In this paper, a low-light-level panoramic imaging system was designed based on the domestic second generation semi low-light-level tube. It has a waveband of 0.4 μm to 0.9μm, an effective focal length of 2.43mm, a working F-number of 1.5, and a field of view 30°～100°. Simulation results show that in the entire field of view, the f-θ distortion is less than 6%. The value of the MTF at 24 lp/mm is greater than 0.3. A mechanical structure supporting was designed. The stray light of this imaging system with its mechanical structure supporting was theoretical analyzed by using the software ZEMAX. A actual measurement was also carried out by a France stray light measuring instrument REFLET-180. The actual measurement results match with the theoretical results well in the simulation accuracy that verify the correctness of theoretical analysis and prove the feasibility of system design.
In the proximity focusing imaging system, the clear degree of images characterized by electronic scattering radius which
could directly decide the resolution. In generation Ⅲ image intensifier, ion barrier film on the input of MCP is a serious
influence factor on device resolution due to its electron scattering process. In this paper the electronic scattering radius
would calculate at the single electron scattering, large electron scattering, and having ion barrier film electron scattering.
Through comparing, it is found that the electron scattering radius is significantly larger at having an ion barrier film on
the input of MCP. The results of calculation show that reducing the gap cathode-MCP and increasing the cathode voltage
could reduce electron scattering radius, so as to improve the resolution of generation Ⅲ image intensifier.
In order to research the influence of the quantity of the Micro-Channel Plates (MCP) on the detectable threshold
of the ultraviolet image intensifier tube, the wide spectrum image intensifier gain tester produced by Nanjing University
of Science and Technology is employed to test the relation curves between self-made one single MCP ultraviolet image
intensifier tube, two double MCP ultraviolet image intensifier tubes, and photocathode incidence radiation illumination
respectively. With reference to the 3rd-generation low-light image intensifier failure theory, if the radiation gain of the
ultraviolet image intensifier tube is defined as 1,000cd/m2, the tube will lose the effect of image intensification, when
the corresponding photocathode incidence radiation illumination will be the minimum detectable threshold. Viewed
from the test results, the minimum detectable threshold of the single MCP ultraviolet image intensifier tube is 3.0×10-6
W/m2, with the radiance gain linear interval between 3.0×10-6 W/m2 ～4.6×10-5 W/m2; and that of the double MCP ultraviolet image intensifier tubes is 4×10-7 W/m2, with the radiance gain linear interval between 4.0×10-7 W/m2 ～2.0×10-5 W/m2. The test results were analyzed on the basis of the MCP self-saturation effect, concluding that the saturation current density of the single-unit MCP is a fixed , but there may be certain difference among the saturation current density of different MCPs due to different materials and manufacturing processes. The test results show that the maximum of the radiation gain linear interval of the three ultraviolet image intensifier tubes are at the magnitude of 10-5 W/m2, and the non-significant differences also verified the theory. In the double MCP ultraviolet image intensifier tubes, the photocathode-produced photocurrent is multiplied in passing the first MCP and then reaches the second MCP, so the second MCP will reach the state of current saturation earlier than the first MCP, making the minimum detectable threshold of the double MCP ultraviolet image intensifier tubes is lower than that of the single ultraviolet image intensifier tube by one order of magnitude, with the linear gain interval increasing by one magnitude, and the absolute of the corresponding radiation gain of the same radiation illumination within the linear gain interval increasing by 10
times, verifying that the double MCPs can detect much lower and weaker ultraviolet radiation and realize the high gain
theory. The research results has certain guiding effect towards the promotion and application of the double ultraviolet
image intensifier tubes, and has great significance on enhancing the high ultraviolet radiation detection and imaging
The GaAs photocathode has been widely used in optoelectronic devices such as image intensifiers and
photomultiplier tubes, but it is inevitable for these devices to withstand a variety of mechanical shock. In order to study
the impact on the GaAs photocathode’s photoemission performance caused by mechanical shock, GaAs photocathode
image intensifier is researched in this paper . The spectral response of the GaAs photocathode was tested respectively
before and after several value of mechanical shock（the value of mechanical shock:55g，65g，75g，85g and 95g）.The
parameter of the GaAs photocathode can be calculated and the quantum efficiency curve can be fitted as well using the
MATLAB software. The results show that surface escape probability is increased after photocathode is subjected to
mechanical shock, so that its photoemission performance will be improved. We think this phenomenon is due to the
GaAs photocathode surface Cs-O reconstruction. This finding provided a new method to enhance the photoemission
performance of photocathode.
The focus of the third generation image intensifier photocathode sensitivity decreases in the GaAs are analyzed, and
proposed solutions,experimental results show that the tube microchannel plate(mcp), screen GaAs cathode discharge gas
is caused by decreased sensitivity of the main reasons. Paper used two-layer model, and even negative electron
affinity(NET) interface barrier theory of the photoelectric cathode drop mechanism was discussed , when the
photocathode emission levels of CO adsorption and other harmful gas, chemical adsorption layer of ionic bond formation
will lead to production of cathode surface barrier interfaces. Cathode surface adsorption of the pollutants more ,the
interface barrier becomes thicker, the smaller the electron surface escape probability, when the cathode interface thicker
barrier to the electron surface escape is zero, the cathode photoemission end of life.
In 3rd generation image intensifier, Al2O3 film on the input of MCP is a serious influence factor on device MTF due to
its electron scattering process. There are no reportes about how to measure the MTF of Al2O3 film. In this paper a new
Half-film comparssion test method is creatively established for determing the film MTF, which overcomes the difficulty
of measuring super thin film less than a few nm. In this way, the MTF curves of 10nm Al2O3 film can be accurately
obtained. The measurement results show that 10nm Al2O3 film obviously decay the MTF performance of the 3rd
generation image intensifier and take an important role in the improvement work of 3rd generation image intensifier
MTF and resolution performances.
In order to suggest the performance of low-light-level night vision device affected by backscattered electron from ion barrier film(IBF), in this paper, based on the idea of Monte-Carlo, the track of electron impinging and rebounding on ion barrier film is simulated. The Lambert distribution and Beta distribution are used to calculate electron’s emission. The Mott cross section and the Bethe formula rewrited by Joy are used to describe and calculate the elastic and inelastic scattering electron traversing in the film. With the statistic of the total transmitted electron and the discussion on the effect of cathode voltage, proximity between ion barrier film and photocathode on performance of low-light-level night vision device, we get the point diffusion function of ion barrier film, and we conclude that in low light level backscattered electron hardly affect working of image intensifier and higher cathode voltage, closer proximity between cathode and ion film will reduce the impact of backscattered electron in high light level.
In order to illustrate the performance of intensifier affected by gas on surface, the kovar ring surface has been tested by
XPS. According the result, gas type and quantity are calculated. With the theory of thermal and electron stimulated gas
desorption, the remaining gas on surface after thermal and electron treatment is reckoned and the surface outgassing
rate is evaluated on the assumption that the image intensifier is working in the 10-3lx environment. Then, the performance of image intensifier is evaluated by the effect of gas on the surface at last.