Proceedings Article | 16 August 2013
KEYWORDS: Image intensifiers, Microchannel plates, Aluminum, Image processing, Ion beam finishing, Analytical research, Cesium, Standards development, Transmittance, Image resolution
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.
