Method for detecting and controlling supply of an immersion medium

A method for detecting and controlling a supply of a liquid immersion medium into an immersion film region disposed between a front lens of a microscope objective of a microscope having an autofocus device and a preparation being examined with the microscope, by using a light source reflected into a microscope beam path of the microscope with a beam splitter, the method comprising recording and evaluating a state of the immersion film region with a detection unit of the microscope or a detection unit of the autofocus device, using an autofocus signal of the light source or a reflection of a modulation object arranged in an intermediate image plane of an incident light illumination source, the method including:

• focusing the microscope without the immersion medium between the front lens and the preparation;
• recording the autofocus signal as back reflection from the autofocus device or recording the reflection of the modulation object arranged in the intermediate image plane of the incident light illumination using one of the detection units;
• supplying immersion medium into the immersion film region;
• recording and detecting an altered intensity of the autofocus signal as back reflection or a change of the optical path length between the front lens and a reflecting boundary of the immersion film region, or recording and detecting the altered intensity or sharpness of the reflection from the modulation object in order to determine a state of the immersion film region:
• communicating the state of the immersion film region to a control unit;
• and
• using the control unit, changing a characteristic of the supply of the immersion medium based on the state of the immersion film region.