螺紋元件為工業上的重要零件，螺紋結構即是在金屬圓柱或圓錐本體表面依螺旋線銑削出螺旋溝槽的外型，主要的功能為固定或結合機械元件，亦可作為傳動等用途。現今螺紋元件的製造以自動化生產為主，為了提高螺紋的加工精度、生產的效率與品質，一套線上快速檢測系統為必要的研究課題。本論文發展出一套三維偏振散射光量測技術之外螺紋測量系統，以光耦合元件搭配偏振鏡來量測外螺紋表面的偏振散射光並加以分析。本系統藉由控制偏振鏡的旋轉角度，分別截取水平與垂直偏振的外螺紋影像，然後由偏振係數方程式結合水平與垂直偏振影像成為偏振係數影像，得到清晰的三維外螺紋影像，藉由此偏振係數影像可以容易的算出螺峰、螺距、螺紋表面特徵等之外螺紋相關參數，並與光學顯微鏡的量測影像比較，以證明本量測系統的正確性。 Screws are arguably the most basic yet essential components used in industry. The helical screw structure seen on the exterior of the screw serves to fasten and hold together various mechanical parts. Today, the production of screws has became a highly automated process. However, in order to increase the precision of screw processing and enhance the productivity and quality of screw production, an online system for rapid testing and measurement is of vital necessity. This study has developed a Goniometric Optical Scattering System (GOSS) for three-dimensional light scattering measurement of the screw surface by using linearly polarized light. A charge couple device (CCD) camera parallel to the surface normal is positioned perpendicularly to the incidence plane. Two images are acquired by rotating the linear polarizer in front of the CCD. One image is acquired by rotating the linear polarizer parallel to the source polarization PP. Another image is acquired by rotating the linear polarizer perpendicular to the source PS. A 2D and 3D polarized image (POL) can be created based on the polarization ratio POL = (PP – PS) / (PP + PS). The POL displays the screw crest, roots and flanks and allows one to estimate screw pitches and grooves. We use the finite-difference time-domain method (FDTD) to simulate light scattering from jagged structures and measuret the optical microscope image in order to prove the correctness of the measurement system.
