The color information in the true color low light level night vision image is the true restoration of the visible light color information reflected by the scene itself. Compared with the gray-scale level image and the false color image, it can obtain more abundant image information, which is more in line with the observation habit of the human eye and reduce the fatigue of the human eye. Under the background of information war, aiming at the multi-functional, all-weather, information sharing and transmission characteristics of new type of low light level equipment for single soldier, the requirements of digitalization, high integration and low power consumption are put forward for the true color low light level night vision technology. In this paper, the research progress of real color digital night vision technology is reviewed: firstly, the classification of color night vision technology is introduced; then, the foreign true color digital night vision products represented by French photonis company, Japanese komamura company and American SPI Infrared company are summarized, included the technology route and development level of the true color digital night vision technology; finally, three issues that need to be considered in the realization of low light level night vision true color technology are proposed.
In this paper, we introduce a novel nonuniformity correction (NUC) algorithm for infrared focal-plane array (IRFPA). It is based on layers technique. First, the Rolling Guidance Filter (RGF) is utilized to decompose the raw IR image into a low frequency part and a high frequency part. Then, an adaptive temporal high-pass filter is utilized to filter the high frequency part by making use of the gradient and amplitude of it to estimate the Fixed Pattern Noise (FPN). The proposed scheme use the frames with large displacement to estimate the FPN to alleviate the ghosting artifacts in case of scene moves slowly. At Last, the estimated FPN is subtracted from the pristine image to obtain the correct result. Experiments with synthetic and real IR video demonstrate that the proposed method has better NUC performance and less artifacts than the state-of-the-arts.
Fixed pattern noise (FPN) in infrared images seriously degrades the imaging quality and visual effect of infrared focal plane arrays (FPAs). Although many scene-based non-uniformity correction (NUC) algorithms have been developed recent years, the convergence speed of the bias and gain correction parameters still need to be further improved. In this paper, we present a novel NUC approach for IR FPAs which minimizes the total variation of the estimated IR irradiance guided by a noise model image, and we name it guided total variation (GTV) NUC method. A temporal detection factor is introduced to NUC procedure to prevent NU parameters updating when scene movement stops. In the proposed scheme, the correction parameters of the FPN are estimated via an iterative optimization strategy, frame by frame. The experimental results of synthetic and real IR videos demonstrate that the proposed algorithm have better NUC performance in terms of fewer ghosting artifacts and faster convergence than the state-of-the-art methods.
As the rapid development of back-illuminated CMOS (BI-CMOS) image sensor technology in recent years, its application prospect in the field of Low-Light-Level (LLL) night vision has been widely concerned. Therefore, LLL imaging module was developed based on BICMOS, whose 3-D noise data was obtained under different illumination conditions. The test results show that, the signal-to-noise ratio (SNR) of imaging module becomes worse with the decreasing of illumination. According to the judgement of noise, the noise power of the image in low illumination is mainly Gaussian distribution. And the image processed by spatial filtering, which efficiently reducing the imaging noise and improving the imaging quality.
Apparent distance is a reflection of the performance of low-light night vision system, but also an important parameter indicator in the design stage of LLL night vision system. As the working environment is changing, it is difficult to accurately estimate the apparent distance. Except the parameters of the system itself and the series of parameters caused by the weather environment, the contrast of the target and background is also the important factor to affect performance of the system. In this paper, we use ICCD to test the contrast of target and background of several typical scenes in the use of low-light night vision system, and get the contrast of target and background, which is very important to the prediction of apparent distance.
Vacuum technology is extensively used in space science, nuclear energy, surface science, materials science, electric vacuum industry, microelectronics, semiconductor, metallurgy, and so on. More and more fields need ultra high vacuum (UHV) or extreme high vacuum (XHV) for scientific research and production. Both the rigorous vacuum processing technics and highly developed sophisticated vacuum technology are the necessities for the acquisition and conservation of UHV or XHV ambience. In this paper, a vacuum decline was analyzed and the UHV system was recovered. Using the residual gas analyzer to measure the partial pressure of residual gas and identify the type of gas, the outgassing source was found out by comparing the measure results. The UHV system was recovered back to 10-9Pa through treatment. The residual gas analyzing method can effectively identify the type of gas about outgassing, narrow the scope of outgassing subassembly, shorten the vacuum system recovery time, and improve work efficiency. The method of determining the outgassing source by residual gas analyzer can be applied in the fields of UHV and XHV, and it has a certain reference significance for further improving the system vacuum degree.
The photocurrent attenuation of GaAs photocathode within one hour after activation under three different vacuum pressure (5×10-9Pa, 5×10-8Pa, 5×10-7Pa) were recorded by automatically activated monitor. The results show that: the photocurrent quickly descend in the beginning and then descend linearly at a low slope; the amplitude of the quickly descending area were 10%, 14.74% and 36%separately, with the respective slope of the linear descending area were -0.00653, -0.01132and -0.02. Three samples’ gas components of H2, CH4, CO, H2O, O2, CO2 etc under the same vacuum pressure (5×10-8Pa)during photocurrent attenuation were collected by quadrupole mass spectrometer. By comparing the gas components content and the attenuation law of the photocurrent, it has been found that H2O and H2 had a greater impact on the stability of GaAs photocathode in the ultra-high vacuum environment and H2O was the predominant effect. This paper has important guiding significance and reference value in studying the stability of GaAs photocathode and the improvement of semiconductor photocathode process.
In order to know the influence of activation processes on GaAs photocathodes, three GaAs samples were activated by a fixed current of cesium source and different currents of oxygen source. The current of caesium source is same during activation to ensure initial adsorption of caesium quantum is similar, which is the base to show the difference during alternation activation of caesium and oxygen. Analysed with the activation data, it is indicated that Cs-to-O current ratio of 1.07 is the optimum ratio to obtain higher sensitivity and better stability. According to double dipole model, stable and uniform double dipole layers of GaAs-O-Cs:Cs-O-Cs are formed and negative electron affinity is achieved on GaAs surface by activation with cesium and oxygen. The analytical result is just coincident with the model. Thus there is an efficient technological method to improve sensitivity and stability of GaAs photocathode.
The gallium arsenide (GaAs) photocathode generally requires a high temperature thermal cleaning before (Cs, O) activation in order to obtain an atomic level clean surface. The process is useful to adsorb and deposit cesium and oxygen atoms. Generally considered, the photocathode needs to be cooled to 60℃ to activate for achieving better results. People usually keep the annealing time for at least 1.5 hours in practical production. In order to explore the effect of annealing time on cesium atoms which were adsorbed on GaAs photocathode, the experiment monitored the activation curves of three GaAs photocathodes samples which annealed for 0.5 hour, 1.0 hour, 1.5 hours respectively, and then compared the occurrence moment of the photocurrent and the first cesium peak by different annealing waiting time. The difference of the activation curves reflects indirectly that the photocathode surface temperature had an influence on the adsorption of cesium atoms during activation process. This phenomenon could explain from two aspects about atoms adsorption and electronic transport. The work has referential significance for experimental research and industrial production.
The basic principle and formation of the auto-gated power using hybrid automatic brightness control scheme were described in detail. The auto-gated power supply in the application process because the device precision and the low-light level image intensifier between individual differences, fall may cause some products in some cases the SNR and resolution, and decrease the consistency of the product. This paper puts forward the corresponding solutions to these problems. And through experiments on the improved auto gated power supply with automatic gated power has not been improved compared. Applications of the auto-gated power in military, police and civil area were forecasted.