Development Of Readout Electronics System For X-ray Detector Based On Array CCD

X-ray detector is a device that converts X-ray signal into electrical signal.It is widely used in medical,industrial detection,security inspection,space detection and other fields.Charge coupled device(CCD)has been widely used in the field of photoelectric detection and imaging due to its low signal output noise,large dynamic range,high quantum efficiency and high charge transfer efficiency,as well as its high sensitivity and accuracy for information expression.According to the requirements of high resolution and large target detection,the hardware circuit design and FPGA logic design of the electronic readout system of X-ray detector based on area array CCD were completed to realize the acquisition and transmission of X-ray imaging data.The main work of this paper is as follows:In this paper,the working principle of CCD was analyzed,and the generation,storage,transfer and readout of charge in CCD were studied.According to the different arrangement,CCD was divided into linear array CCD and area array CCD.According to different charge transfer modes,area array CCD was divided into full frame CCD,inter line CCD and frame CCD,their characteristics and working principle were introduced respectively.Then the system structure of X-ray detector based on array CCD was analyzed,including scintillation screen,optical fiber,CCD,readout electronics system and refrigeration device.Then,according to the system requirements,FPGA was selected as the main control chip,and Gigabit Ethernet was selected as the data transmission interface of the high-speed image acquisition system.In this paper,the structure and working principle of X-ray detector based on 2×2CCD were analyzed.The X-ray signal was collected by optical cone coupling 2 × 2CCD.The output charge signal was stored in FIFO after AD conversion,and finally transmitted to the host computer through Gigabit Ethernet.In this paper,FPGA was used as the main control device,and its peripheral circuit and configuration circuit were designed;According to the characteristics of low energy X-ray source of X-ray imaging equipment,KAF-16803 with high signal-to-noise ratio and small pixel size was selected,its parameters and performance were analyzed,and the DC bias circuit and driving circuit of CCD were designed;AD conversion used AD9826 the special analog-to-digital conversion chip for CCD,analyzed its function and characteristic,and completed the design of related circuits,FPGA and PHY were used to complete the data transmission.The paper designed the main control chip FPGA firmware logical,finished KAF-16803 timing drive,AD9826 register configuration and single port correlation double sampling implementation,Gigabit Ethernet transmission system timing In ISE14.7,the program was written with Verilog HDL language,and the feasibility of this scheme was verified by the final compilation,simulation and upper computer imaging.The readout electronics system was tested and packaged.The results shown that the detection area of the detector was effectively expanded by the splicing CCD mode of light cone coupling,and the readout electronics system meet the low noise characteristics.