2018 Vol. 39, No. 1
Taking the airborne platform as the research object, firstly based on analyzing the principle of the photoelectric reconnaissance system to achieve the target geo-location, the main factors affecting the target geo-location accuracy of the photoelectric reconnaissance system are obtained: the electro-optical reconnaissance system position-error, azimuth-error, attitude-error and the distance from system to target, etc. Secondly the target geo-locating error model for electro-optical reconnaissance system are educed. Analysis and emulation for the relationship among target geo-locating accuracy and azimuth-error, attitude-error indicate that azimuth-error, pitch-error of electro-optical reconnaissance system are the uppermost factors which affect the target geo-locating accuracy, and it is reasonable for the inertial navigation that the azimuth-error is oontrolled in 0.02°~0.5°, the attitude-error is controlled in 0.01°~0.25°. Finally, some suggestions to improve the target geolocation accuracy are put forward.
In order to solve the problem of nonuniform distribution of light intensity on the receiving surface of solar cells after the solar light was collected by the conventional Fresnel concentrator, a belt type Fresnel concentrator was designed.According to the Fresnel belt design method, the receiving surface was divided into corresponding zones, which made the light first pass through the surface belt of Fresnel condenser then enter the corresponding receiving surface strip, so as to reduce the optic energy loss and improve the uniformity of light intensity distribution.This paper gave an example of Fresnel condenser system with the solar flare angle of 0.54°, the diameter of 200 mm, the height width ratio of 0.65 and the concentration ratio of 400 in the wavelength range of 350 nm~760 nm, simulated and analyzed the optic capability of Fresnel condenser by Tracepro.Results show that compared with traditional uniform Fresnel lens condenser of the same parameters and in the case of the same size receiving surface, the spot energy distribution uniformity of the belt-type Fresnel lens reaches 75%.
Terahertz(THz) band locates between the infrared and microwave and has great application prospects in the fields of national defense such as space communications, short-range tactical communications, and so on.The characteristics, categories, solutions and the key technologies involved in terahertz communication system are summarized.Research status and achievements of terahertz communication system at home and abroad in recent years are introduced, and the communication distance reaches 20 km at 0.14 THz band, the communication transmission rate reaches 105 Gb/s at 0.3 THz band.Several communication technical routes are analyzed, that conclude all electronics method, optoelectronics method and quantum cascade laser communication method, and their advantages and disadvantages are compared.Additional, the development trend and application prospect of terahertz communication technology are viewed.
In order to change the focal length of optical system rapidly and at a low cost, we designed the zoom structured light three-dimensional imaging lens and micro-lens array based on liquid lens.The system utilizes the structure of seven spherical glass lenses and one liquid lens, the F# number is 3.2, the full field of view(FOV) is 10 mm, the system total length is 180 mm, and the focal length ranges from 54 mm to 61 mm. The design result shows that, the system can adjust the distance of projection in 227 mm~256 mm; during focusing process the target surface is clear and the resolution ratio has a high quality, while system is within the whole zoom range; at 40 lp/mm, the modulation transfer function(MTF) of full FOV is better than 0.2, the system field curvature is less than 0.2, and the distortion is less than 0.2%.The cylindrical micro-lens array has an overall size of 10 mm×10 mm, a period width of 1 mm and a thickness of 1 mm. With the increase of projection distance, the imaging quality of optical system increases first and then decreases, the imaging quality is optimal at 237 mm; as the projection distance increases, the magnification of the optical system increases; the overall relative illuminance heterogeneity of optical system is less than 0.2.
Quad-element detector is a key sensor of the third generation infrared seeker. In order to implement effective jamming to the seeker, this paper firstly discusses the detection mechanism, and secondly proposes the interference strategy which disturbs the auto gain control (AGC) circuit working.The jamming process is then simulated and analyzed.Finally, the average effective jamming ratio is acquired by Monte Carlo method when frequency difference exists, or duty cycle varies, or phase changes on jamming laser.The simulation conclusions are as follows:at the same or multiple frequency with the seeker and 0.25 duty cycle, high power jamming laser can lead the AGC circuit working abnormal; moreover, adjusting the pulse laser phase can influence the jamming effect and destroy the signal extraction logic, finally, the deception is achieved.The analysis and results of this paper are of theoretical significance for the development of laser directional infrared countermeasure system.
