Surgical optical zoom system

A surgical microscope for capturing a high optical zoom image of a target during a surgical procedure, the surgical microscope comprising:

• an optical assembly including at least one moveable optics;
• an actuator for positioning the moveable optics, the actuator including a pulley system for moving the optics along a set of rails;
• a sensor for detecting the position of the moveable optics;
• a controller for controlling the actuator in response to received control input;
• and
• a camera for capturing the image of the target from the optical assembly;
• wherein the controller is configured to:
• receive control input indicating a target position for the moveable optics;
• control the actuator to position the moveable optics towards the target position, the actuator being controlled according to a first set of control parameters;
• upon receiving signals from the sensor indicating that the moveable optics is within a threshold range of the target position, switch to a second set of control parameters for controlling the actuator;
• and
• control the actuator to maintain the moveable optics at the target position at steady state;
• the first and second sets of control parameters being, respectively, first and second sets of proportional (P), integral (I) and derivative (D) terms for dual-PID control of the actuator.