2020 Vol. 41, No. 6
The target orientation technology of tethered lift-off platform has been widely used in the military and civil fields. The orientation performance has become an important index to evaluate the comprehensive performance of unmanned aerial vehicle (UAV) and tethered lift-off platform. The precision test research of photoelectric detection system was carried out, the emphasis was high precision orientation error analyses about the target, the photoelectric detection system error transformation model was deduced, and the error conversion coordinates were verified by simulation. By Monte Carlo thought, the influence of error parameters is analyzed to the orientation accuracy of the photoelectric detection system, and the method about target’s high precision orientation is improved, which provides a theoretical basis for target orientation accuracy and high precision design about photoelectric pod of unmanned lift-off platform.
In order to meet the requirements of the high image quality, high zoom ratio, long focus and miniaturization zoom optical system for the foreign object debris detection, a 50 mm~1 000 mm zoom optical system based on Zemax optical software was designed. The mechanical compensation zoom type was adopted to realize the zoom system, the extra-low dispersion lenses were adopted to reduce the chromatic aberration and secondary spectrum was introduced by the long focal length. Meanwhile, the merit function operands was used to simultaneously optimize the image quality and design the miniaturization system. The system contains 28 lenses and the total length is less than 400 mm by optimizing design. The on-axis modulation transfer function (MTF) is above 0.2 at 100 lp/mm, which means near the diffraction limit generally. The system field curvature is less than 0.1 mm and the distortion is less than 1%. The system can satisfy the change regulation of the mechanical compensation cam curve, and the curve is continuous and smooth. The analysis results show that the system can meet the practical application requirements of the foreign object debris detection around airport runway, furthermore, it’s significant for the design of large zoom ratio zoom optical system.
Since UAV(unmanned aerial vehicle) image frames has characteristics such as high speed moving platform, intensity view rotation, real-time processing and so on, a UAV ground target image frames detecting and tracking algorithm based on two-level rotation invariant feature space detection and tracking on account of parallel feature extraction was put forward. The detection algorithm used primary matching and meticulous matching to reduce the algorithm complexity. The theoretical analysis and experiments showed that the proposed algorithm has better real-time performance, insensitive to image rotation and have better performance on abnormal conditions and the primary overall-match process in proposed algorithm can act as the pretreatment of other image matching and tracking algorithms. The experiment results indicate that the proposed algorithm can ensure stable target tracking under the situations of UAV images. At the same time, the detecting process has better real-time performance, which can meet the real-time processing demand of target detection and track of UAV image frames.
The influence of glare on humans is an important factor on the research of cab’s lighting environmental ergonomics. For the modern train, more attention need to be payed to the cab’s interface to the purpose of dealing with the porblems faced during the drive, and therefore the glare has the possibility of endangering the safety of driving. The optical simulations were proposed and the principal component analysis method was used to find factors which had great influence on the cab. Combined the results of physical tests and simulations to propose some methods about the main factors that were effective for reducing the glare inside the cab and increasing the visual comfort of the cab. The results show that the console lamp has the greatest effect on the overall light environment of the cab, and recommendations for improvement have been presented according to the results.
It is necessary for the design of car seat to realize the high precision and real-time measurement of the 3-D human pose on the car seat. Based on the existing 2-D and 3-D human joint measurement methods, a 3-D human pose measurement method is proposed, which integrates deep learning and epipolar constraint. This method combines 2-D human joint depth network extraction method with binocular measurement system, uses two-channel multi-stage iterative network to extract 2-D human joint points in the images taken by left and right cameras respectively, combines the Brief feature of joint point position and epipolar constraint, uses binocular camera calibration results to convert the matching 2-D joint point information into 3-D space, and finally obtains 3-D human pose. The experimental results show that the detection accuracy of the proposed method in the self sampling test set can reach 98%. The deviation of the angle of the key position of human body calculated by the 3-D joint point is less than 10°. Therefore, the method proposed in this paper can meet the data acquisition requirements of the actual car seat design.