In view of the traditional fundus camera which can not check the defects of retinal edge, a non-mydriatic wide-area retinal imaging system based on Volk contact lens is proposed.In sufficient lighting conditions, Volk lens can reach more than 130° field of view(FOV).The illumination way is improved based on traditional fundus camera, and by the way of using external annular fiber illumination, the retinal wide-area illumination is realized. The incident angle is increased to eliminate the influence of ghost image, and the dark spot phenomenon in center region can be avoided which is caused by annular lighting meanwhile.The objective lens group eliminates the stray light caused by the corneal reflex and uses the manual focusing method to make a clear image on the complementary metal-oxide semiconductor (CMOS) camera.The fundus images are collected by the colorized CMOS camera with (2/3)′ image acquisition board and then uploaded to the PC terminal in real-time for analyzing, processing, archiving and other operations.Images after post-processing can provide clear, objective bases for the diagnosis and screening of varied kinds of eye diseases.
A method for solving object data based on imaging matrix is proposed. Through one-dimensional processing of the object and image matrixes, a two-dimensional imaging matrix is constructed.Thus, the operation rules of image matrix by convolution of object matrix and point spread function matrix were transformed into the image vector by one of the product of object vector and imaging matrix.Finally, the image vector is obtained by multiplying the vector by the inverse matrix, precise solution of the object data from the image data of optical system is realized and the calculation error can reach the order of 10-12.
The depth value of Kinect sensor changes randomly when the depth image is obtained.In order to solve this problem, this paper presents an image repairing method combined with Kalman filtering and multiple frames averaging based on the idea of optimal estimation.Firstly, Kalman filter is used for repairing multiple depth images.The depth value tends to be stable with time recursion in the process of information capture by Kinect sensor.Secondly, multiple frames averaging method is used to determine the final depth image, in order to solve the problem of inaccurate depth value due to the error of Kinect sensor.The experimental results show that, the root mean square error of the algorithm is 38.102 5, the average gradient is 0.471 3, the information entropy is 6.191 8, the edge of depth image of this algorithm is more clearly when compared with the single image restoration.
A no-reference image quality assessment method based on bottom-up visual attention mechanism and top-down image sharpness metric is proposed for the blur image quality evaluation.Firstly, the color, intensity and orientation feature maps are calculated based on the human visual attention mechanism, and then the saliency region of the image is obtained by the winner-take-all competition. Secondly, the image of saliency region and the background region are evaluated using no-reference image sharpness evaluation method, and the final image quality index can be obtained by the combination of the above two results.The radial blur images produced in the forward motion imaging and the Gauss fuzzy images in the Live database evaluation are evaluated using the proposed method respectively.Experiment results can prove that the correlation coefficient between the results of our method and the subjective one is larger than 0.98 for the radial blur images.The method can be used for evaluating the blur image subjectively.
The existing color image enhancement methods are mainly used for directly enhancing color images obtained under the condition of uneven illumination or low light, and color images acquired by low-light-level(LLL) color imaging system are obtained by separately collecting tricolor images fused.According to this, a method is proposed to improve color image enhancement based on LLL tricolor image denoising and fusion. Firstly the LLL tricolor image is denoised by using wavelet transform and fused into a color image, then the color image is transformed from RGB color space to HSV color space.Secondly V is enhanced with MSR in HSV space and the enhanced image is adjusted by S. Finally it is converted back to RGB color space. This denoised and enhanced image is evaluated by objective evaluation method. Results show that this denoised and enhanced image is better than that of the tricolor image fused directly, and average increase rate of average value, variance and information entropy are 11.37%, 8.46% and 0.44% respectively. The method can be transplanted into LLL color imaging system, which has strong guiding significance for improvement of image quality.
Based on the study of the principle of dual-tree complex wavelet transform, a cloud removal method was proposed by combing the frequency differences of cloud-mist and scenery.A hardware system for cloud and mist removal was designed and established.The system structure and development procedures were introduced.The design methods of the camera driver, video signal output program and man-machine interaction interfaces were described.Additional, the image acquisition and cloud-mist removal processing were implemented by applying the designed system, and the procession results were presented and analyzed.Results show that the entropy of this algorithm is 7.61 when the decomposition level number, the dividing number and the weight factors have the default values, proving that the proposed algorithm can achieve better results than the wavelet threshold method and the homomorphism filtering method.The designed system has a pleasant ability for cloud and mist removal as well as a strong adaptivity.
