Design Of Signal Acquisition System Base On Small Pixel X-RAY Liner Array Detector Card

Industrial CT (ICT),namely Computer Tomography, is presently the best testing technology in the Non-Destructive testing field, which is widely used for the detection of industrial products. As the development of technology and manufacturing industry, people put forward higher requirements for its capacity of detection and image resolution, especially in fields such as microelectronics devices and biological engineering, due to the devices'small size and complex internal structures.For these needs, this subject developed a signal acquisition system based on small pixel size X-ray linear array detector, which can be applied to low-energy X-ray of the small focal / micro focus CT system, and completed the detection of small sophisticated detection devices.? As an important part of industrial CT system, the function of the signal acquisition system is to complete the X-ray signal's acquisition, conversion, and then provide the signal to the host computer for image reconstruction through the transmission control system.The signal acquisition system consists of three parts: signal detection module, signal converter circuit and master control module. The signal detection module completed the X-ray signal detection and pre-conversion , using the linear array detector chip X-CARD 0.2-256G produced by DT Company . This chip integrates scintillator, coated photodiode arrays and signal processing circuit. It can detect X-ray whose energy ranges from 20Kev to 160KeV, and then convert them to analog voltage signal. It can improve the image resolution with the pixel size of only 0.2mm; a chip with 51.2mm in width which integrates 256 detector pixels enhances the acquired data capacity and reduces scanning indexing. AD7674 is used as signal converter to realize high precision conversion. FPGA chip which has parallel processing capacity is used as controller for this design, and it is also used to receive command, control timing signal of collecting, acquire high-speed data and transmit them.The main work of this task can be divided into two parts: the hardware's design and the logic design. The hardware's design adopts method of structured designing, considering the system's expansibility and compatibility , the hardware system was designed based on the modularization, which could designed according to different equipment needs to increase or decrease the number of the detector chip.The logic design adopts the top-down design ideas, and this design achieves the high speed of data acquisition and transmission by virtue of the asynchronous RAM and Ping-Pong operation .The codes were programmed in Verilog HDL language, meanwhile Quartus II softwareand ModelSim software were used for compiling, integration and simulation. In the combined testing process with the card and the detecting system, SignalTap is used to monitor the internal signal in FPGA.This signal acquisition system had completed the joint commissioning test with the existing transmission system and the host machine, the test results show that the signal could be transmitted quickly and accurately, and the design can achieve the desired objectives.