Aspects of basic OCT engine technologies for high speed optical coherence tomography and light source and other improvements in optical coherence tomography

• US 20030137669A1
• Filed: 08/05/2002
• Published: 07/24/2003
• Est. Priority Date: 08/03/2001
• Status: Active Grant

• Current Assignee: Case Western Reserve University, University Hospitals of Cleveland (University Hospitals Health System Incorporated)
• Original Assignee: Case Western Reserve University, University Hospitals of Cleveland (University Hospitals Health System Incorporated)
• Inventors: Izatt, Joseph A., Yazdanfar, Siavash, Rollins, Andrew M., Westphal, Volker
• Granted Patent: US 7,061,622 B2
• Time in Patent Office: Days
• US Class Current: 356/479
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: G01B 11/2441 using interferometry
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B

Abstract

An optical coherence tomography (OCT) system including an interferometer provides illuminating light along a first optical path to a sample and an optical delay line and collects light from the sample along a second optical path remitted at several scattering angles to a detector. In one embodiment, illuminating light is directed along a number of incident light paths through a focusing lens to a sample. The light paths and focusing lens are related to the sample and to both the incident light source and the detector. In another embodiment, a focusing system directs light to a location in the sample. A transmission grating or acousto-optic modulator directs light from the sample at an angle representative of the wavelength of the incident light on the transmission grating or acousto-optic modulator.

Claims

A. A. A transformation device for an OCT (optical coherence tomography) system in which double sided scanning is carried out, comprising,

plural buffers, one for data obtained during the forward scan by the OCT system and another for data obtained during the reverse scan by the OCT system, and

wherein one of the buffers is first in first out (FIFO) type and a different one of the buffers is first in last out (FILO) type.

B. B. The device of claim A, further comprising a multiplexer to multiplex data into the FIFO and FILO buffers alternately.

C. C. The device of claim B, further comprising a read out to read data from the buffers alternately.

D. D. A method of transforming data from double sided scanning operation of an OCT system, comprising providing the data to respective buffers, one and FIFO buffer and the other an FILO buffer, for coordinated alternate read out toe effect transformation of the data.

A-1. A. An OCT system including an interferometer and an optical delay line, wherein the optical delay line includes a transmissive optically dispersive device.

B-2. B. The system of claim A, said transmissive optically dispersive device comprising a prism.

C-3. C. The system of claim B, wherein the delay line comprises said prism and a double-pass mirror, a lens, and a scanning device.

D-4. D. The system of claim C, wherein the scanning device is a mirror.

E. E. A method for high speed OCT, comprising using a transmissive optically dispersive device in the optical delay line associated with the OCT interferometer.

F. F. The method of claim E, said using a transmissive optically dispersive device comprising using a prism.

A-5. A. An OCT system, comprising an imaging system to obtain information of a sample, and a control to control the imaging system to obtain images at discrete number of depths in the sample,

B-6. B. The system of claim A, wherein the number of depths is two.

C-7. C. The system of claim A, said control comprising a switch to select the length of the delay line scan length of the OCT.

D-8. D. The system of claim C, said switch selects the lateral scan length of the OCT system.

E-9. E. The system of claim A, said control comprises a switch for establishing demodulation settings.

F-10. F. A method of OCT, comprising restricting the scan depth of a sample to a discrete number of depths.

G. G. The method of claim F, said restricting comprising restricting the number of depths to two.

H. H. The method of Claim F, further comprising providing image information display at different sizes.

I. I. The method of claim H, further comprising providing image sizes at a number corresponding to the number of discrete scanned depths.

A-11. A. A method of preserving signal to noise ratio in the case of nonlinear scan rate in operation of an OCT system, comprising generating a local oscillator signal with a frequency that varies as the center frequency of the OCT signal varies, and demodulating the time-varying OCT signal to a fixed intermediate frequency or to DC.

B-12. B. The method of claim A, further comprising filtering the output from the demodulating step with a bandpass filter or a lowpass filter.

