spectral pixels are calibrated by quadratic polynomial, standard spectroscopic lamp is used to verify wavelength calibration result accuracy. The calibration result indicates that FWHM is better than 2nm, the wavelength uncertainty is less than 0.6nm, meet the calibration requirements of programmable imaging spectrometer.
Optical design of MWIR detection system for near-space infrared detecting
Author(s):
Pei-pei Yan;
Kai Liu;
Gang Li;
Qiusha Shan;
Jing Duan;
Kai Jiang
Show Abstract
Near-space platform has a high signal contrast and a long detection time. In order to realize effective detection of low altitude penetration target, a middle wave infrared (MWIR) optical system used in near space detection with high optical performance is given. First, the optical system scheme was described. Then on the basis of instrument and system consideration, the optical design parameters were distributed reasonably. The system had an effective focal length of 600 mm, an F-Number of F/4, a field of view of 2ω=1.16°, spatial resolution of 18 lp/mm and a working wavelength range of 3~5μm. The system structure is simple. And the requirements of the spot, energy concentration, distortion are all satisfied. Because the change of environment temperature will deeply influence image quality of MWIR optical system, the temperature characteristic of the system is analyzed. Moreover, first -order ghost and narcissus effect of the system are all analyzed in CODEV software. The analysis results show that temperature, first-order ghost and narcissus effect requests are all satisfied.
Open loop liquid crystal adaptive optics systems: progresses and results
Author(s):
Zhao-liang Cao;
Quan-quan Mu;
Huan-yu Xu;
Pei-guang Zhang;
Li-shuang Yao;
Li Xuan
Show Abstract
Liquid crystal wavefront corrector (LCWFC) is one of the most attractive wavefront correction devices for adaptive optics system. The main disadvantages for conventional nematic LCWFC are polarization dependence and narrow working waveband. In this paper, a polarized beam splitter (PBS) based open loop optical design and an optimized energy splitting method was used to overcome these problems respectively. The results indicate that the open loop configuration was suitable for LCWFC and the novel energy splitting method can significantly improve the detection capability of the liquid crystal adaptive optics system.
Design of the relay lens for infrared system coupled with imaging fiber bundle
Author(s):
Xingtao Yan;
Fu Li;
Jianfeng Yang;
Bin Xue;
Xiaolong Ma;
Juan Lv;
Yinghong He;
Yiyi Zhao
Show Abstract
Relay lens is an important element for infrared system coupled with imaging fiber bundle. According to the basic composition and structural characteristics of infrared system coupled with imaging fiber bundle, this paper put forward the general principle and method of its relay lens design, then a material relay lens has been designed by ZEMAX with definite performance index. It has a working spectral coverage from 3.7μm to 4.8μm, focal length of 33.5mm, magnification of -0.6, linear field of view of 12mm, objective numerical aperture of 0.15. It is objective telecentric and is adapted to the relay of infrared detector and imaging fiber bundle. The total lens has two aspheric surfaces and only four pieces of singlet. Its MTF value is 0.7@17 lp/mm, and distortion is -0.19%. After necessary tolerance analysis and structural design, this relay lens has been fabricated. The optical performances fulfill the design requirements and clear images have been got by this lens. These prove the validity and rationality of the design method. It gives a foundational guidance for such relay lens design.
Analysis of the imaging performance of panoramic annular lens with conic conformal dome
Author(s):
Xiao Huang;
Jian Bai
Show Abstract
Panoramic annular lens (PAL) is a kind of the specific wide angle lenses which is widely applied in panoramic imaging especially in aerospace field. As we known, to improve the aerodynamic performance of the aircraft, conformal dome, which notably reduces the drag of an aircraft, is also functioning as an optical window for the inbuilt optical system. However, there is still no report of the specific analysis of the imaging performance of PAL with conformal dome, which is imperative in its aerospace-related applications. In this paper, we propose an analysis of the imaging performance of a certain PAL with various conic conformal domes. Working in visible wavelength, the PAL in our work observes 360° surroundings with a large field of view (FOV) ranging from 30° ~105° . Meanwhile, various thicknesses, half-vertex angles, materials of the conic dome and the central distances between the dome and PAL are considered. The imaging performances, mainly indicated by modulation transfer function (MTF) as well as RMS radius of the spot diagram, are systematically compared. It is proved that, on the contrary to the general cases, the dome partly contributes to the imaging performance of the inbuilt PAL. In particular, with a conic conformal dome in material of K9 glass with a half-vertex angle of 25° and a thickness of 6mm, the maximum MTF at 100lp/mm could be improved by 6.68% with nearly no degeneration of the minimum MTF, and the RMS radius could be improved by 14.76% to 19.46% in different FOV. It is worth to note that the PAL is adaptive to panoramic aerospace applications with conic or quasi-conic conformal dome and the co-design of both PAL and the dome is very important.
