A refractive defect of a lens or other optical system that prevents light rays from converging at a single point resulting in a blurred or imperfect image.

散光有折射缺陷的透镜或其它光学系统，阻碍光线汇聚于一个焦点，形成一个模糊或不完全的图象。

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Instead of converging to a point on a focal plane behind the lens, the rays spread out so as to run in a thick stream roughly parallel to each other (see chart).

ECONOMIST: MONITOR