The position of the image and the amplitude variation in the optical field are associated with the focus and the distance from the object to the front focal plane of the lens system.

象的空间位置和光场振幅的变化与透镜系统的焦距以及物体距焦平面的位置有关。

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If, for some reason, some of the convergence points meet in front of, or behind, the focal plane, aspects of the resulting picture will be out of focus.

ECONOMIST: MONITOR