The research of calibration method on lens-tilt displacement transmission-type system based on the aberration bounded model
Author(s):
Chun-mei Xu;
Bing-qi Liu;
Li Li;
Fu-yu Huang;
Chu Zhang
Show Abstract
As the developing appliance range of high-resolution optical design, the requirement on the aberration of system design is becoming higher and higher, but the installation and adjustment error of optical components is an important element which influences the aberration. The decentration and tilt of optical components result not only the image lateral displacement but also the aberration enlargement of the optical system, the research on image quality of plane symmetric optical system is becoming more and more popular. The Gaussian correction methods on lens decentration already exist, but it is short of theoretical research to guide the correction on the lens tilt, which leads to the effect of image lateral displacement. This thesis analyzes theoretically a mathematical model between the lens tilt degree and wave aberration, and deduces mathematically the correction equation of zero aberration increment under the aberration constraint condition. Taking an example of some type optical sight, the ZEMAX simulation is carried out to validate this method, and the results show that: This method can effectively guide the correction of lens tilt, and reduce the influence of lens position change on the optical imaging quality. It has important practical significance to guide high-resolution optical design.
Research on surface control technology of precession bonnet polishing for optical processing
Author(s):
Li-peng Zhang;
Hui Yang;
Long-xiang Bao;
Jing Li
Show Abstract
The key technology in precession bonnet polishing was investigated to get the high-precision optical surface. First, the facility and principium of bonnet polishing was introduced and the removal function of bonnet polishing was acquired from the analysis of Preston equation and the orthogonal processing experiments. Then a new algorithm based on matrix iteration to solve the dwell time was proposed and the dwell time function was analyzed to make it convenient to the polishing. The simulation of the variance of the residual error was made through MATLAB to prove the algorithm. And the simulation result showed that the residual error can reach up to 0.1μm. Finally, the polishing experiments of plane and sphere were made to validate the accuracy of the dwell time algorithm and the practicability and precision of the precession bonnet polishing. After polishing the sphere surface PV value reached to 0.17μm. Through this the rationality of the dwell time algorithm was proved and it can satisfy the requirement of optical precision machining very well. And this also provided theoretic foundation for the later polishing for free-form surface.
Polarization-difference imaging of objects in smoke environment
Author(s):
Lu Liu;
Binkang Li;
Shaohua Yang;
Mingan Guo;
Ming Yan;
Tongding Luo;
Gang Li;
Shuai Gao
Show Abstract
Target detection in smoke environment using laser active imaging is of great research significance. According to the characteristics of light propagating in smoke environment, the method of laser transmission imaging is adopted and polarization-difference (PD) imaging technology is used to suppress the effect of scattering light on imaging quality. PD imaging method needs to record two target images of different polarization directions and then the two images are subtracted. A correction factor α is used to match the scattering light intensity of the two images, so scattering light can be mostly filtered out. Experiments show that the quality of images obtained by PD imaging method is better than intensity ones. The PD images have big noisy when smoke concentration is high. A method which combines median filtering with multi-scale morphological edge detection is proposed to process images. It can suppress image noise, improve image contrast and edge sharpness effectively.
Design of laser beam expander in underwater high-repetition-rate range-gated imaging system
Author(s):
Wei Zhong;
Xiaohui Zhang
Show Abstract
Active underwater imaging systems, using an artificial light source for underwater target illumination, have preferable practical value in military and civil domain. Back-scattering of water impacts imaging system performance by reducing image contrast, and this is especially bad when the light source is close to the camera. Range-gated technique can effectively rejecting the back-scattering of water and improve the range of underwater target detection, while it can only collect image at certain distance for every laser impulse. High-repetition-rate green laser is a better light source in underwater range-gated imaging system. It has smaller pulse energy, while it can improve the imaging result. In order to illuminate the proper area underwater according to the different distance between the laser source and targets, there must be a magnifying-ratio variable beam expander to adjust the divergent angle of the laser. Challenges associated with magnifying-ratio computation and designing of beam expander are difficult to overcome due to the obvious refraction and forward-scattering of water.
