circle of least confusion


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circle of least confusion

1 (in optics) a disc representing the image of a theoretical point made by a spherocylindrical lens.
2 smallest cross-section of the blur circle between two focal lines formed by an astigmatic lens.

circle of least confusion 

The smallest cross-section of a circular bundle of an astigmatic pencil formed by an astigmatic lens and situated between the two focal lines. See astigmatism; conoid of Sturm.