A new method of FOV quality test of the anti ion feedback microchannel plate was introduced, Ultraviolet Photoelectric Method, and the principle and the structure of the device were given. The test principle and device structure are given. The problems in the testing, including the mutual relationship between the UV transmittance and the quantum efficiency of the Au cathode, and the influence of the photoelectrons on the field of view caused by the UV-excited MCP were discussed. The advantages of the UV photoelectron method in the field defect detection were compared. Which provided a basis for the application of Ultraviolet Photoelectric Method and proves the research direction.
Rb+, Cs+ and other alkali metal ions in the Micro-channel Plate（MCP）channel, under the action of an electric field, leave out of the channel wall of MCP, and accelerate to input surface of channel along the opposite direction of the electric field to form ion feedback-induced noise. The feedback ions will cause great harms, it will bombard the cathode surface, resulting in decreased cathode sensitivity, reducing tube life, so you must take measures to reduce ion feedback-induced noise. This paper analyzes how to reduce ion feedback-induced noise from five aspects of the MCP materials, etching, annealing in hydrogen, high-temperature baking and electron scrubbing. Through the utilization of mixed alkali effect of suppressing mutual diffusion and decreasing internal network cavity to improve structure of MCP glass wall, the diffusion coefficient of each ion is reduced; the content of Al2O3 is reduced to reduce the Na+, K+ diffusion losses; etching process is optimized, except for the acid corrosion, the alkali corrosion, special acid etching and vacuum baking process are used; annealing in hydrogen technology is also optimized, the time of annealing in hydrogen was chosen on 270 ~ 350 minutes; and the vacuum baking and electron scrubbing are handled before manufacturing. By the above methods the ion feedback-induced noise is reduced.
As the development of Gen III Image Intensifier, photocathode sensitivity, spatial static resolution and
signal-to-noise ratio of the devices are continuously improved except for the view effect. However, for
most devices, the equivalent background illumination (EBI) is excessive, and considerable part is more
than an order of magnitude. Many factors have an effect on the EBI of the Gen III Image Intensifier. By
academic analysis and experiment research, it is demonstrated that: It is the thermal electron emission
of photocathode, dark current, gain of micro-channel plate (MCP) with ion barrier film(IBF), electric
field strength between MCP and photocathode and the light feedback of phosphor that lend to the EBI,
but for the phosphor screen made by the normal process, because of the aluminum film, EBI caused by
the optical feedback is slightly lower, which can not cause the excessive EBI. For the MCP with IBF
after normal processing, even the first focused voltage is added to 350V, the EBI does not exceed the
highest value of 1.66×10-7 allowed by national military standard. Needless to say the photocathode is
the focus factor of the EBI after excluding the phosphor screen, the MCP and other influencing factors.
It is believed that the thermal electron emission of photocathode leads to the excessive EBI. Finally,
without reducing the photocathode sensitivity, by optimizing activation technics, i.e., reduce CsO
quantity, and aging test disposal, the thermal electron emission is weaken, the EBI is becoming lower,
most of the products satisfy with request of technical standard in this index. That is valuable to
accelerate the engineering of Gen III Image Intensifier.
High illumination resolution, which directly determines the applied characteristic of night vision system in flashlight or
high light level condition, is an important performance parameter for evaluating the characteristic of low light level
image intensifier used in high light level condition. In this article, according to the limited resolution test technique, the
test principle, test condition and test method to high illumination resolution are described in detail associated with
operation mode and protective way of low light level image intensifier. Test system for measuring the high illumination
resolution has been founded based on the limited resolution test system. The value of high illumination for measuring the
high illumination resolution has been calculated in theory and measured by illuminometer. High illumination resolution
of low light level image intensifiers have been measured in test system, results show that high illumination resolution test
system is satisfied the need for measuring high illumination resolution of low light level image intensifier, and test
system output light illumination must be greater than 1×103 lux. Light of high illumination, which can be correctly
measured by illuminometer, is transferred legitimately. That is worthwhile to evaluate the operational characteristic of
low light level image intensifier.
First proximity voltage is the voltage between the cathode of Low Light Level image intensifier and the input surface of
Micro-channel plate（MCP）. There are so many factors influencing the image intensifier performance, and the first
proximity voltage is one of the most important factors that can not be ignored. Based on the theory analysis and test of
different proximity voltage on the gain、signal-to-noise ratio and equivalent background noise, this test has studied on the
important performance of Gen III image intensifier effected by the proximity voltage. By the experimental study, the
increase of first proximity voltage to a certain extent can improve gain、signal-to-noise ratio and equivalent background
noise at the same time. The main cause of this phenomenon is that the increase of proximity voltage can enlarge the
incident electron energy, and then improve the quantum efficiency of the incident electron; meantime, stray electron
produced by field emission at the action of the electric field of filmed-MCP will lead to equivalent background
deterioration. Ultimately we conclude that: 1) Signal to noise is proportional to the square of he cathode sensitivity,
increases with the first collision energy of the incident electron, especially at 200-500ev. 2)In the increasing process of
voltage from 300v to 800v, the gain of filmed-MCP increases rapidly, but lower again when Upk increases further because
of gain self-saturation; lgG and lgUpk are linear relationship, thus the curve can intuitively demonstrate the relationship
between them. 3) Stray electron produced by field emission at the action of the electric field of filmed-MCP will lead to
equivalent background deterioration, but will not exceed the requirements of technical specifications（2.5×10-7lx）.
According to definition of noise factor of microchannel plate and the test principle, the authors set up a test installation,
and measured the numerical values of MCPs which were made of different materials and channel pore including no /
with ion barrier film in input of MCP. In order to seek the technical approach to reduce noise factor of MCP at the same
time, we tested and analyzed the relation between noise factor and MCP voltage, combined relation between
signal-to-noise ratio of GEN Ⅲ image intensifier and MCP voltage, open out relation between signal-to-noise ratio of
GEN Ⅲ image intensifier and noise factor of MCP with ion barrier film.
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.