An efficiency computing method is presented to obtain the magnifying-ratio of beam expander. The illuminating area of laser beam can be computed according to the refraction index and beam spread function (BSF) which has already considered forward-scattering process. The magnifying-ratio range of beam expander should be 0.925~3.09 in order to obtain about φ1m illuminating area when the distance between laser and target is 10~40m. A magnifying-ratio variable beam expander is designed according to computation. Underwater experiments show that this beam expander plays an effective role on illuminating in underwater high-repetition-rate range-rated Imaging system.
Research on the space-variant image sensor based on optical method
Author(s):
Yufei Zhao;
Yong Song;
Lin Li;
Qun Hao;
Shaochun Han;
Wansong Li;
Shangnan Zhao
Show Abstract
A novel space-variant image sensor based on optical method is proposed. Firstly, the mathematical models of the proposed image sensor and its non-uniform lens array are developed and verified. Secondly, the relationships among the parameters of the non-uniform lens have been simulated and discussed. Thirdly, experiments are carried out for verifying the characteristic of rotation and scaling invariance of the proposed image sensor. Finally, some conclusions are deduced, which will help to result in a space-variant image sensor with the characteristics of high sensitivity, high speed and big planar array, etc.
Research on precision windowed track mode for in-orbit calibration on star tracker
Author(s):
Jun Zhang;
Yun-cai Hao;
Li Wang
Show Abstract
Implementation of an in-orbit calibration is an effective approach to reduce position error of individual star spot down to arcsec on star tracker. However, without knowledge of variance errors of some error sources, the reduction of such errors to what extent is unclear leading to in-orbit correction inefficiency. Based on Cramer Rao Lower Bound(CRLB) theory, we obtain the minimum variance error of position and make an accurate definition of precision windowed track mode for in-orbit calibration. After that, the error constraints on proper motion, velocity aberration, drift in focal length and other factors are studied in details. Imposing proper restrictions on those parameters, in-orbit correction of star tracker could approach CRLB accuracy.
Design of collimating and rearrangement systems of laser diode array beam
Author(s):
Runmei Gao;
Tao Fang;
Rulian Fu;
Jianquan Yao
Show Abstract
To improve the laser diode output beam quality, micro-cylindrical lens and the step-type lens combination are designed. The former is used to collimate beam in fast-axis direction, while the latter plays a role in the slow-axis of splitting and the rearrangement. The micro-column semi-elliptical lens is made with the drops of spherical zoom lensin electric field and with the help of the material properties of light-cured production, which can reduce the reflection of the front surface and total reflection loss of the after. The divergence angle in the fast axis is compressed to roughly the same as that in the slow-axis direction; Stepped lens splits compressed long strip beam in the slow axis, with parallelogram style of level equidistant and rearrange in the fast axis direction. The spot in the slow axis gets smaller and the spot becomes larger in the fast axis. At last divergence angle and the beam spot achieve balanced in the fast axis and slow axis, optical parameters BPP integrates approximate the same, and beam quality can be improved.
Research on non-direct reflection columnar microstructure
Author(s):
B. Q. Wu;
X. Z. Wang;
L. H. Dong
Show Abstract
To minimize the risk of laser accidents, especially those involving eye and skin injuries, it is crucial to pay more attention to laser safety. To control the risk of injury, depending on the laser power and wavelength, a number of required safety measures have been put forward, such as specific protection walls, and wearing safety goggles when operating lasers. The direct reflection columnar microstructure can also be used for laser safety. Based on mathematical foundations , a columnar microstructure is designed by the optical design software LightTools. Simulation showed that there is a tilt angle between the emergent and incident light, the incident light being perpendicular to the microstructure, as well as the phenomenon of no direct reflection happened. A novel testing platform was built for the columnar microstructure after it was machined. The applied testing method can measure the angle between the emergent and incident light. The method lays the condition for the further research. It is shown that the columnar microstructure with no direct reflection can be utilized in laser protection systems.
