The latest research progress of HgCdTe very-long-wavelength infrared focal plane detectors in North China Research Institute of Electro-Optics is reported. The p-on-n heterojunction materials are grown using horizontal liquid phase epitaxy with In doping and vertical liquid phase epitaxy with As doping. Based on wet etching, surface and side passivation, and In bump interconnection process, the first mesa-type HgCdTe very-long-wavelength infrared focal plane device is prepared. At an operating temperature of 60 K, the device has a cut-off wavelength of 14.28 m, an operability of 94.5%, and an average peak detection rate of 8.98×1010 cm·Hz1/2·W -1.
In the aspect of solid-liquid interface control, there are many studies on mature semiconductors such as Si, but few studies on indium antimonide(InSb)materials. The effects of crystal pulling speed, rotation speed and crucible rotation speed on the shape of the solid-liquid interface during the growth of the InSb crystal in equal diameter segment were simulated and the actual crystal growth experiment was carried out. The results show that these three growth parameters have a certain effect on the smooth control of the solid-liquid interface shape. A stable solid-liquid interface control method is obtained, which lays the foundation for subsequent InSb materials with lower dislocation density and more uniform radial electrical parameter distribution.
Aiming at the requirements of terahertz radiation power compatibility test for free space and waveguide transmission, a multi-function terahertz pyroelectric detector with a photosensitive surface diameter of 10 mm is studied. By means of the finite element analysis and the thermoelectric coupling simulation design, the model of terahertz pyroelectric detector, whose sensitive element is composed of the LiTaO3 wafer with the thickness of 100 m and the carbon nanotubes absorption layer, is established; the process problem of using the large wafer and multi-array method to manufacture the sensitive components of LiTaO3-based terahertz pyroelectric detector is solved, and the development of terahertz pyroelectric detector is completed by using key processes such as optimized precise thinning, polishing and Lift-Off. Under the setting conditions, the responsivity of the terahertz pyroelectric detector is 371.8 V/W, and the noise equivalent power is 0.34 nW/Hz1/2. The experimental results show that the designed and manufactured terahertz pyroelectric detector has high integration, good responsivity and low noise equivalent power, which can effectively solve the power test problem of terahertz beams with large light spots.
The complex refractive index of materials is an indispensable physical parameter for calculating the degree of polarization. Since it is relatively difficult to measure the complex refractive index directly, the polarized reflectivity expression of the materials is derived， and an inversion method of surface parameters is proposed when the incident light is linearly polarized based on the existing polarized bidirectional reflectance distribution function of rough surfaces, which can improve the applicability of the complex refractive index calculation. The comparison between the inversion results and the reference values indicates that the inversion method has good reliability.
In the industrial production, high temperature steam pipelines are usually used to transport high temperature steam and high temperature industrial waste water, etc. But the pipelines are often placed in complex environments for safety, which is not conducive to the inspection and maintenance of pipelines for the workers. How to quickly locate the location of the steam pipeline in the complex background and distinguish the surrounding environment has become an urgent problem to be solved. Because the Otsu algorithm cannot meet the requirements mentioned above, an improved Otsu algorithm is proposed based on the cellular immunity mechanism. According to the characteristics of the pipelines and the complex background in the infrared images, the algorithm calculates two different thresholds which can be used to extract the pipelines and distinguish the complex background. With the help of the Quartus Ⅱ software， a hardware and software system based on FPGA has been built to realize the data communication and transmission, and the improved Otsu algorithm has been verified. The experimental results show that the algorithm can be applied to the infrared images of the pipelines to obtain better effect. Compared with several edge detection operators and the classical Otsu algorithm, the improved algorithm has a higher true positive rate (TPR) and a lower false positive rate (FPR), both for the pipelines extraction and the complex background distinction.
Due to the defect of the detector′s principle, the images taken by the infrared thermal imager have low contrast and unobvious details. Contrast limited adaptive histogram equalization(CLAHE)can enhance the contrast of infrared images. But the parameters need to be adjusted manually since they cannot adapt to different scenes. As an intelligent swarm optimization method, cuckoo search algorithm has a strong ability to search for optimal solutions. In this paper, the cuckoo search algorithm is used to obtain the optimal parameters of CLAHE algorithm in different scenes, and the contrast of infrared images can be adaptive enhanced. The experimental analysis shows that the improved algorithm is feasible and adaptable.
The high spatial and temporal resolution of geostationary satellite has significant advantages in monitoring and forecasting disastrous weather with high impact. A typhoon precipitation retrieval study based on infrared spectrum bright temperatures of the advanced geosynchronous radiation imager (AGRI) in FY-4A satellite is conducted. The influences on precipitation retrieval accuracy of different distance measurements of K-nearest neighbor (KNN) in the inverse problem of regularization method are discussed. The precipitation retrieval consists of two steps: （1） the identification of precipitation field of view, which uses KNN to identify the “precipitation” and “non-precipitation” signals of brightness temperatures to be retrieved mainly based on the training dictionary samples；（2） the retrieval of the precipitation field of view, which uses inverse problem of regularization method to retrieve the infrared brightness temperatures precipitation on the basis of identifying the precipitation field of view. KNN distance measurement adopts Euclidean, normalized Euclidean, Mahalanobis and Cityblock respectively. Taking typhoon “Ampil (2018)”as an example, the precipitation retrieval experiment is carried out. The experiment shows that the retrieval result has a high similarity with GPM, and different distance measurements have their own advantages in the retrieval of "extreme precipitation".