Infrared and visible images have their own characteristics and different imaging principles, the targets be detected by any kind of sensor have their own advantages and disadvantages. In this paper, the characteristics of infrared and visible light images in dim and small target detection are analyzed, and pseudo-color infrared and visible light image fusion detection methods of dim and small target based on visual attention is studied, and its fusion detection effect is analyzed. The research shows that the fusion algorithm in this paper is more effective for targets with complex background and low contrast, and this method only makes pseudo-color mapping on a local area of the target, which is not easy to cause visual fatigue.
Detection, tracking, characterization and identification of space targets orbiting the Earth is one of the main tasks of the space surveillance system. Spatial target image feature extraction can find out some descriptions that reflect the essence of the target from the original image. The moment feature describes the statistical characteristics of grayscale by the moments of each order of image distribution, which can effectively reflect the shape information of the target. A Hu extension moment is proposed, and a feature extraction method for spatial target images is proposed based on this. It solves the problem of information loss when the confidence variance difference is large and the eigenvalue is negative. A linear combinatorial feature calculation method is proposed for spatial target classification, and a linear classifiable quantitative discrimination method is given. The image needs to be preprocessed. Then, the seven eigenvalues based on the extension moment are calculated, and the similarity analysis of the Hu extension moment is carried out. At last, the similarity of the sample target region matching is analyzed, and the target similarity can reach 90%. For image sets with multiple types of targets, according to the numerical distribution calculates the linear combination feature, linear classifiable quantitative discriminant results can be calculated. 48 images of four satellites in the database were selected as test data. Its recognition accuracy rate reaches 95.8%. Calculating the recognition result of the same platform for multi-sample joint recognition, and the probability of recognition attribution after multi-sample union is 100%.
Atmospheric turbulence is a major challenge in long-range imaging of ground-based telescopes, especially in the surveillance of space targets, whose observation distance is usually more than 100 km. In this case, space targets are extremely small in images, occupying less than 0.12% of the total image area, and suffer from severe blur and distortion. Consequently, the accuracy of object detection by both conventional and deep-learning-based methods is significantly hampered. Therefore, this paper proposes an effective framework for detecting space target through atmospheric turbulence. The framework incorporates a shallow deblurring module, a transformer-based feature extractor, and a small region proposal network. The training data comprises simulated degraded images of space target images against celestial backgrounds, as well as a selection of images from the Dotav2 dataset. Testing results show that the proposed framework outperforms the general framework, achieving a mean Average Precision (mAP) improvement of over 20%.
KEYWORDS: Transmittance, Atmospheric modeling, Infrared radiation, Temperature metrology, Radiometry, Atmospheric corrections, Design and modelling, Thermography, Air temperature, Temperature sensors
Atmospheric transmittance is a key parameter in infrared measurement calibration. The transmittance of the corresponding band is usually obtained based on theoretical calculation. The air based active radiation source was mounted below the airship, and the air transmittance measurement verification test based on the air based active radiation source was carried out. The air transmittance correction could be completed to improve the accuracy of the air transmittance. A space-based active radiation source with a hemispherical shape of 400mm in diameter and a maximum weight of 130kg is designed in this paper. The radiation source temperature range can reach normal temperature to 600℃. The ground verification shows that when the actual temperature of the space-based active radiation source is higher than 155℃, the radiation brightness stability is better than ±2%, and the temperature uniformity is better than ±5℃.
Because optical and radar sensors have their own characteristics and are limited by various external conditions, the target structure and shape information that any one kind of sensors cannot be obtained completely. In this paper, the optical and ISAR imaging methods of space target are analyzed, and the analysis of space target fusion reconstruction is carried out by using optical image and ISAR image of simulation and analog measurement, The research shows that the optical and ISAR imaging have complementary characteristics, and the imaging surfaces of ISAR images are perpendicular to those of optical imaging, The comprehensive recognition results reflect the advantages of optical contour extraction and radar structure judgment.
KEYWORDS: Solar radiation models, Solar radiation, Radiative energy transfer, Sun, Process modeling, Heat flux, Thermal modeling, 3D acquisition, Infrared radiation
Regarding the radiation relationship between complex objects involved in the space environment, in this paper we use discrete coordinate method to calculate and analyze the coupled radiation-conduction heat transfer between complex objects. We simulate the heat conduction process by use of the finite volume method, and the overall temperature field is finally obtained. By comparing the calculation results of the program and Fluent software, the correctness of the coupled radiation-conduction heat transfer program is verified. The result shows that the radiation heat transfer between the targets could affect the temperature field under the conditions of self-emission and ambient radiation. And it also shows that an appropriate reduction of discrete points can reduce the calculation time and will not affect the calculation accuracy.
In this paper, the influences for one LWIR thermal camera in different integrate time are studied by using surrounding temperature simulator and blackbody of independent research and development, which compared to theoretical results. In experiment, the image of camera is obtained by using different integrate time and same temperature of blackbody at surrounding temperature of-30°C, 0°C and 20°C, the result show that the output voltage is linearly proportion to integrate time in those surrounding temperature. The experiment is studied for different blackbody temperature at surrounding temperature of-30°C, the result shows that: the slope of “integrate time vs. DL value” is increased with the target temperature. The noise of output image is increased with the increasing of integrate time. Whose agree with theoretical result. According to the conclusion, the DL value of random integrate time can be derived by known two integrate time DL for one blackbody temperature. And the calibration in random integrate time between two integrate time whose calibration curve are known, which is verified in experiment: the blackbody brightness deviation between test and derivation is less than 1%, which corresponds to blackbody temperature deviation between test and derivation is less than 1°C. The experiment results show that the measurement efficiency can be improved by using appropriate integrate time.
In the practical application of the laser, it is necessary to use the laser beam shaping technology to shape the output beam of laser device to the uniform light intensity distribution. The shaping divergent optical system of compound eye integrator way is composed of beam expanding mirror group and lens array. Its working principle is to expand the output laser to a certain size of caliber, and then divide the beam with lens array into multiple sub beam, where the lens unit of lens array can control the divergence angle of sub beam through the design of focal length, with mutual superposition of the sub beam in far field, to make up for the nonuniformity of beam, so that the radiant exitance on the radiated surface may become uniform. In this paper, we use a reflective microlens array to realize the laser beam shaping. By through of the practical optical path model established, the ray tracing is carried out and the simulation results for single-mode Gaussian beam with noise circumstance is provided. The analysis results show that the laser beam shaping under different inputs can be effectively realized by use of microlens array. All the energy is within the signal window, with a high energy efficiency of more than 90%; The measured surface has a better uniformity, and the uniformity is better than 99.5% at 150m.
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