Design and fabrication of an elliptical micro-lens array with grating for laser safety
Author(s):
L. H. Li;
B. Q. Wu;
C. Y. Chan;
W. B. Lee;
L. H. Dong
Show Abstract
With the enormous expansion of laser usage in medicine, industry and research, all facilities must formulate and adhere to specific safety methods that appropriately address user protection. The protective ellipticalal microstructure with grating is a novel technology which can provide the principal means of ensuring against ocular injury, and must be worn at all times during laser operation. On the basis of Fresnel's law and the diffractive law, Solidworks and Lighttools software are applied to design the elliptical micro-lens array and correspondent grating. The height of the microstructure is 100um and its period is 3mm. The period of grating is 5um. It is shown that the amount of emergent light of a specific wavelength (1064nm) can reflect more than 40° from the incident light through simulation, while the incident light is perpendicular to the microstructure. The fabrication adopts the ultra-precision single point diamond method and injection molding method. However, it is found in the test that the surface roughness has a serious effect on the angle between the emergent and incident light. As a result, the element can reflect the vertical incidence beam into a tilted emergent beam with a certain angular degree , as well as protecting users from laser damage injures.
The application of frequency characteristics test in fast control mirror system
Author(s):
Xun Gan;
Yu Jang;
Zong You Wang;
Yao Mao
Show Abstract
The control bandwidth of the FSM affects directly on the performance of the tracking system based on the compound axis servo structure. The FSM’s control system’s accuracy affects the bandwidth and the tracking precision of the system directly. Obtaining the accurate transfer function of the control object is the basis of designing frequency characteristics based control system. Measurement of high precision transfer function is needed to compensate the influence of the mechanical resonance. The mechanical resonance of fast control mirror is mainly of high frequency. In this case, the measured signal’s SNR is low so that the measurement accuracy of the frequency characteristic is reduced accordingly. One way to get frequency characteristics is to input sweeping sine drive signal to the system, measure the output of system, and then calculate the frequency characteristics by Fourier Transformation. However, the measuring result of the FSM system that has a low SNR in high frequency is not precise enough as in a system with a high SNR. To solve the problem mentioned above, this article presents a method to calculate frequency characteristics of an FSM system. This method uses the least squares to fit the fast mirror output overall waveform and the input source can be sine, white noise, multimode signal or chirp signal. A digital compensator based on this method is introduced to experimentally verify the efficiency of the method. Experiment results show that fitting the system’s output curve in high frequency can effectively eliminate influence of quantization noise, gauss measurement noise and harmonic interference on the measurement accuracy and thus enhance the measuring signal’s SNR. It is proved that by using this method a more accurate frequency characteristics of the FSM can be obtained.
Analysis and judgment of key issues in data process for optical tracking and measurement
Author(s):
Shuhua Cui;
Si Shen;
Yuanyuan Kang;
Shaolin Hu
Show Abstract
Regarding the application value of optically tracked and controlled data in unspecified arc segment, the means from random error characteristic, comparison of nominal parameters, influence of error propagation to measurement and control station distribution analysis have been presented to carry out comprehensive analysis of the measured data in an all-around way to understand the availability of optically tracked data unspecified by practical verification and application in engineering, which is used as an effective evidence for external ballistic data process and make ballistic parameter more precise and reliable as a result of redundant data.
Novel PbS detector chip pattern with extinction function
Author(s):
Fengjin Chen;
Junjie Si;
Xianjun Su;
Yanqiu Lv;
Zhengfeng Shi
Show Abstract
A novel chip pattern with extinction function in Lead salt detectors is specified. Lead Sulfide (PbS) polycrystalline film is prepared by Chemical Bath Deposition (CMD) on a transparent substrate, then a special figure and structure is saved by lithography techonology on the substrate. As a quaternion detector chip that made by PbS thin film for example in this paper, whose performance including signal, noise, weak-peaks and the uniformity of the chip are too poor to meet the detecting system at the initial stage of research, and the qualified ratio of chips is only 3% .This paper explains the reason why the performance and qualified ratio of chips were so poor, focuses on a novel chip pattern with extinction which avoided the disadvantages of traditional one. the novel chip pattern has been applied in detectors. The novel chip pattern is prepared with PbS thin film which both “extinction slice” and detector chip are based on a same substrate , which not only had absorbed the jumbled light , improved the uniformity and other performance of photosensitive elements, but also had left out the assembly diffculty and precision demand when a extinction slice assembly in the restricted space of inswept detector chip, omitted the production process of extinction slice and shorten the assembly process of the detectors, and the qualified ratio of chips had been improved from 3% to 98%.
