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 view of the attenuation of performance index of self-developed EBAPS detector principle sample with the increase of working time and working temperature, a test method is designed from the angle of dark current noise and working temperature change, and the corresponding relationship between dark current and working temperature of EBAPS device is tested. Because EBAPS detector combines the characteristics of solid-state and vacuum micro-optical devices, it inherits the characteristics of dark current of CMOS chip changing with temperature. With the increase of temperature, dark current of CMOS chip increases rapidly. The rise of dark current will directly affect the equivalent background illumination of EBAPS detector. If the effective signal received by the detector is lower than the dark current noise signal at low illumination, that is, the effective signal is lower than the equivalent background illumination; the effective signal will be obscured in the noise signal, leading to the detector not working properly. In view of the characteristics of EBAPS detector, the test and calculation are also carried out. The data relations and change curves between the operating temperature, dark current and equivalent background illumination of EBAPS device are given. At the end of the paper, methods and ways to optimize the imaging performance of EBAPS detectors are presented, such as image processing algorithm, reducing the power consumption of readout circuit, and optimizing the dark current suppression process of EBAPS devices.
KEYWORDS: Signal to noise ratio, Ultraviolet radiation, Field programmable gate arrays, Microchannel plates, Night vision, Gold, Semiconductors, Light, Power supplies, Lamps
In the field of low-light night vision, EBCMOS (Electron Bombarded Complementary Metal Oxide Semiconductor) has received much attention due to its high-gain, high-resolution, low-noise, etc. The techniques used to test EBCMOS performance are also in urgent need of development. According to the composition of EBCMOS detectors, based on the existing vacuum device and semiconductor device test methods, the SNR testing method of EBCMOS is proposed and the testing system is designed. The Field Programmable Gate Array(FPGA)-based hardware platform is built in the vacuum environment. The CMOS data is read out by programmable logic design. Finally, the SNR is obtained by the MFC host computer. Experiments show that the system can measure accurate SNR parameters.
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.
Based on the study of working principle and making process of 4-transistor Backside-illuminated CMOS (4T BSI-CMOS), Signal-to-noise ratio (SNR) model are established and quantitative calculating formula is derived. In addition, factors of influencing SNR are analyzed. Two methods are presented to enhance the SNR, the one is optimizing structure of 4T BSI-CMOS image sensor to strengthen the signal and the other one is correlated double sampling to decrease fixed pattern noise (FPN). These results serve as useful guidelines to enhance the SNR of 4T BSI-CMOS and improve the image quality.
Solid low-light imaging device is an important part of night vision, which has the advantage of high resolution, high contrast and small size, and it can work 24 hours. A handheld high-resolution low-light camera is proposed based on the characteristics of GSENSE400BSI CMOS image sensor in this paper. The camera includes CMOS driver, image correction, cache, low-light image enhancement and ultra-clear format encoding, implemented on an FPGA-based hardware platform. And the camera structure is optimized designed to realize the handheld operation. Finally, the experiments show that the low-illuminance camera display the details of the target clearly under 10-2 lx illumination, with an effective display resolution of 2048×2048@60fps.
Low Level Light (LLL) night vision technology is extensively applied in national defense and civil application fields. The digitization of LLL imaging is trend of light detection technology in the future. The corresponding modulation transfer function (MTF) and total system MTF model were established, base on the structure composition and operation principle. Simulation was carried out to analyze the performance of the MTF modern. Results indicate that the MCPCMOS better contrast of object. When the spatial frequency increasing, the MTF of MCP-CMOS downing faster than that of GaAs LLL image intensifier. The GaAs image intensifier shows an better image restoration capability and higher limiting resolution. The model and simulation results can provide a theoretical guidance for the fabrication and application of high imaging quality MCP-CMOS.
The flawed surface of GaAs/GaAlAs heterointerface after wet etching by H2O2 and NH4OH based etch ant was studied in this work. The results showed that the surface of GaAs/GaAlAs heterointerface had convex point, etching pits, pinhole, fog point, and friction scratches were investigated with a etch step measurement. And imprinting the main reasons for the formation of the etching surface defects of GaAs/GaAlAs are the poor quality of epitaxial materials, the contamination of materials surface, the unclear interface of oxidation and doping, the inhomogeneity of concentration and the operation errors. The selective etching of the GaAs/GaAlAs material eliminates some flaws and improves the quality of the etching surface of the GaAs/GaAlAs material.
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