A novel method for diameter measurement of silicon single crystal

Auto diameter measurement plays an important role in Czochralski method for silicon single crystals. In this paper, a novel approach based on concentric ellipses is proposed to measure the diameter of silicon single crystal. First, we analyze the concentric elliptical relationship between the heat shield and the meniscus in a captured image. Then, we further find the diameter of the crystal can be calculated by special geometric properties of concentric ellipses. According to this discovery, our approach is designed to measure the diameter of crystal in two stages. Compared to conventional techniques, our method doesn't apply a complex circle/ellipse fitting algorithm to every image during diameter detection, which makes it suitable for real-time applications. In addition, an ellipse edge filtering algorithm is used to improve the robustness of our system. Experimental results on synthetic images and real images demonstrate that our method is efficient, accurate and robust.