Device for swept-source optical coherence domain reflectometry

• US 8,690,330 B2
• Filed: 12/21/2009
• Issued: 04/08/2014
• Est. Priority Date: 12/23/2008
• Status: Active Grant

• Current Assignee: Carl Zeiss Meditec AG (Carl-Zeiss-Stiftung)
• Original Assignee: Carl Zeiss Meditec AG (Carl-Zeiss-Stiftung)
• Inventors: Hacker, Martin, Ebersbach, Ralf, Pabst, Thomas, Peterlein, Ulf, Antkowiak, Gerard, Bergner, Roland, Koschmieder, Ingo
• Primary Examiner(s): DANG, HUNG XUAN
• Application Number:
  US13/140,752
• Publication Number:
  US 20110255054A1
• Time in Patent Office: 1,569 Days
• Field of Search: 351/205, 351/246, 351/211, 356/497, 356/477, 356/511
• US Class Current: 351/221
• 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: A61B 3/102 for optical coherence tomography [OCT]
• CPC Class Codes: G01B 2290/45 Multiple detectors for detecting interferometer signals
• CPC Class Codes: G01B 9/02004 using frequency scans
• CPC Class Codes: G01B 9/0203 With imaging systems
• CPC Class Codes: G01B 9/02067 by electronic control systems, i.e. using feedback acting on optics or light
• CPC Class Codes: G01B 9/02069 Synchronization of light source or manipulator and detector
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B

Abstract

A device for swept-source optical coherence domain reflectometry (SS OCDR) on moveable samples, particularly human eyes, for obtaining A-scans, having a measuring range according to the sample length and having a laser light source which can be adjusted by a main wave number k₀ and at least one receiver for the light dissipated from the sample, wherein the sample is illuminated on the sample surface by a measurement beam having a diameter D by way of a coupling device. The light source has a spectral line width of δk<168 m⁻¹ and the adjustment of the light source is carried out in τ<44 s/(D*k₀).

Claims

1. A device for swept source optical coherence domain reflectometry (SS OCDR) on a movable sample, for the purpose of obtaining A-scans, comprising:

a tunable laser light source;

at least one receiver for light backscattered from the sample, wherein the sample is illuminated on the sample surface with a measurement beam of diameter D;

wherein the light source has a line width of δ

k<

168 m<sup>−

1</sup>,

wherein the A scan measuring range corresponds to a depth of the sample and

further wherein the device is configured such that tuning of the light source is performed in τ

<

44 sec/(D*k₀) about a centroid wave number k₀.

2. The device for SS OCDR as claimed in claim 1, wherein the sample comprises a human eye.

3. The device for SS OCDR as claimed in claim 2, wherein the measurement beam is convergent before entering the eye.

4. The device for SS OCDR as claimed in claim 3, wherein a degree of the convergence is tuneable or switchable.

5. The device for SS OCDR as claimed in claim 2, wherein the measurement beam is colliminated before entering the eye, and further comprising means for refixation of the eye so that measurement is made on one of an optical axis of the eye and a visual axis of the eye.

6. The device for SS OCDR as claimed in claim 2, wherein the measurement beam is switchable between a colliminated and a convergent measurement beam.

7. The device for SS OCDR as claimed in claim 2, wherein the measurement beam strikes the eye outside a corneal apex.

8. The device for SS OCDR as claimed in claim 7, further comprising an apparatus that controls positioning the measurement beam relative to the eye.

9. The device for SS OCDR as claimed in claim 8, wherein the apparatus that controls the positioning of the measurement beam relative to the eye does so by evaluating the light detected by the receiver.

10. The device for SS OCDR as claimed in claim 2, wherein a photon flux of 3*10⁸ to 3*10¹³ is directed onto the eye during tuning of time τ

of the light source.

11. The device for SS OCDR as claimed in claim 2, wherein measurement is performed along a visual axis of the eye.

12. The device for SS OCDR as claimed in claim 2, wherein detection of light backscattered by a cornea, a crystalline lens and a retina is performed during a tuning of the light source.

13. The device for SS OCDR as claimed in claim 2, wherein reference signals and sample signals are digitized at constant scanning rates.