Application of independent component analysis in target trajectory prediction based on moving platform
Author(s):
Chao Deng;
Yao Mao;
Xun Gan;
Jing Tian
Show Abstract
In Electro-Optical tracking systems, compound control is used to keep high-precision tracking of fast targets by predicting the trajectory of the target. Traditional ground based Electro-Optical tracking system uses encoder data and target missing quantity read from image sensors to achieve the target trajectory by using prediction filtering techniques. Compared with the traditional ground based systems, relative angle between the tracking system and the ground cannot be read directly from encoder data in an Electro -Optical tracking system based on moving platform. Thus the combination of inertial sensors’ data and target missing quantity is required to composite the trajectory of targets. However, the output of the inertial sensors contains not only the information of the target's motion, but also the residual error of vibration suppression. The existence of vibration suppression residual error affects the trajectory prediction accuracy, thereby reducing compensation precision and the stability of the compound control system. Independent component analysis (ICA) method that can effectively separate the source signals from the measurement signals is introduced to target trajectory prediction field in this paper. An experimental system based on the method is built by settling a small dual-axis disturbance platform, which is taken as the stable platform, on a large dual-axis disturbance platform, which is used to simulate the motion of the moving platform. The result shows that the vibration residual is separated and subtracted from the combined motion data. The target motion is therefore obtained and the feasibility of the method is proved .
The effect of physical parameters of inertial stabilization platform on disturbance rejection ability and its improvement method
Author(s):
Yao Mao;
Chao Deng;
Xun Gan;
Jing Tian
Show Abstract
The development of space optical communication requires arcsecond precision or even higher precision of the tracking performance of ATP(Acquisition, Tracking and Pointing) system under the condition of base disturbance. ATP system supported by stabilized reference beam which is provided by inertial stabilization platform with high precision and high bandwidth, can effectively restrain the influence of base angular disturbance on the line of sight.
To get better disturbance rejection ability, this paper analyzes the influence of transfer characteristics and physical parameters of stabilization platform on disturbance stabilization performance, the result shows that the stabilization characteristics of inertial stabilization platform equals to the product of rejection characteristics of control loop and disturbance transfer characteristics of the platform, and improving isolation characteristics of the platform or extending control bandwidth can both achieve the result of getting a better rejection ability.
Limited by factors such as mechanical characteristics of stabilization platform, bandwidth/noise of the sensor, and so on, as the control bandwidth of the LOS stabilization platform is limited, and high frequency disturbance can not be effectively rejected, so the rejection of high frequency disturbance mainly depends on the isolation characteristics of the platform itself.
This paper puts forward three methods of improving the isolation characteristics of the platform itself, which includes 1) changing mechanical structure, such as reducing elastic coefficient, increasing moment of inertia of the platform, and so on; 2) changing electrical structure of the platform, such as increasing resistance, adding current loop, and so on; 3)adding a passive vibration isolator between the inertial stabilization platform and the base. The result of the experiment shows that adding current loop or adding a passive vibration isolator can effectively reject high frequency disturbance.
An application of PECHAN prism in infrared search and track system
Author(s):
Hua Qiang;
Yuan Li;
Shan Gao;
Yulan He;
Nanxi Wang;
Ling Wang;
Li Liu;
Hong Yang
Show Abstract
To solve real-time image de-rotation problems in infrared search and track (IRST) system design, the paper by adding a set of PECHAN Prism in infrared search and track system achieves image de-rotation. In order to get the image de-rotation prism corresponding with the actual engineering needs, it analyzes the main influential factor of prism and designs a 3~5μm MWIR image de-rotation prism. In order to ensure the performance of the optical system, it uses a new PECHAN Prism parallelism error detection method, which measured that the incident parallelism error is 1′16″. The parallelism error after alignment meets the system requirement. In this paper, the PECHAN Prism image de-rotation method significantly reduces the system’s optical path length to 170.5mm. This method will play an important role in miniaturization, light weight and engineering of product.
Thermal/structural/optical integrated design for optical window of a high-speed aerial optical camera
Author(s):
Gaopeng Zhang;
Hongtao Yang;
Chao Mei;
Kui Shi;
Dengshan Wu;
Mingrui Qiao
Show Abstract
In order to obtain high quality image of the aero optical remote sensor, it is important to analysis its thermal-optical performance on the condition of high speed and high altitude. Especially for the key imaging assembly, such as optical window, the temperature variation and temperature gradient can result in defocus and aberrations in optical system, which will lead to the poor quality image. In order to improve the optical performance of a high speed aerial camera optical window, the thermal/structural/optical integrated design method is developed. Firstly, the flight environment of optical window is analyzed. Based on the theory of aerodynamics and heat transfer, the convection heat transfer coefficient is calculated. The temperature distributing of optical window is simulated by the finite element analysis software. The maximum difference in temperature of the inside and outside of optical window is obtained. Then the deformation of optical window under the boundary condition of the maximum difference in temperature is calculated. The optical window surface deformation is fitted in Zernike polynomial as the interface, the calculated Zernike fitting coefficients is brought in and analyzed by CodeV Optical Software. At last, the transfer function diagrams of the optical system on temperature field are comparatively analyzed. By comparing and analyzing the result, it can be obtained that the optical path difference caused by thermal deformation of the optical window is 149.6 nm, which is under PV ≤1 4λ .The simulation result meets the requirements of optical design very well. The above study can be used as an important reference for other optical window designs.
