Methods and apparatus for imaging with multimode optical fibers

Patent metadata

Field	Value
Publication number	US-9871948-B2
Application number	US-201314389275-A
Country	US
Kind code	B2
Filing date	Mar 28, 2013
Priority date	Mar 29, 2012
Publication date	Jan 16, 2018
Grant date	Jan 16, 2018

Abstract

A multimode waveguide illuminator and imager relies on a wave front shaping system that acts to compensate for modal scrambling and light dispersion by the multimode waveguide. A first step consists of calibrating the multimode wave guide and a second step consists in projecting a specific pattern on the wave guide proximal end in order to produce the desire light pattern at its distal end. The illumination pattern can be scanned or changed dynamically only by chang ing the phase pattern projected at the proximal end of the waveguide. The third and last step consists in collecting the optical information, generated by the sample, through the same waveguide in order to form an image. Known free space microscopy technique can be adapted to endoscopy with multimode waveguide, such as, but not limited to, fluorescence imaging or Raman spectros copy or imaging, 3D linear scattering imaging or two-photon imaging. Super-resolution, i.e., resolution below the diffraction limit, is achieved for example but not limited to, using the STimulated Emission Depletion microscopy (STED) technique or the Structured Illumination Microscopy (SIM) technique or a stochastic illumination based method (PALM, STORM) in combination with the multimode waveguide imaging method.

First claim

The invention claimed is:

1. A method for deterministic light transmission through a multimode waveguide comprising the steps of:
providing the multimode waveguide;
calibrating the multimode waveguide, the calibrating including,
coupling in light at a proximal side of the multimode waveguide; and
analyzing light at a distal side of the multimode waveguide by capturing one or more off-axis calibration interferogram images with a two-dimensional detector, and

conditioning the distal side of the multimode waveguide by controlling a spatial light modulator at the proximal side with a conditioning pattern computed from the off-axis calibration interferogram images at the proximal side of the multimode waveguide to generate a counter-propagated beam.

2. The method of claim 1 , wherein the distal side of the multimode waveguide is an opposite end of the multimode waveguide to the proximal side or a same side as the proximal side.

3. The method of claim 1 , wherein the step of calibrating is realized through transmission matrix measurement.

4. The method of claim 1 , further comprising
adjusting a focal spot at the distal side of the multimode waveguide by digitally controlling the spatial light modulator in the conditioning step,
directing the focal spot exiting the distal side of the multimode waveguide to a sample, and
illuminating the sample by scanning the focal spot on the sample.

5. The method of claim 4 , further comprising
collecting light arriving from the sample as a result of illuminating, at the distal side of the multimode waveguide,
sampling the collected light for determined scanning positions, whereby each determined scanning position represents a pixel, and
constructing an image of the sample pixel by pixel, the pixels corresponding to the collected light at each determined scanning position.

6. The method of claim 5 , further comprising achieving super-resolution by exciting the sample with a first wavelength and depleting with a second wavelength with a determined ring pattern.

7. The method of claim 4 , further comprising steps of
placing a scattering medium at the distal side of the multimode waveguide to decrease the size of the focal spot on the sample;
choosing a size of the focal spot at the distal side of the multimode waveguide; and
choosing a position of the focal spot at the distal side of the multimode waveguide.

8. The method of claim 1 , further comprising steps of:
directing light to a sample;
analyzing scrambled light collected through the multimode waveguide from a sample to recover an image;
analyzing light collected from the sample to extract axial information; and
constructing an image of the sample in three dimensions, the axial dimension corresponding to different depths in the sample.

9. The method of claim 8 , further comprising achieving super-resolution by projecting determined spatial patterns computed from the off-axis calibration interferogram images at the step of conditioning the waveguide.

10. The method of claim 8 , further comprising achieving super-resolution by stochastically illuminating the sample when directing light from the distal side of the waveguide.

11. The method of claim 1 , further comprising steps of
providing light pulses at the step of coupling in light; and
providing short light pulses at the distal side of the multimode waveguide by applying an appropriate light field at the step of conditioning the waveguide when controlling the spatial light modulator.

