Research On High Speed Gated Image Intensifier Driving Technologies

An image intensifier is the key component of the night vision device. With extremely high gain, it amplifies light from an image so that a dimly lit scene can be viewed by human eyes. Recently, gated image intensifier, can provide better resolution and sensitivity, extending its applications to the area of security, industry, scientific research and medical care.In this paper, we introduce the basics of image intensifier system. With the field-solving functionality provided by the powerful software CST, we analyze the electro-magnetic field distribution in the tube of the intensifier,which is helpful to design the driving circuits. After study the generic electronic devices and common pulser technologies, a nanosecond-scale high voltage and high speed gating pulser is designed and implemented by three schemes.The first scheme is based on the fully utilization of power MOSFET. Firstly, the pulse response of the power MOSFET is analyzed by the equivalent circuit theory. Then, a Cascode pulser with trailing edge acceleration is designed efficiently by the aid of SPICE simulation. Due to the high speed nature of pulser, some PCB and gate-driving techniques, are applied to guarantee the optimal waveform quality in high speed driving circuit. Finally, 200V pulse with edge speeds below 4ns is obtained.To further improve the edge speeds and shorten the pulse width, two pulse forming network based schemes are proposed later. These two schemes use mercury relay and avalanche transistor as key component respectively. The length of the transmission line is used to set the corresponding pulse width. As a result, a 200V pulse with edge speed of 700ps and width of 5ns is obtained for the mercury relay based scheme. Another 200V pulse with edge speeds of 2ns and width of 10ns is measured for the avalanche transistor based scheme.In order to understand the performance of the above high speed high voltage pulser in depth, the bandwidth limitation of the instrument is also investigated. The end of this thesis is the summary and comparison of measuring results for the all three schemes.