Method for automatic correction of astigmatism

A method for automatic astigmatism correction of a lens system, comprising,

• providing a first image of a first frequency spectrum in a microscope, the first image of a view not being in focus at a first stigmator setting of a lens,
• imaging the first image,
• determining a first roundness measure of a distribution and directions of intensities in the first image,
• changing the lens from the first stigmator setting to a second stigmator setting to provide a second image of a second frequency spectrum, the second image of the view not being in focus at the second stigmator setting of the lens, the second image at the second stigmator setting being of the same view as the first image of the view at the first stigmator setting, determining a second roundness measure of a distribution and directions of intensities in the second image,
• comparing the first roundness measure with the second roundness measure,
• when the first roundness measure indicates a rounder distribution than the second roundness measure, selecting the first image at the first stigmator setting, and
• when the second roundness measure indicates a rounder distribution than the first roundness measure, selecting the second image at the second stigmator setting.