Patent ID: 6226032
Filing Date: 2001-05-01
Classification: C30B

Abstract:
A system controlling the diameter of a monocrystalline rod being pulled from molten material held in a crucible, the system using at least one video camera arranged to view a meniscus around the rod where the rod emerges from a melt surface of the molten material so that an image of the meniscus is incident on a camera pixel array, and the system comprising:a. a lens system arranged to provide a close in view of a neck growth region of the rod and to provide a wide angle view of a body growth region of the rod so that the image of the meniscus on a pixel array is relatively enlarged during neck growth and is relatively reduced during full diameter growth;b. a computer arranged for calculating and controlling crystal diameter from the meniscus image during both neck growth and full diameter growth;c. the computer being supplied with a count of total camera pixels illuminated by the image of the meniscus during neck growth; andd. the computer responding rapidly to the total pixel count for varying a rod pulling rate during neck growth.