Calibrating laser beam position and shape using an image capture device

Abstract

The present invention provides improved methods and systems for laser beam positioning, shape profile, size profile, drift, and/or deflection calibration using an image capture device, such as a microscope camera, for enhanced calibration accuracy and precision. The methods and systems are particularly suited for iris calibration and hysteresis measurement of a variable diameter aperture. One method for calibrating laser pulses from a laser eye surgery system using an image capture device comprises imaging a known object with an image capture device. A pulsed laser beam is directed onto a calibration surface so as to leave a mark on the calibration surface. The mark on the calibration surface is then imaged with the image capture device. The laser eye surgery system is calibrated by comparing the image of the mark on the calibration surface to the image of the known object.

What is claimed is: 
     
         1 . A system for calibrating laser pulses from a laser eye surgery system, the system for altering an eye while the eye is disposed at a treatment plane, the system comprising:
 an image capture device orientated toward the treatment plane so as to image the eye while the eye is altered by the system;   a known object positionable for imaging by the image capture device;   a pulsed laser beam delivery system oriented for directing a pulsed laser beam toward the treatment plane;   a calibration surface supportable in an optical path of the pulsed laser beam so as to result in a mark on the calibration surface and for imaging of the mark on the calibration surface by the image capture device; and   a processor coupled to the image capture device, the processor determining a calibration of the laser beam delivery system by comparing the image of the mark on the calibration surface to the image of the known object.   
     
     
         2 . The system of  claim 1 , wherein the laser beam delievery system includes a variable aperture setting to adjust the laser beam diameter over time to leave a plurality of marks of variable diameters on the calibration surface so that, when the marks are imaged and the imaged marks on the claibration surface are compared to the image of the known object, a hysteresis of the variable aperture is determined. 
     
     
         3 . The system of  claim 1 , wherein a relationship between a diameter of the laser beam and a motor count associated with an iris setting of the laser eye surgery system is determined when the imaged object size is compared with the imaged size. 
     
     
         4 . The system of  claim 1 , wherein the image capture device comprises a microscope camera having multiple illumination settings. 
     
     
         5 . The system of  claim 1 , wherein the imaged object comprises a circular shape having a known diameter. 
     
     
         6 . The system of  claim 1 , wherein the known object comprises a circular chrome layer of known diameter on a glass plate. 
     
     
         7 . The system of  claim 1 , wherein the known object and calibration surface are imaged in the same position. 
     
     
         8 . The system of  claim 1 , wherein the known object and calibration surface are positioned in at least one of a laser focus plane or the treatment plane. 
     
     
         9 . The system of  claim 1 , wherein the calibration surface comprises photosensitive material, silkscreen material, luminescent material, photoreactive material, polymethylmethacrylate material, or photographic material. 
     
     
         10 . The system of  claim 6 , wherein the mark on the calibration surface comprises an ablation, a permanent change in color, or a luminescent glow. 
     
     
         11 . The system of  claim 1 , wherein the mark on the calibration surface has an iris setting in a range from about 0.65 mm to about 6.7 mm. 
     
     
         12 . A method for calibrating laser pulses from a laser eye surgery system, the laser eye surgery system having an image capture device oriented for altering an eye while the eye is disposed on a treatment plane and imaging an eye during laser eye surgery of the eye, the method comprising:
 imaging a known object with the image capture device of the laser eye surgery system, the imaged object having an imaged object size, an imaged object shape, and an imaged object location;   directing a pulsed laser beam of the laser eye surgery system onto a calibration surface so as to leave a mark on the calibration surface;   imaging the mark on the calibration surface with the image capture device of the laser eye surgery system, the imaged mark having an imaged mark size, an imaged mark shape, and an imaged mark location;   comparing the image of the mark on the calibration surface to the image of the known object; and   calibrating a laser beam cross-sectional shape, a laser beam cross-sectional location, and/or a laser beam cross-sectional size of the laser eye surgery system based on comparing the image of the mark to the image of the known object.   
     
     
         13 . The method of  claim 12 , wherein the imaged object comprises a circular shape having a known diameter. 
     
     
         14 . The method of  claim 12 , wherein the known object comprises a circular chrome layer on a glass plate. 
     
     
         15 . The method of  claim 12 , further comprising removing the known object prior to directing the pulsed laser beam onto the calibration surface. 
     
     
         16 . The method of  claim 12 , wherein the imaging of the known object and of the mark on the calibration surface is carried out in the same position. 
     
     
         17 . The method of  claim 12 , wherein the directing and imaging are carried out in the same plane. 
     
     
         18 . The method of  claim 12 , wherein the mark on the calibration surface comprises an ablation. 
     
     
         19 . The method of  claim 12 , further comprising increasing the pulsed laser beam diameter setting over time so as to form a plurality of marks, imaging the marks, and comparing the marks to the known object. 
     
     
         20 . The method of  claim 12 , further comprising decreasing the pulsed laser beam diameter setting over time.