C-13. C. A method of preserving signal to noise ratio in the case of nonlinear scan rate in operation of an OCT system, comprising using a phase locked loop to generate a signal with a frequency that varies as the center frequency of the OCT signal varies, and demodulating the time-varying OCT signal to a fixed intermediate frequency or to DC.

A-14. A. An OCT system, including an interferometer, and characterized in that the interferometer has an optical path to bring light to a sample and a separate optical path from the sample to a detector.

B-15. B. The system of claim A, further comprising an optical fiber bringing light to the sample, and a separate optical fiber bringing light from the sample to the detector.

C-16. C. The system of claim B, said detector comprising a differential detector.

D-17. D. The system of claim A, further comprising optics in both light paths, and wherein the optics are shared.

E-18. E. The system of claim D, said optics comprising a shared lens.

F-19. F. The system of claim D, said optics comprising an array of microlenses.

G-20. G. The system of claim A, wherein the sample is a reflective or scattering sample.

H-21. H. The system of claim A, further comprising an optical delay line.

J. J. The system of claim A, wherein two separate optical paths bring light from the sample to respective detectors.

K. K. The system of claim J, wherein a common optical delay line provides light to both detectors.

L. L. The system of claim K, wherein one beamsplitter divides light from a light source and directs the light to the delay line and directs light to the optical path to bring light to the sample;

and a second beamsplitter divides light from the delay line to both detectors.

M. M. The system of claim L, further comprising respective beamsplitters merging light from the delay line with light from respective separate optical paths bringing light from the sample to respective detectors.

N. N. The system of claim N, each of said detectors comprising a differential detector.

O. O. A method of approximating an optical circulator in an OCT system including an interferometer, comprising directing light via a first optical path to a sample, and directing light from the sample via a second optical path to a detector, and detecting light from the sample and from an optical delay line.

P. P. The method of claim O, wherein the two optical paths are next to each other.

Q. Q. The method of claim P, comprising using optical fibers to direct light in both optical paths, and using common optics between the optical fibers and the sample to direct light to the sample and to receive light from the sample.

R. R. The method of claim O, said directing light from the sample comprising directing light from the sample in two different separate optical paths to respective detectors.

S. S. The method of claim R, further comprising directing light to an optical delay line, and said directing light from the sample in two different separate optical paths comprising merging the light from the optical delay line with respective light in the two different separate optical paths prior to detection.

A-22. A. A device for simultaneously collecting light from a sample remitted at several scattering angles, comprising, a reflector having a surface positioned relative to the sample to receive light scattered from a location of the sample at different respective scattering angles, a collection lens for collecting such scattered light and directing it to the reflector.

B-23. B. The device of claim A, said reflector comprising a right angle reflector having a one reflecting surface for reflecting light scattered by the sample, and a second surface for directing incident light to the sample.

C-24. C. The device of claim B, said incident light being provided by a fiber optic member and a collimating lens, and said scattered light reflected by the reflector being directed via respective lenses into respective collection fibers.

A-25. A. A device for simultaneously illuminating and collecting light from a sample remitted at several scattering angles, comprising, a fiber optic member for illuminating the sample, and a group of fiber optic members arranged relative to the illuminating fiber optic member to collect light scatted at respective scattering angles by the sample.

B-26. B. The device of claim A, wherein the fiber optic members are arranged in a bundle.

A-27. A. An interferometer, comprising

a low coherence source,

1a beamsplitter for directing light from the source to a sample and to a reference optical delay line,

a scanning system to scan a sample with the incident light from the source,

a detector system for detecting light scattered by the sample at multiple angles.

B-28. B. The interferometer of claim A, further comprising Doppler processing means for processing signals resulting from detection of light from the sample at at least two angles and from the reference optical delay line.

C-29. C. The interferometer of claim A, further comprising a camera for aligning the incident light with respect to the sample.