The principle of the triangulation is used to conduct the 3D measurement by binocular vision measurement system, and its structural characteristics determine that the measurement error increases with the increase of the measurement distance. Aiming at the distribution law of the measurement error, the optimization method of the binocular vision measurement system based on the local FOV was proposed. The measurement coordinate system was established by using the external structure to reduce the systematic errors introduced by the inconsistence of the calibration and measurement process information. The coupling effect between camera parameters was used to compensate the calibrated error of the system inherent parameter, and a look-up table was established to realize the virtual mapping of the calibration parameters. The results show that the maximum error is less than 0.03 mm in simulation experiment, and the measurement error is less than 0.3% in systematic experiment. After the optimization, the main measurement error comes from the random error introduced by the detector discretization, and the binocular vision measurement system achieves the theoretical measurement accuracy.
In order to measure the incident angle of light, a new light incident angle measuring system based on conical lens was designed. Using the diaphragm, the conical lens and image receiving device could obtain a complex light spot image. These images were formed by multiple refractions and reflections after the light entered the conical lens through the aperture. The image feature information of the light spot was obtained through image processing, and then the incident angle of light was solved. With this measurement scheme, the angle measurement range can reach to 80°, and the accuracy can reach up to (1×10−4)″. At the same time, the scheme has a simple structure, small size and does not require cumbersome installation and debugging. Compared with the existing single-spot measurement methods, the conical lens in this solution has an angle magnification effect, which can greatly improve the measurement accuracy and has a large field of view, and the pixel resolution of the image sensor has little effect on the measurement results, and the system luminous flux is large. So it is easy to obtain a higher signal-to-noise ratio.
For leather surface defects with the machine vision on-line detection, the image quality of some leather surface defects presented aeolotropism to the lighting direction, and the defects even failed to be shown, therefore the non-detection zone was formed. Considering this problem, an on-line detecting system which could eliminate the non-detection zone was designed. Based on the scattering and the information acquisition mechanism of the defect, the change law of the defect feature light intensity with the lighting direction was obtained. An experimental study on the defects of imprinting and ink was carried out to show that these two types of defect feature light intensity distributions were related to the lighting direction, and the non-detection zone as well as the effective zone of defects presented a orthogonal state. According to this, a self-designed off-axis plane light source with side-entering uniform irradiation was adapted to design the on-line detecting system for the orthogonal composition with linear array and planar array. The vertical target plane was used to collect the information and the dark field orthogonal lighting was carried out at 45°. The main detecting system was composed of the linear-array camera and the linear light source, while the auxiliary detecting system was composed of the planar camera and the off-axis plane light source to detect hundreds of samples of random anisotropic defects. The experimental results show that the defects non-detection zone is effectively eliminated, the defects recognition rate is increased by 22%, and the detection effciency is also greatly improved.
In order to characterize the asymmetric deflection deformation of panels in hidden frame glass curtain wall under complex boundary conditions and wind loads, the digital image correlation technique was employed on the curtain wall sample and realized the non-contact full-field flexural deformation measurement. A set of comprehensive evaluation methods for wind resistance performance of glass curtain wall based on the normal distance on the flexural surface of the glass panel, the Gaussian curvature, the surface principal strain and the strain energy density distribution was accordingly proposed by reconstructing the flexural morphology of the panel. The calculation results show that under the situation of initial deflection morphology and structural coupling effect, the maximum surface normal distance of panel after deflection is 6.02 mm, which is less than the current standard experimental calculations. Therefore, the curtain wall is actually more resistant to the wind load; The corner regions of the panel are deformed as a hyperbolic paraboloid, which also have potential safety hazards, with the maximum in-plane principal strain occurred in the upper left corner in 257 με. Therefore, this method not only avoids the shortcomings of the traditional instrument limited by the measured results of specified point, but also demonstrates the full-field spatiotemporal dynamic behavior of the glass panel deformation, which provides a convenient and effective method for characterizing the wind resistance performance of the hidden frame glass curtain wall.