Lens customization method to minimize aberration in integral imaging
Author(s):
Matheus Miranda;
Jonghyun Kim;
Keehoon Hong;
Byoungho Lee
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Conventionally the elemental lenses of the lens-array used in integral imaging have spherical surface profiles, thus they suffer from intrinsic lens aberrations such as spherical aberration and astigmatism. Aberrations affect the ability of the lens to focus light in a single point, or to collimate light from a point source. In integral imaging, this results in a loss of image quality of the reconstructed image due to distortions. The viewing characteristics of the integral imaging system, such as viewing angle and image resolution, are also affected by aberrations. We propose the use of a custom made aspherical lens-array which was specifically designed to minimize distortions due to aberrations and hence improve the reconstructed image quality. Ray optics calculations are used in order to analyze the aberrations and find the initial lens surface profile. Lens optimization is performed with the aid of numerical simulation software. The designed lens-array is compared to a conventional spherical lens-array of same properties. The design, optimization, and fabrication processes are described and the experiments are presented and compared with the computer simulations.
Optical system design of dual-spectrum autocollimator
Author(s):
Yongjing Wei;
Yiming Wu;
Maosen Xiao;
Weiguo Lu
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The optical system design of a new dual-spectrum autocollimator which can measure two different spatial azimuths simultaneously is proposed. According to the principle of dual-spectrum autocollimator, ZEMAX software is used to design and optimize the optical system. Since two light sources with different wavelength are used in the autocollimator, chromatic aberration is required to reduce off in the optical system design. The experimental results demonstrate that the measuring range of the dual-spectrum autocollimator is up to ±30', the deviation is less than 1″, and the resolution can reach 0.1". The designed autocollimator can simultaneously measure two different azimuths fastly and accurately.
Design of infrared diffractive telescope imaging optical systems
Author(s):
ZhouFeng Zhang;
BingLiang Hu;
QinYe Yin;
YongJun Xie;
FuZeng Kang;
YanJun Wang
Show Abstract
Diffractive telescope is an updated imaging technology, it differs from conventional refractive and reflective imaging system, which is based on the principle of diffraction image. It has great potential for developing the larger aperture and lightweight telescope. However, one of the great challenges of design this optical system is that the diffractive optical element focuses on different wavelengths of light at different point in space, thereby distorting the color characteristics of image. In this paper, we designs a long-wavelength infrared diffractive telescope imaging system with flat surface Fresnel lens and cancels the infrared optical system chromatic aberration by another flat surface Fresnel lens, achieving broadband light(from 8μm-12μm) to a common focus with 4.6° field of view. At last, the diffuse spot size and MTF function provide diffractive-limited performance.
The study of laser beam riding guided system based on 980nm diode laser
Author(s):
Zhou Qu;
Haifeng Xu;
Xin Sui;
Kun Yang
Show Abstract
With the development of science and technology, precision-strike weapons has been considered to be important for winning victory in military field. Laser guidance is a major method to execute precision-strike in modern warfare. At present, the problems of primary stage of Laser guidance has been solved with endeavors of countries. Several technical aspects of laser-beam riding guided system have been mature, such as atmosphere penetration of laser beam, clutter inhibition on ground, laser irradiator, encoding and decoding of laser beam. Further, laser beam quality, equal output power and atmospheric transmission properties are qualified for warfare situation. Riding guidance instrument is a crucial element of Laser-beam riding guided system, and is also a vital element of airborne, vehicle-mounted and individual weapon. The optical system mainly consist of sighting module and laser-beam guided module. Photoelectric detector is the most important sensing device of seeker, and also the key to acquire the coordinate information of target space. Currently, in consideration of the 1.06 u m of wavelength applied in all the semi-active laser guided weapons systems, lithium drifting silicon photodiode which is sensitive to 1.06 u m of wavelength is used in photoelectric detector. Compared to Solid and gas laser, diode laser has many merits such as small volume, simple construction, light weight, long life, low lost and easy modulation. This article introduced the composition and operating principle of Laser-beam riding guided system based on 980 nm diode laser, and made a analysis of key technology; for instance, laser irradiator, modulating disk of component, laser zooming system. Through the use of laser diode, Laser-beam riding guided system is likely to have smaller shape and very light.
