Abstract:According to the in-orbit calibration requirement of a spaceborne infrared imaging system, an online nonuniformity calibration and real-time correction chip system is developed for Infrared Focal Plane Arrays (IRFPA). The system is based on a Field-Programmable Gate Array (FPGA). Because the design of its input signal is standardized, it can be used for on-line nonuniformity calibration and real-time correction of IRFPAs for various infrared imaging systems. Driven by a clock signal, the system operates in a pipeline way. It can acquire calibration images and update the correction coefficient in memory on line while correcting the nonuniform images in real time. It has the advantages of small volume, fast operation, stability, reliability and easy updating. This work has opened up an effective way for the in-orbit nonuniformity calibration of IRFPAs used in spaceborne infrared imaging systems.

Abstract:A circuit structure for studying the use of overdrive technology in pixel units of a resistor array is designed. Compared with the implementation methods of overdrive technologies of foreign countries, this method adopts an open-loop control form. It can remove the steps of closed-loop calculation and table look-up, save system resources and improve the real-time performance of the system. The circuit structure is designed after analyzing the principle of the overdrive technology. It can meet the requirements for studying the thermal response time t1, overdrive factor Kod and dynamic range of temperature of a micro-bridge of the resistor array. In addition, it conforms to the area constraint of a pixel unit. Its Kod is tunable in the range from 1 to 1.5. After simulation and layout design are carried out, the circuit is manufactured in the 0.5 μm process by CSMC foundry. Finally, the function of the circuit is verified by a special test system established. The result shows that the factor Kod of the circuit meets the design requirement.

Abstract:Most of mid-wave and long-wave infrared detectors for space application operate against high background. For a linear HgCdTe infrared detector array, because of the large dark current of itself and the serious nonuniformity of dark current in each of its detection elements, the dynamic range of its output signal is too small and even the signal voltage of part detection elements can not be read out when the conventional readout circuit is used. A readout circuit which has an element-by-element background suppression function is designed for a linear mid-wave infrared detector array. It is designed by combining voltage-current conversion with current storage. This method not only can suppress the dark current from different detection elements, but also can effectively improve the signal-to-noise (SNR) of the circuit and increase the dynamic range of the output signal. The test result show that the circuit has its output swing of 2 V at the low temperature of 90 K and the nonuniformity of its output voltage is reduced by 70%. Therefore, this research is of significance to the engineering design of mid-wave and long-wave infrared detectors.

Abstract:To measure the temperature distribution and image of a high-temperature field, a general design method of a high-temperature measurement system based on infrared detection and photoelectric conversion techniques is proposed. The selection and design of hardware and the development of processing and control software for the system are completed. The image data of a high-temperature field collected by the system are converted by both a serial Ethernet converter and optical terminals. Then, they are transferred remotely for processing. Finally, a computer for image data processing sends control commands for controlling the parameters and operation of the image collection unit through optical terminals. This measurement system is used in a particular test successfully and the instantaneous temperature distribution of a temperature field is obtained remotely. The validity and practicability of this infrared high-temperature measurement system are verified by the experimental result.

Abstract:The overlap region of the parallel light beams in a space is analyzed when a dynamic precision target is running. The region is considered to be a cusiform cone region which can be defined accurately. When a dynamic precision target is used to test an optoelectronic device, it only needs to let the azimuthal pitch visual axis intersection point of the device to be tested be in this region. The dynamic precision target is used to test the angle and tracking accuracy of a given optoelectronic device in different positions in the region for many times. The maximum standard deviation and mean deviation of the test data obtained are much less than the corresponding specifications of the given device. The test result shows that as long as the azimuthal pitch visual axis intersection point of the device to be tested is in the above region, the test error due to the position deviation of the device to be tested is extremely limited. The test result has low discrete degree and good repeatability. It can meet the requirements for practical application. The verification test validates the definition of the fusiform cone. It shows that this definition can be taken as the theoretical basis for judging whether the device to be tested is in alignment with the rotating target during test.

Abstract:The extraction of navigation stars is a critical step in near-infrared celestial navigation. It is related to the subsequent star target identification and star image matching directly. Because of the strong background of the sky, the extraction of star targets is extremely difficult. If the near-infrared celestial navigation is used to detect stars in the near-infrared waveband, enough star targets for navigation can be acquired even in the daytime. On the basis of analysis of the characteristics of near-infrared star images, an energy projection method is introduced and the potential star targets and noises are located according to the peak point of the projection. Then, the areas to be processed are set up according to the energy variation. The targets and noise points are extracted quickly by suing the OTSU algorithm. Finally, after the multi-frame overlay is used to remove the noise points, the star targets are extracted. The experimental result shows that this algorithm is simple in calculation, short in operation time and higher in detection ratio. It can detect the star targets against a complex background effectively with a low false alarm rate.

Abstract:To address the problems such as low efficiency and repeated calculation in multi-threshold selection for the traditional multi-threshold infrared image segmentation, a fast multi-threshold infrared image segmentation algorithm based on an improved artificial bee colony algorithm is proposed. First, the artificial bee colony algorithm is introduced in threshold selection to implement multi-threshold segmentation. Then, to overcome the shortcomings existed in the original artificial bee colony algorithm, such as low convergence speed and being easy to fall into local optimum, an improvement is made in the search by leaders, followers and scouts. The improved algorithm is faster and can converge to the optimal solution more accurately. The experimental result shows that compared with the original artificial bee colony algorithm, this improved algorithm is faster for the same accuracy and its result is closer to the optimal solution for the same iterative times. It can implement multi-threshold segmentation of infrared images very efficiently while keeping its accuracy. It is a feasible segmentation method of infrared images.

Abstract:A modified reconfigurable super-resolution algorithm for infrared images is put forward on the basis of study and analysis of the Projection Onto Convex Sets (POCS) algorithm. The modified algorithm makes full use of the determination model in the spatial domain and implements registration by smoothing noise reduction processing after motion estimation. Because the Point Spread Function (PSF) is modified while the details of digital images are highlighted, reconfigurable high resolution images with optimal quality are obtained by inhibiting the margin Gibbs phenomenon. The quality of the reconfigured infrared image is evaluated quantitatively. The result shows that the expected result is obtained in image quality. This technology is of important application value to infrared target recognition and tracking, infrared reconnaissance and anti-reconnaissance, study of characteristics of infrared ships, processing of high-definition digital images, ripping of old video and extraction and recognition of biological information.

Abstract:The different surface mucus from human normal and cancerous intestinal tissues were investigated by terahertz time-domain spectroscopy technique and the absorption coefficient and refractive index were obtained in the range from 0.2 to 0.8 THz. The study found that the terahertz absorption intensity of fresh normal mucus is close to water, which indicating that the water in fresh tissue occupies the main contribution. The cancerous samples showed higher absorption coefficient and refractive index than that of the normal samples. It suggests that terahertz spectroscopy possesses the capability of identifying the cancerous tissue which has great potential application prospect in biological detection and tumor disease diagnosis.