Images taken in hazy days suffer the problems of color distortion and blurred image details, which lead to a negative impact on the image quality captured by imaging equipment. Aiming at solving the degradation problem of image collection in hazy weather, a dehazing network based on multi-scale dilated convolution was proposed. The generator of the dehazing network was composed of convolution modules with different dilated rates, and combined with multi-scale strategies to increase the receptive field and enhanced the dehazing effect; the discriminator used multiple convolution modules to distinguish the generated dehazed images from real haze-free images; by calculating the perception distance between the dehazed images and the real haze-free images, the texture structure of the images was optimized and the noise signal was reduced. The experimental results show that the peak signal-to-noise ratio obtained by the proposed algorithm on the public data set is 22.410 dB, the structural similarity value is 0.844, and the color difference value is 10.545. Quantitative and qualitative evaluations show that the dehazing network designed with dilated convolution and perceptual loss can effectively restore the color information and texture structure of the images.
In order to solve the problem of insufficient positioning accuracy, error accumulation and long time consuming of feature point matching method, a visual odometer that combines RANSAC optical flow method and improved feature point matching method was designed. The RANSAC optical flow method was used to estimate the small-scale motion between key frames. The RANSAC algorithm eliminated the mismatch points of optical flow, which greatly reduced the mismatch existing in the optical flow method. The motion estimation between key frames used the improved feature point matching method to correct the estimation error of the optical flow method. Finally, the RANSAC optical flow method and the improved feature point matching method were fused by using the Kalman filtering. The experimental results show that the algorithm can overcome the problems of insufficient accuracy and error accumulation of the optical flow method, which increases the MRE from 15.5% to 2.6%. And it can also improve the speed of the feature point matching method, which increases the average consuming time from 37.28 ms to 21.07 ms.
A confocal measurement method for hardness indentation surface area with diagonal length less than 20 μm was proposed. The indentation of samples was scanned and measured by laser scanning confocal microscope at an interval of 0.1 μm. The three dimensional data of indentation were obtained by the enveloped fitting of all data sets. The method of rotating plane was combined with the feature of normal vector to extract the indentation accurately. The surface area of the indentation was obtained by the triangular mesh construction algorithm, and the hardness value of the sample was calculated. Compared with the traditional imaging optical microscope method, the resolution of confocal measurement method was improved by 30%, and the uncertainty of synthetic standard decreases by 1 HV on average. The results show that the confocal method can measure the indentation surface area with high accuracy and high stability.
For explosives in atmospheric environment, the radiation intensity of the test method is relatively mature. With the rapid development of high altitude or outside atmosphere explosives development technology, for such explosive transient testing requirements of infrared radiation intensity become more and more urgent. Since the outer space environment was a kind of low temperature near the vacuum environment, and the field measurement was not available, it was creatively put forward the simulation of vacuum environment in the laboratory to test the infrared radiation intensity of explosive, and a dedicated vacuum environment and testing methods were further established. The 4 sets of specific components of the fire explosives were measured using the special test equipment, and the measurement results were analyzed. In view of the existing problems, the future direction of improvement was expounded.
In order to realize high accuracy absolute radiometric calibration of large aperture integrating sphere source, the spectral radiance calibration method based on tungsten strip lamp was studied, then the spectral radiation uniformity calibration method through concentric scanning was discussed. An absolute radiometric calibration device was developed on this basis. The spectral radiance, luminance and color temperature of the integrated sphere source with the opening diameter of Ф300 mm were calibrated. The results of experiment prove that the uncertainty of spectral radiance absolute calibration is less than 4%.
The low-level-light (LLL) night vision machine can effectively observe the target under the poor illumination conditions at night, and the target contrast observed at night is an important indicator of the influence factors of the whole operating distance. In order to meet the urgent need of target contrast data for night observation theoretical analysis and test of LLL night vision machine. Based on the use characteristics of the 3rd generation LLL image intensifier with good matching with the natural light radiation spectrum under starlight conditions, an imaging device based on the 3rd generation LLL ICCD is built. From the energy transfer chain of LLL imaging system and the visual characteristic equation of optoelectronic imaging system, the relationship between the ambient illumination, with the target-background reflectance ratio and the contrast is deduced respectively. The contrast test was carried out in dark room and natural night conditions. The test results show that when the illuminance is in the linear correlation illuminance interval [Es, Em] of the third generation LLL image intensifier, the contrast has nothing to do with the illuminance; for the same target and background, the target-background reflectance is closer to 1, the lower the contrast is.