Research on large spatial coordinate automatic measuring system based on multilateral method
Author(s):
Dongjing Miao;
Jianshuan Li;
Lianfu Li;
Yuanlin Jiang;
Yao Kang;
Mingzhao He;
Xiangrui Deng
Show Abstract
To measure the spatial coordinate accurately and efficiently in large size range, a manipulator automatic measurement system which based on multilateral method is developed. This system is divided into two parts: The coordinate measurement subsystem is consists of four laser tracers, and the trajectory generation subsystem is composed by a manipulator and a rail. To ensure that there is no laser beam break during the measurement process, an optimization function is constructed by using the vectors between the laser tracers measuring center and the cat's eye reflector measuring center, then an orientation automatically adjust algorithm for the reflector is proposed, with this algorithm, the laser tracers are always been able to track the reflector during the entire measurement process. Finally, the proposed algorithm is validated by taking the calibration of laser tracker for instance: the actual experiment is conducted in 5m × 3m × 3.2m range, the algorithm is used to plan the orientations of the reflector corresponding to the given 24 points automatically. After improving orientations of some minority points with adverse angles, the final results are used to control the manipulator's motion. During the actual movement, there are no beam break occurs. The result shows that the proposed algorithm help the developed system to measure the spatial coordinates over a large range with efficiency.
Feasibility analysis of digital single lens reflex applied in the field of aerospace measurement
Author(s):
Xinghao Feng;
Manliang Li;
Xuehai Tang
Show Abstract
The mainstrean digital single lens reflex (DSLR) image has the characteristics of true color and high quality, this paper proposes apply DSLR to probe spacecraft in order to obtain better quality Color images. Firstly, the performance parameters of mainstream DSLR and industrial-grade optical detector are analysed and compared detailedly; Secondly, the performance and positioning ways etc. of optical detector and DSLR system integrated special telephoto lens are analysed and compared. Furthermore, some experiments have been done in different conditions. The experiments indicate that the performances of DSLR and optical detector are similar. In addition, DSLR has the advantage of small size, low cost and Easy positioning, which can be used to obtain the scene of spacecraft in the takeoff phase and part of reentry phase.
Efficient manufacturing technology of metal optics
Author(s):
Jizhen Zhang;
Yanxiong Wu;
Xin Zhang;
Liping Zhang;
Lingjie Wang;
Hemeng Qu
Show Abstract
The efficient manufacturing technologies greatly accelerate the development and production process. Optical components have higher precision requirements than mechanical parts. This provides great challenge for rapid manufacturing. Metallic optical system is featured high resolution, wide spectral range, light weight, compact design, low cost and short manufacturing period. Reflective mirrors and supporting structures can be made from the same material to improve athermal performance of the system. Common materials for metal mirrors in optical applications include aluminum, copper, beryllium, aluminum beryllium alloy and so on. Their physical characteristics and relative advantages are presented. Most kinds of metals have good machinability and can be manufactured by many kinds of producing methods. This makes metallic optical system saving 30%~60% cost and time than others. The manufacturing process of metal mirror is different due to its working spectral. The metal mirror can be directly manufactured by single point diamond turning. This is an outstanding technique in point of ultra-precision as well as economical manufacture of mirrors. The roughness values and form accuracy of optical surfaces after diamond turning can satisfy the quality level for applications in the near infrared and infrared range. And for visible light spectral the turning structures must be removed with a smoothing procedure in order to minimize the scatter losses. Some smoothing methods to obtain visible quality metal mirrors are given in this paper. Some new manufacturing technology, such as 3D printing, can be used for metallic optical system and several promising techniques are presented.
