Abstract:The operation range is one of the important parameters for describing the whole performance of a military infrared imaging system. It can be divided into detection range, recognition range and identification range among which the detection range is the maximum one. According to the geometric relationships among the infrared imaging system, the earth surface and the target, a method for calculating the operation range of an earth observation infrared imaging system based on MATLAB is presented. The value of the operation range is determined by the altitude of the infrared imaging system, the radius of the earth and the height of the target. The actual detection range of an infrared imaging system or the operation range proposed for a system to be developed should not be greater than this value.

Abstract:Laser imaging guidance is one of the development directions of precision guidance. A laser imaging guidance detector is the key component for a laser imaging system. The research progress of laser imaging guidance detectors including HgCdTe focal plane arrays, Si Avalanche Photodiode (APD) focal plane arrays and InGaAs PIN detector and APD focal plane arrays are presented. Among them, the InGaAs APD focal plane arrays will become the main development direction for laser imaging guidance detectors. Their key technologies include growth of epitaxial materials, fabrication of high uniformity detectors and design of readout circuits.

Abstract:A continuous zoom infrared imaging system with a large zoom ratio can be used for target searching in a large field of view and for high precision tracking in a small field of view at the same time. Because of the large zoom ratio, to keep good imaging quality throughout the zoom range becomes the difficulty for design and validation. To solve this problem, the Modulation Transfer Function (MTF) is used to measure and validate the variation of the zoom image plane. There are two main methods for measuring the MTF of an infrared imaging system: a slit method and a sloping edge method. After analysis and comparison of the characteristics and influence factors of both methods, the sloping edge method is chosen. By using the MTF to calibrate the defocus curve of the existing test sample with a large zoom ratio at each focal length, the optimal image plane position is obtained. Compared with the theoretical design value, its maximum deviation is 36 μm. The focusing compensation is modified according to the data. Finally, the maximum deviation is reduced to 5 μm.

Abstract:Submillimeter wave is absorbed in atmosphere seriously. So it is very difficult to detect a metal target in lower atmosphere passively. A method for detecting a metal target by a 360 GHz radiometer at high altitude is proposed. The configuration of the radiometer is presented. The contrast of the atmospheric radiation temperature to the antenna temperature of the target is calculated by using a MPM model. The radiometer is calibrated under the weather condition with the ground temperature of 0℃ and the humidity of 20% and is used to detect a 0.5 m×1 m metal target at the altitude of 3 m above the ground. The calculation and experimental results show that the model for calculating antenna temperature contrast is feasible. Under the weather condition with the ground temperature of 20℃ and the relative humidity of 20%, the 360 GHz radiometer at the altitude of 5 km can detect a 1 m×5 m metal target in the distance of 0.3 km above it and can detect a 10 m×20 m metal target in the distance of 2 km above it.

Abstract:An optimization method for designing a light-weight point mirror for a space camera is proposed. The light-weight design of a point mirror with a size of 360 mm×560 mm for a space camera is carried out. It is optimized by taking the mirror thickness, tip angle, face-sheet thickness, and rib-sheet thickness as design variables, by taking the minimum weight as the design objective, by using the figure peak value less than 55 nm and the root-mean-square value less than 11 nm as restraint conditions and by reducing the weight of the whole mirror from 4 kg to 1.72 kg (its face density is 8.0 kg/m2). Then, taking the minimum figure under the condition of microgravity as the objective, the supporting points of the designed light-weight mirror are optimized. The resulting figure peak value is 54 nm. The deformation and modality of the mirror under the condition of microgravity, rotation inertia and temperature change are calculated and verified by using a finite-element analysis method. All of the results meet the requirements for space application. Finally, the effect of the deformation due to the synthetic action of the space environment on the image quality of the optical system is analyzed by using an opto-mechanical-thermal integrated simulation method. The result shows that because of the deformation of the pointing mirror, the modulated transfer function of the optical remote sensing system is reduced from 0.735 to 0.703 with a reduction ratio of 4.4%, which meets the design requirement.

Abstract:For the optical design result of a certain space camera, several frameworks in different structural forms are designed and selected according to the machining features of different materials. The resonant frequency of each framework is analyzed by using a finite element method and the economics of each framework is also analyzed. Finally, the structural form is determined for the framework. The selected framework structure is a full-truss one. It has a weight of 57 kg and a first-order resonance frequency of 90.4 Hz. The mechanical test of the framework components shows that the framework has its first-order resonance frequency of 88.7 Hz. The analysis and test results show that it meets the design requirement.

Abstract:To achieve long distance fiber energy transmission and laser conversion, various factors which have influence on the transmission efficiency of a system in the process of energy transmission, such as fiber loss, wavelength selection, matching of photoelectric materials, are analyzed. A photovoltaic conversion chip is designed by growing a InGaAs PIN structure on a semi-insulating InP substrate epitaxially. The structure and interconnect technology of the chip are optimized. Finally, a highly efficient laser energy converter is developed successfully. The test result shows that the laser energy converter has its photoelectric energy conversion efficiency of 28% under the laser illumination at 1550 nm wavelength.

Abstract:Taking the red Fuji apples produced in Shandong and Shanxi Provinces as the experimental objects, a classification method for identifying the apples produced in different regions is proposed. Firstly, the near infrared (NIR) spectra of the apples are preprocessed by a wavelet soft-threshold method, removing the noise and redundancy. Then, a Principal Component Analysis (PCA) method is used to reduce the dimension of the NIR data. Secondly, a Fisher Discriminant Analysis (FDA) method is used to further extract the features from the data. Finally, a K_near Neighbor Classification (KNN) method is used for the classification and identification of the apples. The experimental result shows that the proposed method can well realize the nondestructive, fast and accurate classification and identification of the apples produced in different regions. Its identification accuracy is up to 97.5%.