Free floating patient interface for laser surgery system

A method for performing a laser eye surgery on a patient's eye, comprising:

• directing a laser beam generated by a laser beam source from a base assembly along a variable optical path into an optical scanning assembly;
• coupling the optical scanning assembly to the eye via a patient interface device;
• by a microelectromechanical force sensor, measuring a force on the eye by the patient interface device and converting the measured force into an electrical signal with a response time of tens of microseconds, the microelectromechanical force sensor being preloaded in a compression state;
• by the optical scanning assembly, scanning a focal point of the laser beam in at least two dimensions to different locations within the eye;
• receiving a portion of the laser beam which has been reflected from the focal point back along the variable optical path, with a sensor and generating an intensity signal indicative of the intensity of the portion of the laser beam;
• wherein the variable optical path has at least two mirrors configured to translate relative to each other, wherein the optical scanning assembly is mounted to the base assembly via:
• a horizontal x axis linear bearing, configured to support a translation movement of the optical scanning assembly in an x axis direction;
• a horizontal y axis linear bearing, configured to support a translation movement of the optical scanning assembly in a y axis direction;
• a vertical z axis linear bearing, configured to support a translation movement of the optical scanning assembly in a z axis direction;
• and
• a vertical z axis spring, configured to counteract the forces of gravity on the optical scanning assembly in the vertical z axis, and
• by a plurality of motors attached to the bearings, and based on the electrical signal from the microelectromechanical force sensor, actuating movements of the optical scanning assembly in the x, y and z axis directions relative to the base assembly;
• and
• freely following a movement of the patient's eye relative to the base assembly in the x, y and z directions along the variable optical path with the optical scanning assembly and the patient interface device.