12. The method of claim 11 , further comprising steps of
determining a wavelength required for excitation of the sample; and
choosing a wavelength twice the wavelength required for excitation of the sample for the light at the step of providing light pulses.

13. The method of claim 1 , wherein the multimode waveguide is a rigid waveguide, the method further comprising
positioning the distal side of the multimode waveguide on a surface of a sample.

14. The method of claim 1 , wherein the multimode waveguide is a flexible waveguide, the method further comprising
inserting the multimode waveguide in a sample and moving the multimode waveguide while adapting the conditioning pattern on the spatial light modulator in the step of conditioning the distal side.

15. The method of claim 1 , further comprising
calibrating the multimode waveguide from the proximal side to create calibrated light at the proximal side.

16. The method of claim 15 , further comprising:
providing a beacon means whereby the step of coupling comprises coupling light from the beacon means.

17. The method of claim 1 , further comprising
controlling the polarization of light at the distal side of the multimode waveguide;
analyzing light coupled in at the proximal side of the waveguide, at the distal side for all the polarizations; and
conditioning the distal side of the multimode waveguide for all the polarizations.

18. The method of claim 1 , further comprising
transmitting high speed digital information.

19. The method of claim 1 , wherein the multimode waveguide is an optical waveguide that presents modal scrambling and high dispersion, wherein the multimode waveguide is at least one item in the following list:
a step-index fiber,
a graded index fiber,
a double-clad fiber,
a large mode area fiber,
a fiber bundle,
a no-core fiber, and
a rod.

20. The method of claim 1 , wherein the step of conditioning the output further includes:
processing the off-axis calibration interferogram image to retrieve phases of the counter-propagated output beam at the distal side of the multimode waveguide.

21. A system for deterministic light transmission through a multimode waveguide, the system comprising:
the multimode waveguide,
calibrating means configured for calibrating the multimode waveguide,
the calibrating means comprising,
light coupling means for coupling light at an input side of the multimode waveguide,
analyzing means arranged for analyzing light at an output side of the multimode waveguide,

the analyzing means comprising,
a digital analyzing system that digitally analyzes a complex light field in its phase or amplitude properties by capturing one or more off-axis calibration interferogram images with a two-dimensional detector, and

conditioning means configured to condition an output of the multimode waveguide,
the conditioning means comprising,
a spatial light modulator configured to project a light field computed from the off-axis calibration interferogram images at the input side of the multimode waveguide.

22. The system of claim 21 , wherein the multimode waveguide is an optical waveguide that presents modal scrambling and high dispersion, wherein the multimode waveguide is at least one item in the following list:
a step-index fiber,
a graded index fiber,
a double-clad fiber,
a large mode area fiber,
a fiber bundle,
a no-core fiber, and
a rod.

23. The system of claim 21 , wherein the spatial light modulator is at least one item of the following list:
a phase liquid crystal spatial light modulator,
a deformable mirror,
a binary amplitude modulator, and
an analog amplitude modulator.

24. The system of claim 21 , wherein the output side of the multimode waveguide is either
an opposite end of the waveguide to the input side, or
the same side as the input side.

25. The system of claim 21 , wherein the digital analyzing system

Assignees

• Ecole Polytechnique Fed De Lausanne (Epfl)
• Ecole Polytechnique Fed Lausanne Epfl

Inventors

• Papadopoulos Ioannis
• Farahi Salma
• Moser Christophe
• Psaltis Demetri

Classifications

• G03H1/0005

  Adaptation of holography to specific applications (holographic optical element G02B5/32; holographic scanner G02B26/106; recognition using holographic mask G06V10/88; holographic memories G11B7/0065, G11C13/042) · CPC title

• G02F1/011

  in optical waveguides, not otherwise provided for in this subclass · CPC title

• G03H1/2286

  Particular reconstruction light (G03H1/24 takes precedence); Beam properties · CPC title

• G02F1/0136

  for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation (G02F1/0353 takes precedence) · CPC title

• G02B23/26 Primary

  using light guides {(for illumination G02B23/2469)} · CPC title