KEYWORDS: Cameras, Adaptive control, Light sources and illumination, Histograms, CMOS sensors, Night vision, Electric fields, Sensors, Power supplies, Image processing
Based on the working environment and characteristics of EBAPS cameras, a theoretical analysis is conducted on the relationship between camera exposure time, bias voltage, and image brightness information. An adaptive control method based on histogram feature function is proposed and implemented in the camera. Firstly, multi-point metering is used to extract regions of interest, and variable exposure time adjustment steps and bias voltage adjustment steps are designed to reduce the system metering calculation while improving the convergence speed and stability of EBAPS camera adaptive adjustment. The experimental results show that when the light intensity varies within the range of 10-4Lux to 100 Lux, the EBAPS camera can automatically adjust two parameters included bias voltage and exposure time, to stabilize the brightness of the output image, improve the image information entropy and the dynamic range of the camera. This method can also provide reference for subsequent image recognition and target tracking.
Because of the non-uniform response generated during the development of EBCMOS( Electron Bombardment Complementary Metal Oxide Semiconductor), the images with non-uniform stripe noise is outputted by EBCMOS in low light environment, which seriously reduces the imaging quality of EBCMOS and has become an urgent problem to be solved. To solve this problem, the reason of stripe noise generation is analyzed, the image processing algorithm based on least squares linear correction model is implemented on FPGA, and the experimentation is completed. According to the result of experiment, this algorithm can eliminate the stripe noise of EBCMOS, and the non-uniformity of the processed image is reduced by almost 75% compared to the pre-processed image, the correction effect is fine.
Electron Bombardment Active Pixel Sensor (EBAPS) can work in photosensitive mode and electrical sensitive mode due to the special doping mode of CMOS. In both operating modes, after the target signal passes through the photoelectric conversion, gain and readout process of the EBAPS device, the readout signal needs to exceed the noise generated by the device to ensure the distinguishable output image. However, in the process of conversion and multiplication of the target signal, noise will inevitably be introduced. The noise will be amplified along with the signal, causing distortion or attenuation of the original signal, thus interfering with the quality of the output image and affecting human observation. Therefore, it is necessary to study the noise characteristics of EBAPS as a key factor affecting the imaging quality. For the development of high-performance EBAPS devices, this paper focuses on the noise characteristics of detection and imaging under different operating modes. By analyzing the working principle of EBAPS devices in different working modes, the noise sources that affect the imaging quality are obtained. In photosensitive mode, the noise of EBAPS is consistent with that of ordinary CMOS image sensor. These noises are mainly affected by CMOS process level, ambient temperature, working time and other factors, and can usually be removed by image processing algorithms. In the electric sensitive mode, the noise of EBAPS mainly comes from GaAs photocathode and the electron multiplication process of CMOS. These noises can be suppressed by reducing the working temperature, improving the surface defects and cleanliness during the chip preparation, and improving the doping process of the substrate. According to the noise generation mechanism, the noise suppression methods are proposed to obtain a high SNR digital output image. The above research provides some references for the following research on noise characteristics and noise reduction methods of digital low light level devices.
KEYWORDS: Optical filters, Technology, Night vision, Image filtering, Electron multiplying charge coupled devices, Design and modelling, Cameras, Image processing, Digital filtering, Color imaging
Advanced night vision technology can realize the "one-way transparent" situation to the enemy in night battle, which plays a decisive role in local confrontation. However, traditional high vacuum and low light level night vision devices based on analog signals have inherent functional limitations of not being able to share in real time and enhance processing. Meanwhile, in order to give full play to the visual characteristics of human eyes, new digital and colorized night vision imaging devices have become the mainstream direction of current development. Based on the basic principle of low light level devices, this paper summarizes the research of digital color low light level technology and makes technical prospects.
KEYWORDS: Image processing, Image enhancement, Image information entropy, Night vision, Digital image processing, Digital Light Processing, Detection and tracking algorithms, Visualization, Optoelectronics, Infrared technology
When the classical gray stretching algorithm is applied in digital low light level devices, it cannot meet the requirements of illumination environment change in large dynamic range, and the image processed under very low illumination or very high illumination is prone to the loss of target details, an adaptive gray stretching algorithm suitable for digital low light level devices is designed. The algorithm adds the variable of the brightness value of the original image information collected by the digital low light level device to the gray stretching transformation matrix, deduces the current environmental illuminance value according to the transformation of the brightness value, timely adjusts the relevant parameters in the gray stretching calculation matrix according to the environmental illuminance value, and obtains the gray stretching transformation matrix suitable for different image features under different illuminance environments, In order to meet the requirement that digital low light level devices should be suitable for the change of illumination environment in a large dynamic range. This paper also compares the adaptive algorithm with the classical algorithm, and gives the test results. At the end of the paper, the operation efficiency of the algorithm is tested to verify that the algorithm can meet the requirements of real-time image processing speed of digital low light level devices.
