| 摘要 |
Apparatus for controlling the melt level in a Czochralski crystal pulling method is disclosed. The melt level control has a feedback loop including level sensing means which controls a lift motor for moving the melt containing crucible up or down as called for. The melt level is sensed by alternately transmitting two pulsed beams, or rays, of narrow band visible red light radiation to the melt level surface and measuring the radiation level in the reflected pulse rays after transmission through a lens system. When the melt level is correct the magnitudes of the reflected pulses are equal and no control signal results. When the melt level falls, the magnitudes of the reflected pulses change and a difference signal in one direction is generated causing the crucible to rise. |
