High resolution 3-D spectral domain optical imaging apparatus and method
Methods and apparatus are presented for obtaining high-resolution 3-D images of a sample over a range of wavelengths, optionally with polarisation-sensitive detection. In preferred embodiments a spectral domain OCT apparatus is used to sample the complex field of light reflected or scattered from a sample, providing full range imaging. In certain embodiments structured illumination is utilised to provide enhanced lateral resolution. In certain embodiments the resolution or depth of field of images is enhanced by digital refocusing or digital correction of aberrations in the sample. Individual sample volumes are imaged using single shot techniques, and larger volumes can be imaged by stitching together images of adjacent volumes. In preferred embodiments a 2-D lenslet array is used to sample the reflected or scattered light in the Fourier plane or the image plane, with the lenslet array suitably angled with respect to the dispersive axis of a wavelength dispersive element such that the resulting beamlets are dispersed onto unique sets of pixels of a 2-D sensor array.
1. A relative phase-sensitive optical coherence tomography apparatus comprising:
(i) an imaging system for acquiring first and second images of an optical characteristic of a region of a sample in three spatial dimensions, each said image comprising phase and amplitude information over a range of wavelengths and each being acquired in a single exposure of a two-dimensional sensor array, said second image being acquired a predetermined time period after said first image; and
(ii) a processor for:
(a) registering said first image to said second image to determine a spatially resolved shift caused by motion or distortion of said sample in any spatial dimension; and
(b) determining from said spatially resolved shift at least a component of the displacement of said sample associated with said motion or distortion.
2. An apparatus according to claim 1 , wherein said processor is adapted to determine from said spatially resolved shift and said predetermined time period a rate of displacement of said sample associated with said motion or distortion.
3. An apparatus according to claim 1 , wherein said processor is adapted to measure strain associated with said distortion of said sample.
4. An apparatus according to claim 1 , wherein said processor is adapted to perform elastography measurements on said sample.
5. An apparatus according to claim 1 , wherein said apparatus comprises a multi-wavelength light source configured to illuminate said sample with a first pulse for acquiring the first image and with a second pulse for acquiring the second image, and wherein the time period between the first and second pulses is less than the frame rate of said sensor array.
6. An apparatus according to claim 1 , wherein said imaging system is configured to acquire images of an optical characteristic of a region of a sample comprising the retina of an eye.
7. An article of manufacture comprising a non-transitory computer usable medium having a computer readable program code configured to operate the apparatus according to claim 1 .
8. An apparatus according to claim 1 , wherein said motion comprises capillary flow in said sample.
9. A method for performing relative phase-sensitive optical coherence tomography measurements of a sample, said method comprising the steps of:
(i) acquiring first and second images of an optical characteristic of a region of a sample in three spatial dimensions, each said image comprising phase and amplitude information over a range of wavelengths and each being acquired in a single exposure of a two-dimensional sensor array, said second image being acquired a predetermined time period after said first image;
(ii) registering said first image to said second image to determine a spatially resolved shift caused by motion or distortion of said sample in any spatial dimension; and
(iii) determining from said spatially resolved shift at least a component of the displacement of said sample associated with said motion or distortion.
10. A method according to claim 9 , further comprising the step of determining from said spatially resolved shift and said predetermined time period a rate of displacement of said sample associated with said motion or distortion.
11. A method according to claim 9 , further comprising the step of measuring strain associated with said distortion of said sample.
12. A method according to claim 9 , further comprising the step of performing elastography measurements on said sample.
13. A method according to claim 9 , wherein said sample is illuminated with first and second pulses from a multi-wavelength light source for acquiring said first and second images, and wherein the time period between said first and second pulses is less than the frame rate of said sensor array.
14. A method according to claim 9 , wherein said sample comprises the retina of an eye.
15. An article of manufacture comprising a non-transitory computer usable medium having a computer readable program code configured to implement the method according to claim 9 .
16. A method according to claim 9 , wherein said motion comprises capillary flow in said sample.