一种用于距离选通的ICCD设计与实现

The Design and Implementation for a Range-gated ICCD

研制了一种短余辉、高分辨率、快时间响应的高速选通超二代像增强器,通过光纤锥与CCD进行耦合成高性能距离选通ICCD,理论分析各部件的性能及其对系统空间分辨率的影响;采用FPGA设计电路控制系统,该系统产生出纳秒级的选通门宽以实现对ICCD的数字控制,同时可以对选通脉冲宽度和延时时间进行调整以实现不同亮度以及距离目标的清晰成像,降低背景噪音以及增大成像的动态范围.此外,该系统具有增益监控和调节功能,信噪比达到20∶1dB,在超二代像增强器阴极和微通道板输入面之间加幅度为-200V、宽度为3ns直流连续可调的选通脉冲以实现对增强器的选通,为了提高光电阴极补充电子的速度,在输入窗内表面光刻有线宽为5μm、间距为50μm正方形格栅以保证选通门宽为3ns时光电阴极有足够快的响应速度,选通频率最高可达到300kHz,实验测试在微通道板电压为700V、荧光屏电压为5 000 V时增强器增益可达10 718cd/m2 lx,ICCD系统空间分辨率达到29.7lp/mm.

A high-speed gated second generation image intensifier which is of short afterglow, high resolution and fast response time was designed. A high performance range-gated ICCD was obtained by coupling a fiber taper to CCD. The performance of each component and their effects on the system spatial resolution were analyzed. FPGA was employed to design the circuit control system which can achieve digital control for ICCD by producing a nanosecond gating width. The system can also obtain clear images of objectives in different brightness and distance by adjusting the pulse width and delay time. In addition, the background noise was reduced and the dynamic range of imaging was increased. The gain of this system can be monitored and adjusted to reach a signal-noise ratio of 20 ： 1 dB. A gating DC pulse with voltage of -200 V and width of 3 ns-DC continuously adjustable was applied to achieve image intensifier gating. In order to improve the supplement speed of electrons to the photocathode, a square grid which has 5μm line width and 50μm spacing lithography was equipped to the input window surface. This alsoensured that the photocathode response speed is fast enough when the gating width is 3 ns. The highest gating frequency can reach to 300 kHz. The experimental test shows that the gain of the image intensifier is 10 718 cd/m2 Ix when Mierochannel Plate voltage is 700 V and phosphor screen voltage is 5 000 V, the system spatial resolution is 29, 7 lp/mm.