利用FPGA影像模組實現光點定位系統及其應用

Implementation of light spot positioning system using FPGA-based image module and its applications

范振能(Chen-Neng Fan)

國立虎尾科技大學/電機資訊學院/光電與材料科技研究所/碩士(2007年)

摘要

本論文提出了使用FPGA (Field Programmable Gate Array)硬體架構來當光點的定位系統之運算與控制核心，首先透過FPGA控制雷射指示器或LED (light emitter diode)的電源，使影像感測器依序的擷取有光點和沒光點的兩張影像，再由FPGA來把兩張影像的像素值做相減的影像運算，消去影像相同的背景，留下清楚的光點，使定位出影像裡的光點座標更為精準與容易。我們設計了一個適合FPGA架構的光點中心定位演算法，在搜尋影像中的光點中心時，採用少量的暫存器和取代式的演算法來定位影像中的光點中心座標，而非一般傳統以電腦為運算架構的光點定位演算法，採用統計所有亮點的座標後，再經過平均後得到亮點中心座標，比較起來我們設計的演算法省去了大量的暫存器儲存空間和運算的電路，使用的邏輯元件數目只為傳統光點定位演算法的16.6%。在與電腦的互動應用上，我們讓FPGA控制USB滑鼠模組裡的微控器，產生控制訊號來驅動電腦的滑鼠游標跟隨光點移動，完成無須考量電腦作業系統版本的差異性，也無須安裝任何驅動程式。此外我們再影像感測器前放置一個繞射光元件(diffractive optical element ,DOE)，可以模糊所擷取影像的背景，同時又使光點轉換為更大的繞射圖案，可以消除在背景不相同時，使用像素相減法所產生的相減雜訊(subtraction noise)。

並列摘要

In this thesis, we propose a FPGA (Field Programmable Gate Array) chip module to implement the light spot positioning system and its applications. We use image sensor to capture two successive images by controlling the power of laser pointer or LED (light emitter diode) ON and OFF. Then a simple subtraction operation is used to eliminate the background and avoid the light noise. By this method, we can get a resulted image with noting but a clear light spot and it becomes very easy to locate its coordinate. We also design an algorithm suitable for FPGA-based system to locate the coordinate of light spot center. The conventional PC-based light spot locating method records all the coordinates of the spot pixel in the image, then compute the average center to get the coordinate of the light spot. Our algorithm uses the replaced method to save memory and logic elements in the FPGA module. The total used logic elements (LE) of our algorithm are only 16.6% of that of the conventional method. To interact with the computer, we use FPGA to control the USB micro-controller in a commercial USB mouse to make the compute cursor to follow the light spot motion. Besides, we put a diffractive optical element (DOE) in front of the image sensor to blur the background image and transform the light spot into a diffractive circle pattern. This approach can eliminate the subtraction noise caused by the two successive images without similar back-ground images.

參考文獻

[3] J. Barrus and M. Park, “Method and Apparatus for Detecting the Location of a Light Source,” US Patent No.:5,914,783

[4] L. Hauck, “Computer Input System and Method of Using Same,” US Patent No.:5,515,079

[6] C. Kirstein and H. Muller, "Interaction with a projection screen using a camera-tracked laser pointer, “ Proceedings of IEEE Multimedia Modeling, ” pp 191-192, 1998.

[8] B. A. Myers, “A Brief History of Human Computer Interaction Technology”, ACM Interactions, pp. 44-54.

[9] A. Sears, B. Shneiderman, “High Precision Touchscreens: Design Strategies and Comparisons with a Mouse, ” International Journal of Man-Machine Studies, pp. 593-613, 1991.