专利名称：LEVELLING INSTRUMENT发明人：HUMPHREY D,US申请号：US3793735D申请日：19720510公开号：US3793735A公开日：19740226
摘要：A levelling instrument wherein a level condition is indicated by the projection ofa light beam within the instrument on an indicator. The light beam is projected in aconstant vertical direction by a reflecting surface that is rotatable about a light source,which is focused on the indicator only when the instrument is level. The reflecting surfacecan comprise a pendulum mirror or a continuous circular conduit partially filled withmercury.
申请人：HUMPHREY D,US
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