Autofocus method and associated optical imaging system

An optical imaging system (1) for visualizing an object (3) during a medical intervention, the optical imaging system comprising:

• a zoom optics unit (4), which is adjustable by a zoom actuator (5), to adapt an optical zoom level,
• a focus lens (6), which is tunable by a focus actuator (7), to adapt a location of a focal plane (12) along an optical z-axis (8) during a z-scan (17),
• an image sensor (9) for recording image data, and
• a controller (10) for activating the focus actuator (7), wherein the controller (10) is configured to implement an autofocus by activating at least one of i) the focus actuator (7) or ii) the zoom actuator (5) as a function of at least one of:
• a) a zoom level presently set with the zoom actuator (5), wherein the controller (10) adapts a number of the focal planes (12) optically scanned using the z-scan (17) or a spatial scanning frequency of the z-scan (17), or
• b) an estimated value for a present working distance (11) between the imaging system (1) and the object (3), wherein the controller (10) adapts at least one parameter comprising at least one of:
• (i) a length (16) of a scanning range (14),
• (ii) a number of the focal planes (12) optically scanned using the z-scan (17),
• (iii) a spatial scanning frequency of the z-scan (17),
• (iv) an adjustment speed of the focus lens (6), or
• (v) an optical zoom level of the imaging system (1) used during the z-scan (17);
• and
• the controller is further configured to increase the spatial scanning frequency of the z-scan (17) when the length of the scanning range (14) of the z-scan (17) is shortened.