In order to reduce high time complexity and long time of star image recognition of traditional triangle star pattern recognition algorithm commonly used in star sensor, an improved fast star pattern recognition algorithm was proposed.The algorithm preserves star diagonal distance and angular distance tolerance set by constructing an array of two-dimensional linked list, which avoids repeated calculation and repetitive searching process of star diagonal distance. Then a new star matching method by using hash table is constructed, which can reduce the number of star pairs of angular matching and time complexity of triangular star map recognition significantly. Experimental results show that starred recognition time of improved algorithm is reduced by 70% compared with traditional triangle star pattern recognition time under different star perturbations and different observation star numbers, which is significant to improve the attitude updating frequency of star sensor.
In order to satisfy the requirement that the vehicular electro-optical reconnaissance system can quickly share target information to relevant auxiliary weapon system real-timely in wild environment, a method for sharing target information of different photoelectric platforms, as well as the error analysis of this method are presented.By introducing the informations such as the attitude angle of auxiliary weapon platform and the attitude angle of EO reconnaissance platform, the method can transmit the target information detected by EO reconnaissance system to auxiliary weapon system precisely in real time.In order to verify the correctness of the method, through the modeling analysis, it is concluded that the method can realize the sharing of target information.The error of the method is analyzed by simulation test, results show that the target information after conversion by the method can improve by about 3.5 m in terms of accuracy compared with the direct use of the collected target information.
In order to realize optical detection of underwater vehicle, the mechanism of optical properties measurement of underwater environment is studied, and measurement method for ocean downward radiation and upward radiation is established. Based on the analysis of distribution law of ocean downward radiation, the ocean downward radiation model is simplified, Janus ocean downward irradiance measurement model is established, the irradiance optical probe is designed, the ocean upward radiation measurement method is determined, and the optical probe response scale is designed. Results show that downward irradiance is determined by scalar irradiance, scattering coefficient, volume attenuation coefficient and diffuse attenuation coefficient. The incident angle is the incident radiance. When incident angle is less than 70 °, cosine error is less than 5%. Measurement of ocean downward irradiance is optimized by Janus design. The establishment of ocean downward radiation and upward radiation measurement method has laid a technical support for underwater visualization of target environment.
In current measurement of the freeform spectacle lenses using wavefront sensor, the diameter of progressive addition lenses is usually larger than the receiving aperture of wavefront sensor, it is mainly used to measure the wavefront aberration of the lens by means of the sub-aperture stitching technique.In order to solve the problems of complicated operation and large amount of data processing in the measurement of the sub-aperture stitching technology, a method of beam expanding-shrinking system measurement for wavefront aberration of progressive addition lens was presented, through which the wavefront aberration within 22 mm diameter circular area of progressive addition lens could be got.In order to verify the reliability of the test, the measured defocus co-efficients in Zernike representation of wavefront aberration were transformed into spherical mirror degree, and compared with the spherical mirror degree measured by fringe deflection method. Results prove that the method based on the beam expanding-shrinking system is feasible.
The traditional Michelson interferometer can only simply present the interference image of light, and can not vividly reflect the fluctuation and morphological characteristics of light.Moreover, the measurement process is tedious.Aiming at these problems, a novel Michelson interferometer experimental device based on digital holography technology was presented.Instead of the plane mirrors of the traditional Michelson interferometer, two charge coupled-device (CCD) cameras were used to record the interference fields, which were generated by the interference of the spherical light and the planar reference light.Then the complex amplitude information of spherical light on the CCD recording plane was obtained directly by using the digital holography, and the least square fitting was utilized to compute the spherical parameters, the complex amplitude of spherical light was demodulated to obtain the centering complex amplitude.Finally, the interference phenomenon of two spherical lights was realized by digital interferometry.Experiment results show that the device can vividly display the 3D image of the incident spherical light and the interference image of two spherical lights in real time.In addition, according to the fitting parameters, the refractive index of transparent equal thickness medium can be measured conveniently.The refractivity of 3 kinds of materials measured by experiments show that the error can be controlled within ±5% and the measurement accuracy is high.
