Patent ID: 8349074

Claim:
A method for detecting a diameter of a single crystal at the time of pulling the single crystal from a silicon melt contained in a crucible according to the Czochralski method, the method comprising at least: using two cameras placed in such a manner that the cameras keep the same distance from each other as a target diameter of a straight-body portion of the single crystal and face both ends of the diameter of the single crystal in a growth point of the single crystal respectively, to separately capture both of the ends of the growth point of the single crystal from an outside of a furnace, the growth point being a contact point between the single crystal and a melt surface; and detecting the diameter of the single crystal on the basis of captured images, wherein the diameter of the single crystal is detected by means of detecting each distance in a horizontal direction between one end of the growth point of the single crystal in the respective images captured by the two cameras and a center of the captured images and by summing up the detected distances so that a difference of the diameter of the single crystal with respect to the target diameter of the single crystal is obtained.