Abstract:To solve the dynamic range limitation of an Uncooled Infrared Focal Plane Array (UIRFPA) for imaging multiple targets, a method which can adjust dynamic range according to the target is proposed on the basis of the characteristics of the detector. Before integration, the capacitance is adjusted in real time according to the grayscale distribution of the selected target in an initial image. At the same time, the pixel bias is configured point by point to adapt the dynamic range and Non-Uniformity Correction (NUC) is conducted. Then, the best imaging effect of the locality of the target is achieved successively. Finally, an infrared imaging system for verifying the feasibility of the method is built. The results show that the proposed method can realize the real-time adjustment of dynamic range and obtain clear local key target images. Because the problem of mismatch between dynamic range and target is solved, it is of great significance to the application of uncooled infrared imaging system in multi-target scenario.

Abstract:The infrared radiation characteristics of a high-speed vehicle plume are of great importance to the infrared detection, identification and tracking of a target. To analyze the infrared radiation characteristics of the plume, the flow field of the plume is first partitioned according to the empirical formula. Then, the spectral absorption coefficient and transmittance in the band are calculated by using a narrowband model. For the non-uniform hot gas, in view of the Collided-broaden effects and the Doppler-broaden effects, the infrared radiation intensity of a high-speed aircraft plume in the wave band from 2 to 5 μm is computed by using a C-G band transmission model. Finally, the infrared radiation characteristics of a plume containing different components are calculated and the influence of composition distribution on the infrared radiation characteristics of the plume is analyzed. At the same time, the influence of atmospheric transmission on the infrared radiation characteristics of the plume is analyzed. This study is of referential value to the selection of detection bands.

Abstract:A high precision, high linearity, light and small module for measuring time of flight of laser pulses is designed. Because the TDC7201 chip has advantages in time measurement, it is used as the core for time measurement. The STM32F103RET6 microcontroller is used as the main control chip for controlling the whole module. The experimental results show that the module has its time measurement accuracy up to 4.1 ps in the time interval range from 12 ns to 100 μs. The linear fitting correlation coefficient of the measurement result is 1. It can measure the time intervals between the main laser pulse and five echoes. This module can meet the practical application requirements of high precision, high linearity, multi-echo and lightweight of the pulsed laser ranging systems based on SiPM.

Abstract:Infrared optical films are usually fabricated at higher temperatures. When they are used at low temperatures, the thermos elastic stress generated may significantly affect their spectral performance and reliability. According to the traditional bridge bending theory and the displacement coordination condition, the horizontal strain, bending strain and thermal stress distribution in multilayer films are analyzed. On the basis of detail derivation, the simplified calculation formulas of thermal stress in multilayer films are derived when the thickness of the film is much smaller than that of the substrate. Taking the long-wave infrared narrow-band filter as an example, the numerical value and distribution of thermal stress in multilayer films are analyzed.

Abstract:Aiming at the precooling of the pulse tube of a U-type hybrid cryocooler with a one-stage Stirling and a two-stage pulse tube, the influence factors on the cryocooler are studied. When the cooling temperature of the second stage is 30 K, the first stage cold finger is connected to the pulse tube via a heat bridge and the cooling capacity provided by the first stage is used to precool the pulse tube. The influence of pulse tube precooling on the temperature field and velocity field in the pulse tube is studied by a Fluent software. It is found that precooling may change the internal temperature distribution of the pulse tube and has a great influence on the cooling capacity of the second stage. Without the precooling of the pulse tube by the cooling capacity provided by the first stage, the cryocooler outputs its cooling capacity with its second stage of 0.7 W@30 K and its first stage of 7 W@80 K at the same time and the input PV power of the compressor is 133 W. After the first stage cold heat exchanger is connected to the middle part of the second stage vessel via a heat bridge, the input PV power of 133 W is maintained and the output cooling capacity of the second stage and that of the first stage are changed to 1.2 W@ 30 K and 6 W@ 80 K respectively at the same time. It is found that the precooling of the middle section of the pulse tube can greatly improve the two-stage cooling capacity of the U-type hybrid cryocooler.

Abstract:Volumetric 3D display is a technology for displaying stereoscopic graph in space. The technology is presented in brief. The spatial coordinate transformation problem in it is discussed. By approximating and inducing the actual problems existed, the corresponding geometric optical problems are obtained. Then, they are solved in detail and the relative parameters for experimental measurement are designed. Finally, relative algorithms are designed according to the solutions and the corresponding experiment is carried out. The result shows that the correctness and effectiveness are verified.

Abstract:The study of infrared radiation properties of military targets is important for the evaluation of IR detection range. The limitation and defect of the IR property inversion method based on infrared images when it is used to inverse the properties of point targets are analyzed. According to the principle of radiation measurement, the mathematical relationships among the radiance, pixel grey value and radiation intensity are deduced by extracting the point target in an IR image. A new algorithm for inversing the IR radiation properties of a helicopter in point target detection is proposed and is used to inverse the infrared radiation intensity of a certain military helicopter. The radiation intensity distribution of the helicopter at different observational angles in the waveband of 3 to 5 μm is calculated. The results show that the algorithm can implement the inversion of IR radiation properties of small targets in far distance. It is of significance to the evaluation of infrared radiation detection range of IR reconnaissance systems.

Abstract:The pedestrian detection technology based on infrared images has played an important role in night surveillance, night-time driver assistance and other areas. However, because of low resolution and high signal-to-noise ratio, most of the existing infrared pedestrian detection methods have poor performance. An alternative infrared pedestrian detection algorithm based on image feature channels is proposed. In the method, fast feature pyramids are used to implement sliding window detection in infrared images. The results show that compared with other conventional algorithms, this algorithm is improved greatly in real-time performance and robustness.