A dioptra () is a classical astronomical and surveying instrument, dating from the 3rd century BCE. The dioptra was a sighting tube or, alternatively, a rod with a sight at both ends, attached to a stand.
网络释义
1、折光仪
... dim 模糊的，暗淡的 dioptra 折光仪，屈光仪 dipvergence (1)双目垂直角差(2)高低发散差 ...