- 學位論文
現場可程式化邏輯閘陣列應用於光學同調斷層掃描系統之訊號控制模組
Development of Signal Control Module with Field Programmable Gate Array for Optical Coherence Tomography Application
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摘要
可攜式光學同調斷層掃描(Portable optical coherence tomography, portable OCT)系統通過在頻域式光學同調斷層掃描術(Spectral-domain OCT, SD-OCT)上整合微型化且低成本的運算平台，克服了傳統OCT系統體積龐大且造價昂貴的缺點，並繼承了傳統OCT系統所具備的高解析度、非侵入式的優勢，使其不再受限於大型醫療院所內的使用。然而，當使用單板電腦和小型電腦代替傳統個人電腦時，受限於運算平台有限的運算效能，無法快速地運算OCT重建所需的影像處理函式，導致可攜式OCT系統無法提供快速的成像以及高品質的三維立體影像。 在本論文中，我們將使用現場可程式化邏輯閘陣列(Field programmable gate array, FPGA)開發訊號控制模組，以實現電腦通過通用序列匯流排(Universal serial bus, USB) 3.0介面傳輸指令，使FPGA控制微機電系統(Microelectromechanical systems, MEMS)反射鏡以及同步擷取裝置的目標。訊號控制模組由兩個子模組所組成，分別為USB模組和MEMS模組。USB模組負責與USB控制器溝通，並將接收到的封包解碼成對應的指令，從而實現電腦與FPGA之間以USB 3.0傳輸的功能。MEMS模組則進一步將USB模組傳輸的指令分解為掃描範圍、軌跡等，並通過序列周邊介面(Serial peripheral interface, SPI)對數位微機電系統驅動電路板(Digital MEMS driver)輸出訊號以控制MEMS反射鏡，並將同步訊號輸出至擷取裝置，以實現系統掃描和擷取的同步。 在本論文中，我們首先獨立以USB模組測試FPGA與電腦之間傳輸資料的效能和正確度，接著使用共軛焦顯微術(Reflectance confocal microscopy)架構整合訊號控制模組對resolution target、grid target以及位置感測模組(Position sensing module, PSM)進行掃描，並以掃描結果驗證訊號控制模組的可行性。最後我們將訊號控制模組與芯聖科技(OPXION Technology, Inc.)開發的手持式光學同調斷層掃描儀整合，並將電腦通過USB 3.0控制FPGA的C++程式與台大光電所先進生醫光電影像實驗室(Advanced biomedical optical imaging laboratory (ABOIL), National Taiwan University (NTU))先前開發的圖形使用者介面(Graphical user interface, GUI)整合。達成以訊號控制模組控制和同步週邊裝置的同時，通過簡單的介面操作提供即時的二維成像、enface影像和高品質的三維立體影像，實現了以FPGA為基礎的可攜式OCT系統。我們相信本論文所得到的研究成果能為日後可攜式OCT的研究奠定良好的基礎，並促使可攜式OCT應用於更多偏鄉醫療檢測設施，為初級醫療(Primary care)展現更多的應用價值。
並列摘要
Portable optical coherence tomography (Portable OCT) systems, by integrating miniaturized and low-cost computing platforms on spectral-domain OCT (SD-OCT) overcome the limitation of traditional OCT systems, such as being bulky and expensive, and also retain the high-resolution and non-invasive advantages of traditional OCT systems, allowing them from being utilized beyond large medical institutions. However, when using a single-board computer or a mini PC instead of a personal computer, the limited computational power of these platforms limits the speed of essential image processing functions for OCT reconstruction. This limitation restricts portable OCT systems from providing fast imaging and high-quality three-dimensional OCT images. In this thesis, we propose the development of a signal control module by using a field programmable gate array (FPGA) to achieve the goal of controlling and synchronizing peripheral devices with FPGA. The system control module consists of two main submodules, the universal serial bus (USB) module and the microelectromechanical systems (MEMS) module. The USB module is designed to communicate with the USB controller and also decode the received packets into corresponding instructions, enabling the USB 3.0 communication between the computer and FPGA. The MEMS module decomposes the instructions received from the USB module to MEMS scanning range, MEMS scanning pattern, etc., and then transfers signals to the digital MEMS driver by serial peripheral interface (SPI), which controls the MEMS mirror. It outputs synchronization signals to the detector simultaneously in order to synchronize MEMS mirror and detector. In this thesis, we conducted tests using the USB module to evaluate the performance and accuracy of the USB 3.0 communication between the FPGA and the computer. Subsequently, we integrated the signal control module into a reflectance confocal microscopy framework in order to validate the feasibility of the signal control module by the results of scanning resolution targets, grid targets and position sensing module. Furthermore, we integrated the system control module with a handheld 3D skin viewer system developed by OPXION Technology, Inc. We also integrated the C++ program which controls the FPGA through USB 3.0 into a graphical user interface (GUI) developed by our laboratory. By successfully controlling and synchronizing peripheral devices using the signal control module, we also provide real-time 2D imaging, enface images, and high-quality 3D images through a user-friendly interface, representing that we implemented a portable OCT system based on FPGA. We believe the accomplishment of this thesis will establish a solid foundation for future studies on portable OCT, encourage the application of portable OCT in a wider range of healthcare facilities in rural areas, and shows the potential value of portable OCT being utilized in primary care.
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