METHOD FOR MEASURING MELT LEVEL AT GROWING CRYSTALS Russian patent published in 2006 - IPC C30B15/26 

FIELD: crystal growing, possibly in apparatuses for measuring melt level at enlarged range of angular velocity of its rotation.

SUBSTANCE: method comprises steps of forming probing light beam; directing it by inclination angle relative to melt surface to probing point with use of optical system arranged in path of light beam reflected from melt surface; forming image of light spot from probing point in plane of photo detector; according to position of said spot, detecting melt level; then forming other probing light beams; directing them to probing point by different angles relative to incident plane of first light beam; selecting inclination angles of light beams in such a way that each light beam reflected from melt surface may enter aperture of optical system only in predetermined (corresponding to said beam) range of angular velocity values of melt rotation; alternatively using light beams; selecting from electric signals of photo detector corresponding to light beam only those signals that satisfy to predetermined parameters; calculating repetition frequency of selected signals for each light beam; selecting measuring light beam for which repetition frequency of selected signals exceeds threshold value; for measuring light beam determining position of light spot in image; according to received data calculating melt level; if repetition frequency of selected signal is less than threshold value, selecting new measuring light beam by analysis of signals corresponding to other light beams and selecting such measuring light beam for which repetition frequency of selected signals exceeds that for previous measuring light beam by predetermined value.

EFFECT: enlarged range of melt rotation angular velocities in which it is possible to perform measurements, elimination of error of melt level measurement caused by mutual interference of probing light beams.

2 dwg