Research Of X-Ray Phase Contrast Image Data Acquisition System Based On Multi CMOS Chip

The Grating differential interference X-ray phase contrast imaging system needs large-area imaging digital X-ray detector. As a photoelectric conversion device of the imaging system, the digital X-ray detector is indispensable. In order to achieve large-area imaging to meet the practical application of the minimum requirement of 75×752mm, adopting four CMOS chip coupling four light-cone to consist of a 2×2 array of detector, so that the entire imaging area of the detector can achieve 98.5 × 98.52 mm after splicing. The big end of light-cone is coupled to the X-ray conversion screen, transmit the visible light which is converted from the X-ray conversion screen by total reflection way to the CMOS image sensor chip which is coupled with the small end of the light-cone to perform image acquisition. Due to the particular structure, there is no ready image data acquisition system for our system. Therefore, we need to design a X-ray phase contrast image data acquisition system based on multi CMOS chip. We adopt the ARM + multi FPGA system solutions, 4FPGA boards are used to drive the four CMOS chip respectively and each FPGA boards are equipped with SDRAM cache. Using ARM chip as the main controller of the entire system to control the image data transmission from SDRAM cache to memory on ARM board. And then the image data is sent to PC via Ethernet.In this paper, the main study are software design and implementation. In order to achieve the ARM board working in conjunction with four FPGA boards, the works below need to be done. Firstly, the Synchronization parameter settings of four CMOS chip is is done by ARM SPI interface adopting one master multi slave way. Secondly, the system uses the same ARM GPIO interface to connect with four FGPA boards, therefore need to design the control signal.This is done by multi-mode command assignment to achieve data communication between ARM and four FPGA boards. The data communication between 16 FIFO on FPGA board and ARM GPIO is done by a lightweight asynchronous bus transmission mode. We can achieve fast and stable data transfer through only once handshake. In order to achieveadjustable parameters of CMOS image sensor chip, We need to set different parameters dynamically via the PC. In the process of arguments transmission, We also need to control the order of the parameters and the format conversion of the parameters. Then the data transmission between ARM and PC is done by Ethernet. In the ARM program, We need to implement transmission and reception functions of the underlying network card chip as well as transplanting a lightweight TCP/IP protocol stack to implement the UDP data transmission.Finally, Against to the UDP transport unreliability, our system is designed for reliable and controllable UDP transport.This paper have implemented X-ray phase contrast image data acquisition system which have completed four CMOS chip parameters setting, camera control, data cache, data transmission and data storage and so on. The experimental results show the data acquisition system can stably perform data transmission among the PC, ARM and multi FPGA.