An optical system design that converts a Gaussian to a flattop annular beam
Author(s):
Chaochen Li;
Tengfei Wu;
Yu Wang
Show Abstract
Flattop annular beam has been predicted with good character over an increasing application, but the generating of flattop annular beam is rarely mentioned by academic article. In our paper, an optical refractive system, which is designed to achieve flattop annular beam, are proposed. The cone prism is commonly used to get an annular beam, however, the beam intensity distribution is non-uniform. In our design, an additional aspheric lens is placed in front of the cone prism along the optical axis. The lens parameters are theoretically analyzed and well optimized to homogenize the optical field. Furthermore, to lower the requirement of machining accuracy, a pair of aspheric lenses is also designed, which can be used independently to generate flattop annular beam. It combines the function of cone prism and aspheric lens, so as to replace them both. The performance of the implementations has been demonstrated in detail. Simulation result shows that the proposed design is effective and feasible. It is hope that our work would be helpful in related fields. Flattop annular beam, Aspheric lens, Cone prism
Optical system design for lens with large relative aperture
Author(s):
Kaisheng Zhang;
Zhi Zhang;
Zhaohui Zhang;
Zefeng Wang;
Aqi Yan;
Jiaqi Fei;
Chao Mei;
Gaopeng Zhang
Show Abstract
As the space remote sensing technology progresses, the developing trend of telescope is larger and larger aperture, higher and higher resolution. An Optical system with the relative aperture of 1:2 is introduced. The primary optical properties are: focal length of 120mm, F number of 2, field angle of 7.4°. It has the advantages of large high resolution, small size and excellent image quality. Several kinds of aberration curves and the MTF curve are given. Its imaging quality is nearly diffraction limited so that the spatial frequency is greater than 70lp/mm when its modulated transfer function (MTF) value of the optical system is equal to 0.8,and the optical system distortion is less than 1%. At last, the stray light is analyzed and the baffle of the telescope is designed. The solid model of the Optical system was constructed in Tracepro software, the point sources transmittance (PST) cure was given at different off-axis angle between 7.4°~80°,the analysis result indicates that the PST values are less than 10-6 when off-axis angle are larger than soar critical angle. So the system is suitable for observation or photography of deep sky objects.
The finite element analysis of zoom optical system with no moving parts
Author(s):
PuRui Shi;
Lin Li;
Yifan Huang;
Xing Han;
Bin Ma
Show Abstract
For the method that active optical system achieves zoom by changing the surface of deformable mirror, the design of the brake, the rationality of the layout and the actual change of the surface are very critical issues. This paper presents a practical research idea and method. The finite element model of a deformable mirror was established based on finite element analysis software, and the analysis is achieved after configuring the brake method that needed. The feasibility of the drive scheme is verified through comparing the simulation results and the ideal surface. On this basis, the preliminary design of the core components of piezoelectric ceramic driving circuit brake is achieved.
Anodic fluoride passivation of InAs/GaSb type II superlattice infrared detector
Author(s):
Lixue Zhang;
Xiancun Cao;
Guansheng Yao;
Liang Zhang;
Junjie Si;
Weiguo Sun
Show Abstract
One of the major challenges of InAs/GaSb superlattice devices arises owing to the large number of surface states generated during fabrication processes. Surface passivation and subsequent capping of the surfaces are essential for any practical applicability of this material system. In this paper, we passivated InAs/GaSb superlattice infrared detectors proposed anodic fluoride passivation method. Short and mid wavelength InAs/GaSb superlattice infrared materials were grown by Molecular Beam Epitaxy (MBE) on GaSb (100) substrates. A GaSb buffer layer was grown for optimized superlattice growth condition, which can decrease the occurrence of defects with similar pyramidal structure. The result of auger electron spectroscopy (AES) surface scans after anodic fluoride passivation confirms that anodic fluoride passivation treatment did affect. The leakage current as a function of bias voltage (I-V) for InAs/GaSb superlattice infrared detectors has been examined at 77K. Compared with the unpassivated approach, this passivation methods decrease the dark current by approximately five orders of magnitude.
3D model-based detection and tracking for space autonomous and uncooperative rendezvous
Author(s):
Yang Shang;
Yueqiang Zhang;
Haibo Liu
Show Abstract
In order to fully navigate using a vision sensor, a 3D edge model based detection and tracking technique was developed. Firstly, we proposed a target detection strategy over a sequence of several images from the 3D model to initialize the tracking. The overall purpose of such approach is to robustly match each image with the model views of the target. Thus we designed a line segment detection and matching method based on the multi-scale space technology. Experiments on real images showed that our method is highly robust under various image changes. Secondly, we proposed a method based on 3D particle filter (PF) coupled with M-estimation to track and estimate the pose of the target efficiently. In the proposed approach, a similarity observation model was designed according to a new distance function of line segments. Then, based on the tracking results of PF, the pose was optimized using M-estimation. Experiments indicated that the proposed method can effectively track and accurately estimate the pose of freely moving target in unconstrained environment.