The non-interferometric phase recovery method which is based on the transport of intensity equation is an important phase acquisition technique in microscopy imaging. In the actual operational process of this technology, at least three intensity images are needed to solve the equation. In the image acquisition process, the selection of the focused image is very important, but it is usually determined by subjective methods, thus causing inaccurate positioning of the infocus, which further affects the precision of phase recovery result. A phase recovery algorithm based on edge detection and duty ratio is proposed. Firstly, a series of 'subjectively determined focused images' collected by the microscope are edge-extracted to obtain corresponding edge information points. Then the real in-focus position is found by calculating the duty ratio, and the corresponding defocused images are selected according to the position of the focused image. Finally, the high-precision phase recovery result is obtained by using these images of the accurate position to solve the equation. The algorithm does not require complex operations such as hardware modifications and can be applied to both discrete and continuous sample distributions. The experimental results effectively prove that the algorithm can accurately find the in-focus position, which improves the accuracy of phase recovery compared with the traditional method that is subjectively determined in-focus image position.
Micro-channel Plate (MCP) with Ion Barrier Film(IBF) is one of the main technical indicators that restrict the performance of the third generations of Low Light Level Image Intensifier(LLLII). IBF with inferior quality can be a direct impact on the performance of the third generations of LLLII or even makes it not work, and it’s very unfavorable in the tube mass production and promotion. In response to this urgent requirement, in order to improve the quality and preparation of the finished product of the Al2O3 on the input side of MCP prepared by magnetron sputtering, the paper carries out the process optimization of magnetron sputtering used for image intensifier. By simulation of Ar ion bombarding Al2O3 target, while under the guidance of the working principles of the magnetron sputtering and thin film growth theory, we change the working pressure、 sputtering power、 argon flow and other process parameters by using magnetron sputtering machine developed in China, to change the coating deposition rate of Al2O3, and to increase the lateral migration of the film-forming process of Al2O3. Finally we prepare a uniform、 continuous and compact Al2O3 Ion Barrier Film. At last the optimal technique is obtained: Sputtering pressure is 2.6×10-1Pa, Ar2 flux is 90sccm, sputtering power is 170W, and the thickness of film is 80Å. We test the performance of MCP with optimized films by using the MCP performance testing devices, contrasting with pre-fabricated thin-film quality, and the results show that the average gain decline is dropped, the dead volt is lower, and the quality of the films prepared by this process is significantly better, yield and view pass rate is as high as 90%, meeting the dual demands of high electronic transmittance and high ion blocking rate of IBF.
In order to precisely predict the sensitivity of Ф18 mm transmission-mode GaAs photocathode, a concept of integral diffraction intensity is proposed based on X-ray diffraction principle after analyzing the predecessors′ limitations of testing the micro-area of such photocathode and GaAs photocathode of image intensifier tube is plane electron source in this paper. The integral diffraction intensity on the entire photocathode surface was obtained by multi-points detection in the effective area of the photocathode with integral method. The crystal quality of entire photocathode surface will be taken with the integral diffraction intensity. According to the principle, X-ray diffraction testing for 4 samples of GaAs photocathode modules was executed with high-resolution four-wafer X-ray Diffractometer whose test spot size is 4 mm×5 mm. The diffraction curves were obtained and the integral diffraction intensity was calculated. Subsequently the 4 photocathode modules was activation processed with Cs-O in ultra-high vacuum system simultaneity the photocurrent of photocathode modules was measured. Comparing the variation of diffraction curve with integral diffraction vs photocathode photocurrent curve, they show that the greater the integral diffraction intensity of is, the more photocurrent is in the photocathode module. The variation relation curve between X-ray integral diffraction intensity and photocurrent in the photocathode was fitted with least square method. The curve, which accords with logarithm curve and whose fitting degree is 0.878, was achieved. Since photocathode sensitivity is direct proportion to photocathode photocurrent. The above results prove that A Practicality Φ18mm photocathode of image intensifier tube is plane electron source, GaAs photocathode sensitivity and other photoelectric performance lies on entire photocathode surface crystal quality, the photocathode module integrality reflected by the integral diffraction intensity plays crucial role of GaAs photocathode sensitivity. So integral sensitivity of Ф18 mm transmission-mode GaAs photocathode can be precisely predicted with X-ray integral diffraction intensity, some feasible ideas for further research of GaAs photocathode was obtained in this paper.
To establish a methode for predicting the integral sensitivity of transmission-mode GaAs photocathodes, the relationship between X-ray relative diffraction intensity and integral sensitivity of GaAlAs/GaAs photocathode material is researched. After thermocompression bonding Si3N4/GaAlAs/GaAs/GaAlAs/GaAs epitaxial material to glass window in the vacuum condition, and chemically etching the GaAlAs buffer-layer and GaAs substrate, the glass/Si3N4/GaAlAs/GaAs photocathode module is formed. The X-ray relative diffraction intensity of the photocathode module is tested and calculated respectively, then the photocathode surface was activated in the ultrahigh vacuum chamber using the Cs-O activation technique. Following that, the integral sensitivity of the transmission-mode GaAs photocathode is measured by the spectral response measurement instrument in situ. It is found that the GaAlAs/GaAs photocathode material and photocathode module have similar X-ray relative diffraction shapes. The higher the similar degree of X-ray relative diffraction shape is, the bigger the X-ray relative diffraction intensity of photocathode module is, which results in the better photoemission capability and higher photocathode integral sensitivity. This method can be used as an evaluation criterion for the quality of transmission-mode GaAs photocathode module material.
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