Integrated scanning and ocular tomography system and method

• US 7,133,137 B2
• Filed: 06/19/2003
• Issued: 11/07/2006
• Est. Priority Date: 06/27/2002
• Status: Expired due to Fees

• Current Assignee: Amo Manufacturing Usa, Llc (Johnson & Johnson)
• Original Assignee: VISX Incorporated
• Inventors: Shimmick, John K.
• Primary Examiner(s): Lauchman, Layla G.
• Assistant Examiner(s): Lyons, Michael A.
• Application Number:
  US10/601,119
• Publication Number:
  US 20040021874A1
• Time in Patent Office: 1,237 Days
• Field of Search: 356/479, 356/496, 356/497, 356/498, 356/503, 356/504, 356/505
• US Class Current: 356/497
• CPC Class Codes: A61B 2090/061 for measuring dimensions, e.g. length
• CPC Class Codes: A61B 3/1005 for measuring distances inside the eye, e.g. thickness of the cornea A61B3/11 takes precedence
• CPC Class Codes: A61F 2009/00842 Permanent Structural Change [PSC] in index of refraction; Limit between ablation and plasma ignition
• CPC Class Codes: A61F 2009/00851 Optical coherence topography [OCT]
• CPC Class Codes: A61F 2009/00853 Laser thermal keratoplasty or radial keratotomy
• CPC Class Codes: A61F 2009/00872 Cornea
• CPC Class Codes: A61F 2009/0088 based on wavefront
• CPC Class Codes: A61F 2009/00882 based on topography
• CPC Class Codes: A61F 2009/00897 Scanning mechanisms or algorithms
• CPC Class Codes: A61F 9/008 using laser
• CPC Class Codes: A61F 9/00804 Refractive treatments
• CPC Class Codes: A61F 9/00812 Inlays; Onlays; Intraocular lenses [IOL]
• CPC Class Codes: G01B 2290/25 Fabry-Perot in interferometer, e.g. etalon, cavity
• CPC Class Codes: G01B 2290/70 Using polarization in the interferometer
• CPC Class Codes: G01B 9/02002 using two or more frequencies
• CPC Class Codes: G01B 9/02007 Two or more frequencies or sources used for interferometric measurement using only beat G01B9/02003
• CPC Class Codes: G01B 9/02044 Imaging in the frequency domain, e.g. by using a spectrometer
• CPC Class Codes: G01B 9/0209 Low-coherence interferometers
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence

Abstract

Systems and methods of the present invention measure at least one reflecting surface of an object disposed along an optical path. In some embodiments a measured optical interference signal for each of at least three wavelengths of reflected light may be used to determine a modulation of frequency components of a Fourier series. Frequency components of a Fourier series may be transformed to spatial components that describe intensities and positions of light reflected along an optical path.

Systems and methods of the present invention permit rapid measuring and may monitor corneal thickness during surgery. The invention may do so by integrating an ablation device and a measurement apparatus into a single system. An integrated scanning and monitoring system may include an ablative light source producing an ablative beam and a measurement light source producing a measurement beam.

Claims

1. A method of measuiring a thickness of a tissue, the method comprising:

directing a measurement light beam along an optical path toward the tissue;

providing a structure along the optical path;

selecting three wavelengths of corresponding with wavelengths of a Fourier series with the structure;

reflecting the three wavelengths of light from the tissue;

measuring an interference signal for each of the three wavelengths of to reflected light; and

determining a separation distance between positions of at least two reflecting tissue surfaces along to optical path by combining the measured interference signals.

2. The method of claim 1 further comprising:

determining an intensity of the reflected light bean several positions along the optical path combining the measured interferencnignals; and

wherein to measurement light beam comprises the three wavelengths of light simultaneously directed along the path toward the tissue, and wherein the three interference signals are measured simultaneously.

3. The method of claim 1 wherein the Fourier series corresponds to a distance along the optical path and each of the three wavelengths of light undergoes an integer number of oscillations over the distance along the optical path.

4. The method of claim 3 further comprising:

transforming the measured interference signal to spatial position components by taking an inverse Fourier transform using the measured interference signals, the spatial position components describing positions and intensities of the light beam reflected from the tissue along the optical path.

5. The method of claim 1 further comprising determining a tomography of the tissue by directing the measurement beam to several locations of the tissue, the locations having at least two reflecting tissue surfaces along the optical path.

6. The method of claim 5 further comprising:

scanning the light beam from a first location to a second location, wherein the first location and the second location are among the locations used to determine the tomography of the tissue.

7. A method of treating a tissue, the method comprising:

directing an ablative light beam to the tissue to form a desired shape in the tissue;

providing a structure along an optical path;

selecting three wavelengths of light to correspond with wavelengths of a Fourier series with the structure;

reflecting the three wavelengths of light from the tissue by directing a measurement light beam along the optical path toward the tissue;

measuring an interference signal for each of the three wavelengths of the reflected light; and

determining positions of at least two reflecting tissue surfaces along the optical path by combining the measured signals while the ablative light beam is directed toward the tissue.

8. The method of claim 7 further comprising:

determining intensity of the reflected light beam at several position along the optical path; and

wherein the measurement light beam comprises the three wavelengths of light simultaneously directed along the path toward the tissue and wherein the three interference signals are measured simultaneously.

9. The method of claim 7 whrein the Fourier series corresponds to distance along the optical path, and each of the three wavelengths of light undergoes an integer number of oscillations over the distance along the optical path.

10. The method of claim 9 further comprising:

transforming the measured interference siqnals to spatial position components by taking an inverse Fourier transform using the measured interference signals, the spatial position components describing positions and intensities of the light beam reflected from the tissue along the optical path.