Vision positioning system is the key technology for improving the accuracy of high precision mounter.The machine vision was proposed to detect the deviation of surface mounted technology(SMT)components and PCB board.The regional growth method and the maximum internal rectangle method were used to calculate the displacement and angle center of the SMT components and PCB board, respectively, and the displacement and angle that needed correction were obtained.Experiments show that the detection accuracy of the component center can reach 30 μm and the total processing time is 63.6 ms, so it can meet the requirements for fast detection of mounting components with high precision.
In order to solve duality in pose estimation of single circle feature, a method for eliminating the false pose of the target pose based on angle constraint is proposed. Under the premise of camera calibration, two or more images of circular target are obtained by translating the camera system on a horizontal plane. Based on the nature that real attitude angle of circular target remains unchanged in the camera coordinate system, the false solution can be effectively eliminated. This method can be applied to the industrial robot with a camera installed at the end of the robot, the false solution can be eliminated by controlling the robot to do the known translational motion. Experimental results show that the absolute error of the attitude angle is less than 0.5°, and the true position of the corresponding target is selected by the real attitude. The method is simple and easy to operate, which can accurately locate the true position of the object without additional high equipment. The success rate can reach 100%.
In order to meet the needs of making microchannel plate(MCP), a high-precision glass fiber production system was designed. For ensuring the test accuracy which caused by the servo motor vibration at working station within the allowable range, the three-dimensional model of the glass fiber production system was established by UG software, and the vibration modal finite element simulation analysis was carried out by finite element analysis software, so as to assure the reliability of the system.Experiments of glass fiber drawing were carried out after the system was completed.Experiments show that design fully meets the glass fiber accuracy required for making MCP needed, and it is find out that the best operating temperature and drawing speed of the system under the technical index are 751℃ and 4 m/min, respectively.
Aiming at the defects of low photoelectric conversion efficiency, short life, low radiation intensity and poor uniformity in the xenon lamp solar simulator, a spherical array LED solar simulator was presented which was based on LED solar simulator optical system.The design methods of collimating optical system, uniform light system and spherical array LED light source system were studied.Firstly, the technology of coaxial transmission optical system was used to design the collimating optical system with double-separation structure.Followed on the basis of analyzing the performance and the composing form of the frequent optical system, the design process of integrator and field diaphragm was described.And then based on the design idea of spherical light source, the design of spherical LED array light source system was finished.Finally, the optical system was simulated and verified by Lighttools optical design software.The results showed that the irradiation non-uniformity is less than 3.86% with greater than 1100 W/m2 irradiation intensity when the spherical array LED solar simulator was at a working distance of 100 mm and within the range of 100 mm× 100 mm.
The scanning compensation system is a key part of 3DLIF water measurement system to realize optical path scanning such as large-size planar laser, which determines positioning accuracy of planar laser beam in the fluid sink.This 3DLIF water measurement system has a long optical path length of 3 000 mm and a 500 mm wide light source, which makes it difficult to guarantee positioning accuracy.In order to solve this problem, influence factors of error factors and various factors in scanning compensation system are analyzed.Relevant error model is established and simulation analysis is carried out.The obtained error data are fitted by polynomial fitting and fitting result shows the angle between prism manufacturing and pitch of plane mirror around z axis are main factors that affect position error.In order to reduce the error, fitting result is further analyzed, and the relationship expression between two factors is obtained.Final simulation results show that position error of planar laser in the sink can be reduced from 0.618 mm to 0.103 mm by this method.
The development of Fabry-Perot(F-P)etalon is one of the key technologies of spaceborne scattering lidar.Based on the analysis of the influence of temperature on F-P etalon, combined with the conventional proportional-integral-derivative(PID)temperature control algorithm and fuzzy algorithm principle, a fuzzy algorithm and incremental proportional-integral-derivative(PID)algorithm with added anti-saturation parameter are proposed to achieve the control of F-P etalon temperature.The final set temperature is controlled within ±0.06 K.The algorithm is not only simple to achieve, but also has high control precision and good stability, which provides a powerful guarantee for breakthrough of narrowband optical reception of spaceborne scattering lidar.
