Abstract:According to the demand of imaging spectrometers for mini satellite platforms, an imaging spectrometer based on a linear variable filter is designed. By using the linear variable filter as a light splitter, the miniaturization of system structure, the reduction of development period and cost and the improvement of spatial resolution, signal-to-noise ratio and reliability can be realized. Because the method is suitable for micro/nano satellite platforms, it has a good application prospect. According to the overall design, the related specifications are determined, analyzed and calculated. On this basis, the parameters of the optical system and the splitter system are designed. Finally, the overall signal-to-noise ratio of the system is analyzed. The results show that the system has good imaging performance and can meet the observation requirement. Thus, the expected design purpose is achieved. The theoretical basis is provided for the implementation of the system in next step.

Abstract:An infrared horizon sensor is one of the important equipment of a satellite attitude control system. And yet, an infrared thermistor detector is the key unit of the infrared horizon sensor. Its quality is directly related to the performance and reliability of the infrared horizon sensor. With the continuous development of modern space technology, the next generation of infrared horizon sensors have an urgent demand for high-reliability long linear array infrared thermistor detectors. In recent years, researchers have made a great breakthrough in synthesizing Mn-Co-Ni-O (MCN) thin films by a novel chemical solution deposition (CSD) method. Since the compactness of MCN films is much better than that of sintering ceramic materials, it is possible to use it to fabricate long life and high-reliability infrared thermistor detectors. In addition, the similarity between the fabrication technology of MCN thin film detectors and that of microelectronic devices has provided the basis of fabricating long linear thermistor detector arrays. High quality MCN thin film infrared thermistor detectors are fabricated by microelectronic processes. Some key processes such as etching and annealing are studied. These new technologies and methods are of significance both to the application of thin film infrared thermistor detectors in the fields of space observation and remote sensing of our country and to the improvement of reliability and lifetime of horizon sensors.

Abstract:Passive millimeter wave imaging is an important development direction in the field of public security. Nowadays, the researchers at home and abroad mainly concentrate their efforts in the reflex systems with focal plane arrays. This will result in a high development cost. Moreover, the fabrication of large diameter off-axis paraboloidal mirrors is more difficult. By combining geometrical optics with Gaussian beams, a quasi-optical system suitable for near field passive millimeter wave imaging is designed and developed on the basis of a millimeter wave lens. The system has a detection range of 1.5 m, an imaging area of 1.2 m×1.2 m and a spatial resolution better than 3 cm. Because the system can implement non-contact security inspection, it has a wide application prospect in various public inspection places.

Abstract:With the continuous development of InSb infrared detectors, the pixel number increases and the line-width decreases continuously. When an epitaxial process is used to grow substrates, the requirement of the surface state of InSb wafers is becoming higher and higher. The surface state parameters and their related measurement methods are discussed mainly. Some related standards and the attention of the manufactures and research organizations at home and abroad to the surface state parameters are listed. The direction is found for next step research. This research has laid the basis for the production of larger format focal plane arrays, the improvement of the stability of detector performance and the provision of high-quality substrates for epitaxial growth.

Abstract:The requirement of the large aspect-ratio rectangular plane mirror for a certain space remote sensor is that its weight should be reduced as much as possible and its surface deformation error (RMS) should be less than λ/50 (λ=632.8 nm) at the operation temperature of 20±5℃. The material selection of the mirror and its supporting structure is presented. The weight reduction and supporting modes of the mirror are analyzed. According to the shape features of the mirror, the local width of the back of the mirror is increased and the backside of the mirror is designed to have three supporting points. Through finite element analysis, the mirror and its flexible supporting structure are optimized and determined. The analysis results show that the displacement and surface deformation of the mirror meet the design requirements. Finally, the dynamic characteristics of a simulated mirror assembly is tested in a mechanical environment experiment. It is shown that the structure of the mirror meets the design requirements.

Abstract:The figure shape precision of primary mirrors are most important for the imaging quality of space cameras. To ensure a space camera to have high imaging quality in a wide temperature range (20±10℃), a flexible support structure is designed. Firstly, the SiC material is selected to make the mirror and semi-enclosed type light-weight processing is carried out for the back of the primary mirror body. Secondly, for the environment in the temperature range of 20±10℃ in which the round primary mirror module with an aperture of 550 mm will be used, a flexible articulated structure is designed. Because the parameters of the supporting structure are optimized by the Matlab software, the flexible supporting structure has enough radial flexibility and can absorb distortion so as to reduce the stress of the mirror. The finite element analysis result shows that the supporting structure has the first-order frequency of 267 Hz which is much higher than the inherent frequency of the mirror body module. So, it can ensure the primary module not to be damaged. Even when the gravitation is coupled with the temperature load of 10℃, the mirror can meet the requirement of the figure shape error (RMS) less than λ/40 of the optical system.

Abstract:Automatic light adjusting techniques are critical in optical imaging systems. To improve the imaging quality of an optical imaging system, an automatic light adjusting method is put forward. The method is based on the iris with a potentiometer and uses external trigger pulses to set shutter speed. Compared with the light adjusting method which sets shutter speed by using stop alone or by internal synchronization, the closed-loop control of iris and the continuous adjustment of shutter can be realized by using this method. For the hardware, because the DSP in TMS320C28X series is used as the main processing chip, its clock cycle is up to 6.67 ns. With the built-in flash and rich peripherals, the driving pulse for iris motor, the AD conversion of potentiometer, the compilation and the C language programming can be realized. For the software, the light adjusting cycle of 20 ms is used and the flow chart of automatic light adjusting is given. It is verified that this automatic light adjusting method has the features of large dynamic light adjusting range, high reliability, fast response and wide applicability. It can meet the needs of automatic light adjusting in the project.

Abstract:Xihu longjing tea from different producing regions has different quality. Near-infrared spectroscopy, spectral pretreatment, principal component analysis and discriminant model are used to discriminate Xihu longjing tea from Longjing village, Meijiawu village and Geya village. The results show that the second derivative pretreatment method is most effective for the removal of the noise in near infrared spectra and the Bayes discriminant analysis is the best discriminant model for the tea from the above three regions. Setting the components as 5 in the Bayes model, the best original discriminant rate and the cross-validation discriminant rate are 100% and 82.35% respectively. In the cross-validation, the discriminant accuracies of the tea from Longjing village, Meijiawu village and Geya village are 80%, 83.33% and 83.33% respectively. Therefore, the model can be used to discriminate Xihu longjing tea from Longjing village, Meijiawu village and Geya village and can provide the theoretical basis for the producing region discrimination of Xihu longjing tea.