Methods and systems for laser calibration and eye tracker camera alignment

• US 6,666,855 B2
• Filed: 04/23/2002
• Issued: 12/23/2003
• Est. Priority Date: 09/14/1999
• Status: Expired due to Term

• Current Assignee: Amo Manufacturing Usa, Llc (Johnson & Johnson)
• Original Assignee: VISX Incorporated (Johnson & Johnson)
• Inventors: Somani, Seema, Yee, Kingman, Shimmick, John K.
• Primary Examiner(s): Pham, Hoa Q.
• Application Number:
  US10/131,622
• Publication Number:
  US 20020198515A1
• Time in Patent Office: 609 Days
• Field of Search: 356/121, 356/124-127, 356/243.1, 356/243.2, 356/243.3, 250/252.1, 606/4, 606/5, 606/10, 606/12, 606/13, 372/20, 372/32, 372/33, 372/29
• US Class Current: 606/5
• CPC Class Codes: A61B 2017/00725 Calibration or performance testing
• CPC Class Codes: A61F 2009/00846 Eyetracking
• CPC Class Codes: A61F 2009/00855 Calibration of the laser system
• CPC Class Codes: A61F 2009/00872 Cornea
• CPC Class Codes: A61F 2009/00897 Scanning mechanisms or algorithms
• CPC Class Codes: A61F 9/008 using laser
• CPC Class Codes: A61F 9/00802 for photoablation
• CPC Class Codes: A61F 9/00804 Refractive treatments
• CPC Class Codes: A61F 9/00814 Laser features or special beam parameters therefor
• CPC Class Codes: B23K 26/705 Beam measuring device
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01J 1/4257 applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam monitoring arrangements for lasers in general H01S3/0014
• CPC Class Codes: G01J 2001/4261 Scan through beam in order to obtain a cross-sectional profile of the beam
• CPC Class Codes: G01N 21/6456 Spatial resolved fluorescence measurements; Imaging

Abstract

The present invention provides methods, systems, and apparatus for calibrating a laser ablation system, such as an excimer laser system for selectively ablating a cornea of a patient'"'"'s eye. The invention also facilitates alignment of eye tracking cameras that measure a position of the eye during laser eye surgery. A calibration and alignment fixture for a scanning laser beam delivery system having eye tracking cameras may include a structure positionable in a treatment plane. The structure having a feature directing laser energy incident thereon to a calibration energy sensor, at least one reference-edge to determine a characteristic of the laser beam (shape, dimensions, etc.), and an artificial pupil to determine alignment of the eye tracking cameras with the laser system.

Claims

1. A method for calibrating laser energy from a laser eye surgery system, the method comprising:

transmitting a laser beam suitable for ablation of corneal tissue from a surface;

scanning the laser beam across a calibration fixture having a feature;

separating a sample laser energy from the beam at the surface during the scanning;

measuring the sample laser energy during the scanning;

measuring the laser energy transmitted past the feature during the scanning; and

determining a calibration of the laser system by comparing the energy measurements.

2. The method of claim 1, wherein calibration of the laser system is determined by comparing a ratio of the measured sample energy and the measured laser energy transmitted past the feature to a predetermined tolerance.

3. The method of claim 2, wherein calibration of the laser system further comprises independently comparing the measured sample energy to a first threshold range and the measured laser energy transmitted past the feature to a second threshold range if the ratio is within the predetermined tolerance.

4. The method of claim 3, wherein calibration of the laser system is complete if the measured sample energy is within the first threshold range and the measured laser energy transmitted past the feature is within the second threshold range.

5. The method of claim 4, further comprising removing the calibration fixture and ablating a patient'"'"'s cornea with the calibrated system.

6. The method of claim 3, wherein calibration of the laser system indicates a fault in the laser system if the measured sample energy is outside the first threshold range or the measured laser energy transmitted past the feature is outside the second threshold range.

7. The method of claim 2, wherein the laser beam is transmitted from several different positions on the surface, and wherein calibration of the laser system further comprises analyzing each ratio of the measured sample energy and the measured laser energy transmitted past the feature for each position on the surface to determine if the ratio is position independent if the ratio is outside the predetermined tolerance.

8. The method of claim 7, wherein calibration of the laser system indicates a fault in the surface or an energy sensor that measures the sample energy or laser energy transmitted past the feature if the ratio is position dependent.

9. The method of claim 7, wherein calibration of the laser system indicates a fault in an energy sensor that measures the sample energy or laser energy transmitted past the feature or the laser system if the ratio is position independent.

10. The method of claim 1, wherein calibration of the laser system indicates if an energy sensor measures the sample energy or laser energy transmitted past the feature at an accuracy within a predetermined threshold.

11. The method of claim 1, wherein the surface comprises a mirror, and wherein a photodetector measures laser energy leakage through the mirror.

12. The method of claim 1, wherein the feature comprises an opening in the calibration fixture, and wherein a photodetector measures laser light energy passing through the opening.

13. The method of claim 11 or 12, further comprising measuring a variation in each photodetector due to spatial non-uniformity prior to scanning.

14. The method of claim 1, wherein the laser beam is perpendicular to the calibration fixture.

15. The method of claim 1, wherein the feature comprises a first reference-edge, further comprising determining a characteristic of the laser beam by measuring laser energy passing the first reference-edge during scanning.

16. The method of claim 15, wherein the feature comprises a second reference-edge oriented at an angle relative to the first reference-edge, further comprising determining a characteristic of the laser beam by measuring laser energy passing through the second reference-edge during scanning.

17. The method of claim 15, further comprising determining an energy intensity profile of the laser beam from the measured laser energy passing the first reference-edge during scanning.

18. The method of claim 17, further comprising verifying that the intensity profile of the laser beam is within a predetermined acceptable range from the compared energies.

19. The method claim 17, further comprising determining at least one dimension of the laser beam from the laser beam intensity profile.

20. The method of claim 15, further comprising determining a shape of an energy intensity profile of the laser beam by measuring a rate of change of the measured laser energy passing the first reference-edge during scanning.

21. The method of claim 1, further comprising imaging the calibration feature with an image capture device of an eye tracker system so as to measure an alignment of the image capture device with the laser system.

22. A system for calibrating laser energy from a laser beam system comprising:

a scanning laser beam delivery system;

a surface directing laser energy from the laser beam delivery system toward a treatment plane, the surface separating a sample laser energy from the beam;

a first photodetector positioned in a first optical path of the sample laser energy from the surface, the first photodetector emitting a first output signal in response to the sample laser energy;

a calibration fixture positioned near the treatment plane, the fixture having at least one feature;

a second photodetector positioned in a second optical path of the laser beam from the feature of the calibration fixture, the second photodetector emitting a second output signal in response to laser beam incident thereon; and

a processor determining a calibration of the laser system or a characteristic of the laser beam in response to the first and second output signals.

23. A system as in claim 22, wherein the scanning beam delivery system is a laser eye surgery system.

24. A system as in claim 22, wherein the feature comprises an opening in the calibration fixture.

25. A system as in claim 22, wherein the feature comprises a reference-edge.

26. A system as in claim 22, wherein the feature comprises two reference-edges.

27. A system as in claim 22, wherein the feature comprises a cross-like pattern comprising twelve reference-edges.

28. A system as in claim 22, further comprising an image capture device orientated toward the treatment plane and an image processor coupled to the image capture device, the image processor determining a position of the calibration fixture for measuring alignment between the image capture device and the laser delivery system.

29. A system as in claim 28, wherein the feature comprises four dark circles disposed at four corners of a square pattern.