Microscopy method, especially for fluorescence correlation spectroscopy

A microscope system, comprising:

• a light source configured to emit excitation radiation along an excitation beam path;
• optical elements including a scanner and an objective configured to direct and focus the excitation radiation at an examination location within a sample positioned on a sample stage:
• a detection beam path including:
• a detector configured to detect radiation emitted by the sample in response to the excitation radiation, and
• a camera or detector configured to capture an overview image or image stack of the sample, including a reference structure;
• a control unit operatively connected to the scanner, the sample stage, the detector, and the camera or detector, the control unit being configured to:
• identify the reference structure in the overview image or image stack;
• define a spatial relationship between the reference structure and the examination location:
• subdivide a measurement sequence into a plurality of measurement intervals;
• before at least every second measurement interval:
• determine whether a deviation exists between a current position of the excitation radiation and the examination location, based on a current position of the reference structure and the stored spatial relationship;
• and
• in response to the deviation exceeding a threshold, realign the excitation radiation with the examination location by controlling the scanner and/or the sample stage to correct for positional drift in three spatial dimensions.