14. The device for SS OCDR as claimed in claim 13, wherein the constant scanning rates for reference signals and sample signals are the same.

15. The device for SS OCDR as claimed in claim 2, wherein the light source is movable relative to the eye.

16. The device for SS OCDR as claimed in claim 15, further comprising a reference interferometer and wherein the light source and the reference interferometer are rigidly connected.

17. The device for SS OCDR as claimed in claim 16, wherein the reference interferometer has a wave number reference for length calibration of the OCDR signal.

18. The device for SS OCDR as claimed in claim 2, further comprising an interferometer that is movable relative to the eye, the light source and interferometer being rigidly connected.

19. A device for SS OCDR as claimed in claim 2 further comprising means for variation in one of measurement conditions and reconstruction conditions, the variation in one of the measurement conditions and the reconstruction conditions being undertaken so as to attain one of identification and suppression of a mirror artifact signal.

20. The device for SS OCDR as claimed in claim 19, wherein the means for variations in one of measurement conditions and reconstruction conditions comprises a unit for varying a path length difference between the sample arm and reference arm of the interferometer.

21. The device for SS OCDR as claimed in claim 1, wherein the light source has a spectral tuning range Δ

k about a centroid wave number k₀ of at least Δ

k>

18 000 m<sup>−

1</sup>.

22. The device for SS OCDR as claimed in claim 21, wherein the ratio of a tuning range Δ

k and line width δ

k is greater than 360.

23. The device for SS OCDR as claimed in claim 21, wherein a quotient of the tuning rate Δ

k/τ and

laser line width δ

k is greater than 18 kHz.

24. The device for SS OCDR as claimed in claim 21, wherein the backscattered light detected at the receiver is digitized at a rate of more than Δ

k/(τ

*δ

k).

25. The device for SS OCDR as claimed in claim 1, wherein the line width δ

k of the light source lies between 22 and 50 m<sup>−

1</sup>.

26. The device for SS OCDR as claimed in claim 1, wherein the bandwidth of the at least one receiver is greater than 2*Δ

k/(τ

*δ

k).

27. The device for SS OCDR as claimed in claim 26, wherein the bandwidth of the at least one receiver is less than 80 Mhz.

28. The device for SS OCDR as claimed in claim 1, further comprising an interferometer with a reference arm.

29. The device for SS OCDR as claimed in claim 28, wherein the position of retina signals and cornea signals in the A-scan and the laser line width 6k are matched to one another.

30. The device for SS OCDR as claimed in claim 1, wherein the measurement beam diameter D is smaller than 3 mm.

31. The device for SS OCDR as claimed in claim 1, further comprising monomode fibers in at least one of a reference arm, a source arm, a detection arm, and a reference interferometer.

32. The device for SS OCDR as claimed in claim 1, wherein the measurement beam has a wavelength of between 600 and 1150 nm.

33. The device for SS OCDR as claimed in claim 1, further comprising an apparatus for projecting onto the eye aiming markers with a wavelength of between 400 and 900 nm.

34. The device for SS OCDR as claimed in claim 33, further comprising a camera for checking adjustment of the measurement beam relative to the eye.

35. The device for SS OCDR as claimed in claim 34, wherein the camera is sensitive to the wavelengths of the measurement beam and the aiming markers.

37. A method for SS OCDR on the eye, as claimed in claim 3, further comprising deflecting a measurement beam laterally at one of during individual tunings and between the individual tunings.

36. A method for SS OCDR on the eye, comprising:

detecting and evaluating light backscattered by a cornea from individual tunings of a light source with regard in each case to time dependent cornea positions;

comparing the time dependent cornea positions with an expected profile; and

using deviations from the expected profile to correct position data of cornea, crystalline lens and/or retina.

38. A method for SS OCDR on the eye, as claimed in claim 36, further comprising

illuminating the eye with a measurement beam of diameter D from a tunable laser light source;

and

detecting light backscattered by a cornea, a crystalline lens and a retina during a tuning of the tunable laser light source wherein the light source has a line width of δ

k<

168 m<sup>−

1</sup>, and

further wherein tuning of the light source is performed in τ

<

44 sec/(D*k₀) about a centroid wave number k₀.