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Non-distorting video camera for use with a system for controlling growth of a silicon crystal

  • US 5,656,078 A
  • Filed: 11/14/1995
  • Issued: 08/12/1997
  • Est. Priority Date: 11/14/1995
  • Status: Expired due to Term
First Claim
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1. A system for use in combination with an apparatus for growing a silicon crystal from a silicon melt, said system for determining a dimension of the silicon crystal being pulled from the silicon melt, said silicon melt having a substantially planar surface including a meniscus that is visible as a bright area adjacent the silicon crystal, said system comprising:

  • a camera positioned above the silicon melt surface and away from the silicon crystal for generating an image pattern of a portion of the bright area adjacent the silicon crystal, said camera including an image projector for receiving and transmitting light from the bright area adjacent the silicon crystal and an image plane responsive to the light transmitted by the image projector for generating the image pattern of the portion of the bright area adjacent the silicon crystal, said image plane being substantially parallel to the silicon melt surface thereby to compensate for distortion of the image pattern caused by the position of the camera relative to the silicon crystal;

    a detection circuit for detecting a characteristic of the image pattern;

    a defining circuit for defining an edge of the bright area as a function of the detected characteristic and for defining a shape including the defined edge of the bright area; and

    a measurement circuit for determining a dimension of the defined shape whereby the dimension of the silicon crystal is determined as a function of the determined dimension of the defined shape.

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