11. A system for measuring a thickness of a tissue, the system comprising;

a light source emitting a measurement light beam, the measurement light beam directed along an optical path toward the tissue, three wavelengths of the light beam reflecting from the tissue;

a structure disposed along the optical path, the structure selecting the three wavelengths of light to correspond with wavelengths of a Fourier Series;

an interferometer generating an interference signal for each of the three wavelengths of the measurement light beam reflected from the tissue; and

a processor determining a separation distance between positions of at least two reflecting tissue surfaces along the optical path by combining the measured interference signals.

12. The system of claim 11 wherein:

the processor determines intensity of the reflected light beam several positions alone the optical path;

the measurement light beam comprises the three wavelengths of light simultaneously directed along the path toward the tissue; and

the three interference signals are measured simultaneously.

13. The system of claim 11 wherein the Fourier series corresponds to a distance along the optical path and each of the three wavelengths of light undergoes an integer number of oscillations over the distance.

14. The system of claim 13 wherein the processor transforms the measured interference signals to spatial position components with an inverse Fourier transform using the measured interference signals, the spatial position components describing positions and intensities of the light beam reflected from the tissue along the optical path.

15. The system of claim 14 further comprising an optical system directing the measurement beam to several locations of the tissue so as to determine a tomography of the tissue, the locations having at least two reflecting tissue surfaces along the optical path.

16. The system of claim 15 further comprising:

wherein the optical system scans the light beam from a first location to a second location, and wherein the first location and the second location are among the locations used to determine the tomography of the tissue.

17. A system far treating a tissue, the system comprising:

an ablative fight source emitting an ablative light beam;

a light source emitting a measurement light beam, the measurement light beam directed along an optical path toward the tissue, three wavelengths of the light beam reflecting from the tissue;

a structure disposed along the optical path to select the three wavelengths of light to correspond with wavelengths of a Fourier Series;

an interferometer generating an interference signal for each of the three wavelengths of the measurement light beam reflected from the tissue; and

a processor controlling the ablative light beam and determining positions of at least two reflecting tissue surfaces along the optical path by combining the measured interference signals.

18. The system of claim 17 wherein;

the processor determines an intensity of the reflected light beam at several positions along the optical path;

the measurement light beam comprises the three wavelengths of light simultaneously directed along the path toward the tissue; and

the three interference signals are measured simultaneously.

19. The system of claim 17 wherein:

the Fourler series corresponds to a distance along the optical path and each of the three wavelengths undergoes an integer number of oscillations over the distance; and

the processor transforms the measured inerferrence signals to spatial position components with an inverse Fourier transform using the measured interference signals the spatial position components describing positions and intensities of the light beam reflected from the tissue along the optical path.

20. An apparatus for treating tissue comprising:

a ablative light source producing an ablative beam;

a beam delivery device directing the ablative beam onto a tissue;

a microscope having a viewing port; and

an optical pachymeter emitting a measurement light beam directed along an optical path toward the tissue, three wavelengths of the light beam reflecting from the tissue;

a structure disposed along the optical path to select the three wavelengths of light to correspond with wavelengths of a Fourier series;

an interferometer generating an interference signal for each of the three wavelengths of the measurement light beam reflected from the tissue; and

a processor determining a separation distance between positions of at least two reflecting tissue surfaces along the optical path by combining the measured interference signals.

21. The ablation apparatus of claim 20 wherein:

the processor determines an intensity of the reflected light beam at several positions along the optical path;

the measurement light beam comprises the three wavelengths of light simultaneously directed along the path toward the tissue; and

the three interference signals are measured simultaneously.

22. The ablation apparatus of claim 20 wherein the Fourier series corresponds to a distance along the optical path and each wavelength of light undergoes an integer number of oscillations over the distance, and wherein the processor transforms the measured interference signals to spatial position components with an inverse Fourier transform using the measured interference signals, the spatial position components describing positions and intensities of the light beam reflected from the tissue along the optical path.

23. A method of measuring a separation distance between positions of at least two reflections along an optical path, the method comprising;

reflecting at least three wavelengths of light from the positions by directing a measurement light beam along the optical path;

selecting the three wavelengths of light to correspond with wavelengths of a Fourier series by providing a structure along the optical path, the structure selecting the wavelengths of light;

measuring an interference signal for each of the three wavelengths of the reflected light; and

determining the separation distance between the positions of the at least two reflections along the optical path by combining the measured interference signals.

24. A method of measuring a thickness of a tissue, the method comprising:

reflecting ten wavelengths of light from the tissue by directing a measurement light beem along an optical path toward the tissue;

providing a structure along the optical path;

selectig the ten wavelengths of light to correspond with wavelengths of a Fourier series with the structure;

measuring an interference signal for each of the ten wavelengths of the reflected light; and

determining a separation distance between positions of at least two reflecting tissue surfaces along the optical path by combining the measured interference signals.

25. The method of claim 24 further comprising:

determining an intensity of the reflected light beam at several positions along the optical path by combining the measured interference signals; and

wherein the measurement light beam comprises the ten wavelengths off light simultaneously directed along the path toward the tissue, and wherein the ten interference signals are measured simultaneously.

26. The method of claim 24 wherein the Fourier series corresponds to a distance along the optical path, and each of the ten wavelengths of light undergoes an integer number of oscillations over the distance along the optical path.

27. The method of claIm 26 further comprising:

transforming the measured interference signal to spatial position components by taking an inverse Fourier transform using the measured interference signals, the spatial position components describing positions and intensities of the light beam reflected from the tissue along the optical path.