In order to improve the calculation accuracy of multialkali photocathode image intensifier’s modulation transfer function, base on the modulation transfer function model of proximity focusing structure. Collecting the modulation transfer function data of image intensifiers that having different cathode types, different cathode materials’ escape equivalent initial potential of photoelectron how to affect modulation transfer function is explored. The modulation transfer function model is optimized on the strength of cathode material characteristic parameter. The results show that in view of the difference between the cathode material characteristic parameters, the SSE between the calculated value of modulation transfer function optimized model and the measured value is less than 6, especially in the high spatial frequency region. The results have theoretical significance for further improving the resolution of high performance image intensifier.
The innovation of this paper is combining the micro-nano optical technology and the vacuum photoelectric imaging devices manufacturing. The multialkali photocathode deposition substrate is designed with a meta-surface structure by using the Finite-difference time-domain. According to the nanoimprinting and the atomic layer deposition, the structure of meta-surface can be obtained. Metasurface have the ability of simultaneously controlling the phase of the light by tailoring the geometry of microstructures. The negative loss in the direction of light wave propagation is suppressed, the reflection at the interface between the cathode and the deposited substrate is reduced, and the absorption coefficient of the cathode material to the incoming light is improved. And the absorption rate of the incident light can be increased by 20.5%. The atomic layer deposition is used to prepare the nanolaminate on the surface of the micro-structure. Based on the imaging tube with the meta-surface, the experiment results show that the average value of the quantum efficiency increased by 21.2% in the visible light range and increased by 10.3% in near infrared band respectively, which reaching the international advanced level. A new method is provided to improve the performance parameters of the vacuum photoelectric imaging devices and point the direction for the improvement of the imaging tube. As shown in this paper, the performance parameters of the vacuum photoelectric imaging devices still have great development potential by optimizing the structure of the meta-surface.
The image intensifier is the core component of all kinds of low-light-level night vision devices, which are widely used in security, medicine, biology, and other fields of detection and imaging devices. Multialkali photocathode is one of the important parts of the image intensifier photoelectric conversion. Its optical constant and thickness will affect the sensitivity of the image intensifier. The photocathode material is a chemically active alkali metal (Na2KSb (Cs)). When the photocathode is removed from the high-vacuum alkali source environment of the image enhancement tube, its properties will change. Therefore, it has been impossible to directly measure the optical constant and thickness of the photocathode. In this paper, we established the photocathode optical model with the help of the Snellmeier dispersion model. The optical constants and thickness of the photocathode in the visible band 380nm-780nm are obtained for the first time by the full-spectrum fitting method. The deviation between the fitted value and the measured value is 0.03%, which is in good agreement. The optical constants and thickness of the photocathode obtained in this paper can provide more accurate guidance for the optical system design of image intensifiers. In addition, the method can be extended to the analysis of optical properties of other easily oxidized thin film materials by changing the dispersion formula, which has practical significance in the fields of vacuum optoelectronics and optical thin films.
The microchannel plates are electron multiplier which mainly used in image intensifier tubes for imaging and intensification of the photoelectron image. In this paper, the research models of the funnel microchannel plate are established by the CST Studio Suite software. The whole research model includes the particle emission source, the funnel microchannel plate model with input reinforcement film and the detector module. Under the same parameter settings of the particle emission source, the influence of the input electrode depth of the funnel microchannel plate on the incident particles is studied. The detector module is placed in a fixed position and the electrode depth vary from 0 μm to 7 μm with an appropriate step. Under different electrode depth, the electron distributions on the input surface and at the 7 μm depth of the funnel microchannel plate are obtained. After processing the data, the influence of the input electrode depth on the incident electron distribution is obtained, which lays a foundation for the further theoretical and structural research of the funnel microchannel plate. Meanwhile, the related experiments are carried out for the funnel microchannel plate with different input electrode depth, and the experimental results are compared with the simulation results.
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