STRAINLESS VIDEO CAMERA USED TOGETHER WITH APPARATUS FOR CONTINUOUS GROWTH OF SILICON CRYSTAL

摘要

System (21) for determining the diameter of a silicon crystal (35) being pulled from a silicon melt (33) for controlling a silicon crystal growing apparatus (23). The melt has a planar surface (87) including a meniscus (85) that is visible as a bright ring adjacent the crystal (35). A camera (53) positioned above the melt surface (87) and away from the crystal (35) includes an image plane (97) that is generally parallel to the melt surface (87) and responsive to light from the bright ring for generating an image pattern of a portion of the bright ring. As such, the camera (53) compensates for distortion of the image pattern caused by the position of the camera (53) relative to the crystal (35). Image processing circuitry detects a characteristic of the image pattern and defines an edge of the bright ring as a function of the detected characteristic. The image processing circuitry further defines a generally circular shape including the defined edge of the bright ring. The diameter of the crystal (35) is then determined based on the diameter of the defined shape for use in controlling the crystal growing apparatus (23).