Aiming at the problem of the lack of comprehensive and objective evaluation methods for near-infrared and low-light-level multi-band fusion images, this paper proposes a multi-dimensional fusion image quality evaluation model that conforms to the interpretation habits of the human visual system. Firstly, the multi-source fusion image quality of low illumination CMOS, ICCD, EBAPS devices and near-infrared InGaAs detector is subjectively evaluated. Secondly, 14 classical evaluation indexes such as information entropy, mean gradient, mutual information and structure similarity are combined. The parameters of each index are dynamically adjusted, and finally an objective evaluation model is established based on the linear regression model. The SROCC, KROCC, PLCC and RMSE values of the optimized objective evaluation model and subjective evaluation score are 0.88, 0.72, 0.89 and 0.38, respectively, indicating that the accuracy and stability evaluation effect of the objective model is better. It solves the limitation of single factor evaluation index and realizes the comprehensive and objective quality evaluation of multi-source detector fusion image, which provides theoretical support and decision basis for the selection of night vision camera in complex illumination environment and the data fusion of multi-detector in low illumination condition. < <
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.
After more than 50 years of development, CMOS image sensor has become the most mainstream image sensor. At present, the most used solid-state imaging devices directly image optical signals through the internal photoelectric effect, while the EBCMOS(electron bombardment CMOS) is more popular in the military field. In order to achieve low illumination and high quality image detector, people put forward higher requirements for the minimum operating illumination, fixed pattern noise, dynamic working range and other indicators of CMOS image sensor, and dark current is an important factor affecting these indicators. There are many literatures about the research of dark current in CMOS image sensor, but there is no systematic report on the research of dark current in CMOS image sensor. This paper systematically summarizes the research situation of dark current in CMOS image sensor. In this paper, the mechanism of dark current generation of CMOS image sensor is summarized firstly. Secondly, the influence of structure design, fabrication process and working environment on the dark current index of CMOS image sensor is summarized respectively, and the research situation of dark current compensation method is summarized again. Finally, combining with the generation mechanism of dark current of CMOS image sensor, the formation mechanism and influencing factors of dark current of new proposed electron bombardment CMOS(EBCMOS) image detector are analyzed.
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.
Electron bombardment CMOS devices have the advantages of small size, light weight, and high imaging sensitivity. Studying how to obtain high-gain EBCMOS devices has a profound impact on industries such as low-light night vision technology. In the experiment, we combined Monte-Carlo ideas with the physical model of the interaction between the low-energy electrons and the substrate material, and the movement trajectory and distribution of the electrons in the solid were simulated, which proved the existence of the electron multiplication benefit. In the experiment, the incident electron energy is 4KeV, the incident electron beam diameter is 20nm, the thickness of the passivation layer is 60nm, and the thickness of the p-type epitaxial layer is 10 microns. The electron collection efficiency of the substrate material under uniform doping is about 46.5%. The maximum theoretical collection efficiency under gradient doping can reach 84%. The research on electron bombardment CMOS devices has certain reference value.
KEYWORDS: Image intensifiers, Power supplies, Analog electronics, Automatic control, Digital signal processing, Signal processing, Interference (communication), Digital electronics, Signal generators, Electrodes
This paper briefly introduces the basic working principle of auto-gating power source. Due to the presence of noise in the
circuit, the cathode pulse signal generated by the AD converter is unstable. In this paper, the circuit of the AD converter
is adjusted to improve the instability of the cathode high voltage pulse signal, especially in the case of low light and high
illumination to avoid the jitter of the pulse. The experiment was carried out. And it could guide the implementation of
this part of the circuit.
This paper introduces the basic principle of auto-gating power supply which using a hybrid automatic brightness control scheme. By the analysis of current as image intensifier to special requirements of auto-gating power supply, a feedback circuit of the auto-gating power supply is analyzed. Find out the reason of the screen flash after the auto-gating power supply assembled image intensifier. This paper designed a feedback circuit which can shorten the response time of auto-gating power supply and improve screen slight flicker phenomenon which the human eye can distinguish under the high intensity of illumination.
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.
KEYWORDS: Image intensifiers, Microchannel plates, Power supplies, Electrons, Electrodes, Rectangular pulse, Image resolution, Signal to noise ratio, Automatic control, Process control
The basic principle and formation of the auto-gated power, a new kind power of low-light level image
intensifiers, were described in detail. The advantages and disadvantages of auto-gated power with the
traditional high voltage DC power were studied. The imaging resolution and signal-to-noise ratio were
compared by experiment. Applications of the auto-gated power in military and civil field were
forecasted.
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