object lens focal length

基本解释

If the objective lens is closer to the compact disk than the focal length of the object lens then the cylindrical lens creates an elliptical image on the photodetector array.
如果物镜与光盘之间的距离短于物镜的焦距，柱面透镜就会使在光电探测器阵列上的成像变成椭圆影像。
Once you choose a lens whose focal length is closest to the focal length required by your imaging system, you need to adjust the working distance to get object under inspection in focus.
一旦你选择一个镜头其焦距是最接近于你成像系统所需之焦距，你需要调较工作距离去获取观察目标物的焦点。
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