如果你不能变更工作距离，你在选择镜头上就免不了规限了。
If you cannot change the working distance, you are somewhat limited in choosing your lens.
设计一套特殊测厚规测量两个环形凸台的距离，这两个环形凸台位于两个同心孔内。
The article designs a special dial thickness gauges that measures the distance between ring-steps in two concentric bores.
镫骨与周围重要结构之间的空间狭小，尤其是与面神经、水平半规管距离小。
There are much more small Spaces between the stapes and the structures especially facial nerve and the lateral semicircular canal around it.
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