Research On On-line Monitoring System Of Silicon Rod Diameter In Polycrystalline Silicon Reduction Furnace

Poly crystalline silicon is the basic raw materials of electronic industry and solar industry, which is widely used in semiconductor chips, high-performance sensors, optical fiber, solar panels and so on. With the rapid development of the production technology and polycrystalline silicon production technology, polycrystalline silicon production in China has accounted for more than70%of global production at present.On-line monitoring of parameters such as the growth rate of silicon rod diameter in the polycrystalline silicon reduction furnace is the key to realize the optimal control. However, because of the lack of equipment which can accurately monitor the growth rate of silicon rod diameter in the process of growth of silicon rods of high purity in polycrystalline silicon reduction furnace, it is unable to realize closed loop control in polycrystalline silicon reduction furnace until now. The open loop control mode is always based on experienced value. It generally causes high energy consumption, low production yield which directly affected the economic efficiency in enterprise and the realization of saving energy and reducing consumption.So far, in the domestic, on-line monitoring system which is used to monitor silicon rod diameter in reduction furnace is through the observation mouth of the furnace wall for artificial visual inspection. Since artificial visual is of great subjectivity, the error of the visual result is very high. This method requires that the workers should have rich experience. And it is necessary that the workers should be close to the furnace wall which may be dangerous to them for the reduction furnace is of high temperature and pressure.This research presents a novel method to solve this problem which employed the near infrared CCD imaging technology. The proposed method is based on digital image processing and computer vision measurement principle with high performance. We have devoted to realizing monitor silicon rod diameter in reduction furnace and successfully developed the on-line monitoring system. The system can replace artificial observation which is able to reduce the labor intensity and the risks of the workers. Furthermore, the system can effectively improve the precision of detection and realize real time monitoring of the growth rate of silicon. The technology provides accurate parameters used in the optimization control in order to better guide the growth of the polycrystalline silicon. The method laid a solid foundation to achieve the automation of advanced closed-loop control technology.This thesis mainly focuses on the following contents:(1)We have corrected the distorted image of silicon rod. The histogram equalization for the quality problem of partial lighter or darker of silicon sod image is realized. We also employed different filtering methods on noise pollution image. Using image preprocessing technologies, such as histogram transform and hough transform, we accurately lock the edge of the silicon sod in silicon sod image.(2)The calibration model is established. Based on the basic principle of binocular vision, specific calibration algorithm is presented.(3)The hardware and software of on-line monitoring system of silicon rod diameter in polycrystalline silicon reduction furnace is designed. And then we analyses the application results.