Aiming at the pulse width intensity features of echo signal of long-distance laser range finder and the statistical characteristics of noise, a echo signal detection technology of high-precision multi-pulse laser range finder was proposed.The 400 MHz high-speed signal acquisition and digital processing was achieved by using the clock phase shift distribution way, so as to improve the echo pulse detection accuracy.An ARM embedded high-speed core processor was used for data processing, the functions of filtering noise reduction, adaptive threshold detection, multi-frame correlation detection and others were completed, which can make the signal-to-noise ration (SNR) increased by 7.6 dB and make the goal for acquiring long-distance target information accurately achieved.
The power of single-tube blue semiconductor laser is relatively low. In order to obtain high power laser output, the multi-tube fiber coupling technology was used to achieve 10 W blue laser output, and the white light source output synthetized by laser excitation phosphor sheet was taken as the car high beam light source.According to the requirements of automotive lighting regulations, an automobile high beam lighting system was designed, the optical structures of parabolic reflecting shade, biconcave lens and phosphor sheet as well as the influence of reflecting shade curve parameters, the positions of biconcave lens and phosphor sheet on the color temperature uniformity and illuminance of light source were described in detail.A elliptical parabolic reflecting shade with an elliptical opening of 19 mm×31.6 mm at the top, a circular opening of 5 mm diameter at the bottom and with the height of 60 mm was designed.When the phosphor sheet was placed at a distance of 15 mm from the reflector bottom, an elliptical spot of 5 m×12 m was obtained on the receiving surface 25 m from the light source, the white light source had a luminous flux of 1 025 lm and a center color temperature of 5 880 K, the central color coordinates were (x=0.322 6, y=0.369 2).Results show that the high beam lighting system meets the requirements of automobile lighting regulations.
Super continuous spectrum phenomenon can appear when using femtosecond laser in the process of transparent materials.On the basis of the principle of supercontinuum generation, the experimental scheme of linear polarization and circular polarization and PMMA materials with different energies is designed in order to analyze the threshold of supercontinuum spectrum of PMMA material under different polarized lights.Supercontinuum spectra of two polarized states of linear polarization (TE and TM) and circular polarization under different energies are analyzed and compared with superconducting spectra of the same energy. In the experiment, femtosecond laser with the pulse width of 160 fs and center wavelength of 775 nm is used. Experimental results show that energy of the same polarization is wider and spectrum width is wider. By comparing spectral characteristics under different energies, threshold of the spectrum and the circularly polarized light is 0.46 μJ and 0.586 μJ respectively. The spectral width of the linear polarization is wider than that of the circular polarization and circularly polarized light.
In order to make full use of multiplexing capability of fiber Bragg Grating(FBG) sensing system while the optical signal of each sensor along sensing optical can be detected effectively and to provide basis for sensor design and manufacture, based on FBG sensing principle, aiming at the system integration and optimization of multiplexing capability of the sensing system, the design method of wavelength division multiplexing and the design principle as well as criteria of node sensor structure and sensitivity were proposed and applied to the optical monitoring system of a real engineering.During working of the sensing system, reliable monitoring data about the engineering was obtained.Results show that the difference between monitoring results measured by FBG sensors and those from point-type electric instruments is about 6%, further indicating that there is no sensor signal crosstalk near the optical fiber sensor, which provides a useful reference for the engineering construction and safety maintenance.
Wavelength division demultiplexer is an important component used for dropping optical signals in the design of optical communication systems.The characteristics of micro resonator used for dropping optical signals are closely related to the performances of wavelength division multiplexing(WDM) demutiplexing systems. Single channel WDM demultiplexing structure based on photonic crystal square resonator(PCSR)was gradually optimized in the two-dimensional photonic crystal. With the help of coupled-mode theory(CMT), electromagnetic wave coupling interactions between waveguide and cavity were analyzed qualitatively, and operational characteristics of the structure were numerically simulated by the finite-difference time-domain(FDTD)method.The study results show that the single output port WDM demutiplexing structure based on PCSR has the characteristics of single resonant peak, broadly tunable ranges of central wavelength(1 501.4 nm~1 591.0 nm), narrow passband width(3.3 nm~9.1 nm)in the ranges of design parameters. It can be used for designing photonic integrated circuits, WDM demultiplexing optical communication systems, and etc.