In the process of point target detection, the blind pixel can easily lead to wrong detection of point target. Aiming at the defect that the conventional blind pixel detection method cannot detect the random blind pixel dynamically, a blind pixel dynamic detection method for IRFPA towards point target was proposed. In this method, the suspicious point targets which are removed by the multi-frame detection of point targets are chosen as potential blind pixels. Blind pixel feature model is used to match potential blind pixels, and the likelihood function of the confirmed blind pixel is characterized by multi-frame accumulation. In the subsequent detection, the blind pixels are dynamically detected by using the blind pixel likelihood function which is iteratively updated by the detection result, so as to adaptively detect blind pixel. The results showed that this method can dynamically eliminate random blind pixel and fixed blind pixel without interrupting the detection process of the point target, and at the same time improve the detection accuracy of the point target with a small amount of computation and is easy to be implemented by hardware.
When the target to be measured temperature is far away, and the prior information of the target such as the emissivity of the detected object can not be known, the traditional infrared single-band temperature measurement method will produce larger temperature measurement error. According to the characteristics of target infrared radiation spectrum, assuming that the target is grey body, this paper uses infrared dual-band temperature measurement algorithm and Monte Carlo method to extract the temperature feature of the object under test. The effectiveness of the algorithm is analyzed. The influence of parameters such as iteration times of the algorithm and the minimum error threshold of dual-band radiation ratio on the accuracy of target temperature inversion is simulated and analyzed. On this basis, the influence of different target emissivity, distance between wavebands and detection distance on target temperature inversion accuracy is analyzed. The results show that the two-band temperature measurement algorithm can extract the target temperature information quickly and accurately under the set parameters, and the temperature inversion error is related to the distance between infrared bands. This provides guidance for improving the accuracy of target temperature measurement in practical measurement.
Targets detection in single band images has problems such as poor clutter suppression capability and high false alarm rate, while the difference in imaging characteristics of the aerial target between the mid-length wave and the long-length wave is obvious and complementary, so dual-bands fusion can be utilized to improve detection efficiency and performance. An rapid infrared dual-band fusion target detection method based on local contrast method (LCM) is proposed, searching targets rapidly and extracting targets features in the mid-length wave images from same scene, finally fusing two bands images for precise positioning. The multi-scales LCM is used to quickly perform full-image range background suppression and target enhancement in lower-resolution long-length wave images, then the suspicious target position is obtained and sliced. Following the guidance from the long-length wave images, the position of targets is extracted at the corresponding position in the higher-resolution mid-length wave image. Two positions from different resolution images are fused, and the target is accurately positioned. This method achieves rapid detection of aerial targets in infrared images effectively, which has certain engineering application value.
With the continuous occurrence of aircraft crash, it is very important to realize the detection of aerial targets on the spaced-based platform. Many countries have carried out some researches in this field, but there is still no good conclusion about the methods and systems for aerial target detection. Meanwhile, the actual cost of satellite experiments is very expensive, and it is impractical to test the detection system by launching satellites several times. Therefore, the system simulation model can be used as the basis for the design of detection system. In the simulation process, combined with the optical system parameters and detector indicators, the imaging relationship between the satellite platform, the turntable and the target are calculated, and various imaging modes such as scanning and gazing are obtained according to the specific parameters of the actual application. This simulation mode directly presents the actual satellite motion, camera imaging and target motion state. And such a simulation system greatly shortens the actual design time of the system in engineering applications. It more realistically inverts the actual operating state and can obtain the detection result without the actual satellite launch. And such a simulation system can flexibly change parameters according to the actual conditions, so it can not only be applied to aerial targets detection, but also play an important role in other fields.
This paper reports the development of 2000×256 format SWIR HgCdTe/Si FPA with multiple-choice gain (i.e. multiple-choice charge handling capacity) for hyperspectral detection. The spectral resolution is about 8nm. To meet the demands of variable low flux detection within each spectral band in the short wave infrared range, low dark current, low noise, variable conversion gains and high SNR (Signal to Noise Ratio) of FPA are needed. In this paper, we fabricate 512×512 pixel 30μm pitch SWIR HgCdTe diode array on Si by using a novel stress-release construction of HgCdTe chip on Si. Moreover, we design low noise, variable conversion gain and large dynamic range read-out integrated circuit (ROIC) and hybridized the ROIC on the HgCdTe diode array on Si substrate. There are 8-choice gains which can be selected locally according to the incident flux to meet high SNR detection demand. By high-accuracy splicing 4 512×512 HgCdTe/Si FPA we get mosaic 2000×512 FPA, and characterizations have been carried out and reveal that the array dark current densities on an order of 10<sup>-10</sup>A/cm<sup>2</sup>, quantum efficiency exceeding 70%, and the operability of 99.5% at operating temperature of around 110K. The SNR of this FPA achieved 120 when illuminated under 5×10<sup>4</sup>photons/pixel.
For the prospects of three-dimensional reconstruction technology based on structure from motion in engineering application, a high-resolution and visible band imaging system has been designed and implemented. It consists of a 5k × 5k CMOS focal plane array detector made by the ON-SEMI company, an optical system and an electronics system designed by ourselves. The electronics system takes FPGA as the control and drive processor chip and is divided into three parts: a power management module, a detector module and an image processing module, capable of finishing image compression and transmission. A sequence of images for the target of long distance away is obtained from the imaging system and the images after cropping and segmentation, aiming at reducing calculation and excluding some points irrelevant with the target during reconstruction process, are took as input of structure from motion. Seeds from the match points expand from sparse points to dense points and the initial model of reconstruction target is achieved. The experiment results show that the imaging system meet the requirement of three-dimensional reconstruction in engineering application and a new novel imaging system design of graded resolution based on bionics is proposed.
The free-electron relaxation time is a crucial property to be considered in the design of optical devices, because it determines the dielectric function. Thus, an accurate understanding of this relaxation time is essential for design optimization. Some simulations showed that the relaxation times of Au thin films with thicknesses below 30 nm are different from those of the bulk material. Therefore, we deposited films with four different thicknesses below this value and used near-infrared spectroscopic ellipsometry to show that the relaxation time is dependent on the film thickness. We fitted the ellipsometry spectrum of Au thin films with a thickness <30 nm and found the imaginary part of the dielectric function of the thin films to vary with the film thickness in the near-infrared region. Furthermore, different relaxation times were used to simulate the reflectance of a Fabry–Pérot absorber and a plasmonic metamaterial absorber. The simulation results indicated that the obtained relaxation time enables a more reliable evaluation of optical device design.
An all-fiber multi-pass phase modulator for chirped pulse amplification centered at 1053nm is demonstrated. An optical pulse with a 3-dB bandwidth of 2.23nm centered at 1053 nm is obtained based on the system. And spectrum with negative dispersion is obtain by an all-fiber architecture which can be used for ultrashort laser source in ps.