Abstract:The basic working principle of the uncooled infrared focal plane detector is introduced, and its key technical parameters are summarized. The brief history of the development of uncooled infrared focal plane detector technology and products is reviewed, and the latest progress in related research and product development at home and abroad is reviewed. Finally, the development trend of uncooled infrared focal plane detector technology is discussed.

Abstract:The InAsSb device with nBn structure has many advantages, such as low diffusion current limit, low cost, easy realization of large array, compatibility with existing III-V diode circuit and so on. It is one of the first choices for medium and long wave miniaturized detector with low power consumption, low cost and high resolution detector. In the process of InAsSb epitaxial growth, it is difficult to accurately control the composition of As. In order to find the allowable error range, the influence of As component on the surface morphology, lattice quality and cut-off wavelength of InAsSb material is studied. The experimental results show that under the premise that the epitaxial thickness of the material is less than the critical thickness, the material has a higher tolerance for compressive stress than tensile stress. Controlling the As component within the range of slightly less than 91% can not only ensure the quality of the material, but also slightly increase the response wavelength of the device.

Abstract:The spectral consistency of infrared focal plane detector is one of the important parameters to evaluate the level of material preparation. The detector materials are different because of different preparation processes. Due to the limitations of the speckle size of the spectrometer and the dewar structure of the detector, as well as the huge amount of spectral data collected by the device, it is difficult to test and analyze the detector components. A new method is proposed in this paper. Two detector samples prepared by traditional and optimized process are selected, and multiple light and dark feature regions in the images related to the process are chosen. Then the spectral curves of these regions are tested, analyzed and summarized. And the maximum spectral differences are compared to judge the spectral consistency. The maximum spectral difference of the two materials are 1.21 μm and 0.30 μm. The results show that the spectral consistency of the optimized process is better than that of the traditional process.

Abstract:The frequency of terahertz wave is between infrared ray and microwave, and its unique advantages make terahertz three-dimensional imaging become a research hotspot at home and abroad. In order to extend the optical field imaging technology to terahertz band, the experiments and processing methods of terahertz optical field imaging are introduced. A series of terahertz optical field data with specific viewing angles are collected using a terahertz camera array. Device limitations of the imaging system cause noise in images. Aiming at this problem, discrete cosine transform filtering achieves a good denoising effect and effectively retains the details of the images. Peak signal-to-noise ratio and structural similarity are used to compare various filtering denoising methods, which proves the feasibility of DCT filtering method in terahertz image preprocessing. The digital refocusing of terahertz optical field imaging is realized preliminarily by selecting different depth values to reconstruct images in different depths.

Abstract:Based on the analysis of the requirement of network communication security, the safeguard effect of optical fiber sensing and real-time monitoring technology of fiber optic cable status for network communication security is expounded. Firstly, the development history of optical fiber sensing technology and the representative optical fiber sensors are introduced, then the principle and working mode of distributed optical fiber vibration sensing system are introduced. And the demodulation method of distributed optical fiber vibration sensing system is analyzed. In order to obtain a higher SNR, the effect of delay difference on SNR in the data demodulation is analyzed through experiments. The experimental results show that the delay time is positively correlated with the SNR in a certain range.

Abstract:Due to the vast territory of China, the environmental temperatures in different regions vary greatly. In order to meet the environmental adaptability requirements of the infrared thermal imager for safety monitoring of building engineering, the passive uncooled design mode of refraction and diffraction mixed optics is adopted. Through the reasonable distribution of optical focal degree of the lens with different materials, a miniaturized uncooled infrared imaging optical system is designed, which can work in the range of -55 ~ 70 ℃ and has a field-of-view of 24.1°×19.4°. The operating wavelength range is 8~12 μm, and F number is 1.0.The design results show that the system has simple structure, small volume and good imaging quality. The value of optical modulation transfer function(MTF)at the spatial frequency 42 1p/mm is greater than 0.3, which can meet the application requirements.

Abstract:Aiming at the problem of pesticide residues in vegetables sold in the market, an efficient and nondestructive method for the qualitative classification and identification of pesticide residues in Chinese cabbage is proposed. Three groups of Chinese cabbage leaves and cyhalothrin are used as the research objects. Two groups of Chinese cabbage are sprayed with two different concentrations of pesticides (the ratios of pesticide to water are 1∶500 and 1∶20 respectively), and three types of samples are formed, which contain no pesticides, mild pesticide residues and severe pesticide residues. Three kinds of samples are collected by near infrared spectroscopy, and the spectral data are preprocessed by wavelet soft threshold, then the dimension is reduced by principal component analysis. Fisher decision and K-nearest neighbor classification are performed as well. The experimental results show that the correct identification rate of the two kinds of samples without pesticide residues and with mild pesticide residues is 95%, and that of the samples with mild and severe pesticide residues is 90%, which proves that this method is effective for the qualitative classification and identification of pesticide residues in Chinese cabbage and provides a new way of thinking for the qualitative classification and identification of pesticide residues.