Product color is an important indicator to measure product quality. Since the change of the light sources in the product circulation environment cannot be avoided, the color of the product will be affected by the change of the light sources undoubtedly. Therefore, it is of practical significance to study the color stability under different light sources. D65 light source was used as the standard light source, A and F2 light sources were used as the test light sources, a large number of color blocks were chosen as samples, and the color difference of the sample under different light sources was used to measure the color stability of the sample under different light sources. Firstly, by analyzing samples with different excitation purity, it was found that there was a positive correlation between the color difference and the excitation purity; Secondly, by analyzing samples with different dominant wavelength/complementary wavelength, it was found that the color difference was related to the dominant wavelength/complementary wavelength closely. When the dominant wavelength of the sample was 479 nm, ΔEab*(D65/A), ΔEab*(D65/F2) were 14.50, 13.81 respectively. When the dominant wavelength of the sample was 561 nm, ΔEab*(D65/A), ΔEab*(D65/F2) were only 5.17, 2.78 respectively. After corresponding to the dominant wavelength/complementary wavelength and the hue, it showed that the samples with purple, yellow, yellow-green hue had smaller color difference under different light sources, while the samples with red, cyan, light blue hue had larger color difference. The results showed that the color stability under different light sources was related to the excitation purity and the dominant wavelength/complementary wavelength. In actual production and application, there are two ways to improve the color stability of the product under different light sources, one is to choose a color with lower excitation purity, and the other is to choose a color with purple, yellow, yellow green hue.
As a new gas concentration measurement technology, tunable diode laser absorption spectroscopy (TDLAS) is widely used in the field of NH3 concentration measurement. Using Matlab visual modeling and simulation software Simulink to realize the direct absorption measurement process simulation of NH3 concentration TDLAS with mid-and-far infrared quantum cascade laser (QCL) and near-infrared distributed feedback laser (DFB) as light source, under the environmental parameters of flue gas denitration and normal temperature and pressure respectively, the sensitivity, detection limit and resolution of NH3 concentration measurement were theoretically analyzed. The results show that theoretical sensitivity of the QCL-TDLAS system is about 50 times higher, compared with the traditional near-infrared DFB source. The detection limit and resolution can reach the ppb level, and the trace NH3 concentration measurement capability is greatly improved. The simulation process and results provide theoretical basis for QCL-TDLAS technology in NH3 concentration measurement.
The research for calibrating of high irradiance above 1000 W/m2 of infrared irradiance meter was provided. According to the actual situation of the calibration experiments, the methods for calibrating irradiance meter with and without optical imaging system were discussed, the calibration algorithm for each kind of meter used in variously conditions was described. The principle for calibrating high irradiance using radiator having great radiance or large emitting surface was presented. The special calibration facility used in laboratory was built, the calibration activity utilizing a point source blackbody which highest temperature above 3000 ℃ and an 800 ℃ extended blackbody were hold respectively, and the measurement results were also analyzed. Finally, measures for improving irradiance calibration accuracy were discussed.
As artificial intelligence algorithm was introduced into target detection, the detection of spatial infrared dim targets could be classified as the binary problem of fuzzy detection. According to the detection model of infrared dim target in the air, a signal voltage ratio spectrum model was established. The simulation analysis showed that the variation trend of voltage ratio was related to the speed, attitude of the target and the two-machine posture, which could be used to detect the target. The dynamic characteristics building theory was adopted to build the bicolor ratio feature space of infrared dim target. Based on this feature space, the least squares classification algorithm was optimized to identify the objects from the spectral signal hierarchy. This method not only reduces the amount of the sample data, but also prevents the phenomenon of over-fitting caused by the parameter selection of Gaussian kernel function. It ensures the classification accuracy and improves the classification efficiency nearly doubled. Reference basis is provided for infrared dim target detection by artificial intelligence algorithm.
