Design And Experimental Study Of ICCD Gating Pulse Source

As an imaging device coupled with an image intensifier and a CCD,ICCD has been widely used in low-light night vision,remote sensing monitoring,and biomedical applications due to its unique performance.In the field of ultrafast imaging,in addition to direct observation of short gate widths,ICCDs are also used as core imaging devices for framing cameras.Regardless of the application,it is critical to control the performance of the strobe source that turns on and off the ICCD image intensifier.This paper first introduces the structure principle of ICCD itself and its working mode in the framing camera.Based on this,the main factors affecting the shutter time of ICCD strobe are discussed.Aiming at the influence of photocathode on the gated shutter,based on the analysis of the working mechanism of photocathode gate,the basic photocathode RC charge and discharge model was established,and the photocathode was modeled and simulated by the microwave studio of CST software.Then,further design experiments were carried out to verify the results,which can shorten the gated shutter time from 160 ns to 5 ns after adding a conductive substrate to the photocathode.For the direct control of the ICCD gated pulse source,this paper firstly discusses the implementation of various strobe sources.After analyzing the characteristics,the pulse generation method combining coarse delay and fine delay is proposed.Based on this architecture,two design schemes are proposed:1.The programmable I/O delay module IODELAY in FPGA is used as the fine delay unit.The counter acts as the coarse delay unit and communicates with the host computer by RS232 serial communication protocol.The delay and pulse generation of the whole design are realized by digital circuits.After the simulation and analysis of the timing,the single-pulse delay accuracy of the design can reach 78 ps,and the inherent delay is 35.119 ns.2.Using Cortex-M4 as the core control chip for data processing and communication,FPGA is used as the coarse delay unit,and the fine delay part is realized by comparing and shaping the reference square wave,and adopting the method of dividing the active crystal oscillator to realize A higher strobe repetition frequency occurs.After the final design,the pulse source can have an output repetition frequency of up to 1 MHz,a pulse width of at least 65 ns,and a delay adjustment accuracy of 5 ns.