METHOD AND DEVICE FOR DETERMINING THE OPTIMAL POSITION OF THE FOCAL PLANE FOR EXAMINING A SPECIMEN BY MICROSCOPY

A method for determining the optimal position of the focal plane for examining a specimen by microscopy can include a) illuminating the specimen with light and recording images at different positions of the focal plane to provide a stack of intensity images, b) calculating a phase image from at least two intensity images, with the calculated phase image being assigned a focal plane position located within a focal plane region whose boundaries are the two most spaced apart positions of the focal plane of the at least two intensity images, c) repeating step b) multiple times with different intensity images such that a stack of phase images is available, d) calculating at least one focus measure value for each phase image, and e) determining the optimal position of the focal plane on the basis of the calculated focus measure values and the focal plane positions assigned to the phase images.