Signal detection of weak vibration in long-distance is of great significance in the fields of machine manufacturing, national defense, military, and so on. Aiming at overcoming the shortages of traditional measurement systems, a long-distance vibration measurement system was built based on the solid-state microchip laser frequency-shifted feedback technology. The system sensitivity index, including working distance, incident angle, and non-cooperative objects were further analyzed. The experimental results show that the high-quality acquisition of the weak vibration signal at 100 m distance is achieved, the frequency measurement error is less than 0.1% and the signal-to-noise ratio is still close to 20 dB under an incident angle of ±60° with using paper box as the target. In addition, the system can measure vibration of a variety of non-cooperative targets such as milk powder bags, polyfoams and so on. The system can be used flexibly in mechanical vibration measurement, remote monitoring and other fields, showing great promotional value in engineering applications.
In order to reduce the error recognition rate of high repetition pulse laser ranging echo signal and improve the ranging performance, the adjustment technology of high repetition pulse laser ranging echo signal is studied deeply. FPGA was used as the main control chip to generate laser modulation pulses, and square wave signals were selected according to the measured distance of 3.33 μs～33.33 μs, and the switch chip was driven to generate the time wave gate associated with the range, effectively filtering out the interference pulses in the pulse echo. This method improved the automatic gain control link of the conventional pulse laser ranging signal processing system. The test results show that within the dynamic range of 60 dB of the pulse echo signal, interference pulses introduced in the echo signal can be effectively filtered out, greatly reducing the possibility of error caused by the false recognition of interference pulses. This method can be applied to the pulse laser ranging signal processing system, and the ranging accuracy of the system can be increased by 12.6%.
In order to solve the problem of image stable transmission in electromagnetic interference environment, an fiber bundles image transmission system with the ability of anti strong electromagnetic interference was designed and developed. By using ZEMAX, the front objective lens and the rear eyepiece lens in the image transmission system was designed, respectively. And according to the initial aberration distribution of the objective lens and eyepiece lens, the system aberration was further optimized by using the optimized function and various operation numbers. The optimized results show that, the MTF value of each field of view of the objective lens is greater than 0.85 at the spatial frequency of 38 lp/mm, and that of each field of view of the eyepiece lens is greater than 0.3 at the spatial frequency of 120 lp/mm, which has high imaging quality. According to the structural characteristics of the selected objective lens, eyepiece lens, fiber bundles and CCD, the coupling device of system connection is designed and manufactured, and the image transmission system is built for the image transmission experiment. By analyzing the imaging quality and influencing factors of the system, the image brightness is improved by using the Gamma algorithm, and the high-quality transmission image is obtained.
In view of the problem that the exploration and development of oil and gas fields need to obtain the complete waveform of micro acoustic disturbance signal, the research and development of distributed optical fiber acoustic sensor (DAS) technology and supporting system based on the scheme of double pulse heterodyne modulation and arctangent heterodyne demodulation were carried out. Combined with the indoor vibration simulation experiment of characteristic parameters, the response frequency range of the new DAS system is 20 Hz~25 kHz, the maximum dynamic range is 60 dB, and the signal-to-noise ratio is 49 dB, which can meet the detection requirements of micro acoustic wave of the amplitude, frequency and phase of the complete waveform. Meanwhile, the system has been successfully applied in the detection of underground steam cavity in heavy oil development of Xinjiang Oilfield. The actual effective sound pressure intensity is −195 dB, which verifies the reliability of the system and has a good application prospect.
In order to improve the recognition ability of abnormal data in optical fiber communication networks, an abnormal data detection algorithm based on the optimization of entropy objective function was proposed. Firstly, the attributes of the data samples were classified, and the radius of the neighborhood interval was selected based on the abnormal data feature density index. Secondly, the clustering degree of the big data with high-order statistics was iterated and the optimization of the feature extraction parameters was completed. Finally, the optimal value of the entropy objective function was calculated according to the sample attribute probability, and it was used to complete the abnormal data detection. The experiment tested 1 000 sets of communication data. The results show that the average detection accuracy of this algorithm is about 95.7%, and its data fusion rate, detection time-consuming and average false detection rate are better than that of the two traditional methods. It can be seen that this algorithm has the advantages of high accuracy, fast convergence and low false detection rate, which has the certain application value.