D-30. D. The interferometer of claim A, wherein the detector system includes two optical paths to receive light scattered at respective angles from the sample, the two optical paths and the relationship of the scattering angles remaining substantially constant.

A-31. A. A device for simultaneously illuminating and collecting light from a sample remitted at several scattering angles, comprising,

a number of incident light paths,

a focusing lens for directing light from such light paths to a common spot of a sample,

wherein the light path and focusing lens being related to the sample and to both incident light source and detector for directing light remitted at several angles from the sample to the detector along at least part of the incident light paths.

B-32. B. The device of claim A, further comprising a microlens array for collimating light from the respective incident light paths and directing such collimated light toward the focusing lens, and for directing scattered light received from the sample by the focusing lens to the respective incident light paths.

C-33. C. The device of claim A, further comprising a focusing member and a beam former for collimating light from the respective incident light paths and directing such collimated light along respective paths toward the focusing lens, and for directing scattered light received from the sample by the focusing lens to the respective incident light paths.

D-34. D. The device of claim C, said focusing member comprising a lens.

E-35. E. The device of claim A, further comprising a lens for collimating light from the respective incident light paths and directing such collimated light toward the focusing lens, and for directing scattered light received from the sample by the focusing lens to the respective incident light paths.

A-36. A. A system for illuminating a sample and for receiving light from the sample for analysis, comprising,

a focusing system for directing light to a location in the sample,

a light path for scattered light from the sample,

a transmission grating for directing light from the sample at an angle representative of the wavelength of the incident light on the transmission grating.

B-37. B. The system of claim A, said focusing system and transmission grating cooperating to collect a portion of scattered light into a single spatial mode out of the grating, with each wavelength component having been scattered at a different angle.

C-38. C. The system of claim A, further comprising an interferometer with a scanning reference arm for measuring light from the sample via the focusing system, light path and transmission grating.

D-39. D. The system of claim A, wherein the focusing system comprises a lens for focusing light to the sample and for focusing light scattered by the sample and a number of angles to the transmission grating.

E-40. E. The system of claim A, wherein the focusing system comprises a telescope, including a lens for focusing light to the sample and said lens and a further lense for focusing light scattered by the sample and a number of angles to the transmission grating.

E-41. E. The system of claim A, wherein the transmission grating comprises an acousto-optic modulator.

F-42. F. A method of measuring angle resolved scattering of light from a sample, comprising

directing light via a focusing member to illuminate at least a part of a sample,

directing light from the sample scattered by the sample at several scattering angles via the focusing member to a variable dispersion device, and

operating the variable dispersion device to direct light therefrom at respective angles according to the angle of the scattering from the sample.

G-43. G. The method of claim F, said operating the variable dispersion device comprises operating an acousto-optic beam deflector.

H-44. H. The method of claim G, wherein said directing light through a focusing member to the sample comprises directing light through an edge portion or side portion of a lens.

I-45. I. The method of claim G, said directing of light via a focusing member comprising directing light to the sample through a lens, and further comprising directing light scattered by the sample through said lens and through a further lens, whereby the further lens collects light and directs the collected light to the acousto-optic beam deflector.

A-46. A. An interferometer system, comprising

at least two light sources,

a combiner for combining light from the two light sources, sample and optical delay line light paths,

a detector for detecting light from both the sample and delay line light paths.

B-47. B. The system of claim A, said combiner comprising a beamsplitter.

C-48. C. The system of claim A, comprising a further combiner for combining light from the sample and optical delay line light paths.

D-49. D. The system of claim C, further comprising a detector for detecting light from the further combiner.

E-50. E. The system of claim D, said combiner and further combine comprising respective beamsplitters.

F-51. F. A method of OCT analysis of a sample, comprising

directing light from two sources to a sample and to a reference,

combining light from the sample and reference, and

measuring such combined light.

G-52. G. The method of claim F, said directing light to a reference comprising directing light to an optical delay line.