Low Energy X-ray Detection And Image New System

There is outstanding merit to apply X-ray Industrial Computed Tomography in the field of nondestructive test and nondestructive evaluation. The result of test and evaluation depends on the quality of reconstructed image. In practice, the radiation detecting and data acquisition system acts as a crucial sub-system of the detecting and imaging system. Therefore, its reliability, stability and the accuracy and coherence of the data acquired by it not only has a direct influence on the quality of reconstructed image, but also decide the performance of CT to a large extent, even if the high development of computer imaging technology also has a strong influence on the quality of image,At the present time linear detector array composed of photodiode array is used widely. Although it is better than amorphous silicon flat-panel detector used previously in some performance, such as resolution, speed and SNR, it can't develop further. As a sort of novelty photoconductive semiconductor device, CCD has the advantages of small volume, high test precision and high-speed high SNR and so on, which promote the detector made of the CCD to the development trend of the detecting field in the future. Now, it is the new orientation of the development of linear CCD array to sample, save and process the target in high frequency. However, it is the preoccupation to choose a processor which can meet the requirements. In recent years, FPGA, which is a kind of programmable logic device with characteristic of high speed, parallelism and abundant inner resource, is used as a controller widely in many fields. And it is approved that FPGA is better than congeneric devices in many sides, for example, speed, power consume, source, convenience to design, etc.This project was proposed for the low energy X ray detect and image system, which is based on the CCD and FPGA devices. The paper first briefly introduced the principal of the industry X-CT system, the scanning and detecting mode and the composition of the system. Based on the introduction illustrated above, introduced two most important branches of the detector------linear detector array and CCD detector, and focused on the CCD detector, introduced its fundamental principal, principle of operation, signal readout mode and speciality parameter, etc. Against its different characteristics, two projects were put forward, which are the combination of linear detector array and switched integrator and the combination of CCD detector and the ADC.The same point of the two projects is that they both use FPGA as system controller to drive the time sequence and control the signal; the difference is that the LDA technology is already matured while the CCD technology has such as high accuracy, high signal noise ratio, low cost and so on, and all this merits can be made full use of in the industry X-CT system. After compared the two projects, select the later to accomplish, use the CCD as image sensor, FPGA as major controller, enlarged the raw data, filtered, and analog to digital converted, then transferred to the top host. Used the software Protel DXP designed the hardware and made the PCB, employed the VHDL and Verilog HDL hardware description language programmed the soft sequence and made the sequence and function simulation on the Altera synthesis develop platform, and at last made the total system debug, verification is made that all the functions were applied. This project realized the detection and collection system design, fully accomplished the function of data transformation for the image formation.