另一种是在非相干的情况下，由于传播介质的不均匀性，例如空气中存在的颗粒状尘埃物质，还有由于某些原因造成的在物体本身表面上就存在的散斑，例如一片叶子表面上的斑点等等。

Another condition is incoherent, because of the asymmetry in the medium. For example the particle in the air, the defect on the surface of the object, such as the speckle on the leafage etc.

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