Free floating patient interface for laser surgery system

1. A system to support a laser eye surgery device, comprising:

a beam source configured to generate a laser beam to perform the laser eye surgery;

an optical scanning assembly including scanning elements configured to scan a focal point of the laser beam in at least two dimensions to different locations within the eye, wherein the optical scanning assembly is coupled to a patient interface device for contacting the eye and includes a microelectromechanical force sensor configured to measure a force on the eye by the patient interface device, the microelectromechanical force sensor being configured to convert an applied force into an electrical signal with a response time of tens of microseconds, the microelectromechanical force sensor being preloaded in a compression state, wherein the optical scanning assembly and the patient interface device are configured to freely follow a movement of the patient's eye relative to the beam source in x, y and z directions so that an optical path between the beam source and the optical scanning assembly is variable;

a sensor to receive a portion of the laser beam which has been reflected from the focal point back along the variable optical path, and generate an intensity signal indicative of the intensity of a portion of the laser beam;

a base assembly;

a mechanical structure for mounting the optical scanning assembly to the base assembly, including:

a horizontal x axis linear bearing configured to support a translation movement of the optical scanning assembly including all its scanning elements relative to the base assembly only in the x axis direction;

a horizontal y axis linear bearing, mounted on the base assembly, configured to support a translation movement of the optical scanning assembly including all its scanning elements relative to the base assembly only in the y axis direction;

a vertical z axis linear bearing, mounted on the base assembly, configured to support a translation movement of the optical scanning assembly including all its scanning elements relative to the base assembly only in the z axis direction;

a vertical z axis spring, configured to counteract the forces of gravity on the optical scanning assembly in the z axis direction;

at least two mirrors of the variable optical path mounted on the mechanical structure and configured to translate relative to each other to reflect the laser beam from the beam source into the optical scanning assembly no matter where the optical scanning assembly is located on the x axis bearing, the y axis bearing and the z axis bearing; and

a plurality of motors, attached to the bearings and configured to actuate movement of the optical scanning assembly in the x, y and z axes relative to the base assembly, the plurality of motors being controlled to move the optical scanning assembly in response to feedback signals from the microelectromechanical force sensor.

2. The system of claim 1 wherein each of the linear bearings is a roller and rail bearing and the vertical z axis spring is a pair of coiled metal tapes each coiled around a spring loaded spool.

3. The system of claim 1 wherein the optical scanning assembly includes a confocal lens assembly.

4. The system of claim 1 , further comprising: a patient support structure, configured to support the base assembly and accommodate relative movement between the base assembly and patient support structure.

5. The system of claim 1 wherein the at least two mirrors include a first mirror supported by the horizontal x axis linear bearing to move in the x axis direction and configured to reflect the laser beam from the x axis direction to the y axis direction, and a second mirror supported by the horizontal y axis linear bearing to move in the y axis direction and configured to received the laser beam from the first mirror and reflect the laser beam from the y axis direction to the z axis direction.