DEVICE FOR MEASURING CRYSTAL DIAMETER

摘要

PURPOSE:To use a fixed photosensor and make it possible to accurately measure a crystal diameter even when the liquid level fluctuates, by providing the photosensor so that a sensing line may once cross a bright ring formed in the interface between a crystal and a melt in producing a single crystal by the Czochralski process. CONSTITUTION:This crystal diameter measuring device is constituted of respective means of the following (a)-(e). That is (a) a photosensor provided so that a sensing line (L) may once cross a bright ring 14 formed between a crystal 10 and a melt 12, (b) a peak position discriminating means for scanning the photosensor and discriminating a picture element position (P) corresponding to the maximum brightness, (c) an average peak position calculating means for calculating the average value (formula 1) of the picture element position (P) over a nearly integer number of revolutions of the crystal, (d) a liquid level detecting means for detecting the liquid level (H) of the melt and (e) a crystal diameter calculating means for calculating the diameter (D) of an interfacial part of the crystal and the melt from the afore-mentioned average value (formula 1) and the liquid level (H) and outputting a signal corresponding to the crystal diameter (D). The photosensor is preferably a one-dimensional image sensor.